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post #1 of 57 Old June 25th, 2015, 06:51 PM Thread Starter
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Random questions thread

So since the general post section has closed down, I've decided to come here for all of my question antics, to which I shall begin (I also chose the 99-04 section because this is my favorite generations):



Why race on a drag radial compared to a slick?

I've watched videos of full blown drag cars running on radials in the 8th and being able to run 4's. How is that possible? I would've thought a slick would be better.



Why go centrifugal vs roots/twin screw?

In one video I've seen, there was a Terminator Cobra and a centrifugal equipped 2v, both running almost the same HP numbers +\- 10HP difference. From a roll, at the start the Cobra pulled ahead almost a car length but then the centrifugal began pulling on him. How is that if the centri builds boost and is technically at max boost at redline? I've never really been able to find good answers for this one.



Any answers would be appreciated, and plus I thought with this thread I can get a lot of different opinions and maybe even tips on how to make X setup better than Y setup.


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post #2 of 57 Old June 25th, 2015, 10:07 PM
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Quote:
Originally Posted by SlowSixxer View Post
So since the general post section has closed down, I've decided to come here for all of my question antics, to which I shall begin (I also chose the 99-04 section because this is my favorite generations):



Why race on a drag radial compared to a slick?

I've watched videos of full blown drag cars running on radials in the 8th and being able to run 4's. How is that possible? I would've thought a slick would be better.

I'll let someone else explain this one, but I've noticed that it's pretty typical that if a car can hook on radials, it typically runs faster times than it does on slicks.


Why go centrifugal vs roots/twin screw?

In one video I've seen, there was a Terminator Cobra and a centrifugal equipped 2v, both running almost the same HP numbers +\- 10HP difference. From a roll, at the start the Cobra pulled ahead almost a car length but then the centrifugal began pulling on him. How is that if the centri builds boost and is technically at max boost at redline? I've never really been able to find good answers for this one.

Think of the centrifugal supercharger as a belt-driven turbo. The speed of the impeller on the compressor depends on the speed of the crankshaft driving it instead of exhaust gas velocity. Hence why it reaches peak boost at redline. Centrifugal superchargers are also more efficient compressors in that they typically produce less heat than positive displacement blowers, so while they aren't as responsive they tend to yield higher peak numbers. I can go into further detail if necessary.

Any answers would be appreciated, and plus I thought with this thread I can get a lot of different opinions and maybe even tips on how to make X setup better than Y setup.


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post #3 of 57 Old June 25th, 2015, 10:35 PM
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Drag radials and radial slicks both have stiffer sidewalls than bias ply slicks.

On a marginal track you'll typically go faster on the bias ply slicks as the soft sidewall lets them wind up more to soften the initial hit.

Bias sidewall slicks also recover better after they have spun, likely its the software sidewall in action again.

But on a well prepped track if its sticky enough for the drag radial or radial slick to hook you'll go quicker and have a faster reaction time as there's less energy wasted winding up the sidewall.

Mickey Thompson is claiming their latest line of "Pro Bracket" radial slicks have gotten a lot closer to bias slicks in terms of being more forgiving but still keep the performance advantage of radial slicks.

They are making the same claims on their new ET Street R line of DOT legal radials.

All that said, the consensus is still when the hook is really bad (like on the street) you are better with a bias slick or in DOT tires a bias ET Street tire or Hoosier Quick Time Pro.
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post #4 of 57 Old June 25th, 2015, 11:42 PM
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Thanks for clearing that up cal. That's news to me

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post #5 of 57 Old June 26th, 2015, 02:25 AM
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Drag radials are a radial tire that lets you run other radials on the front. You are not suppose to mix and match (but most of us do). Bias tires (often confused with slicks) have an older different design and are not supposed to be run with radials. Wrinkle slicks are a different beast entirely. The sidewalls absorb a lot of the energy of the launch and then release it making the launch much stronger and faster.

I drove bias tires for years. I ran 8.75x14 bias on my 1966 Dodge 426 Wedge. I could spin the wheels in all four gears.

