UPDATE: Baseline graph added: 442awhp 482tq K16 baseline done with current 1.0bar flash and OEM exhaust. Next run next week with same tune and just added built exhaust.

Just dropped off my car to get a lightweight exhaust, custom built by a well merited racing shop. Engine has a 1.0 bar flash and forge diverter valves, that's it.

Question to knowledgeable people here: What is the appr range of potential performance gain that can be made (except the obvious good of reducing weight) from baseline as it is now and baseline after. All factors the same, I'm only asking what the catback build can do. No changes to car/fuel/dyno conditions otherwise. 5hp, 10hp, more?

I will get the sheets in the next few weeks of course, but half the fun is the speculation at the start.

Then the secondary question b/c I know that a bunch will bring this up anyway; are there better flowing cats that are a direct bolt on for 996TT - or would that have to be a fabrication/welding job?

Thx

 

i believe 100cel cats are the highest flowing and many companies make them it depends on what flange is used at the back side for the exhaust thats the shops take on it

V bands are awesome for serviceability.

im sure marksi has some more info on this or can provide you a couple cats

 

Thx! The exhaust will be built to be a direct OEM exhaust replacement.

 

fabspeed has cats that might fit in 100cel versions, mind you cali regulations want i think 400cel versions ?

 

Yea I don't need to go dirty on the exhaust so anything that is still smog ok and A LOT better than stock cats is interesting, if there is only a minor gain to be had I don't need to go through the trouble with cats at all. Even if I like driving fast I like green grass and trees and will be happy to run 400 cats.

 

When I installed my JIC Titanium with 200 cats I saw a real difference. My seat of the pants dyno would estimate 10 to 30HP (weight reduction and better flow)

 

Today Dynapak run gave: 442awhp 482tq on std K16 with OEM exhaust and a 1.0bar flash (yes, car has forge diverter valves).

Next run next week with OEM tune and OEM exhaust vs built exhaust. Then new full tune w built exhaust.

Merry Xmas to everyone reading.

 

Xmas delayed parts delivery and the car finally the went back in yesterday to the shop to finish the custom exhaust build. Included in the parts setup the builder had to include racecats, think he mentioned 200 cel back then, to make it as he wanted.

Now waiting to see what baseline performance gain that will come from just an exhaust. (mid week next week). Closer to 10 or closer to 30 hp to be expected?

Also, with my 442awhp tune, what will the new number be with a custom built race-exhaust? (I still have std K16)? Getting 10-30 extra hp will put 515 to 525 fwhp is this realistic on K16?

 

I would think you would get well over 30 hp. I think whoosh dynoed just drilling out the oem muffler to do a little muffler bypass and got 30hp. Add a good flowing exhaust and high flow cats. I would think 50hp or more! IMO

 

Let's make a small contest to see who really knows the 996TT the best.

The baseline 442 awhp on the car was done on Dynapak dyno (said to read slightly on the high side but this is a comparison from 1 dyno both runs) with:
OEM K16
OEM exhaust
OEM airbox and filter
1.0 bar flash
91 pump gas
forge dvs

Next run will be done Thursday on the same dyno with same gas, only upgrade added will be a custom built exhaust done by a very experienced racing company, including 200 cel cats instead of the complete OEM system. Headers will be the same OEM.

What do YOU think (know) the immediate gain be?

The poll is of open type where user names supposedly can be seen with the vote, so in other words, prestige here, who has the true knowledge?

The car will NOT be re-tuned between the runs, it will be the exact same 1.0 bar tune, just an open exhaust to compare on top of the initial 442 awhp run.

What will happen with the K16 OEM turbos? They are already close to peak as far as I understand in terms of K16 OEM capacity (442 awhp with appr 12% loss is just over fwhp 502hp). Will the added exhaust only cause lost back-pressure = no hp gain and actually loss of torque? Or loss or torque but higher peak hp? Just hotter charge air?

I sersiously doubt 50hp gain but maybe 12-15hp at higher rpm, however I'm a driver and chassis guy and don't know too much about tuning turbo engines. I'm leaving the poll to the pros to decide.

The right answer will come on Friday so the poll stops Thursday.

 

It will be more than 12-15. Just drilling holes in the stock exhaust did that... Add larger pipes and high flow cats, I would expect a lot more than that...

Here is my reference - whoosh did a dyno run similar to what you are attempting:

https://www.6speedonline.com/forums/1220886-post45.html

 

Thx for the link, it'll be fun to see what the tune will be good for to start. Good number in that thread with 459 awhp.

 

So 100 cell cats and no mufflers?

No Cats = I bet you lose so much torque down low that you will feel it

IMO It is possible to get 35-40HP in the lower range by virtue of faster spool (just shifting the line to the left). I think the question is how much peak or maybe even sustained HP you can expect. I think it's about 15?

BTW Dynojets read 5-8% high. Just read some info on that. My personal experience concurs 100%. I was kinda heartbroken when I first figured out that my maxed out K24s didn't really do 516WHP.. I added some quick spooling tials and set 20HP higher numbers on a Mustang a few years later. You don't need a dyno to know it's WAYYY faster now. Like 2nd gear just spins all teh way through, 3rd is close to spinning as well. That was never teh case with the K24s.

 

Nope, is doing a custom X exhaust with 200 cell cats from what I read. I guess we need to define where the HP gains will be. Max or gains anywhere in the RPM range... Up high, probably not much, down low, probably more. And for track use, that's where I would put my money...

 

Why a custom "racing" exhaust?

So many vendors have iterated fabrication/dyno performance/sound through multiple builds.... peak values are one thing, but the shape of your dyno curves would be what I'd want to control...

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