Dyno Comparison: Catless Xpipe VS stock pipe/cats!!
02-18-2012, 04:54 PM
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Dyno Comparison: Catless Xpipe VS stock pipe/cats!!
Hi there
So a friend also has a sorted 911 like my own and managed to get hold of a catless X-Pipe, I believe its a fabspeed unit without cats.
His car is a 997.1 C2S with following mods:-
1. BMC Panel filter
2. Fabspeed Silicone tube and cap.
3. Resonator removed from airbox.
4. X51 Headers
5. Softronic map
6. PSE
Car made 376BHP with the above at flywheel.
Stock cats and pipes were then removed, battery was disconnected during this and it took just over a couple of hours to remove stock pipes and cats, fitting of X-pipe was fiddly, hardest part feeding the lambda sensors through but some metal wire helped with this.
Battery was re-connected and car was driven for a good 50 miles or so to ensure the ECU had fully adapted to the changes.
I've driven the car previously and we both took the car down a well known stretch of road and noticed the following things including one issue:-
1. Hesitation/jerk when applying throttle to heavy sub 1800rpm, you have to accelerate very very gently to avoid it otherwise you got was could amost be described as a hesitation/misfire, this was not present until fitting the x-pipe, so is definetely caused by this modification, its either the xpipe design or the lack of back pressure from having no cats.
2. Car feels sluggish between 2500-4000rpm, very noticable.
3. Car feels and pulls way way harder beyond 4200rpm and seems to accelerate far harder once beyond 5000rpm, very noticably.
4. The noise, easily twice as loud, if not even more so, noise at idle is far nicer, but at high-revs it just seems plain loud, almost CUP car loud.
5. No apparant change to MPG and no bad smells.
Here is the result:-
The results seem to co-incide with what was felt during driving, the dyno operator also looked at the hesitation down low and said its probably the softronic map needing more custom mapping to dial it out or its just an issue with lack of back pressure, but my friend has since put a further 200 miles on the car today and it is still doing it.
Look at the graph in detail and you will see a major torque loss in the 2500-4000rpm region, infact the loss is as high as 40lb/ft and 30BHP, no wonder we could feel it.
However from 4200rpm things change for the better, torque is 20lb/ft better in the 4500-5000rpm region, but between 5500-6500rpm there is nearly 40lb/ft more. Peak power is up by approx 12BHP, but this does not paint the entire picture as 5500-6500rpm power is up by nearly 35BHP. This we were definetely feeling on our drives.
So in short a de-catted X-pipe does loose you considerable torque and power sub 4000rpm, which contradicts what the manufacturers of X-pipes say, as Fabspeed for instance claim no loss of torque down low for their catless X-pipe, this is clearly untrue as proven here. However there are some great gains to be had in the upper part of the RPM bands which is also very noticable.
In summary this is a great mod if you do a lot of DE events or circuit/track work, you will be faster for sure as long as you keep RPM's beyond 4000rpm and don't get sent home for breaking any noise limits.
On a road car though, well both me and my mate were not impressed, though we liked the top-end power, we were both missing the low-down power we had lost and the hesitation we were and still getting spoiled things further, then add the volume of noise and the fact it seems less exotic I think I shall soon be helping my mate to remove this mod.
However this does make me wonder, would some 200 cel cats be the perfect resolution to this? Those who have fitted 200 cel cats, did or do you think you lost any low down power/torque? Any hesitation issues with 200 cel cats? If a vendor wants to do us a deal or loan us any 200 cel cats we'd happily put the car on the dyno again and add the results to the comparison. Would be great to avoid that loss of power/torque down load, reduce the noise and hold onto the power gains, could 200 cel cats do this?
So a friend also has a sorted 911 like my own and managed to get hold of a catless X-Pipe, I believe its a fabspeed unit without cats.
His car is a 997.1 C2S with following mods:-
1. BMC Panel filter
2. Fabspeed Silicone tube and cap.
3. Resonator removed from airbox.
4. X51 Headers
5. Softronic map
6. PSE
Car made 376BHP with the above at flywheel.
Stock cats and pipes were then removed, battery was disconnected during this and it took just over a couple of hours to remove stock pipes and cats, fitting of X-pipe was fiddly, hardest part feeding the lambda sensors through but some metal wire helped with this.
