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GTS Dyno run before and after results, catless downpipes, full exhaust system
Hi Guys,
Did few dyno runs and was surprise with the results. i bought the GTS used and im not sure if the previous owner tuned it, as the results was shocking. By today i should know by my local tuner wether the car is tuned or not. 521hp at the wheels and 640nm of torque can't be stock can it? Environment temperature was 34C/93F.
Last edited by torquecraz; Aug 9, 2022 at 11:43 PM.
It will be interesting to hear this setup, but not sure what you were after with exhaust. One of the best sounding stock systems out there with a 2nd cat delete. Tips are cool. You might want to add H pipe section in center pipes.
I am not sure about a tune, maybe if at the rear wheels. looks too light to me as a stage 1 tune should add more than that. But interesting to see what you find out.
Last edited by Acta_Non_Verba; Aug 10, 2022 at 11:08 AM.
@torquecraz: Thanks for the report and the pictures.
The performance diagram are 2 measurements without tune?
Shure, its the wheel power?
The GT models are known to scatter upwards. Have had this experience myself.
Factory specification GTR (Germany):
585PS / 700Nm at crankshaft.
First measurement at approx. 90F air temperature, definitely no ECU Tune, no high oktane fuel,
only K&N / 2nd Cat Delete. (both max. + 20PS)
650PS / 850Nm at crankshaft.
MY PERSONAL OPINION on retrofit downpipes and exhaust systems:
(No general law and no declaration of war :-) )
Catless downpipes:
You have to code out the 1st cat.
Most with smaller turbo elbows.
Know of 2 cases where catless downpipes was installed.
Then an additional sports cat was subsequently welded in again.
The reason was that both without cats stank terribly????
Very expensive result: rather worse than 2nd cat delete.
Downpipes with sport cat in the same place of the stock 2nd cat.
You have to code out the 1st cat.
Also with a smaller diameter cat and tupes and turboelbows (see below)
The location of the stock 1st cat is the better place. (More pressure)
Expensive result: rather worse than 2nd cat delete.
Downpipes with sport cat e.g. 200 cells, in the same place of the stock 1st cat.
(think stock is 400 cells, unchecked)
So far, all the ones I know had a smaller diameter and a less favorable input and output funnel (turbo elbows) than stock.
This compensates the larger free individual cross-sections. The "pressure gain" shouldn't be much better.
Expensive result: rather worse than 2nd cat delete.
Fakts:
The original AMG Kats are big and very high quality lightweight (perforated foils) metalcats with 3 winding centers.
The best construction for cats thats currently available.
Input and output funnels are optimally shaped with bigest possible diameter.
In addition, there are the insulated,double-walled housings and funnels.
No aftermarket downpipe can offer that.
That should (especially in the hot V) lowers the temperature.
The stock downpipes are partially insulated. (firewall / torque tube)
Most aftermarket downpipes also lack this.(Not there above)
Didn't want that way.
Performance gain by catless downpipes, without further extreme engine conversions, is also not in a good proportion.
(10 - 30 HP depending on the engine version)
Especially in comparison with a 2nd cat delete.
2 cat delete does not bring high additional performance gain.
But it is noticeable in the exhaust tone (even more so, with European OPF) and by far, the best price / performance ratio of all versions.
Aftermarket exhaust systems:
For me, with a GT, that's wasted money. What is the advantage here?
In the example above you can see very well, how unfavorable the aftermarket system was made for flow.
Even with 100% open flaps. (see the 90 degrees in and outs)
The stock exhaust is better built. Almost straight passages.
Even with small details, such as the funnels on the endpipes.
Do the tubes have the same inside diameter?
Could be wrong here, but it looks a bit smaller. That would be bad then.
It also lacks the H-pipe (the second stock "H-pipe" is not connected, is just a mechanical stabilization)
Simplified: H-pipe is the best for maximum low-end and overall performance gain.
Simplified: X-Pipe is for HP peak at high RPM. (Maybe for Racetrack?)
True dual exhaust is definitely, the worst idea. Wasted potential.
Don't think there is anything to improve on the stock exhaust.Especially when the flaps are open.
