Thought I'd start a thread on this as I've made a little progress today.
I'm going to help my GS to breathe better, starting with the exhaust system and then (hopefully) moving onto the intake when Newton can report progress on the version he's creating.
My GS has the (seemingly) highly restrictive US exhaust system -
hideous, fat, inefficient manifolds with inbuilt cats that go into the squish pipe and a further cat each side:
I have Larini valved rear boxes fitted already which make a glorious roar, but also a terrible boom between 2k-3k revs.
Today I bought a pair of 4200 exhaust manifolds which don't have the cat built in for a bargain price. These manifolds are known to be better flowing and have larger diameter pipes than the US-spec.
I've looked at the differences between Larini and Supersprint exhausts and they appear to have a very similar design, but significantly different prices - the Larini option costing around 50% more than Supersprint, even when discounted.
I've been in touch directly with Supersprint in Italy and have been very impressed with their response.
I've decided to go with the Supersprint pipes with sports cats. These will feed into a straight through sports silenced x-pipe and then exit through the Larini rear boxes. It will look like this:
The squish pipes are changed for 2 smaller pipes to clear the steering rack, which should be better flowing than stock. The sports cats are 200 cell which will also free up a lot of the blockage of the standard system. The only additional work will be to extend the lambda wires that will now fit after the sports cats. Supersprint have already sent a complete guide to doing this including pictures.
I will be ordering the Supersprint parts soon and expect them to take a few weeks to arrive as they are made to order. I will also be putting my car on a rolling road to get a definitive before and after comparison to see if any more power is released.
As more happens I will update this thread.
I'm going to help my GS to breathe better, starting with the exhaust system and then (hopefully) moving onto the intake when Newton can report progress on the version he's creating.
My GS has the (seemingly) highly restrictive US exhaust system -
hideous, fat, inefficient manifolds with inbuilt cats that go into the squish pipe and a further cat each side:
I have Larini valved rear boxes fitted already which make a glorious roar, but also a terrible boom between 2k-3k revs.
Today I bought a pair of 4200 exhaust manifolds which don't have the cat built in for a bargain price. These manifolds are known to be better flowing and have larger diameter pipes than the US-spec.
I've looked at the differences between Larini and Supersprint exhausts and they appear to have a very similar design, but significantly different prices - the Larini option costing around 50% more than Supersprint, even when discounted.
I've been in touch directly with Supersprint in Italy and have been very impressed with their response.
I've decided to go with the Supersprint pipes with sports cats. These will feed into a straight through sports silenced x-pipe and then exit through the Larini rear boxes. It will look like this:
The squish pipes are changed for 2 smaller pipes to clear the steering rack, which should be better flowing than stock. The sports cats are 200 cell which will also free up a lot of the blockage of the standard system. The only additional work will be to extend the lambda wires that will now fit after the sports cats. Supersprint have already sent a complete guide to doing this including pictures.
I will be ordering the Supersprint parts soon and expect them to take a few weeks to arrive as they are made to order. I will also be putting my car on a rolling road to get a definitive before and after comparison to see if any more power is released.
As more happens I will update this thread.
