Dude- where's my boost?

[kwb]

Low boost off trail- as expected on trail
Stage 1 MPI SC on 2006 Apex I bought with the SC already installed but I don't think it was completely dialed in.

I have added a boost gauge and am still waiting on air/fuel to show up but one thing had me concerned yesterday.

Riding down the trail it makes boost basically as expected and linearly with engine speed, throttle response is good for the most part through the mid range (finally)

Hop off the trail to shoot up through the trees and it hesitates a bit then will spool up but then only will show about 4-5 lbs of boost even though it would be spinning up towards 9-10,000 RPM.

Supercharger is mechanically stupid and I checked all my boots and connections and all seems well with the 'big' connections that would be able to lose ~5psi @300CFM.

So where should I go looking for my missing boost?

 

[rxwarrior]

Off trail you have more track slippage and go into a no load (so to speak) condition so the boost goes away. If you ride your brake off trail I bet you will see the boost climb.

 

[Srxspec]

Load has nothing to do with boost on a Supercharger. Boost is all determined on engine RPM. When you jumped back on the trail did your boost come back up? Throttle bodies blow off? Clamp loose somewhere? I'd start searching for an air leak, if it isn't that then look towards the supercharger itself.

 

[badluck]

Charger drive belt? Known for stripping the cogs off if not adjusted properly.

 

[kwb]

boost is good on trail/hard packed snow both before and after but in the soft it seems to hold at about 5lbs when motor is spinning ~9000 and on trail it gets close to 9lbs at same rpm.

 

[KnappAttack]

It's because when your in the snow, you have the throttle bodies open, and the boost, or maybe I should say volume, is going into the engine. You limit the boost, (volume) on the trail with the throttle shut further. You have the boost gauge connected on the intercooler. If you were to hook the boost gauge up to the vacuum lines, you'd see more boost in the deep snow with throttle open. The hesitation is very likely a lean spot. Mike Knapp#17

 

[Silverbullet]

I had a similar problem with mine....Some of the early transmissions had a slippage problem. If you rolled up the throttle you could build some boost. If you nailed it the boost seemed to hesitage or drop of at rpms above 9k. One of the fixes was a different oil.

 

[Apex]

where did you get your different oil? Did MPI send it to you? Or is just the supercharger bad? I have heard of several going bad right out of the box. Won't build boost. Hartman has had 2 or more that I was told.

They would build boost, but wouldn't hold it. Sounds like your problem.