De Cat or Cat ??????

[Paul@1320]

..........everytime we put the Janspeed cat back in we gain horsepower, the 11.77 and the 119mph had the cat in.

Has anyone else experienced this??

[alski]

so are you saying no point in having de-cat, or indeed a de-cat is a power looser

[Paul@1320]

At the moment yes, but to be fair I haven't tested like for like, we tested a straight pipe and not de cat pipe in the shape of the Janspeed cat.

The only way to test it properly is buying buildin a de cat pipe the same shape as the Janspeed cat.

I must point out that this is what we have found with our car, what it'll do on your own is another matter.

We'll be testing another exhaust theory hopefully today.

We have over 70 passes on the dyno in the last couple of months testing different combos

[Richard Crofts]

The supercharger does like some BP mind ... so maybe the removal of the cat looses a wee bit too much BP and causes the loss in power. I know on a turbo BP is bad and so big straight pipes are bsest but its been shown on s blown cars this is not true and doing big straight pipes can loose some hp .... maybe thats what occurs?

[TallAndy]

de-cat sounds better though

[Snowie]

Has any one any idea on what is the ideal exhaust back pressure.

Mine is currently circa 3.4 PSI Is this too high and interfeering with BHP gains

Set up is GP with JCM 4.2.1 Sports cat and standard GP twin rear silencers complete with the 'flat' bit before the 'y' piece.

[MINI-Morgan]

I'd be interested to see some testing on this Any results would be good

[MiniPetrolHead]

Yeah that would be interesting! A mate of mine put the ebay manifold on which has a decat.
It sounds fantastic but we think it may be loosing him power along with the GTT re-route pipe there probably isnt enough back presure.

His car just feels revvy and not torquey, where as mine revd slower hardly noticable with the standard manifold, yet mine feels so much more torquey!

When he had that manifold and de-cat on, 15% pulley, iridium plugs, pannel filter and re-route pipe the cars were neck and neck (apart from initially when the torque of my car put me ahead by 3ft) when i only had my MiniMania exhaust manifold.

Alex

[MINIMANIAUK]

Its more about scavenging , than back pressure. lower the better with BP

[MiniPetrolHead]

Quote: Originally Posted by MINIMANIAUK (original)

Its more about scavenging , than back pressure. lower the better with BP

What do you mean?

Alex

[Paul@1320]

Quote: Originally Posted by Snowie (original)

Has any one any idea on what is the ideal exhaust back pressure.

Mine is currently circa 3.4 PSI Is this too high and interfeering with BHP gains

Set up is GP with JCM 4.2.1 Sports cat and standard GP twin rear silencers complete with the 'flat' bit before the 'y' piece.

We've been eperimting with cat backs and it seems that what you think should work doesn't and what shouldn't work does.

The difference in trq on some is unreal. We were discussing today about having a catback shootout one day next week

[MINI-Morgan]

Any dyno results in? Especially the MINI Mania 4-2-1 Manifold?

[Paul@1320]

No sorry to busy and Adams shipment hasn't come in as far as I know but soon as it does we'll let you know

[ScottyBoy]

Quote: Originally Posted by Mini-Morgan (original)

I'd be interested to see some testing on this Any results would be good

Roland started a thread on this a while ago when he was testing back pressure of a few different exhaust, the JCW is pretty poor in comparison

Hears the thread

http://www.mini2.com/forum/engine-dr...g-results.html

Scott

[MINI-Morgan]

Quote: Originally Posted by ScottyBoy230 (original)

Roland started a thread on this a while ago when he was testing back pressure of a few different exhaust, the JCW is pretty poor in comparison

Hears the thread

http://www.mini2.com/forum/engine-dr...g-results.html

Scott

Thanks So far as I was aware Roland hasnt released any tests results for precat pressure and the performance change with reducing the pressure.