kp

iTrader: (34)

I try not to post anything unless I have some actual first hand experience and have at least some decent, repeatable data to back it up. I'll be the first to admit I'm no engineer (hated math in college) so I dont mind valid input from a engineering/math perspective, comes in handy sometimes when trying to figure out whats going on when something doesnt add up. If you look at it straight from a hot rodder perspective the idea of an inlet restrictor seems pretty good, it appears you would lose nothing until the restrictor starts restricting at higher flow and have a nice flat turbo-like boost curve. But what andereck and yourself are saying makes perfect sense that it should lose everywhere, so there is something else coming into play since there are people that are doing very well with the inlet restrictors.

I'm not sure on the eye meaurements but I'm sure the compressor is near being maxed ou, at least for my IC setup anyhow. If I had an A2W I'm sure I could pick up more by spinning the D1 faster, as of now adding 6K of impeller speed (3.7 to 3.4 pulley) nets me 2 psi peak and 1mph in the 1/4. That same 6K increase in impeller speed (from 4" to 3.7" pulley) nets me 3.5psi and 8mph in the 1/4

Fire67

iTrader: (3)

This has been very interesting reading. Im no math expert, nor have I tried using any sort of boost limiter with a supercharger. But I value hard numbers to back-up or challenge a theory.
Mike - when you get back, please do go over the spreadsheet with your magic. I'd really like to see what you come up with.

kwiksilverz - you've seen the math/scientific side of the story, youve seen other peoples results, now the only thing left is to TEST this theory and report back with hard results. I'd like to see how well it does or doesnt do.
I personally dont think you'll get much of a gain outta that P1 though. If you were restricting the peak boost of a D1 I could imagine alot of new found under the curve power.

To me this idea would be best suited for someone buying a huge blower and putting it on a stock motor temporarily untill a new motor is needed. Basically buying parts for a badass setup, but finding a way to use them on a stock based setup.

LSs1Power

iTrader: (5)

I can send you the Excel file to give u a head start. I found that enthalpy = H = E + P*V where E is Internal Energy, P is pressure and V is volume. The problem is that im not really sure what units to use to make it give the right numbers.

andereck

KP - I should reiterate that what I was saying is that bleeding off boost that you've already made is not a good idea unless you're goal is strictly temporarily limiting power at the dragstrip as the losses are very high.

Restricting the inlet should not induce extra effort up to the point where you could measure the inlet restriction in the tube between the restriction and inlet to the supercharger. The efficiency of the supercharger should decrease as the inlet restriction increases as the charger is running over its air more times to produce the same airflow level as the available volume is less to feed it as rpm increases.

kp

iTrader: (34)

I agree with bleeding the boost off after the blower doesnt seem like a good idea (except for controlling traction) and a few people have tried it and it didnt work well. But if you add a restrictor to the inlest isnt there a point where it wont really hurt anything since the blower doesnt need that much air? Thats what some guys are doing to try to flatten out the boost curve a little, sounds logical and some guys claim it works for them. They are maybe cutting the inlet down 25% and pulleying up the blower to the max, theory being the restriction is just going to 'chop off' the boost on the high end and have more more boost in the low/midrange with the higher blower speed.

So you are saying that doesnt work as well as some claim? My experience with the inlet hat (assuming its a slight restriction) would support the 'flattening out the boost' theory but I have a feeling its more to do with the blower just running out of steam up top then the restriction of the filter/hat.

andereck

No, I'm not saying that doesn't work. I'm just saying its not a free lunch up top. What I'm saying is that the X psi delivered under restriction up top is going to be hotter than the X psi delivered at a lower rpm. That's all.

Now how much hotter? I don't have data on that. Its something I would be willing to experiment with after I get some other issues settled out.

kp

iTrader: (34)

Gotcha, I was under the impression that the less air to compress at high rpm with a restrictor = less heat. But it makes sense about the air running itself over. When I put the F1A on I may fool around with some restrctiction to see what happens, I may try running it this weekend..

kwiksilverz

Wow, this got interesting . Lots of valid points. I think based on the luck that many have had doing it, that the temp increase apparently isn't enough to hurt. I think it is also that a lot of us are running Alky injection, so the temps probably aren't a big issue to us.

Once I get my car back together, I'm going to get some tuning done and I'll do some back to back testing with one pulley at 12 psi and then the smaller pulley and restrictor. I have a feeling that the peak HP will be very close, regardless of parasitic loss and heat from the blower, but the mid range gains will be well worth any trade off there may be.

I have to admit, I am not into the "math" side of things, I did have an interest in engineering years ago, but saw first hand that just because it looks perfect in formula- it doesn't mean that the "wrong" way won't work better in practice. Since then, I have just gone with common sense and experience and it has worked well for me to this point . Thanks for all the input guys!
Joe

kwiksilverz

If you wanted to call ECS, they have the restrictors in stock- though, it isn't a difficult piece to make either.
Joe

andereck

Thanks for asking an interesting question kwiksilverz.

kp

iTrader: (34)

I can make something up in a few minutes, my problem these days is keeping the front wheels on the ground for the first 100' or so. I'm trying to kill some bottom end and put it up top

Brady

iTrader: (3)

so you need a wastegate to dump boost down low... here we go again

andereck

Naw, he just need a good timing controller.

Brady

iTrader: (3)

True, true.. we kicked *** this year using ignition timing vs. elapsed time via the nitrous controller in the FAST. It worked really good on all but the very worst tracks..

ZDOG

iTrader: (13)

so let me get this straight.....lets say you pulley for 10 psi for 6200rpm. car makes 560rwhp. linear increase in the graph 420lbs of torque at 4000 rpms.

now you pulley for 14 psi for 6200 rpms but restrict it or bleed of 4 psi so again your at 10 psi at 6200rpm. would you make 560rwhp again or not? i know the 420 lbs of toque should be lower in the rpm range now. or are you saying because the blower is spinning faster creating more heat and causing more drag that at 6200 rpm you will only make 512.4 rwhp. for the 14 psi you turned down to 10?

even if above is true. depending on the changes to the area under the curve and the gains sooner and lower in the rpm range as far as the strip is concerned you may actually gain et and mph if you have a decent average increase with the sacrafice at peak?

"the numbers are fictional and used strictly for comparison purposes only. no warranties or guarantees implied, rules and regulations subject to change without notice."

kp

iTrader: (34)

I just need to bump the timing down a little down low or drop the 2 step RPM a little, didnt want to fool with it last time out since I am swapping blowers so why spend any tme on it

Yhe BS3 has timers to control a PWM boost controller solenoid (turbo or maybe a WG on a blower) but no timing adjustments vs time..

engineermike

No, it would make less.

engineermike

I urge you to make at least 1 dyno pull with the smaller pulley and no restrictor.

Mike

kwiksilverz

I would- BUT- I am already at 12 psi on an LS2!!! I don't want to push more than that. Even though it is on the top end, it stll is a lot of boost for a stock 11:1 shortblock. Hence the reason for wanting to do a restrictor or gate on it.

No doubt it will make more peak power without the restrictor, but the "under the curve" power will more than likely be the same with or without, if not- close.

I'm not going to have my car back together until the nice weather hits, so it's going to be a while .
Joe

engineermike

I promise you that "under the curve" power will be much more without the restrictor. Adding a restriction reduces boost and power more up top than in the middle, but helps nowhere unless the blower is near choke.