Modified Power-to-Weight

[LowStandards]

My Scamp weighs roughly 500kg and will be getting a Toyota engine with 109bhp

No idea what that equates to in real word figures.

It does have the frontage of a house mind

[biturbo228]

Sept 19, 2019 15:37:47 GMT Frankenhealey said:

I once entertained starting a 1/2K-NASP club, i.e. 500bhp/ton naturally aspirated. No turbos, no chargers, no NOS. It would have been a small group.

Yeah I'd bet that's going to be an exclusive club. All I've got from stock vehicles is the Duratec Caterham Superlight and the TVR Speed 12!

Sept 19, 2019 16:59:13 GMT stealthstylz said:

Think a lot of it was whether it was tested to DIN standard or SAE or whatever. I know the Yank stuff was over rated compared to as it was in the car as they didn't test then with any of the other spinny bits that are related to the engine other than that what is needed for it to run etc. However some stuff was then massaged up or down further by sales people, for insurance or racing reasons usually.

Yeah absolutely. Some of the SAE figures were tested with open headers and suchlike too. Basically whatever gave the best figure. By and large Americans switched over in '72, but that also coincided with a whole load of changes for economy (lots of low compression stuff) so it's not easy to compare earlier engines. AMC changed over early though so they're pretty easy.

Us Brits gradually changed over from around the late 60s, but were fond of just outright lying on power figures. '150bhp' TR6s and '228bhp' 3.8 E-Types are closer to 141 and 180 respectively. Reliable net figures started in '72 as well.

The Europeans have by and large been honest with their power figures for ages.

The Japanese you have to be very careful with. They didn't start changing over to a net power rating until 1985, and some took a while to do it. Then they had their 'gentleman's agreement' stuff where nothing could be rated at over 276bhp, which just meant they all said their cars made 276bhp regardless of what they made.

Neat article about it here: ateupwithmotor.com/terms-technology-definitions/gross-versus-net-horsepower/

Sept 19, 2019 17:01:01 GMT sonus said:

IT has a Daimler 2.5 Hemi V8 that was rated at 140bhp from the factory fitted in the Daimler 250 V8 saloon. 195/65/15 tires, Jaguar e-type 3.31:1 diff and BorgWarner T5 gearbox.

Dude that's awesome! Brilliant little engines them, but I'd never seen one used in a swap before. Definite props for using one

Sept 19, 2019 21:07:23 GMT austinpowers said:

I don’t think my Trabant is going to scare any Farriers, but the engine has been modified from 26hp to 43hp.
And is now just below 600 kg.

Haha you're not wrong still, it's not the slowest car on the list! Woe betide any Mk1 Sprites or Hillman Imps that try their luck (provided it's not over a mile drag...). If you come across a hopped up Fiat 126 then you could be in for a really interesting race as you're pretty close all round with one of them

Sept 19, 2019 21:14:37 GMT mk2cossie said:

My ole girl weighed 1420kg, and managed a quarter mile of 15.8seconds with 175bhp at the flywheel.

Now makes 207bhp at the flywheel, but not been back to Santa Pod yet to see what improvements have been made!
Probably lowered about an inch from standard at a guess if that helps

Nice I've always liked those Granadas. Dead cool cars

With 175bhp you're right around 240zs, early PI TR6s, and E39 528is. Unfortunately, your car's not terribly aerodynamic and doesn't have the benefit of being teeny-tiny like some of the others here. The 528i will probably walk past once you get to about 70ish, but you'll stay neck and neck with the TR6 (much smaller, but worse drag coefficient). You'll comfortably pull away from the 240Z though. Although they're pretty small, they really do have an abysmal drag coefficient.

With 207bhp you're much better off. You're up with twin-plenum SD1s and series 1 E-Types one interesting one is a Mk1 Clio Williams, which despite being completely different in almost every way to yours sits and near as damnit the same power-to-weight and the same power-to-drag. So if you can pair yourself up against one of them at santa pod that would be very helpful

Sept 20, 2019 12:02:06 GMT mungo said:

Yeah, I'm out of legs at the end of a 1/4 mile let alone a full mile !!  and I'd deffo not want to be anywhere near the thing over 100 mph ....it's a deathtrap   (no seatbelts! ) 

Haha well, if you do feel like giving yourself a near death experience, you should be able to get to around 125mph

Sept 20, 2019 12:33:58 GMT LowStandards said:

My Scamp weighs roughly 500kg and will be getting a Toyota engine with 109bhp

No idea what that equates to in real word figures.

It does have the frontage of a house mind

So, that one might be a little tricky! Doubt I'll be able to find drag coefficient info on one of them, but let's guess that it's about the same as a Caterham 7. Is it about the same height as a regular mini too or a little lower at the cage?

[LowStandards]

It's pretty much a Mini Moke replica, I found a site saying the CD is 0.7


Means nothing to me

[biturbo228]

Sept 20, 2019 14:53:35 GMT LowStandards said:

It's pretty much a Mini Moke replica, I found a site saying the CD is 0.7


Means nothing to me

That is...not great

Still, weighing curse word all helps your power-to-weight with the Toyota engine will be right up there with 964 Turbos and E36 M3 Evos. Pick a rolling 1/8th mile drag and you should surprise them, even if you probably won't be able to crack 100mph flat-out in fact, your top speed is 49th from the bottom of a 2038-long list of cars, but your power-to-weight is in the top 20%!

