GTOLarry

I would like to pulley down my S-trim to bring it in earlier and use a restrictor plate to prevent the over boost that will come by the much smaller pulley.

Anybody have experience with this? Looking for size of air flow opening, pulley combinations used, tuning issues, where you got the restrictor or the measurements you used to make it.

Thanks for any light you can shed on the subject.

Got Me SOM

iTrader: (2)

never heard of such a thing You sure you have a S trim? or is it a G trim?

only way to keep from making more power is to keep your rpms down or your foot off the pedal, lol.

Pro Stock John

iTrader: (34)

If you put a smaller pulley on there, you need to (a) figure how high you can safely shift and make the appropriate rev limiter adjustment, and (b) maybe look into having the pcm pull major timing out when the IAT's get above a certain value.

stevieturbo

Might be worth asking ECS or A&A.

ECS defo use them on their Paxton Novi2000 kits for the Vette.

chriswtx

iTrader: (5)

Yep... I use a restrictor plate on my ECS Paxton. A&A corvettes has also used them on Vortechs... Lets you run a smaller pulley so boost hits earlier but limits the boost at higher rpm...Works great...

GTOLarry

My blower is VORTECH V-2 SQ SC-TRIM. I have talked to more than one person who has done it and have seen an ATI equipped GTO with it installed.

Essentially you drop down a couple pulley sizes or whatever your max rpm plus some reasonable rpm increase for the blower is ok. Then you put what looks like a big washer in the intake to restrict max flow. You can end up with the down low grunt of a maggie and most of the top end that the centri type blowers provide. Of big interest to me is any information from people who have done this and experimented with pulley sizes and the I.D. of the washer. I know it can be done I have seen it and spoken with East Coast and A&A and they both do it for some of their installs.

Just hoping to get more "usable power" for daily driving. Got the pulley and A&A Corvettes is supposed to have the plates available next week. My car moves along pretty good but most everything happens from 3200 on and is very strong at 4800. I would like to see if I can lower all of that by 1000 rpm or so.

chuntington101

i have seen some dyno graphs on vettes running them! they look to pull very strong!

only heard good things about them to be honnest

Chris.

eb02z06

iTrader: (18)

I know ECS makes them for a Novi but for the S-trim it would be a bit smaller since the inlet is 3.5" I believe or 3.75". If you can give me the flange diameter of the blower inlet and I can make you a couple to try. The idea works-it shifts the torque and power curve over the left then makes the horsepower peak as boost levels off due to the restriction. So say you make 12 lbs inrestricted you'll make 10 lbs restricted but the power comes on sooner and peak is held onto longer.

No Juice

iTrader: (11)

Interesting. I always thought there should be some sort of way to do this. So this goes on the blower inlet, so it can't suck as much air?

Any pics out there?

stevieturbo

There are some pics somewhere on the C5 forum.

It is as simple/crude as a round steel plate with a hole in the middle, mounted over teh blower inlet.

GTOLarry

Inlet is 3.5 I.D. What I have found so far is that most look like a washer, but I have no idea where to start with regards to the actual intake opening of that washer. I am going to get one from A&A which will get me started.

I would like to get the opening size dialed in for my application (see how the A&A one works) then go up or down as needed for intake size. Then make something a little more sophisticated than a big washer, another GTO buddy suggested an hour glass sort of shape to avoid the air crashing into the broad edge of the washer.

Thanks for everyones input all is welcome and helpful since I have zero experience with these and only an idea of what I want to do.

Got Me SOM

iTrader: (2)

Good Luck , keep timing conservative on the upper rpms.

Do you have your alky control operating out of ww tank or did u use the supplied contatiner?

I need to get a boost a pump, my fuel press is droppin off in the higher rpms, my af is good but that kinda scares me,

GTOLarry

I have a very good tuner and all of this experimentation will be done with a dyno and tuner present. .. but you are right about being conservative.

Using the ww tank. Ordered it without a tank. Working out great for me.

I use KB Boost A. I recently put in a new SS340 Walboro in an 8.1 bucket (from a Hummer) which I hope will last longer than the last two fuel pumps. GTO had a small bucket and I think I was running it dry. Last month the car got a cam and spent most of the day on a dyno getting tuned, pump died after the ride home. Second pump in about 12K miles. Vortech used some pump out of some Mustang sort of looked like a Walbro but clearly not the same as a 340.

Going to forge the bottom before she blows so I can move up to a bigger blower.

eb02z06

iTrader: (18)

These are the ones I make, these fit P1SC's, D1SC's, F1R's, Novi 2000's and Vortech T trims, Ysi's and JT's. You can use on a S-trim if you are using a 4" filter-like in the pics below. All you do is pulley down and watch the boost come on soner but peak and hold. I can make custom sizs too if required. There great for stock motors to limit boost.

DeltaT

iTrader: (5)

You are never going to get a centrifugal blower to have the "down low grunt of a maggie" - they just don't pump enough air until the rpm comes up.

With a restrictor, do you get a big temp increase?

Jim

chriswtx

iTrader: (5)

I only see 10-15degs above outside air temps with or with out the restrictor. Does not seem to matter...

engineermike

This is one of the silliest things I've heard of. I can't believe that people are actually installing restrictions on purpose!

When you install a restriction with a centrifugal supercharger, your compressor is working harder than it normally would need to. The air goes up to a higher temperature and pressure than normal, then is expanded through an orifice. Of course, due to expansion, it cools back off again, but since the compressor is less than 100% efficient, you've added more heat than you can take back out by simple expansion. IAT's at any given boost level WILL BE HIGHER than a slower spinning compressor with no restriction. Add to that the increased hp required to drive the blower with a restriction on the outlet and you won't be making nearly the hp at any given boost level that you should be. The whole system becomes less efficient and doesn't make the power that it's capable of making.

I got an idea, spin the blower faster and then short-shift it. That would give you more low-end, but if you shift at 5000 rpm, then you won't see the higher boost levels. Sound silly? It's not half as silly as adding a restrictor . . .

On second thought, pulley the supercharger up to get more boost down low, then make a bunch of extra power up top due to the added boost there too! Retard the timing some if need be to control detonation. I think if you spin an S-trim to its max speed on an LS1, it won't go much over 10 psi anyway.

Mike

lt1s10

iTrader: (2)

or maybe a wastegate to bleed the boost off.

GTOLarry

I know, it just doesn't sound right when you talk about it but in practice there are folks doing it and apparently it works well. I will let you know if it works for me. I felt exactly the same way, but after talking to someone who had done it and liked it, I have to give it a try. If it all works out I will have a car with more daily driver type power, which I would invite since my car is a daily driver.

GTOLarry

You are right they don't pump enough air until the rpms go up which is why you have to drop pulley sizes to get the rpms up earlier and use a restrictor because you will have too much boost on top end.

Tuner says yes but easily able to tune around changes.