Janspeed manifolds - Worth the money?

[dave23572]

Subject says it all really.
Are the Janspeed manifolds for the 180 worth the money?

1. Is it a good and noticeable performance increase?
2. Is the increase all through the rev range or only in certain ranges?
3. Does it reduce torque in any rev ranges (compared to standard manifolds)?
4. Would the manifolds give a good performance increase when used with an otherwise standard exhaust system and CAT? or does it really need a sports cat etc?

Dave

[Drew]

yes.



i cant say how much you would get on a std exhaust as i already had a decat and full system, but the gains are there to see.

Drew

[dave23572]

So those gains were with the manifold replacement alone?

And what did the gains feel like when driving?
Very noticable?

Dave

Originally Posted by Drew

yes.


i cant say how much you would get on a std exhaust as i already had a decat and full system, but the gains are there to see.

Drew

[redzed]

Throw a decat with it and it sounds amazing, very noticable gains and transforms the sound of the car

[dave23572]

Originally Posted by redzed

Throw a decat with it and it sounds amazing, very noticable gains and transforms the sound of the car

But presumably then the car is not legal?
Don't you have to keep re-fitting a temporary cat for the MOT?

[Fred68]

From what I seen, the JS manifold is well short of optimum. It makes more power than the original manifold. Not because the JS is particularly good, more the standard manifold is particularly bad.
The primaries are way to short for decent torque at the kind of RPMs the KV6 can muster.
The finish on the standard manifold is dire. Just look at this collector. The JS has to be be than the standard manifold.

[dave23572]

Originally Posted by Fred68

From what I seen, the JS manifold is well short of optimum. It makes more power than the original manifold. Not because the JS is particularly good, more the standard manifold is particularly bad.
The primaries are way to short for decent torque at the kind of RPMs the KV6 can muster.
The finish on the standard manifold is dire. Just look at this collector. The JS has to be be than the standard manifold.

That really is disappointing to see.
Looks like with some more effort they could have designed something way better.

But I guess in the absense of anything better, the JS manifold may still be worth considering, given that it's still a good gain over the standard one?

Dave

[Fred68]

Originally Posted by dave23572

That really is disappointing to see.
Looks like with some more effort they could have designed something way better.

But I guess in the absense of anything better, the JS manifold may still be worth considering, given that it's still a good gain over the standard one?

Dave

The only other way is making a good manifold your self.
The primaries want to match the ID of the exhaust ports and be as close to 30" long as possible before the collectors. The bends need be smooth and mandrel formed. The collectors need to be 1 over 2 and correctly welded so as not to impede gas flow. The secondaries need to be around 2" ID and be approximately half the length of the primaries. These then need to collect into a 2 1/2 free flowing system.
It's possible to build up a much better set of manifolds than the JS version.

[dave23572]

Originally Posted by Fred68

The only other way is making a good manifold your self.
The primaries want to match the ID of the exhaust ports and be as close to 30" long as possible before the collectors. The bends need be smooth and mandrel formed. The collectors need to be 1 over 2 and correctly welded so as not to impede gas flow. The secondaries need to be around 2" ID and be approximately half the length of the primaries. These then need to collect into a 2 1/2 free flowing system.
It's possible to build up a much better set of manifolds than the JS version.

If only I were able to make such a thing!

It's a shame there was never a performance replacement for the entire plenum (apart from the Sprintex supercharger plenum).
The normal plenum really doesn't look like it would flow well. And we all know how well designed and reliable the VIS system is don't we?

Theoretically, I expect with the exhaust manifold you described and an optimal plenum, the KV6 would have performed much better.

[petet16]

The result of a limited development budget for the zs, and the need to package it to fit in the front of the 45/zs.