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Old 11-05-2012, 12:09 PM   #1
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Default exhaust gas temperature...facts

Hi there,

1st of all, i hope i post in the right subforum

I post here not so often cause i'm from germany and often it's a bit difficult for me to understand this colloquial language in which the most posts are written.
well anyway...

I got some questions about egt's.
I searched around but can't find a good thread, where a lot of facts are posted.

Maybe first some informations about my car.
I still got a 1.6l stock engine from 1993.
I got a lot of gauges in my car, because i want to know, whats going on in my engine.
Some of them you can see here: https://www.youtube.com/watch?v=qTX6mBablZQ
This engine got fired by a DIY turbokit, with Begi S4 exauhst manifold, GT2560R, Begi Downpipe, Subaru WRX STI intercooler, 360ccm injectors, Emagage ultimate and ZT-2 wideband. Also 6th gear and 3.6 torsen axle.
I only use 102octan fuel.
At the end of my exhaust system I installed a Magnaflow-muffler with welded in silencer (diameter only 1,5748inch ~ 40mm).

At the moment, I think that could be the reason for my high egt's.

I measure my EGT's at the collector of the S4 manifold and also 2inch behind the turbo.
If I am cruising at german autobahn at around 4000rpm, -3psi and 14,7afr I measure around 1400 - 1470f before turbo yet.
While max. accelerating till 7100rpm/155mph it increases to 1850f before turbo and 1600f after turbo. While acclerating I measure 11.5afr and around 9psi.
I think all results should be fine apart from my EGT's. They are a bit high, aren't they?

So I would like to know, what egt's you all measured in your miatas (AFR and Boost data would be also nice to know).

To compare that it maybe would also nice to know, where you measure your egt and where you drive when you measure them.
I don't know the exact laws in the states, but I think it is not allowed to drive so fast like here in germany.
So maybe some of you measure some data at the race track?

What do you think is the problem for my high egt's?
I think my ignition should be ok...


Sorry for my bad english

Would be very nice, if this could get an interesting thread!

Regards from Germany!
Basti
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Old 11-05-2012, 12:22 PM   #2
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Sounds like your timing is a little too retarded.
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Old 11-05-2012, 12:27 PM   #3
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Your EGTs are awfully high. On a built 90 1.6 with a 2554 turbo and a 70mm exhaust, I am seeing a peak of 1450*F on a full 4th-5th gear pull at 18psi.
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Old 11-05-2012, 12:38 PM   #4
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1450*F before or after turbo?!
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Old 11-05-2012, 12:42 PM   #5
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After the turbo of course.
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Old 11-05-2012, 12:55 PM   #6
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1700*F is the number I typically hear thrown around as the dangerzone for EGTs in the manifold on aluminum head cars. Like fae was alluding to, what are you running for timing?

You are right that if that silencer on the muffler is causing high back pressure that could cause high EGTs.
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Old 11-05-2012, 12:56 PM   #7
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1400 before the turbo is very high. I was approaching those temps as my cat was clogging. Opening up the exhaust dropped it drastically.
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Old 11-05-2012, 01:11 PM   #8
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Sounds a bit high, yes. I see 1200F (in the manifold) or so at cruise, and 1500-1600 at redline after running it through the gears (200 kpa, AFR around 11:1).

Can you post your timing numbers?

--Ian
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Old 11-05-2012, 02:02 PM   #9
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FWIW A stabilized (operating temp) turbo'd small engine aeronautical "turbine intake temp" is typically 1500-1600f. The problem with using EGT as sole indicator that something is wrong, is that there are many things that can cause higher EGTs: fuel, ign timing, cam timing, exhaust restriction... Anything that creates a trailing combustion as the exhaust valve is open is going to bring the EGT up: too much fuel, ign retard, cam timing.

I saw 1600f peak, single probe in collector ~1" from turbine flange, at 14psi 6500rpm with a .48 AR stage III t3 turbine housing, 3" exhaust which included a resonator, catalytic converter and muffler. I replaced the original ceramic cat with a high flow metal and the EGT didn't change. Timing did change the EGT. So the answer is not always obvious. You might looking over your ign timing and fuel compared to similar set ups.

Last edited by m2cupcar; 11-09-2012 at 09:10 AM.
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Old 11-05-2012, 04:37 PM   #10
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How often do you (anyone) see miatas with burnt valves?

I haven't seen many.

Also, how can a restrictive exhaust increase EGTs?
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Old 11-05-2012, 04:49 PM   #11
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So here you can see my EMU map:


Uploaded with ImageShack.us

You have to know that my basic setup is !! 8 !! degree in front and not like usual 10 degree in front.

So do you think anything looks wrong?

Depending the question why a restrictive exhaust increase EGTs?
This is easy. If the exhaust gas can't flow out freely, it gets damed up and the temperature also rises up.

Regards!
Basti
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Old 11-05-2012, 05:02 PM   #12
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Quote:
Originally Posted by Faeflora View Post
How often do you (anyone) see miatas with burnt valves?

I haven't seen many.
You must be blind. I've seen multiple sets, all of which have been posted on this forum.
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Old 11-06-2012, 12:56 AM   #13
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Quote:
Originally Posted by Mazdaspeed_Miata View Post
At the end of my exhaust system I installed a Magnaflow-muffler with welded in silencer (diameter only 1,5748inch ~ 40mm).
I can't see this helping matters at all. Can you uncork the exhaust and do some testing?
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Old 11-06-2012, 08:46 AM   #14
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Quote:
Originally Posted by Stein View Post
I can't see this helping matters at all. Can you uncork the exhaust and do some testing?
I can't uncork the exhaust easily. I am planing to build a new 3" exhaust system, but this will take some time.

What do you mean with this sentense:
I can't see this helping matters at all.

You think it will help to uncork or more not?

Regards!
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Old 11-06-2012, 09:56 AM   #15
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Sorry, I lapsed into forum-speak. I was referring to the part of your post that I quoted.

I feel the 1.5" exhaust is a hindrance to performance and the excessive back pressure from the restrictive exhaust could be contributing to your excessively high temperatures.
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Old 11-06-2012, 10:11 AM   #16
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Quote:
Originally Posted by Faeflora View Post
How often do you (anyone) see miatas with burnt valves?

I haven't seen many.

Also, how can a restrictive exhaust increase EGTs?
You can't be serious.
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Old 11-06-2012, 11:05 AM   #17
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So does anyone else would like to post his EGT's with AFR, before or after turbo, turbocharger, engine, boost pressure, exhaust system, and so on?

I really would be interested in a lot of results.

Thanks!
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Old 11-08-2012, 09:43 PM   #18
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If only I had an EGT sensor and gauge...
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Old 11-08-2012, 10:02 PM   #19
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EGT probe is supposed to ~1.25" from the head on the header or manifold. Anything longer than that and you don't know the real temp of the gas coming out of the engine.
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Old 11-08-2012, 10:41 PM   #20
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Quote:
Originally Posted by hustler View Post
EGT probe is supposed to ~3" from the head on the header or manifold. Anything longer than that and you don't know the real temp of the gas coming out of the engine.
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