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post #6 of 57 Old June 26th, 2015, 02:34 AM Thread Starter
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So on a good prepped track, instead of relying on the wrinkling of bias slicks, you can radial slicks or drag radials if I'm right. And that does make sense to me. With the bias plies wrinkling on the hit, I would assume they're "squatting" the car on the launch to help absorb the driveline shock and better transfer it to the ground. And as the second poster said, on a good prepped track, you don't necessarily need that softer launch when you can just hook and go. Correct me if I'm wrong, when it comes to tires I'm pretty foggy.

Now, about the centrifugal. I've heard the definition of it being a belt driver turbo. I know that the impeller, compressor, whatever it is, inside is crank driven and boost goes up with RPM, compressing more and more air. And of course I know they are much better at heat management than a roots/twin screw. BUT, I would think that with the instant boost you get from a PD blower and that flat torque drive, that those factors would propel you to beat the centrifugal's more linear curve. And I know that horsepower is merely a representation of torque. So again, how does steadily building boost outdo instant boost even when they're so close together HP wise?


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---------- Post added at 05:34 AM ---------- Previous post was at 05:32 AM ----------

Quote:
Originally Posted by Eagle2000GT View Post
I drove bias tires for years. I ran 8.75x14 bias on my 1966 Dodge 426 Wedge. I could spin the wheels in all four gears.

I bet that must've been fun as hell.


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post #7 of 57 Old June 26th, 2015, 02:47 AM
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Quote:
Originally Posted by SlowSixxer View Post

Now, about the centrifugal. I've heard the definition of it being a belt driver turbo. I know that the impeller, compressor, whatever it is, inside is crank driven and boost goes up with RPM, compressing more and more air. And of course I know they are much better at heat management than a roots/twin screw. BUT, I would think that with the instant boost you get from a PD blower and that flat torque drive, that those factors would propel you to beat the centrifugal's more linear curve. And I know that horsepower is merely a representation of torque. So again, how does steadily building boost outdo instant boost even when they're so close together HP wise?

In the grand scheme of things, power figures mean nothing. What maters is average power or average torque output. While the PD blower powered car has more low speed torque, that really only matters in lower gears. At the track, at WOT, when shifting your RPMs never drop low enough to make that lower end torque meaningful. This is why the centri would have an edge. It makes boost last in the rpm, but it's well within it's comfort zone while the engine is staying within the power band. On the street, from a dig, things would likely turn out different. It really comes down to the powerband. Each has it's advantages and disadvantages.

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post #8 of 57 Old June 26th, 2015, 05:11 AM Thread Starter
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Originally Posted by StangAddiction View Post
In the grand scheme of things, power figures mean nothing. What maters is average power or average torque output. While the PD blower powered car has more low speed torque, that really only matters in lower gears. At the track, at WOT, when shifting your RPMs never drop low enough to make that lower end torque meaningful. This is why the centri would have an edge. It makes boost last in the rpm, but it's well within it's comfort zone while the engine is staying within the power band. On the street, from a dig, things would likely turn out different. It really comes down to the powerband. Each has it's advantages and disadvantages.


So with what you're saying, since you're staying in the powerband, you don't really need that lower end torque. I've actually seen a video of a vortech 2v with 4.10s, making 430whp on stock internals that can throw down pretty damn good. It at least opens my eyes to different possibilities of big power out the box besides a Terminator, even though they're godly in their own way. I will say, with the Terminator, that I tend to be a bit disappointed by their acceleration at whichever power levels they may be at. I mean, I would think that a 600whp Cobra would pull like balls, which it does from a dig but after that it mellows out. I don't know, maybe it's just me.



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post #9 of 57 Old June 26th, 2015, 01:02 PM
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Not all bias tires wrinkle. Bias street tires don't and in the old days slicks didn't. When they invented slicks that did we called them Wrinkle Slicks.

The debate over centrifugal supercharger vs. roots/twin-screw is endless. Yes, the roots/twin-screw supercharger has more low end torque but that balances out around 4000 rpm and it really isn't beneficial when racing. To put that power to the ground you need a good set of tires. Put the same set of tires on a car with a centrifugal supercharger and it can launch at 4000 rpm. Here is a comparison of power curves. Both sets of numbers are STD corrected.

