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increasing torque without any big modifications

increasing torque without any big modifications

(OP)
Hello. I wanna ask, how increase engine torque without increasing displacement, compression ratio, and fuel consumption? Or how new engines increase fuel efficiency and power, when compared to older egines? I know, that new engines have higher CR, ecu controlled fuel injection and ignition timming, better designed combustion chambers, variable cams and intake manifold, but that is enough or there is something i missed?

RE: increasing torque without any big modifications

Three basic factors for increasing BMEP:
  1. increase the mass of the stoichiometric trapped charge (excess air, excess fuel, charge diluents & internal coolants do not count, though they might be useful for #2)
  2. burn it more efficiently (increase the effective expansion ratio) - this is in terms of IMEP, not BSFC!!
  3. reduce parasitic losses (piston & ring to cylinder friction, bearings, valvetrain, ancilliaries e.g. oil pump, water pump, etc.)

"Schiefgehen will, was schiefgehen kann" - das Murphygesetz

RE: increasing torque without any big modifications

If you compare those "new engines" to "old engines", you'll probably find that there HAVE been rather big modifications.

RE: increasing torque without any big modifications

(OP)
I compared new engines vs. old, like old 5.0 V8 camaro, and newer civic 1.8 vti, camaro have 108kw at 3800rpm and 333Nm at 2400rpm and 121.4psi BMEP, civic 125kw at 7600rpm and 166Nm at 6300rpm and 168.4psi BMEP. So my second question: is BMEP always proportional to torque and is it calculated from only power stroke (180deg.) or from all strokes (720 deg. in 4 stroke engine)? Sorry for dumb questions, but i'm novice in these things :)

RE: increasing torque without any big modifications

http://hpwizard.com/bmep.html

Your thread title includes "... without any big modifications", but going from an old carbureted points-ignition pushrod Chevrolet small block that was designed in the 1950s to a modern fuel-injected twin-cam pentroof 4-valve-per-cylinder with variable valve timing and with intake and exhaust systems that were designed with the aid of computer software that no one even imagined when the Chevy small block was designed ... is a rather big modification.

RE: increasing torque without any big modifications

(OP)
BrianPetersen, yes, my thread title is wrong, sorry :) maybe it should be, "how increae bmep without increasing air/fuel mixture" :)

RE: increasing torque without any big modifications

(OP)
*increase

RE: increasing torque without any big modifications

Well, if you cannot change anything physical about the engine or how much air and fuel pass through it, you only really have snake oil and magnets left.

- Steve

RE: increasing torque without any big modifications

(OP)
Maybe my question due to my not perfect english knowledge isn't very accurate, but i wanna find out, how much torque possible to increase only "changing software" in ecu, if all engine internals are the same. If i have engine, lets say that 5.0 V8 which i mentioned before, how much torque (or bmep) increasment i can expect, if i change carburetor to multi-point injection with ecu controlled ignition, (or if it already has ecu, if i remap it) and other inlet and exhaust headers, but not increasing my fuel consumption?

Thank You for answers :)

RE: increasing torque without any big modifications

If the ONLY thing you want to change is software (e.g. mapping - e.g. "chip-tuning") then the only scope for improvement involves "losing less". It's really easy to LOSE power by changing settings. Sometimes the factory calibration leaves a little bit on the table for whatever reason. Maybe it's calibrated a little rich at full load in the interest of hopefully having fewer warranty claims, maybe the ignition timing is a little on the safe side in case someone puts too-low octane fuel in it. But typically the factory calibration engineers have some clue what they are doing, and there is usually very little to be found.

Exhaust systems were often restrictive in the bad old days. Nowadays, they are usually pretty well chosen.

Changing carb to fuel injection is a "big modification". It generally involves replacing the intake manifold with one of a completely different design. A manifold for multi-point fuel injection need not be designed for eliminating "puddling" or optimizing cylinder-to-cylinder fuel distribution. Manifolds for V8 engines nowadays look nothing like the traditional intake manifold of the (carbureted) past.

There is no magic involved here. If you get a certain amount of air into the engine, that calls for a certain amount of fuel, and the engine will want a certain ignition timing to run best. If you want to make more torque at a certain engine speed, you have to get more air in. Nothing you tinker with on your computer can do that. It's determined by hard parts ... piston displacement, ports, valves, camshafts, etc.

RE: increasing torque without any big modifications

How much of a reduction in engine life/reliability are you willing to accept?

