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EFI69Cam
10-19-2006, 05:36 PM
Someone told me that EFI TBs are rated at 28" and carbs are rated at something lower than that.

I currently have a 1000cfm TB. This seems small for a 540" engine. But then again the RJ 502 makes 500hp through a 600something cfm TB.

Is a 1600CFM TB going to be too big for a 600HP 540?

DeltaT
10-20-2006, 09:05 AM
No, because it is just an air door. CFM ratings for carbs are more important because the carb needs crisp signals from the motor to run right. With efi it's less important because your fuel is injected much clower to the valve and no signal is needed for the air door to work correctly.

Jim

Fuelie Fan
10-20-2006, 09:50 AM
It still affects driveability in the respect that its harder to modulate a 1600 cfm throttle body than an 1000cfm. Some people like this: it leads to lots of burnouts. I personally try not to run excessively oversized. If your current throttle body isn't a restriction, then a bigger one won't do anything for you. Check your efi logs and see if MAP starts falling off near redline. If not, you don't need to upgrade.

pretty sure all 4 bbls, whether it be carb or efi, are rated at 1.5 inHg.

Blown353
10-20-2006, 11:55 AM
It still affects driveability in the respect that its harder to modulate a 1600 cfm throttle body than an 1000cfm.

Words of wisdom right there.

A TB that's too big, especially if it has been coupled with poor linkage geometry can lead to the throttle being more of an on-off switch in the lower load/rpm ranges which can be really annoying in traffic.

I'd stick with your current 1000cfm TB and check the manifold vacuum at WOT. It should be more than adequate for the job.

EFI69Cam
10-20-2006, 12:38 PM
I have not run the 540" engine with the 1000cfm TB yet.

I am debating switching to a 4bbl type intake from my current arizona speed tpi setup, along with a switch from the GMPP zz502 heads to AFR 315 rectangle ports.

I can buy the edelbrock stuff for less than ASM gets for their short runner rectangle port lower intake.