I just put a monoblade on my car and I'm having a hard time getting it to return back to closed. It will hang open and let the car over rev.

It doesn't do this off the car, nor does it do it with the blower belt off. It does do it with the bypass valve completely off the car and venting to atm.

I'm thinking that it just can overcome that huge pressure differential between what the blower is putting out and the 20 inches of vaccum this cam makes.


Whats a fix for this? I'm thinking about drilling a hole in the blades as there is nothing now!

 

so even if the bypass is open and the pressure is venting, it TB is still open a little?

 

yes it will still hang.. The only time it will not hang is if I take the intake plumbing completely off.

Even with the bypass valve completely off the car and just venting to ATM the blower puts out quite a bit of air.

I didn't mention it but I even put a aux spring onthe throttle bracket.. that didn't help at all.

 

Does it still do it with the inlet tubing connected & the blower belt off? This will prove it is pressure related & not due to a bind placed on it by the tubing.

 

I am having the same problem. I am going to drill a 1/8" hole in the throttle cam where the cable attaches and the plastic piece behind it and put in a 1/8" pin in to hold the two pieces together. If you do a search for monoblade in the forced induction forum there is a post about it from 2 years ago.

 

Have you tried contacting AS&M about it?? That's a pretty expensive piece; they should be more than happy to help you out.

 

yeah, they want me to send it back.. but I dont' think its really there problem.. I think the larger surface area makes it impossible for a spring to control with so much pressure on one side and boost on the other.

 

I saw that also, but i'm not sure if thats really my problem or not.. The throttle linkage and the shaft seem pretty damn solid to me.. It just doens't have enough spring to close itsself once air is slipping past it.

 

Maybe a higher flowing bypass valve is in order?

 

Maybe an old carb spring would be able to pull it closed?

 

I have not lokked at mine in about a year, but I think the cam that the TB cable is on is not directly connected to the shaft. This is why the 1/8" pin fixes this situation. I may be wrong, but I am going to do this in about a week when I get home from school. I think I read on here 3-4 years ago about someone trying a larger spring and it did not work for the reason above. I will reply with my results of whatever I do to fix it. This problem will scare the mess out of you and is very dangerous.

 

Yeah, the throttle cable on mine has a machined flat.. so it moves directly with the shaft.. absoulutley no room for play whatsoever.

I re-wound my spring as hard as I could and its a bit better but still has a tendancy to hang open every once in a while.

I'm going to put a stronger return spring on it.. Why the hell didn't they make this thing with a bigger spring or with the plate offcenter on the shaft so vaccum would close it

 

Wouldn't that cause it to idle high too, or can you tune around it?

 

That's the problem.