Supra Forums banner

1 - 20 of 34 Posts

·
Registered
Joined
·
362 Posts
Discussion Starter #1
I am about to fit an EGT gauge and EGT probe. I had planned to put the probe as high as possible on the downpipe because it is much easier to install that way.

A friend of mine however says that putting the probe there is absolutely useless. The temperature readings will vary too much to mean anything.

I am hesitant to put the probe before the turbo since there have been people with broken probes that destroyed turbos and installing it will also be much more complicated. I presume you have to remove the turbo otherwise there will be metal fragments going through the turbo when drilling the hole.

Can anyone with an EGT probe in the downpipe tell me if the temperature readings indeed vary a lot and whether it is of any use there?

Flavio
 
S

·
Guest
Joined
·
0 Posts
Yep, the reading is approximately 150C cooler in the top of the downpipe than in a manifold runner.

It isn't totally useless. It gives you an idea of what the car is doing. Just add 150C to the reading.

We're not supposed to use it to tune the car anyway, it just gives you a feel for whether the car is running lean or not. Of course the right way to tune the A/F is by using a dyno and wideband O2 sensor shoved as far down the exhaust (quicker response) as possible. Actually, they have A/F tuning capability on the road now but I forget the exact method. This would be preferred. I think Kevin Hoare tuned his car this way on the road.
 

·
SF.com Member #0000000023
Joined
·
1,219 Posts
It *IS* useless in the downpipe. I've heard "about a 150 degree difference" over and over again. Unless someone is willing to step foward and say they're the ones who've done it, my understanding is NOBODY has actually tried this and it's a total GUESS. I helped a friend install a probe in the #1 runner, about 2inches away from the head where it belongs. Anyone curious as to the readings? -On even relatively hard pulls he would see temps creep up to *900 CELCIUS* at which point he shuts down....this where the point where you engine parts melt. This was on 92 octane, no a/f computer, Greddy BCC & running ~1.1 bar....he also has a huge FMIC. Although I have not spoken to them directly, I've heard (so maybe it's BS, maybe not) that GForce Engineering actually ADDS FUEL to the stock maps for the generic BPU program.

Let's say it was a 150 degree difference. The reading on the gauge would be so slow that your pistons would probably be exiting your tail pipe by the time it said 750c.

In short, if you're not going to do it right, don't bother doing it at all. An EGT probe in the downpipe will do nothing for you. Tuning off an EGT in your downpipe is just asking for trouble.


-Mike






stoker6 said:
Yep, the reading is approximately 150C cooler in the top of the downpipe than in a manifold runner.

It isn't totally useless. It gives you an idea of what the car is doing. Just add 150C to the reading.

We're not supposed to use it to tune the car anyway, it just gives you a feel for whether the car is running lean or not. Of course the right way to tune the A/F is by using a dyno and wideband O2 sensor shoved as far down the exhaust (quicker response) as possible. Actually, they have A/F tuning capability on the road now but I forget the exact method. This would be preferred. I think Kevin Hoare tuned his car this way on the road.
 

·
I'm ill, not sick
Joined
·
379 Posts
Everytime I read on this topic I get concerned. I have my probe installed in the top of my DP. This was done on the advice of Mark Tozer @ Suprastore.com. It is my understanding he is one of the country's most reliable source for MKIV modification information. I do not want to melt my engine. I love my supra (in some sick man to machine way). I am running only 1.1 bar and my EGT shows temps between 6 and 6.2, even on highway runs. Is it really worth the time to install the probe in the manifold? How long will this take? Don't you have to crank the engine periodically while drilling? For how long. I will do it this winter if it is necessary. I am very fussy when it comes to my supra and do not rig anything. I would appreciate responses from several sources.

thank you.:mad:
 
S

·
Guest
Joined
·
0 Posts
If you really want to get literal, the EGT gauge is useless anywhere. Once again, we are not supposed to use it to tune the car. To accurately monitor EGTs, each runner should be tapped with an independent gauge. Otherwise there is no way to tell which cylinders are running hot. Just because the #6 is *supposed* to run the hottest doesn't it necessarily make it so.

