Can a cylinder head flow more than the exhaust can handle?

[steve briance]

Funnily enough, I did see an advert for throttle bodies the other day while killing some time on fleabay. It was a very nice looking manifold, bodies, linkages and pipework. It was out of my price range and to add standalone on top is sadly deeper than my pockets. It would be lovely to try it though as the balancing work I've done combined with t.b rev happy nature would be absolutely superb

The tuner wasn't able to say whether it was the intake or exhaust that wasn't breathing well but it was down to an apparent lack of air passing over the maf wire. The wire is as clean as spray cleaner will get it but the output just wasn't providing enough signal to permit injectors to fuel that last little bit... This could of course be a maf fault but its output was varying o.k, its just difficult to find info on what it should be to be in spec.

The exhaust is far from noisy so the perforated wall is doing what it's meant to be. The thing which did seem to suggest that it was slowing down flow too much was that not much seemed to be coming out of the tailpipes. Hardly scientific but, holding hand near to the pipe and revving engine there was barely any force to what was coming out. By comparison, an s2 there was the closest and considering there was an exhaust impellor in the flow, there was definitely more force coming out of that sport back box. Revs were low enough so boost wasnt confusing things.

My back box is currently one pipe through the box, I've a mind that 1 in to an internal Y piece and 2 straight through out would be a way of reducing noise, sound absorbing away from 2 perforated pipes has to be better than 1?

[sam80quattro]

Cant you just cut the pipe off the end of the box and remove the ‘blockage’? Then get it welded back up? Keep us updated though, most in depth post I’ve read in years

[Error404]

If you're worried about it, remove the back box & retest. To be honest I wouldn't trust a 28 year old MAF one bit.
Why didn't he add more fuel in the areas of the table the MAF was reaching & AFR was lean & see if it made more torque? As before, how much power & torque did the car make?

[steve briance]

Sorry Alex, the only thing missing from the process is figures. It is a live mapping process out on the road. It's a shame there won't be any end result figures as we all love to know such things but that will be for another day maybe somewhere else that has facilities.

The 90% of the map that the maf could keep up with was adjusted and some fuelling and ignition amendments were made. The wideband lambda showed that the changes were having an effect on mixture and things were responding well. New values were typed into the last 10% of map but they had no effect on fuel / air ratio at all.

Out of interest, Tony banks have now sent a reply and say that the 'blockage' is a baffle to change direction of the gas and reduce motorway cruising speed drone. This may well be about right.

As it is easy enough to take off, i think the back box will be coming off on Sunday and I will go for a spin...

[piotr]

Reading about how the vehicle was mapped and not enough air flowing through MAF make me think it's mapped by Mark -am I right?

[LHD_Kid]

Mark only road maps?????

[steve briance]

Well, I didn't see a rolling road

[LHD_Kid]

hmmmmm....... I may have to rethink my strategy....

[Error404]

Road mapping is fine if you are not after empirical data and happy with "something about right". Likewise a pure dyno tuned car isn't perfect either, especially in transient conditions that you can;t perfectly replicate on the dyno. Fundamentally in this case, without a detailed knowledge of the ECU in question I don't think road testing/tuning is really very helpful in getting to the bottom of the issue - if indeed there is an issue at all.
The trouble is, you can't actually see if any changes are producing desired/expected results. As far as I can tell, the only sign of a problem is that the engine isn't operating at the commanded AFR, but in my opinion this could just as easily be an issue with calibrating the ECU as it could be a mechanical issue.
If you started with some data to see if the engine was producing what it should, you have a good baseline. Just my 2c

[steve briance]

In fairness to Mark, he has lots of experience with s2 ecu tuning, mine is the first 7a he has had in for this type of work so he is learning almost as much as I am through all this! What I was impressed with was the pre map testing of the car to ensure no faults exist. Very thorough.

Anyway, Today I have ordered some bits and bobs to test the exhaust with...

A cheap anemometer for checking what flow (velocity) is passing through at tail pipe and then with with back box removed at exit from middle box.

Adapters to allow me to screw a 0-15psi pressure gauge into the spare lambda boss in the link pipe straight after the bag of snakes manifold to measure system back pressure from there back, whatever the system ends up being.

I agree with Alex that data is key to working out what if anything is wrong and stabbing in the dark changing things because it sounds the right thing to do could end up expensive. All in all my spend on exhaust testing will be about £17 and then I will be able to say for sure if the back box was blocking things or not and at different rpm.

Specific figures are hard to come by as they vary from car to car and then exhaust system to exhaust system but at least I can see whether things change at least.

One Of the few figures I have seen for a normally aspirated car is 3-3.5psi back pressure. As long as pipe bore isn't too big to slow down velocity, lower back pressure is beneficial. In the n/a world there is a happy medium of pressure and flow but the turbo world seems it is very much the lower the better (if you don't mind ear defenders )

Watch this space!

[Bowie69]

Has it still got a cat?

[piotr]

Mark only road maps?????

Mark have got only 2 wheel dyno so no use for our Quattro-s hance why he is mapping them on the road only
I was very surprised as well as in my slightly OCD world I was thinking it's not how it's should be done but to be honest apart from my mystery boost limit to 1.3 bar he did good job as the car producing 363BHP so from the RS2 setup it's almost where it should be .
the only question you want to ask yourself is are you happy to drive (in my case) 130mph in 50mph zone ?
the road is quiet and I was ok with doing it but I'm sure some people would not feel comfortable to do that.
it wasn't driving to see how quick the car is,it was purely for mapping purpose.

[piotr]

hmmmmm....... I may have to rethink my strategy....

I think that before you will change your mind I would give Mark benefit of doubt.At the end of the day him and DMITRI should be the best options for our engine management system.There is a MRC but I think it will cost you alot more .With Mark you can be sure that if you not happy with the end result he will put your ecu back to what it was and will give you your money back .
decisions decisions

[LHD_Kid]

Having been involved a huge amount with mapping stuff over the years (not me mapping), I know the best way is engine dyno, next best is rolling road, then road mapping... In most cases tweaks need to be made on the road and sometimes for idle...

I will not drive to Talinn, so Dmitri is out
Having had really bad experiences with MRC I would not go there if my life depended on it... can't afford 20 million quid for them to breathe in my general direction either...
Which leaves Mark... it will be going to him as I don't want to go standalone (not yet anyway...) February...

Anyway, lets not pollute this very interesting thread any more, enjoyed the in depth discussion here - interested to see whst the testing throws up!

[prj]

A problem created where there is none.
The first post made me shake my head. You have no business tuning an ICE when you don't even understand the axes on the map and what they represent.
Go and read m232.org some at least, to get an idea.

If that's what your "tuner" said then they should not even be in the business. RUN, and don't look back - find someone decent, fit a standalone they are comfortable with and have it tuned.

Yeah flame me, I don't care.