Side by side fuel injectors in open manifold.
Side by side fuel injectors in open manifold.
(OP)
I have a fuel injection conversion project in mind, using either a Megasquirt or Canems programmable control system.
My old non-crossflow, 850cc four pot engine presently has a single semi-downdraught SU type carburettor. The carb is fitted on a heated swan-neck adapter which takes the mixture flow into the mouth of the main inlet manifold. The ports are arranged E-II-EE-II-E. The conventional cast ally inlet manifold has two horiziontal branches, feeding the two pairs of side-by-side inlet ports.
The main problem with this engine is its very small size and lack of space around the inlet ports and in the engine bay. It's a very tight fit in there, too small for any conventional throttle bodies, including motorcycle types, which are all crossflow. To keep the conversion simple, I'm therefore looking at the possibilty of fitting a single throttle body downdraught fashion, onto a vertical adapter bolted on the existing gas flowed and matched inlet manifold (i.e. replacing the heated swan neck adapter). This would allow me to fit two injectors into each of the manifold's two branches, one for each inlet port.
These would be fitted by welding in comercially available, push-in tubular injector adapters on the top face of the two manifold branches.
The inlet manifold branches have no internal walls and therefore act as plenums. This works very well on the carb setup. The injectors will be fitted side by side, at a 45 degree angle on the manifold, to fire directly towards the ports, only about 25-30 mm away from the face of the head casting.
I see no issue with this but I'd just like to canvass opinion here before I make an expensive mistake and ruin my specially made ally inlet manifold because I've missed something obvious.
Thanks in advance!
My old non-crossflow, 850cc four pot engine presently has a single semi-downdraught SU type carburettor. The carb is fitted on a heated swan-neck adapter which takes the mixture flow into the mouth of the main inlet manifold. The ports are arranged E-II-EE-II-E. The conventional cast ally inlet manifold has two horiziontal branches, feeding the two pairs of side-by-side inlet ports.
The main problem with this engine is its very small size and lack of space around the inlet ports and in the engine bay. It's a very tight fit in there, too small for any conventional throttle bodies, including motorcycle types, which are all crossflow. To keep the conversion simple, I'm therefore looking at the possibilty of fitting a single throttle body downdraught fashion, onto a vertical adapter bolted on the existing gas flowed and matched inlet manifold (i.e. replacing the heated swan neck adapter). This would allow me to fit two injectors into each of the manifold's two branches, one for each inlet port.
These would be fitted by welding in comercially available, push-in tubular injector adapters on the top face of the two manifold branches.
The inlet manifold branches have no internal walls and therefore act as plenums. This works very well on the carb setup. The injectors will be fitted side by side, at a 45 degree angle on the manifold, to fire directly towards the ports, only about 25-30 mm away from the face of the head casting.
I see no issue with this but I'd just like to canvass opinion here before I make an expensive mistake and ruin my specially made ally inlet manifold because I've missed something obvious.
Thanks in advance!





RE: Side by side fuel injectors in open manifold.
- Siamesed inlets
- Simaesed exhausts on 2 & 3
- 850 cc
Bill
RE: Side by side fuel injectors in open manifold.
The 2 injectors would likely work fine, but why not just install a single injector and fire it twice, instead of installing 2 and alternating their operation?
RE: Side by side fuel injectors in open manifold.
Firing order for a 4-banger is either 1-3-4-2 or 1-2-4-3. In either case, that intake runner is seeing two intake strokes in a row followed by a full revolution of nothing.
Unless you do something rather unorthodox with the injection timing - and I'm not saying that's impossible - I'm thinking that whichever of those pair of cylinders is first in the firing order is going to be rich and the second one is going to be lean.
The original carb setup doesn't have this issue because all four cylinder pulses are taken away after the carb so that the flow through the carb is as constant as possible (or at least, as consistent for each cylinder as possible). Siamesed ports in which the valve timing overlaps are always going to have some interference between the two.
If you can fix it so that the injector fires coinciding with the early part of the intake stroke on each injector, you might get away with it. Each injector would see hit-hit-miss-miss with the other injector doing the opposite. The two hits in a row might not necessarily want the same duration. The duty cycle of the injectors would have to be kept low for this to work. No idea if the software you're proposing would allow this strategy.
RE: Side by side fuel injectors in open manifold.
The proposal is for four injectors, two in each branch, or arm, of the manifold, i.e. one for each cylinder. There is no need for anything other than a conventional firing pattern, 1-3-4-2.
On other 4 cylinder setups I'm familiar with, the inlet ports have individual tubes leading to the port. The original inlet Reliant manifold is like this, albeit with cylinders 1-2 and 3-4 siamesed within the casting "branches". Unfortunately the inlet tubes are small in diameter and we've proved that more power is produced if the dividing wall is removed.
My manifold is an alternative cast ally design with a single oval interior common to both inlet ports. It's also extended to sit further away from the head as it was originally designed for a supercharger setup with a 4 branch tubular exhaust to fit beneath. It's big enough to house two injectors side by side in each branch. Hence my query.
