Removal of Catalysts

I've finally done it, bought the car of my dreams, a TVR Griffith 500. Now im considering removing the two smaller cats and asked a TVR mechanic friend of mine how to go about this and when he mailed me back he wrote the Griff 500 only bangs out 260 BHP and thats if its a good one, now that came as a bit of a shock as TVR claim 320-340 BHP. Has anybody had there TVR tested and has anyone taken the cats out of their Griff and if so could they please give me any information that could be relevant.

I've been told as long as I leave the main cat alone which don't affect BHP it will pass a MOT. The two smaller cats are just for cold starting. Thats what I've been told.

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Surely if your BHP is down your torque will also suffer.?

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yes but torque tails off at high(er) revs, where the power is made. Low down torque won't be much affected.

see these links for info on BHP and torque

www.pumaracing.co.uk/power1.htm
www.pumaracing.co.uk/power1.htm
www.pumaracing.co.uk/power3.htm


Sparks

Edited by Sparks on Tuesday 16th October 08:34

Edited by Sparks on Tuesday 16th October 08:36

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I've been told as long as I leave the main cat alone which don't affect BHP it will pass a MOT. The two smaller cats are just for cold starting. Thats what I've been told.

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As far as I am aware you can remove the two smaller cats without any changes to the ECU and it will still pass an MOT.

I'm not sure of the BHP benefits but the car will sound slightly meatier as a result.

However, in your insurance companies eyes this will be considered as modifying the car therefore you are supposed to inform them...

Cheers,
Graham

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it will pass the emissions test if you remove the two pre cats... its only when you take the main cat out you need to fiddle with the ecu and that can be done by just changing the ecu balst resistor

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Taking the pre-cats out is worth about 5-10 bhp. It also makes the exhaust slightly louder which can be a problem on some circuits. The pre-cats won't affect the tune significantly and you don't need to get the ECU chipped, but if you're getting it chipped take the pre-cats out first.

If you take the main cat out and want to go 'open loop' you need to change the ECU map. The ballast resistor can be used to switch maps but there's no guarantee the 'open loop' map you switch to is right for the car. (You're pretty lucky if the map you normally use happens to be about right.)

I would always get a 'Mark Admas' setup after any major changes. This doesn't always make a big difference to the peak power but in my experience it makes a big difference to the throttle response and removes hesitation and flat spots. That way you can be sure all the sensors are working properly and the fuelling is right for your particular engine.

Cheers,
Peter Humphries (and a green V8S)

HAs anyone been quoted a price to take out the precats?

Peter, do you think a deprecated motor would pass an MOT? No deprecation intended.

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it will pass the emissions test if you remove the two pre cats... its only when you take the main cat out you need to fiddle with the ecu and that can be done by just changing the ecu balst resistor

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Taking the pre-cats out is worth about 5-10 bhp. It also makes the exhaust slightly louder which can be a problem on some circuits. The pre-cats won't affect the tune significantly and you don't need to get the ECU chipped, but if you're getting it chipped take the pre-cats out first.

If you take the main cat out and want to go 'open loop' you need to change the ECU map. The ballast resistor can be used to switch maps but there's no guarantee the 'open loop' map you switch to is right for the car. (You're pretty lucky if the map you normally use happens to be about right.)

I would always get a 'Mark Admas' setup after any major changes. This doesn't always make a big difference to the peak power but in my experience it makes a big difference to the throttle response and removes hesitation and flat spots. That way you can be sure all the sensors are working properly and the fuelling is right for your particular engine.

Cheers,
Peter Humphries (and a green V8S)

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Thanks Peter I've got Marks number, he was recommended by my mechanic, the inlet on the 500 is also restrictive, and its maybe a good investment to go for a larger throttle body and airflow meter, what do you think, I just want my 340 BHP without breaking the law and I want to be able to do track days without hassle, but I don't want the car to be unsellable, any advice very welcome.

Cheers
Mark and his underpowered Griff 500

My 99 griff 500 went on a rolling road last week. 255 with 291 lbf-ft torque. I Was not happy on the way home, but thinking about it its not slow! My sat nav gives top ten 1/4 mile times, time and place and best of 12.3 seems up there with the big boys.
David.

This issue has been raised before. You will find that most BHP figures quoted by manufacturers are taken at the flywheel - ie with no drag from the transmission and drivetrain components.

Thus when you measure on a rolling road you will get a lower figure. It may well be that the flywheel figure is optimistic, but all engines are different and wear will also affect the reading.

When it comes down to it, does it feel slow to drive, prob not. It's a bit like the maxpower mob getting hung up on 0-60 times, how often do you use 0-60 on a public road.

Just enjoy it.

Although im very dissapointed with these BHP figures, in reality all Tiv's still go like Billy Ho.
So is it worth worrying about?

Bit naughty on TVR claiming these figures though.



Edited by Saturn 5 on Wednesday 17th October 08:22