| Author | Message | ||
     Medic_2512 |
Has anyone tried a larger throttle body on their XB12? I was think the stock 49mm has to be a bottle neck? In comparison my 250cc dirtbike has a 40mm TB and alot of the Rice Rockets have 4 TB`s that are 44 to 42mm. | ||
| Alex |
With stock heads the 49mm throttle body will be definitely no bottle neck. I say it can easily take You up to 115 to 120 rwhp when You have the necessary engine mods. Best regards Alex | ||
| Buelldyno_guy |
Yes we run a 52mm on our race 1210cc +1mm XB Race Bike, but it has stage 3 heads and RS 643 cams. We spin it to 8200 RPM. ... Terry | ||
| Alex |
To feed a 1200ccm engine at 8200rpm You will need about 155 to 160 cfm through the complete intake tract. This is not a major problem with a 49mm throttle plate. Going bigger wouldn´t hurt with an injection system but I´m sure 49mm would be ok as well. Best regards Alex | ||
| Buelldyno_guy |
I was answering the question that was asked. ... Debates concerning Stage 3 Head flow rates and 1210cc engines making 118 RWHP need to go the the KV. … But I will say that Buell's Henry Duga and our head builder's opinion the 49mm TB is acting as a restrictor plate on racing engines. That's why the 1350cc Hal’s bike has twin 60's. ... Let’s discuss it in the KV. ... Terry | ||
| Medic_2512 |
Thanks for the info. Do you even know where i can get a larger throttle body for my XB? The reason i`m interested is that i`m planning to make it an 88" before the summer. | ||
| Glitch |
You may want to contact Revolution Performance or Cycle Rama, if I'm not mistaken they can bore the one you've got. | ||
| Martin |
or just fit two, like I did | ||
| Medic_2512 |
Martin, tells us the details of how you put two TB`s on! | ||
| Diablobrian |
I second Medic_2512, with pics if possible Martin! | ||
| No_rice |
i'm all up for that to if you really did! hmmmmm... dual throttle bodies... so that would mean one nitrous fogger per throttle body..... hmmm so that would mean... hmmm... OMG!!!! GO BABY GO!!!! | ||
| Alex |
Terry, I was answering the question, too, as the second part of it was if a 49mm throttle body would be a bottleneck for a XB12. So no need to discuss flow or hp numbers in the KV  Best regards Alex | ||
| Martin |
This is the only picture I have to hand, of the manifold  | ||
| Diablobrian |
Is that TB off of a current generation IL4?. Nice work BTW! | ||
| Thomas_lindemann |
why not put the throttle body up to the mouth of the port? IMO the stock buell set up isnt much better than a carb because of the injector location and that stupid mainifold. Ive been toying with the idea of using two throttle bodies off a hayabusa would only really have to figure out the throttle linkage (Message edited by thomas_lindemann on January 21, 2006) | ||
| No_rice |
how are you going to cram it inbetween the framerails if you try to hook it up closer to the motor? and get a good supply of air to both of them? runner length has a fair amount to do with how a motor responds too so i would wonder how well either one would work. i know hals has a duel setup but there has to be ALOT of dyno time into that kind of a setup also. | ||
| Thomas_lindemann |
I have the motor out of my bike right now so I cant tell you about demensions but dont think it would be any problem with putting them right up against the mouth of the port.They are not more than about three inches in length and the injector mounts in them and would squirt directly in the port. Runner length is not a big deal either as you could play with that. It will probably be a month before motor goes back in it I will do some more engineering then but dont think its a big deal | ||
| No_rice |
never know. i havent had the motors out of mine yet so i am just going by what i can see through the cracks, lol. i'd be interested in what you find, even if its just for more knowledge. | ||
| Martin |
You can buy plate injectors that are less than an inch thick but there wouldn't be an advantage to having them that close as the air still has to turn a corner. The race bikes have welded-up and downdrafted heads to try and address that very problem. As a result of the twisted nature of the inlet runners I think that they have had to make one trumpet longer than the other to bring runner lengths back more equal. The tight bend I have is not ideal for flow but is no worse than the standard. I have ended-up with a total runner length identical to standard. The T/B is a Jenvey DNCF style twin 42mm chosen for packaging ease (The bores are close together) and the availability of a trumpet. On a standard 9 I would go for a 38/40 if I did it again. The standard injector fires at the back of the valve, which helps with mixing at low revs but is slightly compromised at the top end of the rev range (but not much). The more you rev a motor, the further away the injector needs to be. Hence the twin injectors seen on some IL4s and the 'outside the manifold' ones on F1 cars. Looking at the standard heads in a XB frame I would still be tempted to try a slight updraft setup that comes-out under the frame. You could maybe use a tube-frame buell manifold and adapt it. | ||
| Thunderheart69 |
A plenum chamber thats about 20% larger than the displacement of the engine is a good place to start according to turbo and drag builders who design sheetmetal manifolds for fuel injection. I believe hogan's and accell/lightenfelter had these issues when designing airflow reqs. runner dia. and length as well as shape control volumes and velocities at different rpms and actual vehical speeds through ambient air at speed. Hope this gives a better place to research from. |
