Risks of running 3.5 inch exhaust
11-17-09, 01:42 PM
#26
BLUE TII, were you running a big FMIC when you experienced boost creep? I'm just thinking of the equation for mass flow which is m=(Density)(Velocity)(Area). A bigger intercooler will considerably increase the density which could also cause the boost creep you were experiencing with the Bullit 90 & could also explain why I wasn't creeping with the stock wastegate (stock TMIC).
12-12-09, 01:53 AM
#31
Well here's an update guys. Got my turbo and exhaust on last night. Running an s5 hybrid turbo with just the stock dual wastegates in 32 degree weather and held 5 psi steady all the way through the power band, even during some highway pulls.
Fastest 5psi I've ever felt in my life though!! lol. My friend who helped said he has ridden in a fully built twin turbo mustang that didn't feel as fast as my car did on low boost. Man I love these motors (while they last that is).
Fastest 5psi I've ever felt in my life though!! lol. My friend who helped said he has ridden in a fully built twin turbo mustang that didn't feel as fast as my car did on low boost. Man I love these motors (while they last that is).
12-12-09, 11:46 AM
#33
I got it from a friend down the street (member of rx7club) who ordered it new from Japan. I don't think many of them were made cuz, like you, I can't find any information of it for the life of me.
Surprisingly, when not in boost it has a very deep sexy tone to it. But when you get into boost it sounds glorious, and very loud...but at the same time its not raspy loud like rotaries sometime get, going through bridge underpasses on the highway sounds cool too, everything resonates. But ya, the fitment is practically perfect, doesn't rattle, doesn't move, and most importantly hasn't creeped...yet. I don't know why they discontinued them, cuz it puts my Racing beat to shame
Surprisingly, when not in boost it has a very deep sexy tone to it. But when you get into boost it sounds glorious, and very loud...but at the same time its not raspy loud like rotaries sometime get, going through bridge underpasses on the highway sounds cool too, everything resonates. But ya, the fitment is practically perfect, doesn't rattle, doesn't move, and most importantly hasn't creeped...yet. I don't know why they discontinued them, cuz it puts my Racing beat to shame
12-17-09, 04:08 PM
#34
I take that last statement back about not knowing why they discontinued this system...It's just too loud guys...looking for an efficient way to silence this thing quick, it's actually vibrating my interior apart and can set off car alarms at idle. Who would have thought 1.3L can cause such a ruckus! lol
12-18-09, 06:19 AM
#36
Not at all, it doesn't creep and spools faster than my stock turbo. If it wasn't for the sound I wouldn't have any complaints. I can put the car sideways half throttle in first gear at 3k rpms on 5psi, lets see u do that with a 3" exhaust.
12-18-09, 09:34 AM
#37
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I would try a good exhaust shop or rotary shop. Have them weld a high-flow muffler or other sound-supressing device in. it will probably cost you around $150 which you will quickly make back in the tickets that you do not get.
12-18-09, 12:43 PM
#38
wtf is the point of a big exhaust with a huge restriction in it? Why don't you engineer a complete system instead of throwing parts together?
Because on a turbo car the large piping (low backpressure) allows the turbo to spool much more easily so you GAIN low and midrange power.
The restriction at the very end of the exhaust limits total flow of the system which only impacts the power at the top end where you would have the boost creep. The key is to restrict it enough to limit boost creep and no more.
For instance I found the 3 1/2" JIC Magic w/ its tip silencer in (about 2" exhaust outlet) spools much faster than the full 3" Racing Beat turbo back. Both could limit top end flow to the point where I didn't have boost creep.
Because on a turbo car the large piping (low backpressure) allows the turbo to spool much more easily so you GAIN low and midrange power.
The restriction at the very end of the exhaust limits total flow of the system which only impacts the power at the top end where you would have the boost creep. The key is to restrict it enough to limit boost creep and no more.
For instance I found the 3 1/2" JIC Magic w/ its tip silencer in (about 2" exhaust outlet) spools much faster than the full 3" Racing Beat turbo back. Both could limit top end flow to the point where I didn't have boost creep.
12-18-09, 03:00 PM
#39
I'm gonna give this a try http://www.clubrsx.com/cr/APE-155-A0...mpaign=froogle
12-18-09, 03:31 PM
#40
Did you experience any boost creep with the 3.5 exhaust? If so what setup were u running?
Yes, I had major boost creep if I took the tip silencer out!
Set up is a S5 based BNR Stage 4 hybrid turbo.
Started with clipped "O" trim exhaust and standard ported wastegates- insane boost creep.
Went to larger clipped "P" trim exhaust wheel and externally vented stock wastegates ported out as large as possible- still had boost creep.
Went to 60mm external wastegate and wastegate passages ported out to the limit of the turbo housing casting- still had boost creep.
Finally ported the turbo manifold and runners huge to favor wastegate flow over turbine flow, back welded the turbo housing so WG runners could be ported more and no more boost creep. Went back to unclipped "P" trim exhaust wheel.
Yes, I had major boost creep if I took the tip silencer out!
Set up is a S5 based BNR Stage 4 hybrid turbo.
Started with clipped "O" trim exhaust and standard ported wastegates- insane boost creep.
Went to larger clipped "P" trim exhaust wheel and externally vented stock wastegates ported out as large as possible- still had boost creep.
Went to 60mm external wastegate and wastegate passages ported out to the limit of the turbo housing casting- still had boost creep.
