Cat bypass pipe

[keirv6]

Has anyone taken there cats off,any bhp gain,where did you get them?

[m12_nathan]

Lee has previously stated youd get a 3bhp increase by removing the cats (which are welded in).

I spoke to the head of Miltek at a meet and let him have a look at the exhaust - he'd be happy to make an after market one for the car without cats (so it spits flames ) or with 100 cell race cats but needed to be convinced he could sell 100 before he'd do it.

[Ash GTO 3R]

How much and when?

How much because the boss needs to know.

I think you can prob count me in tho.

[m12_nathan]

I told Phil I'd get back to him at the beginning of next year, probably around £400 for one with no cats from what he was saying. It'd be worth checking with the factory or yellowshed that a different exhaust won't lead to any issues with the turbo spooling up too hard or something?

[DanH]

Could just get a custom pipe made up as others have done. Finding 100 buyers will be near impossible I reckon unless the factory decides to use them!

[gotapex]

m12_nathan said:

Lee has previously stated youd get a 3bhp increase by removing the cats (which are welded in).

Wow, that's amazingly low for a turbocharged car. The ECU must be compensating for the decreased backpressure (and the stock cats must be very very good). Typically, turbocharged vehicles gain a bit of HP from the backpressure change, and more from the bit of extra boost that causes.

[YellowShed]

Can verify the power loss with/without the cats is NOT worth the effort. Even fitted with much bigger cats for meeting Euro Stage III/IV emissions, the power loss was only 20odd bhp. The metallic cats fitted to meet the SVA are very low backpressure and much smaller than those required for full emissions, hence the negligible power loss.

YellowShed

[gotapex]

YellowShed said:

Can verify the power loss with/without the cats is NOT worth the effort. Even fitted with much bigger cats for meeting Euro Stage III/IV emissions, the power loss was only 20odd bhp. The metallic cats fitted to meet the SVA are very low backpressure and much smaller than those required for full emissions, hence the negligible power loss. YellowShed

Do you happen to know if this holds with the M400 as well?

[YellowShed]

Haven't even bothered to check. I've no doubt that there would be a similarly small difference. What's with the belief that it's worth doing these days? It doesn't make any difference with the noise or performance, so why bother?

YellowShed

[thatphilbrettguy]

YellowShed said:

Haven't even bothered to check. I've no doubt that there would be a similarly small difference. What's with the belief that it's worth doing these days? It doesn't make any difference with the noise or performance, so why bother? YellowShed

I've suspected for some time (correct me if I'm wrong) that for low(ish) boost cars, which the Noble is, that the exhaust doesn't really make a massive difference to power. I can see how on say, an EVO @ 2BAR the back pressure would just stop that level of boost being generated in the first place, but @0.7-0.9 it'd have to be a terrible system to cause any problems.

Spool times etc are probably a different matter.

[m12_nathan]

YellowShed said:

Haven't even bothered to check. I've no doubt that there would be a similarly small difference. What's with the belief that it's worth doing these days? It doesn't make any difference with the noise or performance, so why bother? YellowShed

Not bothered about anything other than being able to spit flames on the overrun

[ThatPhilBrettGuy]

m12_nathan said:

Not bothered about anything other than being able to spit flames on the overrun

Ah, flames out the exhaust. Not big and not clever....hands up who doesn't want them. Thought so...

A friends Skyline spits out the odd corker of one. Then again you'd expect that out of a 9000RPM 2Ltr 6cyl with a big T4 stuffed on it. Nice.

I'm guessing the same amount of fuel is there with the cats as without. I'd say with a good ECU and the tallents of Mr YellowShed there are not many flames to be had. Switchable maps for a max-power mode it is then!

[gotapex]

YellowShed said:

Haven't even bothered to check. I've no doubt that there would be a similarly small difference. What's with the belief that it's worth doing these days? It doesn't make any difference with the noise or performance, so why bother? YellowShed

Part of it must be the difference between vehicles there and in the USA. Turbocharged cars on this side of the pond still get a pretty nice HP bump with the removal of the stock cat. I have no prior experience with cars over there; perhaps yours are far FAR less restrictive.

[DanH]

Gotapex thats what yellow shed is saying. Nobles go through an approval process called SVA (single vehicle approval) which is a lot less strict than normal euro type approval and is designed to allow low volume manufacturers and kit car makers to legally make cars. The emissions limits on this test are far far less strict than on a fully type approved car, so the cat doesn't need to do very much at all.

[gotapex]

DanH said:

Gotapex thats what yellow shed is saying. Nobles go through an approval process called SVA (single vehicle approval) which is a lot less strict than normal euro type approval and is designed to allow low volume manufacturers and kit car makers to legally make cars. The emissions limits on this test are far far less strict than on a fully type approved car, so the cat doesn't need to do very much at all.

Ah, good to know, thank you.