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MG Midget and Sprite Technical - 200 km/h: Where to start

Hi there guys

My Sprite runs 200 km/h. I won't drive that fast because everything is stock except the engine (supercharger, 5 speed Datsun, EFI).

Handling, brakes etc old stock I want to do as much DIY where possible. Any suggestions?
a.o. arnold

Tell your wife to upgrade your life insurance!

(200kph = 124mph)

Sounds like you have the makings of a great car there AO. Any photos to share?
Greybeard

What is the cars purpose, how often will it see 125 mph / kph 200

The ultimate package in my opinion

Full helmet with face shild, and a an on board helo fire suppression system would be #1

1. After market full aluminum cast wheels with race rubber. convert to 7/16 inch lug studs

2. Hard top, a sprinzel fiberglass front kit, a front spoiler and a 100 hours in a wind tunnel

3. Front Suspension... ado 3/4 inch anti roll bar, mustange 2 rack and pinion modified with bump stops 1500 competion front springs front line kit with a senondary cross bar at the FL kit hinge... barry king off set primium wishbones

4. Rear suspension... pan hard rod, coil over shocks, dayton dove style leaf springs, adjustable anti trump bars and 1st generation mazda complete rear end cut down to size... it has limited slip, disk brakes, a large speck of differant ratios and its rated to around 300 hp

6. Brakes... upgrade to a triple tandum brake masters, 4 pot calipers, ceramic pads on spit fire rotors drilled and sloted, the lines all are stainless steel bradied with AF fittings

All that and a cup of coffee and you shouldnbe good to go

Prop





Prop and the Blackhole Midget

What engine are you using ? and what is your HP?
What rear axle are you using ?
is it the datsun 60 series gearbox or the 63 or even 70 series you are using ?

ive had mine up to 150kmh and that was scarey enough on these roads !

Andy Phillips (frankenfrog)

As someone who has been close to that speed in their midget (and it's a scary place to be!!), there are two things which you have to consider... What do you need to replace when/before it breaks? and what do you want to do to keep yourself on the road??

Things which will break if you are using standard parts are, most likely your rear differntial and rear halfshafts. The halfshafts are known for snapping with normal power in a midget yet alone forced induction! EN 40 hardened steel ones are available from several suppliers Magic Midget, Frontline, Peter May, Moss etc etc... Worked for me with 166lb/ft of torque.

The diff is harder to keep going... longest ratio you can, make sure oil seals are good, breather is clear, diff oil is correct weight and topped up. Despite this expect to replace at some point if you do spirited driving, I have broken 2!

Things to keep you on the road...

Good rubber, I went up to 185/60/13 size, firstly with Toyo road tyres all round then moving onto Yokohama AO48 road legal cut slicks.

Suspension, well there are plenty of opinions and routes to go down here, I shall not list them as I am sure there is plenty to digest already in the forum. However suffice it to say do something to give you a bit more stability, at those speed the car wanders, remember there is no damping of the steering inputs in a midget and poor roads plus high speeds can cause the car to lurch around quite a bit.

Brakes... well for one or two heavy stops from a 100+ mph down, every once in a while, the original midget setup just with Brembo solid discs and Mintex 1144 pads (from Magic Midget) using AP racing 551 fluid worked fine. Unfortunately on a track day with 3 of those stops every 90 seconds, it was about 3 laps before the brake fade made the car undriveable. If this is your aim go for a big brake kit, expensive I know but worth it!! JLH motorsport do good one, moss, frontline etc also have options

Safety, up to you on this as to how much your life is worth but a bare minimum is the roll bar, personally I went with 3 point harnesses and bucket seats as well... extinguisher isn't a bad idea as it's safety for you and the £££'s you spent on your engine if you have a fuel leak under the bonnet!!


