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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 05-07-2007, 05:51 PM   #1
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Default Tuning by EGT

Just finished up installing a pyrometer. Never had one before, but figured it would help tune ignition when I get to that stage. As a general rule for now, what temps should I expect to see at idle, cruise, and boost? What is too hot?

Or if you could just point me to some good readin', I'd 'preciate it.
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Old 05-07-2007, 05:55 PM   #2
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Generally keep temps above ambient.
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Old 05-07-2007, 06:02 PM   #3
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wait till you hook it into you MS so you can datalog it along with everything else....then you can really use it as a tuning tool.
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Old 05-07-2007, 06:07 PM   #4
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http://sdsefi.com/techegt.htm

Was an interesting read.

I've got EGT in my car and I see 600-800F at idle, cruise is all over the place but I 'd say no higher than 1300-1400. And full boost right around 1600.

Lots of good threads over at m.net on the subject.
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Old 05-07-2007, 06:11 PM   #5
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One thing I have a lot of experience with is pyrometers and EGT gauges. Temperature is meaningless in and of itself because the damn sensors vary so widely. Get five senors from the same manufacturer and none of them will be calibrated the same. The results of this are the crap you'll read on the internet about EGTs. One guy will swear that 950C is right where you should be while others will say 850C, then you'll have a guy who will say, "I was using a wideband and at X.X:1 I was at 900C." All these people will argue with eachother nonstop never realizing the sensors have so much variance.

What you're looking for is behavior rather than the numerical value.
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Old 05-07-2007, 06:22 PM   #6
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Quote:
Originally Posted by jwarriner View Post
One thing I have a lot of experience with is pyrometers and EGT gauges. Temperature is meaningless in and of itself because the damn sensors vary so widely. <snip>
What you're looking for is behavior rather than the numerical value.
I understand that. It's the same thing with the WB and vac gauges, you look for trends more than absolutes. Still, I was looking for just a general guide more than anything. I'm not looking for absolutes.



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Originally Posted by jayc72 View Post
I've got EGT in my car and I see 600-800F at idle, cruise is all over the place but I 'd say no higher than 1300-1400. And full boost right around 1600.
Yeah, that same tech article was posted on 75% of the sites that google brought up for me. Thanks for your data, that was exactly what I was looking for.

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Originally Posted by Braineack View Post
wait till you hook it into you MS so you can datalog it along with everything else....then you can really use it as a tuning tool.
Oh yeah smarty? How do I hook up a thermocouple to the MS?
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Old 05-07-2007, 06:31 PM   #7
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How much of a difference are you seeing between different sensors? 100F? 500F?

Since I'm not datalogging EGT (my ancient link dosen't do that) if it is out by 100F or so I'm not too concerned. What I want to be able to catch is odd behaviour. I'd like to see if my EGT gauge is pinned over 1600 at cruise.

I think the EGT and Wideband used together will help you keep everything that's in the engine, in the engine.
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Old 05-07-2007, 06:32 PM   #8
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cruise and boost matter.. idle, not so much.

you want to use it to tell you your timing isn't retarded too much. lean/rich will come from a wideband, but the EGT can be used as a gut check if your WB looks right and you're running a lot of advance.

Rule of thumb, 1600F is a pretty reasonable "max" for cruise or boost. as mentioned above, there's debate over what it really should be but I use that generically. I wouldn't run 1600 sustained in cruise for hours and hours but for peaks it's ok. sustained should be a few hundred lower.

at cruise it will tell you more if you're too lean than too retarded.
in boost it'll tell you if you're too retarded rather than too lean.
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Old 05-07-2007, 06:34 PM   #9
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Old 05-07-2007, 06:42 PM   #10
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Had a egt gauge on my greddy setup, but unless youll have someone in the car to read and fully understand the gauge, it has no use...
You just don't have enough time to look at the gauge and tune from there.
The reaction time is also not fast...

For the money, buy a wideband...
Don't buy it unles youll have free dyno time...(or a posibility to log the data)
At least thats my $0.02
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Old 05-07-2007, 06:49 PM   #11
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Quote:
Originally Posted by greddymx5 View Post
Had a egt gauge on my greddy setup, but unless youll have someone in the car to read and fully understand the gauge, it has no use...
You just don't have enough time to look at the gauge and tune from there.
The reaction time is also not fast...

For the money, buy a wideband...
Don't buy it unles youll have free dyno time...(or a posibility to log the data)
At least thats my $0.02
Tuning my car I was able to pay attention to what the EGT was going. Long pulls in 4th and 5th gear on a deserted makes it pretty easy to glance down.

Any tool that gives me a hint of what's going on with the engine is worthwhile. Am I going to tune to the ragged edge using the EGT alone? No.

Like y8s said, it's a gut check.
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Old 05-07-2007, 06:53 PM   #12
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Try finding deserted roads here in europe...(let me know if you find some...without speedtraps/camera's)

At least we can go to germany and go top speed... legal...if you can find the room.
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Old 05-07-2007, 06:56 PM   #13
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Originally Posted by greddymx5 View Post
Try finding deserted roads here in europe...(let me know if you find some...without speedtraps/camera's)
I did, when I was in Ireland, in the countryside and a wrong-side-drive BMW 3 series. Damn sure NOT in the city (in the city you have to fold your mirrors in, otherwise someone going the other way will take it off).

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Old 05-07-2007, 07:03 PM   #14
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Quote:
Originally Posted by greddymx5 View Post
Try finding deserted roads here in europe...(let me know if you find some...without speedtraps/camera's)

At least we can go to germany and go top speed... legal...if you can find the room.
I live in Canada, nothing but empty roads!
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Old 05-07-2007, 07:06 PM   #15
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wrong-side-drive BMW 3 series.

Always hated that... When turning the wipers go on....
At least the ign key is in the right place...
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Old 05-07-2007, 07:10 PM   #16
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Quote:
Originally Posted by jayc72 View Post
How much of a difference are you seeing between different sensors? 100F? 500F?

Since I'm not datalogging EGT (my ancient link dosen't do that) if it is out by 100F or so I'm not too concerned. What I want to be able to catch is odd behaviour. I'd like to see if my EGT gauge is pinned over 1600 at cruise.
Good god, I was afraid someone would ask. This work was done around five years ago by myself and a friend, we were trying to build a digital display that would display o2 voltage (narrowband, also pretty useless for tuning), EGT and something else, I want to say IAT. I won't get too much into why it wouldn't work but make sure that whatever probe you get that you read about and understand cold junctions. Some brands require one cold junction, no more, no less, between the probe and the gauge in order to be accurate.

If I recal, some of the probes had 100C differences between eachother. Don't quote me on that. It was enough for us to say, "what the ****?" That's what I do remember.
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Old 05-07-2007, 11:13 PM   #17
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Quote:
Originally Posted by greddymx5 View Post
Had a egt gauge on my greddy setup, but unless youll have someone in the car to read and fully understand the gauge, it has no use...
You just don't have enough time to look at the gauge and tune from there.
The reaction time is also not fast...

the defi lets me play back the gauge readings for the last 3 minutes or some number like that. I can see where it goes on boost.
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Old 05-08-2007, 12:47 AM   #18
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Quote:
Originally Posted by jayc72 View Post
Tuning my car...Long pulls in 4th and 5th gear...gives me a hint of what's going...

I wished I could datalog egt... just one more datapoint to review when tuning.
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