Different pulleys - how much does it help?

Originally posted by MMiskoe:
Greg Amy - email off line if you are still having power steering over heating problems. Your Nissans & my Nissans run similar pumps, I don't have problems.
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That may also be due to the PS cooler. The NX2000 uses a looped line in front of the radiator. Other Nissans, such as the NX2000's brother the SE-R, use a finned PS cooler. I think that makes some difference. We never boiled our PS fluid in our ITS SE-R.


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George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com
 
Darin,

You've got to be kidding me. A 3%-5% hp gain is not that big a deal? I'm using George's 7hp number to get that, and assuming 140 - 210 hp as the range for most of ITA/ITS. There are plenty of people that would pend large amounts of $$$ to get that 3-5 percent increase in hp.

And, it doesn't really matter if 90% (your number, don't know what you based it on) of the drivers can't use it, what about the 10% that can? They're probably already running at or near the top, you just given them even more of an advantage. And in doing so, raised the bar a bit more.

And, given two ways to get to the same goal, I'll take the one that minimizes the chance for 'unintended consequences', any day, espeically when they would benefit some cars more than others.

Now, I need to call the Dr. to make an appt. I think I'm actually agreeing w/ George on this one!
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MARRS #25 ITB Rabbit GTI (sold) | MARRS #25 HProd Rabbit
SCCA 279608
 
I'm biting my lip on this one, but I want to make some facts totally clear:

- There is no horsepower increase with a reduction in rotating mass. Period. It may seem "as if" it was increasing horsepower; well, I'm spending money on racing "as if" I were rich, but I've yet to see my invitation to the New York Polo Club.

- The advantage of reducing rotating mass is the ability of the ENGINE - not necessarily the vehicle - to accelerate faster.

- Distance from the center of rotation of the reduction in rotating mass is the number one factor to the improvement in vehicle acceleration: the farther the distance from the center of rotation that the mass is removed, the more expected ENGINE acceleration one sees.

- The improvement in performance expected from lightening rotating parts in not a hard number, it's a proportional percentage of existing engine rotating mass. A lighter engine will experience greater improvements from a reduction in rotating mass. Taking 5 pounds on a Chevy big block won't even be noticed; taking the same 5 pounds off a Kawasaki Ninja engine will.

- The diameter of a heavy crankshaft pulley is relatively small, therefore the expected engine acceleration improvement is also relatively small (compared to, say, lightening a flywheel).

- The relatively lesser improvement of engine acceleration from a lightened crankshaft pulley (compared to, say, a lightened flywheel) will result in lesser performance increase in VEHICLE acceleration, subject to...

- The vehicle will accelerate faster as a result of reducing powerplant rotating mass, but only as a function of the mass and aerodynamics of the vehicle itself. A heavier, less aerodynamic vehicle will experience less performance increase from reduction of rotating mass of the powerplant.

- Aerodynamics start seriously kicking in around 45-55 mph. Once you reach that speed the advantages of lightened drivetrain components diminishes to a point of zero at top aerodynamic speed.

- Since there is no increase in horsepower or torque from lightening rotating mass, there will be zero (none, nada, zip) increase in the top speed of the car from lightened rotating components. Lightening rotating mass affects drivertrain - and, ultimately, vehicle - acceleration only. That's why you'll really see an improvement at the 60-foot mark, but less so at the 660-foot mark.

You want to settle this? Forget the cheesy chassis dyno, which measures only the drivetrain acceleration and ignores the effects of the vehicle's mass and aerodynamics. Go ask your buddies to do a before and after at the drag strip, on the quarter mile. See how it affects not only the 0-40mph times but also the time and speed at the quarter mile. I'll bet you'll see a significant performance increase from 0-40mph and at the 60-foot mark; I'll also bet you'll see very little performance increase from 40-60mph and 60-100mph, where we as road racers spend the majority of our time.

THAT would be "real world" testing.

GregA

[This message has been edited by grega (edited May 16, 2004).]
 
Originally posted by grega:
I'm biting my lip on this one, but I want to make some facts totally clear:

- There is no horsepower increase with a reduction in rotating mass. Period.
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Agreed 100%. As I've already admitted, that was a misleading statement.

HOWEVER........

Originally posted by grega:
- The advantage of reducing rotating mass is the ability of the ENGINE - not necessarily the vehicle - to accelerate faster.
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Greg, come on. All the theoretical discussion in the world won't change the results. And if the engine accelerates faster, so will the vehicle. Unless of course you have a bad clutch.
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The fact is, there are indeed acceptable engineering calculations to measure horsepower from rotating a known inertial mass. This is how the cheesy (as you put it) chassis dynos work. Interstingly enough, there are also inertial engine dynos. They don't seem to be used for automotive applications though, but on a previous research project regarding inertial dynos I came across them.

