Front heavy, but light front wheel drive, ideas and help!

[Jon Doe]

Ok, so I have done a few trackdays in my kit car, its an Onyx Firecat 1.3 (Uno Turbo).

So its front wheel drive and the weight is all near the front, it suffers from plenty of understeer.

Sadly the TSW wheels on it are 14" and I think that limits what tyres I can get for it.

It has trouble getting the power down due to the huge rush of boost, so I am going to take it down to a standard IHI turbo to get smoother delivery and less turbo lag.

So my question is this- the car has bad weight distribution, but is pretty light. Should I try the battery in the boot? The thing I cant get around in my head is- would the better weight distribution help the handling or would it leave less weight and therefore let the wheels light up more easily at the front, therefore outweighing the benefits?

What else can be done?
Some sort of aerodynamic fins? Also I cant think of anything more useful than moving the battery.

Better tyres would be excellent, but I dont think they do 888's or T1Rs for a 14" (or maybe I have looked in the wrong place?). Its the things aside from tyres which I would like some advise on.

Also- regarding aerodynamics and soft tops- having the soft top up or down- does this have particular benefits or issues on track? MX5 would be a good reference.
Thanks in advance!

[groomi]

I use 14" 888's on my Westfield.

Moving the battery alone won't make much of a difference but it's a step in the right direction - what else can you change/move?

[Elderly]

And Yokohama A048-R in 14".

[rdjohn]

Is it possible to move the driver lower and backwards at all?

Also have a look at a few of the tricks BTCC cars use.

[Jon Doe]

Driver could be a little lover on a bucket seat but it is a Corbeau (spelling) seat which is as low as it can go and gear lever would go out of reach if further back- but that would be a great weight movement to have the driver further back, good idea.

Thanks for the tyre info, any advise out there as to aerodynamics?

[groomi]

Regarding aeodynamics, trackdays are the best place to experiment with this. Go out with the top up, nail the last corner onto the straight and look at what speed you get to. Come in and take the top down and repeat. Which is faster?

As far as making aero modifications, don't bother chasing downforce - all you'll do is increase drag and slow the car down. Instead, are there any nasty areas that can be cleaned up? If the hood is down, can you fit a half tonneau cover over the passenger side to clean up the airflow? Maybe make some rear wheel spats?

Have you got any photos of the car so we can see what you're working with?

[Jon Doe]

They look a bit like a confused TVR built by a Ukrainian freeze dried piss bat.
Ok, this is the nearest pic (not mine). My Firecat is around 40mm lower than this:
http://www.firecat.org.uk/P1000324.jpg
and this is fairly similar at the front:
http://www.motorbase.com/uploads/candc/2009/05/22/...

Edited by Jon Doe on Saturday 23 January 10:30

[BJD]

If the front hubs are the same as the Strada/Ritmo (its likely that they are similar) what a lot of the racers used to do was stick a smaller diameter bolt through the top hub fitting. This gave more neg camber at the front, combined with a degree or so of steering toe out, and it significantly decreased understeer.

[Big Ashy]

I pesume you are struggling getting the power down on the exit of 2nd gear corners and the like? Just my two penneth, but some consideration should be given to a decent suspension upgrade if you haven`t done so already and after that, a LSD diff would also benefit if such an item is available?

Regarding aero upgrades, as said before pretty much everthing is going to slow you down and will only benefit the cars handling at very high speed.

[Jon Doe]

BJD said:

If the front hubs are the same as the Strada/Ritmo (its likely that they are similar) what a lot of the racers used to do was stick a smaller diameter bolt through the top hub fitting. This gave more neg camber at the front, combined with a degree or so of steering toe out, and it significantly decreased understeer.

I think I know exactly where you mean, there are two bolts and that seems to make sense.

[Jon Doe]

Big Ashy said:

I pesume you are struggling getting the power down on the exit of 2nd gear corners and the like? Just my two penneth, but some consideration should be given to a decent suspension upgrade if you haven`t done so already and after that, a LSD diff would also benefit if such an item is available?

Regarding aero upgrades, as said before pretty much everthing is going to slow you down and will only benefit the cars handling at very high speed.

Yes about the second gear out of corners problem, part of the problem is this 'uprated' turbo. It gives the ability (if you let it) to produce loads of bhp but also creates lag. So even with it tuned down (well you have to) you put your foot down and the power through the range is not well distributed. So smoothing this out should help.

The shocks are adjustable and I know so little about shocks that I didnt fiddle with them at all, any basic theories welcome.

[rdjohn]

Very pretty car.

I suppose that it must weight 750kg with 150bhp, so I am a bit surprised it understeers as badly as you suggest; particularly with the lag. perhaps your problems are fairly basic.

Are your tyre pressures too high? I would have thought that soft rubber at about 24psi would make a huge difference, assuming your wheels are not too skinny.

[Jon Doe]

rdjohn said:

Very pretty car.

