[Diy_efi] VTEC solenoid driving, dual throttle butterflies in individual throttle bodies

Adam Wade espresso_doppio
Wed Sep 21 17:30:18 UTC 2005


--- glogovacs at yahoo.co.uk wrote:

> Now, there is a question how to control VTEC
> solenoid.

Wouldn't it be easier to get an IAC solenoid from the
donor vehicle?  The system you are using was probably
meant for some particular vehicle...  If it was a
generic racing box, you could look at other
Weber/Marelli systems for V-twins, such as Ducati, and
early Harley-Davidson EFI (there are a number of
variants from different manufacturers, so make sure
you get the right system!).

> On the intake side we are thinking of using Suzuki
> GSXR 1000 throttle bodies. A question that arises
> here is whether or not to use the model with dual
> butterflies, anyone having experience with this?

The dual butterflies are to keep the throttles from
opening too far too fast.  On a motorcycle, this can
cause a significant stumble, as well as too-quick
throttle response in some cases.  The secondary
throttles are to limit the speed at which the
throttled area is actually increased, and is driven
via a map using a secondary TPS and a stepper motor. 
It's unlikely you can drive this system properly from
a Weber/Marelli unit without modification, and then
you have to program the response of the secondary
butterflies.  I would tend to recommend against it.

A useful alternative may be to source early Yamaha R1
EFI throttle bodies.  Most had vacuum-operated CV
slides like bike carburetors, an elegant mechanical
solution to the same problem that the dual butterflies
control.  While dual butterflies can be better
tailored, and so are used more and more these days,
the hurdles one would have to jump to use them for a
completely different motor might not make for good
time management.  Assuming your hardware will support
it, it's a great option, but the development time for
tuning it might be the killer.

| Honda GL500 Interstate (Slug)    Kawasaki Zephyr 550 (Daphne) |
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|   The catastrophe in this case, of course, was that the sun   |
|     had come up again."                    -Kurt Vonnegut     |
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