I'm thinking my blower isn't putting out the boost it should.

Heres the specs.

*Near stock camshaft, zz3 would be a good cam to compare this one too.
*shifting at 5500rpm.
*aftercooled
*6.66 Crank pulley
*2.95 Blower pulley
*355
*9.1

Its only making about 9.5 pounds. Is this right?

 

It may be a tad low, but not off by too much. I have the 6.66/2.75 pullies and am making 13 psi at 6500 rpm. I have a hard intake pipe and billet MAF ends, which helps boost come up some.

At your compressor speed of ~45000 rpm, the S and T trim compressor curves are flat from 300 to 470 gm/sec, so the cam/heads will not change the boost by much until you get up higher in flow.

Mike

 

ROOSTER93V8, which Vortech supercharger do you have? I have an S-trim, and am running into the same problem. I can only hit 11psi (no intercooler or aftercooler) with a 350, with stock heads and intake.

 

I appreciate your responce..

I have a T trim with aftercooler.


Mike,
How much boost are you making at 5-5.5K? I think some of the problem is I'm not turning it hard enough.

Your also saying that with the T trim the engine doesn't matter as much as it usually does?

I have a 2.5 pulley but its not space correctly and it doesn't seat agianst the nose of the blower like the 2.9 and 3.xxx

 

I haven't measured it at 5500, but I'd bet it's around 11 psi.

With the T-trim, as long as you're in the 300 - 470 gm/s range and 45000 impeller rpm, engine mod's won't affect boost much. That's roughly equivalent to 300 - 500 rwhp.

I'm actually in the same boat as you, so this is what I did (a little math required): Go to:

http://www.vortechsuperchargers.com/...-trim_map.html

lb/min = gm/sec (from the MAF) / 0.127

Cross over the lb/min and the compressor speed, and you find that you should be running a pressure ratio of around 2.05/1.

So, 2.05 * 14.7 = 30.1 psia = 15 psig boost. But you're only running 9.5.

That's OK 'cause mine should be making 22 psi, but it's only making 13. Looks like you're actually doing better than me. One catch is that the Vortech charts and impeller speed calculators assume no belt slip and the pressure readings to be just before and just after the compressor.

I measured the pressure just upstream of my compressor and got -2 psig, and just downstream and got 14 psig. Now my actual pressure ratio is (14.7+14)/(14.7-2) = 2.25. Plotting this on the compressor map, where I should be 2.5/1 ratio, I get about 9% belt slippage. Sound reasonable?

The trick to getting boost might be increasing suction pressure as much as possible (hard intake pipe, which I have), larger air filter, and maybe MAF relocation to pressure side. This could be worth 3 - 4 psi boost. Also, grippy pulleys (http://www.reichardracing.com/pulleys.php) or cogs would get rid of the 9% slippage, which could be worth around 3 psi.

Comments from anyone able to read compressor maps???

Mike

 

Awesome,

are you using a hard intake pipe? I believe I might build one pretty soon to rid myself of the convulated tubing.

A few other thoughts might be

What is the D pressure across the aftercooler? How does it change at higher CFM?

What is the limit of the vortech bypass valve? Shoudl be easy to measure with a vaccum/boost gauge. (if it works there should be -2psi in the return on your car)

Its hard to put a number on belt slippage especially at higher RPM. I know that when we dyno vortech fox bodies you can watch the belt get centrifically thrown out. You can't really watch them on the LT1 cars.

I'm currently using a polycog belt from advance auto, and with my eaton setup I would find that they would grow a inch after a few hundred miles. It would be sweet to compare it to a gatorback belt or something else not so prone to strech.

PS. Do you know Mr. Moates? he lives in your town and is a engineer at Mobile I believe.

 

Yes, I fabricated a 3.5" mandrel bent pipe to connect the blower to the stock Vortech plastic pipe. It replaced the drier duct only.

I'm dropping 1 psi from the blower discharge to the intake plenum. So, it's less than 1 psi through the piping, intercooler, and throttle body. I was a test where the Vortech aftercooler caused a .03 psi drop in a 270 rwhp motor. You can extrapolate that to higher hp levels using this:

Dp = .03 * (rwhp/270)^2

So, at 550 rwhp, I have around:

Dp = .03 * (550/270)^2 = 0.12 psi drop

I believe the other .9 psi lost is through the throttle body since I still have a 52 mm.

I'm actually running a DSM Gen 2 bypass. The Vortech valve is good up to 12 psi and DSM Gen 2 is good for 15 psi.

It is actually best to have zero vacuum upstream of the blower. Ideally, the suction of the blower would be open with no piping, MAF, or filter.

Yes, I work with Craig. I actually have his WBO2 right now and need to return it. We talk about once per week and he's done a few "experiments" on my car.

Mike

 

Wow, that is a relatively low pressure drop across the aftercooler and snaked plumbing after the blower.

Good point with the throttlebody, I have a 48 and 52 on hand I might try them back to back and record the 2 bar map voltage.

I know that idealy no vaccum in the blowers intake would be ideal but the ultimate test to see that the bypass valve isn't leaking at all would be to record pressure in that hose (preferabally close to the valve) and compare it against the vaccum in the filter or at the blowers inlet.

Did you see a gain with a hard pipe? The vortech piece isn't horribly convulated and seems decently strong but i'm sure theres still something to be had.

What type of filter are you using? -2psi is rather significant, its 2 psi you could have in the intake instead. I'm using a late model vortec truck filter (3.5'' inletx 10-12 inches)

Tell him I said hello, hes mentioned to me several times about a buddy with a 383 t trimmed camaro. I put two and two together when I saw your location.

 

The Vortech Aftercooler is underrated by most in terms of pressure drop. You lose boost when you install it due to cooling/condensing the intake charge. Most don't realize that you actually lose boost upstream of the aftercooler also, which allows the compressor to flow more.

I don't think you'd see any pressure in the hose near the bypass valve. There is not enough restriction in the hose at those low (leakage) flow rates. The ultimate test of the bypass valve is to install it backwards and see if the boost rises any. Mine didn't.

I might have seen .5 psi with the hard pipe.

I'm using Vortech's supplied filter. Perhaps if I relocate the MAF, I can fit a 1" longer filter. However, I think most of the restriction is in the MAF. Actually, -2 psi before the blower translates to 4 psi at the discharge (2/1 pressure ratio).

2+2=4 That would be me!

Mike

 

Or go mafless?



From the pictures the stock vortech filter looks pretty tiny.

 

D@mn you speed-density people.

 

Funny, I hardly ever look at the boost gauge anymore.... cause once I punch it I keep my eyes on the road and listen to the engine.

Anyway, last time I looked, it was defineatly over 10 pounds, probably 11. Your 9.5 sounds too low. My pulley combo is also 6.66/2.95.

I had a procharger setup for 12 psi, but only saw 11 also.

As far as the comparison between the 2, I like the vortech a lot better. The V2 makes more mid-range torque and I am convinced the aftercooler (air-water) works better than an intercooler, especially when it gets hotter outside.

I relocated the MAF to the pressure side and installed the vortech max-flo blue bypass valve. The bypass was installed between the outlet of the aftercooler and the MAF. It works pretty well. The only downside is the idle isn't as smooth. The bypass valve is vented to the atmosphere, and it is very quiet, can barely hear it.

The inlet piping to the V2 is stock vortech. Way better setup here than procharger, especially the plastic piece inlet directly to the blower. I think a solid intake pipe may be worth 1, possibly 2 psi at the most.

Funny also how you mentioned the MAF being a restriction. I decided to try putting the factory screen back on it. Bad idea, it ran like crap.