Has anyone measured or estimated the temperature loss from the heads down through to the headers.

Having an EGT sensor is one thing - however how is this affected by where it is positioned.

I have been led to believe that if the sensor is after the turbo - then temps are around 50-75 deg lower than the uppipe - which in itself is 50-75 deg lower than the gas leaving the heads. Can anyone elucidate?

Finally - how do heat treatments or wraps affect the temperature loss through the pipework?

Just for calibration - my car is currently running up to 900deg in the uppipe with lagged headers. Cruise is quite high at 750 deg - but again this could be to do with the lagging on the headers.

Rannoch :D

Hi there :) ..... well just remember that the cruise temps "used" to be a tad higher a few weeks ago ;).

Carlos H.

like thats fooking relevant carlos :p

David.. I suppose it depends on coatings on the heads, crowns, oil cooling, d/pipe wrapping / coating etc.. ie its like charge temps.. no two are the same.

Why dont you test on your new spec?

The headers i have, which you may remember, have 3 egt bosses, one near the head, one just after the collect and one just before the turbo.

If you had 3 egt's, then that could answer your questions.

Would be interesting to see the difference.

Steven

Hi David,

I noticed a marked difference when I wrapped my HKS headers. For a couple of months I ran without wrap just for that reason, plus they looked to shiny to cover up :)

When I wrapped them (probe in the headers) the peak temperature went up (can't remember exactly how much but the most marked difference was the RATE at which the temp rises and falls. With the headers wrapped, the temp builds fairly quickly and falls slower and once you get back down to about 600 degrees it falls VERY slowly. With the headers unwrapped the temperature build up was slightly slower but the temperature fell much more drastically.

The max temp I've seen in wrapped headers is just shy of 1000 degrees. Motorway cruise at say 80-90, sees about 750 ish.

Before I bought the headers I had the probe mounted in the downpipe for a while as I didn't fancy faffing with the OEM headers at the time.

Max temps I saw then were in the low 7 hundreds with the downpipe wrapped, but the car was considerably less powerful then.

I usually estimate about 150-200 degrees loss between the headers and the downpipe.

My green car also has the probe in the downpipe and I very rarely hit 700 even at VERY high speeds.

Hope that helps

Rich

[Edited by RICH WILD - 8/22/2003 9:02:45 AM]

[Edited by RICH WILD - 8/22/2003 9:03:24 AM]

I've been thinking the same thing actually...

My car is sporting a 4-1 header from GT Spec (lovely stuff, and a solution that completely gets rid of the uppipe gasket blowing) and I put the EGT probe (defi) at the bung that's welded onto the collector (just before the uppipe).

Here I get 600 degrees celsius on motorway cruising (60-80 mph-ish), and I haven't seen a reading higher than 800 even on the trackdays...the header is unwrapped still, and this has lead to suspicions that I'm not seeing the "truth".

The car is running a safe 11:1 AFR on boost with these readings.

A car I drove recently had wrapped PE headers, with the probe at the cylinder outlet (IIRC), and that one showed ~700 on a cruise, and just above 900 at full bore through the gears - same AF ratio as my car.

EGBP would make alot of difference to the EGT's as well IMHO, different turbos and exhaust setups would surely make alot of difference to the temps you're seeing, right?

/J

Rich...

Slight thought..

EGT is exhaust Gas temp..

Is the exhuust or probe fitting effecting the reading?

David

The turbo definitely makes a difference to EGTs. Swapping from a MD254 to a TMI somethingorother (bigger, anyway :)) brought 15.4:1 cruise temps down from typically 740C to 680C.

Another factor to consider is the length of the probe, it needs to be protruding 1/3 of the diameter into the pipe in order to measure the true gas temp. Any closer to the side of the tube and you can get offsets due to cooler boundary layer gasses.
I suggest measuring the temp at the zone where you have your temperature limiting component. ie if this is the exhaust valves then you want to measure as close to the head as possible, if it is the turbo then measure immediately prior to the turbine.

Measuring the temp in the downpipe IMO is flawed, the work done by the gasses on the turbine has an effect on the gas temp reduction, as the wastegate opens at higher loads then the probe will measure a mixture of 'working' gas and bypassed gas temperatures. This will not bear a linear relationship to the temperature of the gasses prior to the turbo and could be misleading.

Andy

Carlos,


and what cruise temps did you see? At what speed - having lived with the car for a year I would say 750 is around average for legal limit(ish) cruise. :p

Andy,

the probe is in the uppipe and effectively protudes half way across the underneath the uppipe flange just before it enters the turbo. Your comments about positioning it in the D/P are well made.

Rannoch :D