Advice for Turbo Build Spec please
Turbo Mini Forums

So after finishing my R1 fwd track day mini last year I am now moving onto restoring my other mk3 mini. The build brief is to have a fast, comfortable, quiet(ish) daily driver that can cruise happily at motorway speeds that is capable of getting me to the N`Ring and back.

I am new to the turbo mini world so I have been researching and reading as much as I can on the forum for the last few weeks. I would really appreciate your advice on the below engine spec as to whether it will be suitable for a reliable 125-150bhp.

My start point is a complete, standard early 1275 metro turbo lump & the mini will be rolling on 10"s.

Engine;

- Capacity: 1293cc
- CR: 8.8:1/8.5:1 (ideal compression?)
- Boost: 12/15psi
- Turbo head - Valves: In 35.6mm, Exh. 30mm, bronze valve guides
- Chambers: 25/28cc
- Pistons: Omega Cast +20thou 10cc dish
- Rods Standard
- Crank, early turbo version
- Duplex timing chain kit
- Camshaft: Mg Metro
- Front Mounted Intercooler
- `Nic` Plenum
- GT1752 Saab turbo
- Fusion Fabs downpipe/manifold for GT1752 (so no bulkhead cutting)
- Standard turbo clutch, organic friction plate
- Aldon Elec Dizzy

`Box;

- Standard Metro Turbo Box
- 2.7 or 2.9cwp
- Standard drop gears
- Quaife LSD

1976 Mini 1000 FWD R1 - 13.2@104
1975 Mini 850
INSTAGRAM @duds100
youtube.com/miniduds

Looks very well spec'd to me.

Although I'd be tempted to fit a beefier clutch. Either the 20% Minispares one or an RTS.

I would also use mapped ignition rather than a dizzy.

Edited by theoneeyedlizard on 18th Sep, 2015.

In the 13's at last!.. Just

As above if you can go for a 20% or RTS clutch along with megajolt.

I would also think about a straight cut gearbox too.

Yup SC box would be a good shout, helical drops should manage though.

If something is worth doing, it's worth doing half of.

Wouldn't worry about the crank so much as there's little evidence of them actually being tougher unless you've already got one

I'd get the standard one tuftrided if you want more longevity between regrinds
Also cross drilled for better oil delivery
Dry deck for improved cooling

Basically check out turbo-mini.com it's all there😄👍🏻

Thanks for the replies chaps. I have no experience of megajolt but know DTA fairly well so I may bring that into the budget as I suppose knock control is a nice cushion to have over a dizzy.

Do you think I will be okay running a helical gearset with that kind of power? Would you suggest I just go for a set of drops on their own maybe? I wanted to keep it quiet in the cabin ideally, hence my relicuctance to fit anything straight-cut.

Uprated clutch is definately on the list now & possibly some working of the crank too.

1976 Mini 1000 FWD R1 - 13.2@104
1975 Mini 850
INSTAGRAM @duds100
youtube.com/miniduds

Sc box and helical drops is the best compromise as it goes quiet in top when it drives straight down the main shaft.

If something is worth doing, it's worth doing half of.

We ran helical box with s/c drops in the metro van with about 150bhp. The bearings suffered, looked like we we're on borrowed time when it came apart.

Thanks that's great info. So straight cut gears in the box to take some load off the bearings & as you say the helical SC drops will keep it quiet on the motorway.

Only issue I for see now is if I run a SC/CR gearset on a 2.7/2.9 CWP will my first gear not be too long?

Maybe I should go full helical and keep the boost capped at 10psi to save the box. Decisions, decisions... !

Edited by duds100 on 20th Sep, 2015.

1976 Mini 1000 FWD R1 - 13.2@104
1975 Mini 850
INSTAGRAM @duds100
youtube.com/miniduds

From personal experience, and reflecting other comments, i'd go for sc gearkit, particulary with the potential power you'll be able to push out on that spec

I Ran SC CR gears with a 3.1 diff and extra sound deadening (5-10 KG) in the cabin. The car was great once moving and cruised quietly on the motorway and otherwise pretty quiet (with the windows up) BUT because of the taller 1st gear, driving at stop start and slow speed was tedious.

I'll be running helicals with the turbo engine so for the short term I'll aim for 120bhp max then later on I'll aim to run 120 in the first 3 gears and switch to 150+ in 4th. I'm not entirely sure how, but I'd rather figure it out than have to use close ratios.

Regarding the clutch; You may be pushing the limit of a 20% uprated clutch. IMO an RTS would be a good idea.

Edited by PhilR on 20th Sep, 2015.

ill put my two cents in the hat

2.95 and the close ratio clubman set as the others say stop start or hill starts can be kinder shitty if your not use to it
im on the clutch till moveing at 12-15 kph altho with some better tuning i may get more low end pull from my engine and get off the clutch earlier a bigger engine should be less fuss to get going
but once you get over that hump man it was awesome shifting up and down the gears as its it easy to keep it in the torque band where it pulls like a train
also fun to take off from the lights all casual then roll it on up to 75kph grab second up to 110kph

As said once you get it moving with a sccr set should pull like a train through the gears. Sccr set is perfect for an fi engine once you get it going

I've got at 3.2 on 10's and don't find it an issue getting off the line.

If something is worth doing, it's worth doing half of.

Ok so I am going to back off the spec a little to assist gearbox reliability and mean not having to go SC.

New plan is to open the head up to achieve 9.0-1 compression & run 9/10psi on a standard bottom end.

This means I can run the standard helical box & drops, fit the 2.7cwp with possibly just a 4-pin now, and run around 120bhp.

Do you think the 20% uprated clutch will be up to this? It is roughly 20/25% more power than standard so I would hope so. Only question remains now is whether it is still worth me going onto mappable ignition still - probably is for peace of mind.

2.7 on 10s gives me a cruising rpm of 3400rpm @70mph and 123mph @6000rpm for the Ring which I think it should just pull with 120bhp.

1976 Mini 1000 FWD R1 - 13.2@104
1975 Mini 850
INSTAGRAM @duds100
youtube.com/miniduds

Go for mapped ignition regardless of specification! Makes a much nicer drive.

120bhp or so, a careful build and mechanical sympathy should serve you quite reliably. The 20% upgrade clutch should easily hold this. I've seen people putting 120bhp/120ft-lb through standard turbo clutches.

If something is worth doing, it's worth doing half of.

Thanks John. Hopefully the combination of a GT1752 & mappable ignition should give me a nice torque curve with some decent low end shove to pull the 2.7CWP.

Any idea what SU needle would be a good start point for the revised spec?

1976 Mini 1000 FWD R1 - 13.2@104
1975 Mini 850
INSTAGRAM @duds100
youtube.com/miniduds

Start with the BDD and work from there.

If something is worth doing, it's worth doing half of.

Great, thanks.

1976 Mini 1000 FWD R1 - 13.2@104
1975 Mini 850
INSTAGRAM @duds100
youtube.com/miniduds