Dynomation Enthusiasts?

General engine tech -- Drag Racing to Circle Track

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englertracing
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Re: Dynomation Enthusiasts?

Post by englertracing »

a jeep with 35s
do the 383.....
or better yet a 400...
RevTheory
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Re: Dynomation Enthusiasts?

Post by RevTheory »

Me on the internet: "You mark my fuggin' words, I will NOT build another gawd-forsaken 383!"

Me in my head: "Yeah, but what about a 307 block, .030 over with a 3.8 crank for a 3.905/3.8 combo with a 5.7 rod for piston speed at a lower rpm in hopes of fattening up the torque curve below it's peak?"

Me in real life: "Damn, I should just build another 383 for all the reasons posted above without jumping through a bunch of hoops."

Thanks for the graph, MadBill; I haven't seen that one before.
tt 383
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Re: Dynomation Enthusiasts?

Post by tt 383 »

If you have the 3.75 crank use it!??? Offset it .075 for 3.825 crank x 4.040 bore is 392... if the block will take .060 it's a 396.
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Re: Dynomation Enthusiasts?

Post by hoffman900 »

RevTheory wrote:Sure sounds like these programs care less about the bore/stroke combo than they care about total cubic inches. They also seem a little more generous than I would expect to see on the dyno.

I appreciate your input :)
I hesitate to do tests like this on sims as the bore area will have a direct relationship on shrouding and thus, the flow curve. You really need flowbench results from each bore size change, and plug in the corresponding data to get a more accurate picture.

Remember, GIGO.
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Re: Dynomation Enthusiasts?

Post by RevTheory »

Good point, Bob. Thanks!
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Re: Dynomation Enthusiasts?

Post by randy331 »

RevTheory wrote:Sure sounds like these programs care less about the bore/stroke combo than they care about total cubic inches.
That would hold true in the real world too. TQ production is very very cubic inch related.

I was recently part of dynoing the same cam/heads and 2 different intakes, over several days, on a 4" bore x 3.5 stroke and 4" bore x 3.875 stroke engines. They both produced the same TQ/cubes but as expected the bigger cube was at a lower rpm.

Your not gonna make up for 15 cubes with a different bore/stroke ratio or rod/stroke ratio.

Randy
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Re: Dynomation Enthusiasts?

Post by mk e »

randy331 wrote:
RevTheory wrote:Sure sounds like these programs care less about the bore/stroke combo than they care about total cubic inches.
That would hold true in the real world too. TQ production is very very cubic inch related.
Whats that they sat....there's no replacement for displacement? :)

The Sims like dynomation5 do care about bore/stroke combinations because they care about the energy in the air flow stream at the current conditions and can help you optimize a head or cam selection for the bore/stroke you have or visa-versa optimize the bore/stroke fore the head or cam......but they can't replace Via.

They also want lots of detail to be very accurate which is why I didn't give this one a go....i just don't know enough about port dimensions and such on these engines to make guesses I would trust. I have played extensive with nore/stroke combos on engine I do have all the data for and the result is always the same...once everything is optimized TQ depends on CI and hp it TQxrpm so a shorter stroke with a higher redline makes more hp.....after EVERYTHING is optimized.
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RevTheory
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Re: Dynomation Enthusiasts?

Post by RevTheory »

randy331 wrote:
RevTheory wrote:Sure sounds like these programs care less about the bore/stroke combo than they care about total cubic inches.
That would hold true in the real world too. TQ production is very very cubic inch related.

I was recently part of dynoing the same cam/heads and 2 different intakes, over several days, on a 4" bore x 3.5 stroke and 4" bore x 3.875 stroke engines. They both produced the same TQ/cubes but as expected the bigger cube was at a lower rpm.

Your not gonna make up for 15 cubes with a different bore/stroke ratio or rod/stroke ratio.

Randy
Thanks for your input, Randy. That 15 cube deficit seems like the biggest challenge. I hope your EMC efforts are going well. I know you've played around with seat angles, have you noticed a place in total lift where the steeper seats get the upper hand? Like .650 lift from a 1.94 valve?

I may be out in the weeds here...
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Re: Dynomation Enthusiasts?

Post by randy331 »

Lets say your entering a EMC type contest with a 356 CI limit, but no factoring for cubes in the scoring. Just highest AV TQ and AV HP over specified rpm range wins.

Who would choose the 340 cube combo and give up 15 cubes for what may be a more ideal bore/stroke ratio or rod/stroke ratio ?

Lets leave the 2 options to choose between the ones rev posted to keep it from getting into a "what's best combo" discussion.

Randy
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Re: Dynomation Enthusiasts?

Post by RevTheory »

I can't see sacrificing the cubes in that scenario, Randy. But I doubt if I'd just build a 350 Chevy with the appropriate bore diameter to hit 356 without at least testing other bore/stroke combos first.
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