Decat - before and after dyno figures

[yzf1070]

Something I have often wondered, is just how much is generally gained from decating a standard S6 (just the decat thats all, no chips, no remap etc....).

I have gotten some info from Autocraft they did just this to a T350 last week. The following is the result:

Before decat power was 284 bhp @ 6500 rpm measured at the rear wheels.
After decat 293 bhp @ 6500 at the rear wheels, Power hung on to 6800rpm, but there was a slight drop off at 6500rpm. RR max speed reading in 4th was 165mph.
As hoped the car also picked up a lot easier after decat, showing better throttle response through out. The rolling road was set up correctly and configured with ambient met data (this RR does have a weather station).
A 9 BHP increase is quite good with hopefully a little more to come from a remap session. The car is due to go back in 2000 miles for a service, Craft intend to play around with it some more then.

Incidentally the decat pipes were supplied by Peninsula TVR.

Anyone else with before and after data and then perhaps data from a follow up remap?

Cheers
G

[MrsS]

yzf1070 said:

Something I have often wondered, is just how much is generally gained from decating a standard S6 (just the decat thats all, no chips, no remap etc....).

I have gotten some info from Autocraft they did just this to a T350 last week. The following is the result:

Before decat power was 284 bhp @ 6500 rpm measured at the rear wheels.
After decat 293 bhp @ 6500 at the rear wheels, Power hung on to 6800rpm, but there was a slight drop off at 6500rpm. RR max speed reading in 4th was 165mph.
As hoped the car also picked up a lot easier after decat, showing better throttle response through out. The rolling road was set up correctly and configured with ambient met data (this RR does have a weather station).
A 9 BHP increase is quite good with hopefully a little more to come from a remap session. The car is due to go back in 2000 miles for a service, Craft intend to play around with it some more then.

Incidentally the decat pipes were supplied by Peninsula TVR.

Anyone else with before and after data and then perhaps data from a follow up remap?

Cheers
G

Graham,
How big a mid-range hole was there in the Torque curve?

(Daftlad posting..)

Edited by MrsS on Monday 16th April 08:48

[s6boy]

Only just thinking about this myself, but one question is there a differnce in performance between de-cat pipes and sleeved cats?

[yzf1070]

MrsS said:

Graham,
How big a mid-range hole was there in the Torque curve?

(Daftlad posting..)

Hi John, I don't have the graph only the figures I got from Dave:

Torque figure at the flywheel, there was no loss in torque but at 3000rpm a gain of 6 ft lbs, at 4000rpm the same, at 5000rpm 3 ft lbs, at 5500rpm a gain of 10 ft lbs. Then as you would expect the figures tail off with torque at 6000rpm a gain of 8 ft lbs and at 6500rpm a gain of 6 ft lbs.
Max torque @ 5500rpm 309 ft lbs.

Figures would suggest a healthy motor. Must admit I would have expected a glitch somewhere on the curve that only a remap would sort out. Which is why I mentioned dyno run checks before decat, after decat and after a remap... Then again I have no hands on experience in such matters, I can only relate to what I have read in books etc... and then every car performs differently.

I had to get mine decatted as the additional heat would most likley have melted the cats. I have 2 spare good cats incase of a future MOT failure, but it does seem like a good idea to get rid of them if you can get away with the MOT test. Those are pretty good gains from a standard motor.

Cheers

G

Edited by yzf1070 on Monday 16th April 11:10

Edited by yzf1070 on Monday 16th April 11:14

[scooterscot]

Tuscans struggle to get through an MOT without cats and the new rules for MOT stations make it impossible to fiddle the results. We have seen some very sorry owners after they have taken off the cats.

[plasticman]

Were the pipes used in the test normal cat pipes with the cats taken out or pipes made for the job ? I am asking because I have just bought a tuscan which has been decated using a pipe with a longer taper which I would expect to make more power than the punched out cat type . thanks , David

[xtr2turbo]

I think the other factor in these comparisons is the condition of the cats. Clearly you will gain more by removing whats left of a molten ball of a cat compared to a CAT that is in good condition and free flowing.

David

[yzf1070]

plasticman said:

Were the pipes used in the test normal cat pipes with the cats taken out or pipes made for the job ? I am asking because I have just bought a tuscan which has been decated using a pipe with a longer taper which I would expect to make more power than the punched out cat type . thanks , David

David,

As far as I know they are not just standard cats that have been gutted, but to what spec the pipes were made, I have no idea. Perhaps Penninsula could provide more detailed specifics!

Regards
G

[targarama]

I have two questions:

- Does removing the cats affect noise? Assuming the car has some kind of silencer on the back.
- How easy it is to pass an MOT without the cats in position? (I see the post below about problems), and if not, is it easy to bolt the cats back in position

- OK a third question - are there 2 cats then (since everyone says 'cats' and not 'cat'). I recall my Chimaera had a pre cat then 1 main cat per exhaust 'bank'.

- Darn, a fourth question - what about the lambda sensor? Does this need blanking/earthing or something?

Maybe I should call Peninsula...

[yzf1070]

targarama said:

I have two questions:

- Does removing the cats affect noise? Assuming the car has some kind of silencer on the back.
- How easy it is to pass an MOT without the cats in position? (I see the post below about problems), and if not, is it easy to bolt the cats back in position

- OK a third question - are there 2 cats then (since everyone says 'cats' and not 'cat'). I recall my Chimaera had a pre cat then 1 main cat per exhaust 'bank'.

- Darn, a fourth question - what about the lambda sensor? Does this need blanking/earthing or something?

Maybe I should call Peninsula...

-Yes removing the cats does make the exhaust note slightly more audible....
-Hmm I dunno this one for sure yet (my MOT is due in Oct), I believe it is possible to set the fuel map up so that it would pass, but I am not sure if that would affect smooth running of the car around the 2k5 to 3K rpm mark. (the max values for this test are : 0.2Co % volume and 200 ppm volume, with cats mine came in at 0.019 and 37 respectively and showing lambda 1.016).
- yes the car has 2 main cats (no pre cats) and they are fairly easy to refit if you can get under the car.
-The lambda sensors stay, they control fueling off tick over, to around 4k rpm unless you are running WOT.

Hope this helps
G

[whitey]

Yes, more noise, but not much until you get over 3000rpm or apply some serious throttle then it sounds like a spitfire on crack.

Extremely unlikely it will pass an MOT.

Here is the penisula ones on my engine.

Edited by Whitey on Saturday 12th May 17:15