Turbo Causing Detonation??

[pappas]

Ryan,

You ask:

1) Mixture appears to be too lean when the secondary is turned off.

Mixture and timing are 2 separate and distinct items. In order to isolate the cause and effect of CHT, EGT, low power, not enough boost, etc, you have to have a baseline established. I believe your tasks will be much simpler if you get the timing set correctly and locked down. After that is done, start to go through the process outlined in the Aero-injector tuning section until you are satisfied with the results.

If you are trying to adjust 2 or more items at the same time, you will never determine which item you adjusted had the cause and which had the effect.

You won't know if the "symptoms" you see; High CHT, Low CHT, High EGT, low EGT is the result of timing or carburation.
Work them separately and your problems will sort out much easier.

You also ask ;

2) EGT drops when secondary is turned off. 3) CHT rises when secondary is turned off.

This "symptom" is a classic example of an advanced secondary ignition.

A retarded secondary would show up as cooler CHT's and higher EGT's.

Lou Pappas

[Rynoth]

Thanks Lou!

This has been a great discussion for me, I'll do some more testing. In my case, my "chugging" issue comes up only when I turn secondary ignition OFF and run on mags only (which can't be adjusted in terms of timing), and is resolved by enriching the mixture. I was thinking this would be a "smoking gun" for secondary timing but it may be more complicated then that and I'll try a more focused approach.

Regarding the manuals, the Aeroinjector manual doesn't cover ignition timing. The Aerovee Turbo manual does, but only a ground-check or a basic check of in-flight CHT that then says to adjust secondary ignition timing one way or the other and test again. Trial and error. There's no guidance as to what might indicate that secondary ignition is either too-advanced or too-retarded.

[Sonex1517]

Ryan,

When I was flying with the turbo, I had a very similar “chugging” issue. It was the AeroInjector needle adjustment screw moving a tiny bit. Once I peened the threads and re-tuned, it went away for good....

May have nothing to do with your issue, but that was mine.

[scotttro]

Robbie, how did you manage to peen such small threads?

[Bryan Cotton]

I think I did a squeeze with pliers.

[Rynoth]

It was the AeroInjector needle adjustment screw moving a tiny bit. Once I peened the threads and re-tuned, it went away for good....

Robbie, how did you manage to peen such small threads?

I think I did a squeeze with pliers.

This is what I had done as well, with vice grips. I don't have concerns about my aeroinjector, in fact it has served me very well so far (no burps or stutters despite having a gascolator.) I just need to tweak my secondary timing.

[Sonex1517]

I removed the needle from the AeroInjector. I placed the needle on a vise and very, very gently tapped the threads with a hammer. It just slightly flattened the threads.

Once I did that, no more weird rumbling or chugging. It was so intermittent that I actually thought I was imagining it for quite some time.

Ryan, I also had no problem with the AeroInjector - in fact, it was the last thing I considered could cause the problem. So please don’t assume it cannot happen. It can, and I am not alone in experiencing it.

[WannaFly]

I'm curious, what is the sensation (physical, audible) that leads you to believe it's detonation?

The engine is trying to run BACKWARDS!! I think when I first detected detonation it was a noticeable vibration. I was climbing after take off still producing full power/rpm (33" 3000 rpm was what I was use to) so I pulled the throttle out a little and it went smooth. When I got my waste gate fixed did a NOT full power take off and landed half hour later at another ap taxied back for take off and on climb (37" 3100 rpm) out terrible vibration and rpm drop--pulled throttle and it smoothed out came back around and landed. Did some ground tests and over 35" the vibration would kick in and under 35" it would run smooth. As I said above switching off the secondary solved the problem. This will be the 3rd time I've retarded my secondaries--- I had them waaaay advanced

[WannaFly]

Rats... still not resolved. I can turn my coils off and run on the mags and still get detonation..still hunting

[WannaFly]

Since that post I found it TOO LEAN that helped a lot to put a 2.5 needle in. And my coils too advanced that helped some to retard them. till it came back...now i'm up to my eyeballs in it.
Now I have serious power----when I hit 43 map that baby screams!

Anyway.. I can run it on the ground full power (hold the brake!) Then things heat up and what I think is detonation sets in and I pull the power out so it's just slightly doing it then I turn off my mags and then I switch off my coils the the missing/detonation keeps going---that's why I think it's detonation--it keeps happening on either system. Saw CHT 1 heat wayyyy up doing this...

Yesterday I flew in the pattern using just my mags---I ran it hard 43" map and 70mph climb up then crosswind and downwind 155mph by the numbers--did about 6 laps and it always cools down on the landing approach. But then someone got a flat tire on the run way so I left the pattern for another airport and noticed all my egts were running hot at an easy cruise setting---figured it was because I was only running on mags so not a complete burn and the extra was burning on the way out. So everything heated up on the way to the other airport. Did one touch and go and came around for another when the detonation/missing set in on climb out......bummer. Thought it was completely isolated to the coils.

My $18 borescope saw extra stuff on top of the piston 4 thought it might be glowing and igniting not sure. Spark plug is always wet with oil.

So at this point I think I have 2 problem. 1. coils are mis fireing causing the cylinder the heat up leading to 2. detonation

Will run it tonight with budddy watching engine to locate sparking arching. Coils are really bad now at 2500 rpm should be easy to find!