catalytic bypass
11-02-2003 | 04:40 AM
#1
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From: suffolk,england
catalytic bypass
I am considering fitting a cat bypass to my car and have a few questions.
1) Are all 964's fitted with cat converters,my car is a 1990,here in the UK we can get away with needing a cat if the car was manufactured before I believe 1992.
2) How much HP will I actually gain ?,the system I am looking at quotes a gain of 15 hp.
3) If I fit a cat converter bypass will I have flat spot probs?
Paul
C2 cab
1) Are all 964's fitted with cat converters,my car is a 1990,here in the UK we can get away with needing a cat if the car was manufactured before I believe 1992.
2) How much HP will I actually gain ?,the system I am looking at quotes a gain of 15 hp.
3) If I fit a cat converter bypass will I have flat spot probs?
Paul
C2 cab
11-02-2003 | 09:43 AM
#2
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From: Highland Park, IL
Not sure about question 1, but take a look under the left rear fender. It it looks like this, you probably have a cat.
As for hp gains, probably not much. Only a before and after dyno can confirm any improvement, but my seat-of-the-pants experience suggest an improvement in low-end torque. It may not be an absolute gain but there seems to be more pull around 3,500 rpm. And no, I have not realized any flat spots.
Enjoy.
As for hp gains, probably not much. Only a before and after dyno can confirm any improvement, but my seat-of-the-pants experience suggest an improvement in low-end torque. It may not be an absolute gain but there seems to be more pull around 3,500 rpm. And no, I have not realized any flat spots.
Enjoy.
11-02-2003 | 02:10 PM
#3
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From: suffolk,england
Originally posted by joey bagadonuts
Not sure about question 1, but take a look under the left rear fender. It it looks like this, you probably have a cat.
As for hp gains, probably not much. Only a before and after dyno can confirm any improvement, but my seat-of-the-pants experience suggest an improvement in low-end torque. It may not be an absolute gain but there seems to be more pull around 3,500 rpm. And no, I have not realized any flat spots.
Enjoy.
Not sure about question 1, but take a look under the left rear fender. It it looks like this, you probably have a cat.
As for hp gains, probably not much. Only a before and after dyno can confirm any improvement, but my seat-of-the-pants experience suggest an improvement in low-end torque. It may not be an absolute gain but there seems to be more pull around 3,500 rpm. And no, I have not realized any flat spots.
Enjoy.
Paul
C2 cab
11-02-2003 | 02:31 PM
#4
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From: Highland Park, IL
I believe it is worthwhile and when used in conjunction with a dyno-tuned chip may deliver improved hp but I would consult a real expert if that's your aim. I'm very happy with this mod and feel it does deliver improved 0-60 performance, but again that may be due to an extended torque range as opposed to an increase in torque or hp.
11-03-2003 | 05:04 AM
#5
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From: London, UK
Paul
The only way to know for sure is to dyno the car before you do it and afterwards - there is no other way. Some chip and catbypass solutions do ake some gains, others don't. Why not consider a proven expensive solution, rather than gambling on whether the cheap mods actually give you anything at all?
I am sure there are other owners out there who have spent literally thousands on a resonably cheap mod here, or some trick induction filter there and not actually gained much at all over the years.
I think if your CAT is shot, do the mod as we don't need them on cars here in the UK made before 1993. It also does add more engine noise which may also be desirable. The gains can only be proved on the dyno.
The only way to know for sure is to dyno the car before you do it and afterwards - there is no other way. Some chip and catbypass solutions do ake some gains, others don't. Why not consider a proven expensive solution, rather than gambling on whether the cheap mods actually give you anything at all?
I am sure there are other owners out there who have spent literally thousands on a resonably cheap mod here, or some trick induction filter there and not actually gained much at all over the years.
I think if your CAT is shot, do the mod as we don't need them on cars here in the UK made before 1993. It also does add more engine noise which may also be desirable. The gains can only be proved on the dyno.
11-05-2003 | 04:30 AM
#7
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From: London, UK
Paul
Your question is very difficult to answer. I don't think anyone has ever carried out a test of which ones have the best sound, most gains and all that and for obvious reasons. I think most people just go for the cheapest they can find as it is at the end of the day just a pipe.
One thing to consider. If you don't have a CAT anymore, then you do not need the O2 or lambda sensor. The solution that I used (in a slightly digfferent application of course) was to jumper the DME so that it does not register any input from the O2 sensor and instead have an altitiude sensor installed instead (I think it is under one of the front seats?) so that at least the engine can take into account this aspect of fuelling.
I am sure others who have done this can advise you further.
Your question is very difficult to answer. I don't think anyone has ever carried out a test of which ones have the best sound, most gains and all that and for obvious reasons. I think most people just go for the cheapest they can find as it is at the end of the day just a pipe.
One thing to consider. If you don't have a CAT anymore, then you do not need the O2 or lambda sensor. The solution that I used (in a slightly digfferent application of course) was to jumper the DME so that it does not register any input from the O2 sensor and instead have an altitiude sensor installed instead (I think it is under one of the front seats?) so that at least the engine can take into account this aspect of fuelling.
I am sure others who have done this can advise you further.
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11-05-2003 | 04:58 AM
#8
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From: WhippetWorld, .........is it really only this many
The small gains likely from a cat-bypass won`t even be easy to pick up using a before and after dyno run due to the variables inherent in arriving at the power figures; and it`s all to easy for the operator to pull a fast one and show a gain if they are selling you the part.
Anecdotal and theoretical evidence suggests there will be a small gain in power of the magnitude of 5bhp, more if the cat is blocked.
What is certain is that you will lose unnessacery weight and won`t be running the risk of running a blocked cat ever.
Its a popular mod that most tinkerers do and I can`t recall anyone putting the cat back on if they didn`t have to.
The catbypass is just a SS tube so as long as there is a warrenty buy the cheapest.
Anecdotal and theoretical evidence suggests there will be a small gain in power of the magnitude of 5bhp, more if the cat is blocked.
What is certain is that you will lose unnessacery weight and won`t be running the risk of running a blocked cat ever.
Its a popular mod that most tinkerers do and I can`t recall anyone putting the cat back on if they didn`t have to.
The catbypass is just a SS tube so as long as there is a warrenty buy the cheapest.
11-05-2003 | 05:39 AM
#9
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From: Leeds, where I have run into this many lamp
Dove
if you like it 'low & loud' get a cat bypass & g-pipe(seondary bypass). It is very grumbly loud, will remove about 20kg from the back of the car and is an easy DIY. You should buy a set o new exhaust nuts & bolts (unless they come supplied with thte bypasses. IF not, they are £3.76 for each nut/bolt/washer set from Porsche.
www.type-911.co.uk (no affiliation) is a good supplier of these sorts of things.
My car already had cat bypass when I bought it. I just fitted G-pipe. I have noticed an improvemnt in power delivery with the g-pipe - not more power, but seems a bit smoother.
if you like it 'low & loud' get a cat bypass & g-pipe(seondary bypass). It is very grumbly loud, will remove about 20kg from the back of the car and is an easy DIY. You should buy a set o new exhaust nuts & bolts (unless they come supplied with thte bypasses. IF not, they are £3.76 for each nut/bolt/washer set from Porsche.
www.type-911.co.uk (no affiliation) is a good supplier of these sorts of things.
My car already had cat bypass when I bought it. I just fitted G-pipe. I have noticed an improvemnt in power delivery with the g-pipe - not more power, but seems a bit smoother.
