Exhaust opinion's?

[Muzza]

OK so the engines back out as I have a gear oil leak that I can't find plus 3rd gear is starting to crunch when coming down through the gears. So I was wanting to change the exhaust as it's a scorpion on and I hate the look of it. Plus I'm using a standard down pipe so wanting to no if there's any benifit in a four branch mamaifold over the standard one?? And where the best place to get a one piece down pipe. Thanks in advance

[Ian S]

With a 4 branch manifold over the standard one, some people have reported a small improvement in midrange coming onto boost. The standard one does not flow all that well at the gearbox end. It may cause the engine to make a slightly different amount of power at each end. That may be partly why it's usually the water pump end piston that expands more and rubs the liner; more power and heat at that end due to the longer length and better flow from that end.

Apparently the sound changes, becoming more even and less, 5GTT.

Someone on here, Matty, is making some down 2 1/2 inch pipes. http://www.rtoc.org/boards/member.php?5843-Matty

[Muzza]

OK see what you mean. There doesn't seem to be a lot available on the manifold or the down pipe as I'm trying to get a new one then when engine is out make up a few brakes as I have heard of them cracking. Still a bit undecided tho :rolleyes::rolleyes:

[Matt Cole]

It depends on what you want power wise from the engine. The stock manifold is fine for over 200BHP coupled with a 2.5" down pipe and decent exhaust. Matty can also make you a bespoke exhaust if you want.

[Matt Cole]

http://www.rtoc.org/boards/showthread.php?39679-Exhaust-build-thread&highlight=downpipe

downpipe thread.;)

[Matt_S]

My experience with tubular manifolds (on other cars) is that they release potential but induce lag slightly, as the gases have further to travel initially. If you're not planning on going over 220-240 (which the std item can flow) I wouldn't bother. Plus, if you particularly like the 'warble' then leave it, as the tubular eradicates that. :)

[Muzza]

Thanks folks thats just what i needed to know. The standard one wil be stayin on it then get a down 2.5" down pipe. Thanks for the help yet again.

[Matty]

As said above, I can help with making up and downpipe and full system (and manifold).

I've decided to make a tubular manifold up for mine, but Slightly differnet to others made, all the ones I have seen the primaries look massive which kind of defeats the object of them. ;)

Here's the downpipes I make. Top one is a 3" to 2.5, the bottom one is 2.5" all the way through.

http://i245.photobucket.com/albums/gg50/Mattymini23/69e1d94513b14fa12864ae9b9d32dafd_zpsgre0xqul.jpg

http://i245.photobucket.com/albums/gg50/Mattymini23/0bfb4c17e89cb415cbe0fcd1d11beba3_zpsurb2mz30.jpg

[Ian S]

I don't have any specs on it but Mike Spencer (Mike 48) (enough years ago now that it seems like almost a different lifetime!) had a manifold made by Simpsons, and a matching down pipe and maybe exhaust. They felt it boosted earlier and lagged less. I don't recall him saying they got any more peak power figure.

I seem to recall that went on the car of someone in North West London but don't recall who.

It was A LOT more expensive than those Raceland ones we had done for the club shop a few years ago which, IIRC, were about £130 delivered. I didn't have and try one of those as I don't run a 5 and no-one gave me any meaningful feedback on the effect of those.

I did fit a nice one on my Fiat and that gave me about another 1000 useful RPM at the top end of the range, ie, 7000 instead of 6000. Tuning an engine is not just about chasing some headline power figure.

[Matty]

Yeah from what I found as a general rule is that boost comes in earlier, on an equal length manifold, but this also relies on the pipe sizes being correct. From the pictures I have seen of the tubular manifolds available they are either 32mm bore or 35mm bore pipe (could be wrong through?). Ideally you dont want to go for something around the exhaust valve size, as restriction isn't an issue like an NA engine, as the turbine is the biggest restriction. I'm going to use 29mm bore pipe for the one I am making, this should make the turbo spool quicker, and increase the mid range torque.

On some of the engines I have made exhausts for they haven't gained Peak HP as such, but they have made the same power with less boost, and broadened the power accross a larger Rev range. My aim is not big numbers, but a torquey engine with a broad power band. As the T25 .49 exhaust housings seem to be non existent I am hoping that it will help spool a .64 rear end.

It would be good to see what Simpsons came up with!

[Muzza]

Yeah from what I found as a general rule is that boost comes in earlier, on an equal length manifold, but this also relies on the pipe sizes being correct. From the pictures I have seen of the tubular manifolds available they are either 32mm bore or 35mm bore pipe (could be wrong through?). Ideally you dont want to go for something around the exhaust valve size, as restriction isn't an issue like an NA engine, as the turbine is the biggest restriction. I'm going to use 29mm bore pipe for the one I am making, this should make the turbo spool quicker, and increase the mid range torque.

On some of the engines I have made exhausts for they haven't gained Peak HP as such, but they have made the same power with less boost, and broadened the power accross a larger Rev range. My aim is not big numbers, but a torquey engine with a broad power band. As the T25 .49 exhaust housings seem to be non existent I am hoping that it will help spool a .64 rear end.

It would be good to see what Simpsons came up with!



Pm you there matty.

[Muzza]

Dragging this up again but is it only cgb do the adjustable cam pullys??

[Matt Cole]

Mike at gt turbo spares does. You get 5% club discount too!:D