I honestly don't know. I mean I just keep hearing HKS powerloss. Even in the most recent thread about Invidia Exhaust: https://www.s2ki.com/forums/index.php?showtopic=564354

Scroll down and you'll see tylorweaver saying 4 of his friends lost power with HKS over stock and there's dyno too.

 

I wish he had the dyno print outs/

Have you considered the the fuji exhaust?

 

I think the HKS exhaust sounds ricey

My old T1R70 got compliments from even the V8 crowd.

 

Your going to blow a hole in your piston or burn up a exaust valve, it will be a race to see which one happens first at that AFR. Your either crazy or misinformed on tuning your car. Get help fast! 13.3 is max safe that any respectable dyno tuner will adjust for you. I play around with 13.5-7 pre vtec, but richer on top. 13 - 13.5 N/A is where you need to be dude. At 14.5 not only will you damage your engine, but you likley are losing performance d to not only the added heat your engine is producing but likely starving for fuel. Your running wide open near stoich mix for idle and partial throttle!

Yeah its believable. Dyno Jet reads lower so your actual power is closer to the upper 220's And Dyno jet is the standard we all go by when comparing numbers.

 

In an N/A application the 60mm and 63mm makes power throughout the entire rpm range. The 70mm, though makes a little more, only makes it in the upper rpm range. About 7500rpm and above. The more supporting mods you have to bring your engine power and efficiancy up, the more benificial the 70mm will become. FI yes. In N/A however, you can bring up your other supporting mods to produce the magical 230whp with a 60mm, but have a fatter trq curve as well say over a 230whp 70mm with less suporting mods. Its all bout the exhaust pulse or force your engine can produce to fill the exhaust mm area without creating turbulence. To much area to fill up a 70mm at lower/mid rpm so it is only useful in a drag race application where a more peaky characteristic isn't a hinderence since WOT at all times. 63mm FTW if you street and track.

 

Hate to go head-to-head with you once again, but what are you basing this on?

70mm exhausts make more power across the entire rpm range, equating to more usable power everywhere.

Direct comparison of T1R 70mm to T1R 63mm below. Note that both blue lines are above both red lines across the entire rpm range:


This is amplified for FI applications and/or with mods.

Feel free to show an actual dyno of a direct 70mm to 63mm comparison where the 63mm makes more hp or tq down low as you suggest.

Myth busted.

 

From the same thread you got the above dyno.

T1R 70R & 63 Sparrow (63 cat-back dual / 70R header back dual)
- made out of SUS304 aircraft stainless
- 63S designed for NA to improve acceleration and mid-range power
- 70R designed for NA tuned or FI engine setup
- 63S weighs 28 lbs / 70R weighs 33 lbs
- 70R comes with O2 Fix and detachable test pipe so youu can bolt your stock catalytic convertor back on anytime
- Dynoproven +5whp for 63S / +13whp for 70R


I think the main point here is that both of these exhaust's are proven to increase hp compared to some other exhausts.

 

[QUOTE=TB,Feb 6 2008, 05:43 AM] Hate to go head-to-head with you once again, but what are you basing this on?

 

^Hm.... that seems to clear the myth?

 

I'm not trying to argue here, but your post makes my head hurt...

Show me where it says they are not stock. And regardless, it is the same car, back to back, so the mods (if they exist) are no longer a variable.

And yes, the difference between the two is more noticeable up top. As it should be. The point remains that the 70 is still making more power down low (and everywhere).

Already did that...see above.

I can agrue it because not only are you wrong, what you're saying makes no sense:
A more noticeable improvement? The more power an exhaust makes, the more noticeable the improvement will be. The 70 makes more power at all rpms! It doesnt get any simpler than that.

What facts? You have stated your opinion, unsubstantiated. I am a degreed mechanical engineer and know all about how exhausts work, thank you.

The 70 is better for power. At all rpms. Period. The dyno above proves just that.

Of course there is more to it than just saying "The 70 makes more power" because usually people who say this are only looking at peak power. That's why I qualify every one of these statements I make with "...at every rpm." Because it makes more power at every rpm, the total area under the power curve is absolutely, positively, unarguably greater than that of a 60/63. Therefore, the 70 truly is better for power.

Again, I welcome any same car/day/mod dynos proving me wrong.