Racing Engine Management

[glenn654]

I'm planning on entering the Race to Ridgeland for my first race, but I have a fuel distribution problem. While testing my engine at full throttle and full mixture at low altitude (1500') cylinders 1,2 and 4 showed EGTs of approx. 1250 with CHTs at or just above 350. While cyl 3 showed an EGT of 1450+ range and CHT of approx 325. This leads me to think it is running LOP.
I have an O-320-D1A, 160HP with an Ellison TBI better than a carb but I still have the distribution problem at high power(65 percent +).

Is the condition of my #3 cyl bad enough to burn a piston if run like this for an hour or more? The last thing I want to do is ruin a cylinder playing.

I have been considering some experimentation at evening out fuel mixture distribution but don't have the needed parts (cost). What I thought of was making inserts to restrict the flow for # 1,2,&4 and hopefully allow #3 to draw a little more. To do this I would get four junk intake tubes and cut a piece about 2" from the lower ends.Then cut the pieces lengthwise removing some metal then welding the cut closed. When inserted into the existing runners fitting snuggly I hope reducing internal diameter enough to improve flow to #3.

What do you think? Does anyone know of any other method to redirect fuel flow?


Glenn Wilkinson

[N62XS]

Glenn:

Call Airflow Performance in Spartanburg, SC. I've found they are very good at these types of issues. Good luck.

[Mike S]

Originally Posted by glenn654

I'm planning on entering the Race to Ridgeland for my first race, but I have a fuel distribution problem. While testing my engine at full throttle and full mixture at low altitude (1500') cylinders 1,2 and 4 showed EGTs of approx. 1250 with CHTs at or just above 350. While cyl 3 showed an EGT of 1450+ range and CHT of approx 325. This leads me to think it is running LOP.
I have an O-320-D1A, 160HP with an Ellison TBI better than a carb but I still have the distribution problem at high power(65 percent +).

The Ellison unit is a TBI-----fuel is introduced at the throttle body, not individual injectors at each cylinder head. This pretty much assures that the mixture going into the plenum is equal for all 4 cyl. Not a guarantee, but pretty good probability.

To me, it sounds like an air leak in the induction leading to #3, causing that one cyl to lean out.

Another cause could be timing issue for that one cyl-----not too likely.

Do you really mean LOP??? Or, just lean??

[osxuser]

Yeah, higher EGT would indicate LEANER, rich of peak, or RICHER lean of peak.

I second the induction leak, but just do a lean test on it. Remember, the VALUE of the EGT isn't as important as how close all three cylinders peak with respect to one another. A few other possibilities are:

Bad probe/Gauge
Installation of the probe CLOSER to the port on one cylinder (measure location).

[DanH]

The Ellison unit is a TBI-----fuel is introduced at the throttle body, not individual injectors at each cylinder head. This pretty much assures that the mixture going into the plenum is equal for all 4 cyl.

Single point fuel pretty much assures unequal mixture. Close enough to run ok, rarely close enough, for example, to peak all cylinders at the same time.

Just polishing the pins old bean <g>

[Mike S]

Dan, he was running at full rich, had high EGT, and Low CHT on one cyl.

Assuming the probes and gauges are accurate, I still see an induction leak as most probable cause.

A TBI at full lean may be subject to distribution unbalance, but full rich????

As I said before---"going into the plenum"-------

[Bob Axsom]

Glenn,

It is OK to throttle back and take it easy on you engine in the Ridgeland race. You can always take care of the problem physically at some later date.

A competitor

[Ron Lee]

Exactly Glenn. Just throttle back...depart after Bob and keep the airspeed down. The thrill is just entering and running the race. No need to go fast if you have concerns.

On my one and only race I did not go full throttle since I had a new engine. Just finding the turn points was thrill enough.

[hydroguy2]

In my street racing days, throttle back was called sandbagging.

Nobody likes a bragger, but everybody likes an underdog. So throttle back for your first race or two, then when you've got your power/cooling issues fixed, go out there and blows some doors....tail feathers off the competition.

[DanH]

<<As I said before---"going into the plenum"------->>

Ah, so you did. Sorry, my bad <g>