Travel limiters and fine tuning the suspenion would work wonders...Take some pinion angle out if you have to.

 

I don't think kp needs any help in this area. . .

 

V6 Mike, you are trying too hard to come across as Mr. Expert.

Just bustin' *****.

So all this convo just to avoid a cam swap?

 

Nah, a cam swap was a potential upgrade anyway, all this convo just to see who here, if anyone, has used either the restrictor or a gate. I like having the stock cam just to say "yup, I am making 650 whp on a bone stock motor", but I have no love for it- I'll yank it just as soon as leave it in!

This just got much more "techy" than I wanted it to. If you go to the GTO or, especially, Corvette forums, you will see plenty of street cars running smaller pullies and restrictors and the gains are substantial. Yes, it take a bit more power to run the blower at that RPM, yes it will create a "hotter" air charge, yes it will make more power in the same spot with the smaller pulley and no restrictor than with the restrictor- BUT- it will also make more power with all these negatives than it will with the bigger pulley and no restrictor- that has been proven time and time again. There is a lot more to it than "well the numbers say it isn't optimum". Maybe not more peak power, but more power- especially torque- where you need it. While Mike appears to be a ridiculously knowlegable guy (compliment intended ), I will go for "yup, it works- I have tried it" over "the numbers say it won't" any day of the week. I have a friend who was working on a project car and the words "this will be a full 'math car'- no hacks, just a perfectly calculated 8 second car" were used to describe it- the car ran 11's on it's best day when all was said and done and needed old school "toss the calculator and just do this" techniques to get it there .

I just wanted to ask here since you guys are a bit more "hardcore". While the other boards have some serious cars also, I have seen too many "what cam (or headers) should I go with for the best sound?" posts on the other boards, so that shows the seriousness of *some* there .
Joe

 

Someone needs to re-calibrate their calculator.

 

Lol- while I do not have the engineering degree to back that up, it is pretty funny .

In all honesty though, you don't know how many times I have been to the track- especially with my old DSM's- and got the "you can't to that- according to blah blah blah, it will not work and will cause blah blah blah" from the tech geeks. I'd do it, and the car would get faster and they'd usually have an intelligent comment like "what the fuxor, that shouldn't have worked"...
Joe

 

I can appreciate what you were after and how you would benifit from a simple answer.
The fact is however, and this is not meant to be a slight to anybody but many of the Corvette forums and what have you aren't real techy and many just parrot what a vendor says and its like any other kind of gossip or lore. The information you receive can often times have details missing or replaced with more convenient? "facts". This board tends to appreciate more in depth tech for the most part and likes to beat topics to death. I also feel this board has more manufactuer and vendor participation that those you may also frequent.

As you can see sometimes I have a hard time getting to the point and I apologize. There may be times that we may hypothesise about issues we don't have any hard data on, but its usually based on solid thinking and past experience. To beat that we're actually willing to test and share the data. I haven't seen a bunch of that other than dyno sheet racing on the other boards.

Luckily on here we aren't real concerned about winning a popularity contest and are still able to defend our position without the cost of the chassis and the depth of our bank accounts getting in the way.....if that makes any sense. We're just dealing with the powerplant here for the most part.

I hope you were able to take away some useful information about what the modifications actually do and what effect they may have. If all else fails cut a hole in a piece of metal and give it a try, just try to gather some repeatable data in the process to think about and share.

 

So, lets take a near stock LS1...street car that we track race on the weekends.


346, Stock Bottom, Heads/Cam, D1 witha 10psi pulley...

On a typical supercharger...you see boost in a linear fashion...as RPM goes up, so does boost. You only see 10lbs at the VERY tippy top of your RPM range lets say 6000.

Now, lets pulley down and put a restrictor in there...
Now you see 10lbs from 3500-6000...


How can you say that wouldn't help the area under the curve?




To me, restricting a supercharger is GREAT! It will allow street car blower guys to hang with turbos....which make power in the same NON LINEAR fashion as a retriced blower car.




Am I missing something here? This sounds like a great idea.

 

I agree- that's why I came here .

I honestly appreciate all the replies- positive and negative. Thanks for taking the time to post!
Joe

 

All I'm saying is that a restrictor will DEFINITELY have less area under the curve all other things being equal.

 

I don't think anyone ever questioned that, but- it isn't "all else being equal" that is the scenario here. It is adding boost in the bottom end while limiting top end boost. Sure, no restrictor and more boost will make more power all around- that's a given- but, in this example- more boost = boom .

