Fabspeed Catbypass pipes

[phillipj]

Just wanted to pass some informatiion to anyone whos is thinking about the cat bypass pipes. My car has the Fabspeed chip, mufflers and cold air intake. The Cat pipes are supposed to add some HP and torque but on my car they add neither. The car is not as quick as it was without the pipes.

I like a loud car but the sound is really obnoxious. It has a terrible resonance around 4000 rpm. I have tracked the car before the bypass pipes and it is much quicker (without the pipes) and the power is more usable.

With pipes it seems to maybe have a bit more power at the top end but no grunt coming out of corners. :cursing:

This is my first Porsche. Does the ECU have to be remapped without the cats?

This is not a shot at Fabspeed. I love all the other products I have bought from them.

Any insight from anyone out there would be greatly appreciated.

Thanks

Phillipj

[ianwallwork]

Just wanted to pass some informatiion to anyone whos is thinking about the cat bypass pipes. My car has the Fabspeed chip, mufflers and cold air intake. The Cat pipes are supposed to add some HP and torque but on my car they add neither. The car is not as quick as it was without the pipes.

I like a loud car but the sound is really obnoxious. It has a terrible resonance around 4000 rpm. I have tracked the car before the bypass pipes and it is much quicker (without the pipes) and the power is more usable.

With pipes it seems to maybe have a bit more power at the top end but no grunt coming out of corners. :cursing:

This is my first Porsche. Does the ECU have to be remapped without the cats?

This is not a shot at Fabspeed. I love all the other products I have bought from them.

Any insight from anyone out there would be greatly appreciated.

Thanks

Phillipj

Phillip

Removing the Cats has two major effects. First one is that the post-cat O2 (lambda) sensors are going to detect 'unclean' emissions - they usually are subjected to exhaust gasses that have been through the Cats and are 'cleaned' - this may well cause the ECU to go into some sort of safe mode due to it thinking your cats have failed. Second (and assuming that the first problem is properly resolved) removing the cats reduces exhaust back pressure as the volume of exhaust gas increases. (Even inefficient, standard cats will flow a small volume of gas without creating back pressure, the pressure starts to build as throttle/revs rise). This change in back presure will affect the scavenging of the combustion chamber (i.e. more exhaust gas will escape on each exhaust stroke) allowing more new mixture in. This is good and will theoretically allow more HP to be produced. HOWEVER.......

You now have an engine that is breathing and burning more effciently. This change in the engine's operating parameters means that your standard ignition timing will be way out. Ignition timing at full throttle depends, amongst other things, on the volumetric and burn efficiency of the engine at any given point in the rpm range. Typically an engine that is breathing and burning better requires a SHORTER ignition advance curve. That means the ignition needs to happen later in the cycle - yes, LESS timing. This is simply because a more efficient, cleaner burn happens more quickly and therefore needs to be ignited later for the maximum pressure to be applied to the piston at the optimal point on the power stroke.

The volumetric / timing-requirement differences made by removing the cats will not be huge (compared to say, gas-flowed heads and new cams) but could require a timing compenstation of up to 5 degrees or so. Using the standard mapping, you would notice this as slightly reduced power - and inconsistently so across the rev band. If you are noticing big power drops then there is something in the ECU shutting down / gong into safe mode because it senses cat failure.

In short then - if you make mods, you must have a re-mapped ECU designed to take account of EXACTLY those changes you have made. Mod + matching-ECU are an inseparable pair. Any mod renders the standard engine mapping wrong to a greater of lesser degree. And if you change something that takes a sensor out of its operating range, the sensor will need to be taken out of the loop in the ECU too - either deactivated or given a new set of expected values so it doesn't interfere with correct operation.

Hope this helps

Ian

[phillipj]

Just wanted to pass some informatiion to anyone whos is thinking about the cat bypass pipes. My car has the Fabspeed chip, mufflers and cold air intake. The Cat pipes are supposed to add some HP and torque but on my car they add neither. The car is not as quick as it was without the pipes.

I like a loud car but the sound is really obnoxious. It has a terrible resonance around 4000 rpm. I have tracked the car before the bypass pipes and it is much quicker (without the pipes) and the power is more usable.

With pipes it seems to maybe have a bit more power at the top end but no grunt coming out of corners. :cursing:

This is my first Porsche. Does the ECU have to be remapped without the cats?

This is not a shot at Fabspeed. I love all the other products I have bought from them.

Any insight from anyone out there would be greatly appreciated.

Thanks

Phillipj

Phillip

Removing the Cats has two major effects. First one is that the post-cat O2 (lambda) sensors are going to detect 'unclean' emissions - they usually are subjected to exhaust gasses that have been through the Cats and are 'cleaned' - this may well cause the ECU to go into some sort of safe mode due to it thinking your cats have failed. Second (and assuming that the first problem is properly resolved) removing the cats reduces exhaust back pressure as the volume of exhaust gas increases. (Even inefficient, standard cats will flow a small volume of gas without creating back pressure, the pressure starts to build as throttle/revs rise). This change in back presure will affect the scavenging of the combustion chamber (i.e. more exhaust gas will escape on each exhaust stroke) allowing more new mixture in. This is good and will theoretically allow more HP to be produced. HOWEVER.......

