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Discussion Starter · #1 ·
boost and exhaust temp

Iv'e got the 02 wrx wagon.
put on
18" wheels and michellen sports
Injen wheel well intake
txs chip
up pipe
down pipe and Tanaube exhaust
Cat free
manual boost controller
turbo timer w/ Air/fuel readout
exhaust gas temp gage
psi boost gauge
My question is about boost setting and exhaust temp safety range. At max 4th gear I get 18lbs boost.
My a/f ratio remains rich (around 12) but egt at max will top out at 1650 to 1680 degrees. While normal driving egt is at 1200 to 1400 and 1500 degrees at 3/4 acceleration. I would like to know where the safety limit is when going full out say busting around a mustang on some of the country roads here in Oregon.

kindest regards

David Dyson
 

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sounds like you're OVER the safetly limit. you're boost is too high at 18, it's out of the turbo's efficiency range, and is

1) drastically reducing the life of your TD-04 turbo
2) is creating a LOT more under the hood heat, which is soaking your IC
3) risking breaking up your CAT and sending pieces into the compressor.

your EGTS should'nt ever get about 900 degrees celcius or about 1600 - 1650 F. keep your boost at or below 16.5psi. you'll see no difference in performance (as the turbo isn't pumping more boost at that level, it's just creating making more heat) and you'll be running much safer.

welcome to the club BTW! :) don't forget to browse the new member FAQ thread, and your regional forums!

dR
 

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Discussion Starter · #3 ·
18 psi boost

dr
thank you for the info. Is great to talk to a knowledgable Sooby person. I do not have any cats as all the air system has been replaced including uppipe. What does "soaking up IC" mean?
Do you think a better turbo cooler should be the next step?

David D
 

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"heat soak"

your intercooler has become so hot from the temps you are experiencing under the hood that it is no longer running effeciently. it has become too hot.
 

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I am having problems as well.

I have the vishnu stage 0 for power mods. Boost was set to 15 psi for the track but my EGT's got up to 1700+ at 6000rpm and above. I started shifting at 6k to keep the temps down.

Keep in mind this was on an open track day, I was pushing the car very hard for 30 min or so.

I'm thinking the stock turbo may not be efficient at high rpm and pushes out hot air. Or my tuning is off a little. Someday I will have shiv tune the car himself. :)

I think I may end up getting a new turbo this winter with a full turbo back, maybe VS1.

Any other ideas?

[email protected]
www.achtuning.com
 

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Stock turbo, I think, runs out of its effiecency (sp?) range at around 15-16psi. If you are wanting to run higher boost levels, you will need to purchase a new turbo. You could, if you don't mind the down time, take your turbo off, send it to Forced Performance, have them do the upgrade to it and then you can run higher boost with that turbo. Or you can just get a new one. VF, PE, Garrett, there are tons of tubos out there now for the WRX's.
As for your EGT's...They are way too high! The higher your EGT's, the leaner you are running and you run more of a risk of toasting your engine. Not cool. I run the TXS Stage 4 and my EGT's never get above 1500. That's a hard run, to redline every shift all the way to about 140+ on the track. I know its rich, but, I'd rather have that then a fried engine.
 

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Discussion Starter · #7 ·
akiata 1700 egt at 6000 rpm

Get an Apexi Turbo timer W/ Air-Fuel mixture readout. You should not be running that hot egt at 6000 rpm. I am running 17 psi and only touch 1650 deg. for top of4th gear in a race situation. I am looking for a larger intercooler for heat soak. Or a larger turbo and STI fuel system so I can get more CFM and fuel at a lower PSI. Good luck. I am no expert as I am here for tips also. Dyno Tune seems to be a buzzword for our situation.
Pretty sure you don't want to be at 1700 for mare than 5 or 10 seconds. Diminishing returns and all that.

Hope this was of help
David D
 

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just an inquiry on the subject of egt and lean/rich mixtures. what air/fuel ratio is safe for wide open throttle? 12-1? doesn't the location of the probe for the EGT guage make a difference in the reading ? what if my probe is just before the turbo on the uppipe, what is a safe limit? 1500-1600f
 

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Have you considered getting an STi hood scoop and splitter? Others have found it to reduce EGTs.

Also, moving to "Engine Performance" forum... :)
 

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My car is a STI and it has on a front mount intercooler. My question was what are safe parameters for your air/fuel ratio and EGT readings. Does'nt the location of the EGT probe make a difference in the readings. Sorry for posting in the wrong area but i am NEW here so please bare with me.:confused:
 

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Yes the EGT sesnor should be mounted within 6 inches of the exhaust port for best results. I like to keep EGT's at 1600 or below. The AF ratio should be about 11.2-.11.5:1 at WOT. Ths stock turbo runs VERY hot just to let you know. Cats or no cats it's going to run hotter than a bigger turbo at the same boost pressure.
 

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Thanks for the reply! i have on a pe 1820 turbo with a blitz front mount and a syms equal length header that came with the egt probe mount just before the turbo on the uppipe, would that make a difference in the egt readings. Is that 390 at the wheels!
 

