Low boost - 2.5" or 3" exhaust? (i searched)
01-12-2003, 11:57 AM
#1
0.5 BAR
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Join Date: Dec 2002
Posts: 93
Low boost - 2.5" or 3" exhaust? (i searched)
Hi, I searched with no results? And all i typed in was "exhaust"
Anyway, after monkeying around with the upteen T3 turbos, I decided I am going to buy a T3/T4 from this one guy. BTW this is the turbo, does it look ok in this pic?
Will I be able to keep AC?
And back to my original Q, I plan on boosting 6-7psi with Fuel management with VAFC hack. Should I go with 2.5 or 3" exhaust?
Anyway, after monkeying around with the upteen T3 turbos, I decided I am going to buy a T3/T4 from this one guy. BTW this is the turbo, does it look ok in this pic?
Will I be able to keep AC?
And back to my original Q, I plan on boosting 6-7psi with Fuel management with VAFC hack. Should I go with 2.5 or 3" exhaust?
01-12-2003, 02:42 PM
#3
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Join Date: Dec 2002
Posts: 13,991
Re:Low boost - 2.5" or 3" exhaust? (i searched)
I use to have that same turbo, now beau has it... havent even tried it yet.
what is the a/r on the turbine side?
It all depends on the manifold if it will work with AC. More than likly its going to have to be a custom manifold.
Jeff
what is the a/r on the turbine side?
It all depends on the manifold if it will work with AC. More than likly its going to have to be a custom manifold.
Jeff
01-12-2003, 02:53 PM
#7
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Re:Low boost - 2.5" or 3" exhaust? (i searched)
Originally Posted by PhoenixGSR
a 3" exhaust will make more power, but it will be a lot louder.. your choice
Jeff
01-12-2003, 03:12 PM
#8
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Posts: n/a
Re:Low boost - 2.5" or 3" exhaust? (i searched)
I read some conflicting info on this.. Well at least conflicted with my own belife's.
Something to understand is boost pressure isn't the end all be all. It is quite possible to have more power with less boost pressure on otherwise identical engines. A turbo which is forced to work outside its peak efficiency range is not going to provide as much power. This is why turbocharger selection is so important. It's all about compromises.
Problems
-Sluggish boost rise at low RPM's may mean the A/R is too large, while quick response which causes driveablility problems can be an A/R that is too small.
-Power tapering off at higher RPM's can be a sign of the extruder outlet being too small which is causing high back-pressure between the engine and the turbine. Or an improperly sized turbocharger that is working too hard.
What size exhaust pipe should be used? 2.5" ID pipe is plenty for street use, 2.75" ID at a maximum. Not much of a muffler is required as well, I would not recommend skipping the muffler for the street though.
this info from a page on turboing the bmw m10 can be found at http://320i.com/turbocharging.htm
Something to understand is boost pressure isn't the end all be all. It is quite possible to have more power with less boost pressure on otherwise identical engines. A turbo which is forced to work outside its peak efficiency range is not going to provide as much power. This is why turbocharger selection is so important. It's all about compromises.
Problems
-Sluggish boost rise at low RPM's may mean the A/R is too large, while quick response which causes driveablility problems can be an A/R that is too small.
-Power tapering off at higher RPM's can be a sign of the extruder outlet being too small which is causing high back-pressure between the engine and the turbine. Or an improperly sized turbocharger that is working too hard.
What size exhaust pipe should be used? 2.5" ID pipe is plenty for street use, 2.75" ID at a maximum. Not much of a muffler is required as well, I would not recommend skipping the muffler for the street though.
this info from a page on turboing the bmw m10 can be found at http://320i.com/turbocharging.htm
01-12-2003, 03:39 PM
#9
0.5 BAR
Thread Starter
Join Date: Dec 2002
Posts: 93
Re:Low boost - 2.5" or 3" exhaust? (i searched)
The A/R on the exhaust is .48, and .70 on the compressor. This thing looks huge. As far as a manifold, I will be getting a DRAG or REVHARD or FMAX (which all claim to retain A/C. I just hope I don't have to cut in the block or get rid of AC for this monster.
Does this look like a good turbo? More pics are located at:
http://members.aol.com/vtecingthismotha
No cat? I planned on getting a high flow cat? You think I should get a testpipe? I don't want to be THAT loud! -
BTW: I paypal'd you $5.00 for donation AbaZ
Does this look like a good turbo? More pics are located at:
http://members.aol.com/vtecingthismotha
No cat? I planned on getting a high flow cat? You think I should get a testpipe? I don't want to be THAT loud! -
BTW: I paypal'd you $5.00 for donation AbaZ
01-12-2003, 03:49 PM
#10
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Join Date: Dec 2002
Posts: 13,991
Re:Low boost - 2.5" or 3" exhaust? (i searched)
thanks for the donation, appricate it! 
by "looks" you cannot tell if its a "good" turbo or not. I am sure it will work just fine, the one we have is a .70 compressor and .63 turbine, with a On center 4 bolt flange. It looks like that has a internal gate housing? with a 5 bolt exhaust flange.. hard to tell since you dont have any pics of that side.
Seriously, it will not be that loud without a cat, just use a resonator inline, and a straight through muffler, 2.5 and you will be very satisfied. If you dont like it, then you can put a cat on it.. But it will sacrifice performance.
Jeff
by "looks" you cannot tell if its a "good" turbo or not. I am sure it will work just fine, the one we have is a .70 compressor and .63 turbine, with a On center 4 bolt flange. It looks like that has a internal gate housing? with a 5 bolt exhaust flange.. hard to tell since you dont have any pics of that side.
Seriously, it will not be that loud without a cat, just use a resonator inline, and a straight through muffler, 2.5 and you will be very satisfied. If you dont like it, then you can put a cat on it.. But it will sacrifice performance.
Jeff