You now have an engine that is breathing and burning more effciently. This change in the engine's operating parameters means that your standard ignition timing will be way out. Ignition timing at full throttle depends, amongst other things, on the volumetric and burn efficiency of the engine at any given point in the rpm range. Typically an engine that is breathing and burning better requires a SHORTER ignition advance curve. That means the ignition needs to happen later in the cycle - yes, LESS timing. This is simply because a more efficient, cleaner burn happens more quickly and therefore needs to be ignited later for the maximum pressure to be applied to the piston at the optimal point on the power stroke.

The volumetric / timing-requirement differences made by removing the cats will not be huge (compared to say, gas-flowed heads and new cams) but could require a timing compenstation of up to 5 degrees or so. Using the standard mapping, you would notice this as slightly reduced power - and inconsistently so across the rev band. If you are noticing big power drops then there is something in the ECU shutting down / gong into safe mode because it senses cat failure.

In short then - if you make mods, you must have a re-mapped ECU designed to take account of EXACTLY those changes you have made. Mod + matching-ECU are an inseparable pair. Any mod renders the standard engine mapping wrong to a greater of lesser degree. And if you change something that takes a sensor out of its operating range, the sensor will need to be taken out of the loop in the ECU too - either deactivated or given a new set of expected values so it doesn't interfere with correct operation.

Hope this helps

Ian

Dear Ian,

Thank you so much for the information. It makes a lot of sense. So what am I talking about here? Firstly, who can re- map my ECU? Secondly, Is it worth it? (Since I will have to re -map the ECU again if I take them off.)

Thanks again,

Phillipj

[RedRidge]

Ive not heard of ecu map for cat bypass. Ive heard of remapping of cold air intake and exhuast mufflers. I would take it off, or you will have a better shot at hi flow cat pipes... no ecu remapping neccesary

[i300zxtt]

Are you getting a CEL? if so the car goes into safe mode and kills the performance. Get some 02 simulators or custom ECU programming.

[ianwallwork]

Ive not heard of ecu map for cat bypass. Ive heard of remapping of cold air intake and exhuast mufflers. I would take it off, or you will have a better shot at hi flow cat pipes... no ecu remapping neccesary

RedRidge

Using hi-flow (200-cell / 100-cell) cats requires a re-map to work properly for exactly the same reasons as a cat bypass. You are changing the operating parameters of the engine. If it flows more exhaust gas more easily as rpms and throttle openings increase then the timing requirement will be different. This effect will be less pronounced with free-flow cats than with a bypass as the increase in flow will be less. Whilst a properly re-mapped ECU will still bring the most benefit, the timing difference required may be small enough that you may still see (an albeit smaller) power increase with the standard map.

As an aside (and just to confuse everyone for a moment.....!) we also have no way of knowing how 'accurate' the standard mapping might be. If it is particularly conservative (normal with many manufacturers for reliabililty) the standard timings may even turn out to be closer to the optimal real-world requirement with free-flow cats / headers etc. at some points in the load vs rpm range. This cannot be relied on however and you will certainly get inconsistent results with a standard map and modified components.

What you DO gain by using high-flow cats is that the post-cat O2 sensors are now back in the loop correctly. I would recommend using 200-cell cats for road as they don't boom and resonate like 100-cells can.

Phillip

A worthwhile tuner will offer a range of packages that include known mods and an ECU to match. AFAIK, Fabspeed offers a range of modded ECUs to match their products. Please post the results back - it will be interesting to see how you get along.

Ian

Edited December 29, 2006 by ianwallwork

[jurichar]

ian,

what are your thoughts on an o2 simulator?!?

[phillipj]

Ive not heard of ecu map for cat bypass. Ive heard of remapping of cold air intake and exhuast mufflers. I would take it off, or you will have a better shot at hi flow cat pipes... no ecu remapping neccesary

RedRidge

Using hi-flow (200-cell / 100-cell) cats requires a re-map to work properly for exactly the same reasons as a cat bypass. You are changing the operating parameters of the engine. If it flows more exhaust gas more easily as rpms and throttle openings increase then the timing requirement will be different. This effect will be less pronounced with free-flow cats than with a bypass as the increase in flow will be less. Whilst a properly re-mapped ECU will still bring the most benefit, the timing difference required may be small enough that you may still see (an albeit smaller) power increase with the standard map.

As an aside (and just to confuse everyone for a moment.....!) we also have no way of knowing how 'accurate' the standard mapping might be. If it is particularly conservative (normal with many manufacturers for reliabililty) the standard timings may even turn out to be closer to the optimal real-world requirement with free-flow cats / headers etc. at some points in the load vs rpm range. This cannot be relied on however and you will certainly get inconsistent results with a standard map and modified components.

