mark kibort

Wow, Arthur, you are now a racing santioning body expert now. Now I'm, lol'ing!

No, bzzzt, wrong again.

yes, it could be weight and thrust, but as we have discussed here, HP is a better indication than engine torque, and I think you will agree.

ever see the vipers run against the vets, in ALMS, WCGT, SCCA T1, and countless other venues?? Hmm, if you did and knew a shred of what you THINK you are talking about, you would know that displacement has nothing to do with the classing. 8.3 liter vipers run agains 5.7Liiter vets, mustangs all the time, AND at the same weight. (e.g. WCGT vipers were 3100lbs and so were the vets. wanna see the rule book? )
Today, in ALMS competition, the viper runs against the porsche GT3RS in GT2 compeition. 3.8 liter vs 8.3 liter. think the porsche at 500hp and the viper at 600hp weigh 100% more?? lol (again) and

Look, give the HP-seconds a rest. Its a unit measure of work or energy. I thought (and asked YOU the question ) if it could be used to help narrow down performance of like HP peaks, but different shape curves. Ill pose a questino with an example to make my point and ask the question . maybe, or maybe not you will be able to answer it.

To answer your question, you can use the primary variable of engine torque, but then again, in the big picture it is secondary as well, unless you are talking torque and forces at the rear wheels, correct? that is the reason sanctioning bodys for professinoal racing use dynos to determine HP, not engine torque.
a 550hp GT3RS vs a 550hp Viper. torques are almost one half the other at the engine, yet for any useable RPM range, they both can accelerate the same mass the same. Hmmm, why is that? because the rear wheel forces are the same, at any same speed. (i.e. same hp at same speed, equals same forces at same speed, all other things equal)

Let's list your error so far:
you (Arthur) said:
1. you shift the audi RS4 at max HP and less in the later gears
2. you shift the "estate 928" at 5700rpm , redline, and 5700rpm for 2,3,4shifts.
3. most sanctinoing bodies "usually" use displacement to weight ratios to class vehicles
4. HP curves used for shift points will not give max acceleration for that RPM range and associated gear ratio spacing.

all wrong and I can prove it very very easily. just say the word. Oh yeah, i already did!

You are a joker! common, who put you up to this???!!!! Hacker, its a little late/early for April fools!

Anyway, if you are serious. I have said here:
HP curves are easier to determine shift points. becuase they incorporate engine RPM.
HP-seconds was an idea that seem to make sense to incorporate the time factor in comparing HP curves, or even thrust curves. I was asking YOU if you had any other, more physics -correct, ways of incorporating that factor. maybe its not even a factor, but I still think it is. again, Ill post a couple of HP curves that begs the question.

mark kibort

So, here is the real question. here are two hypothetical curves both having the same HP, both having the same shift points (in a vacuum), but different shapes.

What we have here is two optimal shift points for the cooresponding RPM drop for a particular gear change. BUT, one has a lower rpm weighted advantage of HP vs the other which is weighted at the higher rpm side. Same area under the curve. I suppose, same average acceleration over the same rpm range, and I suppose both would end up accelerating the same over the entire range, but one would have an advantage early, the other later, ending up at the same track position if racing.

Now, i guess that is the answer.... in a vacuum. toss in aerodynamic losses, and we might have a different story, as then the net-HP curves would be much different (with a factor of a negative force going up with the square of velocity). certainly if the speeds were lower than 60mph, it would be a rounding error, but at 100mph, it would be fairly siginficant negative force.
would the advantage of the lower hp part of one curve, travel a greater distance, than the other, which would have an advantage where the forces are much greater than that advantage? maybe thats the answer right there.

at first glance the HP curve with the early advantage gains more distance than the curve with the later advantage .

GlenL

Force by the square, power by the cube.

(Rushing off this morning)

dr bob

So which motor oil displaces the most torque in a properly-designed Venturi?

--

general conclusion: Armchair internet engineer Mark is sometimes correct, but he is never wrong. Makes rational discussion tedious, at least for me.

ArthurPE

fixed


what weight? viscosity is important...

MOST set classes by displacement and weight (with a factor for forced induction)
LeMans
ALMs
F1
NASCAR
NHRA
SCCA

NASA is an exception
although they do use both
if HP > torque, Wt/HP
if T > HP, wt/(avg(HP + T)

mark kibort

Arthur,

are you serious? you just listed all the race classes, with exception of NHRA, that set classes by HP to weight and have NO regard to setting equality based on weight.

nasa is the exception??? are you nuts? DONT FORGET Grand Am Rolex prototype . Remember Arthur, 5 liter v8s, 4 liter flat 6s, etc, all running the exact same weights

what about ALMS? NO! GT2 8.3 liter viper vs porsche 3.8 liter more than double the displacement, but only 10% different in weight based on hp differences NOT displacement
GT1 5 liter maseratti , 6 liter aston martin, 5.7 liter FordGT vs 7 liter corvette - same weight
Prototype, 5 5liter diesel audi vs 4 liter honda, same weight, both 1850lbs, both 650hp. GUESS what, the 4 liter is NA and the 5 liter is turbo!


