200mph+ for less?

[P4ROT]

ruzman said:

An SL55 can be had for about £12k, and a pint to the right man can get the 155mph limit removed, to top out at 202 or 207mph depending on who you believe (it could be argued that isn't standard anymore).

I know they are still very quick, even by today's mental standards. However, Mercedes figures vary from 'only' around 480 bhp, to later cars that are said to have around 520 bhp. How come they are so quick (especially so, considering they weigh nearly two tonnes). Is it gearing? Or are the quoted power figures very pessimistic?

P4ROT

[HappyMidget]

P4ROT said:

I know they are still very quick, even by today's mental standards. However, Mercedes figures vary from 'only' around 480 bhp, to later cars that are said to have around 520 bhp. How come they are so quick (especially so, considering they weigh nearly two tonnes). Is it gearing? Or are the quoted power figures very pessimistic?

P4ROT

Weight has nothing to do with top speed.

[liner33]

HappyMidget said:

Weight has nothing to do with top speed.

Of course it does, increase the weight and you increase rolling resistance, it has less impact that other factors but far from no impact

[CraigyMc]

liner33 said:

HappyMidget said:

Weight has nothing to do with top speed.

Of course it does, increase the weight and you increase rolling resistance, it has less impact that other factors but far from no impact

Compared to aero resistance, tyre rolling resistance is sod all - it's less than 10% compared to aerodynamic drag at >90%.

The rolling resistance isn't dictated just by weight either: it's a function of tyre compound, size and pressure, suspension setup.

If the road has an incline on it, weight can be either beneficial or detrimental (rolling down a hill, weight helps).

[liner33]

CraigyMc said:

Compared to aero resistance, tyre rolling resistance is sod all - it's less than 10% compared to aerodynamic drag at >90%.

The rolling resistance isn't dictated just by weight either: it's a function of tyre compound, size and pressure, suspension setup.

If the road has an incline on it, weight can be either beneficial or detrimental (rolling down a hill, weight helps).

Summed up by "it has less impact that other factors but far from no impact"

[J4CKO]

P4ROT said:

ruzman said:

An SL55 can be had for about £12k, and a pint to the right man can get the 155mph limit removed, to top out at 202 or 207mph depending on who you believe (it could be argued that isn't standard anymore).

I know they are still very quick, even by today's mental standards. However, Mercedes figures vary from 'only' around 480 bhp, to later cars that are said to have around 520 bhp. How come they are so quick (especially so, considering they weigh nearly two tonnes). Is it gearing? Or are the quoted power figures very pessimistic?

P4ROT

They have a lot of torque, from very low in the rev range, > 500 lb/ft, that is why they feel quick, that and 500 bhp, plus very tunable for more.

[WCZ]

200Plus Club said:

Having done 202mph at v max in a 997 turbo which had say £20k spent on it in mods I would say that's one of the cheapest ways to reliably hit 200mph. 50k car and bobs yer uncle.

it'd be nuts to spend £70k when you could easily hit 200+ in a remapped RS6 with 750-800bhp for £25k

[ruzman]

liner33 said:

Summed up by "it has less impact that other factors but far from no impact"

WARNING: NERD HAT ON
I didn't set out to prove anyone right or wrong - but the physicist in me was curious. The below is a good paper on rolling resistance.

http://geosci.uchicago.edu/~moyer/GEOS24705/Readin...

Rolling Resistance
The formula for rolling resistance Power Requirement is Power = Crr m g v (rolling resistance * mass * gravity * velocity)

The paper shares the median rolling resistance of tyres from 2005 (Crr = 0.0099)

Thus the power required to overcome rolling resistance at 200mph in a 2000kg car is =
= 0.0099 * 2000 * 9.8 * 89.4 = 17.3kw ~ 23hp
Half the weight to a 1000kg car and you need about 11hp less to maintain 200mph.