RE: increasing torque without any big modifications

(OP)

tbuelna - how much ecu remap can reduce engine reliabilty, if ignition timing isn't too much advanced? :)

RE: increasing torque without any big modifications

If you are starting from an "optimum" setup then there is no way but down. ("Optimum" in quotation marks because the "optimum" for emissions may slightly differ from the "optimmum" for fuel consumption which may slightly differ from the "optimum" for power output, etc. But on a well-designed engine, these "optimums" won't actually be very far apart.)

Improper engine tuning can make an engine go kaboom in a big hurry under the right/wrong conditions.

RE: increasing torque without any big modifications

Change gear. :P

RE: increasing torque without any big modifications

(OP)
I wanna ask one question about intake and exhaust headers: i know, that longer and smaller diameter headers are better for lower rpm torque, and shorter and bigger diameter headers are better for hgher rpm torque. I know that in smaller diameter header air is moving faster at lower rpm and having more inertia and in this way increasing volumetric effiency at lower rpm, but at high rpm smaller diameter header becomes restrictive, so at higer rpm bigger diameter is better, but in bigger diameter header at lower rpm air is moving relatively slow and having less inertia (if this info is wrong, maybe someone can correct it). So i know (i think i know) how header diameter affects air flow and torque at certain rpm, but i didn't know how header length affect air flow and torque at certain rpm. Maybe someone can explain, why at higher rpm shorter header is better, and at lower rpm longer header is better?

RE: increasing torque without any big modifications

Quote (Deividas)

Maybe someone can explain, why at higher rpm shorter header is better, and at lower rpm longer header is better?

When the exhaust valve opens, a huge pressure wave is sent throughout the pipe. That pressure wave travels at the speed of sound. When it reaches the atmosphere (or an area increase large enough to simulate one), this pressure wave is reflected as a lower pressure wave (think vacuum). This lower pressure wave travel also at the speed of sound towards the cylinder (yes, against gas flow). When it reaches the valve, it then reflects again as a high pressure wave, but lower than the first one. And this process keeps going on until the pressure stabilizes through the pipe. Of course - in an engine - the pressure never quite stabilize because of the engine cycle.

Because we know the speed at which the waves travel, the trick is to tune the length of the exhaust pipe such that the low pressure wave arrives at the cylinder at a moment where the exhaust valve is open to facilitate the scavenging process. The wave can return in a following cycle or even at another cylinder valve (when there is exhaust collector).

You can see this as the molecules' way to communicate between each other. When the exhaust valve opens, the gas molecules are saying: «We're getting out, make space for us!». Of course, the molecules on the other side of the valve can't really move so they just pass the message along the pipe until it reaches an open end. At this point, the molecules are saying: «We found free space, keep coming!» But that message has to go back to the cylinder where the high pressure is.

The same process is used to tune the intake length, except that a low pressure wave is sent when the intake valve opens («We found free space, send more molecules») and it is reflected as a high pressure wave going toward the cylinder («We found a bunch of molecules; they're coming!»).

Search for «pressure wave» and «fluid dynamics». This article is a good start.

RE: increasing torque without any big modifications

I just realize that in my previous post, I might not have made clear the relation between length and rpm.

If we want the pressure wave to arrive at a certain crank angle after the valve opening (Δθ) and we know the rpm (ω), then the time that is available is Δθ/ω. The pressure wave will travel at the speed of sound (v) through a length of pipe (L). The time taken to do that is L/v. Both these times must be equal, so:

L = (Δθ * v) / ω

So we can see how when the rpm at which we want to tune the exhaust increases, the length of the pipe must decrease (and vice-versa).

This is extremely simplified as the speed of sound will vary throughout the pipe and with many other complex factors, but the principle remains.

RE: increasing torque without any big modifications

....how much ecu remap can reduce engine reliabilty,....?

One set point is particularly important for engine life, -the rev limit. But, also gear shift points.

Other changes are dubious as to their benefit. Most emissions settings are not in play under WOT conditions. The manufacturer's settings are probably best. Unless... you change other things, like the camshafts, modify the heads, exhaust, etc. Then, your driving style will likely hurt engine life and the mods will hurt your wallet when the manufacturer refuses to make repairs under warranty.

