m21sniper

"NOTHING tells us that with a 500ftlb max torque engine that we have to have it be at max torque at 5250rpm. this is where you are confused."

Except the formula used for determining HP from torque.

You win....we're not getting anywhere here.

PS, the dyno numbers you posted are not of a balanced engine(they're of an almost balanced engine). Hence nothing special going on at 5252rpm.....oh, nevermind.

mark kibort

Hey, dont be like that!
You have shown some passion of showing your point, and i think for some reason, we got our lines crossed, but in one main area i think you are wrong. That being that 5252 has some significance BESIDES how to calculate HP from torque and speed or torque from HP at any respective speed.(RPM)

I show you a BALANCED engine, and you say its not balanced enough??? COMMON!!!!!!! 322 vs 319 is not balanced??????? first of all, the balance is meaningless, as if you use any other numbers, the graphs may not even intersect. we dont have to beat that one. BUT, so what is the problem with my balanced motor graph, and what did you expect to see at 5250 rpm????max torque?????? probably never happens. at least for our engines and certainly for most chevy's too. DID you read my last post about you using 5250rpm to find the HP or torque if you have one or the other? your formula (equation ) is right, its just your application that needs some work.

If you dont agree with anything i have said, let me know.

MK

m21sniper

Bro, i just don't want to argue over minutia with someone that i like.

We've resolved what, 99% of the issues we debated?

There's an old saying in the aviation industry. "Perfect is the enemy of good enough".

LOL, i think we've reached the stage of 'good enough'.

Grab a cold brew, enjoy your win. You've debated me into bloody submission....

My only remaining question to the math gods is wrt the formula.

Precisely what does the rpm in Torque*rpm/5252 represent?

Going by the comments of the author whose description i posted, it was the rpm at which max torque occured.

Now, i agree that is seemingly not the case(i've looked at a lot of engine power profiles on the net in the last 24 hours trying to make some sense of this, and the actual engine ratings i've found do not seem to comply with the formula at all, though some come pretty close), but the rpm obviously isn't redline or max HP either.

That rpm figure(not the constant mind you, the rpm figure) MUST represent something.

So it's really irking me that it's unclear what the rpm in torque*rpm/5252 represents.

I've looked all over the net for more clear examples, and i just can't find squat. I hate ambiguity, and this formula is proving to be just that.

SharkSkin

Torque is not a measure of "Work". It is a measure of applied force. Technically, you can apply torque to something such as a bolt, a wheel, a gear, etc. but if it doesn't move then you have done no "Work"(e.g. Watts, Horsepower, etc.). In order for "Work" to be quantified, something needs to move, and that movement needs to be measured over time and factored into the equation.

In this case by factoring in RPM we can determine how much work is being done by the applied force.

Take a look at the first page returned by this search. It gives a pretty succinct summary, and from the look of it there is lots more good info turned up by that search. It also shows how the formula is derived.

HTH

Tony

402 RWHp and 375ftRWftlbs...3760 lbs and a 2.20 4spd auto.

mark kibort

Yes, it would be much better to do this in person, over those beers and we can "geek" out about this stuff.

your right, 99% we agree on as of now.

as far as the meaning of the HP = torque (ftlbs) x RPM / 5252 , it is just a simple conversion due to the units being used, nothing more. no significance of where the max torque will occure, or anything else. (except for 928 S4s, the flappy shuts near here!)
the author you quoted , just happened to find an RPM that had that max HP i suspect at that rpm. in fact, looking at some other engines recently, ive seen some with max torque right in that range. not common, but certainly possible, and certainly not due to the 5252 crossover point mathamatics.

I said from the beginning the it had no meaning. it doesnt have any, due to it only being a unit conversion factor, thats IT!! really!
go look at other hp vs torque curves using Nm for example!!! and even KWs for the power side!

MK

m21sniper

The rpm in torque*rpm/constant has to have significance(forget the cross-over, again, that's not what i'm talking about).

It's got to be a specific measure of a particular parameter, or it would be no formula at all.

I emailed an engine builder i know, i'll let you know what he says. He's a real math geek.

I understand fully what the formula is doing, and the significance of all the numbers except the part in bold.
HP =torque*rpm/5252

That rpm figure has to have a specific meaning.

For the purposes of our discussion, it's irrelevant at this point, this is just me wanting to know something i don't.....nothing more.

Anytime you're ever in the philly area Mark, lemme know....we'll get those beers, and i'll take you for a spin in the 'freak of nature' 928.

m21sniper

That's a good run Tony.

My Shark is about 3000lbs even plus driver(i weigh about 150), and ran a 13.67 best on 100 octane with 22/50 psi rear/front.

Did you play with your tire pressures or run race fuel/timing adv. on that run? If not, you've definitely got the ability to log a high 12 sec run. Probably about a 12.75.

Tony

I dropped my tire presres to 19psi for better launch traction. Helps a bit.
Im using pump gas 91 here in vegas. Im running 7-8.5 psi. No race gas. Ive found during various runs and experimenting that ive done a few months ago, that timing isnt beging retarded on the car anyway as far as i can tell. I actually added a gallon of tolune to my 10gal of 91 and my times went up. By ,my calcs i was running appx 95oct with the mixture. One day perhaps i will splurge for 10 gallons of c16 and see what happens. Perhaps if i run at the drag strip in august when temps are in the low 100s it may help. Other than that, at these boost levels im not really seeing any advantage as far as i can tell. I wish i had a good way to monitor timing during all my runs, but i dont.
How do you know where your timing is at during WOT on the drag strip run?

