Question on de-catted manifolds

[richb]

I've just had a set of ACT stainless de-catted manifolds fitted and i) I've noticed that the rear of the car gets a dirty grey dust over it after only 50 miles is this a sign of it running too rich? and ii) it occasionally dies as I pull up at roundabouts and T junctions, would the idle speed be affected by removing the pre-cats and if so how is it adjusted? Any thoughts anyone? Rich...

p.s. feels a lot more rev'y with the manifolds Tim, thanks!

[2 sheds]

It obviously has made a difference, enough to alter the fuel map requirements, are the old cats looking in a bad state ? looks like you might find that extra Omph you were after, but might need a fettle by Mark.
Cheers Tim

[richb]

Thanks Tim, yes I always tought that once they were on together with the smooth inlet hose it would be worth Mark having a fettle! Cheers Rich...

[siwes]

richb
I also fitted ss decatted manifolds and I also removed the main cat, recommend it, I have to say The tail pipes stayed a lovely dark colour.
Easier reving , for sure , but by far the best thing is the sound. Removing cats should not upset the mixture, but if your exhaust is a light grey then all indications are you are running lean and too hot, have it tuned by someone you trust. my opinion of course but running lean can damage the valves and guides so don't do it for too long
regards
simon

[WildfireS3]

siwes said:

richb I also fitted ss decatted manifolds and I also removed the main cat, recommend it, I have to say The tail pipes stayed a lovely dark colour. Easier reving , for sure , but by far the best thing is the sound. Removing cats should not upset the mixture, but if your exhaust is a light grey then all indications are you are running lean and too hot, have it tuned by someone you trust. my opinion of course but running lean can damage the valves and guides so don't do it for too long regards simon

You can also burn through the pistons in extreme cases.

[mongoose]

calling act tim please. ive heard you sell a 'y' pice with removeable cat but cant find it on your website.i can only find the pair of sportscats.have i been misinformed,or is this a new product not yet listed/under development?cheers,mike.

[richb]

siwes said:

richb I also fitted ss decatted manifolds .... my opinion of course but running lean can damage the valves and guides so don't do it for too long regards simon

Thanks Simon, I will get Mark Adams to give it a once over on his trusty lap-top.

p.s. Tim, what gasket stuff do you use to seal the plenum after it has been opened? I have a strange whistle, just like someone with a gap in their teeth! when I accelerate hard. Rich...

>> Edited by richb on Saturday 19th March 12:10

[GreenV8S]

richb said:

p.s. Tim, what gasket stuff do you use to seal the plenum after it has been opened? I have a strange whistle, just like someone with a gap in their teeth! when I accelerate hard. Rich...

Wouldn't you expect a leak here to be more pronounced at part throttle and go away at full throttle? As far as sealing goes, I understand silicone sealant is the stuff, but you need the 'lambda sensor friendly' type. (In fact I think it was Tim himself who told me this, or did I just imagine that bit?)

[2 sheds]

mongoose said:

calling act tim please. ive heard you sell a 'y' pice with removeable cat but cant find it on your website.i can only find the pair of sportscats.have i been misinformed,or is this a new product not yet listed/under development?cheers,mike.

Hi Mike i'm afraid you've heard wrong, the removable/ unboltable cats are only available with our complete new systems.
I had thought about doing a new version of the existing "Y" piece but due to compromises such as 4" diameter flanges and other details i wasn't happy about meaning it would be impossible to achieve more power, i thought it best to just have this feature on the new system only.
Tim

[2 sheds]

GreenV8S said:

richb said: p.s. Tim, what gasket stuff do you use to seal the plenum after it has been opened? I have a strange whistle, just like someone with a gap in their teeth! when I accelerate hard. Rich... Wouldn't you expect a leak here to be more pronounced at part throttle and go away at full throttle? As far as sealing goes, I understand silicone sealant is the stuff, but you need the 'lambda sensor friendly' type. (In fact I think it was Tim himself who told me this, or did I just imagine that bit?)

Yes with a plenum leak it would be loudest as you back off the throttle.
Yes use Automotive acetoxy Silicone, this stuff doesn't have the Citric acid type vapour when curing, which is "cat friendly" i assume all automotive silicones are as this .

Cheers Tim


>> Edited by 2 sheds on Saturday 19th March 19:47

[richb]

OK Chaps, I'll look for some of the automotive acetoxy stuff, on second thoughts and without going and trying it, it might "whistle" on the change-up through the gears which would match what you've said. Rich...

[2Munkys]

Rich

Dunno what kind of plennum you have. If it's one of Tims carbon items I bonded the cork gasket to the flange of the cover and used some of the thick plumbers silicone grease to seal that to manifold plate: makes for an airtight seal and an easier disassembly.

If by chance you have the twin Jenvy set-up, I made a sandwhich plate (load spreader) out of some aircraft spec ali. This removes concerns of overtightening the mounting bolts, distorting the carbon flange and inducing air other than through the throttle bodies. I made two and so have a spare; if this is of use to you then e.mail me at my profile and you can have it (FOC). If of no use (i.e you have a different set-up), then it may be of use to someone else.

And, returning to the thread, I've just fitted a pair of Tims manifolds to my existing 'Y' piece this weekend (as hands bear testament). Had them made in mild steel and ceramic coated as opposed to stainless: function before form! Will be back on the rollers soon for a quick tweek but the car drives no differently than with my none reversal coned originals.

Bruce