Battery was re-connected and car was driven for a good 50 miles or so to ensure the ECU had fully adapted to the changes.
I've driven the car previously and we both took the car down a well known stretch of road and noticed the following things including one issue:-
1. Hesitation/jerk when applying throttle to heavy sub 1800rpm, you have to accelerate very very gently to avoid it otherwise you got was could amost be described as a hesitation/misfire, this was not present until fitting the x-pipe, so is definetely caused by this modification, its either the xpipe design or the lack of back pressure from having no cats.
2. Car feels sluggish between 2500-4000rpm, very noticable.
3. Car feels and pulls way way harder beyond 4200rpm and seems to accelerate far harder once beyond 5000rpm, very noticably.
4. The noise, easily twice as loud, if not even more so, noise at idle is far nicer, but at high-revs it just seems plain loud, almost CUP car loud.
5. No apparant change to MPG and no bad smells.
Here is the result:-
The results seem to co-incide with what was felt during driving, the dyno operator also looked at the hesitation down low and said its probably the softronic map needing more custom mapping to dial it out or its just an issue with lack of back pressure, but my friend has since put a further 200 miles on the car today and it is still doing it.
Look at the graph in detail and you will see a major torque loss in the 2500-4000rpm region, infact the loss is as high as 40lb/ft and 30BHP, no wonder we could feel it.
However from 4200rpm things change for the better, torque is 20lb/ft better in the 4500-5000rpm region, but between 5500-6500rpm there is nearly 40lb/ft more. Peak power is up by approx 12BHP, but this does not paint the entire picture as 5500-6500rpm power is up by nearly 35BHP. This we were definetely feeling on our drives.
So in short a de-catted X-pipe does loose you considerable torque and power sub 4000rpm, which contradicts what the manufacturers of X-pipes say, as Fabspeed for instance claim no loss of torque down low for their catless X-pipe, this is clearly untrue as proven here. However there are some great gains to be had in the upper part of the RPM bands which is also very noticable.
In summary this is a great mod if you do a lot of DE events or circuit/track work, you will be faster for sure as long as you keep RPM's beyond 4000rpm and don't get sent home for breaking any noise limits.
On a road car though, well both me and my mate were not impressed, though we liked the top-end power, we were both missing the low-down power we had lost and the hesitation we were and still getting spoiled things further, then add the volume of noise and the fact it seems less exotic I think I shall soon be helping my mate to remove this mod.
However this does make me wonder, would some 200 cel cats be the perfect resolution to this? Those who have fitted 200 cel cats, did or do you think you lost any low down power/torque? Any hesitation issues with 200 cel cats? If a vendor wants to do us a deal or loan us any 200 cel cats we'd happily put the car on the dyno again and add the results to the comparison. Would be great to avoid that loss of power/torque down load, reduce the noise and hold onto the power gains, could 200 cel cats do this?
02-18-2012, 05:05 PM
#2
Rennlist Member
Great dyno and write-up, love to see some real testing to challenge claims made by aftermarket mods.
Our cars are quite complicated now, and very well engineered to work with exact parts in the car, and just changing one part here or there is NOT going to give you pure gains unless the ECU is designed for such change.
Our cars are quite complicated now, and very well engineered to work with exact parts in the car, and just changing one part here or there is NOT going to give you pure gains unless the ECU is designed for such change.
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10-09-2016, 11:48 PM
#8
Full AWE setup for past 8 years. Came w HKS 200 cell cats. Torque curve moved down and car pulls really strong from 3000rpm to redline. There is no loss I notice below and above, just a more enjoyable motor over the road and nice sound. 3rd and 4th gears are scary fast even after all these years. For past few years I get a cel for cat insufficiency. No effect on drivability but must be cleared and driven before inspections. Imo this is the way to go.
10-09-2016, 11:56 PM
#9
Re above: can't edit posts, why?
Anyway I should add that car has IPD racing plenum, GT3 throttle body and Revo flash in addition to the AM exhaust. 200 cell cats imo do not limit performance and enhance drivability. Just look for high quality German production part
Anyway I should add that car has IPD racing plenum, GT3 throttle body and Revo flash in addition to the AM exhaust. 200 cell cats imo do not limit performance and enhance drivability. Just look for high quality German production part
