GM HighTech Writeup on Procharger/Wastegate setups
07-09-2013, 08:22 AM
#21
your not going to make less power. look at it this way..
you have a stock shortblock and a D1 will make more power than your stock 347 can handle. say it made 550rwhp at 8psi. that means in mid rpm your making more along the lines of 4psi. if u add a wastegate, you can pulley the D1 down where it would normally make 15+psi on that motor, but have the wastegate open at 8psi. itll hold 8psi to redline. your still going to make that 550rwhp, but your under the curver power will increase because the blower is pulleyd down bringing the boost on much faster in the mid rpm range. make sense?
you have a stock shortblock and a D1 will make more power than your stock 347 can handle. say it made 550rwhp at 8psi. that means in mid rpm your making more along the lines of 4psi. if u add a wastegate, you can pulley the D1 down where it would normally make 15+psi on that motor, but have the wastegate open at 8psi. itll hold 8psi to redline. your still going to make that 550rwhp, but your under the curver power will increase because the blower is pulleyd down bringing the boost on much faster in the mid rpm range. make sense?
Again, it just doesn't make sense to me to decrease your overall horsepower with it. People need to stop focusing on peak boost pressure and focus on how much boost at peak torque.
Take a setup with the wastegate and do one pull with it opening at a specific psi, then make another pull without it opening at all. Look at the graphs and see which one you want to run. I would argue that 99 out of 100 people would take the one that didn't bleed off boost.
07-09-2013, 09:06 AM
#22
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You are going to make less power. What kills a motor is too much peak torque. Most motors blow at peak torque, that's where my motor let go, right around 4600rpm in 3rd gear. Releasing the boost pressure above peak torque isn't of any benefit to engine longevity. Think about it, how come you can run it leaner, and with more timing once you get past peak torque? Bleeding off boost at that point is just wasting power, you might as well set your limiter to 5500rpm.
Again, it just doesn't make sense to me to decrease your overall horsepower with it. People need to stop focusing on peak boost pressure and focus on how much boost at peak torque.
Take a setup with the wastegate and do one pull with it opening at a specific psi, then make another pull without it opening at all. Look at the graphs and see which one you want to run. I would argue that 99 out of 100 people would take the one that didn't bleed off boost.
Again, it just doesn't make sense to me to decrease your overall horsepower with it. People need to stop focusing on peak boost pressure and focus on how much boost at peak torque.
Take a setup with the wastegate and do one pull with it opening at a specific psi, then make another pull without it opening at all. Look at the graphs and see which one you want to run. I would argue that 99 out of 100 people would take the one that didn't bleed off boost.
case in point if you only feel safe running a max psi on your motor of 10psi so your only running a pulley that will allow you to max at 8 psi, you may only be seeing 3 psi at 3000 because the psi curve is linear. now if you can pulley it down (smaller pulley) to say a 14 psi pulley , you can ADD a wastegate to the COLD piping to release any pressure exceeding 10psi.
NOW you've gained 2 psi at peak hp and you're probably making 7 psi at 3000 vs 3psi and that will result more power across the band but more so earlier were you were hindered because of the linear boost curve,,,,,,, get it?
07-09-2013, 10:19 AM
#23
You're looking at it wrong. You're NOT decreasing hp , if you'll read the article you're raising the the peak hp but by only a 20 or so hp , but your gaining 100hp down low where before you had no boost because you were limited to the final boost psi threshold.
case in point if you only feel safe running a max psi on your motor of 10psi so your only running a pulley that will allow you to max at 8 psi, you may only be seeing 3 psi at 3000 because the psi curve is linear. now if you can pulley it down (smaller pulley) to say a 14 psi pulley , you can ADD a wastegate to the COLD piping to release any pressure exceeding 10psi.
NOW you've gained 2 psi at peak hp and you're probably making 7 psi at 3000 vs 3psi and that will result more power across the band but more so earlier were you were hindered because of the linear boost curve,,,,,,, get it?
case in point if you only feel safe running a max psi on your motor of 10psi so your only running a pulley that will allow you to max at 8 psi, you may only be seeing 3 psi at 3000 because the psi curve is linear. now if you can pulley it down (smaller pulley) to say a 14 psi pulley , you can ADD a wastegate to the COLD piping to release any pressure exceeding 10psi.
NOW you've gained 2 psi at peak hp and you're probably making 7 psi at 3000 vs 3psi and that will result more power across the band but more so earlier were you were hindered because of the linear boost curve,,,,,,, get it?
No, I am looking at it correctly. Adding just a wastegate doesn't add more torque, adding a smaller pulley adds more torque due to spinning the blower faster.
Max boost is NOT the problem, it's MAX TORQUE THAT IS THE PROBLEM. Torque is cylinder pressure, and cylinder pressure is what causes knock and broken parts. Once you get past max cylinder pressure, you can add more boost, timing, raise air/fuel etc.
Someone has yet to explain to me why keeping the boost psi the same at a certain point is 'safer'.