After this the world is your oyster and you wallet the only limiting factor... if this is no limit see Prop's suggestions above! ;)

HTH
Dave


D Prince

I think if I want to go that fast in a small 2 seater, I'd but a different car. Maybe an Mx5, -- as long as it wasn't rusty ;).
Lawrence Slater

Been close to that once in the frogeye on a road in France. After which the lack of aerodynamics really is a limiting factor.
Pretty standard 1330 with a bit of good breathing.(strapped main bearing)and Peter Maye fast road head, with the datsun gearbox and 3.9 dif. Frontline front suspension and standard rear quarter (but slightly with Peter Maye lowering wedges) Can't remember if I had the Yokos at that time (possibly the Avon CR somethingorothers).
Roll cage. 3 point harness. Standard Midget disks and greenstuffs.
Bill was ahead of me in his Midget and Bob T was in his Boxter.
The car felt very planted but I have no desire to go that fast in the Frog again even on a trackday.
G Lazarus

Mine doesn't seem to want to go much past 100 mph.
john payne

front end - triangulate top link and fit telescopic shocks, unless doing track work keep standard brakes.

Rear - panhard or RTL, telescopic shocks.

cut a hole in the bonnet to aid with high speed stability, really cuts down front end lift.

make sure tracking is right.

Get at least H rated tyres.

mine will do 116mph with the roof off, proably a bit more with it on. It's very stable. I've had it sideways at around 100mph and all has been fine.
Rob Armstrong

Ive gotten mine to 100 on several occasions, but it was long, wide and straight and with no traffic around...it had plenty more to go, but whats the purpose, the point has been made, its not something id do very often

Plus remember the true purpose of these cars are not speed esp in a straight line, they were meant for hair pin curve, tight turn donut spins and side ways driving basically a legalized go kart...the speed part is just an add on luxury


Prop
Prop and the Blackhole Midget

on the speedo or on a satnav Prop? :p
Rob Armstrong

When Gary Bob and I were crossing France quickly he had the satnav, I used my magic bike speedo and both were close in agreement

Unlike Gary I quite enjoyed the experience of staying happily with the Boxster

I wish I could get near that again on a track day

I feel the need

The need for tappets adjustment and aerodynamics


:)
Bill sdgpM

120 mph+ shouldn't be scary. I can't imagine it's easily achievable without a front spoiler and without one I suppose it might be scary. I also suppose without a roll bar/cage then there isn't a lot of difference once you get over 90 in the survive-ability stakes if things go badly wrong.
Daniel Stapleton

I am thinking of adding a front spoiler

If I get the car back to her earlier condition it seems worthwhile
Bill sdgpM

My MGB did 120mph when I rebuilt the engine with a few tweaks and bored it to 1980cc.
Until I ftted the ST spoiler when it got over 90mph you could turn the steering wheel from from side to side and the car kept going in a straight line. The valance lifted the front of the car up and the front wheels were only skipping along the road.......
Neckieman

Thx guys. To answer one of the questions: no I do not want to drive 200 km/h. I justed wanted to give an impression of the power I have at the moment. I will hardly run it faster then 130 km/h. Acceleration is more fun than speed in my point of view.

handling and braking are my concerns at the moment. The frontline kit?
a.o. arnold

Frontline is the generic term for an advanced racing front suspension created by one of our own here on the bbs then stolen by a company called ....frontline

So its called a frontline kit

Prop
Prop and the Blackhole Midget

JLH for brakes and alloy hubs. also brings the front out a bit as well helping with stability.

Also he does a front suspension full replacement which looks ace but is many pennies :)

FL front end seems to be the choice of many. I made my own triangulated link and so far have done about 15k on it with no lower pin wear.
Rob Armstrong

Sorry, I do not fully understand:

1. JLH for brakes and alloy hubs. also brings the front out a bit as well helping with stability.
2. Rear - panhard or RTL, telescopic shocks
3. big brake kit, expensive I know but worth it!! JLH motorsport do good one, moss, frontline etc also have options
4. roll bar,
5. 3 point harnesses and bucket seats as well...
6. extinguisher if you have a fuel leak under the bonnet!!

PS I am not intending to go very fast at all. The car is just very fast and keeps accelerating


a.o. arnold

Hey Arnold,

Mine is a 160bhp K-series powered midget what easely goes beyond 200km/h
Manely on the German autobahn on our NurnburgRing weekend.

