Max EGT? Options

[technicalninja]

The title is the question.

I know what to look for with water-cooled stuff.

I have no experience with air-cooled stuff yet...

What say you?

Is there a normal range?

A never exceed number?

Anyone ever use 4 thermocouples?

Was there any noticeable difference (#3 is of concern to me)?


Thoughts, tips, any data would be greatly appreciated!

[technicalninja]

No direct experience with Porsche but I agree that EGT would be the best method if you are trying to balance combustion in each cylinder. Maybe you could get close just by thermo imaging each exhaust runner without the need to actually mount thermocouples in each runner.

Also agree that 1.5 - 2” below cylinder is about right. More important is to make them all the same

There really is no right number for temp, it will always be moving and depends on thermo couple location and engine state. Maybe you could see delta between cylinders and tune accordingly.

Balancing is done in aircraft by changing out injection nozzles restrictors. They can be had in .5 gph increments. Even then you are not looking at absolute temperature values, you are looking at which cylinder peaks first as you lean at a set power setting. First to peak is the leanest cylinder.

Back in the day, It was common practice to tune go cart race engines on the fly using EGT and a driver adjustable mixture knob.

Chris, were you running 4 sensors and if so could you see any delta?

Another juicy post!
Thanks!

I can change "nozzles" on the fly, in increments so much smaller than .5GPH via a keyboard per injector. I can also alter injection "timing" on some units.

I can do the same with ignition timing on individual cylinders.

I'm hunting the "delta". I thought that was the only way to truly tune individual cylinders.

I'd love to have 4 WBs and 4 thermocouples for truly accurate tuning.
I think you need BOTH AFR and EGT to see the whole picture.

All this crap is for initial tuning only guys.

I want to design/build a plenum-based intake for the T4 and will need "the biggest picture" during POC (proof of concept) phase. POC also stands for "Piece of Crap". They can be one and the same for some projects...

Another question that popped up for me is:
Has anyone installed CHT thermocouples on all 4 plugs and what was the delta between them all?

I BELIEVE that cylinder # 3 runs hotter and is the most critical in the engine but...
I've never tested this myself!

I believe because EVERYONE else does.

What's the difference?
Is it 5 degrees or 40?
5 doesn't bug me.
40 does!
40 would make me want to try different things electronically to reduce the delta.

Injector pulse length, injector timing and ignition timing are the only easily applied adjustments IMO.

[VaccaRabite]

Another question that popped up for me is:
Has anyone installed CHT thermocouples on all 4 plugs and what was the delta between them all?

I BELIEVE that cylinder # 3 runs hotter and is the most critical in the engine but...
I've never tested this myself!

I believe because EVERYONE else does.

What's the difference?
Is it 5 degrees or 40?
5 doesn't bug me.
40 does!
40 would make me want to try different things electronically to reduce the delta.

Injector pulse length, injector timing and ignition timing are the only easily applied adjustments IMO.

@technicalninja
I did that BRIEFLY on my old 2056 while it was carbed. I think I was using the same unit Chris was using. There was a group buy for them back in the day. I don't *think* I put it in when I was doing the Microsquirt conversion. I know from 2017 -2023 that engine ran only with the #3 lead.

It did confirm that #3 was the hottest by about 30 degrees - for my engine at that time. Be it tune (likely) or cooling air leaks (for sure) there was a marked change across the cylinders. That was 30 degrees delta from hottest to coldest. Cylinders were (from coldest to hottest) 2, 1&4, then 3. 1&4 ran pretty close to each other.

When I changed over to Microsquirt I went back to a Dakota Digital CHT on only cylinder 3. When I got my new engine last spring I did not even work the other cylinder heads for leads - only kept cyl 3.

If you want the 4 way unit, PM me and I'm sure we could work something out. I'm certainly not going to use it again and its just taking up space in my shop. Its back in its original box, waiting for me to get off my ass and list things for sale.

Zach