In the upcoming game Project Gotham Racing 3 the McLaren F1 LM is in the car. It is limited to 225mph in real life but in this game all of the cars have their speed limiters removed.

What i'm not sure of is how the LM is limited. Is it limited electronically? Or is it limited by it's rear wing. And also if it's electronic how fast do you think it could go?

It's my understanding that the LM is drag and/or gearing limited to 225 mph - whichever way you want to phrase it. Therefore, you would have to change the gearing of the car, increase the power, or reduce the amount of drag to theoretically give it a higher top speed.

>8^)
ER

Thanks. And another thing. Since the LM has 680hp as opposed to the F1's 627, does it accelerate faster?

Yes, the LM does accelerate faster. Here's a breakdown of in-gear acceleration times compared between the LM and F1 taken from CAR Magazine.

http://a2.cpimg.com/image/74/DA/34131572-e321-015C013B-.jpg

Besides the additional power, the LM also weighs less than a standard F1 by approximately 60kg.

>8^)
ER

Wow!
100-120 takes 3 vs. 4.5 seconds. That's a huge difference!

My guess is that the LM spec engine in the road car would go 250 flat.

F= CdAV^3/150,000
x rwhp = 5.75(241^3)/150,000
x = 536, so road car has 20 or more to play with for tire losses. 627 horsepower * .88 to get rwhp, because .15 is a value for low horsepower cars, and apparently this figure becomes less accurate with the more horsepower you have. I wouldn't be shocked if it dyno'd on SAE corrected dynojet at 560 or more.
680 * .88 -20 = 578.
578 = 5.75(v^3)/150,000
15088695 = v^3
v = 247.106343

Good enough guess.

Wow!
100-120 takes 3 vs. 4.5 seconds. That's a huge difference!

My guess is that the LM spec engine in the road car would go 250 flat.

F= CdAV^3/150,000
x rwhp = 5.75(241^3)/150,000
x = 536, so road car has 20 or more to play with for tire losses. 627 horsepower * .88 to get rwhp, because .15 is a value for low horsepower cars, and apparently this figure becomes less accurate with the more horsepower you have. I wouldn't be shocked if it dyno'd on SAE corrected dynojet at 560 or more.
680 * .88 -20 = 578.
578 = 5.75(v^3)/150,000
15088695 = v^3
v = 247.106343

Good enough guess.
Where are you getting those numbers from? Where do you include gearing? Please say real world test data or I'm going to shoot myself.

Which numbers? You doubting my horsepower or CdA figures? Look em up yourself if so.
The formula is derived from a base drag equation including the density of air.
Gearing has nothing to do with it -- I said the road car, so you might have to swap in for a slightly higher sixth to bring the power peak in at 250, but gearing has nothing to do with it in this case.

Can you tell us the equations you use, what each of the variables is, and the values you use for each of the variables?

Thanks!

Here's a post on another forum where I discuss drag and a top speed calculation:

http://www.mclarenfreak.com/forum/index.php?showtopic=12

I document all my variables, explain my equations, and explain where all of my numbers come from.

If you could do the same, it would make things easier to understand =)

As far as I can tell, your equations are correct. I don't think that including the torque/wheel radius is necessary. My base equation was: F = 0.5CdAρV^2 , p = rho (density of air). Converting to get horsepower required took me to my final equation. Just a bunch of unit manipulation and standard density of air.

"this means that the engine does NOT produce its maximum force when the wheels are spinning the fastest."
Absolutely true in a lot of cars. From what I read in Driving Ambition, however, the McLaren did hit its top speed while in the "Sweet spot" because although its sixth gear is overdrive, the car is so damn fast it is not really overdrive the way my car, which tops out around 4000 rpm in 4th gear is.

It was explained to me by a few texts that way. Since my original equation gives you the force necessary, my final equation also gives you that, where the force is how much force you can put out at the rear wheels, measured in horsepower. That way eliminates the tire and such, because you are using a measured value (dyno), although for cars that have not been dynoed like the mclaren, you need to estimate driveline losses.

I don't know how else to explain this. I'm simply calculating the drag that the road car experiences, then applying that in a ratio type comparison with the added horsepower of the LM spec engine.

