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Multiple fuel injectors

Multiple fuel injectors

Multiple fuel injectors

(OP)
Don't ask why I'm asking this, but...

Can anyone point me to an example of a port injected gasoline engine that uses more than one injector per port?  These may be in series (i.e. one before the other) or both located the same distance from the intake valve.

- Steve

RE: Multiple fuel injectors


Not exactly what you're after, but related:  
http://www.sae.org/automag/techbriefs/12-2006/1-114-12-20.pdf
Lexus gives V6 dual injection
The latest and most powerful member of Toyota's
GR-series V6 family, the 2GR-FSE, encompasses
the company's leading-edge injection gasoline
engine technology. As fitted to the Lexus IS350
and other Toyota models, it employs two (port
and direct) injectors per cylinder with new "double
vertical fan-shaped spray" to achieve a homogeneous
and dense fuel mist.

custom bike setup
http://www.rbracing-rsr.com/zx11tubo.htm
RB Racing only builds sophisticated state of the art systems that feature: ... custom throttle bodies w/2 injectors per port;

Honda bike setup
http://www.superbikeplanet.com/2004/Sep/040909a.htm
Dual Stage Fuel Injection (DSFI) system features two injectors per cylinder.

 

RE: Multiple fuel injectors

(OP)
Interesting, thanks.

The Toyota one sounds reassuringly expensive.  I didn't think anyone would employ both systems on a single engine!

The Honda one sounds a bit like their solution to a driveability problem.  I wonder if the FSAE crowd use these engines??

- Steve

RE: Multiple fuel injectors

The original Corvette ZR1 used 2 injectors per cylinder as well as the Maclaren (SP?) F1 road car.   

RE: Multiple fuel injectors

The FSAE crowd usually runs the 600RR's with only one injector per cylinder.  Since your air flow is limited by the restrictor there's little to gain.  The team's I've talked to had a heckuva time trying to tune it and get drivability with staged injectors while not being Honda.

RE: Multiple fuel injectors

Drag racers use multiple injectors per cylinder, but only when they need more fuel than a single injector per cylinder can supply while maintaining a precise fuel curve.  Otherwise it's not worth the hassle of tuning the system.

RE: Multiple fuel injectors

Cool, I forgot about the rotaries.  My old RX-7 only had 2 per rotor even though it was a "6 port" engine.

RE: Multiple fuel injectors

Drag racers normally use multiple injectors when using alcohol or nitromethane fuel. I have never seen them on a drag race petrol engine that was not supercharged or a rotary.

Drag race engines with roots blowers normally put some fuel in above the blower to lubricate, cool and seal the rotors, then some into the port to fine tune distribution. As a general rule on American V8s they run carbies for petrol and mechanical fuel injection for alcohol, but they run EFI on smaller engines. The tendency not to run EFI on bigger engines is the limits imposed by fuel flow through the injectors and the need for costly multi injector systems. I am not saying no one does it, I a just pointing ut what the vast majority do and why.  

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers for professional engineers
 

RE: Multiple fuel injectors

I seem to remember a Kawasaki motor that had an injector at the throttle body to enrichen on high speed runs. Something to do with the pressurized air box.

Cheers

I don't know anything but the people that do.

RE: Multiple fuel injectors

Quite a few production motorcycle engines use two injectors per port. There is an "inner" one at the usual location just downstream of the throttle, and an "outer" one that uses a shower-type spray patter in the airbox pointed down each intake runner.

Current-production Honda CBR600RR is like this, to give but one example.

RE: Multiple fuel injectors

In the late 80s it was difficult to get good idle control from an injector that was big enough to flow enough fuel for WOT, for turbo engines in particular. So a fairly common solution was to use multiple injectors. I vaguely remember Lotus ran 6 injectors on the 4 cylinder Turbo.



 

Cheers

Greg Locock

SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.

RE: Multiple fuel injectors

It is not uncommon in street drag racing engines to have two complete fuel systems, one for street use-91-octane and one with race gas/alcohol and nitrous oxide.

Back in the bad old days, when EFI was new and large capacity injectors were not available, I tried my hand with a Haltec F1 with a wiring harness for sixteen injectors.  It was a staged system, but the software was not able to handle the progressive transition.  Not surprising it didn't survive.

thnx, jack vines

RE: Multiple fuel injectors

In designing a system for 2 injectors it really has to do with needs.

In my quest for ever increasing VE and greater boost pressures you soon find that the amount an injector can flow to the amount the stock ECU can control becomes an issue.

Say you have a turbo charged SAAB. ( my favorite) and on 94octane I can run 28lbs of boost with a 9.5-1CR. (I can and do)

The problem becomes in theory that for the amount of HP say 320HP I am supposed to run 46lbs injectors for the Inline 2.0L engine.

On standard Bosch 2.4LH the system can't handle the timing of the injectors though they are fired in batch.

So, the next step is to make(megasquirt) or buy an aftermarket that will control the injector.

This sounds good right. Well, with that large of injector you will have a hard time at idle to set it up and fuel MPG will suffer.

the next best solution is to keep the stock 24lbs injectors and add another further upstream pointed up the runner not down.

Use a throttle switch and pressure switch to control the on/off of the secondary injectors and just use the pulse signal from the main bank as the trigger signal for the secondary injectors. You can setup a small relay circuit for the secondary injectors.

Anyhow, in the next few months I am actually building such a system as a test bed for some parts I am producing. Should be interesting.

