Performance with Secondary down pipes???

[RJ Orange]

Yesterday I done some runs against my friends GT-1 Stinger. His GT-1 has Intakes and secondary down pipes. Otherwise no other mods. My GTS has intakes only with no other mods. The GT-1 has 16k miles on it and the GTS has 550. both had driver only. We ran from dead stop, 20mph and 50 mph. I expected his car to pull away just because of the down pipes on his car and my car has stock exhaust. This was NOT the case. All the Runs were virtually even!!! We done this test to see how my car performed without done pipes before I install my down pipes. From everything I have seen on this forum and from venders. There is a performance gain with down pipes. Well These two cars did not show any gains in performance of down pipes over stock pipes. Im open to any ideas why these 2 cars run the same when one would think the car with down pipes would be faster.

 

[oddball]

The stock mufflers are a bigger restriction than the secondary cats. Install a cat-back exhaust *then* mess with the downpipes.
Plus we're talking something in the 10hp range which is really tough to see in that kind of ... uh... "test".

 

[Tonkabob]

Even with a catback the secondary DPs do virtually nothing. Do a search there is a good thread on this with a few dynos and some dragy and strip comparisons. I did the later. Perf gains on the track and dyno are not measurable.

 

[RJ Orange]

WOW! So it sounds like A muffler delete would have had more of a performance gain over down pipes. It would seem a car running more boost would have to gain with less restriction because of more exhaust flow. So it would seem gains would be seen with more boost with say a JB4 then?

 

[ZyroXZ2]

There a couple of things for me to mention here since I went from a 2018 GT to a 2019 GTS, partially from differences I've noticed between the two, and partially from experience modding these:

- If you both have stock exhaust, you're restricting yourselves from virtually any gains. Having said that, my 2019 GTS stock exhaust was MUCH louder than my 2018 GT. Whether this inadvertently results in a few hp is up in the air.
- You weren't really clear on the models. For example, if he has a GT1 AWD and you have a GTS RWD, he might be "losing" the 10HP more he has on you (if that) just because of the drivetrain.
- If you're both AWD, it also depends on what options his GT1 has that could very easily be adding weight. People constantly forget that weight is a major factor in performance, especially around here for some reason, lol... Two drivers, two same cars, one is 50 lbs heavier than the other guy and has some junk in the back, of course he'll be a little slower. So that could also easily wash away the small difference in hp.

The real result here will be you getting secondary DPs and repeating this "test". Of course, as we all know, different day, different weather, different humidity, etc. But yea, get your secondaries and make another run at it.

For the record, though, my GTS also has a lot more cabin noise compared to my 2018 GT. It's as if there's less sound deadening on the GTS than my old one. Even the same exhaust system I put on my 2018 is louder on my GTS. I still haven't figured out if that's a change in the packing of the mufflers or the GTS is somehow different. And I've checked ad nauseum and even moved to v-band clamps in an attempt to ensure there's not an exhaust leak.

 

[Tonkabob]

Here is the thread with the performance data and dynos for secondarys as it may be hard to find given the title.
3.3TT - KHARTUNERZ - NEW CATLESS SECONDARY DOWNPIPES Ark Performance

 

[xot1]

Vendors who say you have performance gains by doing secondary downpipes are not being truthful. They mostly increase the sound.
When pushing the car to its limits, removing them will help a bit, but not with few light mods and a stock exhaust.

 

[RJ Orange]

There a couple of things for me to mention here since I went from a 2018 GT to a 2019 GTS, partially from differences I've noticed between the two, and partially from experience modding these:

- If you both have stock exhaust, you're restricting yourselves from virtually any gains. Having said that, my 2019 GTS stock exhaust was MUCH louder than my 2018 GT. Whether this inadvertently results in a few hp is up in the air.
- You weren't really clear on the models. For example, if he has a GT1 AWD and you have a GTS RWD, he might be "losing" the 10HP more he has on you (if that) just because of the drivetrain.
- If you're both AWD, it also depends on what options his GT1 has that could very easily be adding weight. People constantly forget that weight is a major factor in performance, especially around here for some reason, lol... Two drivers, two same cars, one is 50 lbs heavier than the other guy and has some junk in the back, of course he'll be a little slower. So that could also easily wash away the small difference in hp.

