Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Remap 4/4 Sigma

Thank you very much for the explanation. Can the car be ordered that way or has the axle to be modified afterwards? And how much would that cost?

Whilst I think the 4.1:1 axle mod is a very good one- for me the biggest change to the car came when I fitted the Aero Throttle Bodies.

If you add the Aero manifold, cat and exhaust the bottom end is improved ( but the Sigma is never going to have the torque of a V6/8)

The Throttle Bodies with the remap just make the sound glorious - and the top end revs intoxicating.

Not a cheap modification - but value is in the eye (ear!) of the beholder !

Yes TB's are a must and a sports exhaust , can't beat the pops and bangs on the over run !

Is there a way of telling by looking at the casing which axle ratio it is?
Nick

Yes there is an ID sticker on top of the axle tube "UK off side" But gears can be changed and stickers not!!!

A simple way is a road test. Check your gear box ratios, which will be stock unless you have a special.

With stock 3.73 diff gears:
4th gear (1:1) 60.6 mph=3000RPM

With 4.10 diff gears:
4th gear (1:1) 55.1 mph=3000RPM

Kind regards
Cain

I don't know how much it would cost to have a 3.7 diff converted to 4.11. In theory it's quite straightforward, as it should be just a question of changing the 10-tooth pinion on the input shaft for an 11-tooth : The crown wheel stays the same at 41 teeth, giving the higher ratio (41/11 = 3.73) as opposed to 41/10 = 4.1.

Having said that, if you were going to go down this route I would heartily recommend having the differential itself replaced with a Quaife torque-biasing unit, with these you get all the advantages of a limited-slip differential without any of the disadvantages of a locking arrangement. I had this done to my 4/4 and it has transformed the ability to get power down effectively.

But it's not cheap, I think I ended up paying Billy Bellinger way over GBP1000 to rebuild my rear axle. Mind you, he did a splendid job.

I don't have throttle bodies on my 1.8VVTi engine, but it does have variable cam timing and variable intake length. With the MBE ECU it gives around 165-170bhp and revs through to 7,200.

Who cares about a comparative lack of torque (150 ft-lb or so), when you can just drop it a gear listen to the engine howl past 4,000 rpm?

The Quaife torque-biasing unit, with these you get all the advantages of a limited-slip differential without any of the disadvantages of a locking arrangement.

Not true.

The Quaife does not work as a true LSD as Quaife is a torque-biasing unit. So if there is no Torque to a wheel i.e. you lift a wheel, hit water, gravel with one wheel or even grass, ice it does not Bias so is not working to keep both wheels powering forward motion.

The Quaife is very good for a flat smooth race track and does not reacquire maintenance and is not adjustable more suited to a front wheel drive car as it does not snatch.

The LSD.
Works with friction plates. with a preset ramp (springs) which can be set (changed) to suit your driving style and road, rally or race.
It still works on loose gravel, mud, ice, water and gives constant power to both wheels.
To give an extreme example, You park half on a wet verge a front wheel drops into a dip your rear wheel on the grass spins the one on the road does Fanny Addams thats an open diff or a quaife. The LSD the grass wheel does not spin as the LSD transfers power 'drive' to the tarmac wheel so both turn, and you drive off.

So as for reliability the LSD needs regular oil changes of the correct spec, Friction plates will need to be changed when worn road use about 60,000.

I would defiantly put an LSD in as well, because it will transform the driving experience and ensure more traction off the line and round corners, but I'll go for a stock BTR LSD or even better a Gripper LSD or Titan LSD.

Cain

I bow to your superior knowledge. All I can say is mine works great on loose surfaces, and we have plenty of those on the back lanes of Gloucestershire.

So long as you have some grip, the Quaife will provide drive. Where I find it especially useful is on tight uphill corners, where the open diff used to spin the inside wheel, the Quaife doesn't.

Thanks for the reply Cain. I have the mazda gearbox so I'll have to check the gbox ratios........it's a question for me as 3000 in 5th is only 70mph.....also the car oulls happily from 1500 revs so I'm wondering if the mazda box mated with the standard axle does the same as the changed axle on an older sigma.......mind you, the dealer, when we were out for a test drive, said he was thinking maybe the factory had applied a slight remap as the newer 44s seemed so lively.......?
Nick