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Author Topic: Audi S4 B5 EGT way too hot !  (Read 1384 times)
Jannik07
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« on: September 06, 2021, 01:38:39 PM »

Good evening,

I own a S4 B5 2.7 Biturbo.
After rebuilding it I have Problems with high EGT and after endless discussions I will try to ask in that forum because I think there are some experts around.

Long Story short: The Engine got rebuilt with new Pistons, rods and N/A Heads. New Valves etc.
Setup:
- complete RS4 Intake
- Hybrid Turbos (750) with K06 Exhaust Housing and 55mm inlet
- 3 inch DP
- Bosch 980 Injectors
- E3L Fuel Pump
- Big Exhaust Manifolds


Car runs great!
But if I go WOT the EGT rises extremly fast. At the end of 4th gear I hit easily 1000°C (1800°F) And thats not what i wanted Grin

1. Its not Software related. I got my file checked 3 times and all of them said its fine.
2. There is enough Fuel. I checked with wideband O2 Sensor and everything operates as it should (afr 11,5 - 12,0)
3. I almost hit the MAF limit. So its somewhere around 600hp. Boost is 29 PSI tapering to 21PSI. Should be easy for the turbos.
4. I cant get "good" timing. Even on almost stock Ignition Map it pulls timing. (with 102 Octane Fuel!)

I think that 4) is my problem. On my other Setup before i could easily go with 20 degree BTDC under load. Now I can hardly get 15.

I also noticed, that my boot got sprinkled with black soot (little points all over the Trunklid).

I will pull the engine again to reduce the Compression Ratio. (at the moment 8.5)

Maybe someone has another Idea to look for.

Thanks in advance!
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Jannik07
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« Reply #1 on: September 06, 2021, 11:57:07 PM »

From my understanding and from what i have read the timing is essentially for EGTs.
And timing pull only occurs from knock. And knocks produce a lot of heat.

Or am I wrong?
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aef
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« Reply #2 on: September 07, 2021, 03:44:40 AM »

timing belt?

me7logger logs?
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Jannik07
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« Reply #3 on: September 07, 2021, 04:38:29 AM »

Timing Belt is new and everything is fine with it. Measurement Block 93 in VCDS says 1° and 3°.
Also the markers on the Camshaft caps are correct.

ME7logger log from 3rd gear is attached. (no EGT visible)
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prj
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« Reply #4 on: September 07, 2021, 05:13:43 AM »

EGT and actual lambda missing from log, so nothing to see here.
Connect external WBO2 to rear o2 input(s) and log the signal alongside.
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Jannik07
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« Reply #5 on: September 07, 2021, 05:23:28 AM »

I will attach a log with rising EGT later on.
But assuming everything is fine. I logged lambda with WBO2 more than 1 time and its exactly doing what requested AFR wants it to do.
When I go down to lambda 0,7 its getting a bit better, but that can't be the solution. And as I said the Boot is sprinkled with Soot...
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Jannik07
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« Reply #6 on: September 11, 2021, 01:18:37 PM »

another log.
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3Wtrs
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« Reply #7 on: September 12, 2021, 03:36:12 AM »

Do you run with catalyst? Is it ok or maybe clogged? Double check this. What exhaust? What brand are the hybrid turbos? Some proven stuff or cheap underground noname turbos? Are you sure the EGT sensors working correct?

Your IAT is also a bit high, after third pull over 60°. Reduce the boost a bit to see what the egt and knock does.

You are running way too rich. You don't need to reduce the compression ratio more. Real 8.5 is low enough.
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prj
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« Reply #8 on: September 12, 2021, 05:44:21 AM »

Its not way too rich if EGT is high.
Nye's question was on point. Do you out know what causes high EGT?
So far there has been no valid answer nor any proper logs with the relevant values.

Thus this thread is a waste of time. Enjoy continuing guessing
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nyet
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« Reply #9 on: September 12, 2021, 11:41:58 AM »

I deleted my question because it was overly mean.

I had a super long post describing EGT causes and mitigation but my browser crashed and in a fit of frustration i didn't feel like another write up.

Instead, since I'm lazy, I found a pretty good summary of EGT. Interestingly, it is from an aviation site; that should come as no surprise, there is a lot less bullshit among aviators than car enthusiasts, especially when it comes to FI

YMMV of course.

https://resources.savvyaviation.com/understanding-cht-and-egt-2/

Again, this isn't 100% perfect but it's close enough (and aligns with my understanding of the topic anyway). prj probably has a few nits he would pick.

In fact, prj, i would appreciate nits because I am thinking of writing an EGT article for the s4 wiki.

Finally, anyone really interested in the topic should actually *look at the EGT model in the FR*. Most of it is there in black and white (albeit in german).
« Last Edit: September 12, 2021, 12:23:25 PM by nyet » Logged

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Jannik07
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« Reply #10 on: September 12, 2021, 02:30:55 PM »

Thanks for your answers. Interesting article! I will read the FR pages too thanks for the hint.

But I think I went through most of the troubleshooting already.
I replaced plugs and coils. I switched complete fuel rail incl. Injectors from a working car and I lowered the compression. Nothing helps.

Hardwarewise everything should be fine. Im running TTH 750 turbos. They are quite big in Germany. A Lot of people are using their stuff. I have also no cats in place. Exhaust is free flowing 3.5 inch. Egt Sensors are working. Before the rebuilt everything Was fine. And its not that common that both Sensors give up at once.

The only thing that does not Work like i want it to is the ignition advancement. The ecu registers knock even on low loads on cyl. 5+6.

Maybe I will collect data with my innovate Tool. But as I said. It Shows exactly the value that is desired. So fuel should Not be the Problem. In a friends S4 with similar setup we can easily reach 25° BTDC ignition advance with no Timing pull. But my engine does not like it.
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BlackT
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« Reply #11 on: September 13, 2021, 12:32:57 AM »

What is wrong here with MAP sensor?  Why these readings are so low?
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Jannik07
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« Reply #12 on: September 13, 2021, 11:52:21 AM »

Its because of 5120 Hack. Multiply the Values by two and you have the right numbers =)
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nyet
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« Reply #13 on: September 13, 2021, 03:49:04 PM »

Its because of 5120 Hack. Multiply the Values by two and you have the right numbers =)

You can fix this in your ECU def.
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ME7.1 tuning guide (READ FIRST)
ECUx Plot
ME7Sum checksum checker/corrrector for ME7.x

Please do not ask me for tunes. I'm here to help people make their own.

Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your experience.
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