thepest
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| posted on 17/7/08 at 04:35 PM |
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Bike TB's vs Webber side draught
Is there any performance gain if I switch to bike throttle bodies and fuel injection as opposed to side draught carburettors? (the engine is a x-flow
but the question is general for all engines)
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clairetoo
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| posted on 17/7/08 at 04:53 PM |
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When I changed from twin 40`s to GPZ100 throttle bodies and distrubuterless ignition , I gained 30 bhp...........with a massive boost in torque .
The fuel consumption and drivabilty were so much better as well 
No contest , IMHO
Its cuz I is blond , innit
Claire xx
Will weld for food......
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mookaloid
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| posted on 17/7/08 at 05:02 PM |
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I would say it depends, If you have an optimal setup with side draughts you may not see a gain in power if you change.
However I would agree that driveability, smoothness, better idling, better economy would be benefits in most if not all cases, with power increases in
a lot of cases.
Cheers
Mark
"That thing you're thinking - it wont be that."
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rusty nuts
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| posted on 17/7/08 at 05:10 PM |
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T/B s every time .
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mr henderson
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| posted on 17/7/08 at 05:21 PM |
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Carburettors require a venturi (narrowing of the inlet tract) to work, fuel injection does not. If everything else is equal FI will always win on that
one point
John
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BenB
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| posted on 17/7/08 at 05:39 PM |
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Throttle bodies every time. As already said they're not choked (so no restriction) and it's so much easier to set-up EFi than carbs.
There are only three real benefits to having twin Webers
1) they sound impressive when driving
2) they sound impressive for car related talk down the pub
3) they're 1960s technology that some people have a sense of nostalgia for...
Well set up carbs can be close in Bhp to similarly sized TBs but they'll likely quickly go out of tune quite quickly. Once mapped EFi is stable
(and fine tuning is easy).....
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CaptainJack
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| posted on 17/7/08 at 06:02 PM |
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Carbs Also Look great!
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rusty nuts
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| posted on 17/7/08 at 06:04 PM |
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quote:
Originally posted by CaptainJack
Carbs Also Look great!
But SO twentieth century!
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D Beddows
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| posted on 17/7/08 at 07:47 PM |
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quote:
When I changed from twin 40`s to GPZ100 throttle bodies and distrubuterless ignition , I gained 30 bhp...........with a massive boost in torque .
I have to say that your carbs must have been utterly f*cked if you got that dramatic an improvement!   'scuse the french and all that
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thepest
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| posted on 17/7/08 at 08:19 PM |
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Ok Guys TB's it is, are 42 mm kawasaki tb's sufficient for a 1700 xflow (84mm bore)? Could I keep the Fuel pressure regulator or would I
need to change? What type of pump would I need and where abouts would I start with injector size?
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mr henderson
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| posted on 17/7/08 at 08:37 PM |
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What power of motor bike did they come from (I don't know anything about bikes and don't want to learn) but if it was similar to what the
crossflow might achieve then that would be a good starting point.
What ECU are you going to use?
John
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MkIndy7
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| posted on 17/7/08 at 09:31 PM |
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I personally would go for some smaller TB's if possible probably from a 600cc bike.
We've got R1 Tb's on our pinto and the slightest of throttle and its off so setting the low speed cruise etc is dificult.
The Fuel pressure regulator should come with the TB's on the fuel rail.
We and a few others have a Vauxhall external stand alone type fuel pump.. others have gone for in-tank versions.
You will also need a fuel return line to the tank and either a baffled tank or a swirl pot and hi-low pressure pump setup (should the fuel be slopped
away from the pickup point Tb's die instantly whereas carbs still have a small store of fuel)
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clairetoo
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| posted on 17/7/08 at 09:51 PM |
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quote:
Originally posted by thepest
Ok Guys TB's it is, are 42 mm kawasaki tb's sufficient for a 1700 xflow (84mm bore)? Could I keep the Fuel pressure regulator or would I
need to change? What type of pump would I need and where abouts would I start with injector size?
42mm is way too big for a crossflow - I used 35mm and got 165bhp@8000 rpm.......
Its cuz I is blond , innit
Claire xx
Will weld for food......
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Jenko
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| posted on 18/7/08 at 09:31 AM |
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Assuming you are takling about converting to fuel injection, and not just going to bike carbs???????......
The Earlier GSXR600 (k1, K2) bodies are tapered from 40mm to 38mm on the inlet. They would be perfect........But you really do want to keep them as
small as possible. I use 38mm on my 2ltr CVH engine and they work really well....
If the carbs are set up correctly, the top end BHP will not be changed too much, but as previously mentioned, driveability, low down pull, and fuel
econ will be much improved.
You cannot use the old pressure reg, as Fuel injection runs at around 3 bar (45PSI), where as carbs run at 3-4psi - A very big difference.....
[Edited on 18/7/08 by Jenko]
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thepest
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| posted on 18/7/08 at 12:04 PM |
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Thanks Guys, I was thinking of using the Megasquirt, its locost and popular should I need support 
Any Idea as to what trumpets to use for TB's please?
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