Aero
Aero power requirements are given by: Power = ½ρA v3Cd

All else equal the top speed will be governed proportionally by the Cd –

So out of interest I compared a Lambo and the SL55
SL Cd = 0.29
Lamborghini Gallardo Cd = 0.34

A 560hp Gallardo (LP-560-4) has a top speed of 202mph
Which means that the SL55 power requirement to hit that same speed = 0.29/0.34 * 560 = 478hp.
Actual SL quoted power – (476-512hp)

So the SL55 from a simple comparison looks as if it can top 200mph.
(I expect the Lambo has a greater frontal area and is also 4 wheel drive so will have even greater frictional losses)

[M-SportMatt]

ruzman said:

WARNING: NERD HAT ON
I didn't set out to prove anyone right or wrong - but the physicist in me was curious. The below is a good paper on rolling resistance.

http://geosci.uchicago.edu/~moyer/GEOS24705/Readin...

Rolling Resistance
The formula for rolling resistance Power Requirement is Power = Crr m g v (rolling resistance * mass * gravity * velocity)

The paper shares the median rolling resistance of tyres from 2005 (Crr = 0.0099)

Thus the power required to overcome rolling resistance at 200mph in a 2000kg car is =
= 0.0099 * 2000 * 9.8 * 89.4 = 17.3kw ~ 23hp
Half the weight to a 1000kg car and you need about 11hp less to maintain 200mph.

Aero
Aero power requirements are given by: Power = ½?A v3Cd

All else equal the top speed will be governed proportionally by the Cd –

So out of interest I compared a Lambo and the SL55
SL Cd = 0.29
Lamborghini Gallardo Cd = 0.34

A 560hp Gallardo (LP-560-4) has a top speed of 202mph
Which means that the SL55 power requirement to hit that same speed = 0.29/0.34 * 560 = 478hp.
Actual SL quoted power – (476-512hp)

So the SL55 from a simple comparison looks as if it can top 200mph.
(I expect the Lambo has a greater frontal area and is also 4 wheel drive so will have even greater frictional losses)

Bit simplistic

Unless you have an abundance of Power to go past 200mph then that maths wont work.

If you have just enough power to do 200mph the car needs to be geared such that it is producing that peak power at 200mph.........therein lies the difficulty

[Bradley1500]

I’ve noticed a few similar threads that have been posted recently, and the predictable answer is always some kind of powerful German barge. For the cost/result ratio they seem to be the best bet.

I am always surprised at the suggestions of the E60 M5 though. I know they’re proven to do 206MPH with the limiter removed, but having driven and been a passenger in one I find it hard to believe. The one I drove didn’t feel all that fast, and having been a passenger in it to the factory limiter, it took a long time to get there.

I suspect the car I experienced wasn’t in the best health. It was a real disappointment for me as I have always loved the V10-engined cars, especially for their howling exhaust note, but after experiencing one first hand I thought it was a bit crap truth be told.

The later F10 cars with a limiter removal are much more like it. The Evolve remapped one I have been in was supposedly close to 700BHP, and the acceleration even into very illegal speeds was relentless.

C.A.R. said:

I think the older Japanese stuff could be worthy with some money thrown at it - the JZA80 Supra TT or the slippery FD3S RX-7 might be in with a shout - if you throw money at them of course.

I have noticed a few other posters mentioning the 90s Japanese turbo cars. As standard none of them would stand a chance, but with some modifications I suspect most would be capable – although that could apply to the majority of cars.

I am hoping to crack 200MPH in my Toyota Supra. The gearing is good for a smidge over 207MPH, but it doesn’t have enough power to get there currently. The car has seen an indicated 175MPH and had more to go, although I very much doubt it would have kept going to a genuine (or even indicated!) 200MPH in its current form.

I plan to fit a big single turbo this winter which should give me enough oomph to crack 200MPH. In the context of this thread though it wouldn’t rate very highly, as to get enough power for 200MPH you would need to spend over £20K including the purchase price, and that’s before doing any other modifications to make the car safely capable of 200MPH.

[CraigyMc]

ruzman said:

Aero
Aero power requirements are given by: Power = ½?A v3Cd

All else equal the top speed will be governed proportionally by the Cd –

So out of interest I compared a Lambo and the SL55
SL Cd = 0.29
Lamborghini Gallardo Cd = 0.34

A 560hp Gallardo (LP-560-4) has a top speed of 202mph
Which means that the SL55 power requirement to hit that same speed = 0.29/0.34 * 560 = 478hp.
Actual SL quoted power – (476-512hp)

So the SL55 from a simple comparison looks as if it can top 200mph.
(I expect the Lambo has a greater frontal area and is also 4 wheel drive so will have even greater frictional losses)

Are we assuming the Gallardo and the SL55 have the same cross-sectional area?

