What pipe diameter do you have between the air filter and compressor inlet?

Can you replace a part of it with a pipe with an orifice inside?

If the belt slip is not too severe, then that issue might resolve itself with a restrictor.

 

There actually is no pipe between my filter and blower, it mounts directly.

As to the degree of belt slip.....I had previously pulled 10psi at 5,000 rpm, but was only getting 7psi on the dyno pull. Other factors that may have influenced that: the chaging from stock runners to SLP's, the head and cam change (was stock previously). The chart clearly showed a rapid peak and valley pattern, with no timing pulled or knock counts recorded. I suppose it could have been a result of the BTM pulling timing, but that would be an unusual look in my opinion.

 

It was muscle mustangs and fast fords. I posted the magazine month # and there was a little discussion about it. Seemed like a pretty cool setup..

 

http://www.musclemustangfastfords.co...all/index.html

Just when I thought I had made up my mind.....

 

Looks like you have a few low cost options:

1. Stick a 3 1/2" - 3" exhaust reducer or similar inside your cone air filter to serve as an inlet restriction.

2. The pressure relief valves already discussed.

3. Larger pulley.

Or the high cost solution (wastegate).

 

seen some of the resitrictor plates in C5 FI

simple.


personally, I would probably try out all the ideas starting at the cheapest, and figure out what I liked the most

more resitritors.

 

That seems easy enough. Now I just have to figure out what size.

 

Yeah, I guess that makes sense - blowing up an inflated ballon is just as hard whether or not it's leaking.

 

Are you sure the lower boost is due to belt slip? A stock cam has a lot of overlap, and going to an aftermarket cam (even a "blower" cam) increases overlap a bit and will reduce boost. Also, your blower is supplying a fixed CFM of air at each RPM, and by the changes to your engine, you've increased it's CFM throughput, which will also reduce boost (on your gauge). HP may go up even with the lower boost; CFM thoughput (actually the mass of air) is what makes HP.

 

From the C6 FI forum:

I did not even know that a company was selling restrictor plates for centrifugal superchargers. I posted this idea several years ago but at the time people did not seem to understand the benefits of a restrictor over a bov solution.
It is good to see that it works as I thought it would.

 

I have to correct one statement. A centrifugal supercharger does not have a fixed CFM of air at each RPM. A roots type supercharger works like that.

The rest is true.
Modifying the engine will increase the CFM throughput and if the supercharger is near maximum flow boost will drop a bit.

With more CFM throughtput the supercharger will use more hp from the belt and that makes any belt slip problems worse.

 

Mainly what I was referring to was the "graded" or rapid peak and valley nature of the dyno chart until ~5,200 rpm (boost was consistent at 7psi until that point), and then the sudden jump from 7 to 12psi within 150 rpm. Again, no timing was pulled, and no knock counts were being recorded. That lead us to believe we had a belt slip issue (indeed, after quick jumps to full throttle, followed by a sudden let off, I do get a second of belt squeel).

I check the belt tensioner last night, on Greg's advice. After the tensioner initially makes contact with the belt, it continues to close and additional 1.5-2". I can manually tighten the tensioner another 1-1.5" using a torque bar. My alternator idler pulley is rather small at 2.25", so we are going to step up here, and most likely i will install the smaller idler closer to the blower drive pulley to get additional wrap.

 

There was actually quite a wealth of information on the C5 FI forum. I contacted ECS with some questions as to the size of the restrictors they would recommend, or even fab up, but I kind of got the brush off.

Here's their response:

"Its really a very simple thing that you can do yourself. Just use a small aluminum plate and start larger and work your way smaller as you want to increase boost."

Although that logic seems a little backwards to me. I would think the smaller the diameter, the less boost would be yielded. Maybe he just mistyped, 'cause I think that is absolutely incorrect.

 

What he is trying to say is ... If you switch to a smaller supercharger pulley to increase boost at lower RPM, then you need a smaller hole in the restrictor plate to keep the boost low at high RPM.