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Old 02-16-2010, 06:32 PM   #1
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Default EGTs, Internal Wastegate, Small Turbine Housing

A while back I had a turbine wheel grenade on me and after some reading I've come to the conclusion that it was most likely sustained boosting that brought about the damage. Specifically from exhaust temps. I've got an EGT gauge, though it only goes to 1600f, the needle will go higher. The gauge always peaked around 1550-1600 and that was on my final tune, around 19* near peak hp @ 15psi.

Just wondering what the thoughts are on my current parts causing the current temps. I'm running a tubular stainless manifold. Turbo is (was) a t3/t4. Compressor 50AR 50trim and the turbine a 48AR Stage 3. The turbine housing is an OE Mercedes stage 1 that was overbored to fit the stage 3 wheel. I'm using the OE Mercedes internal wastegate housing that is about the largest OE IWG housing to come on a car (diesel engine). It's got a 2-1/2" outlet and has a pretty big "mouth" BUT it still sends the bypassed gases from the gate into the wastegate housing and right back at the turbine wheel. 15psi is reached ~4k so the wg is bleeding boost from that point up to 7k. Though it's not tracked I did regularly give it successive boosted runs. Usually full throttle from low rpm to redline in fourth AND running through the gears to redline. Again, EGTs were stabilizing right around 1550-1600f. Thoughts?

Since I'll be bringing over the setup to a new chassis, it won't be a big deal to run an EWG. I've got a 63AR turbine housing and can pick up a t3 flanged v-band adapter for that housing.
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Old 02-16-2010, 07:04 PM   #2
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Originally Posted by m2cupcar View Post
A while back I had a turbine wheel grenade on me and after some reading I've come to the conclusion that it was most likely sustained boosting that brought about the damage. Specifically from exhaust temps. I've got an EGT gauge, though it only goes to 1600f, the needle will go higher. The gauge always peaked around 1550-1600 and that was on my final tune, around 19* near peak hp @ 15psi.

Just wondering what the thoughts are on my current parts causing the current temps. I'm running a tubular stainless manifold. Turbo is (was) a t3/t4. Compressor 50AR 50trim and the turbine a 48AR Stage 3. The turbine housing is an OE Mercedes stage 1 that was overbored to fit the stage 3 wheel. I'm using the OE Mercedes internal wastegate housing that is about the largest OE IWG housing to come on a car (diesel engine). It's got a 2-1/2" outlet and has a pretty big "mouth" BUT it still sends the bypassed gases from the gate into the wastegate housing and right back at the turbine wheel. 15psi is reached ~4k so the wg is bleeding boost from that point up to 7k. Though it's not tracked I did regularly give it successive boosted runs. Usually full throttle from low rpm to redline in fourth AND running through the gears to redline. Again, EGTs were stabilizing right around 1550-1600f. Thoughts?

Since I'll be bringing over the setup to a new chassis, it won't be a big deal to run an EWG. I've got a 63AR turbine housing and can pick up a t3 flanged v-band adapter for that housing.
How and where were you measuring EGTs??? Every turbine wheel has a max inlet temp (TIT) that you cannot exceed without risking/causing permanent damage to the alloy. The specs I've seen run from 1,650 to 1,750 degrees F (aviation turbos, not automotive). However, EGT readings on individual cylinders are generally lower that the TIT temperature (TIT reading is typically taken as close to the exhaust turbine as practicable). If you are trying to prevent overheating your turbo, you need to be measuring TIT. If TIT is too hot, you need a richer mixture which will lower both individual cylinder EGT and TIT (for the sale of simplicity, I'm omitting the option of lowering EGTs by running lean of peak).

Last edited by sn95; 02-17-2010 at 12:11 AM. Reason: corrected TIT specs
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Old 02-16-2010, 09:04 PM   #3
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Header/manifold collector- about 1" from the turbine flange. EGTs were essentially the same as rich as 10.5 as they were at the final tune. I've seen **** of 1600f cited as "OK" in several aeronautical contexts. The prior turbine wheel was believed to be a turbonetics, but that's not positive. And it had excessive tolerance to the housing wall - about 1/8". Not sure how any of that would impact temps either.
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Old 02-16-2010, 10:05 PM   #4
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1600F is pretty hot. A quick search on honda-tech (they've been there done that to most questions) says they aim for 1400F MAX at full load and wot, but I see alot of guys say they are hitting 1600 after 1-5th pulls.
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Old 02-16-2010, 10:15 PM   #5
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Sounds a bit high. I always tried to keep it under 1400 on my old car. I would see 1450 while cruising down the highway though until I tipped into the throttle to richen it up going uphill.