RPM.........KB @ 8 psi.........ProCharger
2500........165/345..............135/280 @ 1.8 ps
3000........200/355..............180/315 @ 2.6 psi
3500........240/360..............230/345 @ 3.4 ps
4000........275/362..............278/365 @ 4.2 psi
4500........310/362..............324/378 @ 5.0 psi
5000........342/360..............364/382 @ 6.1 psi
5500........366/350..............385/368 @ 7.5 psi
6000........374/327..............393/344 @ 8.9 psi

You will hear me say over and over again that boost is boost, and 9 psi is 9 psi regardless of the supercharger. The only difference is heat. Roots/twin-screws generate more heat. But here is a comparison of the power levels of of MM members that I collected several years ago.

Forum Member.........Supercharger.................HP/TQ
BlownStang.............V1 S-trim @ 9 psi.............356/371
Mell0......................P1SC @ 9 psi...................351/353
Shaun03GT..............V1 S-trim @ 9-10 psi........380/380
Eagle2000GT............P1SC @ 9 psi..................383/377
No PI No Power........KB 2.6 @ 9 psi.................389/386
ZincSavage123........V3 SI-trim @ 9 psi............378/366
Steve03GT..............V3 @ 10 psi....................398/365
PeteGT...................D1SC @ 9 psi..................413/413
Thereal2v2fear.........V2 S-trim @ 9 psi............421/427
Baker FX4...............P1SC @ 9-10 psi..............427/???
40thAnnivGT...........V1 S-trim 13-14 psi...........418/410
YellowFever............KB 2.1 @ 14 psi................422/465
SaxmanJJ................V3 @ 12 psi....................451/408
Bullitt02875.............P1SC @ 15 psi.................440/450

If was difficult comparing times between the centri and root/twin-screw cars because most of the centris run street tires or DOT drag radials and the KB cars didn't because of traction problems. Tires make a huge difference. But here is a comparison of times for those that ran similar tires.

member..............supercharger......gears....... .tires...............60 ft..........time/trap
PeteGT..............D1SC @ 9 psi.......4.10.......ET Streets.........1.65..........11.9/113
No PI No Power...KB2.6 @ 9 psi.......3.73.......ET Streets.........1.72..........11.9/115
Thereal2v2fear...V2 [email protected] psi.....3.73......Hoosier Slicks......1.60..........11.6/118
BigBoy05...........KB2.1 @ 9 psi........3.73......ET Streets..........1.78..........11.99/118
P-51GT.............KB2.1 @ 9 psi........3.73......MT Slicks............1.59..........11.5/118

Centrifugal supercharger vs. Roots/twin-screw is simply a matter of personal choice.
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post #10 of 57 Old June 26th, 2015, 04:15 PM Thread Starter
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Well thanks Eagle for shedding some more light on the centri and roots/twin screw differences. And I did have a feeling I was wrong when it came to the bias plies. I remember my auto teacher saying they were stiffer than radials so I don't know why I said they wrinkled.

When I was looking at the power curve diagram, it does make sense now how the more efficient centri will start making more power with HALF the boost of the KB at 4k.. And when it came to the times I was impressed by far.

http://youtu.be/N-kYX1HN4ik

Here was the video that I talked about in my original post, about the Cobra vs the centri GT. From the sound of the RPM's when they go, you can tell they're in the lower RPMs which would be below the curve in the case of the centri and of course explains why the Cobra pulled ahead initially. Well, now I know to pick centri over roots/twin screw lol. And the kit prices are awesome too. Thanks to both you and StangAddiction for the info. If I ever have any more random questions, you guys know where to find me.


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post #11 of 57 Old July 2nd, 2015, 03:47 AM Thread Starter
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Alright guys, here's the next set of questions I have.

Why does a roots/twin screw make instant boost when a centri builds it through the RPMs?

I know the centri has a step-up gear inside the compressor to help it start spinning faster as the RPM's rise. That'll be the reason for how fast they spin, but I still don't get how a roots is instant boost.


And when is there "too much" gear?

