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MG Midget and Sprite Technical - 1400 K series Power Plot

Hi All

Like Roly, I was also at the MGCC midget Register Rolling Road at Aldon, and thought you lot might be interested in the result.

I drove down in the K which has recently had an Emerald ECU fitted and has had a complete engine rewire (info on and so it was a chance to get it mapped properly.

I'd been using a map that was from an 1800 (Ant's car) with the fuel scaled back.

3.5 hours in the rain got me there, then I had my go on the rollers, which was pretty scary...

Plot attached, with power & torque on arrival, plus power & torque as I left. And with a representative Elise S1 1800 engine (from Dave Andrew's site)

I'm pretty pleased with it. Especially as to improve between the two 1400 curves my master mapper (Ant) took 20% fuel OUT. That meant it used a whole 1/4 of a tank less fuel to get back (still raining!) than it did to get there! A couple of extra tweaks to even out the torque curve at around 4000 rpm, but the performance is immense...

Altogether a great day, and thanks to Dennis for organising it. If you need a check up or a tweak or anything doing then get on the next one!

Rob Armstrong

How are you getting so much more than the stock ~105 hp from a 1.4 K? Is that all purely from ECU re-map?

M Le Chevalier

differences are:
Free-er flowing exhaust with much longer secondaries, single silencer, larger dia pipe and no cat
Alloy TF manifold with 52mm throttle body, with head opened out to match manifold.
free flow filter
ECU and map - mapped for power and not for emissions.

I reckon I gained 5 or so with the de-cat and exhaust, the rest is mapping. Even the far-too-rich map felt faster than the MEMS ECU.

Rob Armstrong

Also, the drag power was around 40 bhp. Does anyone know if that sound about right?

Rob Armstrong

The improvements in torque are particularly good. For road driving that low-end grunt is just what you need. Impressive.
Nick Nakorn

just went out for a blast. ear to ear grins all round. extra torque makes it docile until you open the taps, then all hell (and sometimes the rear end) breaks loose above 4000 rpm. tee hee hee hee
Rob Armstrong

here it is on the rollers

Rob Armstrong

Hi Rob here is a plot of a race K series 1800 in a midget, we recorded 18.2 losses which gave 194 at the flywheel.


Peter Burgess Tuning

that's cool Peter :) Lots less loss on yours! did it have a straight cut box?
Rob Armstrong

Hi Rob

I am not sure how the Aldon dyno works out power losses. We use inertia testing so we accelerate the rollers with wheel power (direct top gear) which gives us the power curve, we then knock the engine into neutral at peak revs and the negative acceleration curve is logged, this gives us a flywheel power. Some folk poohpooh this method but the stuff that has been engine dynoed then tested on our rollers gives close numbers. At the end of the day we try and get the best from an engine and transmission system, we can compare losses from same make cars to see if there is a problem.
I dont really like shoot out days as I like to tune cars when they are in.

Peter Burgess Tuning

I wish people wouldn't keep posting stuff about K engined Spridgets. You know it only creates desire where none exists.

Every single time one of these posts comes up, I do my utmost to ignore it, but can't.

I'm tempted.

1). DIY mine, or buy install from specialist?
2). DIY mine, or buy a completed K Midget?
Lawrence Slater

Lawrence, join us at the Dark side, I sence the Force is strong in you! :)

Couple weekends ago ive been to the NurnburgRing with mates in all kind of cars.
The blast towards it over the Autobahn was just as good as the track it self.
Driving 210Km/h(GPS tracked) in a midget flashing to cars infront of you to make way!!!!

Childish? probably, but soooo much fun!
Like doing the Olson twinsisters. (I think) ;)
A de Best

LOL Arie. May the force be with you too mate :).

As for that speed, I think I'd probably be happy with a 1.4. I'm not sure I could handle 130mph in my sprite. A ton's enough. But I do fancy all the other attributes of a modern engine.

To some degree it's the economy appeal, but mostly it's the acceleration I fancy. I'm getting bored now, with moderns keep getting up my ar*e thinking I can't go any faster. It's as if these bloody drivers think I have no right to be in the outside lane at all, even when I'm doing 80mph. It would be nice to leave them struggling to catch up, even if they still had a greater top end speed. At least I'd make them have to put their foot down properly to pass me.

What I need to do is to see one up close and personal. I just had a quick scan on the web, but can't see any for sale, let alone any close enough for me to go a look at. I'll keep looking, but I guess the spring is the time they come out.

Meanwhile. Do I K the Midget instead of selling it, and keep the Sprite pure?

Is it cheaper to convert, or to buy a ready made?

Lawrence Slater

Buy ready is always cheaper but you don't need a K to get 100mph+ performance.

