Jamie@dundonmotorsports

The Dundon through axles pipes on the 4RS are shorter, much shorter...

bantam1

Well then I guess the opposite curiosity applies then, I wonder if the shorter length will have an impact.

I had assumed when reading about your development of the 4RS wavy pipes that the resultant length was longer than the GT4.

Either way, good stuff, I am sure whatever you all come up with will be done well

BabyNSX

The sounds coming out of the stock muffler with Dundon headers and OAPs are already fantastic (especially with their pro-tune), but I suspect I'll be in for a very pleasant surprise once the new optimized muffler and tune gets installed and calibrated.

Yeah, it's been a bit of a wait, but the best things in life often are worth waiting for . Very much looking forward to seeing, hearing and feeling what further magic tricks the Dundon team performs on the GT4!

TRSCobra

Is yours Gig Harbor bound for the testing?

BabyNSX

Yup

GianniG60

@Jamie@dundonmotorsports
Jamie, thank you for the update on the rear muffler for the Spyder/GT4. If already running exhaust manifolds/OAP with 200cel cats, what do you anticipate the incremental horsepower gain would be with your new rear section (muffler)?
In other words, what would the horsepower gain be with adding the new muffler to your existing headers/OAP set up?

Jamie@dundonmotorsports

So couple things with this. The muffler will only work with our headers/OAP's. was a decision to ensure the most power was possible. We know the answer on the 4RS, and you all can find that on our website, is quite a kick. The physics holds for the 718 GT4 to get the same benefit and with some new maps opened up for us by Cobb, we will be able to take advantage of it.

I don't want to guess as that's why Doug's car is headed north to us this month!

Jamie

BabyNSX

She's headed your way Jamie!! Looking forward to seeing what you and the boys cook up for her

Avera

The worst part of watching my vehicles getting loaded into these trucks - and unloaded - is watching the driver try to get in/out of when there is no room for them to even open the door

Avera

BabyNSX

Yeah, I hear you... The driver definitely had monkey skills Honestly he was totally cool and showed a great deal of care for the car.

BabyNSX

Well, I will not spill the beans but the results are in from the Dundon team and the results I'm seeing and hearing are glorious... I suspect there will be some official updates from them soon ;-)

Here is a quick screen grab from the Whiskey Friday live stream this past week:


Those who have been patiently waiting will want to get in line to grab one of these

Avera

I have long moved on from the GT4 at this point . . . but I am still looking forward to 'hearing' the results

Avera

BabyNSX

With permission, here are the final results showing the significant improvements adding the rear muffler has made after performing the needed tuning to fully optimize the engine output.

The two graphs below are with my particular engine tuned and optimized for each configuration. Each configuration is the same with the only mechanical difference being the rear muffler. Environmental conditions where as similar as possible between the runs. Prior to optimizing my engine with the OE muffler (using the street tune) my engine made about 388WHP (on the finest 91 octane fuel California has to offer), so the Dundon team was able to squeeze out a bit more from the engine with the help of higher quality (read not from California) 92 octane fuel and a few additional tuning changes. Adding the the new muffler and tuning the engine further added an additional 14WHP .

Previously Dundon has measured a stock PDK equip'd GT4 which resulted in about 365WHP, and while that was on a different car, and different day, that does give a reasonable datapoint and is consistent with about a 10% drivetrain loss. Using that same calculus then it would be a reasonable estimate to say my car is making about 50WHP above its stock configuration. This lines up well with the likely ~30WHP gains from the header/OAPs + the additional gains from the muffler and tune. Of course these are rabbit holes best not entered into, but the obvious fact is the car is making significantly more power than it was from the factory, and the muffler and tune have made a big difference (even if surprisingly so).

According to Dundon the complete system will most certainly require a tune to work well as the reduced back pressure from the muffler opens up the engine so much that the OE tuning will struggle to keep up. Of course, they have a good tuning profile now that works with this setup.

The muffler will clearly only work with those already using Dundon headers, but does require new OAPs for which Dundon says there will be an exchange program. I'll leave it for Dundon to go into details on that.

More pictures and videos to follow

Avera

Good stuff!

Regarding gains, I still think the butt-dyno is most important when it comes to gains had from the headers/OAPs, or otherwisel. I absolutely appreciated the difference, which Dundon originally advertised - and you concur - to be about 30WHP from their headers/OAPs.

You suggest another 20WHP comes from muffler + tune. Not my intent to poo-poo your outcome, but you have ventured a LOOOONG climb for a SHORT slide with respect to those extra 20WHP . . . which I certainly hope ALL came from the tune given all that went into the tuning process. I am not going to digress at the moment, but I seriously doubt anyone would find 20WHP to be worth all the time and money invested if WHP gains were the sole objective.

Now, most importantly, the REAL reason you got the muffler . . . the ACOUSTICS. You know all the questions me and other are going to have . . .

1. Any drone?
2. How is the tone?
3. Howe are the decibels?
4. Etc.

As far as needing to swap out the OAPs, well, that is just another bummer. According to my understanding of your write-up . . . an owner would need to get new OAPs and a tune to make the vehicle perform optimally. I am going to venture a guess Dundon is not going to swap out the OAPs for free? Overall, we are looking at a HUGE investment in time and resources ($$$$$) for whatever the muffler accomplishes regarding questions posed above. If I still had my GT4 I would have to say - even if your GT4 sounded like a GT3RS - that is a not a 'climb' I would be willing to make or even consider. . . I would just get a GT4/Spyder RS, which you are going to end up doing anyway 🤣🤣🤣

Thank you for sharing . . . regardless of what I wrote above, I still look forward to hearing the results.

Avera

BabyNSX

Yes the gains do require an "all-in" approach but on a NA engine the diminishing returns was always going to require turning over every stone. It may not be a pill everyone is willing to swallow but look at the total area under the curve! Check out that significant mid-range bump! These gains would be just as impactful as adding the header and pipes without a tune or new back box. I think trying to extract what is having the single biggest impact would be challenging and not entirely useful.. engines are tuned air pumps and every component should be optimized to work together, I think what Dundon has done here is likely approaching the limit to what can be done with the long-block and intake system Porsche provided us with. I overlapped Dundons results with my engine with the GT4RS and it is making identical power to the RS all the way up to 7000RPM after which the 4RS and its better intake manifold and such allow it to pull away slightly. I can't wait for my butt dyno to confirm

The time and resources to achieve what has been achieved with my car has already been done, all new customers can benefit from that

Dundon mentioned an exchange program for the new OAPs for existing customers, I will let them speak to what that means. I simply don't know.

I suspect we will get some proper sound clips from Dundon soon to help answer the other big question but Jamie's initial feedback was extremely positive during his first test drive (ok, his opinion may be a bit biased, but from what I can hear with my own ears I suspect he and I will share the same opinion) There are some driving clips that he shared during the Dundon podcast last Friday (both at the beginning and end) The team also go into a lot of detail over the work they put into getting this dialed in:

https://www.youtube.com/live/Y-ZEdwu...9dZfHlBBZV8849