RE: Side by side fuel injectors in open manifold.
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RE: Side by side fuel injectors in open manifold.
Thankyou for your comments. I intend to arrange the fuel spray to go as directly into the port as possible, within the limitations of the physical space available. I know that many modern inlet manifolds house the nose of the injector in a small "archway" above each inlet branch directly at the port, which has a matching cutaway to help channel the spray. Unfortunately there is no room to do this on my manifold so the spray will go into the main airflow from above.
"Charge robbing" is one of my concerns. I think this will affect emissions rather than power. However, I'm sure that the injection conversion will improve the emissions of the SU setup. This has been an issue at annual MOT test (it's well known in Reliant circles) because there is no effective way of properly calibrating the mixture needle at idle.
Regards, Paul W
RE: Side by side fuel injectors in open manifold.
If so, I think you need to be very careful as charge robbing is likely to be an issue. As you probably know, charge robbing does cause problems when injecting the A series (true siamese ports).
How to get around it?
- Position the injector as close to the head as possible, use narrow spray angle injectors and point them right at the back of the valves. Might be enough.
- Use a manifold that has at least some segregation. You can easily make a manifold from thinwall tubular steel (exhaust tube) and it works just fine. FWIW, I suspect you'll get better torque from a manifold with separate runners anyway. Maybe just not practical in the available space.
- Use either a single point injector for all 4 cylinder or a pair of them each to serve 2 cylinders.
Use sequential injection so you can time the shots (at low rpm at least where it will matter more). There are now versions of Megasquirt that can do sequential injection albeit at greater expense (still pretty reasonable) and complexity. Here's someone who's done it already
h
Don't know much about Canems but a little googling found this
http://www.canems.co.uk/siameseports.php
You might find this interesting too.
http://www.starchak.ca/efi/efi.htm
Hope you find this useful
Regards
Nick
RE: Side by side fuel injectors in open manifold.
You are correct. The original design of the Reliant manifold has four narrow tubes/runners, two in each branch. This manifold is very small in diameter. It was discovered that more power was to be had if the "dividing wall" was milled away, leaving a single "hourglass" section tube now shared by both ports. This solved an uneven mixture problem on a particular Weber downdraught carb (34 ICH).
I now use a similar but improved design of manifold where the internal cross section is one large oval. The division in flow occurs only at the port face. My engine can no longer use the original manifold due to the inlet ports being enlarged sufficiently to cause a sealing problem at the head face. I use spacer blocks with an internal "hour glass" port on extended studs to get the new manifold on. Without them there is no room to get a spanner or socket in between the exhaust headers to tighten the nuts. Some of the fasteners are socket headed screws going directly into the head casting but not all are accessible with a hexagon wrench and a spanner has to be used.
To put the diminutive size of this engine in perspective, the head is only 13.5" in length (the car is only 10 feet long, think Austin 7 special). I cannot go back to a manifold with separate runners without downsizing the inlet runners again, so I would be as well to go back to the old restrictive manifold! But I cannot get injectors fitted to that because there is no space for them.
My reason for keeping the existing manifold is because of further space restrictions in the engine bay alongside the engine.
RE: Side by side fuel injectors in open manifold.
not2fast
RE: Side by side fuel injectors in open manifold.
Regards
Nick
RE: Side by side fuel injectors in open manifold.
Nick, I'm OK with electronics provided the instructions are OK and having briefly looked through the downloadable manuals, Megasquirt seems pretty good in that respect.
Having taken the engine out of the car today, I've been looking at the manifolding issue again. It would be possible to weld in a simple "mixture containment plate" (my term) in the centre of each manifold spacer block. This might alleviate charge robbing to all intents and purposes.
The other way, as already suggested, is to convert to closed loop single point injection using the existing manifold. It might even be possible to convert the existing carb body; I know this has been done with Stromberg carbs.
My concern with that would be the duty cycle of the single injector.
RE: Side by side fuel injectors in open manifold.
RE: Side by side fuel injectors in open manifold.
As I said earlier, one per cylinder = four injectors, which would be fitted as close to the intake ports as space permits.
A single injector fitted at the engine end of the intake manifold would actually rely on charge robbing to work, not a good idea.
Alternatively, one injector fitted close to, or in, the single throttle body. Two injectors at that location would halve the duty cycle, which might work better.
RE: Side by side fuel injectors in open manifold.
Examples that spring readily to mind are found on the Ford Ka (and probably older Fiestas which use that same venerable pushrod engine) and some of the smaller engined Vauxhalls from the 90s. Also some of the smaller engined Fiats. I expect there are many others too. These will be plenty big enough for your needs, maybe too big. I'm assuming you're UK based as the Reliant 850 can't be common elsewhere.
Charge robbing considerations aside, I'd prefer the multipoint, 4 injector solution.
Nick
RE: Side by side fuel injectors in open manifold.
RE: Side by side fuel injectors in open manifold.