Mine is modified by Frontline and sofar very succesfull/relaiable.
Frontsuspension + thick rollbar (great handling/steering), 10inch vented front discs+4pot callipers, polybushes allround, Barry King wishbones, 3.9 LSDdiff, finespline halfshafts, double rearbearings, 8 inch reardiscs, Brake servo, braided hoses, Ford 5speed gearbox(modified), 400lbs front springs, alloy hubs(JLH,)rear Avo's, anti trampbars, RTL, H-rated tyres, MGF seats with sidesupport and louvres in the bonnet to keep things cool and look cool. ;)

Ive visited JLH and what he created looks great and I would guess its beyond Frontline stuff as they've stopped developing new stuf for Midgets/Sprites as teyre focus is on MGB's now.

Although im not daily driving beyond 160km/h it pays to modify as they also work for the lower speeds aswell.

Next plan for me is to finaly develop my own Rolloverbar and hook up narnes belts who also help to keep us strapped in the seats.
Only been working/sketching on this project for about 6 years orso...

Best advice is to start with the frontsuspension, rollbar, frontbrakes.



Btw, being strapped in a seat by a harness in a car without a sufficient Rolloverbar is also a definitive scalping if ever the car flips over on its top...


Arie

>>Btw, being strapped in a seat by a harness in a car without a sufficient Rolloverbar is also a definitive scalping if ever the car flips over on its top...<<

Spot on, Arie - that's a good comment. But the reverse is true also.

My mates who have ridden in the Midget all hated the fixed harnesses and told me I should have conventional inertia belts. But I disagree. With the Aley bars in my car I heave the harness as tight as I can get them because if the car turns over (Providence forbid) I want to be held within the protection of the bars. So, uncomfortable and inconvenient as they are, I like my fixed harnesses.
Greybeard

Fitted a roll bar and 4 point harnesses before playing on track. They're good for road use but a massive pain for popping to the shops. I've left the inertia belts in for that.

My car is happy at 100mph plus. Certainly widening the front has made it better. So has the hole in the bonnet.

Though if you're not actually intending to zoom about at many mph then you probably won't need all the bits!

In order, if starting again on another car aimed at fast road use, I'd do the same as now, in the following order:

1) rear end telescopic shocks
2) front end reinforced top link and telescopic
3) more front track. 5 mm each side works well.
4) decent tyres (actually this should really be number 1 but I'm on my phone so struggling to renumber!). Match them to the wheel width to avoid slop.
5) shorter harder front springs
6) front anti roll bar
7) harnesses, better seats, roll bar.

Should be lovely and stable.

Rob Armstrong

With regard to aerodynamics: The Ashley Silverstone front ends look nice, are they actually aerodynamic? They look slippery, but what about lift, as Rob and Daniel alluded to? I assume that if you can get air out of the engine bay there will be enough flowing through the rad? Would some sort of air dam help?

Rob, with your increase in track have you adjusted the amount of toe-in? (I realise that widening the track will require resetting the tracking)

Where did you put a hole in the bonnet?

Mark
M Crossley

Hi Mark. I did change it, yes, but no idea what to...

I think it now has a very tiny bit of toe in, I basically messed with it until it felt 'right'

Seems to be OK so far, I've got no funny tyre wear (excepting the melting that happened on track).

The hole in the bonnet is directly above where the dashpots would be (if I had any). When it was A series a burst vacuum pipe and soggy engine mount conspired to dent the bonnet with a dashpot top - so I cut a hole in it and put a little teardrop on top. Phase 2 had the front cut off the teardrop which also helped with vapourisation issues

I (much later) then put an alloy inlet manifold on with a sensor on the front that didn't quite fit in - so moved the teardrop and made the original hole bigger with a vent in it. This is the setup that now keeps it squarely on the ground (at least, from an aerodynamic point of view!) and is currently right above the exhaust manifold. In traffic you can see heat piling out of it. In mildly damp weather driving at the right speed it dries one side of the outside of the windscreen off...





Rob Armstrong

Thanks sofar. I must say the prices of these are pretty high. What do you guys think of:

- Anti-roll bar 5/8"
- king pin overhaul
- Front coil spring - 400 lb and 7,3/4”.
- 30% uprated valves for the original Armstrong shock
- MG B frint discs?

I am not into spending 1500,- on kits etc
a.o. arnold

This thread was discussed between 29/10/2015 and 07/11/2015

MG Midget and Sprite Technical index

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