Removal of Catalysts
Discussion
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.
don't worry, BHP is less important than torque, which your beastie has in abundance. If you bin your cats you will have to remap the ECU with the lambda sensor loop taken out...oh and unless you can get the same people who modify it to MOT it, you will need to put it all back again. This is an option however, there are plenty of reputable specialists around
quote:
Surely if your BHP is down your torque will also suffer.?
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.
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
quote:
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
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)
Thanks for the replys, Ive been told if I take the two smaller cats out that will give the Griff up to 15 BHP more and make it sound even better, if thats possible. Has anyone done this and how do other Griff owners feel about TVR stating 320-340 BHP when it seems that in real terms its a hell of a lot lower, and is it the same with Cerbs and Tuscans.
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Has anyone done this and how do other Griff owners feel about TVR stating 320-340 BHP when it seems that in real terms its a hell of a lot lower, and is it the same with Cerbs and Tuscans.
A recent rolling road test suggested that a good 4.2 Cerb is around 350bhp (TVR claim 350), a good 4.5 Cerb is around 370bhp (TVR claim 420) and an RR Tuscan does what it says on the tin at 380bhp
Edited by MikeE on Tuesday 16th October 16:52
quote:
quote:
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
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)
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
quote:
If your 500 only puts out 260 bhp..what the bloody hell does my 400 put out...I'll be lucky if I've got enough power to give a tractor a run at the lights...
According to my TVR mechanic who knows his stuff a 4 litre Chimp makes 180-190BHP and a 4 litre Griff without cats just breaks 200 BHP on a good day, this is the case with all the TVR rover engines.
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.
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.
TVR are not alone in this, most companies exaggerate their output claims also larger companies test loads of engines in lab conditions and nail the best ones figures to the board for the ad campaigns. How bhp is measured is another variable you do not want to become embroiled in......but probably will, I did
see my post above (below depending on prefs) and also this
www.pumaracing.co.uk/coastdwn.htm
it gives details about rolling road figures and coastdown etc.
Sparks
www.pumaracing.co.uk/coastdwn.htm
it gives details about rolling road figures and coastdown etc.
Sparks
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