The throttle body will feed a simple plenum adapter fitted to the existing inlet manifold. I made a mockup of a simple plenum adapter (a simple truncated cone/frustum and bespoke end plates). There is room in this to fit two injectors side by side to halve the duty cycle (this requires a very simple, compact fuel rail). Megasquirt uses two injector ouputs so wiring should be very simple in this respect.
The actual adapter can be made from fabricated ally plate or may be done in CNC'd billet alloy, depending on how flush I'm feeling when the relative costs are finalised.
I've decided to retain the heated section swan-neck adapter as this will help in obtaining a very homogenous mixture.
Thanks for your ideas.
RE: Side by side fuel injectors in open manifold.
MS
RE: Side by side fuel injectors in open manifold.
Performance
Economy
or Emission friendly
You can only really have one without spending and thinking a fair bit.
The heated swan neck adaptor really only functions after startup, and until running temp is reached.
You'll find that the intake will conduct from head anyway - enough to re introduce fuel dropout back into intake air should the need arise. Fuel dropout is only a problem if the injector is far from ports, if its cold, and if your cranking speed is low.
Unless your intake is remote water fed, ie with hoses, from hoses, Id bin that bit because if its not hose fed, then its fed from a passage in the head - watch out if gasket starts failing under closed throttle. Give it extra choke/start enrichment on the tables if your having fuel dropout. I have always found manifold heaters of any kind, from electric hedgehogs, to water, to be a pain as things start to age.
Unless your trying to save the worlds emission problems, Id batch fire all four injectors, or however many at once. When the intake valve is closed, and piston is coming up to expel exhaust, the injector will again fire into tract, or near hot intake valve back. This will promote fuel evap further and will also allow you to run injectors at lower duty cycle % as each fire is 1/2 quantity that cylinder needs for combustion, this will make idle setup easier. But still, overall cc in tiny in comparison. Look into bikes/scooters for suitable injectors that you may score for free.
To be really honest, I wouldn't think too much about it. Ive seen some shocking intake(x4 injectors) or single injector setups that work very well, surprisingly. They drove fine too. Dunno about emissions or economy though, they were all test drives.
Remember a single carb works fine on an inline 6, with prehistoric runner design...
Answer the 'what is your goal' bit first, then Ill think some more!
Brian,
RE: Side by side fuel injectors in open manifold.
Brian,
RE: Side by side fuel injectors in open manifold.
MS
RE: Side by side fuel injectors in open manifold.
The little Reliant 850 ccengine was designed about fifty years ago and has run on a carb for the ten years since I built this trials car. It was originally designed to power a 3 wheeled car. Three wheelers don't get emissions tested in UK. As soon as this one was fitted into my 4 wheeler, it was required to comply with the emission limits for the year of registration.
It usually fails the emissions test at MOT test time. The SU carb is traditionally very poor for emissions at idle, where the UK testing is done. Reliant owners usually tweak the mixture weak at idle prior to the test, which weans that the car won't run above idle. Before driving the car home they tweak it back to normal again. My friendly tester has another way of getting round that, enough said.
However, I want to improve things in that respect as well as bringing things into this century.
The car is used on road and also for off-road hill climb/trials competitions, so power is an issue, especially as we compete against cars with much bigger engines (3.5 litre in some cases). That said, I have one fairly recent class award where we beat all the MGs at an MG Car Club Trial and the only thing that beat us was a car in the "unlimited" Class 8.
We've tinkered with three different carbs and each has had its strengths and weaknesses. Extreme nose up attitudes at full power in first gear and subsequent hot starting after heat soak have always been an issue. FI should solve that in addition to the emissions issue whilst giving good power output.
The heated swan neck has a direct coolant hose supply, btw. Using it allows the throttle linkage mechanism to gain clearance from the inlet and exhaust manifolds, which is another issue on this little non-crossflow engine.
RE: Side by side fuel injectors in open manifold.
Are you allowed or have you altered valve and valve seat geometries?
The crux with many old engines is chamber shape, valve grinds, valve seat wall thickness(many are thicker than they need to be narrowing port) and of course large tolerances on all hydrodynamic bearings.
But of course then, your down to materials...and what will give next.
Perhaps your intake and carb should be further down the list?
What have you done already?
One last point, many think carbs are junk(nowadays), maybe so for various adjustments they need every now and then, but when setup correctly, they will and have surprised some efi whizzes...
I once saw two cars on rollers, each putting out around 135 standard. They had been modified, one ran efi, the other webbers, the efi fell short 5hp at 175hp. The web put down 180. Ill never forget the look on your mans face, he just could not understand how a flathead screwdriver could beat a laptop(Both in correct and incorrect hands of course)
Brian,
RE: Side by side fuel injectors in open manifold.
Regards
Pat
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RE: Side by side fuel injectors in open manifold.
