My Personal Thoughts on Exhaust and FI
11-18-2005, 03:25 AM
#21
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exhaust on turbo cars are one of the biggest things you can do to add it will help you more then hurt you. one thing you may want to think about is a exhaust cut out connected with a switch
11-18-2005, 04:41 AM
#22
I have seen it go both ways. I remember a member on here put a Borla on a T-netics kit and gained like 30 whp and good TQ lower in the powerband but peak didnt move. I have also seen some cars peak higher, because even though still at same boost, the motor ran more efficiently because of less back pressure. You see this a lot with TT kits and adding test-pipes, boost wont move but peak WILL go up....
11-18-2005, 05:27 AM
#23
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Back pressure slows down the turbine on the turbo so freeing up the exhaust and removing the back pressure allows the turbine to spool easier, yes the wastegates control the boost but it is not an on off switch so even though the watsegate will try to control the boost the turbo(s) will spin a llittle easier and therefore go a little higher before the wastegate catches it and you will get a slightly higher boost.
11-18-2005, 05:28 AM
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I fully beleive that me having a true dual 3" (aka ~no backpressure post turbos) is what made my car achieve 424 rwhp at only 7.5 psi at redline. My car at only 2psi less and factory tune with stock exhaust (minus testpipes) made 345 rwhp. 80whp increase with only a 2psi boost increase + tuning is awesome if you ask me.
11-18-2005, 06:34 AM
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It would be cool if we could get flow specs from exhaust manufacturers. While an exhaust system may have 3" piping, if it has a big azz muffler at the end of it you have no idea how much its going to flow. A good example is the Nismo exhaust which has 3" piping with a stock-like muffler, who knows how restrictive that muffler at the end is. Does it flow better than stock? How much better?
How about the Fujitsubo, Apexi, or even the Amuse? Seems like the universal types flow better but how do we compare the actual flow rates?
How about the Fujitsubo, Apexi, or even the Amuse? Seems like the universal types flow better but how do we compare the actual flow rates?
11-18-2005, 06:49 AM
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the not increasing torque thing, is relevant to the engine that has a turbo. B-series engine for hondas will continue to make more and more torque towards redline.
It all depends on engine design, intake manifold design, ect.
It all depends on engine design, intake manifold design, ect.
11-18-2005, 07:37 AM
#28
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JET.. it's an easy test.. jack up your car and unbolt your B-pipe off your exhaust, then take your car out for a spin and let us know what you think.
I'll tell you right now what you'll feel. Turbo will spool VERY noticeably faster, therefore resulting in much earlier torque in the powerband, holding the power for longer. In an ideal world, on any turbocharged car, you'll make the most whp and wtq throughtout the powerband (not just peak) by having no exhaust at all, resulting on zero backpressure.
Backpressure slows the exhaust gas out the car. As westpak also said, the more and faster you get air in and out of the engine, the more horsepower you will make. So backpressure slows down spool and could even reduce peak boost compared to a free flow larger diameter exhaust.
When it comes to turbo cars, exhaust systems are in NO way comparable to normally aspirated.
Also, keep in mind that larger diameter doesn't always mean lower backpressure! Having a larger diameter compared to stock is only part of the equation. You also need a free flow muffler (preferably straight through without splitting), and the least amount of bends possible.
If you kept the same exact design as stock but go to a larger diameter, you'll make more power.
If you kept the same exact design as stock and STOCK diameter, but eliminate some of the bends, you'll make more power.
If you kept the same exact design as stock but just change to a muffler with less back pressure, you'll make more power.
If you do all 3 above, you'll make the most out of your exhaust system. The more and faster exhaust gas exits the system, the better in a turbo car.
I'll tell you right now what you'll feel. Turbo will spool VERY noticeably faster, therefore resulting in much earlier torque in the powerband, holding the power for longer. In an ideal world, on any turbocharged car, you'll make the most whp and wtq throughtout the powerband (not just peak) by having no exhaust at all, resulting on zero backpressure.
Backpressure slows the exhaust gas out the car. As westpak also said, the more and faster you get air in and out of the engine, the more horsepower you will make. So backpressure slows down spool and could even reduce peak boost compared to a free flow larger diameter exhaust.
When it comes to turbo cars, exhaust systems are in NO way comparable to normally aspirated.
