RoadrunnerGTS

ECU has power/torque estimation and calculation based on inputs... air, fuel, load, boost. No way ECU can determine the effect of exhaust mods, except indirectly for example catless headers which will cause the engine to run leaner and result in ECU attempt to compensate via O2 sensors. Janko's claim is pure uneducated nonsense from another YouTube "expert". Ask any reputable tuner and they will confirm this.

2seats

Didn’t read the thread but OMG that color with those wheels! Absolutely amazing looking GT4!

JCR-Porsche

I have to say that I think it’s a shame that you’re allowing a dyno print out from a test with a huge number of inconsistencies / issues to taint your overall experience of the exhaust modifications.

From the video we can see no intake fans, non linked Dyno, no PIWIS, no Dyno mode, different day, different conditions, higher humidity etc etc etc

Simply repositioning fans one run to the next can net a 10hp swing in results on the 718 GT4 / Spyder and running running no fans at all on the side intakes will see AIT’s rocket within the first full run alone, the car will almost immediately start pulling ignition and any data gathered will not be anywhere near representative of real world results.

Anyone who has tested these cars seriously will attest to that and this, in fact I think Jamie @ Dundon made a big post / video specifically about it. Those guys complete huge amounts of Dyno work and have their own in house Dyno.

We work very hard to be as transparent with our data as possible and recently took lots of time to demonstrate real world performance gains with acceleration data and video as we appreciate that Dyno data on it’s own must be taken with a pinch of salt.

As you mention above Kenny is a very experienced guy within the industry and he confirms that the 10% humidity change alone will have a negative effect. He mentions 3/4hp loss to be expected thanks to this alone, add that to the 3hp gained and factor in super high AIT’s then you start to built a different picture quite quickly.

Really wish you the best of luck with your YouTube channel and thank you for taking your time to share your specific experience but I would really recommend getting yourself a Dragy and forming your opinions based on real world acceleration data gathered on the same day / piece of road. I’m sure you’ll quickly find that your exhaust is performing just as nicely as it sounds in that video

JC

Reedy

Clickbait crap.

unclemat

Isn't that kinda expected? Less back pressure, lower gas velocity hurts mid range but opens up the top?

Never been believer in aftermarket exhausts. They may sound better? Sure. Will they perform better? Big maybe.

Zhao

As others have said conditions can be huge in HP fluctuations.

In one of my turbo cars there is a straightaway on a track i'll usually hit 162kph consistently in my first session of the day (when the car isn't heat soaked yet). On a hot day when the car starts to heat soak badly I'll drop to as low as 150kph on that straight. In fall when it was 15 degrees out I hit 165kph.

To compare dyno sheets you really need same air conditions same air setup same day same dyno type of stuff and even then it's not 100% a fair comparison.

horns

Engines are air pumps. Change parts to move more air and you can make more power (theoretically). The ecu knows how much air the pump is moving.

edub

For modern cars it seems like you'd want all engine data from each dyno run as well in order to properly assess that runs are comparable. Between days the car could easily be pulling timing, changing A/F ratios or any other manner of systems that could affect the measured power output.

Recall story about the Bugatti owner that couldn't unlock the top speed feature on a given day? Something about air temperature being off and the car said 'not today'.

That said - I do think a delta of 24hp is quite a lot. I wouldn't be happy.

daaa nope

I used to work for a manufacturer, writing engine control software. This was a few years ago now (I was writing stuff for a 2003 engine program), but the tech was there back then. Just because you can't see it in a service tool (the service tools don't show EVERYTHING - they're meant for service, not for reverse-engineering) doesn't mean it's not there. The DME can definitely get an idea on the power the vehicle is producing, and whether or not it is producing more or less. It knows how much fuel it's throwing in, knows how much air it's ingesting, how cleanly it's burning, what gear it's in, and how rapidly it's accelerating.

I'm not saying they are doing anything. But I'm saying it's entirely possible. Though I would suspect, IF they were doing such a thing - they would only be doing it if they detected a change in emissions. Though then in that case, I'd also very much expect a CEL to be set.

groundhog

Paper filters and cat back exhausts give you little - other than "improved" sound.

JCviggen

Except that with exhaust mods you're not moving more air so much as reducing pumping losses. How does an ECU measure pumping loss? I'll wait.

Also, our car do not have air flow sensors. They calculate air flow from the MAP plus stuff like Pbaro, IAT, engine speed and fixed values that were based on the stock car's characteristics. It works fine with a modified exhaust because the airflow into the engine actually changes very little. But the ECU can be effectively slightly "wrong" about the amount of air it ingests if you change anything that is necessarily defined by a fixed value. The slight correction required is taken care of by the wideband o2 sensors in the exhaust, but it's a very small correction that is easily within the tolerance allowed.

