Ohio mile

[one2dmax]

I need to get my other computer turned on and see what the dyno readings show for speed vs the RPM's we test to. The speed is measure on the dyno drum and not the speed shown on the bike.

 

[srk468]

Yeah, but he is saying 143 IN 4th GEAR. My original question was if the dif is geared high enough to do 150. That was based on the fact that the 3 maxs I have had seemed to spinning a LOT of rpm at 130. Everything that has been brought up here would tend to support that if you want to do 150 on a max, you need a real big rear tire or a venture dif.

Makes me wonder if the dif is the same as it was in '85. I have never heard of any differences. My '85 was dead stock- I didn't even change the air filter. Back in those days, I weighed 127 lbs. I could keep that bike full open for 10 miles and it never got over an indicated 130.

I guess there is the very real possibility that that spedo was way off and I was really going much faster.

I can tell you that riding that bike wide open for 10 miles was much more exciting then driving my suzy a lot faster on the same strip. The max was very unstable and my vision was actually blurred. The Suzy was no problem because I could fit in a larger front sprocket and it had gonzo more power. Remember the suzy street bike I had was a very highly moded race motor with a plate on it

Does anyone have a spedo known to be accurate and after market tach (or better a gps and accurate tach)

If I get 6600 rpm at 100mph that would be 66 rpm per 1 mph. So 9900 at 150 mph... Right?

The 143mph was in 5'th gear balls out but like I said the shiftlight wasn't on so I was below 9300rpm, if I had to guess probably about 9000rpm give or take. I am heavy and broad shouldered though so I do catch some decent air even tucked so your results may vary. I think with a lighter rider and a beefed up engine that'd pull 5'th gear to say 9600-9800rpm you'd hit well over 150mph but a pipe and jet kit (what I had at the time) isn't gonna do it. I'm going to eventually be looking for a venture diff for mine anyway I think, with nitrous on that 1500 I'm gonna be trapping around the 150mph area probably so I need to start thinking ahead, plus it should make it less wheelie happy cause if you bring the 80hp shot in too fast right now it'll stand up in a hurry and that's with a 300lb guy with his tits on the tank so I'll have to develop my skills a lot when I start spraying the big engine. I went 132.26mph in the 1/4 mile in fourth (air shifter won't hit 5'th on juice, can't figure out why) and shift light was on at the 1000' mark but wasn't on my 10,000rpm limiter yet but had to be damn close, if I could get 5'th I'd have went 134-136 I think but doubt ET would've changed much.

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[srk468]

I didnt even see Scotts post, so there you have it, a built Vmax around 143 mph......

All I had then was a Morley jet kit and a Kerker with a comp baffle. The only thing I did since then was pull the heads and do very light cleanup on the ports and had them milled .020" and went to ARP studs and Cometic head gaskets so I picked up a little compression but on such a small bore mine is maybe 10.6-10.7 vs the stock 10.5 and I have no idea what the head porting did. I went 120.7mph on motor this year but my friend Kevin (weighed 221lbs without leathers) went 123.7mph on the one pass he made with a decent headwind so with more time I'm sure he could have went well over 124mph on it so its not slow but doesn't set the world on fire either lol

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[customizedcreationz]

I ll have to pull my slips. I have this pass at 122 mph at the top of 4th gear. I ve seen 145 mph on my speedo and could have kept climbing, but it was taking years to get there. Honestly I still think top speed on a Vmax is maybe 145 mph tops and it would take you miles to get it. There is just no areodynamics involved.

Craig if you calculate out rpm vs mph, then you have to figure in rolling resistance and wind drag increases as speed goes up. Which increase at tremendous amounts in short amounts of speed and time.

Even with a smaller Venture Diff, I don't think you would pull any more mph. In fact you might actually go slower top speed because you wouldnt have the same rpm pull. Just dropping your gear ratio as low as you can go isn't going to necessarily give you more mph. Its ALOT of calculations to get the proper math on it.

https://www.youtube.com/watch?v=BFl5NborKCk

https://www.youtube.com/watch?v=4qXJIdeQEuU

 

[customizedcreationz]

And guys 145 mph is FLYING!

 

[Tex85]

You can definitely pull 145 on a Vmax. I have had my speedo push the 150 mark before common sense kicked in and I slowed my ass down. However you will not get there on accident like you can from time to time on different sport bikes.

My speedo is stock so no guarantee my actual speed was actually that high. This was not at a track and I didn't get pulled over (basically no one verifying it).

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[srk468]

Even with a smaller Venture Diff, I don't think you would pull any more mph. In fact you might actually go slower top speed because you wouldnt have the same rpm pull. Just dropping your gear ratio as low as you can go isn't going to necessarily give you more mph. Its ALOT of calculations to get the proper math on it.

Perfectly said, it would pull a higher mph if you had the horsepower to pull that gear but a stock bike or a bike with just a pipe and jet kit doesn't have the balls to do it.



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[one2dmax]

HP has no relation to the top speed achievable in relation to engine RPM. The only variance that can affect that would be clutch and or tire slip (which takes a shit ton more HP then we make with this bike). The top speed is a direct factor of rpm, tire diameter (which grows at speed), transmission gearing, worm drive gearing, and final drive gearing. This would be the potential. Of course wind resistance, rolling resistance, hp, torque, weight, and other misc affect what you will be able to get before you run out of power (not necessarily rpm).

Our overdrive trans has the potential of well over 200mph (dyno proven but had to over rev the engine slightly). You will actually get less top speed on stock motored bikes in actual street riding conditions because the wind resistance overcomes the HP that the engine is able to churn out. So, the engine is no where near redline but I just can't accelerate anymore.

According to the "math" the potential top speed for a stock trans, stock tire, stock diff bike is 154 @ 9500 RPM. With 190/50-17, stock diff and stock trans is 142. This is not including any tire diameter change which would raise top speed. Top speed for our overdrive gear would be 191 with stock diff and stock tire. Adding a venture diff would add 10% in theory and according to the "math" (calculator I made) it does show 212 as the new top speed.

I have been unable to see what MPH this would be on the dyno as all the DJ dyno's we've tested do not read past 200mph. In fact they lowered the reading down with a new software update a few years back. We (and the dyno operator) were shocked when the dyno basically turned all red and started flashing all kinds of warnings when we broke the 200mph barrier. They didn't know it would do that since no one had ever done that much MPH on the dyno before.

I did get a few dyno files to open up and made a quick chart. Look at the widely varying HP outputs but note that many of the MPH outputs were similar. Even some of the lower HP bikes ran higher MPH's. This was mostly due to when the operator shut off the run (and the various size tires the bikes had).