Project "Marginal gains..."
Turbo Mini Forums

Yup, it just wouldn,t be right to cut any corners at this stage of this build.

I still stand amazed at the quality of the job.

Love to see it when it is finished.

Thanks for the comments

Cheers

Found thi thread through "Build Threads"

Are you still looking for a bespoke charge air cooler and a radiator

Its my bread and butter, so would be more than happy to quote/help

Thanks for the offer, I have PM'd you

Cheers

So after the usual unhealthy amount of testing and dithering;

DSC_5382 by Aubrey Boy, on Flickr

My choice of lightweight battery which IMO can best cope with likely maximum in car charge rates and being sat outside in the overnight frost but still able to start

DSC_5385 by Aubrey Boy, on Flickr
It's not the lightest but was the best compromise whilst sticking to the self imposed rule of saving as much weight as possible but without any loss of function

I really like the terminal posts, some of the other batteries I tried felt like the terminal was going part company with the battery body before you had tightened it sufficiently.

Cheers

Edited by Aubrey_Boy on 5th Jul, 2017.

Impressive, have you tested it out?

Yes mate, the cold stuff earlier in the year and the charging / durability stuff up until now.

Sorry if ive missed it in the thread but what have you tested it on? Ive wanted a battery similar but been talked out of it by 2 friends 1 a sparky the other an engineer.. i cant remember the exact reasons.. something about how the alternator will over charge it etc but ive seen atleast 5 minis now running these now n they seam fine?

You did ask, prepare to be bored...

I tested on a few road cars, a few race cars, with a few different output alternators and 6 different batteries, 1 Wet lead acid, 1 GEL, 1 AGM, 3 LiFePO4

I data logged;

current from the alternator
current going into the battery
battery voltage
battery temp

All the sensors were permanently fitted to the car being tested

I'd data logged these from first start in the morning continuously then for say up to a 1 hour drive / commute.

Looking at voltage drop during start up alone ruled a couple of batteries out as the minimum voltage was too close to the voltage which will cause the ECU to drop out and lose crank / cam signal, this was done from say overnight cold, day time 'warm', hot etc...
Here are 2 examples of start up voltage drop and then how the battery voltage copes with various electrical loads, such as lights, heater on top of the normal ECU, fuel pump, injectors, ign coils...

Voltage_drop by Aubrey Boy, on Flickr

Voltage_drop2 by Aubrey Boy, on Flickr

I compared to known good wet lead acid, gel and AGM race batteries so I had a target levels for things like voltage drop during starting.

Having done the simple stuff it was then the two main things for me, cold starting performance (ambient around zero or less) and the maximum charge current in to the battery from the alternator in all / any conditions.

This is an example of several measurements of the current levels being put into the battery:

Charging by Aubrey Boy, on Flickr

Most of these batteries are motorcycle batteries and as such have pretty low tolerance to the charge current they will take.

In the plot above some of the batteries are from new fully charged, some are exactly how they were after a commute on the previous day and some had been deliberately drained down to a specific level. All to see the sort of current levels that they would then be subjected to. The LH axis is Current (Amps) going into the battery, you can see peaks exceeding 60 Amps, but regularly above 30 Amps. Many of these batteries are 10 - 20 Amps Max with 2 Amps as the recommended std charge, I dunno does a 60 Amp peak immediately fry a battery with a 10 - 20A max, does 60 sec at 30A kill it?

Also you can't trust your Alternator rating, the 40A alternator I used for these tests is the one shown here giving up to 60A, my 80A one was nearer 100A and another 100A only gave 80A so you really have to measure it to have any confidence in what you have.

In pretty well every instance the charge level far exceeds the manufacturers maximum level, problem is getting info on the batteries, most are just rebadged / re-packaged versions of the same battery, which you can tell from the cases and they either don't know or won't tell you anything as far the impact of over charging, some get hot, some swell, some pop, some appear OK.

As I always say, it depends on YOUR "definition of success", if your definition is buying a new fully charged LiFePO4 fit it to a car which is in a warm garage and see if it starts then everything I have tried passes this test, if it's more like "will it still work in 6 / 12 months if I just fit it and have no idea how much it's being over charged each time I use it, and I want it to start from cold if left outside" your mileage may vary.

Some might say it's only £90 and I'm willing to replace more frequently as the weight saving is big, some will say that's too much?

For me I'd say the minimum should be (I'm using an ECU)

Must always be above the minimum required voltage during a cold start up
Battery must be outside the 'cockpit' - if it does fail (Not scare mongering, just rather it was not in the same shared air volume as me )
Run the gauntlet as far as overcharging goes - it's really up to you?

I'm no battery or electrical expert, I just did some tests which I think helped me make a considered choice, experts in the field would no doubt do it differently - this is all just my opinion / measurements. You've got to make your own choice I'm not recommending them either way.

Cheers

Edited by Aubrey_Boy on 5th Jul, 2017.

Have you imported it the battery from the States then? I couldn't see a UK dealer.

It was last year when I bought it, there is / was? a UK dealer down south (I'll try and dig out the emails) and a couple of light aircraft places that can get them, but I was getting nowhere fast - depending how quickly you want / need one.

So I used up a favour and got it through a contact, it was either the US or Aus I forget but 7 - 10 days later I had it in my hands.

