Competition EGT Spread

[NoSeeUm]

Looking for some feed back from some one who has done some datalogging etc... .



In the exhaust manifold I have a two EGT T/C's installed. One T/C is in the #1 cylinder tube and another T/C is in the #5 & #6 cylinders common tube. I can easily see 300-350F difference in temperature between the #1 and the #5/#6at high loads. The #1 being cooler. At idle and cooled down the temperatures are pretty close to the same between them.



What should I expect for typical cylinder EGT differential?



Thanks in advance;

Jim

 

[DPeltonen]

Sounds like you may need to match (clean) the injectors. Generally speaking (with air cooled engines) you use the highest egt to limit engine operations. Egt variations between cylinders are caused by differences in injector flow, compression, cooling, and spark plug efficiency to name a few.



My personal guess is the injectors. The injectors can become dirty over time and cause flow rate and pattern differences affecting efficiency and temp.

 

[ScottLewis]

First thing I think you should do is to document your readings, then swap the sensors and take more readings, driving the same course and speed. That way you can be certan the temp. differences are actual and not just a variation between pyros.



Dan

 

[COMP461]

I have logged about 25 passes and dyno pulls on my RPM data logger in Project X Diesel , the EGT's are very repeatable and consistent. The spread is around 80 degrees, with 5 being with in 40 degrees. I have used data loggers for many years in racing and dynoing. What you should be looking for is trends and not exact numbers in EGT's, . The K type thermal coupling is very repeatable and either works or it doesn't. I look for one that is in its normal signature and suddenly drops or rises. These can signify a broke component, or unexpected tune change, on that cylinder.



In data log interpretation you recognizes different graph events and know the meaning of each, this can only come from years of knowing what each graph shape equates to what event. This sounds complicated, but it's very simple, and most people catch on quickly.



In racing or any other performance based motorsports arena if you not using a data logger you way behind the power curve of the full potential of you machinery.

 

[NoSeeUm]

Sounds like you may need to match (clean) the injectors.

... ...

My personal guess is the injectors. The injectors can become dirty over time and cause flow rate and pattern differences affecting efficiency and temp.

That thought occured to me, but the injectors are F1 and have less than 10k on them.

First thing I think you should do is to document your readings, then swap the sensors and take more readings, driving the same course and speed. That way you can be certan the temp. differences are actual and not just a variation between pyros.

Yeah, I was going to swap the leads tommorow. From my experience about T/C's (in other applications) are really reliable and almost bullet proof if they work. A shorted T/C will likely show ambient temperature and the point of the short. An opened one just likely won't work or show a really low number (like -428F).

.....

I have logged about 25 passes and dyno pulls on my RPM data logger in Project X Diesel , the EGT's are very repeatable and consistent. The spread is around 80 degrees, with 5 being with in 40 degrees. I have used data loggers for many years in racing and dynoing. What you should be looking for is trends and not exact numbers in EGT's, . The K type thermal coupling is very repeatable and either works or it doesn't. I look for one that is in its normal signature and suddenly drops or rises. These can signify a broke component, or unexpected tune change, on that cylinder.

.....

I have allot of experience with trends etc... I am just not familliar with my truck. I only have the two T/C's and I stuck the #1 cylinder one in as kind of a whim just to see what the other end of the engine was doing. My exhaust header is already looking much like swiss cheese.



From what I understand you are saying is that I should expect a maximum spread of 80F, that is way off from what I am seeing. The part I don't understand is "5 being with in 40 degrees"



Are you saying that cylinders 1 through 5 should be with in 40F and number six is 40F or so above that?

-OR-

Are you saying typically 5 out of the 6 run pretty close to the same EGT and one cylinder gets a little on the high (or low) side?



Is the 80F typically a high or low spread number? Do you remember which cylinder it was?



Thanks much fellas, this is helping me allot;

Jim

 

[ROADWARRIOR]

Cylinder #6 tends to run hotter in a stock engine because it is the furthest from the coolant and air because of where the coolant enters the block and how the stock manifold is machined. My back 3 cylinders run 50 to 100 hotter depending on what I'm doing. I've heard there can be a greater spread while heavy towing up mountains and such when the coolant is getting really warm.



In any case, I'd swap your thermocouples around and see what happens.



Dan

 

[COMP461]

number 5 is the hotest every time on mine, im trying to print screen on my `61 mph pass at the Texas mile. I have a ported head with a ZZ intake manifold, and a great cam , that helps. The 1800 egt are at the end of 27 seconds of 860+ hp run , so dont let that scare you. well the B&W dosent show muck, will work on a better print today , of if any one is intrested , Ill send the link to the RPM software and a few of my data files

the top line is engine rpm, the line that quites is the drive shaft, the truck settled down and pushed the drive shaft forward and misalined the ring and sensor.



the egts are the lines that stick together on the bottom graph the hottest is 1840 and the rest are 1750 and around

 

[johncameron]

spark plug efficiency to name a few.

Is that why the new Ferd 6. 4 throws flames

 

[COMP461]

see if this is better



engine

egts

black rail pressure

red drive pressure

blue boost

green compressure out temp

intake in temp

 

[DPeltonen]

Have you thought about having the injectors matched or shifting the one from the hot cylinder to the coolest? I read about a place in Monroe Washington that works over your injectors to improve efficiency.

 

[COMP461]

I could shift the probes to different locations, but in my experience that will not change the spread. I will guess that it is a fuel, or timing minute change that creates this spread, remember this is less then a 10% and in some case less then 5% form the mean. This is closer then most gas engines.

 

[NoSeeUm]

First thing I think you should do is to document your readings, then swap the sensors and take more readings, driving the same course and speed. That way you can be certan the temp. differences are actual and not just a variation between pyros.



Dan

Swapped EGT leads last night. About the same.



Jim

 

[NoSeeUm]

Have you thought about having the injectors matched or shifting the one from the hot cylinder to the coolest? I read about a place in Monroe Washington that works over your injectors to improve efficiency.

I might look at that. I have a set of M4's getting tested in Texas that I am going to install. I'll need to take a close look at my spread again and go from there.



I am also swapping out a VP44 in the next week or so. Any chance about that?



Still trying to figure out what is normal. :{



Jim

 

[NoSeeUm]

see if this is better

Yes thanks. I am guessing the red EGT trace is your #5. Just making sure, RPM is the scale at the bottom?



Jim

 

[NoSeeUm]

I did some turbo tuning last night also. My peak EGT dropped from the 1400F neighborhood down to about 1250F. With my EGT guage swap it is easier for me to see the spread for some reason. The higher EGT is now on the pillar and it just easier for me to watch it and the road.



Anyways, at 60 MPH my spread is 80-140F. At WOT it can get into the 250-300F range. I just don't have much time to really stare at it, so I could be off by a little. Just hard driving it is in the 200F range.



When I put the exhaust brake on, the EGT's seem to fairly quickly equalize. Which makes sense to me.



Jim