Cats, Crp's And Sports Cats

[MattyB]

Here:

 

http://forums.seloc.org/viewthread.php?tid=17864

 

Seems to suggest that CRP's can actually *reduce* power? Assumingly due to the loss of backpressure (especially on the VVC) Also claims that Sports CAT's have a small increase power over the CRP, whilst still having the noise and being road-legal...

 

Edited to say...this should really be in "technical" if Beefcake (or another mod person) can move it...

[Scott_Mac]

Interestng, but i can't see that myself...

 

Even a sports cat has a meagre amount of "honeycomb" material inside it, which is after all porous, therefore how in the hell can it increase backpressure???

 

The only evidence i can speak from is that since having my CRP and Sports exhaust fitted, the car is quicker and more responsive.

 

Also if the claims of lost power are ture, exactly how much are we talking? 1bhp, maybe 2... would you notice that?

[Scrappydog]

Scot - dunno if this table will come out okay, but the MGF figures are as follows:

 

Car/Catalyst Power (bhp) Power (bhp) Torque (lb./ft) Torque (lb./ft)

at 3000rpm at peak rpm @ 2,500rpm @ 5,500rpm

 

1.8i/Rover Standard 72 124 129 118

1.8i/Rover Motorsport 73 126 128 120

1.8i/Aftermarket 74 125 129 120

1.8i/Bypass tube 73 127 128 120

 

VVC/Rover Standard 72 147 121 128

VVC/Rover Motorsport 72 148 122 130

VVC/Aftermarket 67 141 116 122

VVC/Bypass tube 67 144 117 126

 

Interesting numbers, especially for VVC cars. But to be honest, I've given up worrying if I've liberated or strangled the odd horsepower or two. Had a CRP but the thing was to loud / boomy with my exhaust and it was cheaper to put the cat back on than buy a new exhaust. Haven't noticed any difference.

 

Andy

[Scott_Mac]

Interesting indeed... seems to make ittle or no diff to the std, but one hell of to the VVC... why is that? What does the VVC do that is so reliant on back pressure??

 

I still think that the massively improved throttle response and the pops and bangs are worth it though... plus bugger all performance loss

[Scrappydog]

Scott,

 

I'm no expert, but it's to do with exhaust backpressure and exhaust scavenging effects. What profile the exhaust cams and the rest of the exhaust system is likely will have a great effect. I guess the answer is that on *some* VVC cars you *could* see a drop of a few hp by fitting a CRP, but it would depend on what manifold and exhaust you are running as well.

 

But as you said, if it sounds nice and make the car more driveable it doesn't really matter does it?

 

Andy

[Scott_Mac]

Yup, can grasp that... just find it a little difficult to comprehend...

 

I'm all for it, the increased driveability sold it to me... oh and the big pops and bangs

[dobbo]

Having done Exige exhaust, Hurricane and CRP separately over the last 18 months, in that order, the CRP made the most difference in noise and performance.

 

Made 134bhp in a recent rolling road.

 

Chris

[Scott_Mac]

Sounds about right.... mine certainly feels good for that power!

[dobbo]

But is it worth doing the throttle body on a fairly standard car (induction, sp exhaust and CRP) ?

 

Chris

[dobbo]

Oops, replied to wrong post.

 

Sorry

[Scott_Mac]

LOL

 

I'll reply in here though.... i'll let you know soon as i have the above mods and a 52mm TB sitting in the garage, i wanted to replace the crappy plastic one as it sticks a lot on my car anyway... as to whether it makes a difference or not, i'll let you know

[MattyB]

On the topic of TB's...its a 48mm as standard, correct? Is the only difference between mine and a standard Elise that the 120bhp one is plastic?

 

So whats this 160TB that everyone goes on about? Is that the 52mm you have Scott?

[Scott_Mac]

No, you have the 160TB as i understand.. main difference is the diameter obviously, the std plastic one and i beleive the 48mm alu one have a lip to smooth airflow on gentle throttle openings... i.e. so its smoother in town.

 

Yes, i have the 52mm one, off a certain black metro you may know

[MattyB]

lol...

 

"I know you've just crashed, but can I have your TB?" Did he break it in the end? I expected he'd sell the whole lump together.

[Scott_Mac]

Its going slowly....

 

I'm hoping he can't sell the engine whole as he has 270 Cams and Verniers in it, which i want!!!!

 

Getting the TB was something like that actually