PWW

Ok throwing another question out to all you people.
Have been modding my C4 to get ready for some trackday fun (PSS9's ,FVD camberplates front and rear, H&R anti roll bars , poly bushes etc).
Now time to look at letting the car breath a bit better. Have a drop in K&N (to drill or not to drill the box!) and wondered what is the best Exhaust system available? Looking at Fabspeed at present but who stocks this in UK.Also thought about headers but I want to retain the ability to heat the interior.
Thanks again for any imput.

dave morris

Unless you're already a pretty cmpetent driver on the track, I'd recommend you use the money getting some seat time ... DE entry fees etc.

CWay27

Most header companies will give the choice to either go with heat exchanger or not. I have a full B&B headers exhaust and am pleased with the sound and result...... BTW I have no cat!!

Good luck

PWW

I agree having some extra seat time helps but I also want to get the car prep'd as best I can.
I looked at B&B for my daily run around (a Ram SRT-10) but went with the mopar ones as they came with the cat delete pipes also couldnt get a supplier in the UK for them so probably cant get them for the C4 either.Looks like my choice could be limited.

DaveK

I still have fond memories of Christer's GHL. It sounded amazing, and did give him a power increase - even though he wasn't expecting one. He changed his exhaust to something else when he got all the work done to his car - and the GHL was for sale - not sure if he sold it in the end or whether he's still got it - might be worth PM'ing him if he doesn't comment this thread.

But - if you're doing trackdays, aftermarket exhausts are not your friend (including Christers) because you may struggle to pass the noise tests.

Computamedic

I can confirm what Dave has said about noise. I have the Fabspeed dual outlet system on my car (UK supplier is Design 911 BTW) and it registered 108dB at Goodwood last year!!! Even the noisy track days will not let you run if you register more than 105bD - and some are less than 100dB.

The general consensus is that the best performance/sound/noise compromise is a cat bypass with a Cup Pipe and a standard final silencer.

Regards

Dave

SimonExtreme

In the UK, you need to be very careful with what exhaust system you use because of noise limits at trackdays. My car has no cat, a cup pipe and drilled airbox. It measures 105db static (if I am lucky ).

The next thing to consider is that while the cat and silencers make a difference, doing the headers as well might not make that much more difference. The problem you run into is that while you can move more air through a standard engine, you reach the maximum fueling at around 300bhp and once that has happened, there is little point in getting the car to breath better.

Using standard DME and injectors, I haven't seen anybody get more power than can be achieved with filter, cat, cup pipe and chip. To gain more benefit, I believe you need to go to a programmable ECU (Motec or similar) with larger injectors. So, in choosing your exhaust system, you need to consider what level you might tune it to in the future.

If looking for a trackday set up for the UK, maybe you need to think outside the box. For instance Hayward and Scott do a nice looking system which is decatted and only has a single box across the back of the car. It doen't need a g-pipe. They claim good power and noise control and while I haven't seen/heard their Porsche system, I know of other makes of car where H&S have been the best at combining power with silencing.

Editted to say - I realise I have lied when talking about what mods make the most power! My car has achieved the (equal) most power from a 964RS engine with standard DME and injectors and I have 2 other modifications I didn't mention, namely bigger throttle body and hot film conversion.

Christer

Yes, the GHL did make around 20hp and 20tq on JZ Machtech's dyno when I fitted it to my car - they were as surprised as I was. The Dyno graphs have been posted before - just do a search. I keep meaning to put the GHL on Ebay but I never get round to it. I really should though, because Colin at 9M is still storing it (hopefully)!

I am going to try to put it up in the next week and post the link here - if anyone else is interested in the meantime just PM me.

Gary R.

Just remove the secondary and install a J-Pipe bypass. It's relatively inexpensive, drops about 20LB off the rear end, and has a nice sound.. substantially quieter than the Fabspeed dual (I had both). As for the K&N, my race shop told me the only time they find a ton of grit in the throttle bodies is when there is a K&N filter installed and to stay with the OEM paper element. That said, my car has the Fabspeed Cup airbox cover and I love the intake sound when under WOT... some work with a saw and dremel and your stock cover can easily be opened up to get the same result

PWW

Thanks for all the input ..gives me plenty to chew over.
The GHL sounds tempting but I think noise levels would be an issue with that system plus I think it'll be too exspensive for me,(still so much to do and trying to keep to a budget).
I know all about the track levels as I helped a friend Prep and support him with his 924 for the Lodgesports championship this season (which he won on points with several races to spare). This got me hooked on the idea of some track fun for myself.
I already have a cat bypass pipe to install and thought about the idea of a fabspeed type unit with perhaps a euro pre-silencer (muffler) to silence things a bit more instead of the cat bypass pipe.The other option I was considering is a cup pipe instead of the primary but I see on this forum that this causes issues with the secondary breaking down. So all your experiences and thoughts are more than welcome as it will save me time and expense.

TR6

Question: Will the OEM paper filter fit with the fabspeed cup airbox cover? Or do you have to use the K&N with it?

Gary R.

Either one fits fine.

SimonExtreme

Christer

Do you know what noise levels your GHL system produced? In addition, is it single tail pipe?

Thanks

Simon

DaveK

You know when people say "if you have to ask you can't afford it"? This is a bit like that....... But worth every decibel.......

SimonExtreme

Dave

Unfortunately, that doesn't help me know if I will get the car into certain trackdays. I only go for noisy ones but even then, I usually only just scrape in.