OM603 EGT readings

[gsxr]

Hi all,

I got my AutoMeter pryrometer installed last week. I have been keeping an eye on typical temps, and also managed to get some full-load testing done as well. The sensor is screwed into the stock removable fitting at the #1 cylinder, probably 3 or 4 inches from the exhaust valve.

At idle, it's usually 300F or so. Under most normal driving around town, 300-600F is typical. Moderate to heavy acceleration will pop things up to 600-1000F, depending on how long you keep your foot in it. On the freeway, at 65-75mph temps are 600-800, at 75-85mph it's 700-900, and at 85-95mph it's 800-1000. That's on mostly flat roads with lightly rolling hills, no major up- or down-grades. On a long downgrade with no throttle temps can drop under 300F quickly.

And finally, some full load data. At the dragstrip, temps start around 300F at launch, and the EGT climbs to about 1000F at the other end (18 seconds later @ ~80mph). Keeping it floored past the lights to 90mph, it hits about 1250F before I had to back off. Later I found a nice steep mountain to climb at high speed for some real peak temp testing. I was able to keep the car floored, full WOT, for 30-60 seconds at a sustained GPS-indicated speed of 109mph. (!) The EGT climbed up to 1425F and seemed to peak there, I could not get it any higher. Ambient temp was 55F, I do not know if higher ambients would have yielded higher EGT's or not. Sadly this was past the Jet-Hot limit of 1350F for their Sterling coating, so my rear manifold section (cyls 3-6) is no longer shiny silver, it's more of a dull color now. I was expecting that as a possibility though. I'll have to take some photos. The other sections still look shiny. :-)

Top speed testing yielded a GPS-indicated 126mph, a few MPH short of factory spec, but I don't know if there was a headwind or not. That was at 4800rpm I think, so there was definitely room for more speed if the power was available. I tried to take some photos but haven't processed the film yet, don't know if the pix turned out or not (will post later if they do). EGT's on the top speed run were also in the 1400F range.

SO there you have it, folks... those are the numbers from a stock-pumped 603. Next up is deleting the cat and middle muffler, and turning *down* the boost pressure (from 15psi to 12psi or so), to see if EGT's decrease at all. There could be a couple of HP gained due to reduced parasitic losses (wastes power to push exhaust through muffler chambers, create unnecessary charge air pressure, etc) but I'm not expecting much if anything with the stock pump settings. After that it's time to start messing with the pump - but maybe after Casey gets his pumps tweaked successfully!!

(For those of you who haven't followed Casey's intercooler installation on an OM603, the full thread with photos is here.

Very interesting temps............Which number head have you installed?

When your temp instrument showed 300, 600, 1000, 1250, and 1425 degrees internally, did you note what the stock engine temp guage indicated for each of these readings? ...........BB

[Brian Carlton]

Dave,

Are you concerned with temps that are significantly above the generally accepted limit of 1200°F.?

You are significantly above this level.

[gsxr]

BB, I have a #22 head on this car. Engine coolant temps are usually in the 90-95C range, and during the full-load testing I don't recall them ever passing 105C.


BC, I wasn't terribly concerned about the "high" numbers because my injection pump and engine are stock with stock power output. I was theorizing that the high temps may be due to the close proximity between the probe and the exhaust valve. As exhaust moves away from the cylinder it cools, and I don't know how much probe location will affect this. AutoMeter's instructions say to put the probe near the turbocharger, which I did not do.

At least I know I can run 1400F for 30-60 seconds and not grenade the engine. When I attempt to turn up the power levels (with or without intercooling or water injection), I'd prefer to keep levels under 1400F. For acceleration runs it doesn't usually get past 1250-1300F... it took quite a while to actually pass 1400F. Some folks on the MBZ email list think I may have a plugged catalyst, and I'll see what happens when I install a straight pipe in place of the cat.

[Brian Carlton]

Originally Posted by gsxr

BC, I wasn't terribly concerned about the "high" numbers because my injection pump and engine are stock with stock power output. I was theorizing that the high temps may be due to the close proximity between the probe and the exhaust valve. As exhaust moves away from the cylinder it cools, and I don't know how much probe location will affect this. AutoMeter's instructions say to put the probe near the turbocharger, which I did not do.

At least I know I can run 1400F for 30-60 seconds and not grenade the engine.