I don't have a gauge on this car..
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Old 02-16-2010, 11:26 PM   #6
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I'm sure the temps aren't a result of the tune. I've been all over the ign and fuel map specifically focused on this, all with negligible change. Given that, I suspect that the IWG is the culprit. It's a relic compared to the newer internal designs. It dumps directly into a wall that reflects exhaust gas right back at the turbine.
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Old 02-17-2010, 12:10 AM   #7
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Originally Posted by m2cupcar View Post
Header/manifold collector- about 1" from the turbine flange. EGTs were essentially the same as rich as 10.5 as they were at the final tune. I've seen **** of 1600f cited as "OK" in several aeronautical contexts. The prior turbine wheel was believed to be a turbonetics, but that's not positive. And it had excessive tolerance to the housing wall - about 1/8". Not sure how any of that would impact temps either.
It depends on the alloy used in the turbine wheel. Some Rajays are rated at 1,650 max, others at 1,750. It may not be safe to assume that an automotive application is rated quite that high. Note that air cooled aircraft engines use fuel for cooling at high power settings (climb & takeoff); full throttle on an aircraft engine enables an extra enrichment circuit. Additionally, unless you've done some testing, you don't know if the **** you are observing are peak, lean of peak or rich of peak. Peak EGT generates the most cylinder pressure (and highest chance of detonation), so conservative aircraft operators run cylinder EGTs in the 100-125 degree rich of peak EGT range which yields lower ****. I've always seen the highest **** on max takeoff power climbouts; throttling back to max continuous power brings **** down.
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Old 02-17-2010, 01:41 AM   #8
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I would suspect your running a bit rich a WOT & unburnt fuel builds up in the turbine/WG housing. Where is the EGT located?
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Old 02-17-2010, 01:58 AM   #9
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Quote:
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I'm sure the temps aren't a result of the tune. I've been all over the ign and fuel map specifically focused on this, all with negligible change. .
Sensor at fault maybe? Ign and fuel trims should show a change in egts
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Old 02-17-2010, 09:35 AM   #10
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Could have been worded better- I went from 15* to 19* up top and and saw a negligible change- maybe down from 1600f to 1550. More fuel did nothing but lose power. I'm not man enough to run more than that up top on a pump gas street tune at 15psi... not right now w/o a back up engine.
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Old 02-17-2010, 09:42 AM   #11
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Quote:
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I would suspect your running a bit rich a WOT & unburnt fuel builds up in the turbine/WG housing. Where is the EGT located?
Only if there is an ignition source between the exhaust valves and turbo to afterburn the fuel!

Peak EGT = hottest

From peak EGT, you can add fuel to run Rich of Peak (ROP) or subtract fuel to
run Lean of Peak (LOP). Exhaust temps will fall in either case until you attain a mixture that is either so rich (ROP) or so lean (LOP) that it will not combust and the engine dies.
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Old 02-17-2010, 09:53 AM   #12
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Originally Posted by m2cupcar View Post
Could have been worded better- I went from 15* to 19* up top and and saw a negligible change- maybe down from 1600f to 1550. More fuel did nothing but lose power. I'm not man enough to run more than that up top on a pump gas street tune at 15psi... not right now w/o a back up engine.
What were your AFRs when you were altering the timing? Unless you are using a fast acting aviation style EGT probe (most automotive probes sold are old style Westach or Alcor slow acting probes) you are not going to get accurate EGT readings unless you hold the engine at a constant load long enough for the probe to temp stabilize.

