The more I read, the more questions come up.

Would someone please tell us at what RPM will an internally stock TC96 motor starts coming apart?

Everyone talks about the 6200 RPM number, but why? Even the SERT software defaults to 6200 for the base calibration I'm using.

All of the charts and graphs I've been finding indicate that the HP line weenies-out or is not recorded beyond 5500 RPM. Even at 5500 RPM, the line is as flat as the EKG on Elvis Presley. (OK, bad analogy. I apologize.) This observation includes graphs for stock mechanicals as well as some of the graphs for Stage II mods.

Would I be too conservative in setting a 5800 limit on the revs into the SERT on my internally stock motor? Why strees the limits of the motor if it's not going to produce any more power - If the pump ain't drawing more water, cranking harder will just get you more tired and maybe break the pump.

BTW, just last year I really did see Elvis at a Taco Bell in Toledo...

As always,'thankyou, thank you very much'the feed back.

 

If getting the maximum performance out of an engine is your interest, your objective is to average the most HP in every gear. This means that you shift somewhere past the peak HP RPMso that when the RPM drops, you are at the same power level before the peak HP RPM. Now this is in theory and assumes that this area of yourHPcurve is symetric, but hopefully you get the theory. This is why we want the Rev limit, and hopefully red line at a higher RPM then the peak HP RPM. This is also one reason that vehicles can out perform many higher HP vehicles that have more HP, it's how much HP we can average, not how much we can peak. An engine that peaks at its rev limit is not as quick as the HP number would indicate it should be.

At a given MPH, the max rear wheel torqueoccurs when we pick a gear that places the engine at its Max HP RPM due to a thing we call torque multiplication from the transmission, gear ratios and wheel diameter.

 

Good post....thats funny,

I had the privilege to take a B motor on the dyno about 3 or 4 years ago and try to blow it up....no not crazy, it was for data. I ran the bike to 7000~7500 rpm several times over and it held together which was very surprising to me. (I won't get into the data and findings at this time)
You are right when you say a street able motor will not make power after 5500~6200, depending on the valve springs and breathing capabilities, so why in the world do people want the rev limiter set at 6500 rpms. A stock motor and most mild builds will peter out at 5500~5800 right where Harley set the rev limiter in the stock ECM.

Hope this helps and tell Elvis hello the next time you see him.

Doc

 

Doc, thanks to both you and Geargrinder for the replies.

I'm not so sure I'd like to have my precious parts so close to all of that hot metal when 7K RPMs is hit!

Hey, there's an opportunity for a new product - a Kevlar jock cup for hot rod Harley drivers. Hmmmm, maybe J & P will want to market it in their catalog...

Seriously, I know the b-motor is a little better balanced than the one in the FLH series, but if a b could make several passes at 7.5k then I should think the FLH should hold together at 6K.

Thanks.

 

Ironically, your post ties in with my currentproject. I'm in the process of freshening up my engine and I want to improve on my power band. The issue is, currently my combo produces its peak HP at my self imposed redline of 6600 RPM. This means that I am not optimising the performance of theengine because I can't average close to this 160 HP because I can't use the down slope of the HPcurve. I am going from a .625 lift cam to a .570 lift cam with less duration etc hoping tomake peak HP around 5800 to 6000 RPM. This way if I shift at around 6500 Ishould be able to average moreHP even though my peak HP should decrease, but making the bike quicker.Iprobably will lose 10-15 peak HP butevery aspect of its performance shouldimprove. I feel pretty confortable shiftingat 6500 RPM because my additional cubic inches came from bore only, not a stroker,crank pinhas been welded and have a valve train that should handle it, at least it always has for the past 35000 miles.

We call engines that produce their peak power at theirredline "dyno queens" because they cannot performclose towhat their HP numbers indicate that they should.