718 replies to this topic

[mini25]

i LOVE that interior man

[Ade]

Fancy one on the R1 ?????

Lol I fancy Cameron Diaz aswell but that doesn't mean I'm gonna get her!!!

To be honest I'd love one but a touch expensive at the minute....

[F1 Mini]

Sorry Angelina Jolie Has My Heart.....

[Jammy]

I'd prefer the Starksy and Hutch female threesome of Carmen Electra and Amy Smart....

[Mini-Dave]

Hey, we want some more pics ?!?!??!?!! :D

Keep up the good work, and get it finished !

Dave

[4WD]

It's been interesting reading through your development. I'm looking forward to seeing it all come together.

I have a few comments and questions...

1. Acceleration - I think your going to have an awful lot of trouble accelerating as fast as you predict / hope, ie McLaren F1 rivalling. Generally a supercar has a very heavy midmounted engine, so that when it accelerates this large mass is forced over the rear wheels via g-force, so creating a huge grip on their massive rear tyres. In your case you don't have much mass at all - especially near the back, plus limited rear tyre contact area, so I think your really going to struggle. I know you have traction control but all that will do is reduce maximum output to compensate for the lack of available mechanical grip. What it won't do is transfer 100% of the available peak power, as most supercars would be able to do. Also the limited suspension travel must hamper outright grip. So your effectively only going to be able to use a smaller portion of the output power and theoretical bhp per ton.

2. Vmax - What do you calculate your top speed to be? Every bike engined car I've seen so far has a top end around most hot hatches, ie 150mph max. I presume this is because a tiny engine is used with a very narrow peaky power band, therefore naturally has low torque. This lack of torque can only be compensated for with low gearing; even more so as the engine is not pulling a light bike, but a car at four times the weight. Thus the low gearing will dramatically lower the top speed potential.

Also what is the cda? I know a guy with a 500bhp 911 turbo (like the ruf yellowbird) who has a theoretical vmax of 225mph due to the gearing. However in reality it will only reach 190 as the shape is not very slippery. I suspect the aerodynamics of a mini are akin to a brick so this must have a big impact on the theoretical vmax.

3. Handling - I have heard that most rear bike engined mini's handle very badly indeed, particuarly referring to the zcar conversions. I notice your using dedoin to hopefully improve on this, but I am still concerned for your handling. It seems to be in development as you are building, rather than being designed from the outset by a race engineer. Does your design include any way for someone to alter a lot of the settings to dial in different handling characteristics if required?

4. Evaluation - When the project is finished I would be interested to hear if it was sucessful by way of hearing your lap times on track. Do you have any particular track or times in mind as a target?

Thanks for all the info I await. I admire your dive in approach and it makes great reading

Paul

[R1minimagic]

A couple of points

2. Most bike engined cars wouldn't even get to 150mph, the top speed is more likely to be 120-130mph as they will be geared for maximum acceleration. Top speed has nothing to do with torque, it is only peak power that matters.


3. I don't know who told you that the bike engined minis handle 'very badly indeed'. My mini is at least 5 seconds a lap faster around castle combe than my lotus elise and that is with only 3/4 throttle and the back brakes locking up at anything like moderate braking into a bend. With full power and the other mods I have done since then, I estimate more likely 15-20secs a lap faster.

Edited by R1minimagic, 22 October 2006 - 09:06 AM.

[4WD]

2. I realise torque has more to do with acceleration, however top speed still has a link with torque. Higher torque allows longer gearing, which allows a higher vmax. It's the area under the total power curve, not just peak bhp numbers that count. 450bhp is an impressive number to band about but a circa 200bhp hatch back would have a faster vmax. Never mind a McLaren F1! It comes down to torque and gearing.

P.S my radio control car has about 1500bhp/ton, but it's not very fast vmax

3. Some people who've driven them

Edited by 4WD, 22 October 2006 - 09:21 AM.