The real result here will be you getting secondary DPs and repeating this "test". Of course, as we all know, different day, different weather, different humidity, etc. But yea, get your secondaries and make another run at it.

For the record, though, my GTS also has a lot more cabin noise compared to my 2018 GT. It's as if there's less sound deadening on the GTS than my old one. Even the same exhaust system I put on my 2018 is louder on my GTS. I still haven't figured out if that's a change in the packing of the mufflers or the GTS is somehow different. And I've checked ad nauseum and even moved to v-band clamps in an attempt to ensure there's not an exhaust leak.

The GT-1 was a 2018 rear wheel drive. 2019 GTS rear wheel drive. Drivers very close to same weight. In my opinion on a stock car with intakes I did not see adding a secondary down pipe is cost effective. Each run we made was within a fender or even. For me I plan on installing a muffler delete next.

 

[oddball]

WOW! So it sounds like A muffler delete would have had more of a performance gain over down pipes. It would seem a car running more boost would have to gain with less restriction because of more exhaust flow. So it would seem gains would be seen with more boost with say a JB4 then?

The primary cat is the restriction when it comes to generating boost, which is why there's all the discussions about overboost codes and limp mode when deleting the primary cat. The secondary cat has little impact because you're waaaaay down the pipe at that point.

 

[RJ Orange]

It would seem that the overboost is the real problem. Maybe new turbos or wastegate control. I am aware that turbo cars respond in a big way to free flowing exhaust. I had many turbo Buicks back in the day. They could be made into Monsters with minor bolt ons. The Design of this turbo system seems to more of a challenge. compared to all the controls on the stinger the GN/T/TYPE was a snap to get to respond. The fact that there is a problem when the exhaust is freed up is keeping this car from making the power it can. If 450WHP is there is a lot to be able to do with stock turbos. Anything higher I suspect would awake reliability Issues. I would welcome a day to day driver with 450WHP on stock turbos. Time will improve knowledge on these cars. Reliability and horsepower will come.

 

[ZyroXZ2]

It would seem that the overboost is the real problem. Maybe new turbos or wastegate control. I am aware that turbo cars respond in a big way to free flowing exhaust. I had many turbo Buicks back in the day. They could be made into Monsters with minor bolt ons. The Design of this turbo system seems to more of a challenge. compared to all the controls on the stinger the GN/T/TYPE was a snap to get to respond. The fact that there is a problem when the exhaust is freed up is keeping this car from making the power it can. If 450WHP is there is a lot to be able to do with stock turbos. Anything higher I suspect would awake reliability Issues. I would welcome a day to day driver with 450WHP on stock turbos. Time will improve knowledge on these cars. Reliability and horsepower will come.

There are tons of people making 450WHP driving daily. My old one dyno'd 442WHP on SAE correction (so closer to 447WHP on STD) on E30 without WMI.

 

[Jonathan Lasich]

The primary cat is the restriction when it comes to generating boost, which is why there's all the discussions about overboost codes and limp mode when deleting the primary cat. The secondary cat has little impact because you're waaaaay down the pipe at that point.

I don't know if people remember, but Took Motorsports released a video quite a while ago (over a year?) showing how restrictive the primary downpipes were. One of them (maybe the driver's side) had a diameter of 1.25 inches, plus the restriction of the OEM cats, no wonder there is overboost with aftermarket primary downpipes. Seems like that is where the major restriction resides.

 

[Tonkabob]

The primarys aren't that restrictive. These cars just overboost easily when you crank up boost catless or not. Less restriction easier of course but removing either cat adds little power.

