Hi all,

Some of the 'kart track' layouts are quite a blast. I think there is something quite weird happening at mid to high speed in the MRT5. Going fast in 1st gear is about the speed where accelerating really wants to make the car oversteer. The 'push' caused by changing to 2nd without lifting is often enough to cause oversteer that violently snaps into the opposite direction. But even in 2nd or 3rd gear there is still enough power to easily cause a snap snap snap / death kind of thing.

I find this VERY weird as at slightly lower speeds the little car had a far greater tendency to understeer on power.

What is going on here?

Yes it is weird. Also, the MRT5 engine I think has its peak power WAY to low. It is supposed to be a high revving street bike engines which have the max power/torque near the redline.

EDIT: Did a little research and came up with this...

The Real life MRT5 has these specs -

1997 Yamaha YZF600 engine. Garrett Turbocharger


85 HP with 4 32mm carburetors
75 HP with air intake restricted to 19mm.


The actuall bike the engine was taken out has these specs -


Horsepower: 94.6 bhp @ 11,000 rpm
Torque: 47.72 ft-lb @ 9500 rpm
Fuel System: Normally aspirated by four Keihin CVKD36


And the LFS MRT5.


Horsepower: 64 bhp @ 7894 rpm

Torque: 51 lb-ft @ 5071


Yah, I think the MRT5 in LFS is very underpowered.

It's not stock Yamaha engine,

http://forum.rscnet.org/showthread.php?p=950827#post950827

Quote from TravisS :

The cornering speeds will be pretty massive, decent acceleration as well. Top speed is less than impressive, a tad over 100 MPH, thanks to a choking 20 mm restrictor.

There was someone from McGill giving even more detailed info about it but I can't seem to find it (also RSC search system isn't making it any easier ) (not FlimBoyz - Simon Lemire, there was someone besides him)

Anyway, I recall him saying additionally to other mods they made to the engine, that they put the turbo in to get the max power/torgue even lower.

In autox the acceleration and power coming on early is much more important, than high power on high revs.

TBH it's a very simple piece of engineering built with little science behind it when compared to modern racing cars, my guess is they'll be using a ladder chassis or maybe a small space frame coated in fibre glass, but I'd really dobut it's anymore than that. I can understand the engine revving a lot lower than in a bike when it's being used for autocross, even larger 1000+ cc. bike engines in near standard, naturally aspirated form in the back of single seaters will rev to maybe 150 bhp @ 9500 rpm.

You simply cannot compare a bike engine in a car to what it's like in a bike.

As for the handling of the MRT it's unstable over about 40 mph because it was never designed to go any faster than that.

Well, I don't really care about how accurate the engine is modelled (and posted this before finishing my reply?!)

Anyway, the power to weight ratio isn't that extreme, the car has slick tyres and the tiniest 'weaving' at speed makes it oversteer. I actually think the low weight 'extreme' might be highlighting the / some physics engine troubles perhaps? At 222hp/ton vs 250 for the Fz50 just to give some idea on the power. Of course the lack of weight will make it a lot more nervous but somehow, at guessed yaw angles of only a degree or 2, is the acceleration force enough to make the rear tyres overtake the front?!

The Formula Student (English equivalent of SAE) car at my university is anything but simple. It's a molybdenum steel space frame chassis, fully finite stress analysed. The body is, now, GRP, although experiments with Carbon Fibre monocoque's were taken for the last two years. The suspension is deisnged from stratch and again fully analysed and tested.

The cars are designed to be very short wheelbase, andbe very unstable so that quick direction changes are obtainable. In real life, apparently, it is quite easy to flick around and catch it, but in real life the 'seat of the pants' effect makes catching slides a natural occurance.

As for the engine, the restrictors do tend to push the power band further down the rev range (although perhaps not as extremely as LFS's version), even with turbo charging.

I don't think there is anything seriously wrong with the MRT that a good setup, better low speed tyre physics and slightly more accurate engine modelling couldn't cure.

Quote from tristancliffe :

I don't think there is anything seriously wrong with the MRT that a good setup, better low speed tyre physics and slightly more accurate engine modelling couldn't cure.

Actually what is being said is the opposite, I have a great laugh drifting the MRT5 around tight autocross layouts, it handles like a dream. But even at something like Fern Bay Club, it's very nervous on the straights and high speed bends. But if that's just an accurate property of the vehicle, then so be it. It's still a million times better than it was in v0.3.

No intention to belittle them but they really are still a low tech short wheel base car with a lot of power (220 bhp/ton power/weight low? What planet are you from?) and don't weigh anything. So I'd have said they are fine in LFS, you need a set that's been setup for track use (ie. not a standard one). They aren't built to race on tracks therefore they have no stability at high speeds, like you build longwheel base sports cars for high speed work you build short wheel base rally and autocross cars to change direction very quickly

The McGill team did mention how they had to 'detune' the engine
to get the turbo working well (not to blow the engine i suppose)
and to get that power down low.

Quote from Niels Heusinkveld :

Hi all,

Some of the 'kart track' layouts are quite a blast. I think there is something quite weird happening at mid to high speed in the MRT5. Going fast in 1st gear is about the speed where accelerating really wants to make the car oversteer. The 'push' caused by changing to 2nd without lifting is often enough to cause oversteer that violently snaps into the opposite direction. But even in 2nd or 3rd gear there is still enough power to easily cause a snap snap snap / death kind of thing.

I find this VERY weird as at slightly lower speeds the little car had a far greater tendency to understeer on power.

What is going on here?

the simple answer (I know, i'm always stating the obvious:tilt is NOT to keep you're foot flat while shifting, you wouldn't do it in a real car so don't do it in LFS.

the MRT is a very snappy sort of car to drive, like the chaps say, it's supposed to be, try running the car on road tyres (if you got slickmod) to get a better feel for whats going on, road tyres do give you a more progressive action than the R1's currently on (tyres made by loctite not cromo) but go easy and tweak slowly as you go to get a nice freindly setup (soften it all to start with especially the rear) and once you're pushing it hard all the way round with nice predictable moves, switch back to slicks and gradually make the set more aggressive. it works for me

I still shudder at the memories of trying to race this thing in endurance races in S1, oh the horror

Quote from tristancliffe :

The Formula Student (English equivalent of SAE) car at my university is anything but simple. It's a molybdenum steel space frame chassis, fully finite stress analysed. The body is, now, GRP, although experiments with Carbon Fibre monocoque's were taken for the last two years. The suspension is deisnged from stratch and again fully analysed and tested.

Thanks for mention that, you are completely right. Same situation over here And btw, we also have 100 % anti-dive and about 60% anti squat - i wouldn't say that this sis simple supsension engineering. Maybe the other way around, i'm not really sure...