Vortech + T.D. = ??
06-27-2006, 09:10 AM
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Originally Posted by sentry65
you possibly will I think if you're not pushing very much power and using the stock 3.33 pulley
06-27-2006, 09:44 AM
#4
Try drinking thru a straw with a 2 inch diameter - you won't generate enough suction force to pull the water thru to your mouth - really it's that simple
if you add a big pipe exhaust and have a centrifugal supercharger that does not make full boost until 5000 rpms, you will not be able to fill up enough pressure in the exhaust below 5000 rpms to get good torque. A turbo makes full boost at 3500-4000 rpms and that's right about where the engine starts making peak torque so turbos get a crapload of torque - which in turn runs more risk or breaking a rod
torque is horsepower without rpms factored in
if you add a big pipe exhaust and have a centrifugal supercharger that does not make full boost until 5000 rpms, you will not be able to fill up enough pressure in the exhaust below 5000 rpms to get good torque. A turbo makes full boost at 3500-4000 rpms and that's right about where the engine starts making peak torque so turbos get a crapload of torque - which in turn runs more risk or breaking a rod
torque is horsepower without rpms factored in
Last edited by sentry65; 06-27-2006 at 09:48 AM.
06-28-2006, 04:14 AM
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Boost is not the most important thing in making power.. It's air flow through the engine..Having a larger exhaust reduces the backpressure and boost but allows more air to flow ..The S/C would spin faster thereby pushing more air ...There is an obvious limit to airflow (min backpressure) before the engine begins to lose power. What I would like to know is how can you determine when you are reaching that airflow limit..
06-28-2006, 05:10 AM
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Great post guys....but I have a simple question: I have made my decision to work towards a Vortech. I currently have the Injen SES TD exhaust. Are you telling me that it may decrease my HP/TQ vs. say my Stock exhaust? I am very interested to know the answer to jpc350z question as well.....
06-28-2006, 07:52 AM
#7
i'd just go for it and see where you end up. Dyno the car and tune it and post up some dyno charts and see what the car feels like before making exhaust decisions when you've already bought one. I think a dual is perfectly fine.
getting test pipes and a dual exhaust might be ok or it might not be the best choice on a stock vortech install - hard to say
getting test pipes and a dual exhaust might be ok or it might not be the best choice on a stock vortech install - hard to say
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06-28-2006, 09:20 AM
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I guess I could try trial and error but prefer to not spend 1k+ and be disappointed.. Question is a fundamental one to S/C F.I. and my hope was some knowledgeable experienced guru would point me to the answer..Still hoping!! By the way I have the 3.12 and will change it to the 2.87..
06-28-2006, 09:38 AM
#9
well mcduck was running a borla dual exhaust last I heard and he was making huge power, though he's running a lot of boost on a built engine.
I think if you lose any low end power at all, it'll only be in the neighborhood of a few hp/tq. And you'll gain it all back and then some up high
I think if you lose any low end power at all, it'll only be in the neighborhood of a few hp/tq. And you'll gain it all back and then some up high
06-28-2006, 09:42 AM
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Don't believe Mc Duck had a built engine.. Whatever happened to him, he use to a frequent poster..I don't wanna loose an ounce of low power the only reason for doing it is to make more low end...and some more overall, but not expecting any huge gain..
07-12-2006, 09:24 PM
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I'm thinking about adding some exhaust mods to my 3.12 pulley vortech setup as well. I'm on completely stock exhaust right now w/ 380hp/320tq. How much gains would I see from upgrading the exhaust? I'm at 9lb of boost right now, that would go down a bit with exhaust breather mods and increase hp. What is more risky for the motor for our setups, higher boost or higher hp? Sentry or booger? I'd pm you guys but i'm sure there are others who want to know your responses. Thanks
07-12-2006, 11:12 PM
#12
I wouldn't concern yourself with boost pressure so much with a supercharger cause no matter what you do to the exhaust the SC is going to still pump the same amount of air into the engine. However high psi is bad on the engine because it basically reflects how clogged the engine is at moving air thru it with only 3.5 liters. If you upgrade the pulley on the SC to blow more air (and add more fuel) then you're filling the cylinders with more stress which is relected by the boost gauge because all that gauge measures is pressure - not air volume.
it's a totally different situation with a turbo where the psi is always saturated to the maximum amount that the wastegate limits the boost to. You can add in a bigger exhaust on a turbo and the turbo will still push the same psi thru and bleed less excess boost out the wastegate.
