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Skinners Sprint Micra

Could you put a dint in to the brake booster? It's just an air tank as long as where the diaphragm goes stays round I don't see huge troubles. It could buy you some room although it'd be tight.

Relocate your brake fluid reservoir of you do angle it up?

Get rid of the booster altogether (more brake feel) or fit a remote brake booster most are fitted to the front brakes only so you'd need a front /rear split.
 
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Skinner_87

Skinner_87

Club Member
Bit of an update as iv not been on for a while.

CAD works done to adapt the throttle bodies. Basically it's going to be a downdraft setup now.

The bodies will be going off to Jenvey when cash permits.

Once the bodies and trumpets are back the low boost plenum design can start as well.

Struck a good deal to purchase Chris's turbo setup from him. I'm in two minds at the moment of what to do, bolt it onto the current CGA3 setup and run low boost or rebuild a CGA3 with corsa pistons for a lower compression build.

Cash wise I imagine just a low boost on the current engine :)

Iv a 4:1 gearbox to rebuild in the meanwhile & an ATB or LSD diff to save for as well.

Looking forward to wiring a MAF & Knock sensor into the ECU and a bit more mapping.

A different class in the hillclimb but more torque to play with.

So lots to keep me busy whilst trying to keep the car on the road
 
Whats going on at the mo is rear inside wheel lift is occurring and the owner rather it didn't, at the same time he wishes to have good travel to absorb bumps/dips but without the body roll.
I've spent a couple of days with Paul (@pollyp) where he was still getting inside wheel lift, but a very consistent and strong road holding capability. Every drivers different but to generalise the setup, stiffer damping rear, and higher rear tyre pressures are a good baseline
I've been doing some reading and trying to understand suspension dynamics better, in particular roll centres and how this effects balance.

Anyway the prospect of raising the roll centre to a similar height to the centre of mass thereby reducing the roll couple or the leverage around the roll centre (and therefore roll) always comes up when explaining roll centres. The reason that this wasn't done was given as this would increase 'jacking' without explaining much what jacking was or how a raised roll centre resulted in more jacking.
Usually attaching a scary picture like this (which caused me to go Argh! what the $%(! you're right I don't want that....:eek:):


Jacking was explained as due to a high roll centre not a particular suspension design or due to the positive camber in the picture (it'd be negative if the suspension was going the right way!).

I eventually (I think) got an idea what jacking was and what causes it.

In the above picture say (for arguments sake) we got the centre of mass and roll centre in exactly the same spot so the car didn't roll at all, or all cornering force was being directed sideways through the roll centre with no rotational component.
If you follow the dotted line in the above picture from the roll centre to the tyre contact patch there is a slope downwards this means there is a sideways component (the majority) and a vertical component(minor) which isn't causing the suspension to compress but weirdly to extend. :confused:

So rather than compress the suspension on the outside wheel it's extending, if the centre of mass was above the roll centre body roll would be combating/balancing this extension and we might corner flat.

Looking at say this picture (picked at random ;)):

Overall the car seems to have some roll but viewed in isolation the rear doesn't seem to have any roll (what would it look like if both wheels were on the ground?).
The wheel on the inside is either compressed or neutral, when we'd expect it to be extended, but it is connected to the outside wheel via the beam axle IF the outside wheel were being extended and twisted by jacking this force could hold the inside wheel up via the beam (think of it as a pivot around the roll centre which is approximately the beam axle centre). The rear of the car is also higher than the front, which may be because of braking dive but could also be caused by the same jacking force, lifting the rear as in the first photo above.

So this led me to wonder what you could do about it...

One thing appears to be like mentioned above we could induce more body roll to combat the jacking, but that seems to be robbing peter to pay paul.
The ideal seemed to be to try to lower the roll centre and therefore minimize the vertical component between the roll centre and the tyre contact patch(middle picture), but as this roughly (very roughly) centred around the middle of the beam without changing suspension design this seemed impossible... until I thought what determines the height of the beam? well the wheels and tyres, so what if we went for the smallest diameter wheels and tyres we could fit we could effectively lower the roll centre and probably not be breaking any racing class rules either :) OK it might look a bit different but this is a race car right? results are more important!

Anyway is there a hole in my thinking? it could be a relatively cheap experiment I'd think, but interesting to think that large rims could also be making the problem worse!:eek:

For those with wide and large rims fitted to gain a wider contact patch and more grip the front tyres are the ones likely to need this rather than the rears, keep the fronts and change the rears?
 
that pic of me on santapods site seem to be spreading around lots :p

aye my car has a relatively high cog,
soft spring rates 4/3kg f/r (too soft for this sorta thing),
dampers were at 50/100% stiff f/r,
corner balanced with 62/38% f/r weight distrib,
the hot sticky semislicks were at 2.0/2.7bar f/r,
whiteline swaybars front & rear, rear set at full hard to reduce understeer.

at that moment of the pic I was heavily trail braking with lotsa steering angle on the powerful GTIR brakes,
the semislicks sticking to the tarmac hard and induce a huge amount of weight transfer,
inner back wheel popping up from the big weight transfer rolling the chassis on soft springs and stiff rear swaybar pulling the inner wheel up to match the compressed outer wheel,
I locked the lightened rear wheels with handbrake to induce a sharp turn,
the left side had just ran over a huge dip in the road which rocked the whole car up down even more,
then click, this pic was taken.
 
that pic of me on santapods site seem to be spreading around lots
Not a criticism at all there were other photos illustrating the point I could have chosen just you'd posted this one up and your car had entered the discussion, so I thought it relevant. It seems a trait of micra when pushed hard which might suggest it happens to some extent regardless of the usual suspension settings.
 
