Has anyone tried this EFI idea in a log head?

[Anlushac11]

8)

I was just looking at how the runners come off the log and slope down into the head.

Has anyone considered installing injectors under the log in the underside of the runner?

You would have to install a heatshield to protect the injectors and fuel lines from heat but it seems it would be easy to do.

And I would use stainless or braided stainless fuel lines to reduce any chance of leaks.

Just an idea, wanted to know your thoughts on the idea.

 

[rbohm]

for port fuel injection to be most efficient the injectors should be pointed at the intake valve. the best location for port injectors on the log head would then be in the log itself pointed straight down the ports at the valves.

 

[Thad]

The log head does not have a really equal air flow to each port, whereas the injectors would be injecting the same amount of fuel at each port, some cylinders would be rich or lean compared to others.
Probably the most effective efi using the log would be TBI.
IMHO

 

[Asa]

wonder if you could get around that by boring out holes in the log so that airflow would be equal along the head, then just mount an air-filter to each one, or hook them all up to one...
how sexy would one open-element chrome air filter about the same size as the valve cover be running along side of it?
yeah baby

 

[rbohm]

8) actually thad the problem is getting the air and fuel to the port together. remember air is far more willing to turn corners than fuel is, and that is what the port fuel injection would equalize. yes the inner cylinders would still run a bit rich and the outer cylinder would run a bit lean, but the a/f ratios between them would be much much closer than they are with a carb or even with tbi injection, remember you still have to get the fuel to turn the corner which it does not want to do.

 

[Anonymous]

I would bet that the dry flow of a big-log head is quite even under normal RPMs. While the fore and aft cylinders are further away from the central intake hole, they benefit from tuning effect in compensation.

As for aiming the injector at the valve itself, this is primarily an emissions consideration, employed to ensure that the max possible amount of fuel enters the cylinder instead of evaporating into the atmosphere. Conversely, most racing engines position the injector as far as possible from the valve to give the fuel maximum time to evaporate. The act of evaporating has two functions: the first is to cool the charge and hence increase its density and therefore maximize the engine's volumetric efficiency. The second is to minimize the number and size of fuel droplets that enter the cylinder. Liquid fuel can't combust, and since racing engines are by definition trying to make the most power, their designers want to ensure that the fuel is as fully evaporized as is practical prior to the fuel passing the intake valve.

Therefore, for a turd-head engine, placing the injectors above the centerline of the intake runner on the outside of the log would probably be the most effective position from a high revving, max performance standpoint. That having been said, there is nothing intrinsically wrong with positioning the injectors on the bottom of the runner. By squirting the fuel against the opposite wall of the runner (the top wall in this case), the fuel has more opportunity to evaporate prior to entering the cylinder (always a good thing) and yet mixture imbalances are minimized by injecting closer to the valve than if the injectors were on the outside of the log. Of course, with the injectors on the bottom, one would still have the heat transfer issue to deal with.

FWIW, the latest generation of Formula Atlantics, the Swift 014a, positions the injectors on the bottom of the runners. In their case it's for packaging considerations, but there was no performance penalty compared to the traditional position on top. These engines pump out about 240 hp from 97 CID (1600cc) at 10,000 RPM, too, so don't get the impression that they're some weenie smog-motor...

 

[Anlushac11]

8)

heres a further idea I had but I think it would require expensive testing and be a major pain to balance.

Someone has come out with a piggyback EFI n2o injector. Basically you pukk out your stock EFI injector, plug in the n2o Injector, then plug the EFI injector into the n2o injector.

Now if you could measure what the airfuel mixture was in each port and figure this across an entire rpm range at several temperatures you could vary the amount of n2o injected to create a balanced oxidizer and fuel mix. Lot more work than I would want to do but I think it would work. Not something you want to run all the time.

Other idea was to cut the log off so that the inside edge of the log would provide part of a flange. Then you go ahead and modify for EFI, and mount six butterfly valves that are linked and put aircleaners on to prevent dirt from entering.

This would be a EFI setup that looked like a sidedraft Hilborne setup.

 

[Guest]

The D7 head that I have has the flat-top log. It actually sits up higher than the logs on the earlier heads. That actually provides ample room to modify the log for injector bungs to be installed under the log. The problem is that it will interfere with the exhaust. A header would be a must and would also need to be modified to work. A heat shield would most certainly be needed as well. The lower t-body part of a Tempo CFI unit is practically a direct bolt-on for a t-body and includes the TPS. I'm not comfortable with a high pressure fuel line sitting on top of an exhaust manifold though. Vapor lock could be a huge issue as well.

I'm still partial to a 2bbl TBI setup on the log. Grab one for $35 from a junk yard from a Chevy, a $135 Megasquirt, add some sensors and an electric fuel pump with a return and you can easily have EFI for well under $500. Tune with a laptop, PDA or by using the new MegaView interface.

Al

 

[rbohm]

8) al i think you hit on an idea without even realizing it. take three tempo tpi units and us the offenhauser three 1bbl intake, and the mega squirt unit. that would give you even fuel distribution without modding the log for individual injectors, and you dont need to use the progressive linkage. that wouls also give you two backup throttl position sensors.