Ok, I took out my handy dandy IR thermometer with laser sighting and did some testing of each exhaust header in exactly the same place on each tube: 1 inch behind header flange.
Here is the results with my "Individual Cylinder Fuel Trim" set to 1.00:
in degrees F
Temp Cyl Cyl Temp
510 8 ***** 7 520
525 6 *****5 525
525 4 *****3 525
485 2 *****1 490
Front
Hmmm, so going off of the theory of less fuel (to an extent) means hotter exhaust, I trimmed cylinders 1 and 2 to .95 and left the rest at 1.00. The results are as follows:
530 8 ***** 7 530
535 6 ***** 5 535
535 4 ***** 3 535
515 2 *****1 515
Front
Now, referencing back to stock, a .95 trim is up to 8% away from what the factory has as "optimal".
I am going to be doing another round of testing, but what do you think? Am I going down the right path? I assume the cylinders 1 and 2 should be compensated for about 5 degrees because they are the farthest away from the ambient heat source of the engine/sister header tubes.
It looks as if a cylinder trim of .92 or less may be what I need, but wow, that is a big variance.
Ben
Here is the results with my "Individual Cylinder Fuel Trim" set to 1.00:
in degrees F
Temp Cyl Cyl Temp
510 8 ***** 7 520
525 6 *****5 525
525 4 *****3 525
485 2 *****1 490
Front
Hmmm, so going off of the theory of less fuel (to an extent) means hotter exhaust, I trimmed cylinders 1 and 2 to .95 and left the rest at 1.00. The results are as follows:
530 8 ***** 7 530
535 6 ***** 5 535
535 4 ***** 3 535
515 2 *****1 515
Front
Now, referencing back to stock, a .95 trim is up to 8% away from what the factory has as "optimal".
I am going to be doing another round of testing, but what do you think? Am I going down the right path? I assume the cylinders 1 and 2 should be compensated for about 5 degrees because they are the farthest away from the ambient heat source of the engine/sister header tubes.
It looks as if a cylinder trim of .92 or less may be what I need, but wow, that is a big variance.
Ben
Registered User
Your adjusting the trim because you believe 1 and 2 are recieveing less air because of their position compared to the intake direction? Correct? Less air making it into 1 and 2 because the air must reverse directions and therefore the AF is locally rich in 1 and 2 and thats why there cooler.
I take it you are also assuming that 7 and 8 are ok 5 degrees cooler because they are isolated primarys and not paired like 4/6 and 5/3? Did you adjust number 8 because it picked up more temp in the second run. Maybe the first run it was cooler because of the additional EGR surface area? or did you adjust number 8 also? Maybe the Air pump attachemtns are acting as fins cooling 1 and 2, at least on my SLP headers the Air fittings are about 4 inches off and could add significantly to the surface area and it's cooling capacity.
I think you may be over analyzing the situation for a couple of reasons.
a) much larger air space around 1 and 2 to cool it a little faster, maybe 5 degrees isn't a sound assumption.
b) it seems that your IR pyrometer is accurate and gives repeatable results, do you need to set the emmisivity of the material for that to calculate a temperature? I'm not sure how exactly your IR device works. If so is there a minor inconsistancy with the coating thats is skwing those temps because your looking at a radiused ben from the side instead of the outside radius? I know my coating isn't perfectly consitent around the bends. maybe those got more overspray of coating? This may be a little far fetched.
c) if my original statement is correct that your trying to compesate for the geometry the incoming air travels through and that is the reason the front cylinders are underperforming, won't that effect be slightly more pronounced under acceleration ect because air is mass/inertia and will have a greater tendency to pressurize the rear of the intake manifold when the car is moving. It's not a lot of inertia but if what your trying to balance your cylinders AF ratios that exactly you probably have to take that small effect into account which would mean furthur leaning them out.
My main doubt is with your 5 degree assumption, it seems like there is a lot more air available to cool #1 and 2 that could be making the difference.
What a ramble, i hope some of that makes sense. It's hard to type technical stuff without taking forever.
I take it you are also assuming that 7 and 8 are ok 5 degrees cooler because they are isolated primarys and not paired like 4/6 and 5/3? Did you adjust number 8 because it picked up more temp in the second run. Maybe the first run it was cooler because of the additional EGR surface area? or did you adjust number 8 also? Maybe the Air pump attachemtns are acting as fins cooling 1 and 2, at least on my SLP headers the Air fittings are about 4 inches off and could add significantly to the surface area and it's cooling capacity.
