245 replies to this topic

[thespikeyone]

a wee update 

 

fixed the oil pipe and filled her up with oil and she fired up no problem, i am certain I can hear a  knock from the bottom end but it goes after a few seconds anyway took it to a small show at Dumfries aviation museum and back and it ran fine even gave it a bit of a blast on the way home and engine was fine.Think I will need to order some new sprockets tho the gearing is far too short for me and tops out at around 96MPH.

 

The other issue I'm having is a floaty front end which gives quite a bit of understeer when cruising (grips and goes round corners great if you are accelerating around the corner but if just sitting at constant speed will underteer badly)  going to play with geometry set up to get it better.  If anyone has any tips on this please feel free to let me know.  Thanks

[duds100]

I can try & help you with the gearing & suspension setup.

 

For gearing;

 

What diff ratio are you running?  (3.1 or 3.4 CWP are the most commonly used in the Pro-mo kits) & what top speed would you prefer it to be geared to? 

 

Suspension;

 

Are you on coilovers or rubber cones? Have you had the car aligned yet? what tyre pressures do you run? 

[thespikeyone]

I can try & help you with the gearing & suspension setup.

For gearing;

What diff ratio are you running? (3.1 or 3.4 CWP are the most commonly used in the Pro-mo kits) & what top speed would you prefer it to be geared to?

Suspension;

Are you on coilovers or rubber cones? Have you had the car aligned yet? what tyre pressures do you run?

.

Cheers mate really appreciate it.

Not sure what ratio the diff is, I didn’t specify anything other than the quaife lsd when I ordered the kit. Is there anyway to tell?? And I would like it to top out around 130mph if possible.

I’ve got hi lo’s With spring conversion instead of rubber cones. I have had the car aligned but they didn’t do a very good job and couldn’t dial in half the settings I wanted so will need to get it done again but I am trying to get it as close as possible at home with caster camber gauge and trakace. I’m running 7 x 13s at 30 psi. Open to any better ideas tho.

Thanks.

[duds100]

So I've taken an educated guess and I think you are on a 3.4 CWP as this is what Pro-Motive usually supply for a 13" wheeled car. I've also assumed you are on 175/50r13 tyres.

 

Looking at my calculator I think you are probably running a 17 tooth front sprocket (engine jack shaft output), and a 17 tooth diff sprocket. 

 

This means your current gearing gives something like this with a 97mph Top speed:

 

the spikey one 97mph top speed by Dudley Waldron, on Flickr

 

if you changed to an 18T front sprocket & a 14T Diff sprocket your gearing would be like this with a theoretical 125mph Top speed:

 

the spikey one 125mph top speed by Dudley Waldron, on Flickr

 

Now the front sprocket is obviously a Yamaha R1 sprocket, but the rear diff is actually a Suzuki Hayabusa Sprocket. So make sure you order the right ones. When you fit them you might have to fiddle with the chain to get the tension right. 

 

As for handling. This is a bit of a minefield. I don't have any experience with the spring conversion but by most accounts I have heard they are not a good performance upgrade. I suggest you replace them with some "red dot" uprated rubber cones that minispares sell. Also it is important to check you have enough damper travel. For example at the front, you can do this by;

 

1) Taking off the damper and measuring the distance between the top & bottom bolt hole of the damper with it fully open (pulled out) and then fully closed (push it in as hard as you can).

2) Measure the distance between the top and bottom mounting bolt on the car with it sat at it's normal ride height. This measured value is your damper open length at rest.

3) Check you have at least 30mm either side of the "open length at rest" when referencing your open & closed lengths that you measured on the damper, this will confirm is you have enough bump (in) & droop (out) damper travel. 

 

 

From there I would spanner check the whole car and set tyre pressures to 28 PSI all round. If you have hi-lo's, try and set the rear of the car about 25mm or 1" higher than the front. Best to measure the distance between the sill lip to the ground to get an idea of this. 

 

Then I would take it for a GEO setup. (you could do this with your coil springs still fitted, worth a go)

 

As a general guide for 13" wheels;

 

Front;

 

Bit of toe out

+4° castor,

-1° camber  

 

And for rear;

 

Bit of toe in 

-0.5° camber 

 

Hope this helps. Good luck!