Then the rest
Nascar (all same size engine)
F1 all done by hp for different powerplants, no regard for displ vs weight
SCCA T1 all done by HP to weights
SCCA pro All done by HP to weight, and lots of off season dynoing to justify their decisions with the teams

now, the question for you of the day. Why do you think NASA with GTS averages hp and torque ONLY if the torque is numercally greater than the hp? Did you know I had a hand in setting this rule, and fixing errors with it?

ALMS protype proof about hp to weight NOT engine size:


2009 Audi R15 TDI
Dimensions and features:
Weight: 900kilo/1984.2lbs
Length/Width/Height: 4650mm/2000mm/1030mm
Power: 650 bhp / 485 KW
Torque: 1050 Nm / 774 ft lbs
BHP/Liter: 118 bhp / liter
Power to weight: 0.72 bhp / kg
Engine
Configuration: TDI 90° V 10
Location: Mid, longitudinally mounted
Displacement: 5.5 liter / 335.6 cu in
Valvetrain: 4 valves / cylinder, DOHC
Fuel feed: Direct Fuel Injection

Acura ARX-01is a Le Mans Prototype built for sports car racing, specifically in the American Le Mans Series
Dimensions:
Weight 900 kilo/1984.2 lbs
Length/Width/Height 4650mm/2000mm/1030mm
Performance features
Power 620 bhp/463 KW
BHP/Liter 155 bhp/liter
Power to weight 0.69 bhp / kg
Engine:
Configuration LM-AR7 90º V 8
Construction aluminium alloy block and head
Displacement 4 liter / 244.1 cu in
Aspiration Naturally Aspirated

mark kibort

I know, i was talking about the force going up by the square, so if the power required to accelerate needs to go up by the cube, it seems intuitively that the curve you would want, or that would have the advantage would be the one that had the greater hp in the lower rpm area of the curve because its gains were offset by less aero drag. in the higher rpm range, the now , greater HP curve is fighting a much higher proportional aero drag loss.

Its a little bit of a mind bender for me. see if you agree or can explain this one.


So, in a vacuum, both cars from the graph above would accelerate at the same average acceleration, and end up at redline at the same position. (trading off along the way). But, with aero it seesm the advantage is going to go to the vehicle with more net HP average. (or net force average). So, is the answer the curve with the lower rpm, same HP peak is better in reality at the higher vehicle speeds?

BTW, we are talking about a gear shift of a rpm drop of 70% of the rpm, post shift. (gear spacing)
To your earlier point. both of these curves are not perfect arcs, yet the shift point would be at equal HP levels for both, correct. you never explained a circumstance where this would NOT be true, even if the arc or curve was not perfect.

mark kibort

Arthur,

you are suffering from a lot of projection here. I suggest you do a little reading and find one "exception" where some sanctioning bodies actually use weight to displacement as a classing tool.

As far as F1, that you metion. better dummy up on F1 a little. I think they mention hp/weight a few times, often mention power in HP and KWs and i dont think the word "torque" was ever even mentioned. Not that it isnt important, but it has no bearing, because NOONE uses the rear wheel forces because they change with every gear you use, and engine torque is meaningless without an RPM attached to it.

http://en.wikipedia.org/wiki/Formula_One_car

"The 2006 F1 cars have a power-to-weight ratio of 1250 hp/t (0.93 kW/kg). "

Recent SCCA meeting and vote of rules for Touring cars:
"1402.c.1 (C) Production cars will be classified by the following horsepower to weight weight to horsepower
ratios only:

Dont forget porsche club, POC, PRC, All HP/weight classiing now.

The only excption that I can think of in recent years, is the old Transam use displacement back in the 80s, and drag racing. But, I would think that drag racing would then follow your suggesting of the formula that incorporates VE with their engine designs. their events are more about maximizing engines, than production based engine designs and equalization techniques.

Mongo

You're right. This **** is just downright funny.

M. Requin

I don't have a dog in this hunt, but I'm enjoying it! However, you are wrong about F1. From the regs (not wiki):

"ARTICLE 5: ENGINES AND KINETIC ENERGY RECOVERY SYSTEMS
5.1 Engine specification:
5.1.1 Only 4-stroke engines with reciprocating pistons are permitted.
5.1.2 Engine capacity must not exceed 2400 cc.
5.1.3 Crankshaft rotational speed must not exceed 18,000rpm.
5.1.4 Supercharging is forbidden.
5.1.5 All engines must have 8 cylinders arranged in a 90º “V” configuration and the normal section of each cylinder must be circular.
5.1.6 Engines must have two inlet and two exhaust valves per cylinder.
Only reciprocating poppet valves are permitted.
The sealing interface between the moving valve component and the stationary engine component must be circular."

There is much more in Article 5, but nothing about HP, all about design. And in Article 4, weight:

"ARTICLE 4: WEIGHT
4.1 Minimum weight:
The weight of the car must not be less than 620kg at all times during the Event.
If, when required for checking, a car is not already fitted with dry-weather tyres, it will be weighed on a set of dry-weather tyres selected by the FIA technical delegate."