The good old A in mine has no problem propelling my midget to speeds over 170kph.
The biggest problem is the nose lifts a bit above 160Kph.
Without a front spoiler I won't take it over 175kph.
Onno K

As I said Onno. I'm not so interested in top speed. I can do a ton(mph) already, but I can't accelerate like a K can. Can your A?
Lawrence Slater

"Without a front spoiler I won't take it over 175kph."
Our K did 199.7 over a flying 1/4 mile sprint. That was the average, and the speedo read 10mph faster at the finish that the beginning. It didn't feel excessively light. The really scary thing was the course: closed public road through former swap land, bumpy with a big ditch on one side and power poles on the other ...

But as Lawrence notes, acceleration is used more often, and we have bruised the egos of a few Evo's :-)

Paul Walbran

'It's as if these bloody drivers think I have no right to be in the outside lane at all, even when I'm doing 80mph'

Pious mode on// You haven't Lawrence. Not if the nearside lane's empty. //Pious mode off.

Steve Clark

I reject your piosity, and raise you with indignation. :)

Ignoring the fact that the legal limit is 70mph in the UK, am I not allowed in the outside lane, to overtake cars in the middle lane, at 80mph then?

Should I only be 'allowed' to do that at 90, 100, 110mph?

Or would you have me immediately move over to let the ar*ehole through? I don't take kindly to being tailgated at any speed, let alone at motorway speeds. Hence I'd like more punch to leave them behind.

But even though I can't out accelerate them, a flash of brake lights seems to make them retreat for a while; at least until I'm done overtaking, and then move back into the middle or inside lane. On quiet country roads when I get someone up my ar*e, I often slow right down to a crawl. That really gets up peoples noses, and after a mile of that they usually get the message and drop back. But again, if I'm in a hurry, and can't waste time, it would be so much nicer to bruise their ego, as Paul puts it, with a stuinning burst of surprising acceleration.

Of course, with my advancing age, and the ever increasing instances of road rage these days, it often pays to just move over.

Lawrence Slater

If you can make things, it's cheaper to make than buy. Mine was on the road for 800 quid. 4 years down the line it's crept up to just over 2k, but a lot of that is extra that wasn't technically needed...

Not sure what the numbers are on acceleration, but it's pretty quick. I don't get overtaken much, and never on A roads. sometimes get tailgated on the motorway, but either simply moving out of the way or dropping a gear or two and giving it beans sorts it out.
Rob Armstrong

If I could do it for 800 quid, I guess it would be a no brainer.

I looked at Anthony Cutler's acceleration figures on the k register website.

A standard 1.4k in a Spridget does 0-60 mph 6.8 seconds.

Standard 1275 Midget 0-60 mph 13 seconds.
1275S Mini 0-60 mph: 11.20 seconds.

Even though I'm not a boy racer, (anymore) I wouldn't mind a bit of that; esp as(if) it remains economical in terms of fuel used.

Lawrence Slater

Best figures are the 40 to 70 times - they are most use on the road. Mine does around 50 mpg...
Rob Armstrong

I choose for a supercharger on a 1293 with EFI and intercooler. Don't dare topspeed, must be around 200km/h. It just doesnt stop accelerating with only a little with of boost (0,3-0,5 bar)

When cruising on the highway at 120 km/h it uses about 1 liter every 13 kilometer. When driving on other roads about 1:8

I can understand to K-engine advantages, but the fun of DIY and doing something unique motivated me

I hardly have modern cars behind me... if so I do as Rob.... :-)

a.o. arnold

ps wheel spin on dry roads whernever I accelerate :-)
a.o. arnold

a.o. How much did it cost to supercharge and how long did it take to do it?
Lawrence Slater

While on the subject of superchargers, there are plenty from BMW Mini's and Mercedes Compressor on eBay. Anyone done this yet, or contemplated?

Rob (dreaming again)
Rob aka MG Moneypit


From the Moss US website ref the 1275 Supercharger System:

The new Sprite/Midget supercharger system uses the same Eaton positive displacement roots-type supercharger found on contemporary OE applications such as Mercedes Benz.....

A link to fitting instructions:

Surely there are books with this in..........

Doug Plumb

I looked into the bmw blowers before I did my engine rebuild, ...its interesting, but you better know what your doing, and be prepared to deal with alot of heat issues

Its seems so you need a very fresh almost stock engine ... if its worn, you will find the weak spots fast and expensively

The other thing id really look into are gapless piston rings, even double gapless

Trevor jessie here on this bbs from time to time has done the bmw blower set up from scratch on a 1275 he had laying around for his bugeye...and that thing has some power and really moves along

But I think the 2 biggest things you will need are wing vents that truely work and a cometic head gaskets as I recall MOSS blew a lot of head gaskets during there R&D for 1275 blower mod.