F1 Monster - CdA of the road car is 5.75, although I forget (Driving Ambition is downstairs!) what the CD and A are. CD is somehwere between .31 and .33, but you can look that up if you like. All I have with me at the moment is the combination of the two :). I explained my RWHP equation previously.

I dont know what else to tell you.

Wow...those are pretty impressive math terms :uhoh: And the theoretical top speed is very cool. I'll have to remember that the LM's engine could pretty much hit 250 :grinyes:

What good is a theoretical topspeed?
The LM could not do that speed anyway because it's aerodynamics arent up to it.
The LM is more of a circuithandler, but still the sickest car in the world.

F1 Guy, thanks for the explanation.
Amanichen, your comments?

F1 Guy, thanks for the explanation.
Amanichen, your comments?


Are you reffering to me?
In that case lets cool down the sarcasm as I'm simply pointing out the fact that it's not possible to run 250mph with a LM as it is and I'm sure you all already knew that, but nevertheless still a fact.


It's really an endless discussion if were about to discuss theoretical topspeeds on McLarens as their engines are what you make of them.
But, trying to "modify" this work of art is almost close to idiotic as I trust McLaren has already done extensive testing on that matter.

It sure doesn't look like he was referring to you Thorst. :grinno:

>8^)
ER

It sure doesn't look like he was referring to you Thorst. :grinno:

>8^)
ER


Ooops youre right, I bit early in the morning here in Norway, sorry F1Monster! :p

I don't feel paranoid...really I don't! :loser:

Thorst,
I was asking Amanichen for comments since he is able to explain engineering concepts very clearly. No sarcasm to anyone. :)

Amanichen, your comments?I don't agree with the logic and approximations he used -- there's too many unexplained values and unrealistic assumptions. His calculation is a great academic classroom exercise but doesn't necessarily reflect a real world answer. I can do a more realistic calculation that involves fewer magic numbers and unexplained constants than Theflinger used. Unfortunately I cannot produce a 100% accurate measure without having actual dynamometer test data.

Does anybody with Driving Ambition know what the Cd (drag coefficient) and A (area) of the road car are, separately? Please provide units. Also, the fifth and sixth gear ratios for the road car would be helpful. The rear tire size (units included) will also be necessary. The most important thing I need is ACCURATE peak torque@RPM data for the road car engine, and LM engine. By accurate, I mean from driving ambition, or Gordon Murray, not the internet.

"The Book" lists peak torque for the cars.

The F1 = 651Nm @ 5600rpm

The LM = 703Nm @ 4500rpm

They have this on the spec sheet for Aerodynamics of the road car:

Cd - 0.32 frontal area 1.79m²

There are no figures for the LM or GTR though in case you are wondering.

The Autocar McLaren F1 road car book also lists the CDA as 0.57

Strangely, I don't see the gear ratios for the F1 on the spec sheets in DA but they are listed in the Autocar book. They may be hidden somewhere within the text.

1st: 3.23
2nd: 2.19
3rd: 1.71
4th: 1.39
5th: 1.16
6th: 0.93
FD: 2.37:1

The rear tire sizes are 315/45ZR17 for the F1 and 345/35ZR18 for the LM.

>8^)
ER

The Autocar book also contains a dynograph for the F1. Unfortunately the scans I have of that book made by someone else don't include that page, but I could produce an image of it for you if you think you need it.

>8^)
ER

The Autocar book also contains a dynograph for the F1. Unfortunately the scans I have of that book made by someone else don't include that page, but I could produce an image of it for you if you think you need it.

>8^)
ERActually, the dyno graph would be quite valuable to me, as the true solution to top speed involves matching an aerodynamic drag curve with a power curve, and then finding the speed (RPM or wheel speed) at which they intersect. I can calculate an aerodynamic curve, but the problem is that without dyno data I can't calculate a power curve. Having the power curve makes things much easier.

Thanks for the other data -- it'll be useful if you can't get the dyno graph.

Here's the dynograph from the Autocar book:

http://img.photobucket.com/albums/v482/Peloton25/McLaren%20F1/th_F1_dynograph.jpg (http://img.photobucket.com/albums/v482/Peloton25/McLaren%20F1/F1_dynograph.jpg)

>8^)
ER

Here's the dynograph from the Autocar book:

http://img.photobucket.com/albums/v482/Peloton25/McLaren%20F1/th_F1_dynograph.jpg (http://img.photobucket.com/albums/v482/Peloton25/McLaren%20F1/F1_dynograph.jpg)

>8^)
ERIs this an engine dyno or a wheel dyno graph? It looks like an engine dyno graph.

