question on carb spacers.... : V-Twin Forum: Harley Davidson Forums

Mother · 10-24-2009, 05:46 PM

what affect/effect(I are a biker) would a 1" carb spacer have on the HP and TQ curves? Throttle response? is a 1" spacer worth running? I have seen guys runnin 2", but that sets the carb/ac too far out for a scoot I ride everyday.
Thanks guys

HDMD88 · 10-25-2009, 07:43 AM

Quote:

Originally Posted by Mother

what affect/effect(I are a biker) would a 1" carb spacer have on the HP and TQ curves? Throttle response? is a 1" spacer worth running? I have seen guys runnin 2", but that sets the carb/ac too far out for a scoot I ride everyday.
Thanks guys

Just adding a spacer to the intake track doesn't mean you are going to gain hp/tq. There are three intake track tuning formulas that are used to find the correct length for the 2nd, 3rd, or 4th intake pulse to aid in cylinder fill. This pulse wave is effected by the cam used along with other factors so there is no general statment of what size spacer to use. Usually these mods are done on race motors to get evey last hp/tq squeezed out of the build. I believe we have discussed this topic in depth several times here on the forum....if you do a search on intake track tuning I'm sure you will have a good read.
Doc

Hillside · 10-25-2009, 11:16 AM

As Doc has said, plenum volume is dictated by the cam.
When working in that area, even 1/2" increments can spell out some nice things, but dyno tuning is the way it will be witnessed.

Scott

SLPER · 10-25-2009, 11:42 AM

Quote:

Originally Posted by Hillside

As Doc has said, plenum volume is dictated by the cam.
When working in that area, even 1/2" increments can spell out some nice things, but dyno tuning is the way it will be witnessed.

Scott

Scott,
Do you have any examples of cam, TB, and cubic inches that a 1/2" spacer was in order?

Cheers!

route66paul · 10-25-2009, 11:58 AM

This is an area of fine tuning and will just make the higher rpms better(maybe). For the street - I doubt you would be doing any good.

pwmorris · 10-25-2009, 01:01 PM

I dont think you are going to see any big difference on the street other than maybe cooler fuel by using a PHENOLIC INTAKE SPACER
that can reduce heat transfer-cooler fuel gives you more horsepower.

SLPER · 10-25-2009, 07:28 PM

Quote:

Originally Posted by pwmorris

I dont think you are going to see any big difference on the street other than maybe cooler fuel by using a PHENOLIC INTAKE SPACER
that can reduce heat transfer-cooler fuel gives you more horsepower.

Have no evidence yet, but I ceramic coated my HP Inc. TB in hopes of a cooler charge??