I think I have uneven airflow....

[carrollcw]

I now have about 90 hours on my RV7. Now that I have worked out the major kinks, I am trying to refine it a little. I have noticed that on all my flights, 1/3 CHT's and EGT's run hotter than 2/4 while ROP, however once LOP, 1/3 are my coolest cylinders. When I say hotter, the CHT's are about 20 deg hotter and the EGT's almost 100 deg hotter. When LOP, the CHT's are 60 deg cooler and EGT's 100 deg cooler.

This tells me that 1/3 are getting better airflow, thus run leaner than 2/4.

Furthermore, my GAMI spread is about 1.5 with 1/3 peaking first.

So, what can I do? Right now I have the standard ECI updraft sump that came with my Titan engine. I have heard that the Superior sump is better balanced than the stock Lycoming or ECI. Does anyone have any real world experience with this?

Another option is to heat wrap my 1/3 induction tubes, but I think this would just be a patch for the real problem.

If a new sump is the best choice, has anyone swapped out their superior updraft for cold air induction and would be willing to sell me their old sump???

Thanks!

[Kahuna]

Originally Posted by carrollcw

Furthermore, my GAMI spread is about 1.5 with 1/3 peaking first.

Assuming your 1.5 is 1.5gph difference between first and last peak. If this is the case, fix this first. this will pull the engine cylinders into a closer tolerance in everything.

[DanH]

Originally Posted by Kahuna

Assuming your 1.5 is 1.5gph difference between first and last peak. If this is the case, fix this first. this will pull the engine cylinders into a closer tolerance in everything.

Absolutely correct, but this is an EFii electronic fuel injection system. Clark can't fix it with a simple nozzle restrictor swap like we can with our constant flow systems. That's why he is hoping to correct an intake mass flow imbalance with a different sump.

I for one would be very interested to hear the results of a swap to a Superior updraft sump.

Clark, the trusty Siemens injectors are supposed to be very closely matched. However, since they are simply o-ringed into the intake tubes, and thus easy to move around, it might be informative to swap the injectors side to side. If the temperature pattern changes, you have an injector flow imbalance in addition to (or rather than) a mass flow imbalance.

[Jesse]

I agree with Kahuna. If 1/3 are that far leaner than 2/4, 1/3 will run hotter in both EGT and CHT when rich of peak, and cooler in both EGT and CHT when lean of peak. Tune your injectors, assuming you are injected. Do that before changing anything else. If you have 0.028" nozzles in all injectors, I would put 0.027 in 2/4 and run the test again and see how things run.

[bpattonsoa]

With my experience in working with a SDS equipped Reno racer, Dan is correct, the injectors are not created exactly equal. They are very close so swapping them around may not nake a big difference, but it is worth a try.

There are companies out there that will very accurately flow test the injectors as part of a cleaning process. The one we used gave us before and after flow numbers. Ours had badly fowled due to inactivity over a few months, but the cleaning returned them to specification.

I don't know if 100LL will be a problem over a long time, but EFI users should keep an eye on their EGT numbers and look for long term changes.

[carrollcw]

Originally Posted by DanH

Absolutely correct, but this is an EFii electronic fuel injection system. Clark can't fix it with a simple nozzle restrictor swap like we can with our constant flow systems. That's why he is hoping to correct an intake mass flow imbalance with a different sump.

I for one would be very interested to hear the results of a swap to a Superior updraft sump.

Clark, the trusty Siemens injectors are supposed to be very closely matched. However, since they are simply o-ringed into the intake tubes, and thus easy to move around, it might be informative to swap the injectors side to side. If the temperature pattern changes, you have an injector flow imbalance in addition to (or rather than) a mass flow imbalance.

Dan, you are correct, I cannot do a simple injector swap to fix an imbalance. Furthermore, I have swapped the injectors from 1/3 with 2/4 and the temps remained exactly the same. Thus, the injectors are balanced. This is why I think I have an airflow problem, not injector problem. I have heard the superior sump is more balanced.

[219PB]

Have you contacted Robert at EFII? I am going with a similar setup and would be interested in his take. I am sure that you are not the first to use the stock sump.

[DanH]

Originally Posted by carrollcw

Dan, you are correct, I cannot do a simple injector swap to fix an imbalance. Furthermore, I have swapped the injectors from 1/3 with 2/4 and the temps remained exactly the same. Thus, the injectors are balanced. This is why I think I have an airflow problem, not injector problem.

Excellent. You, me, and Bruce all thinking alike. Puts me in good company

I have heard the superior sump is more balanced.

And I suspect we're going to find out if it is true or not.

[Kahuna]

I saw it was EFII. I assumed that an electronic FI could easily control the amount of fuel dispersed with time open. If this is not the case, then how does one ever control the even distribution of fuel in an EFII setup? Swap sumps until you find the best? Yikes!

[miko38]

What is the difference in cht and egt at wot