Originally Posted by belfo

Isn't this pretty thin, even for 321 stainless?

I'm used to seeing 16Ga as standard for street applications, and 18Ga is 20% thinner. How does durability of 321 stainless @ 18Ga compare to that of 308 stainless @ 16Ga? I note that you offer a lifetime structural warranty for the original purchaser, but the academic question remains.

Comparison of 308 vs 321 below.
http://www.burnsstainless.com/stainlesssteel.aspx (see bottom for material properties)

Originally Posted by okie981

Do you also have the weight of the uninstalled headers?

Originally Posted by Jamie@dundonmotorsports

Directly from the link:

"Both 321 and 347 are top choices for exhaust headers, especially turbocharger systems and rotary engines. Since 321 is much more available than 347, that leaves 321 as the first choice, with no sacrifice in needed qualities."

18Ga has shown over many 100's of hours on the headers we've built to be more than sufficient for street car duty. If you wanted something lighter 20Ga has worked well for race cars in 321. Wouldn't use it for a street car.

And thanks to fellow rennlister Alan for this, he's retired from the steel industry...

"T321's service temperature from 800-1500F plus the fact that you all but eliminate IGA ( Inter Granular Attack) in the HAZ (Heat Affected Zone) are 2 of the prime reasons I think it is a better choice. The titanium in the 321 ties up the carbon and prevents chrome carbides from forming in the grain boundaries. Without the chrome the grain boundaries can be attacked by exhaust gas condensates. This results in cracks in the HAZ not the weld pool. People blame the failure on poor welding but it is actually poor selection of materials for the job. The mechanical properties for T304 and T321 are really pretty close. T304L, low carbon, shows less formability."

As far as Type 308 it's used as the filler metal when welding 304SS

Originally Posted by belfo

Thank you. I had meant to write "304" rather than "308."

Originally Posted by No Heel No Toe

I need these shipped to Australia in about 3 months 😛

Originally Posted by CarAholic

I need to start top looking at this thread getting depressed, lol.

Originally Posted by Knolow

Got to luv the open communication along with the logical and backed explanations.

Originally Posted by Jamie@dundonmotorsports

Thanks, we're trying to answer them all and help everyone understand why we're doing things the way we do!

Originally Posted by Mech33

Hi Jamie, would you be willing to help explain why you think the Dundon GT4 headers would make more power than the Cargraphics Race headers (ignoring material quality differences)? To the layman, the designs look very similar, so I'd be interested in understanding the nuances. Thanks!

Originally Posted by Fstclyz

Funny - Just prior to reading this thread this morning, I was thinking of doing just headers and a tune, then the IPD/TB and another tune if needed. From all my cars and mods over the years, I've sometimes found similar results to what we're reading, and many times the stock exhaust isn't that restrictive, just heavy. I WANT more power but don't really need a louder car. IMO the stock exhaust "open" sounds great.

I like that Dundon isn't trying to upcharge us for other parts which really don't give material benefits. Like the air filter option for $215....psssfff

On another note, I actually prefer the sound of no cats and a muffler system versus cats and a limited muffler system. I guess the only issue for me right now is the CEL errors as I don't want to have those or any other codes flashing at me.