RE: increasing torque without any big modifications

(OP)

Quote:

number of power strokes/minute
What do you mean by saying power strokes? I'm asking, because in wikipedia: p(me)=(T*nc/Vd)*2pi, and wikipedia says, that nc is number of revolutions per power stroke (for a 4-stroke engine nc=2)(http://en.wikipedia.org/wiki/Mean_effective_pressu...). So, if power stroke is one of 4 strokes (intake, compression, power, exhaust), how can be 2 revolutions per power stroke, if power stroke is only 180deg crankshaft rotation? Maybe i'm missing something?

RE: increasing torque without any big modifications

(OP)
And also says: "When quoted as an indicated mean effective pressure or IMEP (defined below), it may be thought of as the average pressure acting on a piston during a power stroke of its cycle" and then says: "Indicated mean effective pressure (IMEP) - Mean effective pressure calculated from in cylinder pressure, average in cylinder pressure over engine cycle (720° in a 4 stroke, 360° in a 2 stroke)"

RE: increasing torque without any big modifications

"Two revolutions per power stroke" is describing the frequencyof the power strokes ie on power stroke per two revolutions - not the duration.

je suis charlie

RE: increasing torque without any big modifications

Force more air into it.

RE: increasing torque without any big modifications

Take it to a lower elevation.

RE: increasing torque without any big modifications

Changing your timing and getting rid of parasitics would be the only real options you have left after you take out things that use more fuel. Bigger cams, forced induction, lower intake charge temps, and lower elevation all increase volumetric efficiency which requires more fuel and more air.

Your crank shaft requires a lot of torque to spin it. If you can reduce weight there, you reduce a big parasitic. Otherwise you can change your timing to increase BMEP.

Oh wait, you said without using "more" fuel. Use fuels that have higher energy density, and then change your timing. Thats not against the rules, is it? lol Your only options are strictly BMEP related unless you go after your crank shaft with a grinder. This includes evacuating spent fuel charge more effectively

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

Timing has a massive effect on engine power. Changing 2 degrees of timing can yeild 5-7% power gains. Manufacturers set up their engines with some room for error in fuels, failure effects, and adverse conditions. They dyno test engines on E-10 fuel which is always the same. That fuel in the pump down at the kum & go truck stop isn't quite as consistent, so they have the timing retarded enough to compensate for detonation that might come from running crappy fuel and climbing the rocky mountains while towing at 100% capacity in 120 degree heat. You can tune your own ignition for your specific intents and purposes and get noticeable gains in power depending on how the stock ignition map was set up. Some modern cars are doing an excellent job of it, other cars need about 4 degrees of timing added at some points.

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

"5.0 V8 which i mentioned before, how much torque (or bmep) increasment i can expect, if i change carburetor to multi-point injection with ecu controlled ignition, (or if it already has ecu, if i remap it) and other inlet and exhaust headers, but not increasing my fuel consumption?"

You will lose power if you go to port EFI. Every car lost power when they switched to port injection EFI in the 80s. I have a 1999 mustang GT that I converted to run a carburetor and it gained 10% on the dyno with the same stock EFI intake that it was using EFI with. The igntition map was also identical to stock. Then I changed the ignition map and gained another 5% in power. So my carburetor conversion and ignition remap gained me 15% rear wheel horsepower. If you have EFI and a modern 4 barrel carburetor running the same air fuel ratio, the carburetor will usually make more power. They have an intercooling effect on the intake charge as well as significantly better fuel atomizing. Even Throttle Body Injection makes more sense for peak performance than port fuel injection. However, port EFI is ultra easy to dial in and get it running at its full potential. Carburetors take skill to tune correctly, and you have to re-tune them when conditions change.

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

(OP)
Panther140 - Thank You for answers :)

RE: increasing torque without any big modifications

"You will lose power if you go to port EFI"
The only race cars that still use carburettors are the ones that are mandated by rules. The rest use multi-point fuel injection. I guess they should all go back to carbies?

je suis charlie

RE: increasing torque without any big modifications

Quote (Panther140)



Your crank shaft requires a lot of torque to spin it. If you can reduce weight there, you reduce a big parasitic. Otherwise you can change your timing to increase BMEP.
That's an interesting statement. Can you please give the physical basis for it?

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: increasing torque without any big modifications

"Every car lost power when they switched to port injection EFI in the 80s"

Takes only ONE counterexample to disprove that, and it's a vehicle that I owned a (carb) example of.

Toyota 22R carb, 97 hp (1981-1990)
Toyota 22RE EFI, 105 hp (1983-1984) and there was a redesign in 1985 that increased it even further. Most of them were 114 hp (1985-1997). The 1983-1984 carb versus EFI models are directly comparable and were available in the same vehicles (base models got carb, higher models got EFI) ... carb 97 hp, EFI 105 hp.

