Flow calculation for some LSJ parts.

[jmc007]

Hi ! Here are my flow calculation for some LSJ engine parts :

ADDED COMMENT : These flow numbers are calculated at ambiant air temperature AND pressure.

Stock Throttle Body (67 mm) : 625 CFM.
EDITED : Stock Head : One intake port : 250 CFM @ stock 0,395" valve lift. One exhaust port : 145 CFM @ stock 0,395" valve lift. Stock head is said by GM to be efficient up to 275 WHP; it is clearly possible to make more WHP than that, but in a unefficient way (several HP losses caused by heat and restriction).
Stock Exhaust manifold ("Header") : 425 CFM.
Stock Downipe (DP) with cat : Plus or minus 370 CFM or less.
Stock Cat-back Exhaust (2,5" inlet to 2,25" outlet with stock muffler) : 300 CFM.

Now here are some replacement parts :

GMPP Exhaust manifold ("Header") : (30 more CFM than stock) : 455 CFM.
Shorty or long tube Header with 1,75" primaries and 2,5" outlet : at least 500 CFM.
Shorty or long tube Header with 1,75" primaries and 3" outlet : at least 725 CFM.
Shorty header with 1,5" primaries and 2" outlet : Waay not enough, who cares LOL.

Stock DP w/o cat : 425 CFM.
2,5" DP with VERY HIGH FLOW cat : plus or minus 450 CFM.
2,5" DP w/o cat : 500 CFM.
2,75" DP with VERY HIGH FLOW cat : plus or minus 475 CFM.
2,75" DP w/o cat : 600 CFM.
3" DP with VERY HIGH FLOW cat : plus or minus 500 CFM.
3" DP w/o cat : 725 CFM.

Stock catback with only the rear muffler replaced (the last portion is still in 2,25" tubing) : 350 CFM.
Stock catback with last portion replaced for 2,5" tubing and straight through muffler : 450 CFM.
2,5" catback : From 450 to 500 CFM (must be a straight through muffler).
2,75" catback : From 550 to 600 CFM (must be a straight through muffler).
3" catback : From 650 to 725 CFM (must be a straight through muffler).

Hope this can help ...

Regards )

[handyjoe]

How was this measured/calculated?

[socalsilverRL]

what? a LSJ head outflows a LS6 head be 120CFM?

did you measure that flow with or without the valves in there? and at what mm of lift?

[AlphaJaguar5]

Actually the LS6 sucks at making power compared to us.

An LS1 has a BMEP of 11.27 while we have a 17.05. Like it has been stated before though, the EVO engine rocks cranking out a 24.64 BMEP.

[socalsilverRL]

^yea, i think he calculated flow without the valves in there... DJT dan had the calculation somewhere around 380 with 1mm lift...iirc.

[Shabodah]

His numbers look to be total. You guys are thinking per cylinder. The LSJ does NOT outflow the LS6 head, but it's 4 cylinders would outflow 1 of the LS6's. lol.

[AlphaJaguar5]

Originally Posted by Shabodah

His numbers look to be total. You guys are thinking per cylinder.

I am...asdfhahahae

[jmc007]

Post #1 Edited (Head Info).

[hammers]

nice post deff help alot of people

[fullthrottle]

Why isnt this a sticky?