Peak torque too close to peak hp

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peejay
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Re: Peak torque too close to peak hp

Post by peejay »

robch wrote: Wed Mar 14, 2018 11:26 am Thanks for the reply. I would prefer the hp to be at the lowest rpm possible, this engines in a jet boat with an impeller that will never rev passed 4100 rpm @wot at this hp.
A completely flat torque curve will result in peak HP coinciding with peak torque no matter what RPM it happens at. Given that torque is mostly a function of engine displacement, you're not going to get much more at 4100 no matter what you do....
Last edited by peejay on Thu Mar 15, 2018 9:36 pm, edited 1 time in total.
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Re: Peak torque too close to peak hp

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mag2555 wrote: Thu Mar 15, 2018 6:36 am I would have liked to have seen the motor run up to 5500 to see how the cross over numbers pan out on the dyno sheet!

I don't get what you're getting at? All dyno sheets that read in English readings will "cross over" at 5252rpm whether it is some low revving piece of shit that only makes power up to 6500 or a decent engine that makes power up at 9000-10000....
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Re: Peak torque too close to peak hp

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peejay wrote: Thu Mar 15, 2018 9:34 pm
mag2555 wrote: Thu Mar 15, 2018 6:36 am I would have liked to have seen the motor run up to 5500 to see how the cross over numbers pan out on the dyno sheet!

I don't get what you're getting at? All dyno sheets that read in English readings will "cross over" at 5252rpm whether it is some low revving piece of shit that only makes power up to 6500 or a decent engine that makes power up at 9000-10000....
He said how they cross over. Not where. Everyone here knows they cross at 5252 lol.
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Re: Peak torque too close to peak hp

Post by MadBill »

What variations of 'how' can there be, the angle they cross at with particular X and Y axis scales? :?
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Re: Peak torque too close to peak hp

Post by pdq67 »

I like engines that have T and Hp still going up past 5252 rpm.

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Re: Peak torque too close to peak hp

Post by DrillDawg »

Put a DP'er on it, the secondaries are not opening fast enough and maybe not all the way.
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Re: Peak torque too close to peak hp

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MadBill wrote: Thu Mar 15, 2018 10:08 pm What variations of 'how' can there be, the angle they cross at with particular X and Y axis scales? :?
Well, for example, they could cross at 450/420

Or 410/450

Or 411/450

Or 412/450


Seems there could be many variations. And what about the numbers right before and right after that? What are they doing?


Shit, I dunno. Lol. Just being devils advocate here.
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Re: Peak torque too close to peak hp

Post by CamKing »

Until you figure out what centerlines the cam is installed at, there's no way to know which way to move.
Put a degree wheel on the engine, pull the rockers off, put an indicator on the #1 intake lifter, and find the intake centerline, by going .100" down both sides from max lift.
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Re: Peak torque too close to peak hp

Post by MadBill »

midnightbluS10 wrote: Fri Mar 16, 2018 4:12 am
MadBill wrote: Thu Mar 15, 2018 10:08 pm What variations of 'how' can there be, the angle they cross at with particular X and Y axis scales? :?
Well, for example, they could cross at 450/420

Or 410/450

Or 411/450

Or 412/450


Seems there could be many variations. And what about the numbers right before and right after that? What are they doing?


Shit, I dunno. Lol. Just being devils advocate here.
OK, you've lost me. At 5252.113122 RPM, the horsepower and lb-ft. of torque will by definition always have exactly the same numerical value. If your examples are intended as potential HP vs. TQ numbers at that RPM, they are not possible.
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Re: Peak torque too close to peak hp

Post by travis »

Maybe there is a bit of a dip in the HP curve? That cam should certainly peak another 800-ish rpm higher. I’ve used that cam numerous times and in a sbc will easily go to 6k rpms with the basic 981-16 springs.
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Re: Peak torque too close to peak hp

Post by peejay »

pdq67 wrote: Thu Mar 15, 2018 10:49 pm I like engines that have T and Hp still going up past 5252 rpm.

pdq67
5252 isn't anything magic. Power always goes up faster than torque because "power" doesn't exist, it is just a mathematical construct that allows our simple brains to quickly balance torque vs. gearing for a given road output.

Torque is what accelerates you. Torque at higher RPM accelerates you more, because it allows you to run shorter gears for the same speed, so therefore more thrust at the ground. Horsepower is just shorthand for torque and RPM.
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