[ruzman]

CraigyMc said:

Are we assuming the Gallardo and the SL55 have the same cross-sectional area?

Yes

In reality I doubt there's much difference but I'd also be prepared to believe that the muscular Lambo has a bigger area.

Having found the formulas I was just messing around and surprised the result aligned so closely with real world test results.

[pSyCoSiS]

I have an 2003 S55 AMG Kompressor.

Bought for just under £10k (but has been rather ruinous to maintain and get up to scratch).

Would that be capable of 200mph with the limiter removed?

[ZX10R NIN]

Not without some engine work.

[pSyCoSiS]

ZX10R NIN said:

Not without some engine work.

Remap, pulley and headers then?

With the limiter removed, what would they top out at as standard?

[AMGJocky]

WCZ said:

200Plus Club said:

Having done 202mph at v max in a 997 turbo which had say £20k spent on it in mods I would say that's one of the cheapest ways to reliably hit 200mph. 50k car and bobs yer uncle.

it'd be nuts to spend £70k when you could easily hit 200+ in a remapped RS6 with 750-800bhp for £25k

Define 'easily.'

The 997 would be a much better way.

[LasseV]

AMGJocky said:

Define 'easily.'

The 997 would be a much better way.

Yeah, i think RS6 has same kind of aero than brick has.... I read a thread where one dude crashed his Supra in Vmax event at speed of 202mph or so. His earlier attempt in his Lamborghini was something like 198 mph or so. Going genuine 200mph is not easy, not even for modded family wagon...

Edit: 90's japanese high performance cars are genuinely fast cars in vmax events. They are quite cheap too at the moment.

Edited by LasseV on Tuesday 21st March 15:31

[200Plus Club]

AMGJocky said:

WCZ said:

200Plus Club said:

Having done 202mph at v max in a 997 turbo which had say £20k spent on it in mods I would say that's one of the cheapest ways to reliably hit 200mph. 50k car and bobs yer uncle.

it'd be nuts to spend £70k when you could easily hit 200+ in a remapped RS6 with 750-800bhp for £25k

Define 'easily.'

The 997 would be a much better way.

we actually did 213mph in a 997 turbo there, but that had to be fair had a "serious" amount of money spent on it. bear in mind brunters is only 1 and a bit miles, given room and gearing the 997 would have done 230 i bet

[IanH755]

AMGJocky said:

Define 'easily.'

The 997 would be a much better way.

As mentioned at the start of the thread, my C6 RS6 estate (£27k when bought mid 2015) had an engine/gearbox remap and secondary CAT removal in 1 day for around £2k back then (IIRC it's £300+ cheaper now) which got me 730hp with 750lbs/ft. I did an autobahn video of it going from 0-206mph speedo (200mph on a 10hz GPS reciever same as VBox etc) in only 36 seconds with another gear still to go, so I'd say that was pretty easy despite "having the the same kind of aero a brick has"

Edited by IanH755 on Tuesday 21st March 17:34

[Guyr]

I've done over 200mph both on road and at Brunters many times, as well as GPS measuring a variety of cars at >190mph on both Autobahns and Bruntingthorpe.

Few thoughts as follows:

1. GPS is not the same as speedo, one of my cars (Ruf GT2) was accurate to 3 mph at 210mph, whereas my Gallardo speedo was 20mph out at 190mph.

2. Gearing does not ensure you will reach 200mph (power does), but if you don't have the gearing it will stop you. My Ruf hit the rev-limiter noticeably at 217mph, hence why Ruf sold a longer 6th gear, which I had felt unnecessary for my usage.

3. As stated the factors for top speed are power and CdA (provided the gearing is correct). I did all the calcs years back and whilst Cd figures are available, frontal area is harder to find. Also many of these claimed figures are not accurate, just as claimed weights for sports cars are often way out (anyone weighed a Ferrari recently).

4. Most cars vary relatively less in Cd or frontal area, in comparison to the variation on power. So it's a lot easier to simply fit 800bhp in just about any car than to find more aerodynamic cars. So the answer will most likely be whatever turbocharged car can be cheapest to tune to 700-800bhp. Hence why big Mercs, RS6 or 911 Turbos (pre recent price increase) are the most obvious.

Edited by Guyr on Tuesday 21st March 17:21