I've watched videos of a forum member named StopSign32v. I don't know if he's a member here, but anywho. He has only a cold air, exhaust and 4.56 gears. The car can rip with how short the gears are but I can be positive that his car is mainly an 1/8 mile car. And as we all know, these modulars in NA form need some gear to help out. But when is the gear too steep to where it accelerates fast but doesn't have enough speed per gear? How much more beneficial is a 4.10 when compared to a 3.73, or a 4.30 to a 4.10?


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post #12 of 57 Old July 2nd, 2015, 04:27 AM
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Quote:
Originally Posted by SlowSixxer View Post
Alright guys, here's the next set of questions I have.

Why does a roots/twin screw make instant boost when a centri builds it through the RPMs?

I know the centri has a step-up gear inside the compressor to help it start spinning faster as the RPM's rise. That'll be the reason for how fast they spin, but I still don't get how a roots is instant boost.


And when is there "too much" gear?

I've watched videos of a forum member named StopSign32v. I don't know if he's a member here, but anywho. He has only a cold air, exhaust and 4.56 gears. The car can rip with how short the gears are but I can be positive that his car is mainly an 1/8 mile car. And as we all know, these modulars in NA form need some gear to help out. But when is the gear too steep to where it accelerates fast but doesn't have enough speed per gear? How much more beneficial is a 4.10 when compared to a 3.73, or a 4.30 to a 4.10?


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4.56 is a good 1/8th mile gear for a n/a car and 4.10s are good for either n/a or FI. Some will disagree on that but I put up pretty good times with my 4.10a and my blower, could have been a bit faster if I would of ram a 27" tire instead of a 28". As far as to much gear its really had to say, it varies from person to person and there particular setup.


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post #13 of 57 Old July 2nd, 2015, 08:55 AM
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In the grand scheme of things, power figures mean nothing. What maters is average power or average torque output. While the PD blower powered car has more low speed torque, that really only matters in lower gears. At the track, at WOT, when shifting your RPMs never drop low enough to make that lower end torque meaningful. This is why the centri would have an edge. It makes boost last in the rpm, but it's well within it's comfort zone while the engine is staying within the power band. On the street, from a dig, things would likely turn out different. It really comes down to the powerband. Each has it's advantages and disadvantages.
I agree. Thats why many people worry more about the track than the dyno, peak torque/power give you an idea for tuning reference but it is hard to guess whether moving your power band up or down significantly either direction will hurt or help acceleration.
Will that extra 20 ft/lb at 4 grand be worth losing 10 ft/lb at 5500? that's hard to speculate.


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post #14 of 57 Old July 2nd, 2015, 11:55 AM Thread Starter
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[quote=CJackson;10700113]4.56 is a good 1/8th mile gear for a n/a car and 4.10s are good for either n/a or FI. Some will disagree on that but I put up pretty good times with my 4.10a and my blower, could have been a bit faster if I would of ram a 27" tire instead of a 28". As far as to much gear its really had to say, it varies from person to person and there particular setup.




http://youtu.be/v2koMJq-rsg

This is what I can relate to when you say 4.10s are the good all rounder. That car, for 431/390, I feel pulled pretty good. I know some people go 3.73 and say it's good but i feel it won't have enough oomph. In my head, 4.10 for 2v, 4.30 for 4v NA.



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I agree. Thats why many people worry more about the track than the dyno, peak torque/power give you an idea for tuning reference but it is hard to guess whether moving your power band up or down significantly either direction will hurt or help acceleration.

Will that extra 20 ft/lb at 4 grand be worth losing 10 ft/lb at 5500? that's hard to speculate.


True. I fee that you'd only really need the lower torque if your car can't get out of the hole fast enough, but other than that you'd need your power up top and for it to not just drop off the table when it peaks. And dyno numbers can be nice and all but like you said, how important is that gain/loss and will it make a difference? I'm sure that cars with less power than other cars could and possibly have outran higher power cars. If anyone can attest to this its be nice, some food for thought to change my opinion of "more is better."



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post #15 of 57 Old July 2nd, 2015, 04:16 PM
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Not all bias tires wrinkle. Bias street tires don't and in the old days slicks didn't. When they invented slicks that did we called them Wrinkle Slicks.

