FUELforTHOUGHT

by Dave Koehler
3/8/04

Dave

I have a 468 bbc with 13.1. The heads are 2.19 in. 1.88 exh. and a solid cam is 0.596in. and 0.625 exh. with a dur. of 316 in.-332 exh. Lobe C is 0.014-110c with a single tunnel ram 950 holley alky carb making around 625 horse. This is in a 1982 Prostreet Corvette. I would like to go with alky tunnel ram Enderle fuel injection. My questions are: Would this run well on the street because the car doesn't see much track time, and would it bring the horsepower up some? Would it be worth the money?

Brad in TX

Brad,

Holy Alky!!! I am more than a little amazed that you are running around
town with an alcohol carburetor! I bet that is a real eye opener / closer
for the little old lady sitting behind you at the light.

Fuel injection works great, looks great and it is simple to work with but
was never intended for street use. Did I say it was great? Mechanical fuel injection systems are almost an all or nothing deal. There is no accelerator pump as on your carb, so it is difficult but not impossible to set the barrel valve for a crispy clean, fuel efficient idle and still be able to stomp it without a backfire.

In normal use, the barrel valve, which controls your idle fuel flow and a
little bit of part throttle, is set to run more than a little on the rich
side so that when you whack the pedal there is instant response without a
backfire and boy, does it is respond! This lack of accelerator pump,
however, leads to less than desirable daily driving characteristics and
fuel mileage.

Any injected bracket racer can tell you that it is no big deal to drive
them around the pits but it is not quite the same as driving 10 or 15 miles
around town cruising. I set up an occasional system for "trailer queens"
but they are not concerned about any of the possible negatives.

It can be done and if it is something you really want to do, call the
shop during the week. If I had a hot street machine I would do it but then
I am known for some strange mechanical adventures, plus it certainly would
look bitchin' peeking out of the hood.

I just realized that mileage is probably not on your list of concerns and
hey, ... do some more racing so you will have a legitimate reason to do this. :-)

Have a safe race
Dave Koehler www.koehlerinjection.com

Hi Dave,

We currently run an inline six with a T60-1 turbo. It has an
Electromotive TEC II on Methanol. My question is this: What kind of
EGT's should we expect with this type of set-up? Most mechanical
injection on methanol runs extremely low compared to what we see. The car
seems to run better above 1500 but we currently run no higher than 1450
just to be safe. I have heard of turbo set-ups running as high as 1700!
Is that true? This is a 225ci motor running 6.30s in the 1/8 with the
occasional 1/4 race thrown in the mix.

Tom

Good question. Turbocharged engines will show higher EGT numbers due to
the backed-up exhaust flow and pressure between the exhaust valve and the
turbo.

There is no gospel EGT number for any particular engine. You will have to
depend on your plug readings and E.T. to determine your "baseline" number. If your plugs look right at 1500, the car is truly quicker and you have not sacrificed any pistons to the aluminum gods, then that will be your baseline. If it is not quicker at 1500 degrees and you have no reason to be "on kill", then 1450 degrees is the right choice. Take small steps in tuning.

EGT numbers are only useful in comparing and tuning cylinder to cylinder
variations. It will do you no good to try to match or care about numbers
from another car.

Have a safe race
Dave Koehler www.koehlerinjection.com

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