Edited by duds100, 26 September 2018 - 10:35 AM.

[thespikeyone]

Thanks. Will have a play with it at the weekend.

[thespikeyone]

Right so I decided to ditch the coil spring conversion and fit some mini spares red spots and what a difference!!! the car feels 100 times better and less death trapy!!!!!  also fitted a 14t diff sprocket which has made the gearing a bit longer and more usable.

 

just want to say a big thanks to duds100 for his help   

[Bat]

Hi,

I think you'll find more grip with the tyre pressures a bit lower.

Cheers 

[duds100]

Yes, quite possibly... I think 6x13 sportspack mini recommended pressures were 28 PSI front. I run my mini on 10x5s at around 24 PSI front.

 

28 PSI would be a good start point. From there I would bleed out a little bit and see the effect. Less pressure = more grip but the danger, especially with a wide contact patch on 13s, is that running under inflated during lateral load the tyre will roll to the outer edge and this will give less grip mid & corner exit. It's a balance between pressures, camber & castor for traction & cornering grip.

 

If possible use a pyrometer on the tyre to measure the temperatures across the tread after a good blast. I take 3 readings, ( centre & 1" from each edge) you want the temps to be within 10% of each other for the whole width. This will give an insight into how the tyres are being worked.

[Bat]

Hi,

I'm guessing the front end is a lot lighter than a normal mini now so less tyre pressure would be needed?

As you say work down gradually.

Cheers 

[Gribovphipt]

It is the valuable information

[duds100]

correct, I guesstimate it's around 30kg lighter, pro-mo kit Vs A-Series 

[thespikeyone]

right so I had it out for a couple of blasts, one of which ended up with bit of off roading!!! (driver I was overtaking decided he was over taking the tractor while I was beside him!!!!) anyway.

 

findings:

 

I think I may have gone too long on the gearing, right up the top end in fifth change to 6th and there is no/very little speed increase and engine struggles to get past 9500 rpm in 6th.

 

Not sure if I am down on power or if the 14T rear is just too tall for 13's thoughts?

 

Anyone got a decent map for PC3?  Running the pro-mo supplied k&n filter and straight through exhaust.

[duds100]

Try going up a diff sprocket, or down a jack shaft sprocket. Do one or the other and this will shorten the gearing slightly.

 

Pro-motive injection R1's are about 118bhp stock, or 125bhp at the wheels mapped. Carb's will be similar top end power stock/dyno jetted

 

With stock R1 power, 13" wheels, wide arches & mirrors I guess your potential top speed will probably be around 115-118mph. Gear it for 118mph in 6th at 10,600rpm and you won't be far away. 

 

Mapped, and with correct gearing you might hit 120mph.

[RoryN]

My race r1 mini at 500kg with me in it can pull 116mph no problem at the limiter over the 1/4mile.
Mines isnt a promotive kit. I run a 15t - 50t setup on 13 wheels.

Rory

[duds100]

My race r1 mini at 500kg with me in it can pull 116mph no problem at the limiter over the 1/4mile.
Mines isnt a promotive kit. I run a 15t - 50t setup on 13 wheels.

Rory

 

RoryN

 

The beauty of a light car & 6 sequential gears! 116mph is still a very impressive terminal. Is it stock power?

 

I have seen 125mph GPS at just shy of the limiter in 6th in mine. It also weighs around 500kg. With this gearing on 165 road tyres I managed a 13.2sec with a 104mph terminal on the 1/4 mile, going over the line at 11,200 in 4th gear.  I am more motivated to change some sprockets and have another go using all 6 gears after seeing your impressive terminal speed. This and some aero mods to clean up the turbulent flow underneath my heel board & partially block the front grille should hopefully see some tangible gains.  

 

thespikeyone

Be interesting to hear how you get on with some taller gearing. There are some good free GPS apps you can download to verify speed. I bought a speedo healer and then calibrated my R1 clocks so now they read GPS speed

Edited by duds100, 26 October 2018 - 10:02 AM.