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In our 2nd season of racing, my brother Pete and I changed gearing and were methodical in upshifting at 12,500 RPM and heeding maximum 12,700 at the end of the straight in our Stohrs. I am using 15/44 gears; Pete has 16/47 which is almost exactly the same - 141 mph @ 12,500 rpm with 22" rear tires.
I was recently told that 12,700 at the end of the straight is OK, but 12,500 is too much for upshifting.
What do you guys recommend?
12.5K seems fine to me. I've run completely stock 07-08 engines almost exclusively over the past two years in my DSR, and typically shift in the 12-12.5K range, with the odd trip further north for whatever reason.
Revlimit is 13.2K, and I'd get close to that from time to time when racing hard, though not as a habit.
I am in the habit of keeping the revs down on test days - 11.5-12.0 or so, just as a measure of conservation.
FWIW, No idea if any of that ever made a difference, I never killed a stock motor.
$0.02,
-Jake
I'll back Jake up with all his comments. Pretty much the exact scenario for me. I have ten weekends on the engine. I am planning on going thru it this winter.
12700 won't blow it up but I was always told 12300 was peak hp then drops off. Check out GDs graph sounds about right: http://www.apexspeed.com/forums/showthread.php?t=45688
Ivinsea:
GDRE completed a refreshening of my 2006 GSXR F1000 engine on 8/23/2011. From his dyno chart attached the engine peaked out at 177 HP right at 12,250-12,300 RPMs.
As you can see from the chart, after 12,250-12,300 rpm's the HP performance started to drop off.
Therefore I see no reason to run the engine, (in my case), over the 12,250-12,300 RPM mark, as you really don't gain any HP. I would think pushing over this area will only lead to extra stress on critical parts of the engine. So I really wouldn't push the engine over the these limits.
The dyno chart really helped allot in determining where the real peak HP falls in and at what RPM level.
I have never blown an engine, as I have always kept the RPM's under these limits.
Hopefully this helps a little bit in your question and decision of whether or not to push the engine beyond the maximum HP levels as you just don't achieve anything by pushing the envelope.
Thread Drift:
Shifting at max hp is a bit too simplified, since the engine's output is also multiplied by gearing. Slightly less HP at, say, 12,500, multiplied by a 1.5 gear ratio (4th) versus 1.36 gear ratio (5th) will give you better acceleration. Optimum shift point is when the two curves cross - revving beyond that point is slower than shifting to the next gear at whatever lower RPM.
I'm sure there is an additional level of analysis whereby one tries to optimize shift points based shifting *into* an optimum RPM, but that's more than I know about. Perhaps the resident mad scientists will chip in on that one.
However, in terms of the original thread, I'll just re-echo what I wrote above. Works great, go enjoy your motor! :thumbsup:
-Jake
From previous threads, the geartronics does all that analysis for you on the fly and only lets you shift at the optimum point. :DQuote:
Originally Posted by JakeL
Sorry, couldn't resist.
Truth. Geartronics has a built-in eddy-current dynamometer.Quote:
Originally Posted by VehDyn
I understand that the prototype was a water brake but the water tank caused a weight issue.Quote:
Originally Posted by starkejt
It's a mercury brake on the RFRs. That's why they are so heavy.
I thought there'd be some interesting discussion on this topic....
I changed gearing to 16 front, 46 rear which will reduce RPM at end of straight from 12,700 to 12,400 at same MPH.
Additionally, there are three places on Lightning NJMP where I could use slightly longer gearing to avoid shifting or reduce RPM so this could be a better compromise.
In AMA Superbike we ran our GSXR1000's to over 14k in some situations. But occasionally rods would stretch and the pistons would hit the heads up there.
-Neel
For max acceleration in any gear, you want to look at the average HP for the rpm range (the area under the curve), which will generally mean that you shift at some rpm beyond max HP. How far beyond the max HP point will depend on how quickly the power drops off.Quote:
Originally Posted by JakeL