Engine mods are free from regulation but I reckon I've done just about all the mechanical mods that can be done. I achieved 58-60 bhp on a Weber 34 ICH (rolling road figures). I've since gone away from that carb and fitted a 1.5"/38mm SU (standard is 1.25"/32mm) because the engine would often cut out on a steep slope restart and then refuse to start. We're allowed 6 seconds to clear the line after the marshall's flag drops then are deemed to have failed the hill. The engine was often fluffing up badly and stopping with the Weber fitted, due to the extreme angle of the float chamber causing very rich mixture (i.e the contents of the float chamber tended to dump into the in the manifold). If we can't restart the engine and clear the line, as well as failing the section, we often have to reverse back down, which can be very exciting (!) and holds up the whole event because there is no other escape route.
My car is one of 60 made. It's seen by the designer as probably the most powerful normally aspirated one in its type/class using this type of engine. During one trial I was approached by a very enthusiastic marshall who asked to see my supercharger setup because he was building an Austin 7 special and wanted to copy it. He was completely taken aback when I told him that it didn't have one. I don't think he believed me until I lifted the bonnet and let him see for himself.
Other owners have not been as successful in tuning their Reliant 850s and some have recently fitted Suzuki G10A engines (relatively modern 1 litre, 3 cylinder, fuel injected). I don't want to go down that route as it involves a major rebuild and chassis and bodywork mods. There is also an advantage in keeping with the smaller engine - in the event of a dead heat during a special test timed sections, the smaller engine wins by default.
The non-crossflow head uses parallel vertical valves and there is no scope for changing this. The head has been ported as far as it can be safely done and chambered. Due to other work on the block and wet liners the CR is very high (it pumps straight up to 225 psi on a dynamic compression test) and I have no deire to increase this. In fact I've done some recent work to remove material to decrease the CR and this time will fit a head gasket of 0.0715" thickness (standard is .047", in an effort to improve reliability in that area. The crank assembly has been dynamically balanced. On these engines the factory conrods are known to be good to 9,000 rpm and flat top pistons give no trouble either, so nothing needs doing there.
I am about to fit a slightly hotter 280 degree cam; this is as yet untried but is expected to increase top end power and willingness to rev a little higher (present cam completely runs out of go at 6000 rpm). As part of this upgrade I initially intended to merely fit Megajolt ignition to replace the original camshaft/chain drive distributor (already converted to electronics and advance curve modified) but I want to be able to experiment with mapping the ignition because I've always felt there has been more to come from this engine. Having looked at the relative cost of using a Megasquirt module to also include fuel injection, I'm looking at giving it a go.
To give you some idea of what we get up to, here's a YouTube link of our little car:
ht
RE: Side by side fuel injectors in open manifold.
Do they prevent a log plenum with IR from the plenum and a single throttle body. I have made inlet manifolds out of copper pipe and plumbing fittings before today and exhaust pipe tube can also be used. I know aluminium looks the part, but it actually only needs to direct and control airflow.
Regards
Pat
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RE: Side by side fuel injectors in open manifold.
I think I see what you are getting at - then fit one injector per runner. There's nothing to prevent me doing that. In effect that's what the original manifold was, albeit with a downdraught entry mouth.
We did find better performance with the internal wall of the manifold cut away. The inlet ports are so close together in the head casting it prevents enlargement of the runners of the original manifold by more than a couple of millimetres without breaking through the dividing wall so I couldn't match the size of the enlarged inlet ports. I reckon the narrow tubes had become the limiting factors to gas flow to the port. Allowing the ports to "suck from both teats" as it were, removed that limit. I understand that ideally the runners should be as long as possible. On this car using long runners blocks access to the battery (which sits alongside the engine) and accessory drive belt adjustment. I had originally used twin SUs on separate, semi-downdraught siamesed inlet trumpets, giving a longer inlet tract. Car ran very well (and they looked very nice indeed) but they were totally impractical for other than occasional use. My car also gets used on the road, we've covered almost 40K miles since I put her together a decade ago.
Alternatively, as I think I mentioned earlier, I could possibly fit simple ally plates inside each arm of my present "big bore" cast manifold, to provide crude fuel spray guides which should minimise fuel charge robbing, if in fact that should prove to be a problem (which is where my original quest began ;) ).
All interesting ideas. Thanks again. Paul W.
RE: Side by side fuel injectors in open manifold.
The valve grind/overlap would affect this reading and no indication of cr.
But I feel you know this.
Ill think some more,
Brian,
RE: Side by side fuel injectors in open manifold.
Yes, I'm aware of the lack of accuracy of that method. However I also know that a standard engine of this type (10.5 to 1 CR) normally gives around 195 psi. The cam in my engine is standard but the head face has been skimmed and the block shaved when I first had it re-manufactured (I wish they hadn't done this, especially as the pistons now sit very slightly proud of the liners at TDC, but that's another story altogether).
So we do know it's a little bit higher than 10.5 to 1.
I've not had time to re-measure the volumes of the combustion spaces as yet. These are "bathtub" shaped with a "waist" on one side (not sure of the technical term but they look like a rounded capital letter "B". This time I've taken some more metal out; de-shrouded the valves slightly and removed a little off the "egg-timer waist" between the valves. I will re-calculate the actual CR with the new thick gasket eventually. I'm hoping to have reduced it back down to a more sensible level.
