Ive got a Vortech v7 YSI with a 10 rib pulley setup. 3.7 inch blower pulley, and an 8 inch crank pulley. The car builds 17psi at around 7k rpms but that's where it peaks and falls off to about 13.5 psi at 9200 rpm. I can't imagine belt slip as i have tried to go above and beyond to eliminate belt slip with the 10 rib setup. I will mention the car is running on an aem v1 unit with 2150cc injectors and is otherwise completely bone stock. Stock heads. Stock bottom end. Stock intake etc.

Im looking for any suggestions, aka possible valve float, restrictions with stock throttle body etc.

I know it's probably not "safe" running this kind of boost on a stock motor but it does have a th400 behind it and is primarily used as a bracket car, making a few passes a month.

 

Is it possible the water to air ic is a flow limitation with your blower? What is your calculated flow capability with that blower spinning at the speeds your pulleys spin it at?

 

i went with a bigger water to air cooler. It is a 3.5 inch intake with a 3 inch outlet. I believe it's rated for 6 or 700hp. But that was before I made the inlet and outlet larger

 

The supercharger itself is rated at 1600+ cfm

 

So its the frozen boost type 14? That's rated for 700cfm. You enlarged the ports, so that's worth something. But its still going to be a restriction to a blower capable of 1600cfm.

But its not like it shuts down after its rated 700 cfm. It would just be more and more of a restriction. Difficult to say if its the root cause of your boost dropping off.

 

Also,it looks like ic is pressed against upper radiator hose, and impeding its flow. Its also putting a load on radiator bung, and with engine vibes and motion, could cause sudden radiator failure.

Be careful.

 

Worth a shot to:

1. Remove heat-exchanger and connect SC directly to the TB
2. Bump up your gas Octane rating as high as you can (to safeguard from knock) but if you're running E85 I wouldn't worry and leave as is
3. Retard 10-15 degrees in WOT cells (to safeguard from knock)

Now go for another run or two and see if boost doesn't taper down.

 

Just a quick update. Solved they problem. Turned out to simply be belt slip. I just really cranked down on the belt tensioner and took it around the block. Now to fine tune and get on e85. Thanks for the help guys.

 

That's more like it. My V7-YSi is putting out 31.4 psi at 71,000 impeller rpm.