What you DO gain by using high-flow cats is that the post-cat O2 sensors are now back in the loop correctly. I would recommend using 200-cell cats for road as they don't boom and resonate like 100-cells can.

Phillip

A worthwhile tuner will offer a range of packages that include known mods and an ECU to match. AFAIK, Fabspeed offers a range of modded ECUs to match their products. Please post the results back - it will be interesting to see how you get along.

Ian

Thanks Ian. I will let everyone know what I find out. As of now the pipes are going back to Fabspeed.

Phillipj

[phillipj]

Ive not heard of ecu map for cat bypass. Ive heard of remapping of cold air intake and exhuast mufflers. I would take it off, or you will have a better shot at hi flow cat pipes... no ecu remapping neccesary

RedRidge

Using hi-flow (200-cell / 100-cell) cats requires a re-map to work properly for exactly the same reasons as a cat bypass. You are changing the operating parameters of the engine. If it flows more exhaust gas more easily as rpms and throttle openings increase then the timing requirement will be different. This effect will be less pronounced with free-flow cats than with a bypass as the increase in flow will be less. Whilst a properly re-mapped ECU will still bring the most benefit, the timing difference required may be small enough that you may still see (an albeit smaller) power increase with the standard map.

As an aside (and just to confuse everyone for a moment.....!) we also have no way of knowing how 'accurate' the standard mapping might be. If it is particularly conservative (normal with many manufacturers for reliabililty) the standard timings may even turn out to be closer to the optimal real-world requirement with free-flow cats / headers etc. at some points in the load vs rpm range. This cannot be relied on however and you will certainly get inconsistent results with a standard map and modified components.

What you DO gain by using high-flow cats is that the post-cat O2 sensors are now back in the loop correctly. I would recommend using 200-cell cats for road as they don't boom and resonate like 100-cells can.

Phillip

A worthwhile tuner will offer a range of packages that include known mods and an ECU to match. AFAIK, Fabspeed offers a range of modded ECUs to match their products. Please post the results back - it will be interesting to see how you get along.

Ian

Thanks Ian. I will let everyone know what I find out. As of now the pipes are going back to Fabspeed.

Phillipj

Just an update,

I have not been getting any ECU light which is strange. :( :huh: I'm going to take the car to my mechanic and have him hook up the PST 2 to see if any codes show up. I'll let everyone know what I find out.

Thanks for all the input I really appreciate it.

Phillipj

[Vman]

The right software map is in your porsche tech's Porshe System tester 2 it is called ROW software mode and does not look for the rear O2 sensor, also the program is a bit richer and matches really well with high flow 100 or 200 cel cats and high quality Scargo headers, we are seeing about 25 to 30 HP over stock, same set up running U.S. OBD 2 program had 20 hp less and when we tried a chip by one of the tuners it was even worse. Did you ever send the pipes back to Fabspeed as mentioned above, if not drop me a line as I would be happy to buy them and put them on a dyno to see what happens.

Ive not heard of ecu map for cat bypass. Ive heard of remapping of cold air intake and exhuast mufflers. I would take it off, or you will have a better shot at hi flow cat pipes... no ecu remapping neccesary

RedRidge

Using hi-flow (200-cell / 100-cell) cats requires a re-map to work properly for exactly the same reasons as a cat bypass. You are changing the operating parameters of the engine. If it flows more exhaust gas more easily as rpms and throttle openings increase then the timing requirement will be different. This effect will be less pronounced with free-flow cats than with a bypass as the increase in flow will be less. Whilst a properly re-mapped ECU will still bring the most benefit, the timing difference required may be small enough that you may still see (an albeit smaller) power increase with the standard map.

As an aside (and just to confuse everyone for a moment.....!) we also have no way of knowing how 'accurate' the standard mapping might be. If it is particularly conservative (normal with many manufacturers for reliabililty) the standard timings may even turn out to be closer to the optimal real-world requirement with free-flow cats / headers etc. at some points in the load vs rpm range. This cannot be relied on however and you will certainly get inconsistent results with a standard map and modified components.

What you DO gain by using high-flow cats is that the post-cat O2 sensors are now back in the loop correctly. I would recommend using 200-cell cats for road as they don't boom and resonate like 100-cells can.

Phillip

A worthwhile tuner will offer a range of packages that include known mods and an ECU to match. AFAIK, Fabspeed offers a range of modded ECUs to match their products. Please post the results back - it will be interesting to see how you get along.

Ian

Thanks Ian. I will let everyone know what I find out. As of now the pipes are going back to Fabspeed.

Phillipj

Just an update,

I have not been getting any ECU light which is strange. :( :huh: I'm going to take the car to my mechanic and have him hook up the PST 2 to see if any codes show up. I'll let everyone know what I find out.

Thanks for all the input I really appreciate it.

Phillipj

Edited March 5, 2007 by Vman