RE: Side by side fuel injectors in open manifold.
Bill
RE: Side by side fuel injectors in open manifold.
My car's cylinder head:
[IMG]http://i7.
RE: Side by side fuel injectors in open manifold.
As Pat mentioned, ITBs may be the way to go too? But of course they have drawbacks compared to log style manifolds.
'Generally' ITBs lose mid range torque, but offer gain at higher rpm. Dont go down the road of large or common diameters, fit smaller bore ones, this will keep some mid torque by keeping air speeds up. 7/10 times I see throttles fitted with too large a bore.
Obviously, if you do go this route, and aim to make power further up the range than you currently make it, keep in mind your gearbox ratios may need a re-jig to take full advantage.
Easy and cheap steps are, make car light, and fit the smallest width(within reason), and diameter rims that will fit over your brakes.
Overall, you will be limited with what you can do with a cast Iron head, since al transfers heat faster, and therefore can handle higher crs without hotspots. Al heads were one of the notable changes when It came to getting more power out of top ends - Is head Al or Iron?
Brian,
RE: Side by side fuel injectors in open manifold.
The existing gearbox ratios can't easily be changed because nothing else fits - the gearbox is very small on these cars. I have recently fitted a longer diff ratio to reduce the engine rpm for road use as it produces quite a bit more torque than the norm. One member of our group did obtain a quote for a new gear cluster but it apparently was to cost almost as much as he had spent on his entire car. I'm happy with the gearbox ratios!
Regarding weight reduction - for the road yes, we have a car weighing 460 kgs but in fact we tend to ballast them up at the rear end for more off-road traction during competition work. I hang my two spare wheels off the rear of the car and carry a heavy tool bag, another tool box, a spares box and jacks, spare fuel, water ballast etc in the rear compartment.
If you look at this video link below you should get some idea of what we try to emulate (Sorry to say, I can't easily do the "old school" accent though). It's all for fun, no prize money given, no sponsorship allowed, so costs are a big issue.
http://www.youtube.com/watch?v=8YLmb08T0z4
Rgds, PW.
RE: Side by side fuel injectors in open manifold.
h
is very instructive, since so often the specific features that Weslake had recognized as key to the enhanced performance of his chamber are misunderstood or even removed during a head job. I am thinking of aspects such as the swirl-inducing inlet port (counter rotating in adjacent cylinders when fed by siamesed intake ports), and the curved chamber side walls to deflect the incoming mixture around the head of the valve.
PJGD
RE: Side by side fuel injectors in open manifold.
An interesting link! I seem to have inadvertently copied the intricacy of that design by de-shrouding the inlet valves during previous DIY work on my ally cylinder head. It made a noticeable difference, more than I'd expected for the small amount of metal removed.
Regards, Paul W.
RE: Side by side fuel injectors in open manifold.
Bill
RE: Side by side fuel injectors in open manifold.
My initial concern was charge robbing when using four injectors in the existing "Siamesed runner" manifold. I spent some time pondering over this, then saw the answer was to design and make a couple of ally plates to weld inside the engine end of the manifold, to direct the fuel sprays directly into the port they were meant for. Essentially, place a simple dividing wall between ports.
Having finally got this sorted, I trial fitted the manifold. The injectors will actually be required to sit less than an inch from the exhaust headers. Not a good recipe for longevity of plastic bodied injectors, even with heat shielding fitted.
The single injector spaced away from the exhaust in a simgle throttle body may be more practical, if not the best design for performance. In effect an electronically controlled carburettor working in closed loop.
RE: Side by side fuel injectors in open manifold.
If you now have paired runner divides ported out totally, then I would buy another manifold and leave them in there. Mount an injector in each tract spraying onto valve, or near it, and batch fire them. Individual runners to each valve will airspeed up.
Brian,
RE: Side by side fuel injectors in open manifold.
RE: Side by side fuel injectors in open manifold.
Mike Halloran
Pembroke Pines, FL, USA
RE: Side by side fuel injectors in open manifold.
[IMG]htt
And the original (which was found to be restricting overall airflow):
[IMG]http://i7.
RE: Side by side fuel injectors in open manifold.
Those manifolds have 21mm diameter runners, too restrictive for my engine (the runners are much smaller in diameter than the ports in the head so we stopped using that type some years ago). It would actually be very difficult to fit injectors, as they would all have to face in different directions. A fuel rail would be very difficult to align.
Also, the 4 branch exhaust now fitted to my car means that manifold can no longer fit my engine because the length of the side branches is too short to reach the head. The original cast iron Reliant exhaust manifold is very small too and of very poor design. It went in the bin a decade ago and there is absolutely no prospect of me fitting that so I can also fit a more restrictive inlet, too.
This is the main reason I wanted to use the existing inlet manifold, which is wider across the side branches, so the two pairs of injectors can sit alongside and be parallel to each other.