Originally Posted by Jamie@dundonmotorsports

Hi All, We're very happy and humbled by the response we've received from the forum members on our development work for the GT4 so far. We've finished up the development and production prototypes. Just tested them on the car this morning. Here's the results on a stock car, bolt on, no tune. Dundon GT4 Race Headers, No Tune Dundon Motorsports GT4 Race, Stock Tune vs. Stock Exhaust, Stock Tune Gains Over Stock. 3600 RPM: +42 wtq 5000 RPM: +36 wtq, +34whp 5800 RPM: +15 wtq, +16whp 6500 RPM: +28whp 7000 RPM: +30whp 7500 RPM: +41whp Our dyno read the stock car at 330.8 whp at 7400, Porsche rates the car at 385bhp at 7400, this is 14.1% loss with our Dynapack 4000 hub dyno running the car in Rolling Road mode using the factory PIWIS tools. Using this Conversion the headers alone get us to 426BHP For those that want a bit more we offer a Cobb Accessport with a Dundon Motorsports Pro Tune tailored to the Race Headers. Dundon GT4 Race Headers with Dundon Pro Tune Dundon GT4 Race Headers, Dundon Pro Tune. 377.1 WHP Gains Over Stock including Dundon Pro Tune: 3600 RPM: +50 wtq +32whp 5000 RPM: +55 wtq, +52whp 5800 RPM: +24 wtq, +26whp 6500 RPM: +30 wtq, +36whp 7500 RPM: +30 wtq, +43whp 377.1whp on our dyno works out to 438.8 BHP Materials: The Headers are 18 Ga 321SS. We keep stressing this as the quality of the materials matters. It dictates fitment, it dictates the quality of the welds and the ability of the system to withstand the abuse a car like the GT4 can dish out. This makes our systems cost more than our competitors as 321 is typically 2x the cost of 304SS (what most others stainless systems are made with), but it's important to us to use great materials. We believe in it so much that we offer a lifetime structural warranty to the original owner of our systems. Design: The design of our headers is unlike any other on the market, and was specifically created for the GT4, not just to fit a 981 Cayman, but specifically for the 3.8L engine in the GT4. When we make headers for the rest of the Cayman family they will specifically designed for them as well, each engine requires a different design to extract the most from it! Fitment with factory PSE: The Dundon Race headers are designed as a direct replacement to the factory system and will bolt right up to the factory sport exhaust, so you retain your valves and ability to quiet the car down for "dinner date duty". Sound: Very much a dual personality system. With your foot out of the throttle very livable, talk on the phone in the car etc. PSE button on and foot in it, and get this! Video Link: https://www.youtube.com/watch?v=OJG-wdxjL0g Video Link: https://www.youtube.com/watch?v=XpC3713d8wI CEL: To keep the CEL off while using this racing and offroad use exhaust, we have improved our post cat O2 bung defouler so that it is off 99% of the time. We've been testing with 991 GT3RS with very finicky programming and it's been working like a charm. Plenum/TB: We ran a popular plenum and 82mm TB on our headers and our tune and found no measurable improvements even at high rpm. This is good news to some as it means the power improvements are easily achieved with just headers and a tune or even headers alone. We do believe there is more power available through work on the intake/plenum and we will be pursuing this as a Stage 3 package. Street System: Catted system development is already underway and we will putting together a prototype for testing in the next 2-3 weeks. We need to finish the 991 GT3 catted system first and then back to the GT4 catted. Dundon Race Header Pricing and ETA: We're looking at about 5-6 weeks for delivery for the systems. We're starting with a batch of 20 sets. Retail Pricing for them is $4250.00 Rennlist Pricing is $3950.00 Group Buy pricing is $3750.00 The Group Buy is limited to the first 20 systems. We will require a $1000.00 deposit to secure your group buy allocation. Ground shipping in the US is free Tune Pricing: The Cobb Accessport is a very convenient and stable method for tuning a modern vehicle. It has the ability to store tuned and stock files, log engine parameters and read/clear engine fault codes. The price of the Cobb Accessport is for the device and some generic off the shelf tunes. The OTS tunes add some power, but not near as much as our custom developed Pro Tune. Cobb Acessport: $1295 Dundon Pro Tune for Race Headers: $495 Package Pricing: We'll offer a further discount for those that order the headers, Cobb AP and Dundon Pro Tune at the same time. Total Group Buy Package Price for Race Headers, Cobb AP and Dundon Pro Tune: $5350.00, savings of $690.00 Please email Jamie@dundonmotorsports dot com and we will send a paypal invoice for the deposit As always, any and all questions are welcome!