With the supercharger setup, the boost amount is more finite because the supercharger only makes so much boost. It doesn't have excess amounts of boost available to keep the psi up high like a turbo.
with a supercharger, adding a more open exhaust I don't think actually stresses the engine any harder. It trades boost pressure for hp. Either way that air is moving thru the engine, except the bigger exhaust lets the air out easier/faster which in turn lets the heat out easier/faster. It will push your powerband into the higher rpm range though so you might lose a little bit of low or even midrange power.
It's exactly the same thing as people with civics and 5 inch exhausts - the engine pumps the same air, but ends up moving the powerband so far up that it's actually beyond the rpms the engine is capable of and thus loses power. Or the guy with a V8 who puts huge huge race cams on the car that are designed to make power at 10,000 rpms and ends up losing all their low and midrange power.
as far as gains, I'd expect to gain 10-20whp depending on what exhaust you get and lose maybe 1psi of boost pressure
here's a decent link on the same concepts only about headers which is the same sorta thing only earlier in the exhaust chain
http://superchevy.com/technical/engi...0504sc_header/
it's a totally different situation with a turbo where the psi is always saturated to the maximum amount that the wastegate limits the boost to. You can add in a bigger exhaust on a turbo and the turbo will still push the same psi thru and bleed less excess boost out the wastegate.
With the supercharger setup, the boost amount is more finite because the supercharger only makes so much boost. It doesn't have excess amounts of boost available to keep the psi up high like a turbo.
with a supercharger, adding a more open exhaust I don't think actually stresses the engine any harder. It trades boost pressure for hp. Either way that air is moving thru the engine, except the bigger exhaust lets the air out easier/faster which in turn lets the heat out easier/faster. It will push your powerband into the higher rpm range though so you might lose a little bit of low or even midrange power.
It's exactly the same thing as people with civics and 5 inch exhausts - the engine pumps the same air, but ends up moving the powerband so far up that it's actually beyond the rpms the engine is capable of and thus loses power. Or the guy with a V8 who puts huge huge race cams on the car that are designed to make power at 10,000 rpms and ends up losing all their low and midrange power.
as far as gains, I'd expect to gain 10-20whp depending on what exhaust you get and lose maybe 1psi of boost pressure
here's a decent link on the same concepts only about headers which is the same sorta thing only earlier in the exhaust chain
http://superchevy.com/technical/engi...0504sc_header/
Last edited by sentry65; 07-12-2006 at 11:18 PM.
07-13-2006, 06:02 AM
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The issue with power loss on larger diameter exhausts is that a supercharger and turbocharger are different when it comes to how they generate boost. When you add a larger diameter exhaust on a turbo car, you will always be able to generate more hp because the car now relies on the exhaust being able to spin the turbos. On a supercharged car, by adding a larger exhaust, all you are doing is relieving the backpressure on the car. You will see a loss on this because the supercharger's air is generated by a belt and has nothing to do with the exhaust system. Therefore in essence, your exhaust system is still that of an N/A vehicle and should be treated as such.
07-13-2006, 08:50 AM
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great explaination
Originally Posted by THE TECH
The issue with power loss on larger diameter exhausts is that a supercharger and turbocharger are different when it comes to how they generate boost. When you add a larger diameter exhaust on a turbo car, you will always be able to generate more hp because the car now relies on the exhaust being able to spin the turbos. On a supercharged car, by adding a larger exhaust, all you are doing is relieving the backpressure on the car. You will see a loss on this because the supercharger's air is generated by a belt and has nothing to do with the exhaust system. Therefore in essence, your exhaust system is still that of an N/A vehicle and should be treated as such.
07-13-2006, 08:58 AM
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Originally Posted by THE TECH
The issue with power loss on larger diameter exhausts is that a supercharger and turbocharger are different when it comes to how they generate boost. When you add a larger diameter exhaust on a turbo car, you will always be able to generate more hp because the car now relies on the exhaust being able to spin the turbos. On a supercharged car, by adding a larger exhaust, all you are doing is relieving the backpressure on the car. You will see a loss on this because the supercharger's air is generated by a belt and has nothing to do with the exhaust system. Therefore in essence, your exhaust system is still that of an N/A vehicle and should be treated as such.
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