Finally ported the turbo manifold and runners huge to favor wastegate flow over turbine flow, back welded the turbo housing so WG runners could be ported more and no more boost creep. Went back to unclipped "P" trim exhaust wheel.
12-30-09, 09:28 AM
#41
Sooooo......
A friend of mine found a minor boost leak from the turbo to the bov & after fixing that, no more 5psi pulls. It's slowly creeping now and pulls like CRAZY!!
Did a 3rd and 4th gear pull with a buddy of mine's TII, his is streetported with a BNR stage I on 10 psi, 3" exhaust. We started in 3rd gear at 60mph and I was maybe 3/4 throttle to prevent creep & put his front bumper by my side view mirror and with the excitement of the new found speed went full throttle in 4th under shifting at 6k but still put him in my rear view mirror by the time I hit ~110+ mph. Even after taking his for a drive I noticed mine has much less lag, tons more bottum end, similar mid range, and a lot more up top. So its safe to say the 3.5 exhaust is money well spent, just need some more safety mods before I do anymore serious racing
A friend of mine found a minor boost leak from the turbo to the bov & after fixing that, no more 5psi pulls. It's slowly creeping now and pulls like CRAZY!!
Did a 3rd and 4th gear pull with a buddy of mine's TII, his is streetported with a BNR stage I on 10 psi, 3" exhaust. We started in 3rd gear at 60mph and I was maybe 3/4 throttle to prevent creep & put his front bumper by my side view mirror and with the excitement of the new found speed went full throttle in 4th under shifting at 6k but still put him in my rear view mirror by the time I hit ~110+ mph. Even after taking his for a drive I noticed mine has much less lag, tons more bottum end, similar mid range, and a lot more up top. So its safe to say the 3.5 exhaust is money well spent, just need some more safety mods before I do anymore serious racing
12-31-09, 08:43 PM
#42
Braggin about your 3.5in exhaust now ha ha....I may not quite able to put my car sideways in first at 3k rpm and 5psi. But my car is pretty much useless from 1st thru practically 3rd gear with a 3 in exhaust so what now ha ha.
Oh and what safety mods are you talking about Willis?! ha
12-31-09, 11:15 PM
#43
Braggin about your 3.5in exhaust now ha ha....I may not quite able to put my car sideways in first at 3k rpm and 5psi. But my car is pretty much useless from 1st thru practically 3rd gear with a 3 in exhaust so what now ha ha.
Oh and what safety mods are you talking about Willis?! ha
Oh and what safety mods are you talking about Willis?! ha
for safety mods I'm gonna need a wideband, water injection, rtek 2.1, and 1000cc secondaries...then I'll feel more comfortable going full throttle
01-08-10, 12:25 PM
#44
Quote:
Originally Posted by BLUE TII
wtf is the point of a big exhaust with a huge restriction in it? Why don't you engineer a complete system instead of throwing parts together?
Because on a turbo car the large piping (low backpressure) allows the turbo to spool much more easily so you GAIN low and midrange power.
The restriction at the very end of the exhaust limits total flow of the system which only impacts the power at the top end where you would have the boost creep. The key is to restrict it enough to limit boost creep and no more.
For instance I found the 3 1/2" JIC Magic w/ its tip silencer in (about 2" exhaust outlet) spools much faster than the full 3" Racing Beat turbo back. Both could limit top end flow to the point where I didn't have boost creep.
-------------------------------------
i find that strange, since larger exhaust is supposed to increase top end power while increasing spool time(reduced low end power). i do think the change was in your head, not in the car. that or the exhaust had that much more restriction somewhere else, not putting it on the size of the piping.
That is not how it works on any turbo car.
You are correct that in a natually aspirated car if the exhaust diameter is too big velocity drops off and you get pulsation in the exaust so the piston/rotor has to keep pushing back on the exhaust reversions to keep the flow moving in the right direction costing you power in the low rpm.
With a turbo however, there is no pulsation in the exhaust from the turbo back so the larger diameter pipe simply increases the pressure differential between the inlet and outlet side of the turbo.
Increasing spool and helping the low end power.
Originally Posted by BLUE TII
wtf is the point of a big exhaust with a huge restriction in it? Why don't you engineer a complete system instead of throwing parts together?
Because on a turbo car the large piping (low backpressure) allows the turbo to spool much more easily so you GAIN low and midrange power.
The restriction at the very end of the exhaust limits total flow of the system which only impacts the power at the top end where you would have the boost creep. The key is to restrict it enough to limit boost creep and no more.
For instance I found the 3 1/2" JIC Magic w/ its tip silencer in (about 2" exhaust outlet) spools much faster than the full 3" Racing Beat turbo back. Both could limit top end flow to the point where I didn't have boost creep.
-------------------------------------
i find that strange, since larger exhaust is supposed to increase top end power while increasing spool time(reduced low end power). i do think the change was in your head, not in the car. that or the exhaust had that much more restriction somewhere else, not putting it on the size of the piping.
That is not how it works on any turbo car.
You are correct that in a natually aspirated car if the exhaust diameter is too big velocity drops off and you get pulsation in the exaust so the piston/rotor has to keep pushing back on the exhaust reversions to keep the flow moving in the right direction costing you power in the low rpm.
With a turbo however, there is no pulsation in the exhaust from the turbo back so the larger diameter pipe simply increases the pressure differential between the inlet and outlet side of the turbo.
Increasing spool and helping the low end power.
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