For BPU it is more of PITA then it is worth to install it anywhere in the exaust manifold.
 

·
Registered
Joined
·
192 Posts
Having the EGT in the downpipe can be used for what it is intended... a tuning tool.

If you baseline your car and know what it should be running at, you could put it anywhere you wanted in the car. Any deviation (higher or lower) and you know something is up, and to start looking for the problem before you go WOT again.

But you need to come up with a figure of what temp it should be at where YOU have it mounted.

BTW, 900C is not melting point for engine internals. Most people tune the car to purposefully get to 900C, and some a bit hotter (if you want to tune to the edge)

RPS reccomends tuning to 850 (probably a safe value) with the EGT mounted at the top of the collector before the turbo.
 

·
SF.com Member #0000000023
Joined
·
1,219 Posts
It took us about 4 hours with a GOOD drill. You can actually do most of the drilling with the car off. When the drill is just about ready to penetrate to the other side, the car should be either idling or cranking as this it is being drilled (don't crank you starter for more than 10-15 seconds or you will shorten it's lifespan.


-Mike

ocd said:
Everytime I read on this topic I get concerned. I have my probe installed in the top of my DP. This was done on the advice of Mark Tozer @ Suprastore.com. It is my understanding he is one of the country's most reliable source for MKIV modification information. I do not want to melt my engine. I love my supra (in some sick man to machine way). I am running only 1.1 bar and my EGT shows temps between 6 and 6.2, even on highway runs. Is it really worth the time to install the probe in the manifold? How long will this take? Don't you have to crank the engine periodically while drilling? For how long. I will do it this winter if it is necessary. I am very fussy when it comes to my supra and do not rig anything. I would appreciate responses from several sources.

thank you.:mad:
 

·
SF.com Member #0000000023
Joined
·
1,219 Posts
Ideally yes, but we were probably looking at at additional 8 hours of work. We weren't planning on tuning anywhere near it's limits so we concluded it should be "close enough" in the #1 runner. There should not be a huge variation between temps of the different cylinders.


-Mike

gritsak said:


Shouldnt that be in the #6 runner. that is the hottest one.
 

·
SF.com Member #0000000023
Joined
·
1,219 Posts
If you tune it right on the edge sure. I you want to just trim some fat, a single runner or collector is fine.

-Mike

stoker6 said:
If you really want to get literal, the EGT gauge is useless anywhere. Once again, we are not supposed to use it to tune the car. To accurately monitor EGTs, each runner should be tapped with an independent gauge. Otherwise there is no way to tell which cylinders are running hot. Just because the #6 is *supposed* to run the hottest doesn't it necessarily make it so.

For BPU it is more of PITA then it is worth to install it anywhere in the exaust manifold.
 

·
SF.com Member #0000000023
Joined
·
1,219 Posts
Not exactly true. The further downstream the probe, the slower it will be to respond. The EGT is not only for tuning, int he adjusting a/f ratio sense. It can warn you of things such as detonation and getting a bad tank of gas.

-Mike



ekool said:
Having the EGT in the downpipe can be used for what it is intended... a tuning tool.

If you baseline your car and know what it should be running at, you could put it anywhere you wanted in the car. Any deviation (higher or lower) and you know something is up, and to start looking for the problem before you go WOT again.

But you need to come up with a figure of what temp it should be at where YOU have it mounted.

BTW, 900C is not melting point for engine internals. Most people tune the car to purposefully get to 900C, and some a bit hotter (if you want to tune to the edge)

RPS reccomends tuning to 850 (probably a safe value) with the EGT mounted at the top of the collector before the turbo.
 

·
We has your money!
Joined
·
576 Posts
asdf

I agree with ekool...I have mine mounted at the very top of the dp..next weekend I will have it tuned to see what temperature I should be at when running my af at 11.0:1..it gives you a really good baseline..maybe not for tuning but for when you want to crank up the boost...so if I run my car on a wide band o2 and it says 11.0:1 and I look at my egt and it says say 700 then I know that is the maximum I should go..so at night I can crank up the boost a bit as long as I never go over that point
 
V

·
Guest
Joined
·
0 Posts
WOW. that is nice that you guys actually responded with some opinions or help. People just ussually dont even respond or respond with a stupid comment or some shit talking. Thanks guys.