It's engine dyno. 627 horsepower at peak. Looks about there to me. I'd be seriously impressed were that a chassis dyno, that would mean an unbelievable engine became even more unreal.

"By accurate, I mean from driving ambition, or Gordon Murray, not the internet"

Very funny. I believe I did state I got my figures from Driving Ambition?

Also, what do you plan on doing with the CD separate from the Frontal Area?

Honestly dude, I'm looking forward to an explanation from you. I'd love to learn more. No subtle keyboard warrior sarcasm here. I just don't see why in a car that peaks out at max revs and tops out in sixth at the rev limiter needs the gears and tires considered? As far as I know cars don't top out at torque peaks?

I just used those formulas because my original idea of running the LM spec engine in the ROAD CAR (LM car could not reach 250, not arguing that at all), I figured I could discard all the losses besides aerodynamics. They'd be the same (with a variation that's not really significant -- I doubt tire losses would impact the mph by more than 1 from between measuring at 240 and 250) as in the original, 627 horse road car.
Along that crazy train of thought are you planning on producing a rough tire loss at speed? Because something to consider there is the 170 pounds of downforce at 160 (As far as I know the only downforce figure stated in DA), but also the fact that the F1's tires probably are slightly less grippy than supercar tires of today. Just thought you might want to know that.

Again, being honest, looking forward to it.

Is this an engine dyno or a wheel dyno graph? It looks like an engine dyno graph.

For the record, the book doesn't specify, but given the quoted power figures of the car and what is shown on that chart I'd have to agree that it was most certainly produced by an engine dyno.

>8^)
ER

For the record...
"CdA of the road car is 5.75, although I forget (Driving Ambition is downstairs!) what the CD and A are. CD is somehwere between .31 and .33, but you can look that up if you like."

Damn good guess for being a loser who gets his figures from the internet right? (just playing)

http://flinger.ath.cx/F1/DAspec.jpg

http://flinger.ath.cx/F1/DAfront.jpg

For the record, the book doesn't specify, but given the quoted power figures of the car and what is shown on that chart I'd have to agree that it was most certainly produced by an engine dyno.

>8^)
EROne more question -- I have scans from a road and track article that says the F1 does 60mph @ 2000RPM in 6th gear...confirm/deny?

Are you asking me to confirm it based on other sources of data, or from personal experience? I didn't really pay attention on my ride along. Maybe Mr Selldorff will see this and confirm that info for us.

I can look through some other things, but it is probably easier if you just do the math based on gearing and tire size. Wouldn't that work, or does power have some random effect on the equation?

>8^)
ER

http://s94779296.onlinehome.us/McLarenF1/McLarenF1.html

Here are the numbers I promised. You can skip the first two sections, and head directly to the Results section if you wish, but PLEASE read all of the results section before you make any comments. If you're really impatient then the important numbers are in bold, and in a box down at the bottom of the page.

There's only a few miles per hour difference between my calculation and what Theflinger calculated. If there's any bickering about who's method is better I'm going to remove the page, and this post. Yes, I spent more around 8 hours on this, only to have an answer that was a couple miles per hour different than Theflinger's. You might think it was a complete waste of time, but before you make a judgement, keep this in mind:

If the car were only going 100mph, there would be a much larger difference between my answer and his answer, and my answer would still be far more accurate. Since the McLaren F1 is capable of traveling at 240+ mph, and when going that fast there's at least four times the wind resistance as it has at 100mph, it's operating at a speed where a decent step up in power will only make you gain a tiny fraction of extra speed. This is the reason that our numbers are very close.

My method, like his, is an approximation (due to lack of proper dyno data from the LM engine.) However, the numbers that I used in it were more valid, and more accurate than what Theflinger calculated because I based mine off of real world test data, and not just the same old 15% drivetrain loss that's too often used on any car with a manual gearbox.

The McLaren F1 isn't like your average street car, so you can't assume a 15% drivetrain loss and then subtract 20 hp due to the tires. Its drivetrain and tires are remarkably efficient at high RPMs, as noted by the 3.8% drivetrain/tire loss. In the case with the McLaren F1: the car speed, aerodynamics, engine output, and gearing mean that there's only a couple of mph difference between my answer and Theflinger's answers.

