All talk VR.

Is an open invitation

You will never take me up on it, becuase you would rather hide behind your computer screen and spew insults and non-science. You would only show up if you could guarantee your success, and unfortunately, you can do that.

Thunderhill, Laguna, Sears, any SCCA race weekend. Offer stands

Mark

 

Look the only thing moving the car down the road is power. Power is measure of work and this means it relates the force you are pushing something with to the motion it is actually doing. Engines create power by turning the crankshaft with a certan force at a certain speed. No speed and the force becomes irrelevant for work since you are not moving anythign any where.

In the end what makes a car move is the power that goes throuhgh the rear wheels and gets transferd to the ground. Gears and multiply torque, but never create more hp. They can only lose hp through frictional loses in fact.

So power is really the only important thing.

However torque is also very important since it is base component of power. Torque x speed = power. So torque is essential as it is the force the motor can provide. If you look at everything from street engines to F1 engines you will something interesting. For normal non forced incudtion engines peak torque fits in relavivly narrow bad with displacement. Seems odd at first that a 2.4L F1 motor and a 2.4L honda motor might be similar in torque, but that is due to the size of bang you get. Per 1 crankshaft rotation there is only so much air and fuel that can be crammed in to fixed diplaced volume. Thus you get a relativly fixed torque output. However the HP levels are different since you use engien speed to counter that by giveing more torque per second. Thus more hp.

Now for any given single point the critical number is hp not torque as it is measure of how much work is is being done. Force and distance.

Now what does this mean for practical race cars.

Firstly F1 motors are fast in anychassis despite little torque. They just spin the motor so fast it gives you many many little pushes vs fewer big pushes.

The issue with torque vs hp in most race cars comes down to driveablilty. Since race cars must operate over a range of ground speeds and over range of engine speeds they rarely operate 100% at their peak power point. So the shape of the curve is critical as this determines how much power you have over the range of engine speeds you will need to operate at.

Big torque motors often have power curves that offer good power at a wide range of engine RPM. This in turn gives the car power at many different ground speeds. In racing road racing especially where you need to accelerate from various speeds you want good power through out the operating band of the engine. Smaller motors that make hp through RPM in general have narrower bands of high power. Now if a high RPM motor can be made to have strong power from 6000 to 8000 rpm then it may be comparable to a motor that has power from 4000 to 6000 rpm. The real key comes down to gearing need to allow both cars to run at the proper RPM for the same ground speed.

The reality of life however is that most road cars are not geared like this and most motors even race motors are not equal in their distributions of torque over the RPM band. As such a 220 hp 1.8L Honda is not the same as 220 hp 3.2 911 motor or even a 220 hp 5.0L V8. In all cases the peak hp is the same, but the torque will not be. Good motor development will try to make the 1.8L motor provide good hp over a large enough RPM band that it can equal the power curve of a 5.0L V8 just at 2000 RPM more. However good motor development in 5.0L V8 will work on expanding the powerband of the motor so that even if it were "hp limit" by class rules the power band would be so wide that it would make 220 hp at 2500rpm all the way to 6000 rpm.

So this is why power/weight is good for classing cars, but does not tell the entire story. In the end torque is the key with engine design as the goal is not so much to make hp, but make torque at low RPM and then maintain it as RPM's increase. The hard part is that while hp inceases with RPM torque tends to fall off as it can be hard to fill the clyinders will all the air needed at those RPM. Remember at some point you need to consider that at 8000 rpm you have 1/2 as much time to get a cylinder full of air as at 4000 rpm. Fuel can just injected in at pretty much any rate, but without forced induction you need to try to still drawing a full filling of air each crank rotation. The trick is this in general harder to do at higher RPM and also harder to do over a wide RPM range than over a narrow one.

Point is hp and torque are linked. When people talk about big torque motors they should really talk about motors with a wide powerband. The wider the power band the better when you have equal hp.

