Supercharger Project

This is gonna be interesting, I like it.

 

Dude, that'll never work. Those paper housings will burn up when the engine gets hot. Also, I don't think that blue tape will hold it in place for very long.

I'd switch to duct tape and cardboard.








(Keep us updated!! Looks very cool)

 

Obviously the stock airbox goes away, but then how is air filtration handled?

Looking good!

 

I'm not sure which vortex unit you are planing on, but most are available in CW or CCW rotation

 

WOW looks all too familiar when I had a custom SC designed for my Mustang...Looks awesome keep it up...

 

It may be quiet, but people are watching.

 

Yes, we are watching... and this winter i think SOMETHING will be done to the car by someone.

 

To your car? Don't tell me our local mad scientist is gonna lay his hands on it.

 

Scott,
I'm not completely sure why (I.m pretty sure it's the flow profile of the heads), but 308QV engines are air pigs and I'm pretty sure the 308 2v and the 328 are the same.

When I was during my first SC set-up, I wanted 6-8 psi, which translated to 10 in my twisted world. I decided to go with an eaton roots (so there was a lot of thermal expansion contributing to the boost) and the engineer recomended a 62ci. I bought a 90ci figuring it let room for future upgrading. Long story short, I had that poor thing spinning to 16000rpm (it has a 14000 redline) to get 10psi. At 16000 rpm it pumps about 58 lb/min of air (90x16000/12^3/13.5X.95). 58 is a LOT more than 40. On a QV or 328 I don't think 40 will give you more than 3 or 4 psi of boost.

The unit I have now flows about 80 lb/min to yield about 20 psi and a little over 500hp....80 lb/min should yield 750+ hp according to the blower people and the research I did.

The bigger unit that will flow 60 lb/min is probably the one one need even if it is a couple % lower efficiency .

 

OK, but don't be surprised when you don't get the boost you planned for. I'm trying to help you aviod the mistakes that I've already made.

The superchargers I've tried rate flow by inlet CFM, so I converted that to lb/min at STP for you to be able to compare to the mass flow numbers that centrifugal units (turbo or SC) are rated in. No confussion.

I'm also using about 500 lb/hr of fuel with my current set-up and I used about 300 with the old set-up. That's enough fuel for 800hp and 500 hp on engines that actually made 520 and 360 respectively

The reason for the high fuel usage is that a lot of fuel is going straight out the exhaust unburned along with the extra air that's being pumped through. 308 engines have a terrible blow-down problem and are extremely wasteful of air and fuel because of it.

This also makes it hard to size a compressor because much more air is required than the math says should be required. I actually talked to the vortex guys when I designed both systems. The first time was looking at a V1, I don't think the V9 was out yet, that's when I made the exact same graph of boost at rpm you posted and decided I wasn't happy with it and went another direction. The second time I was planning a variable ratio drive and gave votex another call, but I finally just gave up on them because I couldn't get them to believe the numbers I was giving them and do the math right. The numbers are what they are and confirmed with 2 separate compressors, so it's not some kind of fluke where the first compressor just didn't flow the way it was supposed to.

A third data point is the turbo Paul (turboQV) has on his car, it's a 60-1 compressor which flows 65 lb/min and it makes 15 psi. A turbo does a little better with blow-down than an SC due to the increased pressure in the exhaust, but 65 lb/min should be good for 650hp, he makes 400 if I recall.

Now you know why my heads are off and being ported, I want to fix the blow-down problem and keep the air and fuel I'm pumping in the engine to be burned. I'm also planning on re-timing the cams to a 114 or 116 lobe separation angle, I currently have them at the euro 109 instead of the US 107.

 

I'm giving you data for the 7700 engine rpm point, no other point because that is the point you're using to set the design.

Paul's getting about 400 crank hp, not wheel hp, but there is probably a touch more flow left in the compressor, so say 60 lb/min to get 400. With a SC, I only got 360 from 60 lb/min, and that would be the differences in efficieny and blow-down. I'm now making 420 rwhp and using about 80 lb/min to do it.

Any way, know you have that data I have, I hope it helps.

 

Looking at the two compressor charts, if we go with the V1-SC and we do need to push it up to 58 lb/min like Mark recommends, it only requires another 1000 rpm or so (and stays about the same efficiency) where the V-9G is pushed up another 5000 rpm and into a much less efficient band.

I know the V-9G is smaller and easier to shoe-horn into the car, but the larger compressor may be the best bet.

I did some quick calculations too, and my numbers came out inbetween the two of you. Just my 2-bits worth.

Thor
www.JavelinArt.com

 

I'm very confused now for 2 reasons. First, I'm not doing any math, I'm guess giving you test data. These are real flow vs boost test results for a qv engine. Second, if an engine will make 325 at 9.85 psi with a centrifugal compressor, it will make 325 at 9.85 with a twin srew....actually a touch lower because they are higher efficiency. But at any rate, the hp is a function of mass flow, so if 325 hp requires 39 lb/min of air, then that is a constant regardless of boost, intercoolers, compressor type, it varys only if the engine itself is changed in some way. There must be something wrong with your spreadsheet.

The only math I did was to convert the inlet cfm of my compressor maps to mass flow to compare to your compressore maps. I used 13.5 cfm/lb for the convertion, that's all the math I did.

I think both the compressors you're looking at will work for you, but as you mention, will require a blow-off valve to aviod surge if you are building a blow-thur system.

The only thing I really wanted to warn you about is the pulleys. When I did my first system, I did what you're doing and talked to the engineers, got a compressor and the pulley they recomended for 8 psi and 10 psi...and got 2.5 psi and 3 psi of boost respectively. Trying to get it up where it belonged, I ended up with a 2" blower pulley which requires the belt to play a middle C it was so tight and it still slipped a bit. A 3" or 3.5" blower pulley is where you want to be with at least 180 degrees of wrap...and if you guess way low on flow to begin with, you'll end-up spending a lot of money re-making pulleys.

You might want to think about a second blow-off valve, the first one is what they sell as a blow-off valve and is vacuum controled and will prevent any surge problems. The second one would be a simple pressure-relief valve mounted after the throttle body. The reason is that you are going to have a couple things working against you.

The injected engines make peak torque at 5500 and peak hp at 6800 with redline at 7700. The torque dropping at 5500 means the VE of the engine is dropping, so it wants less air per rev, but the blower is delivering more. The hp dropping after 6800 means the engine's air flow (volumetric or mass flow) peaked at 6800 and is dropping, but again the blower is delivering more. So, if you set the drive ratio on the blower to give 10 psi at 7700, it may only be 6-7 psi at 6800 and maybe 3-4 at 5500 and you won't hit your hp goal which was based of boost at 6800 rpm.

On my graph the problem shows pretty clearly. If you look at the yellow line, you can swee it start to rise at 5500, then really turn up at 6800. And remember, this is with a scew type blower, so the volumetric/mass flow at almost perfectly linear with rpm, not expontential. A second pressure relief valve would let you set the boost at 6800 for hp and not be WAY over boosting at redline. You could probably assume the blower is perfectly linear and map the engines flow to code into your spreadsheet which will give you a much more accuate prediction of manifold pressure at any given rpm.
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Did you see the Voretc complete charge-cooled kits for Mustangs? About $5K complete, plug-and-play for a claimed 54% increase in HP.

http://www.vortechsuperchargers.com/news/2006_gt_ho.html

I wish it was that easy for our cars! Of course, maybe it will be when Scott is done with this project...