The debate over centrifugal supercharger vs. roots/twin-screw is endless. Yes, the roots/twin-screw supercharger has more low end torque but that balances out around 4000 rpm and it really isn't beneficial when racing. To put that power to the ground you need a good set of tires. Put the same set of tires on a car with a centrifugal supercharger and it can launch at 4000 rpm. Here is a comparison of power curves. Both sets of numbers are STD corrected.

RPM.........KB @ 8 psi.........ProCharger
2500........165/345..............135/280 @ 1.8 ps
3000........200/355..............180/315 @ 2.6 psi
3500........240/360..............230/345 @ 3.4 ps
4000........275/362..............278/365 @ 4.2 psi
4500........310/362..............324/378 @ 5.0 psi
5000........342/360..............364/382 @ 6.1 psi
5500........366/350..............385/368 @ 7.5 psi
6000........374/327..............393/344 @ 8.9 psi

You will hear me say over and over again that boost is boost, and 9 psi is 9 psi regardless of the supercharger. The only difference is heat. Roots/twin-screws generate more heat. But here is a comparison of the power levels of of MM members that I collected several years ago.

Forum Member.........Supercharger.................HP/TQ
BlownStang.............V1 S-trim @ 9 psi.............356/371
Mell0......................P1SC @ 9 psi...................351/353
Shaun03GT..............V1 S-trim @ 9-10 psi........380/380
Eagle2000GT............P1SC @ 9 psi..................383/377
No PI No Power........KB 2.6 @ 9 psi.................389/386
ZincSavage123........V3 SI-trim @ 9 psi............378/366
Steve03GT..............V3 @ 10 psi....................398/365
PeteGT...................D1SC @ 9 psi..................413/413
Thereal2v2fear.........V2 S-trim @ 9 psi............421/427
Baker FX4...............P1SC @ 9-10 psi..............427/???
40thAnnivGT...........V1 S-trim 13-14 psi...........418/410
YellowFever............KB 2.1 @ 14 psi................422/465
SaxmanJJ................V3 @ 12 psi....................451/408
Bullitt02875.............P1SC @ 15 psi.................440/450

If was difficult comparing times between the centri and root/twin-screw cars because most of the centris run street tires or DOT drag radials and the KB cars didn't because of traction problems. Tires make a huge difference. But here is a comparison of times for those that ran similar tires.

member..............supercharger......gears....... .tires...............60 ft..........time/trap
PeteGT..............D1SC @ 9 psi.......4.10.......ET Streets.........1.65..........11.9/113
No PI No Power...KB2.6 @ 9 psi.......3.73.......ET Streets.........1.72..........11.9/115
Thereal2v2fear...V2 [email protected] psi.....3.73......Hoosier Slicks......1.60..........11.6/118
BigBoy05...........KB2.1 @ 9 psi........3.73......ET Streets..........1.78..........11.99/118
P-51GT.............KB2.1 @ 9 psi........3.73......MT Slicks............1.59..........11.5/118

Centrifugal supercharger vs. Roots/twin-screw is simply a matter of personal choice.

As what seems to be your usual, your post is well written and provides hard data. Thank you for that.

What I think we need to keep in mind is that the data you cite, while giving a quantifiable means of comparing the HP of different cars, becomes meaningless unless the same criteria was used in the taking of the measurements.

In other words, unless the *exact same conditions* were present at each dyno run, then a valid comparison cannot be made. That is, of course, if true and correct data is being sought.

You are entirely correct when you state that 9psi is the same as 9psi, regardless of the means by which it was achieved. Where I hold that you are mistaken is in your claim that "the only difference is heat". Would not the amount of HP needed to generate those 9psi also be of critical importance?

If one blower, for instance, requires 50HP to drive, and the other 30HP, then the latter would produce 20HP more at the crank than the former.

It seems to me, that BOTH heat and efficiency are important, and *not* just heat as you state. Would you agree?

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post #16 of 57 Old July 2nd, 2015, 04:32 PM
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"It seems to me, that BOTH heat and efficiency are important, and *not* just heat as you state. Would you agree?"

