Why is stock 2" exhaust not a restriction

[Myx]

These cars are making a lot of horsepower through our stock exhausts. Why?

It goes against everything I have been reading, especially on a turbocharged car, up to this point. I can see now that it is accepted here since PRL's dyno test but why isn't it a restriction?

2" ?wtf?

I mean, it is what it is but I don't get it. **Scratching head** What's the explanation behind this? I'm cracking on 13's myself and the car is quiet as a mouse. With a 2" exhaust.

I'm been sitting here and pretending this isn't happening for long enough. Hehe!



Edite (Updated).

AFE exhaust: 7whp (This was installed first with stock downpipe and frontpipe). HERE
AFE downpipe: 5whp (On lowend. Topend, they were experiencing hp loss due to hot intake temps/ignition timing being pulled. HERE
AFE frontpipe (Or Rear Downpipe they called it): 10whp. HERE
Blog Details on full exhaust setup: HERE

Apexi N1-X Exhaust Dyno


Anthony Taikyu! Wanted to capture it here just in case it is lost on Facebook.
Facebook Post --- HERE
I am attaching the dyno result below.
Here's what Athony Taikyu had to say about it in that Facebook post --->J

Solid line is the full boost map - 243.5 hp 248 ft/lb
Dotted line is the Econ button map 227 hp 212.2 ft/lb
Dashed line is standard map with only the Spoon exhaust fitted (circa) 195 hp 205 ft/lb

Book power figure is 182 hp

Super pleased. Mapped gains of 50hp and 50ft/lb.

There were bigger numbers but Paul pulled it back to give a better power and torque curve.

Drives brilliant. Power matches the chassis now. Will lose traction in third gear in the dry now.

Turbo runs out of puff at higher rpms. Look forward to the next stage!

Sponsored

 

[hawk02]

That's why Borla, MF and 27WON are 2.25/2.5, 3 is overkill and can actually decrease power or move the power band to a higher RPM. Bigger is not always better, turbo or not it's a damn 1.5l, soda comes in bigger displacement bottles....LOL

 

[17siturb0]

Small engine and small turbo. Last time I’m saying it. Build the engine, bigger turbo, then you’ll make gains off a 3 inch exhaust etc..

 

[baldheadracing]

... It goes against everything I have been reading, especially on a turbocharged car, up to this point. I can see now that it is accepted here since PRL's dyno test but why isn't it a restriction? ...

IIRC, PRL's test that showed no gains was with their downpipe and front pipe already installed (and gaining power). The exhaust system gains are to be had, it is just a question of where. With a turbocharger, you (more-or-less) lose the "tuning" (as in musical instrument) aspect an exhaust system, so go big early to reduce restriction to the turbo (and low-restriction cat depending on local law enforcement, etc.), and, if desired, reduce diameter afterwards for sound suppression/reduced weight, etc. (As an aside, there is some confusion as to what a "cat-back" exhaust system is - whether the front pipe is part of the system or not. Some vendors, e.g., Thermal, have cat-back systems that include the front pipe; others do not.)

You also have to look at the engine's tuning. The 1.5's are tuned for mid-range, a range where the 2" flow is more than enough. The 2.0l's are a bit more aggressive in tuning (and have larger diameter pipe IIRC) but so far the published gains (with stock downpipe, stock tune, etc.) are with going to 3" on the frontpipe. Afterwards is seemingly just more noise.

YMMV.

 

[Myx]

So much for my question some 3 years ago. Posting the info below in the original post as well, in case someone runs into this post while searching.

AFE exhaust: 7whp (This was installed first with stock downpipe and frontpipe). HERE
AFE downpipe: 5whp (On lowend. Topend, they were experiencing hp loss due to hot intake temps/ignition timing being pulled. HERE
AFE frontpipe (Or Rear Downpipe they called it): 10whp. HERE
Blog Details on full exhaust setup: HERE

Sponsored