Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Morgan need to give the new Plus 4 more power

Hi Cerealsurfer,

Do you (or anyone else appreciated) know the gear and axle ratios of the current 4/4? It's the first Mog I drive who feels really correct.

I agree to all points you have made regarding the Morgan ratio issues and their attempt to compensate the given gear boxes taken from saloons and vans, resulting in a compromise.

BTW concerning your custom made gearbox/axle ratio, if you translate the data, where is the red line (or better comparable to road cars) where is the speed for each gear when running 6.500 rpm?

Not wanting to detract from the standard Duratec which I agree is a lovely tuneable engine, but the +4SS engine is quite a distant relation: a Mazda version with independently variable timing on the inlet and exhaust cams. That's why the top of the engine has the extra 'lump' in the cam cover compared to the standard Duratec.

I'm not in the UK at the moment to do the analysis, my redline is 8000rpm.

If you use the following tool (and draw on the shift points as horizontal lines - cross referencing against the power/torque curves for your engine) you'll get the answer.

http://www.gearboxman.co.uk/inforatios.html

Alternatively I can give you some more info from my race car thread.... (Just seen in preview the links only work if you click them - I'm working off iPhone and I can't get the 'copy img source url' function).

First off - you can see the shift points as slight dips in acceleration as I come off the start line - you can read across to the speeds (gps driven data).

[img]http://www.talkmorgan.com/ubbthreads.php?ubb=showpic&id=10434[/img]

Stock ZETEC E Blacktop with twin 45DCOE and high lift cam.
[img]http://www.talkmorgan.com/ubbthreads.php?ubb=showpic&id=8333[/img]

Race ZETEC E Blacktop on twin 45 DCOE
[img]http://www.talkmorgan.com/ubbthreads.php?ubb=showpic&id=8039[/img]

Weight info for both:
[img]http://www.talkmorgan.com/ubbthreads.php?ubb=showpic&id=8040[/img]

That should give you enough info to work it all out...

Thanks a lot, nice stuff for a long winter evening...

[quote=Andrew255]According to the manual the ratios for the current Plus 4 and 4/4 are:

Gear Ratios. Plus 4. 4/4
1st. 3.87. 3.136
2nd. 2.08. 1.888
3rd. 1.36. 1.330
4th. 1.00. 1.00
5th. 0.76. 0.814
Final Drive Ratio. 3.73:1. 3.73:1

Both use the Mazda MX5 gearbox... quote]

Thank you all for these datas (ratios, curves...)

Comparing to the ratios of my 2005 PLUS 4:

rear axle same ratio
The only difference is on the 1st gear 3.87 (Mazda) vs 3.61 (Ford)

Nota :To calculate the final ratio multiply the gear ratio by the rear axle ratio.

How to understand the final ratio: in the above exemple, in 5th when the motor does 2.85 rotations the rear axle/wheel does 1 rotation.

Greater is the final ratio, greater is the torque on the wheel, the force between the wheel and the road, and the acceleration.

For the final result mph/1000rpm the size of the tyre have to be taken into account. 2005 PLUS 4 : 195/60 R15.

To cerealsurfer what tyre size do you use during races?

Hi CBY, Have you ever had any difficulty passing the CT?

That means MMC uses different Mazda Gear Boxes for Plus 4 and 4/4? I´m impressed if they really consider the different engines performances.

If I understand the figures right, I´m wondering if the stronger Plus 4 got a shorter first and second gear in comparison to the 4/4?

My PLUS 4 is a second hand RHD. I bought it in UK by BerryBrook in july 2011. They changed the front lights and invert fog and reverse lights at the rear to be compliant with right driving.

At the arrival in France I have to do a CT(MOT) and it was OK. In july 2013 for the second CT no problem. They don't know well these cars and seem a little affraid and carefull.

Heinz
I am merely copying from the handbook. Whether Morgan really uses different MX5 gearboxes and ratios and how accurate the figures are who knows.

185/55/15 on the 185bhp engine
205/50/15 on the 230bhp engine

You'll probably find they give almost the same rolling circumference.