RE: increasing torque without any big modifications

Carburettor obsolescence. A real shame for those who love the inspired and beautiful engineering. But the contraption really is obsolete now. Simply not up to the job required - mass-market closed-loop transient AFR control. On the same scrap heap as the equally brilliant distributor diesel fuel pumps that were far more exciting and clever than the engines they were connected to.

I got quite good at coaxing a fantastic picture from my last and best CRT display. I could go through all the settings to get that thing calibrated for a perfect picture on a good day, winding out drifts and compensating for environmental conditions. And regular degaussing. It was a shame to see it on the heap at the local recycle station, with all the others. My flat panel displays lose to the CRT in some areas, but they are overall better and more fit for purpose.

Steve

RE: increasing torque without any big modifications

hemi - a V8 Crankshaft weighs 50-80 lbs, usually has a pretty big radius, and spins 5,500 RPM. One thing we do to test engine parasitics on an electric dyno is to spin the engine over by using the electric dyno and measuring how much power it actually took to spin the engine. This huge moment of inertia in crossplane counterweighted V8s is one reason flat plane cranks are preferred for a lot of racing applications.

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

gruntguru- They are using port EFI because it can be adjusted real time. That is the advantage of it. It is always running right.

Port EFI's claim to fame - "I will always run the right AFR"

4 Barrel Carburetor's claim - "I will deliver more horsepower than EFI if we are both running the same AFR"

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

Hi Panther,

when you did your carburetor conversion what intake manifold did you use?
Did you have to spend any time equalizing cylinder-to-cylinder airflow?
Did you have to spend any time equalizing cylinder-to-cylinder AFR?

Do you happen to have the dyno tests of FI vs carburetor?

regards,

Dan T

RE: increasing torque without any big modifications

Tmoose - I used the stock EFI intake manifold. Everything on the car was bone stock except for the carburetor and ignition module at the time. I just made an adapter to bolt onto the intake manifold that would allow me to bolt a 4 barrel carburetor to it.

I did not spend any of my own time equalizing cylinder-to-cylinder airflow. I sometimes put a thermometer at various parts of the exhaust manifold just in case something extreme happens with the EGTs. I am trusting that the OEM intake manifold distributes air evenly enough that its not worth messing with.

Cylinder-to-cylinder AFR was not checked, because each cylinder bank is getting identical AFR at all times.

I recently moved (this week) but I will try to find those charts.

In the mean time: https://www.youtube.com/watch?v=_mYhKfSIRVQ

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

Panther140 Quote:
Cylinder-to-cylinder AFR was not checked, because each cylinder bank is getting identical AFR at all times.

Not very likely. Port fuel injection manifolds are designed for even air distribution with out regard for even fuel distribution. It is very difficult to get both even fuel and air distribution, something the old carb manifold designers had to deal with.

The problem with carbs is you can get good power, good fuel economy or good emissions. Choose one. The others will have to suffer. So in today's emissions controlled environment a carbureted engine (aren't many left other than lawn mowers) will suffer in both fuel economy and power.

And I seriously don't believe your claim of decreased power output when the switch was made from carbs to EFI in the 80's. As the emissions requirements increased the carb engine power outputs were dropping like a stone. It took EFI & the 3 way cat to save the automobile for some truly awful engines.

Just take the evolution from the last C3 Vette to the first port injected C4 Vette.
In 1981, there was only one powerplant available, a 350 cu in (5.7 L) carbureted engine that produced 190 hp.
1982 saw the debut of the “Cross-Fire Injection” TBI system, the engine produced 200 hp (continued in the first C4's).
The new 1985 L98 350 added tuned-port fuel injection, which was standard on all 1985–1991 Corvettes. It was rated at 230 bhp for 1985–1986, 240 bhp for 1987-1989.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

RE: increasing torque without any big modifications

Be sure you're comparing apples to apples here. That crossfire 350 does not represent the Port EFI that I am comparing modern carburetors to. Nor does it represent a controlled experiment as it has 10% higher compression than the 1981 car. The 1985 mustang GT made 210 horsepower with a 5.0 and a carburetor. The 1986 Mustang 5.0 made 200 horsepower with EFI and higher compression in the same engine.