Definitely. However, heat is more substantial in determining Engine efficiency
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post #17 of 57 Old July 2nd, 2015, 05:03 PM
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"It seems to me, that BOTH heat and efficiency are important, and *not* just heat as you state. Would you agree?"

Definitely. However, heat is more substantial in determining Engine efficiency
Do you have some data to offer in support of this?
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post #18 of 57 Old July 2nd, 2015, 08:11 PM
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Alright guys, here's the next set of questions I have.

Why does a roots/twin screw make instant boost when a centri builds it through the RPMs?

I know the centri has a step-up gear inside the compressor to help it start spinning faster as the RPM's rise. That'll be the reason for how fast they spin, but I still don't get how a roots is instant boost.


And when is there "too much" gear?

I've watched videos of a forum member named StopSign32v. I don't know if he's a member here, but anywho. He has only a cold air, exhaust and 4.56 gears. The car can rip with how short the gears are but I can be positive that his car is mainly an 1/8 mile car. And as we all know, these modulars in NA form need some gear to help out. But when is the gear too steep to where it accelerates fast but doesn't have enough speed per gear? How much more beneficial is a 4.10 when compared to a 3.73, or a 4.30 to a 4.10?


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Roots/twin-screw don't actually make instant boost but they do reach maximum boost around 2500 rpm. I don't really know how they maintain maximum boost without making too much. I suspect they bleed off the excess. There are tricks to make a centri come into full boost earlier. You can run a small pulley and put a boost limiter on the piping. I don't really think its worth the effort and I can only remember one MM member having ever done it. He said it actually made his car slower.

There is not such thing as a "best" gear. You need to pick right gear for your specific application. "Too much gear" or "running out of gear" are basically the same thing. They cause you to run out of rpm before reaching the finish line. I have been told that for autocross you want a gear that allows you to reach maximum rpm on the longest straight a way. For a quarter mile track you want a gear that allows you to finish without shifting into overdrive. That depends on trap speed. The more power you make the higher your trap speed.

If you are running a stock motor with a supercharger then you will most likely be running around 380-400 rwhp. That puts your trap speed in the quarter around 111-114 mph. If you are running a stock size tire then your tach will be deep in the red at the finish line with 4.10s. That combo gets you around 105 mph at 6000 rpm so to finish the race you have to push the motor somewhere around 6300 rpm. With 3.73s it will be just shy of redline. looking at the data I could not see a significant difference in trap speeds or times. Peak horsepower occurs around 5800-5900 rpm. 4.10s put you past peak horsepower. With 3.73s you have not yet reached it.

You can increase your trap speed and water down 4.10s by putting on a bigger tire and running a 28" wrinkle slick with 4.10s has a lot of advantages.

---------- Post added at 07:11 PM ---------- Previous post was at 06:54 PM ----------

Quote:
Originally Posted by 2001MineralGreyGt View Post
What I think we need to keep in mind is that the data you cite, while giving a quantifiable means of comparing the HP of different cars, becomes meaningless unless the same criteria was used in the taking of the measurements.

In other words, unless the *exact same conditions* were present at each dyno run, then a valid comparison cannot be made. That is, of course, if true and correct data is being sought.
The data is not meaningless. Before I collected that data everyone had an opinion based upon someone's else's subjective judgement and you wouldn't believe the urban myths that were floating around. And you are incorrect about not being able to compare dyno numbers. If the dyno is set up correctly and the same correction factor is used the correction factor adjusts for varying conditions. That is why I try to use the same correction when comparing numbers. The KB and the ProCharger data presented earlier were both STD corrected. Unfortunately some people screw with the settings to please their customers.

The list of members running different superchargers showing similar numbers is not that clean. Some are probably SAE corrected. Some STD corrected. And, some may be raw numbers.

ProCharger P-1SC, 9 psi, STD 396/383; Uncorrected 388/375; SAE 383/370.
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post #19 of 57 Old July 2nd, 2015, 08:29 PM
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Originally Posted by Eagle2000GT View Post

The data is not meaningless. Before I collected that data everyone had an opinion based upon someone's else's subjective judgement and you wouldn't believe the urban myths that were floating around. And you are incorrect about not being able to compare dyno numbers. If the dyno is set up correctly and the same correction factor is used the correction factor adjusts for varying conditions. That is why I try to use the same correction when comparing numbers. The KB and the ProCharger data presented earlier were both STD corrected. Unfortunately some people screw with the settings to please their customers.