If you fancy testing my power-to-weight-to-drag thing, then try and find a bone-stock 106 GTi and challenge them to a 1/4 mile drag

[johnthesparky]

This is interesting, thanks

got a UVA fugitive kitcar with VW beetle running gear.

Originally when we built it, it had a 40hp 1300cc engine in it.
We’ve swapped that for a 2007cc engine (don’t know power, I think 100hp is a very safe bet, and it may be as high as 120)
It weighs about 500kg

But I don’t know drag coefficient, the front is fairly pointy, but the cockpit is very open, so lots of turbulence I guess.

Would the drag not really affect the 1/8 mile as much, but becomes more important at speed?

[LowStandards]

Sept 20, 2019 15:20:02 GMT biturbo228 said:

even if you probably won't be able to crack 100mph flat-out i

I wouldn’t worry about hitting a ton, I think my balls would give out long before any theoretical top speed

[Darkspeed]

You need to factor the all up weight with driver - especially with Lightweight cars - so many bike engine kits rave about high power to weight figures but due to the light initial weight the driver skews those figures dramatically which is not the case with heavy but high powered vehicles

Like a superbike with 195Kg and 190BHP = 974BHP/ton But stick an 85Kg pilot on it = 678BHP/ton

Fisher Fury is the only car I have accurate weight and power figures for which is 515Kg and 195BHP - 378BHP/T = add a driver 85Kg and that's 325BHP/T add a 105Kg driver - 314BHP/T

Pub numbers gone from 500Kg and 200BHP at 400BHP/T to a more accurate 300BHP/T due to sitting honest john behind the wheel

It was still plenty quick enough.

Strato's figures are well documented - I hope to get Litton 2.7 rep under 1000Kg with driver and over 200BHP - 200BHP/T
Ginetta G27 4.5 goal is 700Kg with driver and 300BHP - 428BHP/T
G15 1.0 should be 600kg with driver and 90BHP - 150BHP/T
Gemini 1.6 700kg with driver and 105BHP - 150BHP/T
Gemini 2.8 760kg with driver and 150BHP - 197BHP/T

[giuliettaevo]

My 1974 alfa giulia has 0.34 drag apparently. It now has about 180-190 bhp and 400nm from a 10v jtd engine. It weighs 1070 kg with 1/2 tank.

Never really timed the performance but due to the torque it's pretty fast. I've had it over 210km/h.

Next winter i'll be swapping the engine for a 20v jtd which will end up with something like 270bhp and 600nm. This should make the car scary fast..

[mrbounce]

My Midas has a 1293cc engine which has yet to run, but if similar engine specs are anything to go by, should in theory have about 70-75 FWHP. It weighs (I think) about 675KG. It's more slippery than a Mini but I think it'll be restricted by ots gearing. 3.44:1 final drive on 12" wheels.

[biturbo228]

Sept 20, 2019 17:53:19 GMT johnthesparky said:

This is interesting, thanks

got a UVA fugitive kitcar with VW beetle running gear.

Originally when we built it, it had a 40hp 1300cc engine in it.
We’ve swapped that for a 2007cc engine (don’t know power, I think 100hp is a very safe bet, and it may be as high as 120)
It weighs about 500kg

But I don’t know drag coefficient, the front is fairly pointy, but the cockpit is very open, so lots of turbulence I guess.

Would the drag not really affect the 1/8 mile as much, but becomes more important at speed?

Neat hadn't come across one of those before but they look damn cool. Like the lovechild of a caterham 7 and a sandrail

You're also right, unless you're monstrously quick drag won't really affect an 1/8th mile, but is probably the dominant thing holding you back in a full mile drag.

Done a little research on weights for them, and will need to do some approximations. Let's say Caterham drag coefficient (0.62), 110bhp and 535kg (weights seem to range from 550-600kg, but we'll be kind). Can't seem to find height or width though so might need you to do some measuring...

Sept 20, 2019 19:08:40 GMT Darkspeed said:

You need to factor the all up weight with driver - especially with Lightweight cars - so many bike engine kits rave about high power to weight figures but due to the light initial weight the driver skews those figures dramatically which is not the case with heavy but high powered vehicles

Like a superbike with 195Kg and 190BHP = 974BHP/ton But stick an 85Kg pilot on it = 678BHP/ton

Fisher Fury is the only car I have accurate weight and power figures for which is 515Kg and 195BHP - 378BHP/T = add a driver 85Kg and that's 325BHP/T add a 105Kg driver - 314BHP/T

Pub numbers gone from 500Kg and 200BHP at 400BHP/T to a more accurate 300BHP/T due to sitting honest john behind the wheel

It was still plenty quick enough.