Not a criticism at all there were other photos illustrating the point I could have chosen just you'd posted this one up and your car had entered the discussion, so I thought it relevant. It seems a trait of micra when pushed hard which might suggest it happens to some extent regardless of the usual suspension settings.
:) not a prob. I was just commenting on how popular that official pic of me was going around and explaining what was going on at that moment to create such extreme position as a contribution towards the discussion.

aye it's a pretty common thing for a short base, high COG, soft front, stiff rear, front heavy fwd car to pop it's inner back wheel up during hard trail braking in attempt to reduce understeer and ain't a bad thing, just a result of certain compromises
 
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Skinner_87

Skinner_87

Club Member
But more progress to the turbo addition.

A 2nd hand GtiR plenum will be donating it's lid, a 10mm aluminium plate can then be machined to match the Jenveys with 45mm ports and possibly trumpets (or the plate will be beveled to a bell mouth)

Looking for a company to water jet or machine the adapter plates. CAD drawings are ready to go if anyone has any recommendations

 
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Skinner_87

Skinner_87

Club Member
EOI: FOR SALE

If anyone would have an interest in buying the car drop me a PM

I'd rather not break it and sell seperate because of post but if it needs to be done that way il look into it properly.

For the full spec / any info as I say drop me a message

Cheers

Paul
 
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Skinner_87

Skinner_87

Club Member
Why? Not leaving the Micra fold are you?
Thinking it over Matt.

I quite fancy something else, maybe iv just fell out of love with it as its been apart since September & not on the road.

Its either spend a bit on it to make it competitive or sell up for something else all together. Im honestly not sure what to do .....
 
With the time and effort you've put into it do you really want to start again?

You'll only find yourself in the same situation as now just in a different car.

Ultimately it's up to you and what class you want to compete in
 
back in 2012 mine was off road for 6mths whilst forged engine was getting completely rebuilt with new oil baffle system.
when projects go stale I just focus on prepping & working towards the goal (design n build oil system, clean & analyse stuff, recap past footage), keeping ourselves busy.

look back at good times what its helped you achieve, look to the future of ambitions and judge do you like this road, where it's going to, how close the destination is, is it worth the extra time & push to make it compared to how far u progressed already, or do you go all the way back to scratch and look for a different road & destination?

when my forged engine was still burning oil badly after this last major rebuild, I was so close to quit but I've invested so much time, money, soul into her, we had good times and was looking forward to future plans (trackdays & nurburgring), she still works and fab to drive, twas just the annoying unknown of failing to fix the oil leak, if it'll last and pass MOT with this burning oil that was doubting me.

my crossroad was either give up failing & losing 4yrs or hard detailed work & many thous of £££ & start all over from scratch costing many more,
or presevere onwards on the final run, last resort being so close to finishing with nothing else to lose and seeing if it'll improve.

but with support from club and nothing to lose other than give her a final thrash on track to verify my doubts, I just stuck with it, and was eventually rewarded with a reliable engine going to many trackdays with no major issues, took me to germany and passed her MOT.
suppose its like When in doubt, Flat out :p
 
if you really fancy a change paul ? i would go for something later model, that had performance from the factory personally, a ford ST or whatever, or a classic rwd car that will hold its value if you want to sell it on
the dosh that some of you guys spend on what was essentially a mass produced town car baffles me tbh
 

SirChris

Educated Bodger
if you really fancy a change paul ? i would go for something later model, that had performance from the factory personally, a ford ST or whatever, or a classic rwd car that will hold its value if you want to sell it on
the dosh that some of you guys spend on what was essentially a mass produced town car baffles me tbh
This. Can't turn back now in my case, plus its a hobby and a challenge. Nor will I sell it tbh. I don't spend much time on it either it, I have a job and a life outside cars... Sometimes.
 

SirChris

Educated Bodger
Skinner is at that point I think, tell me if I am wrong Paul, that you want more performance and improvement on handling etc which would require significant modification/cost. Where if you bought a modern, more performance minded car, you would get it all at a fraction of the cost. It will be way better in all departments compared to a Micra and no doubt be better suited to performance increase with off the shelf parts. All providing its a popular car. And tbh would handle better and perform better at stock level, than a Micra at balls out spec.

Sent from my Nexus 6 using Tapatalk
 

SirChris

Educated Bodger
The grey Micra was expensive and similar to Paul's car at spec. This white o have now one is a unicorn. ####ing pointless and the cash spent on it was, how would say, foolish. Isnt reliable, and expensive to fix, Paul is right to question where the micras going in the future. I would seriously suggest he considers another car.

Sent from my Nexus 6 using Tapatalk
 
in my case i spent a huuuuge amount of man-hours on my micra,s (which i now regret) and even though mine were very ghetto built, a fair amount of cash i guess
 
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Skinner_87

Skinner_87

Club Member
Cheers for the advice gents, its appreciated :)

As Frank and Chris have said its at the point where unless im investing in forged parts, limited slip diff's etc im not going to be competitive.

Dave, its just that, the MSA have moved AO48r off list 1b so to stay in my current class im going to need 4 new tyres (R888 most likely) as well an a HANS device pending rule changes a believe!

Id mentioned to Chris earlier about the like of a Caterham or similar, I've been reviewing all sorts, Fabia Vrs, ST fiesta, 325 E30 maybe.

I have an entry in for the hillclimb again April 2016. Il refurb the Jenveys and get the car setup as well as I can for then with minimal expense and see where we go from there
 

SirChris

Educated Bodger
That white weapons got too much grin factor built into it surely!
I am trying to resolve countless issue with it Paul. Win one and two issues pop up else where. The Micra was never designed for this deal, and I haven't even started abusing the car yet... Worse thing is I can't drive it on the roads .. I will lose my license I swear.

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