Also, why did you choose a car with TBI to represent your cylinder-to-cylinder tuning concept? They also bumped the compression ratio up from 8.2 to 9. Thats a big difference when you are dealing with low numbers like that. In my opinion, TBI has more in common with a carburetor than it is to Port EFI. That is why I have specifically been referring to port efi to modern carburetors. I am only making the claim that there are things that a carburetor does that port EFI does not, and one of those things is having the most potential for peak horsepower. I'm not saying that EFI isn't great at everything else. If you have money and need to adapt your car to conditions in just 3 practice laps, then go with EFI.

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

Quote (Panther140)

a V8 Crankshaft weighs 50-80 lbs, usually has a pretty big radius, and spins 5,500 RPM. One thing we do to test engine parasitics on an electric dyno is to spin the engine over by using the electric dyno and measuring how much power it actually took to spin the engine.
There is no doubt that a larger radius journal bearing will consume more torque to spin at a given rpm, than a smaller radius journal bearing. But that is not what you claimed in your original statement:

Quote (Panther140)

Your crank shaft requires a lot of torque to spin it. If you can reduce weight there, you reduce a big parasitic.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: increasing torque without any big modifications

Quote (Panther140)

4 Barrel Carburetor's claim - "I will deliver more horsepower than EFI if we are both running the same AFR"
,
While I agree that there were some very elegantly optimized carburetor setups back in the day, I don't subscribe to that generalization. For the simple reason that, a carburetor that is accurate from part to full load of necessity imposes an appreciable air flow restriction at WOT, in order to have a sufficiently accurate pressure drop vs flow to be used as a signal for fuel metering. Of course, some fuel injection air metering systems impose their own pressure drop (e.g. vane meter, MAF), but these can typically be of lower order than a state of the art accurate carburetor.
Furthermore, when considering PFI vs single point carburetor, air manifold design imposes its own restriction to airflow, in order to mitigate inherent maldistribution issues of air and fuel of a single point system. I hasten to add, PFI systems are not perfect, just inherently better than single point carburetors, in this regard.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: increasing torque without any big modifications

hemi- I am having trouble viewing the maldistribution of air being inherent only to carburetors. PFI also has a single point of induction for air in their manifolds just like most carb setups. In fact, I am using an EFI intake manifold with my carburetor. Does my carburetor make it distribute air less evenly than the EFI throttle body allowed it to? If not. then why would it not be distributing fuel/air as evenly as it did with EFI? Is it not true that all of the air coming through my carburetor is uniformly mixed with fuel and air? Unless certain parts of the intake manifold are getting air from some other point of entry than the carburetor, I don't see how the AFR would be different in any cylinder. All of the cylinders are pulling air from the same point, which meters every cubic foot of air equally. Slightly off this exact topic - You can have 1 carburetor per cylinder! It works well.

Carburetors meter all of the air coming into the manifold. If there is air in the manifold, it theoretically already has the correct amount of fuel metered into it.

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

Maldistribution is not inherent to carburetors, it is inherent to single point fuel mixing. Yes, the AFR might be OK right after the mixing point (carburetor or TBI), but due to the inertia forces, the fuel can leave one point of the air stream to go to another, sometimes accumulating on intake walls. This is how cylinders can end up with different AFR if one receive the «lean» portion of the airstream and another one the «rich» portion.

RE: increasing torque without any big modifications

Panther140, I take it you have not heard of fuel puddling and wall wetting. While not unknown to PFI, the problem is much more pronounced with single point metering. To counteract this issue, single point manifold geometries are "gerry-mandered" to coax the liquid fuel on the walls to distribute itself roughly equally. This tends to undermine efforts to achieve absolutely equal air distribution, not to mention minimize flow restriction.
Regarding 1 carb/cyl., I agree, it works well (assuming proficient application & calibration), but is OT relative to your original claim regarding 4BBL carburetors.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: increasing torque without any big modifications

Quote (Panther140)

....a V8 Crankshaft weighs 50-80 lbs, usually has a pretty big radius, and spins 5,500 RPM. One thing we do to test engine parasitics on an electric dyno is to spin the engine over by using the electric dyno and measuring how much power it actually took to spin the engine. This huge moment of inertia in crossplane counterweighted V8s is one reason flat plane cranks are preferred for a lot of racing applications....

The rotating mass of the crankshaft is dynamically balanced by the counterweights and produces very little mechanical losses at the main bearings. Most of the mechanical friction losses in a recip engine are due to the dynamic forces produced by the reciprocating conrod and piston masses, and the high sliding frictions at the ring and piston skirt contacts from high combustion gas pressures.