(I'm not flaming here -- only stating the facts.)

Thanks. Very good stuff.
So question, the 3.8% drivetrain loss...would it be safe to assume that today's high performance cars also operate with less than 10 percent loss? As in the new 500 horsepower z06. That would account for the seeming overrating of the c5z06 (405 horsepower, chassis dynoed higher). Just wonderin.

Also, you got the deformed tire radius from the known top speed run, correct? As in, it was the only variable you didnt know, so you solved for it, then used it in the 680 horse run?


Appreciate the work that went into this. It's too bad that the aero manipulation that went into the car for the 391 km/h run adn probably every top speed run made (discussed in large detail on a thread on this forum) will probably make accurate predictions impossible.

I guess it's pretty fun to work these equations. Obviously I'm not bashing you as I'm into this too, so don't get bitchy on me....but Gordon Murray didn't do any of this. He wasn't shooting for this. It happened. I wonder sometimes if I should be studying what HE was working when he created the car instead of this stuff.

Again, thanks for the work.

PS about the bolded stuff, I wouldn't worry about people arguing for me over that page! :)

fact: the f1 lm is drag limited to 225, not gear limited. the engine is an unrestricted gtr engine which is why it has 680 bhp, opposed to 600. the xp5 road car that andy wallace drove to 240.1 mph had the rev limiter deactivated which is why it went 240.1 the standard road car cant hit 240 mph because it is rev limited to either 7500 rpm or 6500 i forget, anyway the reason the f1 lm can go no faster than 225 is because of the drag and downforce it produces, which is enough to drive upside down at 150 mph

Thanks. Very good stuff.
So question, the 3.8% drivetrain loss...would it be safe to assume that today's high performance cars also operate with less than 10 percent loss?It's not a constant number, and it's not a constant percentage -- it varies as RPM and gearing does, so you'd need "speed@rpm in gear" and aerodynamic data to estimate how much power is lost to what's sitting between the crank and the pavement.

Basically, I wouldn't go assuming anything.

As in the new 500 horsepower z06. That would account for the seeming overrating of the c5z06 (405 horsepower, chassis dynoed higher). Just wonderin.Horsepower ratings from manufacturers have been notoriously unreliable. Unless you have a dyno sheet from both the engine and the wheels (or speed, aerodynamic, and gearing data, in its place) you can't reliably calculate the drivetrain and tire losses.

Also, you got the deformed tire radius from the known top speed run, correct? As in, it was the only variable you didnt know, so you solved for it, then used it in the 680 horse run?That's correct. I took the known speed, known gearing, and known engine RPM to find the deformed tire radius.

Appreciate the work that went into this. It's too bad that the aero manipulation that went into the car for the 391 km/h run adn probably every top speed run made (discussed in large detail on a thread on this forum) will probably make accurate predictions impossible.There's all sorts of tricks that people can do, and yes, it sort of makes top speed comparisons worthless. There's also only a few places in the world where you can safely run 200+ mph on pavement (salt flats are another story.)

I guess it's pretty fun to work these equations.I wouldn't have done it if I didn't want to do it. This type of problem was actually an entire lab in one of my classes last year -- the matching of two independently operating systems to see where they reach an equilibrium.

Obviously I'm not bashing you as I'm into this too, so don't get bitchy on me....but Gordon Murray didn't do any of this. He wasn't shooting for this. It happened. I wonder sometimes if I should be studying what HE was working when he created the car instead of this stuff.I agree that he probably wasn't shooting for a 240mph top speed. I think he wanted to make the car as driveable and responsive as possible all the way from idle, up to maximum speed (which means, among other things, making sure the car hits its top speed at redline in top gear.) It turned out though, that the result was a ridiculously fast car.

PS about the bolded stuff, I wouldn't worry about people arguing for me over that page! :)It's mostly to put things in perspective for people who might be gearheads, but who might not know much engineering or physics. Of course there's always a few ignorant haters to come along too. I just want to be sure that my results aren't misinterpreted -- people on the internet will take any bit of information they find and then run around waving it like they know what they're talking about.

