markiegt3

Hi all,

Here is an extract from another thread, 991.2 GT3, pdk that has Dundon Street Header and their intake system for comparison. JC, your gearchange must be on point!!-

"Products- Dundon catted Street headers, 93mm Throttle body, Plenum IMPORTANT NOTE: I am running factory center muffler, so i am loosing a little power over the Dundon Loud center.
Install- Was smooth, it does require some patience to ensure the plenum does not have any leaks. I would highly recommend using someone who has experience with Porsche vs a general speed shop.

Initial reaction: I felt that the car needed to learn a little bit. Once it did WOW was it a different animal. It really changed the tone of the car, and you can certainly feel the difference at the top of the rev range. Obviously a butt dyno doesn't do anyone good so i wanted to get some real data. We had a PCA club weekend right after install and i was with 3 friends 2 of which had bone stock GT3's so it was a great comparison on track. I also did some pre and post runs with a draggy and i wanted to share that data in the event it helps someone.


Stock GT3 60-130 runs PDK
1200Ft of elevation
65 degree ambient temps
Valid slope per Draggy

• 9.23 seconds
• 9.11 seconds
• 9.32 seconds
• 9.03 seconds

Dundon Package GT3 60-130 PDK
1200ft of elevation
67 ambient tempature
SAME ROAD as previous pulls done 2 days prior
Valid slope per Draggy

• 8.70 seconds
• 8.93 seconds
• 8.42 seconds
• 8.49 seconds

The biggest gains that I saw were in the 60-130 range and i consistently am faster with the set up. I will be the first to admit i did not think i would have much real performance gains in the data but the car just keeps getting stronger and stronger the more I run it.


Now onto lap times. Again , i didn't think i was going to notice anything so my expectations were pretty low. I know there is a lot of variables with this data but i found it interesting.

Brained International Raceway Long course
VMax on the long straight with my friends stock GT3 166mph
Vmax on the long straight with my dundon GT3 171mph
Same driver, Similar fuel loads. The data above was best case, however i will say the dundon car could consistently get 2 MPH over the stock car.

Lap times (i know hard to do apples to apples) But we tried!
1:45.88 stock GT3
1:44.53 Modified GT3
With this, we really looked at the Apex Pro data and overlaid the data to see if we were picking up MPH in corner exit/in. It was harder to tell but the Dundon car was always slightly ahead with the same driver and as close to the same fuel levels as possible. Laps were done back to back.


Over all, i would strongly recommend the power package. I was goinig to do just the headers at first, but im glad that i did the plenum and the new airbox. You can feel the car just breathes better, and i would imagine the thing really comes alive with a tune! The sound you get from the slower moving air inside that plenum is pretty cool. I think its safe to say everyone knows how good the exhaust/headers sound but it was a nice surprise to hear the sound of that airbox/plenum doing its thing!

I dont think anyone else can come close to the real world gains Dundon advertises (and i have tested). I have been impressed with the service and quality most importantly. The guys really know there stuff!

Please reach out if i can help. I have a lot of data i can share. I attempted to upload as much as i could here (NEWB) but happy to email it out to whoever needs it.

Thanks
Dan

997 C2S-Sold
991.1 TurboS- Sold
991.1 GT3- Sold
991.2 GT3
991.2 GT3RS (incoming, and it will 100% have this dundon set up as well)"

Dundon installed

Stock

Dundon Installed

markiegt3

Morning! (well in the UK)

I have another interesting find and shows how little I know in previous post, but below is a Dundon dyno graph with & with side mufflers.and the power & torque increase (991.2 gt3 manual). It probably means that the power & torque difference going from side muffler deletes to the Street header system is less pronouced than from the full stock system to Street header. Also help explain why JC's time is quick in 'stock' form as already experiencing a little bump in power & torque and the change to Street header didn't make as much difference.as expected. Thoughts?

Note, the Black Lifetime Muffler has a larger 3" size, so that may make a power/torque difference as opposed to just side deletes into regular 2.5" stock muffler...........

Dundon Valved Side Deletes and Black Lifetime Muffler
25lbft gain at the wheels and about 10whp

Lolo La Torche

yes, the positive impact of the side deletes was what I supposed a few messages ago. That's seems logical.

markiegt3

Agreed, albeit, some of that may be down to the side deletes being 3" and a better rear muffler design.........we'll not know unless someone does a comparison dyno with a standard muffler, but suspect you would still get a bump in torque but less top end increase

JCviggen

I don't think the side deletes do much, obviously a non zero amount but I would assume changing the muffler to a 3" path is a base case scenario to gain 10 HP with, as it's a manufacturer provided dyno it's always going to be at the high end of expectations. Give it 2 or 3 HP maybe from just removing the sides on the stock muffler.

I don't consider 9 seconds 60-130 to be unusually quick for a stock GT3, my manual GT4 with 470 HP did a 9.1 back in the day. Lots of youtubers in Europe get the same 100-200 km/h times (between 7.5 and 7.8s) for 991.2 and 992 stock which translates to 9 secs 60-130. 9.4 would be unusually slow.