Iirc... I.want to say an aluminum head did much better for a blower then the standard cast iron...but there lies a whole host of more issues that would be worth dropping a dime to peter burguss about.

Lawerance... thank god, you came to your scence...yes do the K, and avoid the electric motor idea ~


Prop and the Blackhole Midget

What about a super charged K series.... 1.8 liter

Now that could be fun

Prop and the Blackhole Midget

Well ask a dumb question and get a smart answer....haha

Apperantly supercharging K series engine is fairly common the super charger of choice is a rotex C-30, to me it looks more like a turbo... the pricing isnt to bad aboout 2000 to 3000 depending on how envolved the kit

Prop and the Blackhole Midget

Never measured 0-60 but never lost a stoplight sprint from anything slow.
Never had any problem overtaking do have some "trouble" with wheelspin in the wet ;)

But yes the K is cheaper.
If I had an extra midget I might try it though it is becoming a rather ancient engine.
The new 1Liter ford Ecoboost looks like a real winner.
Over 100BHP and over 60mpg sounds interesting.

Or a bike engine.....
BMW has a nice small 6cylinder with torque (1650cc) that should fit well
Onno K

lol Prop. That's more than my conversion cost in total, including all the extras!

Paul's supercharged a K series. I thought about supercharging the A series before I went K - I even bought a supercharger (Eaton M45) - but couldn't make it work for the same price. It was a close run thing though, something about a supercharger that's just ace. I bet they're great fun to drive.

I've got a V8 in the other car, that'll be a happy receptacle for forced induction...
Rob Armstrong

"What about a super charged K series.... 1.8 liter Now that could be fun"
That's what we have Prop, and yes it definitely is :-)

Rob, if you still have that blower we have patterns for how to fit it ....
Paul Walbran


That was part of my distraction... I had no idea how to hang that beast off the side the engine without at least 5 rills.of duck.tape,and the blower is alot heavier then it looks... so I pushed it along to a dear friend that need something special

But after reading today... I like that rotex C 30 super charger, it looks much more universal

Paul... I cant even imagine, haha, it must be like a rocket

The dream engine I like is the ford crosworth 1600... thats just looks like a screaming little engine, but gez are they expensive

Prop and the Blackhole Midget


My 1600 showed 34.8 losses at Aldon 2 years ago (101 at wheels)
peter, they do just as you describe

On my plot there is a rotating vehicle mass of 60kg
Dan Cusworth

Aldon are running down against the pau which is different from inertia roll down I think. When I used to play on John Nobles sun eddy brake years ago on overun it gave a -ve number which seemed near enough to compare transmissions. It goes to show you cannot go from one dyno to another and expect similar trends. Mind you we have had stuff on three different Dynocoms and wheel and transmission losses were same within a gnat's b on them all. Doesnt mean they are right, just close for system performance.

Peter Burgess Tuning

Think mine ran down while pushing the engine round rather than in neutral. Got very big tyres and wheels on, rotating mass is 80kg on mine. Good job I'm lighter than Dan. LOL.
Rob Armstrong

Hey Onno. There's a 123bhp version too. But they don't reckon it for fuel economy.
Lawrence Slater

still they say it gets 30+mpg driven like a loony in a heavier car than a midget.
So those figures must have room for improvement.
Add to that a free flowing exhaust and intake (a midget does not need to be a quiet as a Fiesta)and some gains must be manageable.

Onno K

How much to get hold of one of those engines? And would it fit?
Lawrence Slater

Paul Walbran - I'd be interested in the patterns as I have an Eaton M45 blower for the 1.8 K Series. I have all the ducting etc. but it was for a transverse installation so half of it is useless.
Nick P

gah! it's one of the only things I've ever sold...

Rob Armstrong

Just goes to show Rob, horde everything ...
All you need is a bigger house
Paul Walbran

Nick - what's your email address?
Paul Walbran

Paul - it's nick AT parrmail dot co dot uk


Nick P

Arise from the Archives you thread! I went again. 124bhp this time. Ha! even more!
Rob Armstrong

I smell the witches brew for making a century posting

Congrats rob

1 Paper

Well done Rob.

Of course a smaller driver would give it a better power to weight, I happen to be a lot smaller than you. :)
Nigel Atkins

;P I'm smaller than I was. Combined weight loss and small power increase has led to an 8bhp per ton increase.
Rob Armstrong

" ;P I'm smaller than I was. "

Thas typical for newly weds because of their nightly activities: makes you burn loads of calories. ;)
A de Best

This thread was discussed between 11/11/2014 and 30/10/2017

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