I'm now going back to the idea of a larger, single injector in a single 38mm diameter Jenvey throttle body, retaining all the existing manifoldery. Effectively this would just replace the existing carb. Having downloaded drawings of the Jenvey item, I've now got as far as designing an adapter plate so it will fit straight on to the heated swan neck. The plate will also locate the outer throttle cable.
I'll forgo the long individual inlet runners for what should be excellent fuel /air mixing, i.e. same set up as with the existing carburettor. It will also make a very simple, uncluttered, installation and look pretty good good under the bonnet.
RE: Side by side fuel injectors in open manifold.
Brian,
RE: Side by side fuel injectors in open manifold.
RE: Side by side fuel injectors in open manifold.
RE: Side by side fuel injectors in open manifold.
Thanks, and no I've never seen a GM TBI in UK. I've now looked these up online and it seems the smallest unit made was for 2.8 to 3.1 litre engines, is this correct? My engine is just 850 cc and therefore I think one of the GM units will be unsuitably large, in respect of intake gas speed and low throttle opening controllability, which is often important for a trials car (we need to carefully control the engine power output to avoid wheelspin, especially on section starts/restarts).
However, I have considered other smaller single point injectors available here, from the previous generation of smaller cars (Fiat, Ford, Suzuki etc). I don't know if they are tunable and from experience I know the Ford ones are unreliable with age.
Thanks again to all, this is a really interesting topic for me (even if for no-one else).
RE: Side by side fuel injectors in open manifold.
Regards
Pat
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RE: Side by side fuel injectors in open manifold.
I've just bitten the bullet and bought a set of three throttle bodies from a '99 Triumph Speed Triple 955i, a cheap Ebay deal at just over £50 delivered, injectors, fuel rail, TPS, linkage all included. I reckon about a sixth of the cost of a new Jenvey setup?
This bike uses three completely independent 42mm throttle bodies with injectors, linked together by simple pressed steel rails, so they can be very easily dismantled. These are unlike most other bike setups I've considered, which seem to be made to operate as a unit.
The "master" one houses both the throttle linkage and the TPS, so I intend to use just that one on the original manifold system and see how I go with it.
I'll need to modify the fuel rail, but this looks easy enough as it's billet alloy with a screwed plug in each end. I can shorten it then re-drill and tap the "new" end to close it off, using the original plug. I think I may need a slightly larger flow injector but that will need further research before final setup is done.
A long way to go yet but I'm looking forward to the challenge of making this work.
I'll report back at some stage. Thanks again for all contributions here; just realised how many there have been.
RE: Side by side fuel injectors in open manifold.
'The main problem with this engine is its very small size and lack of space around the inlet ports and in the engine bay. It's a very tight fit in there, too small for any conventional throttle bodies, including motorcycle types, which are all crossflow'
Where theres a will theres a way I guess...;
B,
RE: Side by side fuel injectors in open manifold.
What I meant was that that type of setup can't be done on this small, non-crossflow engine (I don't know of any non-crossflow, fuel injected motorcycles).
The proposed setup is to use a single motorcycle throttle body on the existing carb manifold and heated swan neck adapter, which keeps the TB well away from the cylinder head and the heat of the exhaust manifold. The single throttle body will replace the existing SU type carburettor.
RE: Side by side fuel injectors in open manifold.
Ive designed and cast a lot of custom manifolds for different setups, Its amazing what you can fit in a space if its tailor made. See how the single tb fairs I guess, It sounds a pretty simple, and cost free swap should it not show gains so go for it,what have you to loose!
Brian,
RE: Side by side fuel injectors in open manifold.
If this doesn't work out I'm considering an engine swap for the only other engine that will easily fit in our tiny car's engine bay.
This is the Suzuki G10A, coupled to a Suzuki Jeep 5 speed gearbox (this little front wheel drive engine rather surprisingly bolts straight on to the 4wd jeep gearbox). This conversion is now being supported by the designer of the car, Peter Davis, who has come out of apparent semi-retirement (at least as production of car kits is concerned), to help owners who have struggled to get the Reliant engine to perform sufficiently well.
I've just realised an unintended bonus of buying the Triumph triple throttle body setup: The Suzuki G10A is a relatively modern, three cylinder, crossflow ported, 1 litre engine. It uses a single point injector in standard form and produces just 52 bhp. The Triumph triple bike setup might well bolt on to it very easily and release quite a bit more output.
RE: Side by side fuel injectors in open manifold.
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RE: Side by side fuel injectors in open manifold.
I'm not committed to using the Triumph injector, it may actually not be big enough in flow capacity, so a change might be required in any case.
When you said "we made the injectors", may I respectfully ask who "we" is?
Thanks, Paul.
RE: Side by side fuel injectors in open manifold.
It's not just droplet size. Cone angle and targeting are all wrong for single point application. You can change the injector but you can't fix the targeting. I still think you would have fewer problems with individual port injectors.
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RE: Side by side fuel injectors in open manifold.
