FASTER, 800's with accelerator pumps or without!

[Diggler4444af]

I have a 95 spi580 im done with trying to make fast. If anyone has 580 performance suggestions im open. Im giving in and going out to pick up a 96 xp. I noticed they did not put accelerator pumps on the 96's b or 97 spx but they did put it on the 98 and 99spx also the 97 xp. Im just wondering what is better or maybe some opinions ok thanks
Dan
ps what are the mikuni 40i carbs. whats the i mean, and is that an accelerator pump on it?

 

[popasodatastie]

Give it a Wirl

well i have rode a 2008 seadoo rxp with the 215 and i'll tell you i liked it but when it comes to takeoff with my 96 Xp its acceleration and crusin to me seems about in the same ranking i mean a little bit slower but it goes. I have the 787 Rotax and i would say go out and get one step up from the 580 get yourself the 787 and try to hang on! :cheers:

 

[Chester]

http://www.seadooforum.com/showthread.php?t=13833

Chester

 

[PWCdoc]

The accelerator pump is not actually anything that will increase, or decrease, performance. The accelerator pump is merely there to smooth out the transition from the low speed to the high speed circuit so that you get a more fluid feeling when accelerating.

It's also not intended to be there as a primer either but it can assist in that respect only until the fuel is depleted from the carbs as the carbs must be pumping in order to replenish the fuel for this circuit to be useful. Also, if you tend to feather your throttle you can actually flood your motor.

Having said all of that, I prefer non pumper carbs myself.

 

[seadoosnipe]

Arguments on both sides?

You might get arguments on both sides of the coin when it comes to the accelerator pumps.

If it were up to me, I would want accelerator pumpless carbs. It's just another sub-system to take care of and when you got to replace it, like I said, $200 bucks for a 1" square diaphragm...........:ack:

The idea here is the design. The accelerator pump design is set up that when you open the throttle, it distributes a quick burst of fuel into the manifold for combustion, which happens fairly quick. This is not used to speed you up any faster, not noticeable anyway. It's a part of the carbs design to start the manifold vacuum so that once the accelerator has been used, the engine's vacuum in the manifold has already been established and the carbs venturi is now working to distribute fuel into the throat, which is usually when it's in transition, both the pilot and main jets are supplying fuel.

On the other hand, the acceleratorless carbs design is set up so that as the engine is idling, one of the two orifices (one on each side of the throttle plate) is creating the vacuum from the beginning, sucking in fuel for working the carb from idle, into transition to WOT on the Main jet.

So, though the Mikuni does have two different set ups, one is not faster than the other.

As for how you can decide which Mikuni fits your Rotax, it's set up by horsepower. If your motors horsepower is up to 80 h.p, chances are, you have the SBN 44, up to 90 h.p, you'll see the SBN 46 and when you get into the 90 hp and larger, you get into the dual carbs 38's, 44's, and 48's. Modded class racers will use the Dual 44's/46's.

Bottom line, just because you have an accelerator pump does not make your carb faster. It will actually cause you to have more to maintain.........:cheers: