One of my biggest complaints with my Vortech system is boost. It does not fully come on until around 6000+ RPM. I was thinking of a way to improve the spin up time without hurting the internals. Here is my idea.

1. Return the blower to Vortech and get the system rebuild to support lets say 15-20lb of boost. (i.e pulleys or whatever is necessary)

2. Remove one piece of the piping for the SC and have the following installed inline, pre MAF. (Tial Wastegates 38mm with .7Bar (10.15 psi) spring. http://www.lightningmotorsports.com/tialsport.htm


By doing this we should be able to attain higher boost levels at lower RPM yet still not exceed the max boost tested by users on this forum. Now understanding I am NOT a mechanic so please put this all into perspective. Any comments on my idea would be greatly appreciated.

 

Are you still running the 3.33 pulley? If so, try the 3.125--the smaller pulley will not only get you higher top end boost numbers, but should* also get you into boost sooner.

*I can let you know for sure when I swap mine out this weekend.

 

yes, swapping the pulleys helps, the boost IMO does come on faster, and has a better "FEEL" to it, i gained about 10 hp thruout the entire band,

supposedly our blower can support something like 25-30psi, or something close to that, Forced mentioned it in a previous post, but they are close to being maxed out already. we need to find out how to harness that power.

 

Doesn't the Vortech and ATI have some kind of a by-pass valve that could control the peak boost? Or does that bypass valve just vent air under vaccuum.

 

BOV, i think it just vents air under vacuum.

 

Yeah, the bypass on the Vortech only vents under vaccum--when you're driving it (without the "muffler" you can hear it pushing out air when you're cruising--it stops as soon as you give it some gas).

 

Does anyone see a reason why this would not work for our SC units????

 

A wastegate is designed to vent hot exhuast guages after the turbine generates enough positive boost to open the spring fully on the wastgate. There are two sides the the wastegate..the manifold side, and the downpipe adaptor side.

I am not certain if a wastegate would work with outlet charge air. And if its did, you'd have to do some fancy piping fabrication to get it all to the work. I guess you'd have to vent the excess compressed air out into the atmosphere. It's a thought provoking idea nonetheless.

If I was a betting, i was suspect this will not work. If it did, it would be the PERFECT way to generate insane boost at lower RPM, ala TT...and everyone would be doing it.

 

Some people do this. I know of a NSX with a Centrifical Superchager (Paxton) That did this. It works fine however the draw backs are as follows:

You waste even more HP to compress the extra air that your going to just dump.

The air you do keep is heated more than what is the standard for that boost because the SC had to build up to the higher pressure that you dumped some of.

That's alot of air to dump at redline. Say you want 10 psi across @ 3k (just to keep numbers easy). You would pump double that at redline 20 psi and dump 10psi, that's alot of air!. So it makes a TON of noise and since the air is heated alot more than the normal for 10 psi you'd make roughly what a normal set up @ 8psi would for peak HP.

Like GQ said if it was easy or work great every one would have done it.
Gary

 

in no way am i trying to insult you i just wanted to state that this will be the case regardless of the boost pressure you are running with a centrifugal blower. the max boost is always at peak rpm due to the centrifugal design! roots style blowers alow for sooner peak boost like tt kits......again, no disrespect with this comment, it just seemed as though you expected differently from your above statement!

best of luck,
-justin

 

yeap, running 8psi at 3k rpm would be very hard on your engine. Since it takes more power to spin the supercharger you will have massive parasitic loss and I don't think u're engine can handle it. Suppose u are running 8psi at 3k rpm and it dynos at around 300hp @3k rpms at the wheels. Realistically, u are actually doing about 400hp to the crank@3krpms since the engine has to work extra hard to spin that blower.

I too have complaints abou the lack of power at the lower rpm's. You should consider a 50-75 shot of nitrous to give you that extra torque down low where boost is lacking.

 

Putting a wastegate in the discharge tube off the SC can be used to limit boost. But, there are some huge problems with doing this. First, you are still spinning the S/C faster. The faster you spin, the greater the drivetrain loss from turning it. The faster the S/C compressor spins, the more air it compresses and the greater the temperature of the discharge air. At those boost levels you will have over twice the drivetrain losses so even though you may still be making 8 psi at 6000 rpms, you will actually make a lot less power than one just running the stock pulley.

This is actually why roots superchargers and turbos exist. With small turbos, you can hit peak boost at 2-2500 rpms and have it flat to redline. Roots superchargers make boost down low and carry it flat to drop off some as you reach peak rpms. The disadvantage is that the compressors are terribly inefficient and don't have the power capability or a centrifugal S/C or turbo.

 

There is a way to fix your problem....U can do it in more than one way. The first one is to run a small pulley (2.70) or so on the blower and bleed of the extra boost using some kind of valve (ie. wastegate for turbos), but u can face the problem of belt slippage here. The other one is to run a larger crank pulley and a larger SC pulley. Every 1 inch increase in the crank pulley equal .5 decrease in the SC pulley. So when u increase ur crank pulley diameter u increase boost giving the same SC pulley. The trick is to max out your blower and bleed of the extra boost hence u get full boost around 4-5KRPM and hold it to red line without over boosting the motor. If I remember correctly the V2 Vortech has a max impeller speed of 53000 RPM. I’m assuming u guys have a 6 inch crank pulley now and a 3.33 step up ratio in the blower. I know some Votrech’s have 3.45 step up ratio. So if u are running the 3.33 blower pulley then that means u are spinning your blower around 40800RPM that if you revved to 6800RPM. That means u still have around 13000 extra RPM’s u can get out of the blower. I’m not sure if u can fit a 7 inch crank pulley (U have to check on that) then u just need a 2.95 inch blower pulley to get around 53731RPM out of the blower with no slippage problems. This should give u anywhere between 12-14psi on your car. ASP can make u the pulley if u need it.
There are drawbacks to this solution, one of them is the extra heat generated by spinning the SC at a higher impeller speed hence a little bit higher IAT (Affects timing a little bit). To avoid the seconds problem u have to bleed the boost before the MAF or MAP so the PCM won’t get confused. I would try to bleed the boost off before the intercooler if u are going to do it.
Now the advantages are: U can run something similar to a boost controller and when u get race fuel, u can just turn the **** to close the valve and u have the extra boost without changing a pulley. Another advantage is to have almost full boost (8psi) around 4K RPM if u are running a 13psi pulley setup and bleeding the rest of the extra boost on pump gas.

Sorry for the long write up, but I had this idea for a long time now and I figured it might interest u. Good luck.


EDIT: I just saw the post above me......