Lolo La Torche

II could see several times that my car, simply equipped with an aftermarker muffler suppressor was faster than other identical full stock GT3. The difference was noticeable on circuit in "side by side" mode. But I did not ever find this data relevant because we all know that 2 different cars, 2 different engines, even identical series, have differences in performance...

I will repeat the same test with my new config (Dundon headers, side suppressors but GT3RS Muffler), hoping that the 10K€ investment did not downgrade the perfs .. Dyno butt is very difficult because it's cold these days, and I'm sure that sound and noise change the perception. Nothing but tested figures to prove something...

If possible, I'll try Dundon+Aftermarket muffler to compare (but it will take several months)

JCviggen

All right friends, the things that time sat bored in a plane is good for... I dug through ALL my dragy data as it is a significant amount especially when switching to metric km/h data. For the most representative runs I collected the acceleration data of some particular speed brackets to almost plot a dyno-like graph of how the car is performing at different RPM intervals. I didn't actually plot a line since the data points are a bit too far from each other, but I do believe I can at least somewhat explain the performance numbers better now.

Conclusion: the Dundon street headers make my car faster at high RPM but they are losing some power at the low end vs my stock header/side delete combo.

On the stock ECU, the Dundons are 1% slower from 5000 to 7000 RPM. From from 7000 to 7600 they are 0.4% faster. From 7600 to 8200 they are 1.4% faster.From 8200 to 8800 they are 2.8% faster.
On the tuned ECU, the Dundons are 1.7% slower from 5000 to 7000 RPM. From from 7000 to 7600 they are 2.7% faster. From 7600 to 8200 they are 3% faster.From 8200 to 8800 they are 5.2% faster.

I'll put the graph up below. I have no good explanation for why the tuned ECU seems to increase the amplitude of the changes, both losing more down low and gaining more up top vs the stock ECU. But I can definitely say that they don't do "nothing" They do all kinds of interesting things which does not show up in a 60-130 sweep. As it turns out the car spends a bit more time in the mid RPMs than the high RPMs so the losses there weigh a bit heavier than the ones at the top making for nearly identical times. Funnily enough I kind of felt it was the opposite, but I will trust the 10 Hz GPS data over my subjective impressions. You need to keep it above 7K to enjoy constant gains.

TDT

VE, my friend. As you say… depends where you want/need the performance and how you use the powerband and revs.

Lolo La Torche

So; it means that this modification is more track oriented than for road use! (at least on your car)

we also have to take into consideration that you don’t compare with a full stock configuration (side delete+modified throttle body+BMC filters)

JCviggen

Correct, although it depends on the track a bit and with my manual gearbox I sometimes can't avoid being below the "good" RPMs. With PDK it's easier for sure. At least with the ECU tuning there is still a lot more torque than before anyway even when the headers lose a little.

Lolo La Torche

To be honest, I did not expect that there would be losses...I hope at least I did not degrade the performance of my car...it is disappointing, knowing that the whole community was unanimous on the power and torque gain from the middle of the curve…

As I will never tune it…

JCviggen

Simon Motorsport in Germany tuned and dyno'd a 991.2RS and also found a power loss in the middle of the RPM band with the Dundons. But it makes up at high RPM so I would not be too worried, the benefits should show on track. It's not a totally different car but 10-15 HP more between 8000 and 9000 does make a difference.

74goldtarga

For lap time / hp / performance - if you were on a budget (of course that’s ridiculous but humor me) the tune offers more improvement over stock when compared to the exhaust over stock. I’m curious for speculation on how much better your custom tune is compared to an off-the-shelf tune. Many of us don’t have access to a custom tune without transporting the car. I’m left wanting a tune but no idea if it’s worth it for a 3.8L or if it’s worth it as an off-the-shelf option.

JC - based on the data do you think the exhaust will nonetheless aid you in lower lap times at the Nurburgring?

JCviggen

On a non-RS the tune will be a bigger jump than anything else you can do to it so yeah, for 2-3K it throws a lot of shade on the other mods. Obviously there's the sound element as well but you can achieve that with things that don't cost 8-9K.

It'll be hard to say what the exhaust does for lap times, just from where the power gains are it seems easier to get lap time from it at Spa than the Ring but it should be better than stock exhaust everywhere at least by a little. Unfortunately as you can't swap it on and off as easily as a tune there is a limit to how well it can be tested.

markiegt3

Good stuff JC, although I would say vey low down (3k to 5K) the car feels a fair bit stronger with the Dundon, so good for road driving. Do you agree?

Would be interesting comparing a pull in say 4th gear from 3k rev upwards standard vs Dundon, but doubt we will evet know.

Maybe one day I will get to a decent dyno cell, like Litchfield in the UK, who have done power runs for multiple .2 gt3 and compare.