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Exhaust what would you do?

 
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peebles24  



Joined: 27 Jul 2007
Posts: 43
Location: Terre Haute, IN

PostPosted: Wed Sep 19, 2007 11:21 am    Post subject: Exhaust what would you do? Reply with quote

I will be ordering a new exhaust this weekend I don't know what I should do. My current exhaust has a leak at where the down pipe is attached I do believe.

My choices that I can find in the performance products magazine are

Cat converter: 904977 $236.95
Dansk cat back: 904894 $199.95
Bursch header: 908173 $254.95
Flow tube Bursch: ????? $?????
Bursch cat back:904923 $289.95

and a new O2

I can mix and match some of this what do you think I should get. I may do some head work over the winter such as a gasket match and bowl smoothing. I'll also grind the valves and replace the seals and try to find a decent cam.

Would I see any major gain by going with the bursch system header on back after I do some head work or would the cat and Dansk stuff be just as good for power.

Also I have no Emission check in Indiana so dropping the cat is no problem what-so-ever.

I would appreciate your input very much. Yes I have searched and found some info on headers and that there is not much gain to be had with just an exhaust. However would the head work be made any better by a certain exhaust system. I am trying to look to the future.

Thank You,
Chad P.
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1981 924 Weissach, progressive rate coils, Dansk Polished S/S exhaust, free flow Cat, K&N filter

1991 Toyota FJ80
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ideola  



Joined: 01 Oct 2004
Posts: 15451
Location: Woodstock IL

PostPosted: Wed Sep 19, 2007 10:36 pm    Post subject: Reply with quote

Chad, if you were to go with a Eurorace big valve head and a dual carb setup and maybe some high compression pistons, the headers might makes some sense. However, for a stock setup, in many people's opinion (mine included) headers probably aren't warranted.

I have the Dansk setup on my 81 NA. It is a very nice system, looks great and sounds good. Hard to beat for the price unless you can find NOS setup on eBay.

If you're looking for something quick, easy, and inexpensive to improve the response of the car, try the big bore Audi throttle body upgrade. It probably doesn't add any power, but in terms of drivability and throttle response, it is well worth it. Again, I have one on my 81 NA, and love it.
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition
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peebles24  



Joined: 27 Jul 2007
Posts: 43
Location: Terre Haute, IN

PostPosted: Thu Sep 20, 2007 1:24 am    Post subject: Reply with quote

ideola you are saying that even if I port and polish the heads and put in a bigger bump stick I won't see any real gain from the header? If that is the case I see no reason to chance the problems some people have had with headers. I don't know how much you can shave a head before you run into problems, but I thought about this as well to gain a little compression. A friend of mine I used to work for has a auto shop with a full machine shop.
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1981 924 Weissach, progressive rate coils, Dansk Polished S/S exhaust, free flow Cat, K&N filter

1991 Toyota FJ80
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ideola  



Joined: 01 Oct 2004
Posts: 15451
Location: Woodstock IL

PostPosted: Thu Sep 20, 2007 1:35 am    Post subject: Reply with quote

Simply porting the head gives little gains. There are threads galore on this topic, and an authoritative article in the tech section. The only reliable and documented method seems to be going with the Eurorace big valve head, which may be more expense than you want.

Also, the conventional wisdom is that shaving the head to gain CR is a bad idea since it will throw off the timing. Unless you want to recurve your ignition dizzy, from what I understand, that is not a good approach either.

Getting more grunt from these motors is NOT easy OR cheap. You can do it, but you have to address it as an entire system. Big valve head, dual carb setup, stroker with high compression pistons. Your total cost there would be in the neighborhood of $5K.
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88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition
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Chrenan  



Joined: 15 Jan 2003
Posts: 3899
Location: Canada

PostPosted: Thu Sep 20, 2007 1:41 am    Post subject: Reply with quote

Ideola speaks the truth. I wouldn't bother shaving the head or block to gain compression if you have a North American market 924, just get the higher compression Euro market pistons and be done with it, instant 9.3:1 compression, no messing around. If you want to go higher, you have to go with custom pistons, and I'd also start thinking about EFI if you are going to start getting into higher compression than offered from the factory.
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1987 951 - M193 Version for Japan
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peebles24  



Joined: 27 Jul 2007
Posts: 43
Location: Terre Haute, IN

PostPosted: Thu Sep 20, 2007 1:48 am    Post subject: Reply with quote

Go stock is the authoritative answer. 5K not happening. I'm used to being around small blocks. Raise the compression a little and receive a gain, port the head a little receive a gain, open the exhaust and receive a good gain. Good thing I like the performance of the car the way it is, I was just going to get a little extra (15-20hp) if it was fairly easy (pull and port the head, put on header, put in cam).

So I guess I will be saving the 100 bucks and going with a new cat and the Dansk system.

Also is performance products the best place to be buying these items?

Thank You,
Chad P.
_________________
1981 924 Weissach, progressive rate coils, Dansk Polished S/S exhaust, free flow Cat, K&N filter

1991 Toyota FJ80
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ideola  



Joined: 01 Oct 2004
Posts: 15451
Location: Woodstock IL

PostPosted: Thu Sep 20, 2007 1:57 am    Post subject: Reply with quote

I think that's a wise approach. The other thing to do would be to focus on typical tuning techniques, just to make sure you are getting 100% of the HP available: chase down and correct vacuum leaks (do this first), good plugs, wires, distributor rotor & cap, fine tune the timing, new fuel filter, new injectors, run techron periodically, new air filter, and do the Audi TB conversion. Then address the suspension to make sure you get all the handling the car can offer. The KYB shocks and strut inserts are a great value, IMO, for a stock, street-driven car. Good set of hi-po all season tires. You'll have a great running car that will be a joy to drive. The nice thing about this type of approach is that you can do it incrementally. Major HP gains require an all-at-once approach.
_________________
88 924S SE | 82 931 Holbert | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 78 D-Prod Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition
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peebles24  



Joined: 27 Jul 2007
Posts: 43
Location: Terre Haute, IN

PostPosted: Thu Sep 20, 2007 2:10 am    Post subject: Reply with quote

I have a friend who works at KYB and can get me quite a good deal on the adjustable shocks. He can only get 8 shocks a year though so I may have to wait till next year.

I am making a trip down to the local 1/8th mile drag strip Friday the 28th. I have a bet with a friend of mine that I can run under 10.99. The bet is only for a beer, if it was for more I would go get a sneaky pete 50 horse NOS kit and hit the button in 3rd. I used to drag a 70 Chevelle with a 396 making 500 horse and ran 8.64 at 80 mph. It was a full interior all steel car so it was pretty good times. I miss the hell out of that, this out to cure my bug for a few more years.
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1981 924 Weissach, progressive rate coils, Dansk Polished S/S exhaust, free flow Cat, K&N filter

1991 Toyota FJ80
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