The stock early TB is 44mm at the butterfly but has a venturi after it (40mm) and before the manifold. It flows same or slightly better than the later stock later TB. If you remove the venturi you can pick up a a bit of flow. The later TB is 46mm but has a slight larger plenum in the manifold area. Cleaning up the steps at the ports helps with flow but it still doesn't match the early TB with the venturi removed. Early TB gets more velocity if that is what you want. Look at the last 3.

 

ok, i scored all the parts, and got a spare early throttle body and can see what you mean about the venturi behind the throttle plate. got adapters for the injectors and a new harness for the t/p sensor. my big question now, is that for my build, 04, 95 inch, 10.5-a comp, tw54 cams and stage1/streetport heads, (06 later style)which is most likely to serve me better? the higher voelocity of the re-worked old t/b, or the larger throttle bore and plenum of the newer style throttle body. the bike has the old W/B Epipe and PV to tune with, but i'm trying to get some opinions before i set myself up for a)more dyno time and attempting to mod the early t/b. thoughts?
ps bike is already over 100 hp and tq, i really just cant leave well enough alone sometimes.
thanks
marco

 

One thing i can tell you from running an early TB with 06 program is that I had to adjust cranking fuel and IAC warmup steps. Also don’t forget to adjust your injector flow rates.

 

the bike is an 04 and as far as I can tell the logic for the tune is for the 04 years, i understand what you mean on the injector flow rate(my t/b does have the 25dg injectors), what did you have to do with the cranking fuel and warm up steps, as i'm already having issues with that, with the stock throttle body,,starts up ok, runs for a second and stalls, doesn;t hold a stable warm up routine.
m

 

iac warm up steps too high = excessive rpm flare on startup

Iac steps too low = hard start or struggling start or start and die.

cranking fuel too low can isually be diagnosed by keying on and allowing prime pulse, keying off long enough that another prime pulse will be delivered at a second key on. After second keynon, if if pops right off thats a sign to increase cranking fuel. May also have extended cranking if its too low.

Excessive cranking fuel may result in kickback and hard start / no start or backfire.

I used efi super race tuner to look up those values in a map for the year of the throttle body i used with the best matching parts and pasted into new map. Adjusted from there.

 

I really don't know which TB will be better. Short of testing buth on the dyno, about the only thing that can be done is to attach the TB to a head and see how it flows. I would expect that the one that flows the best will make the most HP and the one which the higher velocity (CFM/port-valve area) would provide the better/wider TQ curve. Again it's just a guess and can easily be different based on different components used.

 

I agree with you Max, i was just hoping that someone else had done this to report on it and maybe save me some brain and dyno work. Will report after i do the job and get it on the dyno.
I really helps when you own one!!!
m

 

So, what were the results? I would really love to hear this. I already have an 06 TB sitting here.. Doing a marelli to delphi swap.. was going to go full 2006 up.. had trouble getting the 06 harness, so i ended up landing the 04a harness. I will have toi repin the IAC and Fuel injectors.;

Would love to hear the results? In the auto world.. a few MM makes a huge difference.