I agree that he probably wasn't shooting for a 240mph top speed. I think he wanted to make the car as driveable and responsive as possible all the way from idle, up to maximum speed (which means, among other things, making sure the car hits its top speed at redline in top gear.) It turned out though, that the result was a ridiculously fast car.

but the f1 doesnt hit top speed at the rev limit, it hit 240.1 with the limiter removed

As in the new 500 horsepower z06. That would account for the seeming overrating of the c5z06 (405 horsepower, chassis dynoed higher). Just wonderin.

Horsepower ratings from manufacturers have been notoriously unreliable. Unless you have a dyno sheet from both the engine and the wheels (or speed, aerodynamic, and gearing data, in its place) you can't reliably calculate the drivetrain and tire losses.
I'd agree, except that the c6z06 was the first car certified with the new SAE process, which was designed completely new to hold cars to a 2% engine to engine variation and no over/underrating.
The c5z06 had no such cert, that's why I was wondering if we could say that the seeming undderating was really a drivetrain thing.

but the f1 doesnt hit top speed at the rev limit, it hit 240.1 with the limiter removed
A stock F1 road car hits its top speed at the rev limit of 7500RPM.

A modified F1 road car hit its top speed at its rev limit of 8300RPM.

The F1 hits top speed at the rev limit, period.

BTW, disabling the rev limiter would destroy the engine -- it was simply INCREASED by 800 RPM for the 240mph test.

I'd agree, except that the c6z06 was the first car certified with the new SAE process, which was designed completely new to hold cars to a 2% engine to engine variation and no over/underrating.
The c5z06 had no such cert, that's why I was wondering if we could say that the seeming undderating was really a drivetrain thing.As I said, horsepower ratings from manufacturers are traditionally unreliable for a number of reasons. They can play all sorts of tricks like: quoting crank horsepower, and removing normal engine accessories such as a water pump or exhaust system, or simply quoting a smaller or larger figure on a sales borchure. Unless someone tells you how a test was done, its results are worthless.

Exactly why there's a mystery surrounding the C5 corvette numbers is something you should ask General Motors.

A stock F1 road car hits its top speed at the rev limit of 7500RPM.

A modified F1 road car hit its top speed at its rev limit of 8300RPM.

The F1 hits top speed at the rev limit, period.

BTW, disabling the rev limiter would destroy the engine -- it was simply INCREASED by 800 RPM for the 240mph test.

oh i see. i read that xp5 had the limiter removed for the top speed run.
also the engine wouldnt be destroyed with the limiter removed if the gearing only allows the car to hit a certain speed, that means the engine wouldnt redline because the rpms wouldnt get high enough, right?
a car only hits top speed when it reaches the maximum speed it can reach with the gearing it has i thought

I believe the engine would redline, but the car would not accelerate past a certain point.

oh i see. i read that xp5 had the limiter removed for the top speed run.Removed is the wrong word because it wasn't removed, it was simply raised.

also the engine wouldnt be destroyed with the limiter removed if the gearing only allows the car to hit a certain speed, that means the engine wouldnt redline because the rpms wouldnt get high enough, right?Drag isn't a brick wall -- the faster you go, the harder it pushes you back. If you could get the engine to rev higher, it would produce more power, and push the car faster through the air. However, at a certain RPM, the valve cams would start lifting off the actuators and the valves would fail to open properly. This would cause extensive damage to the engine.

a car only hits top speed when it reaches the maximum speed it can reach with the gearing it has i thoughtWith any car there are limitations on top speed:

Gearing (how fast you can get the wheels to turn)
Aerodynamics (how hard it is to push the car through the air)

When the gearing limitation equals the aerodynamic limitation, your car has reached its maximum speed -- it just won't go any faster.

People call a vehicle "gear limited" when the more restrictive of the two factors is the gear ratio. The car's aerodynamic limitation will never reach the gearing limitation unless you want to severely go past the redline of your engine.

People call a vehicle "drag and gearing limited" when the aerodynamic drag is able to catch up to the gear limitation without exceeding the engine redline. Uninformed people tend to call this "drag limited" but really it is "drag and gearing" limited, because the actual maximum speed depends on both.