RE: Multiple fuel injectors

We discussed this recently (in relation to a dual-injector Corvette) but I couldn't find the thread again.  

There are ECUs available that will control large injectors at idle.

RE: Multiple fuel injectors

FWIW MegaSquirt has more than enough resolution to accurately control large injectors (like  46 pounders) at idle and low load. I know plenty of guys using 46 lb/hr or larger injectors with MS and they have no issues at all and still have good fuel economy.

I use 60 lb injectors on my 2.0 twincharged SVT Focus running upwards of 25 lbs of boost and I had perfectly good low load and idle fuel control using the a modified OEM ECU and later on using a Haltech E6X. I have lost economy but that is to be expected when adding a roots blower and a turbo.

Take a look at your fuel pressures and lower them if you don't need extra headroom. If you can flow enough fuel through your injectors at WOT and 45 PSI of fuel pressure, why keep fuel pressure at 60 PSI and decrease injector pulsewidth down to the point where the injector can't respond quick enough? So long as you still get a good spray pattern AND you don't max the injector out during peak fuel consumption, a lower fuel system pressure does nothing but increase your accuracy.

RE: Multiple fuel injectors

Actually we sell and use an engine management system called Big Stuff 3. It is a sequential efi system and can drive at least two sets of injectors.  The injectors can be different sizes for the primary and secondary. Its very easy to do. You size the smaller injector like you would for light load, idle and cruise and after you go to wide open throttle and reach a user definable parameter like 82% injector duty cycle. The ECU switches, determines the fueling strategy and controls the second bank of injectors as well. If you only run at WOT like in drag racing, it would be no different.  We use 16 injectors at 160 lbs/hr at 65 psi. Alcohol would also work fine. We run mid 6 sec at over 210 mph at 3045 lbs on race gas.  It would be no different for pump gas.  The system is a stand alone engine management system that's model based, so it's reasonably easy to configure and tune.  You have complete control of timing, fuel and target air/fuel if in closed loop and many other parameters.  If this is something along the lines of why you are asking the question and need more info, email me. -- Mike

RE: Multiple fuel injectors

Look at www.nelsonracingengines.com

They have set-ups like mentioned above - octane on demand is what they call it.   

RE: Multiple fuel injectors

A comment like octane on demand does slightly less than zilch for their credibility.

Regards
Pat
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RE: Multiple fuel injectors

(OP)
My innocent, low key question seems to have attracted all the petrol heads.  My reason for the original question was quite mundane - I was probing to see if a restriction on fuel injectors to one per location was likely to be a problem in a simulation.

- Steve

RE: Multiple fuel injectors

Steve

Unfortunately your OP was not that specific.

Now that you have specified, many of the above posts could be considered off topic from this point on.

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers for professional engineers
 

RE: Multiple fuel injectors

(OP)
... nevertheless, the replies have all been interesting and educational, so thanks to all.

- Steve

RE: Multiple fuel injectors

Mazda Rotary engines used two injectors for years. One injector, the primary fed fuel all of the time. The secondary injector (the ones that were easy to see) only fed fuel under load, and when the intake runner control system was activated.

The Lexus system uses a typical intake runner injector, and the second injector is a direct injection system ( direct into the combustion chamber). This system makes use of a "stratified charge" for improved performance and emission standards.

One thing that never seems considered strongly enough is exactly how a technician is supposed to analyze a problem when a problem with a system like this finally occurs. I can easily envision individual cylinders suffering a fuel density missfire and only under specific engine load conditions. Which could mean, no way for the tech to re-create the conditions in the bay, and nothing but intuition to rely on for figuring out the problem with a customers vehicle. Sure some will say on-board diagnostics will show us what cylinder is miss firing and when, but truly almost everything else about the failure will be completely unknown. That amounts to too many variables that can only be worked through in lab type settings, where time isn't a factor. Meanwhile a technician is expected to diagnose the problem in a flat period of time, and then repair the circuit or change a part and always be correct the first time. That's a standard that if put to the test, NO-ONE could ever completely live up to.

RE: Multiple fuel injectors

"A comment like octane on demand does slightly less than zilch for their credibility."

So running 91 oct from one fuel cell on one set of injectors, and 116 from another fuel cell to the other set indicates, what, zilch on their credibility?  
They may not be degree certified engineers, but their ingenuity is commendable - maybe not their tagline.  I only quoted what they say.  

Take a look at their products and then give an opinion.  

Nevertheless, to run those injectors, if I remember right, they use Electromotive's TEC³.  The guy wanted examples of engines running multiple injectors.  DON'T be so quick to judge.

RE: Multiple fuel injectors

If they said that it had 2 fuel tanks, it was certainly well hidden amongst the smoke and mirrors.

I just wasted another half hour not prejudging the Lets get edjumacated video. As expected after seeing the gloss and glitter preceding it, it was kindergarten level with a Las Vegas façade.

 

Regards
Pat
See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers for professional engineers
 

RE: Multiple fuel injectors

I don't know if this is helpful but the 2003-2006 Ford GT had 2 injectors per cylinder on it's 5.4L dohc supercharged motor.

RE: Multiple fuel injectors

In the aftermarket world look at the Big Stuff 3.  It has the ability to control 16 injectors and in a V-8 or less provide staged injection.  Once the first stage hits 80% duty cycle (or whatever you decide) the second set picks up the slack.

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