RE: increasing torque without any big modifications

High performance motorcycle engines have been one carb per cylinder historically. In all forms of top-level motorcycle roadracing, carbs are gone and will not be coming back. If it were really possible to make more power with a carb, they would have stuck with them, particularly in the MotoGP classes which are not subject to being built from a road bike that has to meet emission standards.

The high-performance bike EFI systems usually use two injectors per cylinder nowadays - one near the port downstream of the throttle, and one in the airbox pointing straight down the intake runner.

RE: increasing torque without any big modifications

Panther said - "..snipped..... Is it not true that all of the air coming through my carburetor is uniformly mixed with fuel and air? Unless certain parts of the intake manifold are getting air from some other point of entry than the carburetor, I don't see how the AFR would be different in any cylinder. All of the cylinders are pulling air from the same point, which meters every cubic foot of air equally. .........
Carburetors meter all of the air coming into the manifold. If there is air in the manifold, it theoretically already has the correct amount of fuel metered into it."

=========
I think most sources would say the fuel provided by a carburetor is far from evenly distributed and thoroughly and uniformly mixed. Testing on the dyno may not simulate what acceleration does to the fuel in the carb, or the multi-phase mixture flowing into the engine.
https://www.youtube.com/watch?v=s-q1eJu1Wz8

=================

AMC Rambler's best effort to create equal AF ratio back in 1957 or so.
http://worldpowersystems.com/AMC/Rambler-327/The%2...

===================

" At this point, it hadn't yet become evident to dyno users that the use of in-car pieces (headers, ignition systems, cooling systems, etc.) on the test stand would be a logical step toward the need for linking engine testing with on-track performance. The importance of this fact was brought solidly home to me in the mid-'70s when sorting out some cylinder-to-cylinder mixture distribution fixes in a now bygone "Smokey Ram" intake manifold. Distribution fixes Smokey had determined on the dyno barely resembled what were required on the track."

Read more: http://www.hotrod.com/how-to/engine/ctrp-0808-powe...
Follow us: @HotRodMagazine on Twitter | HotRodMag on Facebook

================
From the Hilborn INJECTION SITE -
http://www.hilborninjection.com/tech_elect_manifol...
"First it is important to keep in mind that the air and fuel have not mixed into a homogenous mixture in the venturi of the carburetor or in the runner of the intake manifold. A homogenous mixture is defined as a mixture whose physical properties are uniform throughout. Fuel in the manifold is not uniformly mixed as this only happens under the extreme heat and pressure contained in the combustion chamber. In reality, fuel in the intake tract uses air as a carrier; therefore, it is relatively easy for fuel to fall out of suspension, causing mixture distribution concerns."
And lots more.

==============

Here is a thread on a bulletin board showing some of the stunts that sometime have to be used to get carbs on "high performance" V8 manifolds to get the right amount of fuel to flow to the dry sections of the manifold.
http://racingfuelsystems.myfunforum.org/viewtopic....

============
Post 10 here shows some of the carb assymetry applied by Chevrolet to improve the fuel distribution on the legendary L88 engine.
http://racingfuelsystems.myfunforum.org/viewtopic....

RE: increasing torque without any big modifications

Tmoose - Those are all good points. I hadnt completely considered the potential for maldistribution of fuel from carburetors. I am going to look into getting another carburetor and a better intake manifold now if I find that my car is indeed not running like it should. That should farther improve my peak power over stock.

Tbuelna - I wasn't really talking about friction as much I was talking about the actual rotating mass of the crankshaft and how it affects acceleration through the RPM range. Crankshafts have mass, which rotates. It takes torque to spin a mass in a circle. It takes more torque to spin that same mass in a circle if the mass is farther away from the center (higher moment of inertia).

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

(OP)

Quote:

The high-performance bike EFI systems usually use two injectors per cylinder nowadays - one near the port downstream of the throttle, and one in the airbox pointing straight down the intake runner.
I also saw two injectors per cylinder in sports cars, but i don't understand purpose of second row of injectors. Is it for better fuel evaporation at high rpm's or for what?

RE: increasing torque without any big modifications

You can meter fuel more precisely at low RPM with 2 smaller sized injectors than with one large one. Injecting fuel earlier with the air also cools the intake charge, atomizes the fuel better, and makes the air more dense

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

With the motorcycle systems, the lower injectors (downstream of the throttles) are active all the time for driveability and emissions, and the upper injectors are only active beyond a certain engine load (near full throttle) generally in the upper half of the RPM range. Both sets of injectors act together when the engine is near full load and high revs.