You guys remember the 0-100-0 mph record set by Andy Wallace? In that interview/article he said the LM was only good for 190 mph because of the increased drag. Take that for what it's worth.

the lm would be faster than the roadcar because of increased engine performance, but due to the gtr body cladding its top speed is reduced to 225 due to the drag, not 190. i'd be willing to bet that a f1 roadcar fitted with the lm's unrestrcted engine would wax the new 253 mph speed record set by the veyron recently. :iceslolan

I wouldn't be so sure. Each addition mile per hour in speed takes a LOT of horsepower once you get to 230mph or so. What's the difference in bhp between the LM and regular F1 motors? With bhp and gearing and cdA figures known, it should be possible to work out the theoretical top speed. I don't know how to do this calculation, but I think Amanichen would?

roadcar: 627bhp, LM: 680bhp. so the difference is about 53 bhp, give or take a few depending on the condition of the engines...

I wouldn't be so sure. Each addition mile per hour in speed takes a LOT of horsepower once you get to 230mph or so. What's the difference in bhp between the LM and regular F1 motors? With bhp and gearing and cdA figures known, it should be possible to work out the theoretical top speed. I don't know how to do this calculation, but I think Amanichen would?


Exactly what different is this than what he already instructed us on? :)

I wouldn't be so sure. Each addition mile per hour in speed takes a LOT of horsepower once you get to 230mph or so. What's the difference in bhp between the LM and regular F1 motors? With bhp and gearing and cdA figures known, it should be possible to work out the theoretical top speed. I don't know how to do this calculation, but I think Amanichen would?Already did it:

http://s94779296.onlinehome.us/McLarenF1/McLarenF1.html

The link is a few posts up back on Page 2. My hosting service went down so I had to remove it for a couple of weeks.

Cool, thanks. At the very end, you say:
If it were re-geared it could reach a higher speed:
With a new 6th gear ratio: 2.37 * 0.75 = 1.7775...
The RPM where max speed occurs is: 6702
The max speed is: 416.4794 in km/h
The max speed is: 258.7878 in mph

Is this for this gear ratio or for all gear ratios...?
Could you explain why it could not theoretically be higher with a different gear ratio?

the lm would be faster than the roadcar because of increased engine performance, but due to the gtr body cladding its top speed is reduced to 225 due to the drag, not 190.
Are you implying that we're not to believe Andy Wallace? He's had a tremendous amount of experience in Mclaren products so I'd take his word for it on this issue.

Cool, thanks. At the very end, you say:
If it were re-geared it could reach a higher speed:
With a new 6th gear ratio: 2.37 * 0.75 = 1.7775...
The RPM where max speed occurs is: 6702
The max speed is: 416.4794 in km/h
The max speed is: 258.7878 in mph

Is this for this gear ratio or for all gear ratios...?
Could you explain why it could not theoretically be higher with a different gear ratio?If you installed a LM engine in a F1 road car, you're initially limited by gearing, rather than aerodynamics. If you change the 6th gear ratio you can allow the gearing and drag curves to intersect, you can then hit the true top speed possible with that engine power.

Are you implying that we're not to believe Andy Wallace? He's had a tremendous amount of experience in Mclaren products so I'd take his word for it on this issue.

yes he does, but the 225 number comes from mclaren cars, i believe they know the car just a little better than he does... also something tells me that the f1 gtr's probably went a little faster than 190 down the mulsanne straight at le mans, maybe somewhere in the 225 range... so i highly doubt that the gtr hd kit limits the car to 190, when speeds higher than 190 were attained during races...

yes he does, but the 225 number comes from mclaren cars, i believe they know the car just a little better than he does... also something tells me that the f1 gtr's probably went a little faster than 190 down the mulsanne straight at le mans, maybe somewhere in the 225 range... so i highly doubt that the gtr hd kit limits the car to 190, when speeds higher than 190 were attained during races...The 225mph is stated in an article that covers the 0-100-0 record set by Andy Wallace in the LM, while McLaren observed.

However, later in that same article Andy Wallace is quoted as saying that the LM hits a wall at 190mph flat out.

Going with what Andy said, I think the top speed is closer to 225, but that the top end acceleration isn't as good after 190mph because of the drag on the GTR body.

Going with what Andy said, I think the top speed is closer to 225, but that the top end acceleration isn't as good after 190mph because of the drag on the GTR body.

That's how I read it. :thumbsup:

Also, as Fortune mentions, the GTRs with the same aerodynamic add-ons certainly went faster than 190mph on some tracks, and they were even down on power from what the LM engine produces.

>8^)
ER