EDIT: Yeah I recall that the light aircraft place tended to have deliveries 3 - 4 times a year and under these circumstances the price was good, but to get it sooner you pretty well had to pay all the delivery costs from the US yourself and they would get it as a single item - so I sorted it out myself

Edited by Aubrey_Boy on 22nd Aug, 2015.

My steel boot lid is now little more than a single skin with some semblance of the inner frame and still weighs the wrong side of 3kg.

CF_single_skin by Aubrey Boy, on Flickr

Coming in at just over 900g bare gives a 2.2kg weight saving and to be fair the torsional stiffness of the two is very similar, the CF feels just as sturdy and fits and seals as well as the original.

I've decided that the bias pedal box I have may be overkill, especially the weight penalty that comes with it, so I am looking going back to a lightened version of the Mini pedal box and I have swapped to AP master cylinders with Ti pushrods;

Wilwood:

ww by Aubrey Boy, on Flickr

AP:

AP by Aubrey Boy, on Flickr

I wanted to use the AP cylinders from the beginning because I have always used them and they are second to none quality wise but at a price, it's an expensive 100g saving per cylinder but all the weight being saved at the moment seems to be at the rear of the car so I am trying to chip away at parts at the front.

All in, it's approx another 3.5 kg saved for the boot lid, pedal box and cylinders

Cheers

Edited by Aubrey_Boy on 5th Jul, 2017.

thats a big chunk of weight, well done.

Edited by robert on 18th Oct, 2017.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Cheers Robert,

But I definitely need to try and achieve a better balance as far as where the weight is saved, all the big chunks are coming from the rear at the moment making it more and more front biased

When we were discussing the factors which effect getting a coilover based rear suspension to work another significant disadvantage is the sprung to unsprung mass ratio that doing all the rear sprung mass loss causes, especially when trying to control the rear wheels over anything less than perfect surfaces. Just another thing working against you...

Yeah but you never see pics of simon lifting the front of his car! Hahaa

hmm , i suppose rear motorbike discs/calipers ,hydraulic handbrake , super light wheels ,all help?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Yeah all of the above really, anything to reduce the unsprung mass even further relative to the sprung.

As an example if we compare say a std MK1 1275 Cooper S (I tend to use this for relative weight comparisons) with an ally beam, ally trailing arms, split rims, etc... lightweight Mini we are about 13% worse off and there is little else you can do really other than try and cater for it with some inventive damping depending on what the cars used for.

rear mount radiator?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

5kg (3kg rad, 1kg fan, 1kg water) at the rear axle takes us from 13% deficit to 10% but it also adds about 5 kg of ballast (additional water and pipe work) to the overall weight. So you can see it needs to be in the order of 20kg to undo all of it...

Ironically with the LiFePO4 batteries being so lightweight the additional battery cable weight out weighs putting the battery back in the boot.

Fuel is the only thing I can realistically see in the boot (as it usually is) which has minimal piping weight (especially 8mm ally tube type) and gets more weight back there. Full of fuel (30L) in a low lying tank (gets your CofG height back) is about the same sprung / unsprung ratio as a std car which is about to run out

All silencing to be done by a single back box only, even if it needs to be bigger to get to the sound down, this helps a little putting some weight back there.

I plan to see how it is and what can be done with damping before the last resort of adding any kind of weight

With your car as a test I would add ballast as low down at the rear as you can (spare wheel well, this addresses the mass and the CofG) - if it has no positive effect - you know its coilover / spring rate / motion ratio behaviour

As with most things it's taking longer than expected, new floorpan going in:

DSC_5484ps by Aubrey Boy, on Flickr

It's pretty well all adjusted and trimmed now ready to weld in, I'd say its taken a couple of weekends for me to do just one side

DSC_5507_ps by Aubrey Boy, on Flickr

DSC_5503ps by Aubrey Boy, on Flickr

Cheers

Edited by Aubrey_Boy on 17th Oct, 2017.

excellent stuff..... oh i forgot one more unsprung weight thing , turn the shocks upside down ?

Edited by robert on 18th Oct, 2017.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Cheers Robert,

Absolutely on the 'upside down' dampers, just like on some motorbikes

My inboard front suspension layout has the coil overs 'upside down' already for this reason, it's easy not to notice because they are inboard and horizontal but it has the same benefits even though they are inboard.

I think there are some photos of my inboard suspension without the engine installed where you can see there upside down'idness.

Ironically at the rear where it will be more important to me (because of the sprung / unsprung ratio) I may not be able to do it as I am mocking up using offset damper bodies, I'm using the offset body in the opposite direction to what they were originally intended for as I want to be able to use high inset (ET35 - 40) wheels and I'm using the offset body to move the coil over away from the tyre. It all depends on what type of top mount I use ultimately.

Cheers

ah gotcha ,the offset body at the bottom making a twist on the hub pin .
congrats on your man triumphing at silverstone , bet he was tired that evening .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Yeah for once some good came of the British weather!

So it's about a month after I first started replacing the outer sill

DSC_5584ps by Aubrey Boy, on Flickr

The door step had to be replaced as well, which I took from this piece

DSC_5567ps by Aubrey Boy, on Flickr

I've still got to finish the sill to floor bit when I get better access

DSC_5587ps by Aubrey Boy, on Flickr

DSC_5585ps by Aubrey Boy, on Flickr

But I think I broke the back of it, just a shame there is the drivers side too

Edited by Aubrey_Boy on 5th Jul, 2017.