Cats and turbos
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JNLRacing
kevhaywire
6 posters
OddUnit :: The Workshop :: Engine
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Cats and turbos
So how much of a restriction do they present to a turbo in moderate boost applications (up to 15psi)?
I've had a 3" ceramic cat laying around for a while and I'm tempted to fit it. Anyone know of any before and after plots? If they sap 50hp or more, then I won't bother, but 15 - 20hp I can live with.
Anyone got any firm data / ideas?
I've had a 3" ceramic cat laying around for a while and I'm tempted to fit it. Anyone know of any before and after plots? If they sap 50hp or more, then I won't bother, but 15 - 20hp I can live with.
Anyone got any firm data / ideas?
kevhaywire- .:Stroked:.
- Number of posts : 605
Re: Cats and turbos
I'm running a 3" sport cat on mine and it's so small it may aswell not be in there. Really can't see it making a lrge hp difference at all.
JNLRacing- .:Cammed:.
- Number of posts : 205
Re: Cats and turbos
Spoke to someone today who has done a back to back dyno comparison of cat versus non-cat. It was a small 3" 100 cell sport cat and it made 367hp without the cat, and 345hp with.
Not a huge difference in outright power, but he did say the spool up is where you notice the cat's prescence the most. It's noticably slower to spool, so much so the timing needed adjusting to prevent det.
I think I'll leave the cat off then
Not a huge difference in outright power, but he did say the spool up is where you notice the cat's prescence the most. It's noticably slower to spool, so much so the timing needed adjusting to prevent det.
I think I'll leave the cat off then
kevhaywire- .:Stroked:.
- Number of posts : 605
Re: Cats and turbos
kevhaywire wrote: so much so the timing needed adjusting to prevent det.
How come?
Was the onset of boost less progressive??
dirtytorque- .:Charged:.
- Number of posts : 1101
Re: Cats and turbos
22bhp for £600ish at a guess on price is brill to be honest.
junkie- .:Bored:.
- Number of posts : 376
Age : 43
Location : Rotherham
Re: Cats and turbos
It's a 22hp loss dudejunkie wrote:22bhp for £600ish at a guess on price is brill to be honest.
Re: Cats and turbos
hahaha totally read that wrong oh the shame.
Well does this also mean it can be looked at from another angle though, what was the power run with the standard cat on, im sure the sports cats are more for the people who want to run a better flowing exhaust whilst still passing an MOT without the need to be changing back and forth every year.
So ultimately a no cat system will flow better of course and a sports cat will always flow worse due to there still been a restriction there which affects spool but will be better than a standard restrictive cat due to less cells.
Well does this also mean it can be looked at from another angle though, what was the power run with the standard cat on, im sure the sports cats are more for the people who want to run a better flowing exhaust whilst still passing an MOT without the need to be changing back and forth every year.
So ultimately a no cat system will flow better of course and a sports cat will always flow worse due to there still been a restriction there which affects spool but will be better than a standard restrictive cat due to less cells.
junkie- .:Bored:.
- Number of posts : 376
Age : 43
Location : Rotherham
Re: Cats and turbos
kevhaywire wrote:
Not a huge difference in outright power, but he did say the spool up is where you notice the cat's prescence the most. It's noticably slower to spool, so much so the timing needed adjusting to prevent det.
I think I'll leave the cat off then
That must be a fair restriction then, to be robbing the engine of 6% of its peak power.
boost panda- .:Bored:.
- Number of posts : 307
Re: Cats and turbos
Yeah, the chap said 6% is the average loss he sees with "Sport" cats on the Rover Tomcat engines he maps. I hate to think how restrictive OE cats are then!
The reduction in timing I suspect is to combat the backpressure raising EGTs. Standard 1.8T maps have zero degrees timing on boost at certain loads and rpms, so it's obviously an issue VW have encountered too.
The reduction in timing I suspect is to combat the backpressure raising EGTs. Standard 1.8T maps have zero degrees timing on boost at certain loads and rpms, so it's obviously an issue VW have encountered too.
kevhaywire- .:Stroked:.
- Number of posts : 605
Re: Cats and turbos
kevhaywire wrote:Yeah, the chap said 6% is the average loss he sees with "Sport" cats on the Rover Tomcat engines he maps. I hate to think how restrictive OE cats are then!
The reduction in timing I suspect is to combat the backpressure raising EGTs. Standard 1.8T maps have zero degrees timing on boost at certain loads and rpms, so it's obviously an issue VW have encountered too.
ahhh...
thnks.
dirtytorque- .:Charged:.
- Number of posts : 1101
OddUnit :: The Workshop :: Engine
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