Right now my restrictions are 3" intake and the stock manifolds and exhaust. I am running with a RMB and a cat bypass with 2 glass packs wleded in.

BTDT...ive done 12.9. And Andy has done 12.4 with drag radials with a similar HP level .I used that time slip becasue some one mentioned a 13sec quater mile and what power it took to give it. At my weight that day it was 402rwhp. Minus some driver skill, thats what it takes with my gearing.

m21sniper

Total advance is base + dynamic.

You check it with an inductive timing light. Set the **** on the back of the light to the total timing figure you want, and then strobe the crank pulley with the engine running at about 2500rpm. Twist the distributer until it indicates 0 degrees advance/TDC.(pull and plug the vacuum advance line before you begin). On 85 and up 32v motors there's no distributer, so you need chips to play with your timing adv unless someone makes cap/rotor eccentrics, which i highly doubt.

IIRC around 50 degrees total advance is best for a stock US N/A 928(i think it was wally plumley that told me that a few years ago) on high octane pump gas(High octane here is 93 or 94, vs the 91 out in the midwest where you are, so you can't get away with quite as much advance as an east coast guy can). Start out much lower than the ultimate timing figure you want, and work the timing up in 2 degree increments(with test drives in between listening carefully for knock/ping) until you get to the advance you want, or until you hear pinging. If you hear ping, back it off 2 degrees and leave it there.

You have to be careful with a blown application though because there's significant inlet air temperature heating because of the compressing of the air through the blower. Generally on a blown app you want to retard timing incrementally as boost increases. No idea who makes timing retard systems for 928s though, mine's not blown. MSD is probably your best bet, they make some universal systems. I used an MSD timing retard system on my old T-Type turbo(18psi was the max. boost i ever ran on that motor at the track, usually 14-15 on the street), and i never had any problems with ping/knock. My cousin uses some sort of MSD timing retard on his Blown miata too, but i don't know what model number it is, or if it's a universal system.

High octane fuel is great for blown apps. because you can maintain more ign. timing advance without detonation(unless you boost ign timing high octane fuel does nothing but cost more $). Next time you go try running 100 octane Cam II fuel with a couple more degrees of initial advance(assuming that you get no knock/ping at the current setting on high octane under full boost), and stay at around 1/8th a tank. Save you some weight as opposed to running with 10 gallons in the tank(about 80 or 90 extra pounds of fuel than you need for a 1/4 mile run, that's about a .1 ET reduction right there).

What i do is run the tank almost to E before i go, then i put 10 bucks of CAM II in the tank(a little over 2 gallons) at the gas station right before the track, and bring a 5 gallon gas can and fill that with the CAM II also, then i just add about a gallon for each run to replace what i used.

I'll have to try lowering my air pressure even more next time i go. I only got in three runs the last time i took it, and i wanted to get a good idea of my average before i started messing with more changes. The difference in launch traction between the stock 36psi rear pressure and the 22 i ran is IMMENSE. Try jacking your fronts up to 50psi too, less rolling resistance, helps the ET a little.

I probably won't go again until i install my nitrous kit.

I hate waiting(baking) in the staging lanes, so i don't really enjoy the track that much. It's a lot of waiting around for a little over 40 seconds of combined fun.

PS, what did you run against for your 13 flat? I see he was well into the 11's.

m21sniper

"Torque is not a measure of "Work". It is a measure of applied force."

HP(or watts) is the measure of torque applied over time. IOW, work.

This is from your link:

" Torque and power are inescapably linked by the fact that horsepower equals torque (in ft-pounds) times RPM divided by 5250,"

RPM measured where is the question....

Is it RPM at torque peak, rpm at redline, or what?

James-man

Keep in mind that you are looking at torque CURVES and power CURVES.

You will have to come up with a better equation to match what is really happening for each unique engine - empirically, that is.

I am an idiot. That said....

If you look empirically, peak torque happens wherever in the RPM band that an engine happens to be able to twist the hardest. Peak HP RPM occurs much higher than peak torque. The two peaks essentially have nothing to do with each other.

Since Torque varies across the RPM band, you are forced to consider the torque CURVE in order to understand the Power curve mathematically. Torque needs to be represented as a function, not a constant. RPM is the variable.

I already said I am an idiot, but flame on dudes.

m21sniper

Not gonna flame anyone that's simply trying to help me to understand something, even if their 'help' isn't particularly helpful.

That's not my style.

I think mark will back me when i say i understand all the things at play, the importance of power curves, etc.

Right now all i'm interested in is WHAT does the RPM in the formula relate to specifically(ie is it the rpm that peak torque occurs, rpm that redline occurs, etc)?

I want to know just because i want to know. It must be a specific measurement of something.

My question is.....what?

The part of the formula i'm talking about is the part in bold.

hp= torque*rpm/5252.

T_MaX

Now that it seems the HP/TQ thing has been worked out , what about the N0S question (s) that started this thread?

James-man

Now that Sniper and racer boy are talking civilized-like (does Kibort have a nickname yet?) a NOS installation should be forthcoming?????