RE: increasing torque without any big modifications

Quote (Panther140)

Your crank shaft requires a lot of torque to spin it. If you can reduce weight there, you reduce a big parasitic.

Quote (Panther140)

Tbuelna - I wasn't really talking about friction as much I was talking about the actual rotating mass of the crankshaft and how it affects acceleration through the RPM range. Crankshafts have mass, which rotates. It takes torque to spin a mass in a circle increase the rotational speed of an object with non-zero rotational inertia [edit by hemi]. It takes more torque to spin that same mass in a circle increase the rotational speed of an object with the same mass if the mass distribution is farther away from the rotational center (higher moment of inertia)[edits by hemi].
If my edits for clarity are accepted, that is all true, but I don't consider rotational inertia as a source of parasitic loss. Of course you have to invest energy accelerating the rotating masses (everything from the crankshaft to the wheels, not to mention the reciprocating parts of the cranktrain, i.e. pistons & rods), so we all understand the value of reducing their moments of inertia as much as practicable (respectively, masses of the rod small end and piston), but at least for everything forward of the gearbox, that energy can be harvested to some extent when shifting. I don't know, and I haven't bothered to do the analysis, but some straight line racers I know assert that a heavy flywheel, when spun up to redline or so prior to the start of a race, can produce faster net acceleration times than a light flywheel.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: increasing torque without any big modifications

You could get a 48 hp VW Rabbit diesel to lay rubber off the line by spinning up the engine to 4000 rpm and dumping the clutch. That engine needed a heavy flywheel due to the 22:1 compression.

The momentary hard acceleration you got from doing that, was the only hard acceleration you got ...

RE: increasing torque without any big modifications

Right, a heavier flywheel and crankshaft would get you better launches based on simple conservation of momentum. The heavier flywheel also improves tractability for engines that would otherwise have abrupt powerbands

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

A friend picked me up to go skiing in his Tercel Diesel. There was about a foot of snow on the ground, a real rarity in SC. He was dumping the clutch and driving like a mad man, when I suggested he take it a little easier he said "When you drive a Toyota diesel and you have an opportunity to spin the tires you have to take it".

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RE: increasing torque without any big modifications

(OP)

Quote:

You can meter fuel more precisely at low RPM with 2 smaller sized injectors than with one large one. Injecting fuel earlier with the air also cools the intake charge, atomizes the fuel better, and makes the air more dense
I think, that nowadays ECU can easily control 1000cc or bigger injectors at idle or low load, so why not to use one big injector further from intake port? With one injector per cylinder it's also easier to adjust ECU. Maybe there is more advantages to use one injector near intake port and one near throttles than one big?

RE: increasing torque without any big modifications

Deividas - I think size of the injector could affect fuel droplet size and the duration that it can be injected for. Id imagine that a longer "cutoff ratio" relative to the time that air flowing in would have an advantage. Also, if you have multiple intake ports per cylinder it would make sense that you would want 1 per port or have one upstream to have more time to mix with the air, but one downstream so that there isn't as much puddling effect on the walls of the runner. 2 injectors per cylinder probably makes more sense for some engines than others

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

The injector downstream of the throttle and near the intake valve is necessary for driveability and emissions at light engine load (shut throttle). Fuel injected at this injector either goes straight into the cylinder, or lands on either the backside of the intake valve or the inside of the intake port which is hot when the engine is warmed up, and on top of that, it is downstream of the throttle and under light load, this throttle is nearly shut and has a big pressure drop across it so the air that is getting through is very turbulent (which is better for fuel mixing). Cannot do that if the injector is far upstream.

But on the other hand ... when the throttle is nearly open and the engine is spinning fast, fuel injected further upstream has more time to mix with the air and partially evaporate, cooling the intake charge. The throttle is open or nearly so when these injectors are in use, so there is no issue with the fuel droplets landing on the throttle blade and accumulating and then being fed to the engine in (relatively) huge drops, which is what would happen if you tried to use the upstream injectors at light engine load.

RE: increasing torque without any big modifications

Hi all,
Just read this thread so I may be a bit late, but just my observations.