Maybe at > 1000hp :-)
Muffler:
A muffler that is supposed to dampen and sound deep, always needs big volume.
This aftermarked muffler is also (estimated 50%?) smaller.
Maybe this exhaust system is a little louder when the flaps are partially closed?
This can be done with a flap module. Then stock exhaust is max. loud and cheaper.
And can still be freely selected (also quiet) at any time.
2. cat delete, flap control. Don't need more.
If you could measure stock exhaust and both mod versions in real terms,
Would expect the following: With 2.cat delete and stock exaust there will be a small performance gain.(10 - 20hp) Catless and this aftermarket exaust sytem will be, +- around stock performance.
As I said, my personal opinion.
Don't want to speak anything bad and don't claim to be the only truth.
Best regards
Stenzel
Last edited by Stenzel-Germany; Aug 10, 2022 at 09:19 PM.
Reason: words
Can you answer the question about the dyno results HJZ asked in post #6? Is the chart comparing pre and post exhaust install?
The title of the thread says that, therefore I assume it is. If so, it is good data that the CATS vs. CATLESS is only giving a handful of extra HP which some of us have been saying all along. In this case looks like about 8 HP?
I agree with Stenzel, the factory CATS are high quality. In other platforms in which I've tuned, I've seen about the same results removing CATS, even some of the earlier designs from other manufacturers, but CATS on many platforms perform pretty well and are less restrictive than the ones first introduced.
This would be a good thread to earmark for posterity.
It will be interesting to hear this setup, but not sure what you were after with exhaust. One of the best sounding stock systems out there with a 2nd cat delete. Tips are cool. You might want to add H pipe section in center pipes.
Yes you are right it is tuned stage 1, my local tuner just confirm with me by checking the ECU. the previous owner just remap the ecu only nothing else. downpipe and exhaust as stock. as is why im changing the whole exhaust system because the present stock ones are rusted and i wanted to use catless downpipe. its a 2015 model so is about time to change it anyway. the new exhaust has been ordered and installed so not going for the H pipe. Tks for the advice.
Looks to be tuned. Is that first graph with both runs for before or after? Or is it just 2 runs of the before?
yes it is tuned stage 1. is just 2 runs not before and after. will show you guys the after results when the car is remap and installations of the full exhaust system.
@torquecraz: Thanks for the report and the pictures.
The performance diagram are 2 measurements without tune?
Shure, its the wheel power?
The GT models are known to scatter upwards. Have had this experience myself.
Factory specification GTR (Germany):
585PS / 700Nm at crankshaft.
First measurement at approx. 90F air temperature, definitely no ECU Tune, no high oktane fuel,
only K&N / 2nd Cat Delete. (both max. + 20PS)
650PS / 850Nm at crankshaft.
MY PERSONAL OPINION on retrofit downpipes and exhaust systems:
(No general law and no declaration of war :-) )
Catless downpipes:
You have to code out the 1st cat.
Most with smaller turbo elbows.
Know of 2 cases where catless downpipes was installed.
Then an additional sports cat was subsequently welded in again.
The reason was that both without cats stank terribly????
Very expensive result: rather worse than 2nd cat delete.
Downpipes with sport cat in the same place of the stock 2nd cat.
You have to code out the 1st cat.
Also with a smaller diameter cat and tupes and turboelbows (see below)
The location of the stock 1st cat is the better place. (More pressure)
Expensive result: rather worse than 2nd cat delete.
Downpipes with sport cat e.g. 200 cells, in the same place of the stock 1st cat.
(think stock is 400 cells, unchecked)
So far, all the ones I know had a smaller diameter and a less favorable input and output funnel (turbo elbows) than stock.
This compensates the larger free individual cross-sections. The "pressure gain" shouldn't be much better.
Expensive result: rather worse than 2nd cat delete.
Fakts:
The original AMG Kats are big and very high quality lightweight (perforated foils) metalcats with 3 winding centers.
The best construction for cats thats currently available.
Input and output funnels are optimally shaped with bigest possible diameter.
In addition, there are the insulated,double-walled housings and funnels.
No aftermarket downpipe can offer that.
That should (especially in the hot V) lowers the temperature.
