Vortech S-trim Questions

[final5-0]

I have wanted to ask this Q for a while and today I'm gonna do it

I'm looking for general info mostly so keep that in mind.

The Vortech blowers build boost with an increase all the way to the redline.
I know that!

Having said that
Most of the good stuff happens from mid range rpm and above.
Would most of you who have experience with Vortechs agree?

If one pulleyed a Vortech for more boost
Would you see boost start to build at an earlier rpm

I really am looking for a good discussion here as I've never driven or even been in a Vortech car.

Vortech guys ... give me an idea of what happens if you please

Grady

 

[95CobraMike]

I am going to go ahead and say that Yes i think that if it were pullied diffrently for more boost, you would see and feel more boost faster... meaning you would feel the boost in the lower (not so much low but lower than normal) RPM's

Why do i say this? when you change the pulleys on the s-trim or crank for more boost, you are changing the rotational speed of the s-trim....not the engine the engine still cranks at the same speed meaning more rotational speed of the s-trim but the same amount of engine rpms...

lets say that with pulleys to make 10lbs total boost you see 10lbs at 5500 RPM's

now you change to pulleys to make 16 lbs of total boost, you are no longer going to see 10lbs of boost at 5500, you'll see 16lbs at 5500 and you will have achieved 10 lbs at (guessing) around 4000ish rpm's

Here is a link to vortech's site with a calculator to project impeller speed at a certain rpm....you can change rpm's and upper and lower pulley size

http://www.vortechsuperchargers.com/support/impspeedv-1.html

so in summary, with pulleys to make more total boost, you will see higher boost numbers at lower engine rpms.

therefore i believe you would feel the s-rtim pull at lower rpm's

hope it makes sence?

 

[95CobraMike]

oh, btw.... with 10 lbs of boost at WOT starting from 0 mph you dont really have any traction through 1st gear, but then in 2nd and 3rd gears it is in the UPPER rpm's around 4000-5000 rpms when you start to see traction issues again...when you get the boost built up again.... its pretty sweet

 

[final5-0]

Mike

If you did go from a 10 to 16 pulley

Would that mean that you would make the same power at a lower rpm where you now see 10lbs?

Grady

 

[Killercanary]

Grady, good topic to bring up, its one I am sure a lot of people get confused about. We often hear people say... "I'm running Xlbs of boost" but what we often don't talk about is at what rpm. Boost is a measure of backpressure, which is a result of the additional air being pushed in by the blower. The cent. blower moves more air the faster it is spun, and that is a direct result of engine RPM, so spin the engine faster given the same pulley size and the more air that will be pushed into the engine and as a result the boost/backpressure will continue to increase.


Pulley the thing for 20lbs and run the belt loose and you could have the best of both worlds... high boost down low and it will taper off up top due to belt slippage. The belts won't like it but it'd work until the belt final throws in the towel.


I'll have to respond more later, I'm too involved in the steelers game! I have a lot more to add though.

 

[95CobraMike]

Mike

If you did go from a 10 to 16 pulley

Would that mean that you would make the same power at a lower rpm where you now see 10lbs?

Grady

i dont think so... i think power is related to PSI AND Rpm's
you will make more power at lower rpm's, but i dont think/dont know if you would make as much power at 10psi now because the rpms arent there....
lets say you had 400hp at 10psi at 5500...now you are up to 16 psi... You WILL hit both 400hp AND 10psi BEFORE 5500rpms, BUT, do you hit 400hp AND 10psi at the same time?? i doubt it.. but, i really dont know for sure, its just a guess

there has to be a formula for this.....

 

[final5-0]

Thanks for the info Paul.

Yes, boost is one of these subjects that I have seen peeps talk about but sometimes their comments just don't add up. I'd much rather have less boost on a motor that can move lots of air than on a stocker that won't move any air but shows high boost.

Maybe this is just one of those bragging rights kinda deals and the high boost value is sorta like high peak dyno numbers but a poopy torque curve that doesn't get talked about.

Anyway

The boost thing is not where my interest lies.

I have always wondered if you could play with pulleys to change how much the blower spins and kinda find the in-between place between a cent blower and a KB.

Grady

 

[S/CBlack95GT]

I thought about doing this a couple years ago and it does work. I dont run my car to redline that much so I wanted to pulley it for around a max of 14-15 psi at 6000rpms. This way I would have more bottom end (not that it needs it with 360rwtq at 3500rpms ).

 

[turbogt]

Yeah, It just depends on how fast you are going to spin it. I see full boost by 5000, so if you pullied it, you would probably not want to spin it anywhere near redline. I too have thought about doing the same thing, but said screw it and am now going Turbo!

 

[94GTLaserRC]

My $0.02:

I think the "sooness" in the RPM band is over-analyzed.

When I "gun it", my Tach goes from 2000 to 3500 in such a miniscule amount of time, I hardly think it matters.

All the stuff said above makes sense and is logical, but I think it's like leaving an accordian in an unlocked car:

It just doesnt matter

RC

 

[final5-0]

but I think it's like leaving an accordian in an unlocked car:

It just doesnt matter

RC

A Gem if I ever saw one RC

Screw all that Tech Stuff

That one I'll remember ........ and use when the time is right

Grady

 

[95CobraMike]

Yeah, It just depends on how fast you are going to spin it. I see full boost by 5000, so if you pullied it, you would probably not want to spin it anywhere near redline. I too have thought about doing the same thing, but said screw it and am now going Turbo!

actually at 10psi with stock pullies you are not really anywhere near the rpm limits of the s-trim.... when you start getting into the 16psi range (whatever the pulley sizes are...2.8" and 8" or whatever) then you start scratching close to the limit of rpms on the s-trim i think its something like 50,000ish? i think with stock pullies and 5500 you are at about 35,000, and with a 2.8" and 8" for approx 16psi you are at 54,000 rpms

does that make any sense?

this info i got using the impeller speed calculator up in the second post of the topic

 

[Killercanary]

It'd be cool if you could setup the vortech to run on its own pulley that is setup like a centrifical clutch setup on a go cart, more commonly refered to as a torque-a-verter. At low speeds the drive pulley would run the belt our at the outermost edge of the pulley thereby turning the vortech faster at low rpms, and as engine speed increases the drive pulley expands and makes the belt travel on the inner side of the pulley where the diameter is smaller and it would drive the blower slower. I'm sure with enough desire this could be done, it wouldn't be pretty as the drive pulley setup is quite large, but it'd give you the best of both worlds.

Here's a link to a torqe-a-verter.
http://www.bmikarts.com/shop/index....91c0444def0f4c9b145f1d70f898e9&thumbval=thumb