I have a GMC motorhome, the one GMC designed and built back in the 70's using the Oldsmobile Tornado front wheel drive train. It came with a 455ci engine with a quadrajet carb. (www.gmcers.org)

When I bought it in 2008, the original card had been changed to an aftermarket Rochester 4 barrel carb. It had the usual carburetor issues (hard starting, hesitation, wont come off high idle, dieseling) all that good stuff. There is TBI kit for these machines from Howell EFI (www.howellefi.com), so I went with the EFI kit. It took me a bit to get all the bugs out of the system, but now it starts and runs like a modern engine.

I also added a more up to date engine control computer system (www.dynamicefi.com) and electronic spark control.

I had to learn about and deal with things like fuel condensing on the runner walls when the engine was cold, and clearing out the rich mixture from puddling (but that only happens from stone cold start-up in my case).

As far as torque and fuel mileage goes it does have more pep, although the electronic spark control seemed to make more difference there than the EFI. GMCer's say with a well tuned carb engine you will get 8 to 10mpg depending on whether you tow a car with you. I never had a good carb on it, but with highway lean cruise and deceleration fuel cut-off I have no problems getting over 10mpg even with my jackrabbit starts.

Just my experience

RE: increasing torque without any big modifications

A second genera+ion Quadraje+ <65 and up> is a good carb, among +he bes+ OEM carbs ever , when in good +une. Ay, +heres +he rub <and +ha+ app1ies +o a11 carbs>. Sorry for +he unconven+iona1 +yping; my keyboard is gimba11ed 3eyes

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: increasing torque without any big modifications

hemi you should send work emails typed like that haha.

So id concede this debate with a conclusion along the lines of: EFI is great at a broad field of applications (soccer moms driving vans to engine tuners tuning a car in real time). Carbs are great for shadetree mechanics and they have their place in some racing applications

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

Carbs are an ingenious solution running out of problems to solve.

Steve

RE: increasing torque without any big modifications

EFI will never look as lovely as these, efficient though it may be: Glorious

www.tynevalleyplastics.co.uk

It's ok to soar like an eagle, but weasels don't get sucked into jet engines.

RE: increasing torque without any big modifications

Yeah I suppose I shouldn't rag on EFI too much. It keeps my department pretty busy thumbsup2 Once I can do it myself, my car is going to have direct injection and a very high compression ratio. Until then, I'm loving my carburetor

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

Lower gear ratio's means more torque.

RE: increasing torque without any big modifications

One thing you can also do is to make sure you are combusting the fuel at the ideal time, and making it combust as fast as possible.

Have you ever heard of a turbulent jet igniter? It does this VERY well. There are a few variations to it, but they all work in the same way. They ignite the fuel charge with the turbulent particles instead of directly exposing the charge to the spark.

You get a much more uniform and instant burn when using one. That means you can have the fuel/air charge release more of its energy when most optimal. The combustion will be more precisely concentrated, which allows you to get higher combustion pressure when you want it.

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

RE: increasing torque without any big modifications

Is your supposition that the "turbulent jet ignitor" can be retrofitted to a run-of-the-mill engine? If so, do tell.

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

RE: increasing torque without any big modifications

Forced induction!

RE: increasing torque without any big modifications

The "turbulent jet ignition" looks like a modernized version of the old Honda CVCC system.

Lean-burn might be an efficiency-improver in some circumstances but it is not a power/torque adder. The engine will make less torque in lean-burn mode than in stoich mode.

MAHLE is a large and reputable company, so something of this sort coming from them warrants paying more attention to it than if it were coming from the usual quacks.

RE: increasing torque without any big modifications

The main differene to CVCC is the volume of the pre-chamber - very small and contributing only a tiny fraction of total combustion energy. The process is simple - air or lean mix enters the igniter from the cylinder during the compression stroke. The igniter has its own injector which adds a minute quantity of fuel and a spark plug to set it off. Much simpler than the CVCC which had two seperate induction paths.

There are a few papers by William Attard who worked on this research with Harry Watson at Melbourne University before going to work for Mahle.

je suis charlie

RE: increasing torque without any big modifications

It allows a more uniform and precise combustion. My thought is that you could get the fuel to burn more quickly and have the cylinder pressure concentrated to a more ideal portion of the piston's stroke. Of course, the benefits would vary depending on how efficient the combustion chamber is that you're working with. Im also thinking this would help with knock limitations. Lean burn is one benefit, but I think there is potential for getting more work out of the given fuel & air already being brought into the engine.

And there are various versions of turbulent jet igniters that could work in certain engines without changing the architecture. Spark plug angle is important here

"Formal education is a weapon, whose effect depends on who holds it in his hands and at whom it is aimed." ~ Joseph Stalin

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