 

[Daniel @ K8 Stinger Store]

There are minimal gains if anything with installing aftermarket secondary downpipes. However, they do change the sound and tone of the exhaust and for that alone, they could be the right mod for the right person. For example a lot of people run the Ark Performance Downipipe and the Borla Turbocharged cars do gain significant performance from changing or eliminating the cats. For the Stinger GT you would want to swap the primary and secondary cats in order to get maximum horsepower ability pre-catback. We sell the Ultimate Performance HFC Combo Kit here at the K8 Stinger Store. This combo kit is the only option to my knowledge that offers both primary and secondary HFC that throws no CEL and does not require a tune.

 

[RJ Orange]

Nice looking pipes for sure. But is there an overboost condition because of all the free flow now???

 

[Rynil2000]

Sound check for Borla cat back before and after ARK downpipes

I can't say that the downpipes made a noticeable HP gain, but the sound is so much better (deeper, throaty) with the secondaries gone. Even if it's only 10 HP, it sounds hella faster.

 

[Nightshifter]

Any time you alter the exhaust, you need a new tune! The exhaust is factory tuned to scavenge the cylinders optimally.... You'll be reducing back pressure thus altering the exhaust velocity for the factory setup. This is the main reason most people actually have no performance gain, or make it worse because the exhaust isn't being scavenged properly... If you open it up too much, the velocity of the gases will slow down unless you increase the density which means more air & fuel . RETUNE! Anyone who's an expert with cars will tell you this. I know from doing it all myself and learning over the years.... You might see a gain on some cars ... but sometimes you'll lose bottom end torque because the back pressure has been altered in some manner. Again... mileage varies

 

[Aarvix]

True for NA, not so much for a turbo motor.

 

[Nightshifter]

True for NA, not so much for a turbo motor.

Hello Aarvis! I agree that's usually the case but there's a few variables to consider here.... A turbocharged system does require larger-diameter exhaust piping, which is critical for both engine durability and the production of horsepower and torque. In general terms, a V-8 engine that runs a single turbo in the range of 6 to 15 pounds of boost requires a minimum 3-inch exhaust, while a twin-turbo setup exhaust pipe requires only a 2.5-inch exhaust. As you increase boost, the exhaust pipe diameter needs to increase proportionately. Running an exhaust pipe that is larger than necessary usually doesn’t hurt (depending on the car), but running a too-small exhaust or altering the existing exhaust improperly will be detrimental to both power and the engine’s maximum RPM (or shift the power curve). The best way to help maximize efficiency is to tailor the exhaust system for maximum exhaust gas scavenging. If the 2.0T isn't generating enough boost, then putting an aftermarket down pipe won't really amount to anything. If you chipped your vehicle for more HP (fuel remap, boost, timing blah blah blah) then yes, it would be very beneficial to open up the exhaust all the way to the rear (not just the down pipe because you would be creating a bottleneck thus effecting the physics of the flow)... not too mention the intake as well Dyno tuning your car after all the mods is best way to make sure you're getting the most power and to see which mods actually help or hinder the cars performance from my experience.

 

[Nightshifter]

WOW! So it sounds like A muffler delete would have had more of a performance gain over down pipes. It would seem a car running more boost would have to gain with less restriction because of more exhaust flow. So it would seem gains would be seen with more boost with say a JB4 then?

If you're going to put on an aftermarket down pipe, then you should also open up the rear because you'll just be creating a bottleneck. I had a 2009 EVO, and I remember when I put on the down pipe first after a Buschur Racing stage 1 chip (23 PSI), it actually hampered my performance a bit because I was creating a lot of turbulence in the exhaust system. A sudden rush of NOW unrestricted hot gas hits the stock exhaust is like blowing out more air from your lungs with a wider mouth opening kissing a short piece of PVC (the down pipe) into a straw (stock exhaust)! When I added the racing exhaust to allow that down pipe to do its job; it was night and day!