I suppose that it must weight 750kg with 150bhp, so I am a bit surprised it understeers as badly as you suggest; particularly with the lag. perhaps your problems are fairly basic.

Are your tyre pressures too high? I would have thought that soft rubber at about 24psi would make a huge difference, assuming your wheels are not too skinny.

Thanks for that, all these things together should make a difference.
Its these kind of hints and tips that I need to get onto.

I think the stock weight for these was 610kg but this is probably more like 650. The HP is unknown, when i first had it, the previous owner had it running at 1.2 bar (the turbo can give it 1.3!!) and has a dyno printout for 204bhp. The problem was that the power was nothing, nothing, is the tur... WALLOP. It ate its last clutch and if you put your foot down in the dry, when the acceleration kicked in hard at 5000 revs, it would then read 7000 revs until the tyres gripped again. The result was that with such a narrow power band, the benefits of the 'amazing' power were all but lost. Reading forums about Uno Turbos, realisticly you should stay below 1 bar, at around .8 or .9 it can still light up the wheels but the tyres dont actually have much rubber on the road, probably better as a wet tyre, they are A359's. http://www.elitedirect.com/Tyres/images/Treadpatte...
Peoples opinion seems to be mixed on these but people who like them mostly are road users.

Another main problem is the driver- I am not a pro, so I dont make the best way round a track yet getting the weight into the right areas.

SO, replace driver, let out tyres, adjust camber, change tyres (realising that letting them out earlier in the sentance was pointless), move battery to back, change to appropriate turbo size.

Edited by Jon Doe on Saturday 23 January 16:45

[t11ner]

You may have hit on a major area for improvement there; get some training, learn how to get the car as straight as possible on the exits etc to maximise traction and you'll probably do much better.

Also, as has been suggested above, if you are running an open diff then you'll always struggle - especially in the wet!

Steve H

[iguana]

A539s are a cracking track tyre for longevity- I've done circa 1300 'ring miles this yr & fronts are still well legal! 180bhp 900kg track golf & its not driven gently, rears are as new!

Naturally as a result of this they aint the stickyest tyre around & will of course make any natural understeer worse.

Never driven one of yours but for the Golfs to cure under steer normally=

-Run larger foot print tyres 7j with a 195/50 /15 or 205/50/15 is ideal
-Run stiffer rear springs or a thicker rear arb, narrower rear wheels/tyres also play with tyres pressure- harder rears
-Wide track the front subframe



Also drivers make amssive diference rember the clarkson/kershaw in an Elise top gear bit,

[rdjohn]

t11ner said:

You may have hit on a major area for improvement there; get some training, learn how to get the car as straight as possible on the exits etc to maximise traction and you'll probably do much better.

Also, as has been suggested above, if you are running an open diff then you'll always struggle - especially in the wet!

Steve H

I was belatedly thinking about this; it strikes me that you have quite a nice road-going car and not a trackday special - so firstly you have to decide what you want.

My guess is that out-on-track the guys with a stripped-out 106 are actually having as much fun as the guys in GT3s, though in the pits they may be a bit envious.

Driving "what you own" is the fun of a trackday; you are not trying to be better than anyone other than yourself - so training and mastering the car you own is the first step to enjoyment - cutting the power will ultimately disappoint on the straights. Sitting with an experienced instructor will probably help you appreciate that smooth unflustered movements is ultimately the fastest way round a circuit.

With your car as it is, do all you braking in a straight line; before you turn-in gently touch the throttle to start to spin-up the turbo - never jump from the brake to full throttle; caress the throttle through the corner; only once you are straight smoothly open the throttle to max revs.

Only when you have mastered the car as it is, should you think about radically changing things as you will not be able to understand the improvements you have made (other than in your wallet). Personally, I do not think that I would spend money on much else other than sticky rubber; it really does make the biggest difference.

Beyond that, I would probably chose to buy a more track oriented car, but, again, the main thing is to enjoy what you have first.

[Jon Doe]

All good points. Yes the A539's could be replaced by stickier tyres but I think I will try and learn more about driving before changing them, wear them down first!
The turbo I will change, I already have the standard one sitting in my shed and having the silly one and not using its potential is also silly.

Interesting point about the tuition as the last time I took the kit car out, it had a few problems by lunchtime. So I took my Saxo VTS back after lunch and booked some tuition in the afternoon. It was an absolute revelation and i was taught a whole bunch of things reflected in this post. So, to be fair, the last time i drove this car was before I learnt to drive! The throttle control is what i knew nothing about before that lesson and also how it helped the weight transfer.

Like you say, its not about the out and out speed on the track day- I really enjoyed my saxo, full of seats and standard suspension. The firecat is my semi dedicated track vehicle though.

[slipstream 1985]

better quality rubber on the front than on the rear?

[racingsnake]

Lower front tyre pressure & increase rear tyre pressure might alter the current balance.