Throttle Body Question

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Oct 20, 2008 | 06:15 PM

maineultraclassic

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From: Biddeford, Maine

Throttle Body Question

I've been debating going with a larger throttle body for my build, but I also don't want to go too big and lose power.

I could have my stock 44mm bored out to 46.5mm.

Or I could go with a HPI 48mm or a HPI 51mm.

What is the thoughts on which size TB would give me the best gains with my build?

Doherty PowerPack Air Cleaner with Powervents vented to open air
Daytona Twin-Tec TCFI-WEGO IID Auto-Tune EFI System
D&D FatCat 2-1 Exhaust with Quiet Baffle
SE 95" 1550 Flattop Pistons(valve reliefs opened up)
Woods TW-6G Cams
SE EZ Install Adjustable Pushrods
SE Clutch Spring
SE Triple Platinum Sparkplugs
HD Premium Oil Cooler
Big Boyz Heads with compression releases
1.9" Kibblewhite Intake Valves, stock exhaust valves
78cc Chambers = 10-1 CR with 0 deck height
195 CCP F & R
Cometic Top-End gasket kit with .030 head gasket
Gaterman Products Lifters
Baisley Spring

Thanks for any thoughts or ideas.

Steve

Oct 20, 2008 | 06:31 PM

SuperAhcmed

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Quote:

Originally Posted by maineultraclassic

Hi Steve, looking over your build, Im going to have to say your probably better off with your stock FI TB. Your on a bagger and your cams are geared for low to midrange power. You want to keep your air velocity up. Increasing your TB will gain you some top end HP, but at lower rpms, you may lose a bit of air velocity with too large of a diameter in the tb, and I dont think your ride warrents that. If you were to go a bit bigger I would not go anything larger than the 48mm TB. I run a dual runner 50mm TB on my 97" ride, but I let her rip well over 6000k on a lightened softail.

So if this helps give you some insight..........

Oct 20, 2008 | 06:34 PM

maineultraclassic

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From: Biddeford, Maine

That's exactly what I was thinking................not to go too big, but at the sametime I do think that some increase would help things out, maybe.

A HPI 48mm would be the biggest I would go if buying a different TB.

Or I could send mine out this winter and get it bored out to the 46.5 that seems to be popular from Hillside.

I do like my low-end torque............and don't really need top-end HP.

Steve

Oct 20, 2008 | 06:39 PM

SuperAhcmed

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Quote:

Originally Posted by maineultraclassic

Yep, then I think your dialed in well with knowing your ride. Im sure either the bore out option or the HPI unit will do the trick. Since I think that having your stock TB bored out would be a cheaper alternative, I would go that route FIRST. 2.5mm is actually a decent bore increase. IMO better to go a little less than a little more in your case.

Oct 20, 2008 | 07:07 PM

chad peterson

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Good explanation! On my first 95" build I ran the SE 50mm tb, and made decsent power, but could never figure out why the bottom was so flat, so I tried some woods 400 cams, and it helped but still didn't seem right compared to most other builds. So I put my stock throttle body back on and at 2000rpm to 2500rpm range it picked up 10 pounds of torque (much more ridable), and I only lost 2 peak hp (who cares)! Plus your build is set up for bottom end torque, and it's a bagger! I agree that it's a bad a$$ build the way it is!

Oct 20, 2008 | 08:07 PM

maineultraclassic

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From: Biddeford, Maine

Another option is the Dakota Kid 48mm boring of the stock TB.

But again, I don't want to mess up a good thing. The bike is very strong now and has a very flat torque curve from 2500-5500, with the HP peaking at 6000.

I guess I just have always wondered that since the '06 bikes have a 46mm, then an increase would benefit my bike.

Steve