So is the egt just a little slower in reading or/and does it read a lower temp?
 

·
We has your money!
Joined
·
576 Posts
ad

The closer to the turbo the better if mounting on dp...the farther away it is mounted the less responsive it will be as well as show a more lower temperature
 

·
I'm ill, not sick
Joined
·
379 Posts
All the info is great! Does anyone know at what temp the GReddy EGT probe melts at? Does anyone know if the new GReddy A/F gauge (I believe it's wideband) is a better device than the EGT?

All this "lean" talk makes me leary to boost my engine beyond stock.:mad:
 

·
Banned
Joined
·
1,124 Posts
I have a fjo and am looking at mounting it(looking for more advice on where). This thread sounds like you guys dont think it is needed with a wideband. I am under the impression that it is an indicator of timing etc.....let me know what you guys think. Oh also i am aem fjo 3row its61 with .70/ar if that helps in making an opinion

Anthony
 

·
Registered
Joined
·
2,913 Posts
I have tested back-to-back with the GReddy EGT probe mounted in the center of the collector just under the turbine entrance, and then with it moved to a position in the DP 1" behind the turbine outlet.

With the probe in the collector I would routinely hit 900 C or a little bit more on a pull through 2 or more gears at 28 PSI boost and AFR at 11.5:1. I ran this way for more than 2.5 years, did a compression test, and compression was still 170+ on all cylinders. That means I wasn't melting anything.

THEN I moved the probe to the DP position mentioned above. SAME EXACT PROBE, NO OTHER CHANGES. I can make a pull at 32 PSI boost through 4 or 5 gears at 11.5:1 AFR, and I CANNOT get the EGT higher than 720 C, and usually it won't go above about 680. If I only make a pull through 2 gears, the EGTs won't go much beyond 640. That is PROOF to me that the DP position isn't worth much at all. If you don't understand why this means that the DP position is almost completely useless, post a question here and I'll explain it.

Also, for the 50th time, #6 is NOT the hottest cylinder in the engine. #1 is hottest, and #3 is 2nd hottest. #2 is the coolest, followed by #6. I used to have a $1700 EGT monitoring system with an EGT probe one each header runner, complete with data-logging, peak/hold, and all sorts of shit. I probably did more EGT monitoring and comparison than anyone on the planet. My conclusion was that EGT monitoring was practically worthless. However, I never burn marginal fuel in my car, so if someone were boosting too much on marginal fuel, and the ECU started pulling a lot of timing, then MAYBE it could be picked up if you had built a good enough profile of what your car's EGTs ought to be, AND you are watching very closely.

You can read more about this in the FAQ section of www.widebando2.com

Steve
 

·
Banned
Joined
·
1,124 Posts
steve i pmed you.. I have a cast manifold (turbonetics log style) I bought the fjo fomr you but was wanting to use the egt for timing issues> what do you think of this i wil not even have a gauge just will set up some saftey parameters in the aem. Tell me if you think this is a good idea or not also where would you put it if you did. I never really run race gas just 94 and sometimes only 93 we are talking about group purchasing some race buyt it would be far and few between
 

·
Senior Spooler
Joined
·
1,206 Posts
"Also, for the 50th time, #6 is NOT the hottest cylinder in the engine. #1 is hottest, and #3 is 2nd hottest. #2 is the coolest, followed by #6. I used to have a $1700 EGT monitoring system with an EGT probe one each header runner, complete with data-logging, peak/hold, and all sorts of shit. I probably did more EGT monitoring and comparison than anyone on the planet. My conclusion was that EGT monitoring was practically worthless. However, I never burn marginal fuel in my car, so if someone were boosting too much on marginal fuel, and the ECU started pulling a lot of timing, then MAYBE it could be picked up if you had built a good enough profile of what your car's EGTs ought to be, AND you are watching very closely. "

Steve,
Does this vary car to car? Or should be put it in #1 if we only have one.
thanks,
Tom
 
1 - 20 of 34 Posts
Top