Power, Torque, My thoughts etc

[CussCuss]

So ive been having a think the last few days from what i read on some other sites, came up with a conclusion of the power vs torque thing and had a look at my numbers. Then i found this site anyway wich explains it way better than i could. http://vettenet.org/torquehp.html

anyway so i actually went and calculated a few things from my dyno and came up with a few interesting things

- Peak torque is 289nm at the wheels or 385nm at the fly but at 3470 rpm
- But it drops off after 4500, but still 240nm @ fly at 5700rpm wich is better than stock
- if i say move the peak torque up a bit to say 5000rpm (probably a bit too high) theres 200rwhp right there or 180rwhp with peak at 4500rpm and probably some power past that aswell.
- Hopefuly an adjustable cam wheel should achieve this barring some other restrictions ie exhaust dump and maybe turbo but the turbo isnt a restriction yet as its still holding boost.

heres the figures that i came up with, i dont think i stuffed up anywhere.

RPM KW HP LBF NM NMFLY
2410 044 059 128 174 232
2820 063 084 156 211 281
3230 094 126 205 277 369
3470 105 141 213 289 385
3640 109 146 210 284 379
4050 116 155 201 273 364
4460 119 159 187 253 337
5280 105 141 140 189 252
5690 108 145 133 180 240

thoughts, comments, opinions, flames?

PS this is more of a theoretical thing, i would get the camshaft with the wheel but there just seems to be so much power there waiting.

edit : peaking at 4500 would give 180rwhp @ 4500 rpm and ~200rwhp at 5500rpm if the curve is the same?

[SpidersWeb]

I notice from looking at dyno charts, the DOHC 4G63 doesn't curve down until ~6000-6500rpm. Factory was about 5500, and some of the modified dyno charts I looked at got it to hold off until around 6500-7000 before the torque dropped significantly. Those were EVO motors though, the VR4 head has higher flow, so not sure when that dies off.

Remember the SOHC Starion head has a low VE at high rpm, which is why I opted to go down the DOHC track instead.

But anything related to allowing more flow at high rpm (cam timing, porting, higher valve lift) should contribute to providing more power higher up.

Well thats my 2c anyway.

[David]

Those figures look OK to me....

That article was pretty good also.

David.

[mrb1]

I must say I get amazed sometimes about this power torque discussion :? Torque (force) is what the engines delivers, horsepower is way of quantifing the work done over time. They are not some "seperate thing".

Serious engine developers often just use torque during development. The torque curve will follow the VE curve (friction influencing this). The VR4 head flows a lot more than the SOHC head. So it has better VE (cylinder filling) capacity. This means (all other things being equal) as the RPM increases the air flow increases and the SOHC head will start to restrict the flow (reduce the cylinder filling) before the VR4.

[toysrus]

Are you still using the standard camshaft ? How about turbo ? Remember Nxtime and Cookie both belive the camshaft needs to go once 150Kw is reached and as you can see, 150Kw was reached by 3500rpm, torque was still good at 4500rpm but you can see the restriction their and needs to be looked at. An adjustable cam wheel will allow you to move the power band up to higher rpm, but why would you do that for ? You want as much torque down low as possible so that you can then work on increasing the torque up top by improving/removing the restrictions, ie camshaft or turbo.

[SpidersWeb]

I read that article in better deoth today, and I finally understand the actual link between torque and power. Was good reading :D

[Will]

CussCuss, At a guess, I think that you will still be flow limited, so I think that if you try to move the peak torque up the rev range with the cam wheel, the greatest restriction will drop the torque back to give roughly the same peak power - that same 'wall' that we keep seeing. But don't let that discourage you from trying.

Here's another excellent explanation of torque and power. I'll refrain from calling it torque vs. power because as pointed out - you shouldn't be comparing them.

http://www.v8914.com/Horsepower-v-torque.htm

[CussCuss]

i think you have it right will, i need to find the restriction. I have nfi about what kinda flow the sohc head is capable of but its obviously higher than this.

[TOMSUN]

Has anyone bothered to put a SOHC on a flowbench???

PS: Have anyone cracked 200rwkw with an SOHC? If so what turbo and what were the other modifications?

I'd like to know as this is my challenge :D

[mrb1]

Has anyone bothered to put a SOHC on a flowbench???

Yes I would like to know these figures very much also. Say SOHC, DASH 3 valve head and VR4 all compared. Not asking for much am I (also a Magna AstronII head thrown in as well) :D

[TOMSUN]

I someone wants to donate one head of each, I can get them flowed at my TAFE... :)

[mrb1]

Has anyone bothered to put a SOHC on a flowbench???

PS: Have anyone cracked 200rwkw with an SOHC? If so what turbo and what were the other modifications?

I'd like to know as this is my challenge :D

Yes :D http://www.beyondthelimit.com.au/kon.html

[TOMSUN]

I wonder what cam specs and turbo he is running?

[quest]

flow numbers don't tell the whole story... just like peak hp on a dyno doesn't. Smaller ports will restrict at upper rpms but velocity will fill cylinders in the lower rpms, giving u good exhaust energy to spin up turbos and get u moving smartly, with a good powerband.
Starquestclub has some ported 2.6 head flow numbers and they don't come close to even a stock vr4 head. That would imply there is no comparison, even with the displacement handicap. Not the case at all.
A 60-1/to4b/stageIII/0.63 is very laggy on a vr4. A 2.6 spins it up like its a little t3, and has gone 12.4 on only 15psi (that turbo hasn't even woke yet). A vr4 wouldn't on that same turbo/boost.

[TOMSUN]

quest

It's very interesting... so many different factors to get right...

I was under the impression that on a flowbench you could get flow figures for various valve openings? If this is possible... you could take those figures to a cam grinder and say I want my maximum power to be made in this rpm range etc... hmm now I'm wondering how boost would get factored into the equation? Yes/No?? Am I way off???