Mk2 Coopers Mini turbo
Turbo Mini Forums

Gday turbo Mini fans

have just introduced myself in intro section. I will be building a mk2 cooper s mini turbo.
this is my first turbo build so getting my head around it to be quite honest! and i will have many questions along the way.

Here is what i am up to
- bottom end is currently getting machine work by Russel engineering (A series Specialist here in AUS) specs include:
bored 1310 with Graeme Russel dished piston to 8.5:1 CR, 1100s big journal crank cross drilled, ground and balanced, Graeme CAM haven't got full specs but he runs these on turbos will find out more. forged conrods (i had these unused for a while so am using them. modified oil gallery behind pump.
Grahame will also machine the head but awaiting the bottom end first before this happens

Bits i have so far:
MED roller drop gears 1:1
MED belt drive kit with ignition sensor and damper
KAD pinion brace
KAD oil pump
fusion fab manifold and dump pipe GT17 turbo
Minispares manifold
MED push rods
MED ATB
Side mount VW Gold intercooler
Haltech elite 1000 ecu


Ok first question relates to the gearbox. i have spoken to many people over here who are running standard helical gears some on twin cam binkys with 180 atw hp. i have contemplated the mini evolution helical set? but if the standard gears will be fine i am happy to run them. what is everyone the throught's

So far i have a remote box (about to be sent for soda blasting), new bearing (quality english/japan), new heavy duty evolution bulk rings, i have modified the box to adapt A+ layshaft an have a MED competition layshaft and an A+ laygear set. MED ATB on way but still undecided between 3.2 or 3.4 final drive. i also have pinion support from KAD in transit. If i get through to guess works ill try to get some roller output flanges and maybe a windage tray??

I will be rebuilding the gearbox myself and will get it double checked by ausmini spares just in case i stuff up. haha

So in regarding the gear box here are the questions
1: Thoughts on standard gears will like to see 130 - 150 atw,
2: Final drive ratio, i might run this on the strip (very rarely) but maybe at a classic day or something. it will be running on 10" wheels
3: Windage tray worth or not, my engine builder said not really unless you stating in high rev range for large periods of time? but it is a cheap modification.
4: i have noticed on (turbo mini sport build) the oil return line being installed into the rear of the box with an anf type fitting welded in place, is this a better option over returning back into the block mechanical fuel pump location. i have the mechanical fuel pump fitting but if it is better to plumb into the gearbox ill do this.
5: any other thoughts on the gearbox.

ill get some photos together shortly

thanks legends for any help its greatly appreciated!

Welcome to the forum, I look forward to this build with interest.

1, There are members on here that have ran similar power on standard box internals and straight cut drops without issue, but (if memory serves correct 150 HP was considered the limit) I may be wrong and other members memories may fare better than mine.
2, Final drive, this really depends on the main usage for the car and personal preference. Personally I run a 3.2 diff and until recently .958:1 drops (making the diff ratio around 307:1) with 10' rims and this was a good compromise for road track and strip.
Its worth while calculating road speed per 1000 RPM to see how your chosen tyre and Diff ratio works out for general driving scenarios/motorway cruising.
Eg;

Final Drive x Tyre rotation per mile = X
60000 / X = MPH per 1000 Rpm

so, 3.2 x 1056 (based on an A032r) = 3379.2
60000 / 3370.2 = 17.8 MPH per 1000 RPM
giving 115 MPH @ 6500 RPM

3, I would agree not essential for the power your aiming for but if it's cheap to buy...
4, As long as the oil return is above the oil level in the gearbox and free flowing (AN 10 minimum) I can't see it making a difference.
5, Again this comes to personal preference and proposed use of the car. Helical can be made to work at lower power levels if built well.
You will inevitably crave more power which will necessitate an improved spec, MED and Minispares offer some good quality entry level straight cut gear sets which can handle the power hike (again the box needs to be built well).
The alternative if you don't fancy straight cut is the Minispares helical set, there is a couple of members that I know of on here that run these with high power without reported issue.
Finally and again personally this year I've found my straight cut box not so user friendly with the onset of tinitus so when funds allow I'll be converting to the mini spares helical set.