So, when you use an inertial dyno, you can be fooled into thinking that low mass components increase hp. They don't. But, they spin up the heavy drum as if they did. In other words, they accelerate it more quickly, just as the car would accelerate more quickly as if it were accelerating on pavement. It will accelerate faster just like it would if you increased hp.

This is not ricer mumbo jumbo Greg. You can tell us in theory how little affect a small diameter, low mass crank pulley can have on acceleration, but a chassis dyno gives you and answer that isn't theory.

The fact is, there are performance improvements to be had by replacing the main pulley.

Originally posted by grega:
See how it affects not only the 0-40mph times but also the time and speed at the quarter mile. I'll bet you'll see a significant performance increase from 0-40mph and at the 60-foot mark; I'll also bet you'll see very little performance increase from 40-60mph and 60-100mph, where we as road racers spend the majority of our time.
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This is a red herring. Add 7 bhp to any car and see how it affects the acceleration times at these speed ranges and you'll find the same results. Well nearly the same results since every hp mod does not increase hp linearly throughout the rev range.

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George Roffe
Houston, TX
84 944 ITS car under construction
92 ITS Sentra SE-R occasionally borrowed
http://www.nissport.com

[This message has been edited by Geo (edited May 16, 2004).]
 
<font face=\"Verdana, Arial\" size=\"2\">Add 7 bhp to any car and see how it affects the acceleration times at these speed ranges and you'll find the same results.</font>
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I'm sorry, George, but you're wrong; you've been handed a plate of bull. 7hp horsepower on an intertial driveline chassis dyno will not correlate to the same thing in the real world. Them's the facts, my friend, and that's the last thing I have to say about it.


[This message has been edited by grega (edited May 16, 2004).]
 
Well, you are both probably closer than you think.

A good discussion of what HP is could be handy right now...where's Gregg Baker when you need him? But isn't Jake an engineer too?

Anyway, aloowing the engine to spin up faster does "fool" the dyno into a higher number...and while that number may not be dead nuts accurate, it does represent a potential performance gain.

Any gain has to be attributable to something...whether it is more torque, better breating (HP), less driveline drag, or faster engine rev band acceleration.

That said, there are a lot of things spinning between the crank and the pavement, like the clutch/flywheel, trans input shaft, driveshaft(s), final drive diff, axle shafts, brake discs, wheels and so on that the gain has got to be really small.

Which is one reason the F1 guys go nuts over the weight and location of the driveline components. it all adds up ... or down, to make the car acceletate up faster, and the times drop down.

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]
 
Originally posted by lateapex911:

Which is one reason the F1 guys go nuts over the weight and location of the driveline components. it all adds up ... or down, to make the car acceletate up faster, and the times drop down.
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I have to agree.. it really is simple... The Dynojet Dyno's may not in some peoples estimation denote TRUE HP... However neither do those attached to the hub, as they are losing HP via drag from the driveline components on the way from the Flywheel.... But that isnt the real point.
The POINT of all out work on these cars is to make them accellerate faster.
It is REALLY that simple..

Now the point is... IF the pulleys allow the dynojet to "misread" that into better HP.. via faster acceleration.. then isnt that what we are all after????

Look at F1 as posted above... Look at Motorcycle racing.. make it light and it is going to be faster than the next one by default. We are not running Nevada in a Top speed run.. therefore it is sorta moot the Drag factors at high velocities... this is all about acceleration.

(I had a lot of other stuff I typed.. but got carried away with weight reduction etc.. and percieved HP etc...soo going to let it lie at this amount ROFL)

Scott Neville
SPiN Racing
86 RX-7 EP
88 RX-7 20B SP


[This message has been edited by SPiN Racing (edited May 18, 2004).]
 
Originally posted by Joe Craven:
Has anyone mentioned that the crankshaft pulley is unrestricted on rotary powered cars?
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Shhhh.

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Marty Doane
ITS RX-7 #13
CenDiv WMR
 
Originally posted by Quickshoe:
An additional 2-7 HP for everyone (but the rotary) doesn't concern me as much as someone being able to spin the motor another 400-600 rpms (numbers pulled out of my arse). Maybe it doesn't make any more power at all, but now they have the opportunity to run a little lower gear w/o hurting top end...
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Those who read between the lines might have caught it in my above post.

We can argue how much hp it gains, real or perceived. Argue whether or not that HP makes any difference on the track until we are blue in the face.

I think you will find that those in support of the rule who also think that it doesn't make any difference (going to a smaller and lighter pulley), would be totally against going to a much larger and heavier pulley even if accessory speed wasn't an issue.
 
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