Calling all v6ers who have gone from 2.5" to 3" exhaust...

[HBHRacing]

Look again. your not sticking to your CI table in the chart. That table only goes up to 200 HP at 2.5". Just because you are no longer in the same HP table that doesn;t mean that you get to jump to the higher CI table. Since the chart doesn't provide the info for a 250HP 3.8L motor that is exactly why I had to "guess". But no, i'm not guessing like the rest of you. I am taking the princapals that I know and understand and using that to make the best possible estimate that I can. Going by the motor size I would still belive that you would need a MIN of 230-240 HP before you need to move up to a take off size of 2.75. Remember, it's still a 3.8, your simply not moving the amount of air as a larger displacment motor. going by the same thought. That 2.75" should take you a long ways up heading twords 275+HP before you need to think about 3 inch. The LT1's have 285 and still tend to suffer slightly with a 3 inch cat back untill the RPM's come up a little. then it's right in our range. remember, by looking at teh chart a 350 CI motor can go all the way to 350 HP with a 3 inch.

[Turbo V6 Camaro]

Originally posted by HBHRacing:
Look again. your not sticking to your CI table in the chart. That table only goes up to 200 HP at 2.5". Just because you are no longer in the same HP table that doesn;t mean that you get to jump to the higher CI table. Since the chart doesn't provide the info for a 250HP 3.8L motor that is exactly why I had to "guess". But no, i'm not guessing like the rest of you. I am taking the princapals that I know and understand and using that to make the best possible estimate that I can. Going by the motor size I would still belive that you would need a MIN of 230-240 HP before you need to move up to a take off size of 2.75. Remember, it's still a 3.8, your simply not moving the amount of air as a larger displacment motor. going by the same thought. That 2.75" should take you a long ways up heading twords 275+HP before you need to think about 3 inch. The LT1's have 285 and still tend to suffer slightly with a 3 inch cat back untill the RPM's come up a little. then it's right in our range. remember, by looking at teh chart a 350 CI motor can go all the way to 350 HP with a 3 inch.

so what would i need for 500-600 HP at the wheels? (my goal turbo is on and boost to 12 psi now [img]smile.gif[/img] )

[HBHRacing]

again. Boosted applications are a totaly different beast. Because of the extra pressure in the motor it will easily overcome the force aplied against it in the exhaust. So go big enough that you don't have a restriction up high and you will be fine.

[Turbo V6 Camaro]

Originally posted by HBHRacing:
again. Boosted applications are a totaly different beast. Because of the extra pressure in the motor it will easily overcome the force aplied against it in the exhaust. So go big enough that you don't have a restriction up high and you will be fine.

well right now its open down pipe lol

[HBHRacing]

The best thing for you to do (when boosted) is to get your exhaust flow out as fast and possible. No cat, and preferably a cutout before the muffler. What you need to do then is to adjust your cutout location to best suit your RPM window. You tune the cutout distence based on where you want your power. The "general" starting point for 4000-6000 RPM band is 30 inches from the Y pipe. Then once you are there you can adjust on the dyno back and forth untill you hit it where you need it. Another way to do this is to install teh cutout closer to the motor and then add on a long pipe to the end of teh cut out. Then start cutting off the pipe inch by inch while dynoing untill you find the distence that will set you into the band that you want to run. The point here is knowing that where and when the exhaust exits to atmospehere. there could easily be a change of .1-.3 from correctly tuning like this.

[Turbo V6 Camaro]

Originally posted by HBHRacing:
The best thing for you to do (when boosted) is to get your exhaust flow out as fast and possible. No cat, and preferably a cutout before the muffler. What you need to do then is to adjust your cutout location to best suit your RPM window. You tune the cutout distence based on where you want your power. The "general" starting point for 4000-6000 RPM band is 30 inches from the Y pipe. Then once you are there you can adjust on the dyno back and forth untill you hit it where you need it. Another way to do this is to install teh cutout closer to the motor and then add on a long pipe to the end of teh cut out. Then start cutting off the pipe inch by inch while dynoing untill you find the distence that will set you into the band that you want to run. The point here is knowing that where and when the exhaust exits to atmospehere. there could easily be a change of .1-.3 from correctly tuning like this.

DOES THIS apply for turbo apps? i would the back PSI from the turbo would be all you would want and after the turbo you would want non so it spools well

[HBHRacing]

I'm not great with Turbo stuff, I mostly know superchargers. But my understanding is when you have the exhaust exit you still want it exactly like I said. That will allow the turbo to spool well and not hold back. I know that when you put a good exhaust set up thats correctly tuned on a SC'ed set up you can show a little less boost as per teh gauge. However the system is more efficant then it was.

[Predator Bird]

look what you started eric. i swear to god i'm gonna pistol whip the next guy who says shenanigans.

[BLLDOGG]

HBHRacing, everything you say is correct about placement and what not but most people on this board will not go through what you say just for that .1-.3tenths. only die hard racers with actually fast cars do crap like that. i swear, you have to be apart of a pro drag team. [img]tongue.gif[/img]

[Turbo V6 Camaro]

shenanigans has good food [img]graemlins/banana.gif[/img]

[HBHRacing]

Love the Mozzarella sticks....


I am glad that people (especialy people that faught me so hard on the last thread like this) are starting to see the light. It takes a LONG time to change a learned behavior. The learned behavior here is that 3 inch is better. Since it's spread like an epidemic it's so hard to stop. honestly all someone needs to do is look at the FACTS and it's easy to think to yourself "hey, there might be something about this". Wehn I post things about this people take it like I just told them that I slept with thier mother. To them it's personal. Which I have no idea why. But that doesn't change the fact that the general statment that 3 inch will perform better then 2.5 is just false. Sure, there is a time when 3 inch will do better. But that time is pretty far away for most NA 3.8's

Myself, I would LOVE to do something that would net me .1-.3. That could mean the difference between a 13.2 and a 12.9 or a 12.7 and a 12.5. Especialy when you figure that it's not going to cost you anymore. you just have to do it right the first time. Exhaust is so often overlooked. People do it wrong so many times. too big of pipe, keeping the restrictive cats, wasting money on a bad flowing muffler, not giving cut out placment any thought ect. But all it takes is a little bit of time and thought and you don't even have to change anything. Just do it right the first time and you will be set.

Like I said long ago. I don't care what people do with this information. As long as they understand it it's up to them to use it or not. But now you understand when someone asks if 3 inch is better and I say no, that I have my reasons. And these reasons are good and correct. Maybe a few more of you will conceed some of this and help me out. even "if you want sound go with 3 inch, if you want performance go with 2.5 inch" would be a HUGE step forword. Even point people to this thread so that they can read why it is the way that it is and make teh choice for themselves. Forcing the 3 inch on people will simply extend the epidemic further then it is already untill it takes on a life of it's own.

[FirebirdGT]

Originally posted by HBHRacing:
"if you want sound go with 3 inch, if you want performance go with 2.5 inch"

OR - have BOTH with a B&B 2.5" V6 cat-back. I have an article on my site with dyno results.

:D

[HBHRacing]

Sweet, I didn't knw that B&B made a 2.5. I like the way that thier V8 cat back sounds. I like the magnaflow sound to but I would like to hear the B&B.


Thanks [img]smile.gif[/img]

[shenanigans]

Originally posted by Predator Bird:
look what you started eric. i swear to god i'm gonna pistol whip the next guy who says shenanigans.

LOL to think it all started from some guy asking if a 3.8L camaro is a good Daily driver.

[Red]

i got full 3 exhaust and it is overkill for my car currently. Slow to go but a great punch at around 30-40 mph. Luckily i will be going turbo sometime which should help.