The list of members running different superchargers showing similar numbers is not that clean. Some are probably SAE corrected. Some STD corrected. And, some may be raw numbers.

You write, "And you are incorrect about not being able to compare dyno numbers. *IF* the dyno is set up correctly and the same correction factor is used the correction factor adjusts for varying conditions. " (EMPHASIS MINE)

*IF*, and only *If*, I would agree. Now the question comes, "How do you know they were?"

Keep in mind, to simply respond, "Well, how do you know they were NOT?", does not support your claim. See, I am calling YOU to support a claim YOU made. For you to simply turn around and attempt to reverse the claim does not help you at all. I am questioning the veracity of comparing dyno results with other readings taken at different shops, by different people, at different times, under varying conditions. Your data is certainly helpful, but in no way is it to be taken as gospel. It gives a "ballpark" number, that is all.

Furthermore, gear ratio, tire pressure, tire position on dyno roller, vehicle weight, and MANY OTHER factors affect dyno readings! Are you absolutely sure these parameters were exactly the same in ALL of these instances?

If not, then it follows by necessity that your data is not reliable as a means to make objective determinations on the efficiency and over-all performance of different type super-chargers.

You seem to think that the "correction factor" is some magical parameter that negates all the aforementioned variables, it does not.
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post #20 of 57 Old July 2nd, 2015, 08:58 PM
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Quote:
Originally Posted by 2001MineralGreyGt View Post
You write, "And you are incorrect about not being able to compare dyno numbers. *IF* the dyno is set up correctly and the same correction factor is used the correction factor adjusts for varying conditions. " (EMPHASIS MINE)

*IF*, and only *If*, I would agree. Now the question comes, "How do you know they were?"

Keep in mind, to simply respond, "Well, how do you know they were NOT?", does not support your claim. See, I am calling YOU to support a claim YOU made. For you to simply turn around and attempt to reverse the claim does not help you at all. I am questioning the veracity of comparing dyno results with other readings taken at different shops, by different people, at different times, under varying conditions. Your data is certainly helpful, but in no way is it to be taken as gospel. It gives a "ballpark" number, that is all.

Furthermore, gear ratio, tire pressure, tire position on dyno roller, vehicle weight, and MANY OTHER factors affect dyno readings! Are you absolutely sure these parameters were exactly the same in ALL of these instances?

If not, then it follows by necessity that your data is not reliable as a means to make objective determinations on the efficiency and over-all performance of different type super-chargers.

You seem to think that the "correction factor" is some magical parameter that negates all the aforementioned variables, it does not.

I honestly do not see what you are trying to prove at this point. You are just coming across as a complete ass.

I agree that every dyno will read a little different depending on a variety of factors. I also agree that dishonest tuners can skew dyno numbers very easily to make their customers happy. SAE and STD correction factors do a VERY good job of taking a lot of these things out of the equation (besides operator dishonesty). Do you even understand the parameters that these correction factors take into account?

Track times help show a car's true characteristics. Weather, weight, traction and a few other things all play into a car's performance on the track. But using the 60ft, 1/8 times and mph, and 1/4 times and mph you can definitely work around a lot of these factors and get an idea of what the car is capable of.

Eagle has already acknowledged both of the above facts. What more are you expecting to get out of this discussion?

Yes, these things show trends. You can't look at a car's horsepower on the dyno and tell exactly what it is going to do at the track, but you can give a range of performance to expect like Eagle mentioned. The cool thing about data analysis is that if your sample size is large enough, you can begin to draw reasonable conclusions from it, which is exactly what Eagle has done.

It's very easy to sit behind a keyboard and pick someone else's work apart. Eagle has been a valued member on MM since before I was even here. He has thousands of extremely informative posts about a variety of topics and has obviously spent hours compiling data with as much detail as possible for discussions such as this. What have you contributed?


What does your dyno sheet trap?
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