Shane

Edited by shane on 25th Sep, 2020.

the remote box might cause you issues, the Kad support will need fettling to get it to miss the gearchange gubbins, also IIRC Pre A+ mainshafts had a thinner end where the support bearing fits on, I certanly had to a spacer to take the bearing race when I fitted one to mine. if you were to fit the minispares evo helical kit, i assume you would need to fit the A+ mainshaft, so that would avoid the issue.
one other thing the remote box is weaker due to having the 4 bolt main bearing, but I guess thats why your fitting the KAD support?

Thanks Shane an Joe

i am tending to lean towards a 3.2 diff and will be running A032r tyres so cruising rpm of 3300 at 60mph sounds more appealing.

The standard helical gears according to https://www.facebook.com/Readspeed-688922494518057/ have supported over 180hp. I have looked at the helical minispares items however they have been out of stock for a while. i might send them a message to see waiting times. i want to try to avoid a close ratio setup which a lot of the straight cuts tend to be.

Joe i have went down the remote route as A+ gearboxes over here are not that easy to find and the fact that i had a couple of pre A+ remote and rod boxes. All my pinion end have been 17mm which is what is required to fit the support brace not sure if this a UK / Aus difference.

I have purchased the brace to add support, although many guys race the remote box with no support and no cracking . not saying this doesn't happen

i quite like the feel of the remote but if i can get my hands on an A+ box ill make the switch.

any thoughts on the oil return line in to the gearbox or is back of the block ok?

cheers guys

Cool, 3.2 sounds a good choice, I run a 3.1 so basically the same.

The std oil return will be fine as long as your not using a turbo that sits lower than standard. Basically as long as you've got gravity draining it with a big enough bore it's fine.

I would go with the Minispares helical gearset, especially it's a new build. All new and good for whatever abuse you want to issue.

Lots of people on here have destroyed helical sets around the 140hp mark. I have destroyed two with just 108. 1st was a casting imperfection at the centre web, 2nd agressive shift from 2nd to 3rd at a hillclimb. For the damage they do when they let go its not worth the risk, especally given the age of most of them now.

Also make sure the helical drops are in top condition too - freshly bushed primary gear, properly shimmed idler gear

alright thanks guys looks like i have tracked down an a+ box which i can get in a couple of weeks. Now i was thinking about using the primary housing on my remote box for 1+ drops or is not worth it just change to rod eliminating the 4 bolts change and be done with it.?

I have emailed minispare re helical set as they have been unavailable for a while now.

I will be running roller MED straight cut drops. As i have worn out a couple of helical drops.

One quick question the guy selling the gearbox also has a specialised components efi throttle body for sale. it is 45mm which my engine builder says will be enough however i noticed many guys over there running 50mm ?any reason

cheers

If running straight cut drops you could just run the mini spares clubman gearset then. The Sc drops make all the racket.

Yes i am concerned about that!

Picked up an A plus gear box today so slow progress

will strip down and take some photos.

being a non mpi block i am reliant on the crank position sensor (MED damper and sensor off belt kit) I am second guessing myself here is there any need to fit a cam sensor if at all possible. All wired to haltech elite 1000

thanks Steve im watching yours closely as taking inspiration and very curious about the haltech elite as will be running that as well

that makes sense id probably go batch to start with the SC throttle body but am thinking as i am building the block up to have the option of potential sequential down the track if i want to play around.

problem is my block is not mpi or A+ i have seen somewhere a modification where the cam sensor was fitted to the distributor drive does anyone know of a retro fit / conversion?

I could be wrong with this but didn't Paul S or one of the EFI guru's have something mounted on the timing cover to pick up a point on the end of the timing gear?