No More Mot Fail On De-cat

[BLUE V LTD]

Found this on ebay just what you need for a tunnel run.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...s%3DI%26otn%3D2

[eureka]

Found this on ebay just what you need for a tunnel run.

http://cgi.ebay.co.uk/ws/eBayISAPI.dll?Vie...s%3DI%26otn%3D2

these have been available for a while now

[Maxxed_Ross]

I can't see Mr Plod being too impressed with that, but it is a very cool idea!

[granby]

Was thinking about one of them a while back so i could have a quiet exhaust for normal driving then open it up for a tunnel run , you can also buy just the valve in various pipe sizes to add to any exhaust

http://cgi.ebay.co.uk/Exhaust-Cut-out-Valv...1742.m153.l1262

Edited February 15, 2009 by Granby

[BLUE V LTD]

Was thinking about one of them a while back so i could have a quiet exhaust for normal driving then open it up for a tunnel run , you can also buy just the valve in various pipe sizes to add to any exhaust

http://cgi.ebay.co.uk/Exhaust-Cut-out-Valv...1742.m153.l1262

I have seen these around before but not pre fitted to a pipe. Save's all the cutting around and changing over for the MOT tho. Birthday coming up soon my have to treat myself..

[granby]

I have seen these around before but not pre fitted to a pipe. Save's all the cutting around and changing over for the MOT tho. Birthday coming up soon my have to treat myself..

Do you still have a cat in your system then as theres no cat in that downpipe

Edited February 15, 2009 by Granby

[m@tt untimate STImulation]

bit of warning with this if you get flames! it will set your car alight mabe not the best idea

[emoe]

Theres a couple of minor problems with these kits.

First is the bypass is PRE CAT, therefore you are changing the back pressure, and the Lambda reading when you open it, so the possibility of LEAN WOT is much greater. NOT GOOD!! unless you have a switchable map this may cause a melt down if used too much!!

When the cat is in place, the gasses are different, so when you open the pipe up the lambda will read different. When you DECAT the car, the ECU and lambda regulate and then are stable. When you open and close this valve the lambda reads differing values all the time and c annot settle. This causes the ECU to regulate the fueling at Injectors quite a bit.

The other problem is that as Matt states, the exhaust is right under the car, and that isnt good for both flames and the exhaust fumes, as they will leach into the car from under the body. NOT GOOD!! if i were to advise on one of these, id say manufacture some sort of extra pipework to get the exhaust out to the side or back of the car.

[Deano 666]

one of my customers has this type of valve fitted to his camero (yank car) with a V8 engine and modded exhaust pipes, it is VERY load! his valve is fitted just before the twin silencers (post twin sports cats), and it has a small tail pipe off of the valve pointing to the ground, he uses it for sound off's at car shows.

[BLUE V LTD]

Do you still have a cat in your system then as theres no cat in that downpipe

Only in the down pipe but not for much longer.

Fingers crossed.

[Jolly Green Monster]

Theres a couple of minor problems with these kits.

First is the bypass is PRE CAT, therefore you are changing the back pressure, and the Lambda reading when you open it, so the possibility of LEAN WOT is much greater. NOT GOOD!! unless you have a switchable map this may cause a melt down if used too much!!

When the cat is in place, the gasses are different, so when you open the pipe up the lambda will read different. When you DECAT the car, the ECU and lambda regulate and then are stable. When you open and close this valve the lambda reads differing values all the time and c annot settle. This causes the ECU to regulate the fueling at Injectors quite a bit.

The other problem is that as Matt states, the exhaust is right under the car, and that isnt good for both flames and the exhaust fumes, as they will leach into the car from under the body. NOT GOOD!! if i were to advise on one of these, id say manufacture some sort of extra pipework to get the exhaust out to the side or back of the car.

the lambda reading changing will not effect WOT full stop.. the lambda reading is only used for closed loop fuelling which is idle and cruise.

The lambda sensor is mounted in the top of the downpipe on the classic shape (except 92~95) where it is in the headers.. this is sufficiently far from the valve to be uneffected flow wise by open or shut and will not have any difficulty settling.. plus it is only cruise and idle.

Yes it needs mapping or at least checking between open and closed but it is possible to map it so that one or the other is perfect for 99% use and the other a safe compromise..

I think the long term issue would be the valve jamming due to heat and corrosion.

I would have a side pipe made up so the exhaust fumes exist at the side of the car rather than under

Simon

[baser999]

Thats one hell of a muffler