Oneiros

This might start another controversy but here goes

Extending the AP arm will reduce low end acceleration, because the pump has a longer stroke it will shoot fuel at a lower rate as the throttle opens, resulting in a leaner acceleration mixture - in my experience it was quite noticeable on light throttle. However the fuel shot will last longer, meaning it covers the point where the usual mech secondaries mod starts opening the secondary throttles.

No drawbacks with enlarging the AP volume though (e.g. with gaskets), apart from extra fuel consumption.

Few pics of my latest strip.

Sterling

Uhmmm, OK. Not sure why you're not making the connection between increasing the AP volume and increasing the shot duration. They're done together on the Sterling Nikki for a reason.

Oneiros

Ok, from what I understand, the only worthwhile way of increasing the AP volume is by letting the diaphragm extend to its full potential. There's no point increasing the amount of fuel that can sit in the AP circuit because it's only going to displace as much as the diaphragm can move.

If I am right in the above, then increasing the AP volume by maxing out the stroke of the diaphragm won't increase the RATE of fuel it squirts as the throttle opens. It will just allow for a longer stroke, and that's where the extra displacement / volume comes from. Making the AP diaphragm stroke even longer in time, by extending the AP lever, is going to reduce the RATE of fuel being squirted (against rate of throttle opening), resulting in a leaner acceleration mixture.

That is why I would increase the AP "volume" by allowing the diaphragm to move as far as it can, but would not extend the AP lever as this will lean the acceleration mixture. If you have mech secondaries opening late then yes it makes sense to extend the AP stroke to cover this, however mine open so early (1/4 throttle) that I don't need a longer AP stroke and prefer the richer bottom end pull.

Just throwing my ideas out there.

blwfly

iTrader: (4)

nice carb^^

Sterling

Are you asking me, or tellingme?
It feels like you're telling me, in which case I should just say, "Well, OK then. You know what's best. Good luck. ", and leave it at that. lol

Oneiros

Lol neither like I said just throwing my ideas out there, i may be wrong of course.. And yeah i may be crazy but I'm sure not crazy enough to try and tell you how the Nikki AP works!

Dadsmazda

iTrader: (2)

I've just installed a rebuilt carb on my 1980. My original carb had the part (power soledoid?) you're referring to, which is also the part that has the red arrow pointing to it in an earlier post. My rebuilt carb, however, has the hole plugged for that part. The car is running great without having this part hooked up, but it was there for a reason originally. Do I need this gizmo? Or am I OK running without it?

Any info or thought are greatly appreciated.

Thanks.

Oneiros

That would be the power valve solenoid. Unlike most other carbies, the few Nikkis that came with a power valve had it electronically controlled (via that solenoid) for emissions purposes. So like most of the other emissions stuff you can remove it.

Dadsmazda

iTrader: (2)

Thanks for the quick reply! You're info is very helpful. I really appreciate it.