Also, keep in mind that larger diameter doesn't always mean lower backpressure! Having a larger diameter compared to stock is only part of the equation. You also need a free flow muffler (preferably straight through without splitting), and the least amount of bends possible.
If you kept the same exact design as stock but go to a larger diameter, you'll make more power.
If you kept the same exact design as stock and STOCK diameter, but eliminate some of the bends, you'll make more power.
If you kept the same exact design as stock but just change to a muffler with less back pressure, you'll make more power.
If you do all 3 above, you'll make the most out of your exhaust system. The more and faster exhaust gas exits the system, the better in a turbo car.
11-18-2005, 08:14 AM
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Originally Posted by 002-M-P
I fully beleive that me having a true dual 3" (aka ~no backpressure post turbos) is what made my car achieve 424 rwhp at only 7.5 psi at redline. My car at only 2psi less and factory tune with stock exhaust (minus testpipes) made 345 rwhp. 80whp increase with only a 2psi boost increase + tuning is awesome if you ask me.
11-18-2005, 09:18 AM
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Originally Posted by bigbri
NIce power by the way bro at 7.5psi nice.....
11-18-2005, 09:39 AM
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Originally Posted by 35ounces
It would be cool if we could get flow specs from exhaust manufacturers. While an exhaust system may have 3" piping, if it has a big azz muffler at the end of it you have no idea how much its going to flow. A good example is the Nismo exhaust which has 3" piping with a stock-like muffler, who knows how restrictive that muffler at the end is. Does it flow better than stock? How much better?
How about the Fujitsubo, Apexi, or even the Amuse? Seems like the universal types flow better but how do we compare the actual flow rates?
How about the Fujitsubo, Apexi, or even the Amuse? Seems like the universal types flow better but how do we compare the actual flow rates?
I'm interested in this as well. I'm hittin 9-9.5psi with the Fujitsubo exhaust, and the wastegate is supposed to be regulated to 8.5psi on a stock exhaust setup. This leads me to beleive that the fujitsubo is, in fact, a more free flowing exhaust. But, I'm still making around the same power as some people on these forums with this kit on a stock exhaust.
I'm very interested in seeing just how well the Fujitsubo/Nismo exhausts actually flow compared to some of the other exhausts on the market. I've been considering dropping my Pro-1 exhaust back on when I find the time to see if I can tell a difference in power. But, I don't really like the sound of the Pro-1... I'm not sure if I'd be willing to swap out the sweet sounding fuji for a loud exhaust that gives me 5 more whp.
So does anyone think I'd be better off with the Pro-1 on the car? hhmmmm....
11-18-2005, 09:51 AM
#32
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Go on the APS website (unlinkable) and lookup the Z ST kit. Click on the link for the exhaust system for that kit. At the bottom of that page there is a writeup on this subject.
Last edited by dirtroad; 11-18-2005 at 09:54 AM.
11-20-2005, 08:22 AM
#33
Couple points of clarification.
The typical internally gated turbo is more sensative to exhaust back pressure. A larger diameter external wastegate is going to result in better boost response, and more accurate boost stabality. When you put a super free flowing exhuast on an internally gated turbo, you tend to get more boost, vs. doing this on an externally gated turbo.
Second, a free flowing exhaust provides several key benifits.
Reduced exhuast back pressure. What the hell does this mean? It means that you have significantly reducing the thermal load on the motor, and will allow you to run more timing advance, and less boost, to acheive the same power goal. The cars we tune all have large 2.5 or 3 inch true dual exhuasts, and they are making awesome power at just 7-8psi of boost pressure....depending on their other mods. If you slap a restrict exhuast on that thing, you will need to run more boost to acheive those numbers. Restrictive exhuast contribute to engine overheat, detonation, and power losses up top. They do tend to spike the trq down low. A good sign of a restrictive exhuast and/or too little timing advance is a trq number that is significantly higher than the whp number.
With the TN singles, a good solution is a 3 inch single pipe all the way back. Peking's car had this, and after unbolting his exhuast, there was no increase in power....perfect indication of a zero backpressure exhuast at the pressure level we were running...about 9psi.
Keep in mind that zero backpressure must be stated in reference to the boost pressure used. A zero backpressure exhuast at 10psi can be very restrictive at 15psi.
