[Diy_efi] Importance of TPS with lightweight cars

[William Shurvinton]

----- Original Message -----
From: "Adam Wade" <espresso_doppio at yahoo.com>
>
> Incidentally, I'd really like to discuss your
> experiences with the MS and the 'blade off-list, as I
> am writing a series of books on motorcycle fuel
> injection.

No Probs. The first full tune is not complete, but I am building up a pile
of MS for other BECs as soon as I have moved house, so this summer should
see a number running.
>
> I believe they go hand-in-hand.  If the air velocity
> doesn't drop, there's no need for an enirchening setup
> for acceleration; you'll get as good atomization as
> with steady-state running, and will require an almost
> identical mixture

Agreed, but we are approaching from different angles I think. My fault for
use of the word 'acceleration' in my first post. If you are not accelerating
(TPSdot=0, VSSdot=0) then you can tune lean of stoich. If you open up the
throttle then VSSdot becomes positive and you need to go richer to get the
wanted kick in the back. The dyno would tune for best power, so you wouldn't
necessarily have this transition to worry about. Also in a port injection
setup the accel shot is less related to atomisation changes than with a carb
or TBI setup.

> If a vehicle's drivetrain is responsive enough, and
> mass is low enough, then the intake velocity won't
> drop much upon throttle opening, and an acceleration
> enrichment map won't be necessary.

Still reckon this is more due to throttled volume than mass, but need to
think some more.

<Snip from other mail>

>> Given how much more sensitive to bog a low inertia
>> engine is there must be some sort of TPSdot
>> fitted.

>I disagree.  I think low-inertia small engines are
>LESS sensitive to bog, because they can spool up much
>more quickly, and don't let the IA velocity drop as
>much

Might be terminology, and I only have experience with 1 engine and that was
in a car rather than a bike, but comparing tuning that with my rotary, if
the tune was lean the rotary just died on throttle opening, no drama. If the
blade was too lean it bucked like a bronco, and in fact bent the engine
mounts on one occasion. That may not be 'bog' in your dictionary but a
higher mass flywheel would have masked this.

Bill


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