The stock downpipes are partially insulated. (firewall / torque tube)
Most aftermarket downpipes also lack this.(Not there above)
Didn't want that way.
Performance gain by catless downpipes, without further extreme engine conversions, is also not in a good proportion.
(10 - 30 HP depending on the engine version)
Especially in comparison with a 2nd cat delete.
2 cat delete does not bring high additional performance gain.
But it is noticeable in the exhaust tone (even more so, with European OPF) and by far, the best price / performance ratio of all versions.
Aftermarket exhaust systems:
For me, with a GT, that's wasted money. What is the advantage here?
In the example above you can see very well, how unfavorable the aftermarket system was made for flow.
Even with 100% open flaps. (see the 90 degrees in and outs)
The stock exhaust is better built. Almost straight passages.
Even with small details, such as the funnels on the endpipes.
Do the tubes have the same inside diameter?
Could be wrong here, but it looks a bit smaller. That would be bad then.
It also lacks the H-pipe (the second stock "H-pipe" is not connected, is just a mechanical stabilization)
Simplified: H-pipe is the best for maximum low-end and overall performance gain.
Simplified: X-Pipe is for HP peak at high RPM. (Maybe for Racetrack?)
True dual exhaust is definitely, the worst idea. Wasted potential.
Don't think there is anything to improve on the stock exhaust.Especially when the flaps are open.
Maybe at > 1000hp :-)
Muffler:
A muffler that is supposed to dampen and sound deep, always needs big volume.
This aftermarked muffler is also (estimated 50%?) smaller.
Maybe this exhaust system is a little louder when the flaps are partially closed?
This can be done with a flap module. Then stock exhaust is max. loud and cheaper.
And can still be freely selected (also quiet) at any time.
2. cat delete, flap control. Don't need more.
If you could measure stock exhaust and both mod versions in real terms,
Would expect the following: With 2.cat delete and stock exaust there will be a small performance gain.(10 - 20hp) Catless and this aftermarket exaust sytem will be, +- around stock performance.
As I said, my personal opinion.
Don't want to speak anything bad and don't claim to be the only truth.
Best regards
Stenzel
Its tuned to stage 1. will show the dyno results after i have remap, install downpipes and full exhaust system. should be ready by tommorrow. tks for the advice.
Last edited by torquecraz; Aug 10, 2022 at 10:20 PM.
Can you answer the question about the dyno results HJZ asked in post #6? Is the chart comparing pre and post exhaust install?
The title of the thread says that, therefore I assume it is. If so, it is good data that the CATS vs. CATLESS is only giving a handful of extra HP which some of us have been saying all along. In this case looks like about 8 HP?
I agree with Stenzel, the factory CATS are high quality. In other platforms in which I've tuned, I've seen about the same results removing CATS, even some of the earlier designs from other manufacturers, but CATS on many platforms perform pretty well and are less restrictive than the ones first introduced.
This would be a good thread to earmark for posterity.
Thanks,
The chart shows stage 1 tuned (with stock downpipe and exhaust) by the previous owner of the car as i bought it used. i agree with Stenzel but removing the Cat gives about 10%-15% louder sound and gives better air flow.
the after dyno results will be posted as soon as the car have been remap and complete installation of the catless downpipe with full exhaust system to stage 2. i would not want to assume how many hp gain, will just wait for the dyno after results. should be ready in 1 or 2 days so stay tune guys
If possible, please make the first run, with the same tune.
That would be an interesting comparison.
Thanks.
Best regards
Stenzel
Yes, I agree with Stenzel, these would be good data.
torquecraz,
Based on how you are going to tune it (hand held, etc.) it would be very easy to do a Dyno pull, then add the tune, then another Dyno pull. It will give a number of valuable results.
Hi guys,
this is the vdo dyno run i did stage 1 with stock downpipe and stock exhaust. i could not do a dyno run with the car completely stock because the previous owner already remap to stage 1.
please take note that this is the result and graph that you guys saw on the first post.
Best Dyno Results stage 2 remap, catless downpipe and full exhaust system installed
Hi Guys,
Car is finally ready, took a bit of time to install the downpipes and the full exhaust system. below is the vdo of the dyno final run. Torque and boost limiter are still able to play safe.
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