cat temp = egt?
#4
Registered
iTrader: (1)
Yeah- I'm trying to find this same information for the stock cat, as well. (Or for aftermarket high-flow cats as well). I want to install an EGT gauge to directly measure approximate cat temp, and keep that temperature as a threshold during tuning.
I know that higher temps will decrease cat life, but any guesses as to the normal operating temp, and what temps would melt the cat in a matter of weeks? I'll go for somewhere between the two :-)
I know that higher temps will decrease cat life, but any guesses as to the normal operating temp, and what temps would melt the cat in a matter of weeks? I'll go for somewhere between the two :-)
#9
i just need to know approximately the max temp for the cat, and then thats one of the tuning limits....
#11
#14
RotoRocks Powered
Not happening!
With the turbo (in boost) the EGT temps easily register in the area of 1800. even when I leaned out the cruising AFRs I was seeing 1600+ temps at highway speeds when not in boost.
Tuning to keep your EGT's low, will make your car run at 150 miles per tank, and retarding your ignition will shave quite a bit of power. Not fun at all
But you are welcome to try, and post the results...
With the turbo (in boost) the EGT temps easily register in the area of 1800. even when I leaned out the cruising AFRs I was seeing 1600+ temps at highway speeds when not in boost.
Tuning to keep your EGT's low, will make your car run at 150 miles per tank, and retarding your ignition will shave quite a bit of power. Not fun at all
But you are welcome to try, and post the results...
#15
Boost Junkie
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Bah... I have melted every cat made for the RX8 now. I even got a free lunch from the Steelcat guy after he swore up and down I couldn't melt it. If you want to keep a turbo and a cat... you might want to relocate the cat further down the midpipe.
#17
Banned
iTrader: (3)
A bunch of things:
1) The CAT temp is computed by measuring the resistance across the rear O2 sensor's heater circuit. There is no separate sensor.
2) This computed value (via CANScan) is way to slow to be useful for anything.
3) You can't tune using EGT. EGT is used as a baseline reference after you already know the proper A/F for peak torque. I've already written extensively on the subject, so do a search.
4) Leaning out the A/Fs will increase EGT up to a point before they go down again and that point is way past 16:1.
5) Retarding timing or having unusually slow combustion will also increase EGTs to a point.
Vlad - your temps seem just a tad high (maybe 200°F), but every car is different (see point #3) and I don't know where your sensor is positioned.
Mine is right at the inlet to the turbo, which is 2" from the rear exhaust port and I see 1200° - 1300° in off-boost cruise and 1600° - 1700° under boost at the torque peak.
1) The CAT temp is computed by measuring the resistance across the rear O2 sensor's heater circuit. There is no separate sensor.
2) This computed value (via CANScan) is way to slow to be useful for anything.
3) You can't tune using EGT. EGT is used as a baseline reference after you already know the proper A/F for peak torque. I've already written extensively on the subject, so do a search.
4) Leaning out the A/Fs will increase EGT up to a point before they go down again and that point is way past 16:1.
5) Retarding timing or having unusually slow combustion will also increase EGTs to a point.
Vlad - your temps seem just a tad high (maybe 200°F), but every car is different (see point #3) and I don't know where your sensor is positioned.
Mine is right at the inlet to the turbo, which is 2" from the rear exhaust port and I see 1200° - 1300° in off-boost cruise and 1600° - 1700° under boost at the torque peak.
#18
RotoRocks Powered
Vlad - your temps seem just a tad high (maybe 200°F), but every car is different (see point #3) and I don't know where your sensor is positioned.
Mine is right at the inlet to the turbo, which is 2" from the rear exhaust port and I see 1200° - 1300° in off-boost cruise and 1600° - 1700° under boost at the torque peak.
Mine is right at the inlet to the turbo, which is 2" from the rear exhaust port and I see 1200° - 1300° in off-boost cruise and 1600° - 1700° under boost at the torque peak.
It is positioned at the beginning of the midpipe, right after the flange and before the CAT, or where the CAT was.
During the summer, I had the timing pulled and set at very conservative levels to avoid surprises in a 100F days which may be the cause of high exhaust temps.
I know, that the temps increase as mixture gets leaner. (should not have used the word "even" in the sentence that begins with "Even when I leaned out..."
I was just trying to make a point: on my car the AF is in the area of 14 - 15.7 when cruising (based on the RPM). Tuning down to 10-11:1 AF at cruise, will lower the EGT, but at the same time make the car spit fuel through the tailpipes.
You are correct, Retarding the ignition will not do any good in this case.
Last edited by rotorocks; 11-29-2007 at 11:12 PM.
#20
RotoRocks Powered
I don't know...
different gas, different ambient, different AF, different timing, different intake temps... Too many variables. It's all good as long as there are no pings
The timing is quite aggressive now that the humidity and temps are down.
I haven't taken any screen shots lately, but in general, it is around 30degrees overall, with the area of 5000 - 6500 pulled back by 5-7 degrees.
I can't remember what it is on the pressure based MAP but it is darn near dangerous. I did hear a small ping a few days ago while boost at about 10 PSI and eased off for that specific area, but it is close to scary Power is sooo addictive.
different gas, different ambient, different AF, different timing, different intake temps... Too many variables. It's all good as long as there are no pings
The timing is quite aggressive now that the humidity and temps are down.
I haven't taken any screen shots lately, but in general, it is around 30degrees overall, with the area of 5000 - 6500 pulled back by 5-7 degrees.
I can't remember what it is on the pressure based MAP but it is darn near dangerous. I did hear a small ping a few days ago while boost at about 10 PSI and eased off for that specific area, but it is close to scary Power is sooo addictive.
#23
Banned
iTrader: (3)
I haven't taken any screen shots lately, but in general, it is around 30degrees overall, with the area of 5000 - 6500 pulled back by 5-7 degrees.
I can't remember what it is on the pressure based MAP but it is darn near dangerous. I did hear a small ping a few days ago while boost at about 10 PSI and eased off for that specific area, but it is close to scary Power is sooo addictive.
I can't remember what it is on the pressure based MAP but it is darn near dangerous. I did hear a small ping a few days ago while boost at about 10 PSI and eased off for that specific area, but it is close to scary Power is sooo addictive.
#25
Banned
iTrader: (3)
Nope. Doesn't need to.
The sustained EGT of 1700° or so is only the "softener". The fact that combustion is still occurring inside the CAT is what takes it down.
In any event, there is no CAT made that will sustain +2000°F for any useful amount of time, despite what anyone has sold you.
The sustained EGT of 1700° or so is only the "softener". The fact that combustion is still occurring inside the CAT is what takes it down.
In any event, there is no CAT made that will sustain +2000°F for any useful amount of time, despite what anyone has sold you.