[R1minimagic]

There is no way a 200bhp car will have a faster Vmax than a 450bhp car unless the gearing was ridiculously low, which there is no need for. The gearing is unlikey to be 2.25 times the ratio!!

[4WD]

That is precisely why torque needs to be considered. Bhp is one side of the coin, but not the whole story. That is why a lot of diesels are so quick with only small bhp. Why? Because they have a high TORQUE. Examples:

BMW 320d, bhp 163, VMAX 140
BMW 535d, bhp 272, VMAX 155 (TORQUE 560!)
Audi S3, bhp 225, VMAX 155

P.S look at some stats:

http://www.bmw.co.uk...t-bmwuk,00.html



What is the torque of a holeshot 450bhp engine? What is the gearing? Therfore what is the theoretical vmax?

Edited by 4WD, 22 October 2006 - 09:43 AM.

[R1minimagic]

I agree, but i thought we were talking about top speed??

My argument was that if you take an 'identical' car with 'identical' gearing then the torque doesn't effect top speed it is only the power output. For example you could have an engine with 200bhp, 100lbft, 15000rpm and another engine 200bhp, 200lbft, 7500rpm, they will both have the same top speed. However, the way they get to that top speed will be different.

I think your argument is more along the lines of take the same engine, add more torque, you will get a higher top speed, which is also correct as long as it still has a similar max rpm!

Also, difficult to compare modern vehicles as they are usually limited top speed by the ecu.

I would imagine a busa turbo engine would have at least 200lbft of torque if it is going to make 450bhp, nit sure on the base case engine figures but guessing around 170bhp, 100lbft, 10000rpm??

[4WD]

Oh I agree the *way* they get to their vmax will be totally different. The busa will screem it's tit's off and be at or around it's 140mph max in no time at all. However the example diesel bmw will quietly, eventually, catch up and overtake, due to the higher vmax. Despite having half the bhp and four times the weight. Given enough room of course! This is why I mention torque as so many people seem oblivious to it's importance.

At the end of the day all I wanted to know was what lap times will a busa mini post up on well known tracks. Obviously it will be great on gokart sized tiny tracks, or 0-60 drag sprints, but what about the real world proper size tracks? I wonder what sort of time it would manage at the 'ring, with long straights and less than mirror perfect surfaces. This is why I asked about the torque, handling and cda. This way a design like this can be compared to different cars, like the evo, radical or even F1 if you really insist!

Real life laptimes are what I care about. Just a friendly enquiery

[R1minimagic]

The gearing issue is a bit more complex i think with bike engines as they tend to have more gears so that the torque is less of an issue.

I think a turbo busa mini will do well on the long straights (e.g. Snetterton, Castle Combe, Donnington, etc) as you have lots of torque, power, bhp/ton, and gears! But i am not sure how well it would do on the twisties as it might be off boost all the time!!

[4WD]

Yes, turbo lag is a big issue. That is why in the real world, the factory 350bhp Evo is quicker than the 400bhp model. Much to the annoyance of those who spent more for the pub bragging rights. The only time the peaky nutter turbo lagging evo engine is faster is on a dead straight drag strip. But of course were not yanks are we. We have corners to contend with.

Also notice how Ruf tuned porsches are faster than those with more power in the real world. Ruf have a huge amount of torque, spread nice and wide across the full power band where it counts.

P.S

Due to all of above I suspect an ultima will kick sand in the busa mini's face all day long.

[R1minimagic]

Yes those type of things used to be developed with a huge turbo for rally homologation purposes but then they use an anti-lag system to keep the boost up, which is fine for rallying but not much use in a road car!! I think they are banned now. Things like the impreza turbo, escort cossie had a limited run with a big turbo then went to a small turbo after they had built enough for homologation.

However, VW has just launched a golf with a supercharger and a turbocharger, the supercharger feeding into the turbo, could see a lot more of those in the future I think. Lots of power and torque from only a small engine, good on economy too.