Cylinder Head Temperatures, Calling on the Brain Trust and they Win! Options

[ChrisFoley]

Wrt the comments above,
try moving the CHT to another cylinder to see if the high temp is isolated or across the board.

[era vulgaris]

If you try Chris' suggestion to test a different cylinder temp, here is a bit of reference point as far as temps across the cylinders...

#'s 1 and 4 are within a couple degrees of each other. #2 is about 20-30 degrees below 1 and 4. And #3 is about 20-30 degrees above 1 and 4.

So for example:

1) 300
2) 275
3) 325
4) 300

I'll look next time I drive on what the exact numbers/relation between cylinders are on my car, but that's sort of a general ballpark for you to work from.

[Mblizzard]

If you try Chris' suggestion to test a different cylinder temp, here is a bit of reference point as far as temps across the cylinders...

#'s 1 and 4 are within a couple degrees of each other. #2 is about 20-30 degrees below 1 and 4. And #3 is about 20-30 degrees above 1 and 4.

So for example:

1) 300
2) 275
3) 325
4) 300

I'll look next time I drive on what the exact numbers/relation between cylinders are on my car, but that's sort of a general ballpark for you to work from.

I was going to do that this weekend! Will post the information.

[catsltd]

I would rethink timing???
I dont know about 2.0 but cant your timing be checked at like 3000RPM or something like that,to see what advance your running.

My 1.8L ran hot all the time,seems the Porche shop that worked on it,does not know how to set timing on a 914.

After I adjusted the timing,and valves my motor is so quiet.
And no longer runs hot.

At the bottom of the timing adjustment article,a guy tells how to manually check timing.Might be worth trying.
http://www.pelicanparts.com/techarticles/9.../914_timing.htm.

[Jake Raby]

This year's summer blend fuel has changed... I have seen all engines be harder to start when hot, and with the same tuning as last year everything is running hotter... A couple of my personal cars are a good bit hotter, and I have had to throw some changes at the timing and enrichment that have never been needed with these cars before.

Back the timing down 2 degrees and see how i responds.

We have to constantly watch for changes to things like fuel, no one tells us when something changes. I know what settings are supposed to work with the combos, and when a mass of them no longer do, then we know to look elsewhere.

Nothing ever stays the same, the way these engines tune today is wildly different than 2+ years ago.

[DRPHIL914]

This year's summer blend fuel has changed... I have seen all engines be harder to start when hot, and with the same tuning as last year everything is running hotter... A couple of my personal cars are a good bit hotter, and I have had to throw some changes at the timing and enrichment that have never been needed with these cars before.

Back the timing down 2 degrees and see how i responds.

We have to constantly watch for changes to things like fuel, no one tells us when something changes. I know what settings are supposed to work with the combos, and when a mass of them no longer do, then we know to look elsewhere.

Nothing ever stays the same, the way these engines tune today is wildly different than 2+ years ago.

interesting, since ive had to run different octane fuel in my truck to eliminate an issue that came up this spring/early summer - this might explain why- and alson in my 2.0 914 stock d-jet car I had been running 87 no ethanol, but 89 might be a bit better if the fuel blend is different? also back the timing down 2(meaning 26 rather than 28 at 3400rpm?)

[Mblizzard]

This year's summer blend fuel has changed... I have seen all engines be harder to start when hot, and with the same tuning as last year everything is running hotter... A couple of my personal cars are a good bit hotter, and I have had to throw some changes at the timing and enrichment that have never been needed with these cars before.

Back the timing down 2 degrees and see how i responds.

We have to constantly watch for changes to things like fuel, no one tells us when something changes. I know what settings are supposed to work with the combos, and when a mass of them no longer do, then we know to look elsewhere.

Nothing ever stays the same, the way these engines tune today is wildly different than 2+ years ago.

I have backed it out to about 25 but still running hot. Will back out a bit more tonight and test.

I have all of the dizzy options to select
I am thinking about going back to my stock Dizzy instead of the 123 electronic to see if that is an issue. I think the 123 batch fires the injectors instead of firing them in 2 at a time.

[Mblizzard]

On the 123 dizzy I have all of the following options. Currently running the 011.

From looking at these it seems that the advance is all in at about 2700 rpm.



But this seems to correlate with the stock settings from Bosch. Note that you have to double the readings on the graph below.



But I have to think that because it seems to only heat up excessively on highway and hills that it must have too much advance at highway speeds.

If I am thinking about this correctly I think I will have to reduce the total advance back to a level that produces acceptable head temp on highway and depend on the 12 degrees of vac advance to get some low RPM performance.

None of the other setting for the 914 seemed to make a difference in temps.

[Jake Raby]

If it still runs hot with a couple degrees of retard, then try advancing to 30* and see what happens. You can have high CHT associated with high EGT, elevated by retarded timing that doesn't match the engine combo/ fuel/ enrichment.

I'd go to 30* then 32* and watch it closely. This will rule out any chances that the engine wants higher ignition timing.

