ranger22

They told me the same thing.....

JG 996T

can someone post the vid?

Wonderdan

I have had every combo of v1 and v2, the title says “race” power package. That kit most certainly sets off your CEL since it’s cat delete.

If your taking about the street headers refresh both of your post cat O2 (I’d do all 4 if it was me), so your eliminating cat efficiency bank 1,2 (P0420) as a culprit, then when you diag and tune you know it’s not a sensor setting the CEL , it’s the tune.

I think I talked about this a few years ago in a thread. Your dealing with 200 cel cats now so everything’s tolerance goes down… even more so if your changing the manifold. But I’ve always been able to get to l a spot with the tune where I’m not running to lean for the CEL. Unlike some rumors Dundon is not tuning out the CEL, they are tuning to be compliant and have the best possible back pressure for your setup.

Have you guys done a custom tune, if so how many iterations w/Charles?

Im on the best “compromise” sound setup now with a new 991.2 Ti muffler and tips and 2.0 headers, with baffles closed its nearly stock. But I can light up an underpass sometime this week for the thread, it’s no straight pipes but sounds good.

prl

Just run two 5” 400 cel gesi g-sport cats instead, you won’t lose any horsepower and you won’t have a cell. Gesi has some of the best cats and continues to work on them. From personal experience testing cats, generations, manufactures, gesi g sport with the spiral spin for di engines performed 1.2% less hp than a straight pipe on a 500whp car on a dynojet with every readiness monitor checked. Just saying cut the cats off throw some higher end gesi 400 cell’s on it you won’t lose anything to think about. Now gesi does have lower grade cats also, but the top g sports, just had them on a 4rs with no cel all monitors checked.

Jamie@dundonmotorsports

it’s unfortunate you had this trouble. The system for 99% of folks performs flawlessly. Typically issues wirh CEL are air leak related.

for the few that aren’t that we can fix it with proper fueling with a cobb AP.

fwiw. We’re using American made catalysts in all of our products.

Jamie@dundonmotorsports

in general a healthy mezger will not set CEL with our headers….

ranger22

Keep telling the lie Jamie, some will believe it.
If you're one of the so-called 1% that get a CEL, don't dare tell anyone because "you obviously have an unhealthy Metzger. Shame! Or you could just buy more stuff from us, it will work, promise!"

Wonderdan

I’ve had 2 different generations of Dundon headers, both threw cat efficiency codes, both stopped throwing codes after iterating on the custom AP tune, both ready all sensors after single good drive cycle and both passed emissions…

So only going off my experience the only 1/2 truth is if you are one of the unlucky ones that tosses a code like me you NEED to buy the Cobb AP to get it back to an ideal state.

Not so turn key for everyone but for gear heads I enjoyed the process and my 28hp is WAY faster lol

vma1788

I'll play both sides here. I have GMG headers and 200 Cell cats. I've had my car (with them) for 4k miles and I have gotten 2 check engine lights for post cat o2. Both times were from low rpm operation for a longer duration- a photo shoot with low speeds and the other while in lots of traffic and low rpm city driving. Maybe what triggers the CEL is situational?

Wonderdan

Yep when I set my CEL it almost always when it’s lugging… but the tune I have now doesn’t trigger no matter how crappy I drive.

Jamie@dundonmotorsports

If you're interested in how the physics works for the resonance intake. Short version: Porsche uses 3rd order resonance on the intake, we use 2nd order resonance on our intake manifold this gives the charging wave 11% or so more strength so more O2 gets shoved in the intake. the shape and length of the runners, the volume of the plenum effect the wave strength, constructive and destructive interference that all plays into the benefit.

When you include our headers with a significant suction wave (scavenging) on top of the manifold, you get a 1+1+3 situation due to the differential pressure created between the intake and the exhaust during valve overlap allowing us to "suck" out the spent gasses allowing you to use all of your displacement, and "supercharge" the engine with the charging intake pressure wave.

https://z-p42.www.instagram.com/p/CNdxw-iIfXx/

https://www.dundonmotorsports.com/bl...bsessed-garage



Matt, you have our full backing and support. If you have trouble we will support you, and make it as right. V2 is the right system and we don't lie...


Mergers need to have a good "Italian tune up" and you've nailed it. Get a tune if you're car is a little cranky at low RPM's or you have extended or unique situations (not everyone is at 5000 ft of elevation and NA engines act different at elevation...)

Now to the rest of the questions

• @Ranger22, We do our best to trouble shoot the issues folks have. When they become combative and persistent in calling us and me personally a "liar" its where my desire to help declines significantly. What was your order number and where did the headers come from?

• V2 is better for V1 as far as setting CEL specifically on 997.2 GT3 (the most sensitive). We shortened the secondary length so the delay from combustion to post cat 02 reporting a voltage is more like what the car would expect, this shortening of the secondary length also helped the intake manifold with unwanted reversion...

• The comments about getting new O2's on the car is a sound one as the sensors do age. Further getting a tune on the car to get the correct lambda (especially at low RPM cruising) is the best solution, not always required, but some cars are more sensitive than others. 997's are getting up there in age, it's not a cheap car to own, so don't think you can "cheat" when upgrading it.

