De pre-cat Griff?

[howard45632]

I have a 95 Griff 500 with the serpentine engine (60k miles). Standard except a 'sports exhaust'.

I gather it is possible to remove the pre cats. Has anyone any experience of this? Does it provide the combination of more noise/ more power/ still MOTable? If so, why hasn't everyone done it?

Thanks in advance

[GreenV8S]

Doesn't make a significant difference to noise or power, unless the precats are blocked. It costs a couple of hours of labour, so hardly worth doing unless there is a problem with the precats.

[johno]

Doesn't make any notable difference ... or at least it didn't to mine. I only did mine as they had evidently moved in the manifold, so took em out. Bugger of a job to do, and nothing gained except a couple of gouges to my hands !

[mongoose]

It makes the sound nicer for sure,done it on both of my griffs now.No noticeable effect on power though.Its still a great idea to get rid of them because it helps reduce the underbonnet temperatures,which affect so many things under there.If you go fully de-catted with a good system of manifolds and downpipe,then you can certainly make more bhp and torque here.Get em out,no good reason to keep them at all,oh and yes your car will still pass the emissions easily as long as its all running ok of course

[richb]

howard45632 said:

<clip> why hasn't everyone done it?<clip>

Well you will find that many owners have. I didn't actually remove mine as I replaced the manifolds with some of Tim Lamont's ACT stainless manifolds which have no pre-cats in them and are fitted with non-reversal cones. Not really sure about the power as like all mods I did it at the same time as I replaced the coil, fitted magnoacore leads and Bosch injectors. Along with the already existent mods I was getting 300 bhp/325 ft lbs on Austec's rollers. It is slightly louder bit not excessively, what I did notice though was much more popping and banging on the over-run presumably because there is more unburnt fuel getting past the main cat. Rich...

>> Edited by richb on Wednesday 19th April 09:22

[forthright MC]

you could just put a couple of Cherry bombs on it as they are brilliant if it is more noise you want!
or alternatively you could open the exhaust up, take out all the rattly bits and then weld it back together at the join. a few S series owners have done this, so i guess it would work well on a Griff.

>> Edited by forthright MC on Wednesday 19th April 16:43

[IPAddis]

Compared to standard TVR manifolds, having the pre-cats removed and flow-cones inserted is supposed to be worth at least 5bhp. Ask V8 Developments, they test enough manifolds.

Ian A.

[howard45632]

Thanks guys. The general concensus from this thread and various TVR workshops seems to be a little more noise, perhaps some more power (more likely a little more torque) and no hassle in the future with MOTs.

So, they are coming out! No brainer really.

I will report back having collected the car. Can't wait!

[howard45632]

Just picked up the car having had the pre-cats out. Whahey!!!!

Didn't really sound any different when I first fired it up (shame), but on the move - lovely!!

Best desribed as the same language but with a different accent, definately more puposefull when the revs are up, but still reasonably civilsed when they are down.

Not sure if there is any more power but it feels a little 'crisper' and revs more smoothly.

Worth every penny - get 'em out!!!!

[sam gamgee]

howard45632 said:

Just picked up the car having had the pre-cats out. Whahey!!!! Didn't really sound any different when I first fired it up (shame), but on the move - lovely!! Best desribed as the same language but with a different accent, definately more puposefull when the revs are up, but still reasonably civilsed when they are down. Not sure if there is any more power but it feels a little 'crisper' and revs more smoothly. Worth every penny - get 'em out!!!!

Sorry to have to ask....how much dollar???

Dave.

[howard45632]

£300, I had it done whilst the car was in having a major service.

The cost covers labour and new manifold gaskets.

[sam gamgee]

howard45632 said:

£300, I had it done whilst the car was in having a major service. The cost covers labour and new manifold gaskets.

Ta mate!!

Dave.

[seabrookd]

Does anyone know what the pre - cats are supposed to do, and why TVR put them in?

I've heard about removing them, but surely they must serve some purpose?

Dave

[richb]

Yes, in order to pass EU tests (or something) the car has to be able to pass certain emission tests within 5 mins. of starting up form cold. The pre-cats are closer to the exhaust ports and so heat up quicker than the main cat and therefore are operative more quickly. Once the main cat has heated up they are superfluous. This requirement is however only to get certification for the manufacturer so once the car is on the road they can be removed and as long as the car is warmed-up before being tested will still pass the emission tests for an MOT. Without them there is less gubbins in the exhaust manifolds, it is debatable if it gives more power (some people swear it does other say not) but if the pre-cats are starting to degrade then removing them will help. And of course the car sounds better. Rich...