If the engine responds the same you have to start thinking about enrichment, and even a misconfigured engine combination, or exhaust issue.

Of course missing engine tins, and etc go without saying... And of course remove and clean the cooling fan... That alone can make a 20 degree difference in CHT.

What oil temp are you seeing? Its easier to tune an engine if you can balance both the OT and CHT simultaneously, and often times the OT will give us hints as to what needs to be done with the tuning spectrum to reach an acceptable result faster.

Make sure the 123 isn't running wasted spark, if so your timing light will do no good... It'll show twice the ignition pulse that it should, so you'll actually be running 1/2 the timing that you think that you are.. Been there, done that.

This post has been edited by Jake Raby: Sep 12 2016, 09:05 AM

[Mblizzard]

If it still runs hot with a couple degrees of retard, then try advancing to 30* and see what happens. You can have high CHT associated with high EGT, elevated by retarded timing that doesn't match the engine combo/ fuel/ enrichment.

I'd go to 30* then 32* and watch it closely. This will rule out any chances that the engine wants higher ignition timing.

If the engine responds the same you have to start thinking about enrichment, and even a misconfigured engine combination, or exhaust issue.

Of course missing engine tins, and etc go without saying... And of course remove and clean the cooling fan... That alone can make a 20 degree difference in CHT.

What oil temp are you seeing? Its easier to tune an engine if you can balance both the OT and CHT simultaneously, and often times the OT will give us hints as to what needs to be done with the tuning spectrum to reach an acceptable result faster.

Make sure the 123 isn't running wasted spark, if so your timing light will do no good... It'll show twice the ignition pulse that it should, so you'll actually be running 1/2 the timing that you think that you are.. Been there, done that.

Thanks Jake.

I went a little forward on the time but not as far as 30. Will do that tonight and see what happens.

Engine was recently out and I cleaned everything and verified all tins were in place.

Because I had apparently overheated and crack both heads previously I paid special attention to the internal flaps to be sure that they operated correctly.

Oil Temps seems to run a bit high but on 90+ degree days only see the "M" on the gauge as a high. that is with an external oil cooler.

Running a CFR Evo exhaust and stainless heat exchangers. While not high flow I would not think it would be restrictive.

the 123 does not seem to run a wasted spark approach but I am checking to be sure.

[Jake Raby]

You need an oil temp gauge with numerical values.. I don't trust the stock gauge for anything.

[Eric_Shea]

Just put a 123 on this car...



Has me wondering. I'm going to take the injectors in tomorrow am for testing. No intake leaks were present.

[Jake Raby]

Timing was too high... Guaranteed.

[Mblizzard]

Just put a 123 on this car...


Has me wondering. I'm going to take the injectors in tomorrow am for testing. No intake leaks were present.

Can't say that's an engine mod I am looking for. The slow incremental approach seems valid!

I have new injectors but how would faulty injectors cause that?

[Eric_Shea]

Just put a 123 on this car...


Has me wondering. I'm going to take the injectors in tomorrow am for testing. No intake leaks were present.

Can't say that's an engine mod I am looking for. The slow incremental approach seems valid!

I have new injectors but how would faulty injectors cause that?

Lean condition.

It's just on #3

[Eric_Shea]

Timing was too high... Guaranteed.

Set at 27... (IMG:style_emoticons/default/sad.gif)

I'm hoping that dizzy isn't the culprit.

[Jake Raby]

If the timing was too high it'll look like the engine was lean, and it always happens on #3 first.

The high timing burns too much of the fuel mix, and looks like its lean. I've chased my tail because of that before.

[Mblizzard]

Well it may be premature to do the happy dance but thanks to the guidance from Jake and Eric, I advanced the timing to about 30 degrees. On a short drive ran much cooler. 375 or less most of the time only approached 390 on hill climb that had previously pushed it to 400!

Oh and it seems to have a lot more power!

I think there is a bit more advance to add but after Eric's photo I wanted to be careful. AF never indicated lean conditions so I feel pretty good that it is not running too lean.

Will drive it in the heat of the day tomorrow and see if there are any changes.

[brant]

If it runs hot in the sunlight I'd sure put a different distributor in and run a baseline

[Jake Raby]

Well it may be premature to do the happy dance but thanks to the guidance from Jake and Eric, I advanced the timing to about 30 degrees. On a short drive ran much cooler. 375 or less most of the time only approached 390 on hill climb that had previously pushed it to 400!

Oh and it seems to have a lot more power!

I think there is a bit more advance to add but after Eric's photo I wanted to be careful. AF never indicated lean conditions so I feel pretty good that it is not running too lean.

Will drive it in the heat of the day tomorrow and see if there are any changes.

That tells me that someone set the compression ratio a little low.. Since it ran cooler at 30*, now try 32*. Find a stretch of road up a hill and hold wide open to the top, do this over and over with different timing settings and advance until temps go up, you hear audible pinging, or the car feels slower.

This is how I developed engine combos and tuning for them before I had a dyno. Doing this will tell you everything about the engine.