I think you may be over analyzing the situation for a couple of reasons.
a) much larger air space around 1 and 2 to cool it a little faster, maybe 5 degrees isn't a sound assumption.
b) it seems that your IR pyrometer is accurate and gives repeatable results, do you need to set the emmisivity of the material for that to calculate a temperature? I'm not sure how exactly your IR device works. If so is there a minor inconsistancy with the coating thats is skwing those temps because your looking at a radiused ben from the side instead of the outside radius? I know my coating isn't perfectly consitent around the bends. maybe those got more overspray of coating? This may be a little far fetched.
c) if my original statement is correct that your trying to compesate for the geometry the incoming air travels through and that is the reason the front cylinders are underperforming, won't that effect be slightly more pronounced under acceleration ect because air is mass/inertia and will have a greater tendency to pressurize the rear of the intake manifold when the car is moving. It's not a lot of inertia but if what your trying to balance your cylinders AF ratios that exactly you probably have to take that small effect into account which would mean furthur leaning them out.
My main doubt is with your 5 degree assumption, it seems like there is a lot more air available to cool #1 and 2 that could be making the difference.
What a ramble, i hope some of that makes sense. It's hard to type technical stuff without taking forever.
Very cool - err hot - ramblings! You have me going a few different directions which is what I wanted.
Hmm I am not sure how the EGR would play a part, but I have that blocked, if that matters. My AIR pump is gone so that is not a factor.
a) Agreed 5 deg. is just an assumption and nothing more.
b) Oh you made me look at the IR thermometer and that is a good thing. It says its range is up to 500 deg F, so who knows how accurate it is just past 500. Emissivity is preset at .95 and I have uncoated headers that have turned dark grey and dull. I took my reading from the topside so no internal/external bend was involved - I wanted that consistent.
c) Looking at both tables for idle and off idle cylinder trims for stock program, it shows something different. In fact at idle the trim extremes are more than at off idle. This is interesting and I will account for this in my program. This is what is weird: stock at idle has the trim at on cyl 2 at 1.08 and cyl 1 at 1.06 while I am currently at .95. Sound odd I am going opposite of what stock indicated I should do.
Hmm, should I rethink this whole test?
Hmm I am not sure how the EGR would play a part, but I have that blocked, if that matters. My AIR pump is gone so that is not a factor.
a) Agreed 5 deg. is just an assumption and nothing more.
b) Oh you made me look at the IR thermometer and that is a good thing. It says its range is up to 500 deg F, so who knows how accurate it is just past 500. Emissivity is preset at .95 and I have uncoated headers that have turned dark grey and dull. I took my reading from the topside so no internal/external bend was involved - I wanted that consistent.
c) Looking at both tables for idle and off idle cylinder trims for stock program, it shows something different. In fact at idle the trim extremes are more than at off idle. This is interesting and I will account for this in my program. This is what is weird: stock at idle has the trim at on cyl 2 at 1.08 and cyl 1 at 1.06 while I am currently at .95. Sound odd I am going opposite of what stock indicated I should do.
Hmm, should I rethink this whole test?
Brad,
I am closed loop mode at the time of testing. BTW, I found this little snippet of information off http://www.sdsefi.com/techegt.htm just as I am posting:
"Many people think that the leaner you go, the higher the EGT gets. This is also incorrect. Peak EGT occurs at stoichiometry- about 15 to 1 for our purposes. If you go richer than 15 to 1, EGT will drop and if you go leaner than 15 to 1 EGT will ALSO drop. It is VERY important to know which side of peak EGT you are on before making adjustments."
So Hmmm, next round I am going to go to 1.05 on cyl 1 and 2 and see what that does to temps. I would assume that the GM engineer's knew better than me what to do. It raining now, so the test road is closed
Will post hopefully tomorrow.
Ben
I am closed loop mode at the time of testing. BTW, I found this little snippet of information off http://www.sdsefi.com/techegt.htm just as I am posting:
"Many people think that the leaner you go, the higher the EGT gets. This is also incorrect. Peak EGT occurs at stoichiometry- about 15 to 1 for our purposes. If you go richer than 15 to 1, EGT will drop and if you go leaner than 15 to 1 EGT will ALSO drop. It is VERY important to know which side of peak EGT you are on before making adjustments."
So Hmmm, next round I am going to go to 1.05 on cyl 1 and 2 and see what that does to temps. I would assume that the GM engineer's knew better than me what to do. It raining now, so the test road is closed
Will post hopefully tomorrow.
Ben
OK, got back on the test bench with this hottie.
For cylinder trims, I went with 1.05 on 1 and 2 with .97 on 7 and 8.
I ran my testing and what do you know I am within 5 degrees in all my headers. 1 and 2 are about 5 deg. cooler and 7,8 are about 3 degrees cooler.
Now this is not scientific (thermometer is not even properly calibrated for these just above 500 deg temps), but it is good enough. As far as I am concerned, my cylinders are trimmed ok.
Thanks all for the input, hope this helped some of you.
Ben
For cylinder trims, I went with 1.05 on 1 and 2 with .97 on 7 and 8.
I ran my testing and what do you know I am within 5 degrees in all my headers. 1 and 2 are about 5 deg. cooler and 7,8 are about 3 degrees cooler.
Now this is not scientific (thermometer is not even properly calibrated for these just above 500 deg temps), but it is good enough. As far as I am concerned, my cylinders are trimmed ok.
Thanks all for the input, hope this helped some of you.
Ben