07-09-2013, 10:36 AM
#24
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No, I am looking at it correctly. Adding just a wastegate doesn't add more torque, adding a smaller pulley adds more torque due to spinning the blower faster.
Max boost is NOT the problem, it's MAX TORQUE THAT IS THE PROBLEM. Torque is cylinder pressure, and cylinder pressure is what causes knock and broken parts. Once you get past max cylinder pressure, you can add more boost, timing, raise air/fuel etc.
Someone has yet to explain to me why keeping the boost psi the same at a certain point is 'safer'.
Max boost is NOT the problem, it's MAX TORQUE THAT IS THE PROBLEM. Torque is cylinder pressure, and cylinder pressure is what causes knock and broken parts. Once you get past max cylinder pressure, you can add more boost, timing, raise air/fuel etc.
Someone has yet to explain to me why keeping the boost psi the same at a certain point is 'safer'.
Well i would use my car as an example but i cant because im turbocharged,
I CHOOSEto only run 17 psi on my car but guess what, I hit 17 psi at 2800 and i hold that ALL THE WAY to peak hp.
if i was to put a S/C on my car tomorrow and Pulley it to get the desired 17 psi.......... id only make 5 psi at 2800 soooooooo how is that better?
and are you trying to say that if i put a smaller pulley on it and wastegate the excess pressure to not exceed 17 psi id somehow blow my motor from the massive amount of torque (less then with the turbo) id make at 4,000 rpm with probably 5 less psi then i had before? i don't get it?
07-09-2013, 11:54 AM
#26
So you want more low end torque/boost, then put on a smaller pulley and get it into the efficient range of the blower.
My point is, there is no benefit to dumping the extra boost once you go past peak torque. They are trying to make it seem like running the smallest pulley, and making gobs of torque is going to be safe because you blow off the excess boost after that.
What would you rather have, a car that makes 600ft/lbs of torque and 600rwhp, or a car that makes 600ft/lbs of torque, but carries the torque curve higher and makes 675rwhp?
STOP looking at just boost pressure curves. Look at the torque curve. Why would you want the torque curve to plummit when the wastegate opens? Honestly, I'd rather have the boost come in progressive than instant since it's easier on the drivetrain, tires, and motor.
My point is, there is no benefit to dumping the extra boost once you go past peak torque. They are trying to make it seem like running the smallest pulley, and making gobs of torque is going to be safe because you blow off the excess boost after that.
What would you rather have, a car that makes 600ft/lbs of torque and 600rwhp, or a car that makes 600ft/lbs of torque, but carries the torque curve higher and makes 675rwhp?
STOP looking at just boost pressure curves. Look at the torque curve. Why would you want the torque curve to plummit when the wastegate opens? Honestly, I'd rather have the boost come in progressive than instant since it's easier on the drivetrain, tires, and motor.
07-09-2013, 12:13 PM
#27
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So you want more low end torque/boost, then put on a smaller pulley and get it into the efficient range of the blower.
My point is, there is no benefit to dumping the extra boost once you go past peak torque. They are trying to make it seem like running the smallest pulley, and making gobs of torque is going to be safe because you blow off the excess boost after that.
What would you rather have, a car that makes 600ft/lbs of torque and 600rwhp, or a car that makes 600ft/lbs of torque, but carries the torque curve higher and makes 675rwhp?
STOP looking at just boost pressure curves. Look at the torque curve. Why would you want the torque curve to plummit when the wastegate opens? Honestly, I'd rather have the boost come in progressive than instant since it's easier on the drivetrain, tires, and motor.
My point is, there is no benefit to dumping the extra boost once you go past peak torque. They are trying to make it seem like running the smallest pulley, and making gobs of torque is going to be safe because you blow off the excess boost after that.
What would you rather have, a car that makes 600ft/lbs of torque and 600rwhp, or a car that makes 600ft/lbs of torque, but carries the torque curve higher and makes 675rwhp?
STOP looking at just boost pressure curves. Look at the torque curve. Why would you want the torque curve to plummit when the wastegate opens? Honestly, I'd rather have the boost come in progressive than instant since it's easier on the drivetrain, tires, and motor.
07-09-2013, 05:36 PM
#29
I still have yet to hear why it's a bad thing to have the boost continue to increase past torque peak....
Do we not put in bigger cams in order to help carry power higher through the rpm range?
The only reason to blow off excess boost is if you're fuel system isn't adequite to support the higher horsepower, and then the wastegate is a bandaid fix for not having adequite fuel supply.
Seriously, can someone explain why it's a bad thing to have the boost continue to rise through the rpm range. Maybe I'm missing something. How many threads do we see in here with people posting dyno sheets showing issues with the power dropping off above x,xxx rpm and everyone chimes in with plugs, plug gap, wires, injectors, coils, boost leak, belt slip, so why would you intentionally drop of the power by venting boost above a certain amount?
Do we not put in bigger cams in order to help carry power higher through the rpm range?
The only reason to blow off excess boost is if you're fuel system isn't adequite to support the higher horsepower, and then the wastegate is a bandaid fix for not having adequite fuel supply.