Heh, now I am kicking around just ditching the Procharger and going turbo. I put a post in fab, but figured I'd ask you too- any ideas where I can get stainless LSx header flanges from?
Joe

 

HOW?


Now remember the setting... the motor can only handle 15psi...

I wanna run 10, since it is my safe little street car...

I could run


or, with a restrictor...



How would area under the curve be less with a plate (or WG)?

 

from what im gathering...... unrestricted the blower is drawing in air and compressing it with basic amount of effort.

now restricted it has to fight to pull in air. that causes heat and extra load on the blower and in turn your engine. yes you now have 10 psi at 4000 rpm but with a higher iat count and additional losses from the blower fighting to draw in air. now when you hit 5000 rpm the penalties increase, and at 6000 rpm the penalties increase some more.

the exact penalty numbers is what no one can spit out but some form of penalty is there. the best way to find out is a back to back dyno and some same day track runs.

im my mind even though its a cheesy example its like taking a floor box fan. its power requirments is 1 amp on its high setting. take a piece of carboard and put it on the back of it with a amp meter on the power wire. the more you restrict it the higher the current or power needed to turn the fan blade is going to be. this is whats happening to your vehicles engine. but again without some tests the exact loses are unknown as of now. i hope it works as a got a d1sc but my hopes arent up.

 

Look outside this site- it has been working for quite a while for several people . It was even a recommendation by Procharger when I got the blower. They said a lot of their customers do it to wake up the under the curve power.

I didn't mean to start this huge debate, although it is very interesting from both points of view! I was just trying to figure out what the preferred method for limiting boost was here, but aparently it isn't a popular trick on this site- that does not mean that it doesn't exist though .
Joe

 

i hope to find out it does! im currently trying to decide on a longblock and if i go 402 or bigger i wont be able to resit moving up to an f1 size blower. wouldnt that be nice,restrict that bad boy and build max boost at 3500-4000 rpm....muuahhaaaahahahah!!!!!!!! id explore it but im aways from maximizing a setup, im trying to get the fundamentals together right now!!!! good luck

 

One problem is that your common centrifugal blower is not going to give you 7# at 3000rpm EVER - they just don't have a boost curve like that.

Also, you can't grossly exceed the max rpm of your blower, or you start psuhing a lot of heat and extra wear on the gearbox. Add in extra belt slip due to the restricted blower needing more HP to spin it and the tiny pulley you've got on the blower...

You cannot make a centrifugal blower have the same boost characteristics of a positive displacement (roots or twinscrew). You will never get good low end boost with a centri, or a huge midrange.

Jim

 

Really hmmm.... Can you explian the Boost curve on my D-1SC.... Its pullied for 13psi only and made 6psi on 3500RPM and 13psi at 6k RPM while keeping an avg of 10psi. When it was pullied to 10psi it made 4psi at 3400RPM and 10psi on 6400RPM with an avg of 8psi. If he used a 3.4 pulley with 7.25-7.65 crank he will see 7-8psi at 3000-3500RPM and an avg of 12psi accross the board to 6K-6300 RPM.

How about 500rwtq at 3500RPM and 600rwtq at 4300RPM. I would say that is a huge midrange on a stock bottom end... dont u say soo?

 

i think its a great idea! and as you said it has been tried and tested by others.

and as ZDOG said, imagine haveing a very save anf civilised 5-600rwhp daily drive thats nice and easy on everything, then at the track or when you fancy getting on it a bit, take the restrictor off and have some fun! oh you might need to have it SD tuned then though. but thats better anyway! lol

thanks Chris.

PS. haven't had chance to go back and look through the thread. but how is the weastgate coming on??? the one to help with traction??

 

Those numbers are examples. I am trying to show that you would be in MAX BOOST for LONGER with a restrictor setup...how can that not be an advantage?

 

I'm not sure how you are getting 6psi @ 3500, I have a small cam and 9.5: compression and with the 7.25/3.4 on a D1SC I'm only seeing 5psi @ 3500 and seeing 17psi @ 7000.

There were some good points in this thread but you have to remember sometimes results can be a little skewed depending on what someone is trying to sell plus the 'jones factor.' Its very easy to find an example to prove you point but just because something worked for so and so doesnt mean its going to work for you. My advice is always just try it for youself and see what happens, thats simple enough.

Here is a 1st gear a pass with my car with the 7.25/3.4 with the inlet hat on, I deleted a ton of frames to make it all fit on the the screen but thats with the 2step at 3500rpm up 7000rpm (max impeller on a D1SC). I cant honestly see 7psi @ 3500 unless its a 100% stock engine and if you are trying that the stock engine wont last long.