 

Word for word GhettoRacer.

https://rennlist.com/forums/6266165-post81.html

 

Actually I was thinking of comparing the win ratio of the car you run vs the one I built. I know it's not very scientific but none of the examples so far have been either so obviously that doesn't matter in this conversation, see your Miata suggestion for reference.

It would be a good example of how successful we both have been with our different principles in real world practice.

As I have repeated, and continue to, I really feel this an arguement that will not be agreed on regardless so it's best to just to agree that we disagree with each other and leave it at that. This really isn't a new discussion, it's a VERY old one.

 

Its not that Im right VR, its the "LAW". Now, if you want to argue or discuss gear ratios optimization, weight to HP ratios of different cars, handling differences, absolute weight effects, those are interesting subjects where you might be able to make contributions based on real life. . However, base on the topic of discussion here. Different engine torques of two engines with the same HP will yeild the same accelerative forces unless the HP curves are NOT the same shape. Why are you turning this into a debate. Its basic phyisics here.

IF you are as knowledgeable as you say you are. Have spoken with top teams regarding the subject, analyse the porsche curves and tell us which you would choose for your racer and why. If you dont want to take the test, then it speaks miles for why you are even posting here.

mk

 

I think I remember this early in the first thread.
Still true too.

 

Quit stalling. Show me a professional who works with this for a living that says I'm wrong and I will listen. Step up to the plate.

 

what car is this? give details.

what does this mean in regards to this discussion.

you start going dollars to performance with me and I think you will loose that one too. by the way, the reason my car has done as well as it has, is due to to some of the things VR is advocating here. Its not the point of the discussion. the real point is that IT is not the rule. Engine torque as a value, can be completely neutralized by Power curve levels. completely. I dont know why I didnt think of this earlier, but think of a 375rwhp viper vs that GT3RS. the GT3R would never make more than 275ftlbs of torque, yet a viper has over 400ftlbs of torque. Yet, in real life, if the cars were the same weight, the GT3 RS would never have ANY disadvantage, even at a standing start, off a turn, no where. The point is, rear wheel torque , and net forces acting on the road are independant of engine torque values. Net forces acting on the road, through the tires is what give you acceleration at any vehicle speed.

mk

Tell us about your car. Or is it a secret program with secret race results.
I love hearing about other folks race cars. I learn a lot from others Ive seen off and on the track!

 

On this chart it all depends on the track and gearing.

If I am at 24 hrs of daytona I will pick the peak hp chart all day long. I maybe slower off the corners, but so much tiime is spent at high speeds that I can gear the car to run in top gear near the peak power point and pull away.

Now if I am at a circuit where I need to slow down alot and accelerate out of corners probably the lower peak hp curve is better. The reason is more power at lower RPM. However even then I need to consider how much time the car will spend at 5000 rpm vs 8000 rpm. If I can gear it right even then the peak hp car might prove better despite a very narrow power band. However the downside may be too much time shifting gears. This does not even bring up traffic. If you are in traffic and get stuck out of the desired power band at anytime you will suffer. So in a long traffic filled race it maybe better to give up on peak hp and use the wider powerband car due to greater power when you are stuck in traffic. In real on track race you what wins it for you may be powering out from a corner 5000 rpm. Not only that if you are infront on track you can often dictate apex speed to the car behind and try to force them to accelerate out of their powerband inbetween gears.

One classic example is the RS spyder vs R10. The R10 has fat powerband and more power to boot. So when held up in corners it had the power to accelerate away from the lighter RS spyder. This made it more suited to both long high speed runs (advantage in peak hp) and stop and go tracks where if a RS spyder got held up behind a GT car it would suffer much more than the R10.
Even so on fast flowing track the RS spyder was fast fast fast.

 

only to calculate engine HP. If HP is known, engine torque can be infinitely different and still produce the same rear whee torque, and thats the part that gets most folks confused. Rear wheel torque as found THROUGH the gear box is grossly different than engine torque as a value. again, that is the point.
its been discussed before, as you say, but for some reason , some still dont get it.