• Resonance Intake skepticism: It's funny how many folks are skeptical of the dyno's, (not just our dynos). I get it, seems crazy to think we can extract that much power from the engine. We worked on this for over 22 months to get it right. But the physics are simple once explained and there are more than 1 satisfied customer that saw the results with their own eyes.
  • This thread was started by a satisfied customer in Canada that had his car ran on the installers dyno...
  • I shy away from taking customer cars out, or asking customers to run 60-130 times as bad things happen at speed on public roads... This is why dyno's were made...
  • Are 60-130 the only thing people will believe?

• 996 GT3 will benefit the same as the 997.1 GT3's (is very close to the same engine) and the manifold doesn't have flaps in it (so there's nothing to fall in the engine like the 4.0RS manifold). I can get you in touch with owners of other 996 GT3's with the kit. We've done 2 of them so far with great results...

• The physics works for all mergers 3.6L - 4.2L (cups are a challenge as they're throttle cable and not straightforward to tune). Leh Keen's 4.2L Frog has our kit on it, Daryl's 997.1 above has it, multiple 997.2 GT3RS' a few 997.2 GT3's and 2 996 GT3's

• Catalysts, we use the same American made catalysts on the 997 system as we do on the 992 GT3 systems, and they're way way more cranky about conversion and deviations from spec on post cat lambda. Where we've seen issues with CEL are typically air leaks as air confuses the 02 sensor. We added gaskets to the vbands in late 2019 for the 991.2 GT3 as it was cranky and the smallest minor air leak from a hurried install would pop a light. After the seals added to the vbands no more CEL regardless of the monkey that installed them. We rolled that out to all systems there after. Our catalysts aren't rolled up zig-zag bent sheets like you're used to seeing. This is where the "cell count" methodology comes from as the cat essentially as "straws" running through it. Our cats are stacks or sheet with a chevron pattern on them to promote quick and even mixing even at low mass flow. They do great holding up to track work as there's very little resistance to flow and they create great mixing and CO conversion. They also don't hold on to heat as when the car dumps fuel when it's seeing elevated temps and load it cools the cat off really really quickly...

• Anyone who has purchased directly from us has a lifetime warranty (to the original purchaser). So if your cats ever stop working (exceedingly rare, but they are a consumable...) reach out. Will we just roll over and send you thousands of dollars of parts on your say so? No, we will want you to do a few things before we get there. If you call Apple and say my phone isn't working, they don't send you a phone without verifying things either.

ranger22

I'm not getting any joy out of calling out the lie, but I do want the community to be informed. Dundon claims above that no CEL will occur for 99% of users. Yet in this thread alone, around 50% have reported a CEL. Now we're being told that these cars "are getting up there in age." So perhaps the fix is to need gaskets, maybe new O2 sensors, maybe you can tune it out. If that doesn't work then your motor is unhealthy and you can't go cheap on upgrades. It sure sounds like Dundon is well aware of the issues associated with these upgrades, yet they will continue to repeat 99% of cars will not have a CEL. The community needs to know that this is not true and there is a high likelihood that something else will need to be done to prevent the CEL. If headed down the troubleshooting path, this will be done at the expense of the owner's time and money and Dundon will try to do the minimum fix each time starting with tossing out some gaskets and have the owner install them with the headers at the owner's expense. If Dundon knows this is a problem, why don't they just ship them with the headers in the first place? The install cost/time far exceeds the cost of new gaskets.

bweSteve

from my keyboard point of view, seems that pretty much EVERY customer has a different situation, especially elevation. I'm no mechanical engineer but it seems to me that investigating the reasons why CEL, and the approach of possibly applying new O2's (or moving their location), identifying & fixing any air leaks, customizing a tune, etc, is all part of the process of getting your car running the way you want it, + for the customers own specific setup (type of exhaust, headers, cats, etc etc). ... and yes, on the customers dime, since the customer was the one who headed down the path of modifications in the first place. None of that seems out of place to me.

subscribed.

ScottArizona

I don't have a dog in this fight, and have never bought a single thing from Dundon (new or used...I'm too cheap). But I can say this. If most people don't have a CEL problem with a given product, there probably ain't a "problem" with the product, even if technically the product could be characterized as the "but for" cause of the CEL or the "straw that broke the camel's back," as opposed to the "proximate cause" (sorry, I'm getting all lawyer nerd-like now). This is what makes the tuning industry so complex. If, after installing a given product that others have installed without issue, you get a CEL, I don't think you can say "see, the product is crappy or poorly engineered" or someone is a "liar." In fact, I know you can't say that. There could literally be 100 reasons the addition of said product, combined with some other underlying condition not present with other owners' engines (i.e., aging 02 sensor, bad Maf, bad gas, vacuum leak, worn out cats, etc...), could result in a CEL.

The semi-custom tuner for my old 996tt with some miles on it once told me he would not tune my car unless I first replaced the MAF and both pre-cat o2 sensors. I told him I didn't have any codes, and he (rightly) told me those items are effectively wear items which can be well on their way to useless before a code is triggered, and it was simply not worth his time to risk it and then trouble shoot "issues" that were not caused by the tune but perhaps "manifested" as a result of its addition. There is a difference.

650kid

After my very first transaction with Dundon years ago it was about 9pm at night and Jamie was on the phone helping me trouble shoot some install stuff. I could never say enough good things about the customer service I’ve received over the years.