With less backpressure he ECU will have an easier time running more timing (it cannot distinguish the mods from good fuel in this case) but most of the power is simply "made" by not losing it to shoving the exhaust gases out through a straw.

There are certainly ways that different cars with different configurations that would have an easier time catching on but that's not really the point in this case.

4lflat6

What is the proof of this "real world performance" that I am missing? other than one dyno test posted by JCR there is absolutely no other data points that I am aware of. All straight line draggy performance data is for the full system with headers and not just the back box. The same "fairly primitive" dyno setup showed 30hp gains for the SOUL system.

3rd gear I believe (not 100% sure). Single Axle dyno. The dashboard lights up like a Christmas tree as you pointed out.

AND IT WORKED!! how do you think I was able to afford the car?

So a few things to your response:

1) the guy sitting in the car is Kenny, who you just mentioned is a very experienced guy in the industry. He is sitting there with PIWIS while running the dynos.
2) The fan positions may not be ideal but is consistent in before and after tests so should not impact the delta
3) Same dyno machine showed 30hp gain on SOUL system. if you go to their website, the performance numbers are from Jotech, the very same dyno machine you are bashing
4) I do not have draggy but I did a whole bunch of 0-60 launches using aimsolo. With factory exhaust I was able to do 3.97 after 3-4 tries. With JCR Exhaust in multiple days, I was not able to break below 4.2 after several tries.
5) You mentioned "real world performance data". There is no such thing with only the back box/muffler/race pipe. Only with the full system. Can you share that "real world performance" data of only the backbox with me like I asked in my email before you ignore me? I will wait.
6) I really do not need good luck with the youtube channel, this is not a get rich quick scheme and I make enough money to not need that side hustle. I am simply sharing my DIYs projects. No vlogs, no BS. If you are implying that is a "click bait" you are way off base

JCviggen

There's lots of people running exhausts on their cars on track, they're faster and stay faster. There is no need to single out JCR or Soul because the gains will be basically the same as all they free up the flow basically the same. It's all 2.5 inch piping bent into a roughly similar shape.

The fact that dyno showed +30 for the Soul system (which does ditch the stock restrictive OPF pipe) if anything makes me doubt its general accuracy. Soul have since publicly posted another customer on a different dyno which gained like 18 with the same exhaust. My own testing showed +26 crank HP on a state of the art dyno for a _full_ exhaust line with Soul race headers and valved exhaust.

I mean, don't get me wrong, any and all testing is welcome but extraordinary claims require extraordinary evidence and there are too many possible explanations for a skewed result here to simply throw out everything we established previously. We can't discount the issue with the exhaust on your car but it's not sufficient on its own to prove anything either. 0-60 runs also don't really work as they are so dependent on traction.

JCR-Porsche

1. Logging AIT’s or at least being aware of them should be very simple in that case, is that something that was considered or measured?

2. Consistency (no side air intake fans) between the before & after tests doesn’t take away the issue mentioned above. It will definitely impact results because you’re introducing a factor which you will not encounter in the real world unless you almost entirely blocked the side vents.

3. Comparing a header back exhaust to a rear silencer replacement on a different car, 9 months ago really bares no relevance at all. No bashing here, just presenting factors that can lead to skewed results, I’m trying to help.

4. 100-200kph acceleration data is the test to use to compare before after but again these really need to be completed on the same piece of road (we use track) and with conditions as close as possible too. 0-60mph is way more to do with the launch than anything else.

5. If our rear silencer ‘loses’ power then we certainly wouldn’t be posting the times that we are, we’re actually quite a long way ahead and we have data from our race manifolds / OPF delete with stock rear and race manifolds / OPF delete with JCR rear and there is a very distinct gain in performance.

5.1. In regards to stock vs rear box only 100-200kph data this is something that I will be able to gather in the next few weeks with the next willing customer car we have in, no issues, I’ll share on this thread ASAP.

6. Again, I was trying to be polite, very happy that you’re successful and earning lots of money. I think you’re getting the wrong end of the stick with a number of responses on this thread. You have to be reasonably open to criticism when presenting this kind of information in this way.

JC

Archimedes

Simple solution to this OP. Find someone local with a stock car to run them back to back on the dyno on the same day, being careful to match fuel, pressures, etc. Porsche tolerances are very tight on their motors, so the stock baselines should be similar.