 

Yes this is true in theory and would be as well in practice if you can create the identical power curves and ensure both cars used the proper RPM range. Heck the power curves need not be the same one can be shifted up 2000 rpm and it would still work if the range of RPM used on track was the same.

The problem here is the reality of the piston engine. It is not the peak torque of the viper that is the issue, but the width of the power band. If the viper has a wider power band it will have an edge even if bother cars a optimally geared. The reality is even worse since it is very unlikely to optimize a gear set for all the turns on one race track let alone for all race tracks. As such the wider power band car has an edge. A good racing organzation will attempt to minimize this, but it is never easy.

Yes this is true. Acceleration is a function of tire grip, mass of the car, engine HP and wheel torque as muliplied through the gears. Actually engine shaft torque not relevant.

 

You are thinking and reasoning in the right terms. If gearing was the same for both, as it would be most cases for this engine, you have to consider Hp-seconds that would be applied at any track under any conditions. because the shift range of a GT3 would be around 6k to 8+k, you can see the time spent in the higher RPM ranges, where the HP (and thus rear wheel torque) would be greater. The lower HP curve has the greater engine torque. It would, as VR and you are saying, would come off turns better, but in the end the higher hp engine would more than likely be the one you would want due to the time you would spend in the upper HP ranges, and the HP is much greater than the lower HP losses as well. That is exactly what the telemetry systems can tell you. For me, I have poor man telemetry. I have video of the rpm guage, and WOT light. It can tell me if the gear box I have is optimal for a given track for example. If it isnt, well, its good to know , as I cant change anything anyway. At least I can optimize my shift points for a given track.

Your reasoning is sound an correct.

mk

 

I used that example, to show that even with the flat HP curve of the viper, that at any speed, the viper still would have less rear wheel forces. If you look at the GT3RS HP curve, you can see with 80% rpm drops for its gearing, that it would always have more HP in each gear over the operational engine rpm range. even if those gears were used on the viper, the same would be true. The point I was trying to make here is that engine torque is not a value that has any bearing on performance here. the 375rwhp viper will always be plagued with less hp at any operational speed vs the GT3RS with 438rwhp, also plaguing it with less rear wheel torque (forces at the rear wheels) at ANY vehicle speed. Even thought the viper still would have 125ft-lbs of torque more at the engine.
clost ratio gear boxes allow for better HP utilizaton. But remember, this can only be 100% of max HP if you used an infinitely variable gear box. close ratio gear boxes are used to keep the engine in the optimal HP range to maximize rear wheel torque.

you are joining this a little late, but early on, there was a discussion of a BMW vs caddy with the same shaped HP curve. surprisingly, almost identical, yet at the same HP levels as well, the BMW had 125ftlbs of torque less. there would be NO differnce on any track at any speed (in theory) if the cars were identical in all respects (besides engine and transmission swap) . also, like you mentioned, this need not only be the case. close ratio gear boxes can narrow any gap that a torque weighted Hp curve might have, or as you also say, if the range of RPM used near the top of the HP curve is the same, it really doesnt matter what is happening down lower in the non-used rpm range. (unless you miss a shift or something )

mk

 

Why bother? What difference will it make? The two of you have totally closed minds, and are completely intolerant of differing opinions on this topic. Mark has hurled half a dozen unsolicited PM's at me last week with increasingly strident insults and 1,200 more words explaining why he is "right". I have no desire to stoop to the level of religious zealotry and bring professional drivers whose names you'd recognize into it. And, FYI, that is not "stalling".

Namedropping will not make my opinion more true or yours less true, or vice versa.

 

Well, it's your signature to say "Professional Racing & Driving Coach - Ask me how to improve your lap times" and you have so far mostly dismissed what others have to say. Would be nice if you could prove the point of your theory. You know, have some basic physics to support it, some good references to back it up, perhaps show some race tuning experience connected to the theory.

I'd gladly read, hear and experience if you have something to share and you have before so I don't put it personal on you. But in this case I take it as you can't. Now it's more "I have a secret formula that I can't tell anyone.". So doesn't look very serious.