Quote:
Originally posted by grega:
Yes, but it's not as significant as George believes...
Uh, yes it is.
Quote:
Originally posted by grega:
George, let's put this into a real-world perspective. While you now concur that there's no horsepower to be gained with a lighter crankshaft pulley
I have always concured with that point Greg. Visit my first post on the matter. What I got caught up in is wording. An inertial dyno will show a hp gain that in reality doesn't exist. It does so because it rotates the drum quicker.
Quote:
Originally posted by grega:
Let's hit the first point: how fast is an engine accelerating under load? I'm not going to try any calculations here, but just close your eyes and imagine how fast your tach moves when you're in third gear at 60 miles per hour.
Rather than play "let's pretend," let's use real world results, shall we? Low mass underdrive pulleys show a hp gain on an inertial dyno. No, this is not a hp gain. What it does show is the car will accelerate as if it gained hp. In the case of the SR20DE, it accelerates as if you added 7 hp to the engine. Not real hp, but faster acceleration.
We can dance around this issue all you like, but on an inertial dyno the gain is measureable and repeatable. The hp is not real, but the acceleration is. And again, it tells us the car will accelerate as if it has additional hp.
Quote:
Originally posted by grega:
So, my point is, "It's all about the distance, silly." Yes, it makes a difference, but not as much as you think it does (and not nearly as much as those chassis/tire dynos indicate.)
I'll place my bets on real instrumented testing rather than conjecture.
Quote:
Originally posted by grega:
But let's start chatting about reality: how many cars still use these large harmonic balancers
Yours for one Greg. The SR20DE uses an integral harmonic balancer. So, if the rule is made such that you must retain the harmonic balancer, the SR20DE will still have to retain the stock pulley.
Is this outrageous? Depends upon your point of view. It's certainly something that has been discussed. And if we let you change your main pulley (with integral harmonic balancer) they everyone sould be able to eliminate the harmonic balancer.
But, let's step back for a second.
Why do we even need to do this? I understand what it is supposed to accomplish, but I don't see a compelling need to allow this in IT. Again, how many people are blowing up engines because they cannot run an undersize main pulley?
I understand the technical points here. Probably better than most considering the arguments being made. Most are made from a purely personal point of view based upon their perceived impact on their car or some they are familiar with. You, in fact, assume that you will be able to run a underdrive pulley on your SR20DE, but that's not in fact the case if stock harmonic balancers are required to be retained.
If we do not look at this issue from all sides very carefully, there will be unintended consequenses and people will be bitching later. Then again, there will probably be bitching later anyway.
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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
PS: BTW, an underdrive main pulley is smaller diameter, not larger.
[This message has been edited by Geo (edited May 12, 2004).]