To build or not to build?

[AntonUK]

Hi Fellow Petrol Heads,
I currently run a highly modified Mini Clubman Estate ((some old photos here)). Its runs a 1380cc, race head & Cam, megajolt, 45DCOE, straight cut gears etc etc... but tbo its not quick enough. Having always wanted a Westfield, Caterham, Lotus 7 kinda car, it has led me to this site... I have been reading your forum for a while now.

What I really want is a silly quick car, 250bhp+ that's fairly cheap to keep and has the potential to tinker with it some weekends then drive it to a track the next and have some fun with it

What I would really like to know is if the plans I have are viable. I'm planning a car based on a locost/haynes chassis, Fuel injected 1.8 zetec lump with a single turbo hanging of the back of it. Having built the mini, I have the tools and capability, there is going to be a learning curve with the fuel injection and but that's half the fun.

Are things like brakes, diffs, clutches available to handle this kinda thing? or will it be custom stuff?

Comments / Opinions most welcome?

Anton

[Talonmotorsport]

hello Anton, the thing you need to remember about the 7 type car is that it only weighs 600-750kg so you get a better power to weight ratio than a turbo 1.8 zetec in say an escort. You might find that a 2ltr zetec running 40 or 45 webbers or even throttle bodies with 3d mapable ignition may well give you a very reliable 220-240bhp with better all round traction. I think your bigest problem with that much power might be finding the right size wheel and tyre that are narrow enough for the low weight of the car but grippy enough to make use of the power.
As for the clutch,gearbox,diff etc it's all made to push a car weighing 1200-1600kg along the road with 110-200bhp so a car weighing nearly half that it'll be more than capable of handling the extra power. The brakes I would have thought maybe a different matter. Make a heavy car go faster you need bigger rotars and monster calipers but in a light weight roadster the standard calipers may well be up to the job with added drilled disks and green stuff pads.
I hope what I've said is more or less right I've been playing with grasstrack racers for 7 years and have found the breaking point of most things along the way.

[HandyAndy]

i,m hoping that my car will be approx 550kgs in weight but am only using the 1.8cvh engine to start with then in time change to a 2ltr zetec on bike carbs so the power to weight ratio should be quite exciting

andy

[frankie boy]

HI Anton
I am in the progress of building my second roadster and will be going down the 20L zetec SE route with java throttle bodes, Fast road cams ported head. I have thought about the turbo but think it would only make it good in a straight line. These cars can become very twitchy on the corners so the thought of a turbo kicking in bring shivers down my spine. A well balanced car with 165 to 200 BHP to me will make a good fun car for road and track.

[AntonUK]

Thanks for all you comments guys, im glad my thoughts are on the right track.

I think with a well setup suspention, and suitably sized turbo issues such as lag and "twitchieness" etc can be minimised.

I assume geometry is adjustable? Castor, camber etc?

I just put 12month MOT on the mini, so its ready to sell but tbo i think i might get more ££ for it in pieces.

[alga]

Camber: of course. Castor: no, it's set in the geometry of front wishbones (and uprights).

[AntonUK]

Hmmm interesting, might have too look at a mechanism to enable the adjustments of front castor? or is there a reason its not adjustable by standard?

[Chris Gibbs]

There are several reasons really. The Sierra upright isn't ideal, the offset mushroom introduces some mechanical trail to help self centring, and people think that you can just add caster (by moving the top wishbone backwards or the bottom one forward) to give more self centering.

It's not that simple.

All suspension design is a compromise and the price you pay for increasing caster in this way is that you move the contact point of the tyre (When turning) to the outside of the wheel, eventually the contact patch can be on the sidewall. This causes "flip/flop" steering, where the steering is fine in a straight line but as you turn the wheel you reach a point where the wheel is pushed into the turn giving very odd feeling steering, almost like having a left and right switch.

I suppose the reason it's set is because it's right, that might sound a bit strange but I work on "a little knowledge" principal, which means that most people want the car to handle in a neutral way and don't have the experience or knowledge to adjust the caster and get good results. Now some builders will have that knowledge and it's possible to make the caster adjustable by using bigger brackets and swapping spacers either side, it was my judgement that it wasn't something that was necessary for most builders and it was a potential minefield for the inexperienced.

If you are going to alter the suspension I'd recommend you use a program like "Susprog" and check your mods, it can be very unpredictable.

Cheers

Chris