I'd suggest testing the car on a chassis dyno that can hold the engine at a constant load for as long as desired (e.g., not a Dynojet). Get the engine running at a safe load (60-75% power) and RPM that puts the engine in boost but does not cause the wastegate to start dumping. Monitor AFR and EGT at constant load until both stabilize (at least 1 minute) and then start slowly adding/subtracting fuel in small increments and waiting for the EGT gauge to stabilize after each change. You should be able to find peak EGT this way and also see what richening AFR does to EGT/TIT.
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Old 02-17-2010, 10:17 AM   #13
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Last time on the dynojet I was tuning the top end target boost IGN map and adjusting fuel accordingly for power with regard to knock and EGT. No knock and the usual EGTs during those runs. Final AFR was 11.5 in the newly tuned zones on 93. I was running leaner AFR but with less advance when I rolled in with a rough street tune. There was probably a 50* drop in EGTs by the end.

Agreed - loading dyno is the ideal way to tune (all of it for that matter). So are you saying I should reach peak EGTs at a lower rpm, and boost?
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Old 02-17-2010, 11:05 AM   #14
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I get up to 1200-1300f pulling 1st-5th wot, my bung is welded in 2-3" before the cat.
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Old 02-17-2010, 11:16 AM   #15
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Any speculation on what that would translate to at turbine inlet? How far is your cat from the turbine?
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Old 02-17-2010, 11:24 AM   #16
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Any speculation on what that would translate to at turbine inlet? How far is your cat from the turbine?
Cat is where factory location is, turbo, SG begi DP, then cat. Its all 3" exhaust. I think your temps are normal to be honest because if mine are that hot down there i dont want to imagine the manifold. Heres a video of tuning fuel cells at the dyno i wanted to cry lol, was there for 6 hours still not done tuning...returning this summer to retune

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Old 02-17-2010, 03:10 PM   #17
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Quote:
Originally Posted by m2cupcar View Post
Last time on the dynojet I was tuning the top end target boost IGN map and adjusting fuel accordingly for power with regard to knock and EGT. No knock and the usual EGTs during those runs. Final AFR was 11.5 in the newly tuned zones on 93. I was running leaner AFR but with less advance when I rolled in with a rough street tune. There was probably a 50* drop in EGTs by the end.

Agreed - loading dyno is the ideal way to tune (all of it for that matter). So are you saying I should reach peak EGTs at a lower rpm, and boost?
I'm suggesting a safe approach to validate your EGT gauage is working properly. By starting at a lower power setting w/the wastegate completely shut you can safely globally add/subtract fuel (while at constant load) to determine Peak EGT (and corresponding AFR) and then add fuel from there. Your EGT/TIT gauge should show peak and rich of peak values by doing this. You then have the option of upping boost until the wastegate opens and seeing if you get the same results. If you test methodically like this, you have a better chance of determining if your IG is causing elevated TIT temps or if you simply have a malfunctioning EGT probe/gauge.
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Old 02-17-2010, 04:00 PM   #18
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Post turbine temp is now way to judge your inlet temp. The heat performs a large portion of the work that drive the turbine, and you will see a large temp drop across the turbine as well due to pressure drop.

Turbine inlet temp is critical to longevity, and it sounds like you were pushing it.
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Old 02-17-2010, 05:56 PM   #19
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Most aluminum alloys start to get pretty wobbly around 1650F, so if you are there a lot your head might have a problem anyway.

Most diesel guys are very worried about EGT because they tend to run under load for much longer time frames than we do when towing, even compred to a road course car.The general rule of thumb there is that if you are sustained over 1300 degrees you are basicaly asking for it. You can have peaks that are higer than that, but not for too long.

WI drops EGTs really well. I would simply run a really basic system with pure water. That will often drop temps by about 200F. If you want to run more timing to take advantage of it, so much the better, but you dont have to. And then you can run a more sensible AFR, as the 10.5 is not doing you any favors or making you safer.

Richening the AFRs themselfs is a bad idea. You get cooler combustion temps but you might end up simply burning fuel in the manifold post-cylinder head and spiking temps that way. The increase in timing is simply burning the fuel more completely in the chamber and using it to make TQ, which avoids this to a degree, which is why it cooled things down.
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Old 02-17-2010, 05:58 PM   #20
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Post turbine temp is now way to judge your inlet temp. The heat performs a large portion of the work that drive the turbine, and you will see a large temp drop across the turbine as well due to pressure drop.

Turbine inlet temp is critical to longevity, and it sounds like you were pushing it.

This. Often you will see a 250 degree diff in pre and post turbine temp with a restrictive housing, sometimes even more. If you have 1600 post-turbine, then I gurantee you that you are in heat-death land by quite a bit.
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