Thanks for the advice, much appreciated and I can understand what you are saying. However, I can't fit single port injectors for practical reasons already explained. In an ideal world I would do so, that was my original idea put forward here.
The inlet tract on my setup is 13 inches from injector output face to the ports, all of it heated. The Triumph injector will actually fire directly at the hottest part of the heated swan neck (toward the outside wall of the upper downward bend where the coolant input joins it, i.e. the "back of the swan's throat"), which will hopefully provide sufficient fuel vapourisation.
The SU carb worked well for many thousands of these little engines, using the (same) swan neck on a similar manifold but with an inner dividing wall to give as long a runner as would fit in the engine bay. This made the flow division occur less than half that distance from the ports. One engine tuner found a "glitch" (quite severe charge robbing) when the heated swan-necked plenum was removed to fit a Weber downdraught carb for his racing series (Rebel Racers). Two cylinders (one in each pair) ran weak. Removing the inner wall in the manifold cured the problem.
I used this setup for some time but found another, hot starting problem instead. I've gone back to the SU type carb on a purpose built, wider bore manifold. The plugs run very evenly coloured using this setup so it appears the swan neck is heated for good reason.
I've been in touch with Jenvey, who make high quality throttle bodies. They make single point throttle bodies not dissimlar to the Triumph type. I was going to fit one until I found the Triumph setup at far lower cost.
Jenvey said they thought a single point setup should work well. Obviously, the proof of the pudding is in the eating! This is experimental stuff after all. If the single point injection doesn't work out, I can always think again. I regard the main bulk of the project to be in fitting the electronics and associated other stuff, sensors etc to make it all work. Both Megasquirt/Microsquirt or Canems can control either application.
If this project gets completed, I'll post the results here, either good or bad. ;)
RE: Side by side fuel injectors in open manifold.
You could also mount butterfly's in the oem manifold after the injectors and before port/head face. Much like the Toyotas variable intake butterfly's near valves.
Surely this is possible and you could even use parts from the V.runner Toyota manifold?
I feel when you gutted the divides out of the ports, it was possibly better fuel/air mix you were getting, and not more air. The total twin port/runner cross section now seems insane for such a small engine.
Brian,
RE: Side by side fuel injectors in open manifold.
Brian,
RE: Side by side fuel injectors in open manifold.
The problem with space/size is two fold. Again, I'd like to emphasise that this is a tiny 850cc, non-crossflow engine. The total head face is just 13" long, shorter than the head width on my Honda CB750. There are eight ports on the same side. The Reliant OE manifold is only 8.75" long and about three and a half inches from front to back. Each of the two mounting flanges, where it bolts to the head, containing two inlet runners, is just over two inches wide. The original fit for both the Reliant (and the Liege) has a single 1.25" SU carb sitting above the rocker cover (I mean right above it).
The standard inlet ports are only 21mm wide. I've done extensive research and no-one makes a small capacity four cylinder motorcycle with ideally small individual throttle bodies - at least not for the UK market. I bought a set of four TBs from a modern (small by UK standards) 650 Kawasaki for a look see; the TB unit is larger than the cylinder head itself and the outlets are 42mm in diameter, twice that of the inlet ports.
Apart from very limited physical space on the engine itself, the engine bay is very narrow. Fitting stuff alongside the engine means I can't access the battery, which sits alongside the engine, or the alternator drive belt adjustment. I had twin SUs on the car to begin with but it proved totally impractical and I had to remove them. It was almost half a day's work to check and top up the battery level or to adjust the fanbelt tension.
Obviously, anything is possible if enough money is thrown at it. Unfortunately I cannot justify production of a new, one-off manifold casting.
Regards, Paul.
RE: Side by side fuel injectors in open manifold.
If you are to swap over to efi, and want to see gains, then I dont think there is much point in doing so unless you get serious about the manifold.
Generally, well In my eyes, power would come first, adjusting ancillary(s) would be far down the list.
Look into tig welding something new of you cant afford casting. Where theres a will, theres a way.
Brian,
RE: Side by side fuel injectors in open manifold.
EFI as such will not improve power much at all over a carby set up. To get gains you need to increase airflow, improve airflow distribution and improve fuel distribution. Charge robbing does not only rob fuel, it also robs air.
If the battery is in the way, move the battery. That is not exactly a major problem.
If the exhaust is n the way, reroute it to make more room.
If the engine bay is narrow, make a manifold with individual runners that sweep back over the engine so the plenum is on the opposite side to the exhaust. Use one large throttle body on the plenum and four individual injection nozzles. Make the inlet manifold out of exhaust tubing for reasons of economy. It isn't really all that hard to do.
Alternatively, cut holes in the side of the engine bay so long as there will be some room for the manifold to project through. I mean, this is supposed to be a race car.
Regards
Pat
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RE: Side by side fuel injectors in open manifold.
But yes Paul, thats pretty much it really,
Brian,
RE: Side by side fuel injectors in open manifold.
Sorry guys, we're obviously talking at crossed purposes here. This is definitely not a race car and power is certainly not the only priority. If I wanted to build a race car, I'd have built a different car altogether. As I mentioned, this is essentially a 1950s style road car. For fun we use it for off-road trials.
