Ported Throttlebody

[Backdrafter88]

Anyone have it/done it?

I've been googling and searching this site for days now on information on this and I can't seem to find what info I am looking for. I am planning on getting my heads ported sometime this year, most likely the Hammer Perf. "Smash" or the NRHS Stage II port job done. I wanted to go bigger on the throttle body/intake as well. I have read that it can go up to 51mm from the stock 49mm. Future plans also involve a set of cams, or an 88 inch big bore kit.

Looking for all of the info I can find on this, anyone have any useful info?

 

[mrNICEGUY]

Are you going to change to a bigger butterfly?
I think you are not getting any performance gain if you are going to stick with a stock size butterfly.

 

[Backdrafter88]

Yes i will increasing the size of the butterfly as well, also more than likely going to have to increase the inner diameter of the velocity stack as well...perhaps a trick piece of aluminum.

 

[Internet Annoyance]

depends on what you think you need to accomplish, Bigger is not always better, in fact often times Bigger will make you slower and just create problems. You MAY already have an excellent game plan and a desired step by step way of getting there, but it isnt clear from your post. What are you looking to accomplish?
For example,, big ports, big valves and ported intakes just KILL low end performance, torque and power. It only really works on the top end when flow needs to be unobstructed and massive air quantitys are needed. But the problem is that these motors just plain fall on their faces past 6000 rpm, Now a ducati desmo motor or an asian bike that spins up past 10,000 rpm is a different story. I have a motor here with intake porting, head work,Big bore kit, cams and dyno sheets, It sure does cost a LOT OF MONEY. Money you will never recoup if you want to sell it, I know of 2 other motors with this work done, and your marketing is very limited for resale, keep that in mind if you go down this path.

 

[s0dhi]

Along these lines, how well are the ports matched on our engines? T-Body to manifold to heads to exhaust?

 

[mrNICEGUY]

If I remember right, intake ports will require some welding before porting.

 

[Backdrafter88]

So perhaps the throttle body work isn't necessary? My bike runs good and hard up to the limiter due to the race kit on it (EBR ECU, factory race exhaust, K&N) I'd like to touch up the heads so it breaths better, pulls a little harder up to the limiter, and do this now so that when the time comes for 88" kit and cams I won't be doing it all at once. For now a few trips to the drag strip for some bracket racing, while maintaining DD status. Don't want to turn it into a pain in the ass to ride, I want to keep it reliable and yet give it some more power to help ensure most of the jap bikes I run into stay in their place

 

[EricZ]

With what you just said, don't worry with the throttle body until you have all the other work done. The stock XB12 body is more than enough even for a high powered XB engine. I have near 200hp running through my stock sized XB throttle body.

 

[Internet Annoyance]

Tuning and performance mods on ANY motor are a package, not a list of single components, Read up on forums like the XL or Sportster forums on "Stage tuning" stage one for example is Air cleaner, jetting and exhaust, easy to do, inexpensive relative to the gains. Stage 2 might be upgrading a 883 to a 1200cc, again, a huge performance increase for very little expense, but once you get to stage 3 and 4 the costs are high and the rewards much less tangible, There is no lack of writeups on this on the sportster forums and guys back it up with Dyno printouts of what they used, ahd the results they got. Buzzellis Sportster performance book might also be a good place to start as well, he touches on Buells a little bit.
Porting your EFI intake by itself would be a mistake, and im 100% certain you would lose power and rideability.
read up on the how all this works together. Keep in mind, these Buells, especially the XBs are already damn close to as good as it gets for that motor design,
But smaller being better is hard to sell, but let me make a comparison for you,,, I have built a lot of hot rod cars, and spent a LOT of money building crazy motors that really were a pain in the ass to drive and maintain, 350 chevys with stroker kits, alloy heads with big valves, big carbs, big intakes, even for a while ran a tunnel ram with dual double pumpers, Looked cool as hell on my 63 nova SS, but ran like shit, went to smaller carbs, and vac secondarys and went faster, got rid of the tunnel ram and back to a dual plane edelbrock and went even faster,
while rebuilding that motor, i stuck back in the stock 283, power pack heads (Small ports-small valves) the stock 2 barrell intake and rochester 2 barrell carb, and you know what? on the street that motor was way faster, and more fun, plus decent gas mileage, I learned the expensive way that small ports equals velocity and off the line and in real street driving, thats where its at.,,,Torque is what pushes your eyeballs into the back of your skull, HP you cannot feel, its only an abstract number on a dyno print out.

 

[Backdrafter88]

So in essence you're all saying that I'd be wasting time and money on the throttle body even with a 88" kit and ported heads, because the gain is negligible at that point? That's all I wanted to know. Gotta do my homework before I spend the money.

 

[mrNICEGUY]

My findings have show that there could be benefits to increase throttle bodys size, or even making dual throttle bodys... However there could be some driveability conserns at low speeds/cruise..

http://www.lxforums.com/board/showthread.php/194536-Throttle-Body-Selection-with-a-Pocket-Calculator

Throttle body sizes on Nitrous, supercharged and turbocharged vehicles:
http://www.boosttown.com/engine/throttle_body.php

And a bit more info for throttle body sizes(at section "Throttle Bodies" under the "injectors and fuel"):
http://www.megamanual.com/v22manual/minj.htm

Best calculator that I've ever found. And it suggest that stock 49mm would be optimal for stock/lightly modified Buells:
http://dairally.net/daihard/chas/MiscCalculators/DaiThrottle.htm

 

[Backdrafter88]

Thanks for the info mrNICEGUY, I'm going to take a few days and read through these links.