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egt and boost gauges

i've got the apexi el gauges and want to get them installed, questions where is the best place for the egt, now i have the Perrin uppipe and hks down pipe.should it be mounted in the exhaust manafold? as far as the boost it comes with a sensor also where should this be mounted on the hood. thnaks
 

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This is an interesting thread that I sure would like to see continue. Measured EGT will vary quite a bit depending on where your probe is located. Closer to the exhaust port is better.

FWIW, retarded timing will also raise EGTs. The ECU will retard timing rather dramatically under certain conditions, and that can also raise EGTs in addition to lean fuel/air mixture for that power level. I am still unsure exactly all the parameters the ECU uses to make its timing 'decisions'. I wonder if anyone other than a few lab coated ghosts at Subaru do at this point.

I have a TXS stage 4 (VF30/STi injectors/Unichip) running the large TXS TMIC at 17.5psi. I regularly see short term EGTs in the 1650F range - which does have me a little worried - when running WFO. Is that to be expected from a 2.0 liter engine pushing 17.5 psi and ~280HP at the wheels? I don't know. I do know we are in rotary engine EGT range - which is darned hot.

I have observed absolutely no correlation with EGTs with regard to ambient temps, so I am somewhat skeptical of hood scoops that can directly impact EGTs. It might be feasible that the larger scoop can help reduce the temp of the incoming air charge enough that the ECU doesn't 'hear' a knock event [or see excessive intake air temp...?] and will let the timing stay advanced. You'd have to log some data to see if that has any bearing.

Additional fuel will cool the EGTs somewhat, but will also reduce power. A little timing advance may also result in lower EGTs, but may also introduce knock under certain conditions, which will yield the ECU retarding timing and back to high EGTs. I believe that tuning to be a fairly fine science at this stage. At any rate, 1600F is about as high as I'd like to see in a piston engine.

So, what to do? More fuel? More advance? Water or propane injection?
 

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Re: 18 psi boost

David D said:
dr
thank you for the info. Is great to talk to a knowledgable Sooby person. I do not have any cats as all the air system has been replaced including uppipe. What does "soaking up IC" mean?
Do you think a better turbo cooler should be the next step?


David D
the heat "soaking your IC" is the excess heat under the bonnet, warming your intercooler. keeping under hood temps as low as possible means running better boost, b/c you're able to cool down the compressed charge.

i haven't heard of larger scoops lower EGT's, i'm not sure how that could be possible, but i think you confused it with lowering ambiant temps under the hood, reducing IC heatsoak and turbo heatsoak (as a portion of the scoop direct air onto your turbo)

as for running 1650 DegF, i think you need to reevaluate some tuning, as that should not be a regular occurance for a properly tuned engine. remember, you're approaching the temps that MELT aluminum. what is our block made of? exactly.

dR
 

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The location of the EGT probe is said to be best at 3-6 inches away from the cylinder head .........does this mean that you will get a higher reading when it is 3-6 inches as opposed to it being on the uppipe. When it is on the uppipe it is getting the temperature of all four cylinders and when it is 3-6 inches it gets it from one cylinder. Which would give the higher reading? would the readings be significantly different?
 

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bertune said:
Thanks for the reply! i have on a pe 1820 turbo with a blitz front mount and a syms equal length header that came with the egt probe mount just before the turbo on the uppipe, would that make a difference in the egt readings. Is that 390 at the wheels!
No at the crank. 311.5 whp. I have a new car ready to be dyno tested to break my record soon. I think I can get 330 whp out of it. Anyway, with the Maxim Works header, that bung is for the stock EGT. An aftermarket one needs a new bung mounted on the driver's side rear port welded on. Only take a minute and I have the bungs here if you need one in stainless. Bad part is you have to remove manifold to do it.
 

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bertune said:
The location of the EGT probe is said to be best at 3-6 inches away from the cylinder head .........does this mean that you will get a higher reading when it is 3-6 inches as opposed to it being on the uppipe. When it is on the uppipe it is getting the temperature of all four cylinders and when it is 3-6 inches it gets it from one cylinder. Which would give the higher reading? would the readings be significantly different?
The readings are not significantly different from cylinder to cylinder BUT they are different from the port to the uppipe. Best wy with stock manifold is to put it at the y joint. That way you can read of two cylinders yet still be within 6 inches away from the port.
 

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Re: Re: 18 psi boost

dark_rex said:
as for running 1650 DegF, i think you need to reevaluate some tuning, as that should not be a regular occurance for a properly tuned engine. remember, you're approaching the temps that MELT aluminum. what is our block made of? exactly.
It's not quite that simple, but I understand your point. Aluminum alloys melt at a temperature significantly lower than that. More importantly, aluminum loses strength at temperatures far below that. But the aluminum parts (heads, block, pistons, etc.) are protected by its ability to conduct heat to surrounding materials - like the oil and coolant, but only so far before the heat builds faster than it is conducted away.

Another important thing to think about is the inelasticity of aluminum. It's probably one of the contributing reasons why ring lands eventually fail in knock events.

1650F is hot for a piston engine, which is why I am concerned about it in my engine, but just tossing more fuel into the combustion cycle to cool the EGT might not be the best way to go. Maybe it is. It certainly may lower EGTs, but is there a more systematic and potentially more beneficial way to do it?

A little more advance? In conjunction with more fuel? Perhaps needing some additional help - ie. water injection? Propane?
 
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