All I'm trying to do here is replace the existing carb setup with an EFI, without changing the car into something else it was never designed to be. We're certainly not trying to win the NASCAR series with it. The "more power" priority was posted by someone else. I'd hoped I'd made things clear enough by posting the link to the video of us using the car in a trial. As you perhaps hadn't watched it, here is another:
http://www.youtube.com/watch?v=77RRLlYXZ7U
We got second in class that day. The following year (2010) we won best in class, which surprised the MG drivers as it was an MG Car Club invite and we beat them all. We were second overall, to a Buckler, built especially for trials and it arrived and went home on a trailer. We drive to and from the trials.
Anyhow, I thank you all for your contributions. I think we'd be better to leave the subject to rest here because I sense this thread is beginning to cause frustration in some.
As I said, I will report back with observations when the car is back on the road.
RE: Side by side fuel injectors in open manifold.
It worked well enough for those relatively low-revving, low output engines. Roughly 90hp from a 1.8l. The turbo variants did get divided intake ports and four port injectors.
RE: Side by side fuel injectors in open manifold.
With this in mind I've also been in touch with a fuel injector specialist who advises that a single 400cc injector (a long stroke, 20 degree spray Asnu) should do the trick and will cope well with mapping.
RE: Side by side fuel injectors in open manifold.
Brian
RE: Side by side fuel injectors in open manifold.
Regards
Pat
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RE: Side by side fuel injectors in open manifold.
I've had practical problems, especially during off road trials with different carbs, which the TBI should overcome. Some of the slopes we are expected to drive up are extremely steep (too steep to walk up or down). This can cause either fuel starvation or flooding depending which carb is used and in which orientation it's fitted; we think due to float chamber limitations. Other owners have the same problem.
The car also has to pass UK emissions testing during its annual MOT check for road use. As I wrote in one of my original posts, the car has always had a problem with the emissions test (the Reliants all do, due to limitations of the SU carb they were originally fitted with at idle). In the past we have had to get around this by various means. We have to find a "Reliant friendly" MOT tester to do it. However, the UK system has now been computerised which makes it much more difficult to "fudge it" as all emissions test attempts are recorded on a database.
[To be honest, as well as hopefully helping me solve these issues, another reason I want to do this is out of curiosity because no-one else seems to have fuel injected this little engine type before].
RE: Side by side fuel injectors in open manifold.
A carby with the float bowel directly below the discharge nozzle or jet is a needle type metering jet is used. I think from memory, some SUs and a lot of moror bike carbies are built that way.
Some down draft Webbers also have tall narrow float bowels close to the nozzles. This means a large angle makes little difference between fuel level and fuel discharge point.
Also a throttle body injector will do it. Many D series Honda engines have a dual point fuel injection system. It is throttle body and has low and high speed injectors at the TB. They should be almost free being the low performance option on these engines in the late 80s early 90s.
Regards
Pat
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RE: Side by side fuel injectors in open manifold.
Quite a number of folk have had things to contribute (I'm grateful for all of it) and the scope has become wider than I expected. I asked what seemed a simple question in the first place and have received answers on things I didn't feel I needed an answer to. The only reason this thread has gone on for so long is that almost everyone has their own fixed ideas on how "tuning" should be done, including keeping the carburettor. I've read all the advice, done more research (including from the manufacturers and suppliers), looked into the practicalities and adapted my plan to suit.
I have already tried to politely bring the thread to a close on two occasions. However, folk (including yourself) have continued to post stuff for me, so I feel obliged to give them the courtesy of a reply.
You latched onto something posted by another contributor about increasing power output and wrongly assumed I was building a racing car and was therefore out to gain maximum power. I've never said that. Sorry for any confusion. You gave advice on improving airflow via manifold improvements and seem to expect me to redesign the whole inlet system and re-jig half the engine bay on your say-so.
However, I don't feel inclined to redesign more than I really have to because increasing the power output isn't the main priority. If I wanted to merely wring the maximum power out of the engine then I would put the quadruple motorcycle throttle bodies on it (I have a set of near-new Suzuki 750 TBs in the garage and did look at this on a previous occasion, that's why I bought 'em). Or I could supercharge it, as a couple of other owners have already done, albeit not without sacrificing reliability elsewhere.....
When I've tried to explain what I'm trying to do here in more detail, because of answers given, you seem to become irritated about it. If this is a problem for you, then please feel free to stop replying. If you wish to carry on, then that's just fine too.
Having taken everyone's advice into consideration (not just on this forum) I have now decided how to make the conversion to suit my own needs, the look of the car, the practicalities and the fairly limited budget. The project is moving on.
It's been a very interesting discussion which I note has produced quite a large number of replies compared to other recent topics. If anyone remains interested enough to know how it works out (or not) then I'll report back at a later date with some results.
If not, then I'm happy to finish the thread at this point.
Thankyou, again and peace to you, Pat!