Strato's figures are well documented - I hope to get Litton 2.7 rep under 1000Kg with driver and over 200BHP - 200BHP/T
Ginetta G27 4.5 goal is 700Kg with driver and 300BHP - 428BHP/T
G15 1.0 should be 600kg with driver and 90BHP - 150BHP/T
Gemini 1.6 700kg with driver and 105BHP - 150BHP/T
Gemini 2.8 760kg with driver and 150BHP - 197BHP/T

You're absolutely right Darkspeed. I've got another little column that does power-to-weight with a 75kg driver (as per the newer EU regs). Differentiating which stated kerb weights include driver and luggage and which ones don't has been a bit of a challenge, but getting there. Will have a look at them in a bit...

Will need to do a bit more research to get some figures for the Fisher, but the G27 and G15 I've got some for already.

The V8 G27 is way, way up there with Superlight 7s and supercharged Atoms. With a 75kg driver you're around 991 GT2 RS figures! The G15 is pretty respectable too 205 T16 and Mk3 Focus STs. You're right about the driver effect with smaller cars as with a 75kg driver you're a little lower. Still sitting around Evo2 Delta Integrales and Mk6 Golf GTIs.

The drag is an interesting one on these tiny cars too. The G15's still not brilliant thanks to it's (admittedly estimated) Cd and modest power, but the G27 is pretty impressive. X308 XJRs, F-Type V6s and modern BMW M2s are around the same power-to-drag (and your power-to-weight is better). Those are all much slipperier, but are let down by massive frontal areas.

Sept 22, 2019 19:10:42 GMT giuliettaevo said:

My 1974 alfa giulia has 0.34 drag apparently. It now has about 180-190 bhp and 400nm from a 10v jtd engine. It weighs 1070 kg with 1/2 tank.

Never really timed the performance but due to the torque it's pretty fast. I've had it over 210km/h.

Next winter i'll be swapping the engine for a 20v jtd which will end up with something like 270bhp and 600nm. This should make the car scary fast..

Wait...JTD-swapped classic Giulia? How have I not seen this before? Please tell me you have a thread so many questions...

As it stands, the 10v (assuming 190bhp) is not far from a Megane RS 250 (and, despite the Renault being more modern, the Giulia has better power-to-drag!). Evo VIII FQ260s are another similar one, but just sneak past you on power-to-drag. Driver included they'll just sneak past you, but if their mate has a 9-3 Viggen you might scare him

with the 20v you're neck and neck on both power-to-weight metrics with a 4C GTA, and beat it for drag. Interestingly a similar thing happens with Alfaholics' 2300 Giulia saloon which is a little lighter, but has less power. You're also pretty damn close to where I think my PI-engined Spit will work out, but again will pull away neatly when the drag gets too much.

Sept 22, 2019 20:36:29 GMT mrbounce said:

My Midas has a 1293cc engine which has yet to run, but if similar engine specs are anything to go by, should in theory have about 70-75 FWHP. It weighs (I think) about 675KG. It's more slippery than a Mini but I think it'll be restricted by ots gearing. 3.44:1 final drive on 12" wheels.

I'd absolutely love to do the Mini Midas as I reckon that might be another giant-killer, but I'm having real trouble finding an estimated drag coefficient for it. Will do some more research...

[georgeb]

This thread could throw up some interesting results.

I won't bother with 225 (probably now 200)bhp, two tonnes, drag coefficient of a small hotel. It wafts...

Gonna bookmark for as long as it lasts all the same.

[biturbo228]

mrbounce Is yours one of the 70s Midases or one of the 80s ones with the round lights?

Sept 26, 2019 12:36:03 GMT georgeb said:

This thread could throw up some interesting results.

I won't bother with 225 (probably now 200)bhp, two tonnes, drag coefficient of a small hotel. It wafts...

Gonna bookmark for as long as it lasts all the same.

Ahem. You are not wrong!

Your drag coefficient isn't actually all that bad (0.38), but by dint of having the frontal area of a small barn it's coefficient of drag area is really not great :S

Interestingly, because of the power compared to other similar power-to-weight cars, you're not actually all that bad off. Similar power-to-weight as an MGC GT or a TR7, but because you need 225(ish) bhp to reach that, when the drag starts to take over you're be much better off. Feels very Range Rover that does. Awful drag, ludicrously heavy, but stick a big enough engine in it and you'll be quicker than you think

[tofufi]

How about this little beastie?



Around 1000kg I imagine. And running estimated 200bhp at full boost.

It's stealthy, I've surprised a BMW e46 330ci before

[v8ian]

My cortina was about 900kg with 330ft lbs and 310 hp, ran 11.9 @ 111mph, on a 3.9 rover, and don't forget, its Torque that gives acceleration, not HP

[mrbounce]

biturbo228 it's a Mk1 - one of the early ones based on the Mini (not Metro) and looks like this:

[froggy]

share.icloud.com/photos/0qO2xw8wwOyqws5VqIe-ipcHw

Men are worse than women when it comes to lying about weight . Mines 960kg with some fuel and driver . Pretty much the same numbers as an r500 Caterham and slightly slower to 50mph when the Caterham gets totally smoked (straight line obviously )