S4 exhaust modification

4.2 V8 40v Naturally Aspirated - 339bhp
Glen
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Post by Glen » Tue Feb 09, 2010 5:19 pm

I'm going to get the exact same done and looks like its worth it, how do you rate the sound i would like similar or louder than milltek non res (as LPG runs quieter)

how does this compare and were did you get your custom tune done?

thanks for the info

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BlingBling
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Post by BlingBling » Tue Feb 09, 2010 8:35 pm

Sound wise they will cater for your needs. I think it is loud enough. Enough so that the burble can be heard without too many revs, but not to intrusive inside the cabin. I got the map carried out by JD Engineering in Holland and MRC verified that it was a good safe amp. In that it maximised performance without putting the engine at risk.

Glen
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Post by Glen » Fri Feb 12, 2010 8:57 am

well its all done!

I Had down pipes, sports cats, no resonator, and back boxes with same style S4 trim but larger!

Happy with the sound very deep and rumbley at low revs and no to loud when driving plus no droning on motor way :)

Only problem is the engine managment light has come on, I guess it because the down pipes were replaced?
I'm going to call about a custom tune today and hopfully they can put my mind at ease...

Weres best for a custom tune pref near london?

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BlingBling
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Post by BlingBling » Fri Feb 12, 2010 9:09 am

Did you get the main cat sensors relocated? This is probably the cause of your CEL. The difference between the pre & post cat sensors is not enough becasue they are virtually seeing the same temp anf flow rates. They can be cleared with VAGCOM.

Glen
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Post by Glen » Fri Feb 12, 2010 9:12 am

Yes they were placed after cats, should i not worry then if i just get them cleared?

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1781cc
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Post by 1781cc » Fri Feb 12, 2010 11:27 am

I run LPG and I gutted my pre-cats, they can turn the error off when they map it, so no biggie, I think it will say something like: Lambda sensor warmup temperature not optimum - something like that.

Where did you get your LPG done mate? I am having a few issues with mine that I need looking at with fresh eyes.
Image

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BlingBling
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Post by BlingBling » Fri Feb 12, 2010 12:03 pm

As Lee posted depending upon the error it can be switched off. As long as all fuel and airflow levels are within limits then it should not be detrimental. I had a similar error code and it was removed. Get a diagnosis carried out to be sure.

Glen
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Post by Glen » Fri Feb 12, 2010 12:11 pm

Oh good, ive got it booked into Power Engineering in the morning for a health check.

Lee- my system was fitted though green fuel by the last onwer, lve been back to them but cant remember there name ill have a look when i get home for ya.

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Post by nihc » Fri Feb 12, 2010 1:26 pm

Hi,

The first Lambda sensor should go before the Cat, if it's positioned after the Cat the ECU won't be getting the right info' to adjust the fuel trims.

The Lambda sensors perform a very important role in setting the long term fuel trims.

What happens is that the ECU sets the injector timing depending upon the Air flow, etc to get the mixture correct. The first Lambda sensor feeds back what the actual mixture is like and the ECU sets the fuel trim depending upon that.

So, the ECU sets the mixture, the Lambda sensor says the mixture is actually, say, lean by whatever percent and that gets stored as the fuel trim.

The fuel trims are stored in engine measuring block 032, so you can look at them with Vag-Com. A negative value shows that the actual mixture is lean and the ECU will correct how it sets the mixture by increasing the injector time by that percentage.

If the fuel trims are more than +/-15% , the CEL will come on indicating a problem.

There are 4 fuel trims in block 32 -
Trim at idle, bank 1
Trim at partial, bank1
Trim at idle, bank 2
Trim at partial, bank 2

A large negative fuel trim at idle, while the partial trim is OK normally indicates a vacuum leak.

The second Lambda sensor is normally used by the ECU to check emissions.

You can reset the fuel trims by clearing engine fault codes.

Hope that helps understand what may be going on.

Regards, Chris.

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BlingBling
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Post by BlingBling » Fri Feb 12, 2010 3:06 pm

nihc wrote:Hi,

The first Lambda sensor should go before the Cat, if it's positioned after the Cat the ECU won't be getting the right info' to adjust the fuel trims.
Good info. Just to clarify. The pre-cat, first sensor, is not moved when the pre-cats are deleted. The diagnosis sensor, 2nd set pair of sensros, need relocating to the rear of the main cat if the pre-cats have been deleted.

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Post by Glen » Fri Feb 12, 2010 7:32 pm

Yeah the first sensor is in the original place

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Post by Glen » Mon Feb 15, 2010 2:43 pm

got the engine light turned off no probs they also left one sensor unplugged... I had the car on the rolling road while i was there and it only made 270bhp! 100 less than i was expecting! He said it was common for s4's to under power and there was no problems WTF? Cant be right can it?

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BlingBling
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Post by BlingBling » Mon Feb 15, 2010 2:50 pm

Glen wrote:got the engine light turned off no probs they also left one sensor unplugged... I had the car on the rolling road while i was there and it only made 270bhp! 100 less than i was expecting! He said it was common for s4's to under power and there was no problems WTF? Cant be right can it?
What were the exact fault codes?

This is why I stay well clear of RR. Depending upon the type of RR, fudge factors and how the thing is tied down the results can be varied. What fuel were you running during the RR session? LPG or 98 RON Petrol

Has the car been mapped? You will need a new map to make the most of the exhaust changes. If it has not beem mapped then that might explain the low numbers.

Get yourself a G-Tech or Racelogic device and perform some 0-60, 1/4 mile, 0-100 runs. Realworld numbers. If the results are better than stock then you know you've made the right modifications.

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marv
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Post by marv » Mon Feb 15, 2010 6:24 pm

Another couple of things to consider are the adaption and/or throttle body alignment. See the info in this thread: http://rs246.com/index.php?name=PNphpBB ... ic&t=72509 (a lot of it originally posted by nihc).

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Post by Glen » Tue Feb 16, 2010 10:29 am

He cleared the codes before i could have a look, but i have vagcom so will check later.

He did said that one was the lamba probe with no reading (which was unplugged) and the over was the front engine mount which a mechanic told me was common wrong reading???

How can i tell if the engine mount has actually gone?

That thread looks good and i tried the left foot breaking trick and car did seem more aggresive after (traffic and rain permitting...)
But also when i floor it there is a slight delay mainly if in low gear, im thinking this could be the engine mount suprizing as has only done 54K!?

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