Submitted for accuracy.

mark kibort

Yep, you are right. But when you talk to those in the know, its about power. if someone found a way to get more power out of a F1 motor, there would be a rule made against it. None the less. You dont have a dog in this fight, and it was just an example of what sanctioning bodys look at for classing cars. Does displacement to weight ratio as Arthur says, have any factor here??
why not jump on that lame before getting in the weeds about F1 rules. NO, they limit displacement and limit weight, but they dont use a displacement to weight ratio. They are both fixed in the rules.

Let me be also clear about the other classes and sanctioning bodies. most never really point out power values, but certainly limit designs and modifications that effect HP/weight ratios which are the staples. Having raced in a bunch of SCCA WC GT races, ive become pretty friendly with some of the rule makers, and often they spent a lot of time on the dyno to get the parity right. again, it had nothing to do with displacement, as they ran the gamet, of 3.6 liter all the way up to 8.3 liter. It was clearly a HP /weight goal. actually, the viper with 8.3 liters was not always the heaviest car out there. Weight to displacement ratios are not used any more. A clear example of this is in ALMS GT2 competition. 8.3 liter vs 3.8 liter. both NA, both at near the same weight.
If they used weight to displacement rules as Arthur says, then the viper would have to weigh 6000lbs for parity.

EDIT: But, to be fair. Arthur was talking about "limiting weight and displacement". in this case, it really works against his case, because then it allows the engine builders to build the best engine that will make the MOST HP! That would be classes where they use the same engine specs, like F1, NASCAR, etc. However, when the goal is about parity, the limit the HP by using rules that will equate HP/weight rations, LIKE, in SCCA WCGT, Touring, Grand am rolex prototype, GT, ALMS prototype, GT1, GT2, GT3 in europe, and even the mentioned, NASA GTS as well as porsche classes now. So, again, it becomes a matter of explaining yourself. since Arthur was bashing on using HP as a measure of performance, go and talk to the rules makers to see what they limit and why. In other words, they use HP to weight ratios to give parity for the class made up of different weight and displacement vehicles. (and usually use weight, or hp reducing measures to achieve parity)

NOW, go to the graph and give me the reasosn why the shift points would be different, and which curve would yeild a faster car and why at speeds near 100mph.

GlenL

Problem!

The same average acceleration does not give the same average velocity. Much better to accelerate hard at first!

Something else was the concept of average. Average over what? Time is what matter. Dyno graphs are all RPM. The faster you go the greater the distortion between evenly spaced RPM and evenly spaced seconds.

As for not balancing HP at the shift points, consider the "bucket" in an S4 dyno. You'd be better off revving the car harder, into lower HP, than sitting in that flat power area for a longer period of time. If the HP is a nice hump then balance on HP.

In your drawing with the hump shifted to the left the car would accelerate harder to a point and that point would be a lower top speed. At some point the car with the right-side hump (flatter torque curve!) would catch and pass the other.

ArthurPE

cookoo

so we agree, 'kiborts' (aka HP x sec = ft lb) are useless
and the only way to determine shift point for max a is torque/thrust delivered
(not in a vacuum and with a gravitational field acting on the body under study )
in other words, our intertial reference frame, not the one in la-la land or neverland

mark kibort

Interesting.

I wanted to produce those curves, but it would have been messy, plus a lot of guess work. (vs time, not rpm)


so, there are no "buckets" in reality in HP curves that i have ever seen, but yes, we have a dip in the power curve, but still even in bucket-ville. you mention its better to "rev the car harder", which means, start out above this area , in a higher hp range? anyway, even if redline was in the "bucket" for some reason, the max acceleration range would be two points of equal HP (or equal rear wheel force) post shift.

Now your last point. pretty muddy, if you ask me, but what are you talking about? sounds like you are contradicting the first part of your post. anyway, the early HP curve, would allow to faster acceleration to that point, and be further down the track. after that, its acceleration goes even further down, but still accelerating. the lfirst lower HP vehicle, now with more power past that rpm, at a further back point on the track, and in time, now is gaining, but facing increased aero drag force, and seems like it would never catch up to the first car.

mark kibort

would you give the hp-seconds a rest for the 10th time! Glen has the manners to focus on the question and do his best to discuss. You, do not.

I only bring up "vacuum" even though we have always said, "all other things being equal", because of the drag effect on a car at top speed, with two different shaped curves with the same shift points and peak HP. taking aero, I was thinking that in the end, the average velocity would be the same and in the end the two cars would tie at a distance. certainly its a valid condition to then look at the squared effects of the drag force acting on the two cars in question.

now, add some value, would you??

[QUOTE=ArthurPE;7941558]cookoo

so we agree, 'kiborts' (aka HP x sec = ft lb) are useless
and the only way to determine shift point for max a is torque/thrust delivered
(not in a vacuum and with a gravitational field acting on the body under study )
in other words, our intertial reference frame, not the one in la-la land or neverland

QUOTE]