Engine/Transmission (1994 - 1998) Pre and Post Turbo temperatures?

[Boldt's Wagon]

The rule of thumb I have seen is 300 degrees difference for pre and post turbo exhaust temperatures. I expect that this is for stock engines, 12 cm HX35, and 20 psi boost. The temperature difference should be higher with higher boost.



Those of you that have installed both pre and post turbo thermocouples, what are the temperature differences you are seeing at 20 psi, 30 psi, and 40 psi boost. Tell us what your turbo is also (12, 14, 16, etc cm).

 

[Cooker]

I can't say at what boost but here are a few observations:



Cruising down the highway the gap is typically closer than 300 degrees, unless you are going up a grade or trying to pass. The post moves very little in these situations and the pre can move several hundred degrees.



The post is much slower reacting so you may spike the pre at 1300 for a couple seconds and the post may never get over 800. I don't even think the 300 degrees difference is accurate for a stock engine, but is more realistic than a BOMBed one.



I'll pay closer attention the next time I'm out and maybe I can post some more informaiton.

 

[Champane Flight]

On

On a friends 95 with both pre and post probes. The temp differences until engine is warm or just running around town can be as high as 600'. After warmup with a load, on a hard pull 250' solid. The pre does react much quicker. An old time diesel mech once told me you could deduct 100' per inch past the turbo, for the turbo temp. Most all pyrometer probes on rigs are post.

 

[BushWakr - RIP]

Running an original WH1C with a 16 housing I found that 10*F for every 1 pound boost was pretty darn close,,,, until I hit about 22psi, then the error got larger at 24psi it was closer to 12*F per lb. boost, at 26psi it was nearly 14*F per lb of boost. That's as far as I took readings.

I agree with the spiking mentioned earlier too, preturbo you'll see near instant response to temp spikes, post turbo you may well be cooling down from your spike, before the gauge even reacts to it. .



Bob.

 

[QRTRHRS]

What they said.

300 degrees is a pretty valid under steady throttle conditions. Anything else is infinetly variable. If you think to follow the numbers, then it becomes a sanity check. If you see a shift over time then you know something has changed.

 

[Forrest]

HX35-12, 32psi, post turbo was 950 to 1000 degrees.



Moved the probe to pre turbo, 1500 degrees.