3" vs 2.5" crossover pipes....LETS LAY IT TO REST!!
10-19-2011, 06:31 PM
#21
You have a have the Brute speed/APP cam correct.
There is a big difference in the design of a cam for a supercharged motor to a turbo motor.
heck there is a difference between a centi and PD style blower cam specs.
The cam you have was originally designed as a blower cam not a turbo cam. It does ok as a turbo cam but it is not the most desireable cam for a turbo car.
Cam selection can make a difference in spooling that turbo
There is a big difference in the design of a cam for a supercharged motor to a turbo motor.
heck there is a difference between a centi and PD style blower cam specs.
The cam you have was originally designed as a blower cam not a turbo cam. It does ok as a turbo cam but it is not the most desireable cam for a turbo car.
Cam selection can make a difference in spooling that turbo
10-19-2011, 09:22 PM
#24
If 800hp is what you are looking at making then the 2.5 is good. It doesn't belong on a race car making 1200 plus though. Look at what you would want at that hp n/a and the go from there. I have never had trouble making boost from a big cross over or headers.
10-19-2011, 09:24 PM
#25
You have a have the Brute speed/APP cam correct.
There is a big difference in the design of a cam for a supercharged motor to a turbo motor.
heck there is a difference between a centi and PD style blower cam specs.
The cam you have was originally designed as a blower cam not a turbo cam. It does ok as a turbo cam but it is not the most desireable cam for a turbo car.
Cam selection can make a difference in spooling that turbo
There is a big difference in the design of a cam for a supercharged motor to a turbo motor.
heck there is a difference between a centi and PD style blower cam specs.
The cam you have was originally designed as a blower cam not a turbo cam. It does ok as a turbo cam but it is not the most desireable cam for a turbo car.
Cam selection can make a difference in spooling that turbo
10-19-2011, 09:49 PM
#28
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Look at VA Speed's shelf turbo grinds. There are many different theories on camshaft specs for turbo engines but VA speeds look nothing like yours.
10-20-2011, 05:16 AM
#34
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What's the area in sq inches of the inlet of a T6 turbine housing, I bet it's smaller than even a pair on twin 2.5in pipes. On my 355ci engine I use 2in ID pipes feeding my T4 GTX4202 and they are even a fair amount larger in area than the flange opening.
I cannot see the point of letting the exhaust gas to expend into a big pipe then having to compress it up even more than required when it hits the turbine inlet. The most important thing when you run small crossovers etc is to make the merge from the primary pipes into the cross over as smooth as possible.
I cannot see the point of letting the exhaust gas to expend into a big pipe then having to compress it up even more than required when it hits the turbine inlet. The most important thing when you run small crossovers etc is to make the merge from the primary pipes into the cross over as smooth as possible.
10-20-2011, 05:56 AM
#35
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What's the area in sq inches of the inlet of a T6 turbine housing, I bet it's smaller than even a pair on twin 2.5in pipes. On my 355ci engine I use 2in ID pipes feeding my T4 GTX4202 and they are even a fair amount larger in area than the flange opening.
I cannot see the point of letting the exhaust gas to expend into a big pipe then having to compress it up even more than required when it hits the turbine inlet. The most important thing when you run small crossovers etc is to make the merge from the primary pipes into the cross over as smooth as possible.
I cannot see the point of letting the exhaust gas to expend into a big pipe then having to compress it up even more than required when it hits the turbine inlet. The most important thing when you run small crossovers etc is to make the merge from the primary pipes into the cross over as smooth as possible.
Last edited by Fireball; 10-20-2011 at 06:01 AM.
10-20-2011, 06:00 AM
#36
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I dont get the Spooling issues. everyone wants to blame the Tube size. You need to be looking at your Tune among other aspects of your Builds. Hell we have spooled 101mm Large Frame turbos to 12-14lbs with 310ci SBF engines in under 4-5 seconds that dont breath nearly as well as the LS1 Platform's.
1. on the starting line
2. After transbrake is release (how fast can the boost come in)
Its all a balancing act. you can improve spooling with small A/R turbine housings which will add considerable backpressure up top. Can also loosen converter to get more rpm but will typically have more slip up top as well.
10-20-2011, 06:42 AM
#39
Yeah, im an idiot 
I asked Phil his thoughts on my cross over before i bought my pipes, after seeing TracyRRs results after taking his advice, i figured, what the hell.
Plus, i saw someone post one time about the "coincidence that at t4 flange fits almost perfectly against a squared 3" pipe" And said, "****, that makes sense"
SO.. with that said, you a guys are my reason for 2.25"
I asked Phil his thoughts on my cross over before i bought my pipes, after seeing TracyRRs results after taking his advice, i figured, what the hell.
Plus, i saw someone post one time about the "coincidence that at t4 flange fits almost perfectly against a squared 3" pipe" And said, "****, that makes sense"
SO.. with that said, you a guys are my reason for 2.25"
10-20-2011, 07:57 AM
#40
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So it wouldn't be a big deal using 2" for max of 1000hp should be ok right? I'm going to try to step up to a 2.5" if i can make it fit. Its really tight up front of a typhoon with a lq4. The 1000hp is just hopes and dreams as of right now, nothing wrong with planing for the future.