If your goal is to measure exhaust temperature, then placing the probe as close to the exhaust valve as possible, as you have done, will give you the closest possible indication of the temperature of the exhaust gas as it leaves the cylinder.

Those folks who install the probe downstream, or after the turbo, register temperatures significantly lower. This only serves to give them a false sense of security, IMHO.

The fact that you can run exhaust temps of above 1400 F° without damage to either pistons or head is quite amazing.

[rwthomas1]

From what I have read 1200* to 1250* is the generally accepted conservative EGT limit. I have heard that the Cummins crowd will run 1400* to 1450* so your numbers are not unheard of. I also know a few guys that tow with NA engines and they run right at 1400* without issue. Doubtfull that the EGT temp would be very different between the port you used and the turbo inlet given exhaust gas velocity at those power levels. Its simply moving to quickly to cool off over such a short distance. What will be interesting is if the EGT's will go down when you remove the cat and muffler. Looking forward to the updates! RT

[H2O2]

I suspect MB chose wisely when they tapped the test port at the #1 cyl exhaust valve. If you look at the silly design of the exhaust manifold, it doesn't have equal length runners with a central collecter, so #1 would no doubt get the hottest due to its distance from the outlet stream--i.e. back pressure induced heat. I wish we had a domestic source for exhaust headers, cuz that would get bumped up my mod-priority list, ahead of a Finnish injection pump.

Dave, I bet if you drop the boost pressure back down to stock and weld in a "test pipe" in place of the CAT, your EGTs will drop. $136 on Ebay will get you a basic WI system that would ensure further EGT drops.

[gsxr]

The port on the manifold is designed to attach a pressure gauge, to measure backpressure for the (now-removed) trap oxidizer. If backpressure was over 2 bar (30psi), the trap was plugged and needed replacement. This backs up what the Finns have said about keeping backpressure to no more than twice the boost pressure. I'd like to know what my backpressure is but don't have a gauge to connect and measure it.

I'll report back what happens when I free up the exhaust, although I may not be able to repeat the mounting-climbing 'torture test'. Eventually I would like to install a WI system but there's really no point unless I get my injection pump modified first!

[Hit Man X]

I agree... losing the kitty will lower them for sure. 100° doesn't seem off base at load, it can lower a bit at idle too. If you open the exhaust from the turbo outlet on back it will drop EGTs too as the gas has more room to expand.

Interesting stuff, keep it coming.

[winmutt]

Pulling this one out of the grave. Got my arduino project working finally and found I hit 1250 with my stock IP. Its good to know that 1450 has been seen without issues.

[gsxr]

Originally Posted by winmutt

Pulling this one out of the grave. Got my arduino project working finally and found I hit 1250 with my stock IP. Its good to know that 1450 has been seen without issues.

Keep in mind that the damage may be cumulative... if you hit 1450 once or twice, nothing may happen. But if you hit that daily, eventually there could be a failure. I'd try to avoid those temps.

Originally Posted by gsxr

I'll report back what happens when I free up the exhaust, although I may not be able to repeat the mounting-climbing 'torture test'. Eventually I would like to install a WI system but there's really no point unless I get my injection pump modified first!

Late update, but freeing up the exhaust did very little (if anything) for EGT's. I did try a WI system but it was useless, it did lower IAT's slightly, but did nothing to reduce EGT's. Complete waste of time and $$$, I removed the kit. The WI system did increase power slightly if I sprayed enormous amounts of methanol, but overall it was a bust. The bit power gain came from installing larger pump elements, which of course came with the expected IAT/EGT issues... need larger turbo now.

[winmutt]

This was with 6mm elements and stock turbo right? I am very close to getting my 7.5mm elements and HX30 up and running. Just need to sort the intercooler mounting, which I have already had a test pass on.

[gsxr]

6mm elements yes, started with stock 3.0L KKK turbo then went to stock 3.5L Garrett turbo. The 3.5L turbo helped but it's still too restrictive. HX30 would be much better.

[Don M]

Back in the day, I would as a matter of habit hit 2200 F daily. Short spurts of 10-15 seconds only, but 1650 F for 30 plus seconds. Direct injected engine.

The lowest costs old tricks back then was a free flowing exhaust, larger turbo with larger turbine or at least a larger housing, water inj, and increased timing ( 200 degrees lower EGT with 5 degrees added )

[gsxr]

Don, when you say "increased timing", does that mean advanced or retarded?