The typical internally gated turbo is more sensative to exhaust back pressure. A larger diameter external wastegate is going to result in better boost response, and more accurate boost stabality. When you put a super free flowing exhuast on an internally gated turbo, you tend to get more boost, vs. doing this on an externally gated turbo.
Second, a free flowing exhaust provides several key benifits.
Reduced exhuast back pressure. What the hell does this mean? It means that you have significantly reducing the thermal load on the motor, and will allow you to run more timing advance, and less boost, to acheive the same power goal. The cars we tune all have large 2.5 or 3 inch true dual exhuasts, and they are making awesome power at just 7-8psi of boost pressure....depending on their other mods. If you slap a restrict exhuast on that thing, you will need to run more boost to acheive those numbers. Restrictive exhuast contribute to engine overheat, detonation, and power losses up top. They do tend to spike the trq down low. A good sign of a restrictive exhuast and/or too little timing advance is a trq number that is significantly higher than the whp number.
With the TN singles, a good solution is a 3 inch single pipe all the way back. Peking's car had this, and after unbolting his exhuast, there was no increase in power....perfect indication of a zero backpressure exhuast at the pressure level we were running...about 9psi.
Keep in mind that zero backpressure must be stated in reference to the boost pressure used. A zero backpressure exhuast at 10psi can be very restrictive at 15psi.
11-20-2005, 02:30 PM
#34
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Interesting. My Torque is in fact much higher than the WHP. So either the NISMO exhaust is restrictive (as I surmise) or there is too little timing advance for my car in that TN reflash.
11-20-2005, 05:58 PM
#35
Originally Posted by 35ounces
Interesting. My Torque is in fact much higher than the WHP. So either the NISMO exhaust is restrictive (as I surmise) or there is too little timing advance for my car in that TN reflash.
11-20-2005, 07:27 PM
#36
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Originally Posted by Sharif@Forged
With the TN singles, a good solution is a 3 inch single pipe all the way back. Peking's car had this, and after unbolting his exhuast, there was no increase in power....perfect indication of a zero backpressure exhuast at the pressure level we were running...about 9psi.
I'm assuming Jet has a different exhaust then the 3" exhaust Peking is using. That's why I suggested he disconnects his B pipe and takes it out for a test drive to see the difference first hand.
Although a short test drive on his part wouldn't be too dangerous on stock Turbonetics tune (plenty rich I hear), I'd obviously suggest a retune with a free flow setup, assuming he's still running stock exhaust.
11-20-2005, 07:56 PM
#37
Originally Posted by mojo powered
nice, thanks Sharif for the explanation, very thorough
I'm assuming Jet has a different exhaust then the 3" exhaust Peking is using. That's why I suggested he disconnects his B pipe and takes it out for a test drive to see the difference first hand.
Although a short test drive on his part wouldn't be too dangerous on stock Turbonetics tune (plenty rich I hear), I'd obviously suggest a retune with a free flow setup, assuming he's still running stock exhaust.
I'm assuming Jet has a different exhaust then the 3" exhaust Peking is using. That's why I suggested he disconnects his B pipe and takes it out for a test drive to see the difference first hand.
Although a short test drive on his part wouldn't be too dangerous on stock Turbonetics tune (plenty rich I hear), I'd obviously suggest a retune with a free flow setup, assuming he's still running stock exhaust.
11-21-2005, 06:18 AM
#38
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that is also true.. I personally don't believe 10-15whp difference isn't THAT much of a difference on the butt dyno, but man that exhaust sound sure would feel like it added ~100whp. haha
sure would feel like it added ~100whp. haha
11-21-2005, 04:53 PM
#39
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Originally Posted by mojo powered
nice, thanks Sharif for the explanation, very thorough
I'm assuming Jet has a different exhaust then the 3" exhaust Peking is using. That's why I suggested he disconnects his B pipe and takes it out for a test drive to see the difference first hand.
Although a short test drive on his part wouldn't be too dangerous on stock Turbonetics tune (plenty rich I hear), I'd obviously suggest a retune with a free flow setup, assuming he's still running stock exhaust.
I'm assuming Jet has a different exhaust then the 3" exhaust Peking is using. That's why I suggested he disconnects his B pipe and takes it out for a test drive to see the difference first hand.
Although a short test drive on his part wouldn't be too dangerous on stock Turbonetics tune (plenty rich I hear), I'd obviously suggest a retune with a free flow setup, assuming he's still running stock exhaust.