Seriously, can someone explain why it's a bad thing to have the boost continue to rise through the rpm range. Maybe I'm missing something. How many threads do we see in here with people posting dyno sheets showing issues with the power dropping off above x,xxx rpm and everyone chimes in with plugs, plug gap, wires, injectors, coils, boost leak, belt slip, so why would you intentionally drop of the power by venting boost above a certain amount?
Last edited by The Alchemist; 07-09-2013 at 05:44 PM.
07-09-2013, 06:13 PM
#30
its no different than a turbo reaching full boost at 2500rpm and the wastegate limiting the boost all the way through the rpm range to redline. they make better power/torque under the curve than a centri. wategating a centri makes it "spool," if u will, more like a turbo ie bringing the boost in faster giving you more power and torque through the midrange where centris lack.
07-09-2013, 06:24 PM
#31
07-09-2013, 06:25 PM
#32
its no different than a turbo reaching full boost at 2500rpm and the wastegate limiting the boost all the way through the rpm range to redline. they make better power/torque under the curve than a centri. wategating a centri makes it "spool," if u will, more like a turbo ie bringing the boost in faster giving you more power and torque through the midrange where centris lack.
07-09-2013, 06:55 PM
#33
Seriously, we're going back to the argument of it's safer? I think this is funny.
To reach max boost by 2500 rpm, you've got to spin it to max rpm to get max cfm out of the blower. If you do that, and get max boost at a low rpm like that, you might as well move your rev limiter down to 4000rpm as well. Unlike a turbo, centri blowers can't spin to unlimited rpms. Overspin your blower long enough, and wait till you no longer make boost because you've trashed it.
To reach max boost by 2500 rpm, you've got to spin it to max rpm to get max cfm out of the blower. If you do that, and get max boost at a low rpm like that, you might as well move your rev limiter down to 4000rpm as well. Unlike a turbo, centri blowers can't spin to unlimited rpms. Overspin your blower long enough, and wait till you no longer make boost because you've trashed it.
07-09-2013, 07:02 PM
#34
Oh, and I said that back in post #23 that running more boost at peak torque is what causes failures. Peak torque is peak cylinder pressure, hence why you pull timing, and add fuel in that area.
07-09-2013, 07:35 PM
#36
max boost at 2500 rpm being whatever boost ur shooting for. not max boost of what the blower can do..... theres plenty of guys running 12psi on a stock block making x amount of power with a turbo setup. say their max boost is 12psi. theyll make that 12psi at very low rpms and carry it all the way up. u take a centri blower, pulley it to where it would make...say 20psi...add a wastegate and have it pop open at 12psi. ur going to build more boost in the lower rpms just like you would with a turbo except u won't exceed 12psi at redline where you nomally max out at 20 because of the wastegate. safer? no, but its no different then going turbo. i dont know what ur not understanding. its not gonna max impellar speed of the centri. and this method only really works on an engine that can't max out whatever blower your running. like urs for instance, u have a forged setup and could probably max that D1 out with no problem there for you would not need this. u could throw an f1x on (just for examples sake) and set ur boost controller/wastegate at 18psi and pulley the **** out of that f1x and make some damn good under the curve numbers.
07-09-2013, 08:13 PM
#38
It's obvious that we're not on the same page, and maybe it's because I'm missing something, whatever. I didn't realize I had received help from you or asked you for help, again, maybe I did, but I don't remember. In the past I've asked questions of multiple people, some I agree with, some I disagree with, and ultimately, I have to make my own decisions. I built my own motor, tune it myself, so if it pops, it's on me. I learn what I did wrong, and figure out how to avoid that in the future.
Do you have more experience than me, without a doubt. I don't know your background, and even if I did, I'd still question you. That's how you learn.
max boost at 2500 rpm being whatever boost ur shooting for. not max boost of what the blower can do..... theres plenty of guys running 12psi on a stock block making x amount of power with a turbo setup. say their max boost is 12psi. theyll make that 12psi at very low rpms and carry it all the way up. u take a centri blower, pulley it to where it would make...say 20psi...add a wastegate and have it pop open at 12psi. ur going to build more boost in the lower rpms just like you would with a turbo except u won't exceed 12psi at redline where you nomally max out at 20 because of the wastegate. safer? no, but its no different then going turbo. i dont know what ur not understanding. its not gonna max impellar speed of the centri. and this method only really works on an engine that can't max out whatever blower your running. like urs for instance, u have a forged setup and could probably max that D1 out with no problem there for you would not need this. u could throw an f1x on (just for examples sake) and set ur boost controller/wastegate at 18psi and pulley the **** out of that f1x and make some damn good under the curve numbers.
07-09-2013, 09:43 PM
#40
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Lol why is this such a heated debate with you alchemist? Ok so my d1 has 3.4 pulley and 7.65 crank pulley I have it making 11psi at "peak" it carries 10-11lbs from 4000rpm to redline. I have stock bottom end. So alchemist should I take off the wastegate and run it without it because its already making all that boost at max tq? Lol I love the extra tq I now have. Feels much better than it did without it.