Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Lugging the motor

In Peter Dron's excellent book on the M3W, mention is made of the massive torque spikes from this engine and how they can momentarily exert on the transmission ten to fifteen times the average not inconsiderable torque from this engine. Add to this the fact they are not evenly spaced and it can easily be imagined the major headache it gave MMC once they had made the decision to use the X-wedge.

The lugging issue comes as no surprise therefore.

ETA: your Centa drive (can't bring myself to call it a compensator) mods seem to have made major inroads into minimising this though

All good advice. If S&S says don't lug it under 2,700 then don't. It's hell on the motor and the compensator will complain. It will not be happy. Even at 3,000 when I need to pick it up quickly I will downshift. The only time I run it lower is when there is absolutely no load. Some call it coasting...

Hate it when there's somebody in front of me on a twisty road and I need to downshift every ten seconds!😡

Yes agree and equally frustrating having to use second in town, but it's such a pleasure to change gear on the other hand.

To this end would love to see the six speed version of MX5/Miata gearbox made an option. Now what would MMC charge do you think

Ouch! Those pistons get close!

Makes the reason for all that vibration pretty obvious!

Tim

Nice video, and that does definitely represent why there's a good amount of vibration considering how unbalanced things are, but that's not an x-wedge there. The x-wedge went to the different 56.25 angle from the more traditional 45, in part to avoid having to cut the skirts, like you see in the video there.

Richard, regarding the swap, if it's anything like swapping a 5 to a 6 speed in a miata, it's pretty damned easy. The bolt pattern is the same, the only thing that ended up being different was the starter. If I recall the 6 speed ended up using a more compact starter. As such there was a metal plate (shim) between the motor and the bellhousing that had to be modified if you didn't get the plate from the 6 speed transmission. That was it. Length was the same, clutch assembly was the same. Not to full hijack this thread or anything but to delve into that a bit more.

The 6 speed of course does weigh more, and has a bit more girth to it in areas. Not sure how tight the chassis fits around it if modification would be needed there. Is the added weight worth having a tighter ratio across the board? I guess that would all depend on how you drive it. (Ratios are different from US to UK 3rd gen "NC" transmission so possibly another factor to consider) I personally don't know what generation transmissions the three wheeler is using.

I think the wiring as far as reverse indicator and stuff like that are a bit different, but not sure that's even something needed for the three wheeler.

Here are some images to give you a better idea.

I saw this post early on and have been muddling how to explain lugging. Here's a go at it.

Lugging refers to placing too much load or strain on the engine.

Suppose you want to move a heavy weight up a slope. Using 10 men to move the weight would place less load or strain on each person than using 1 person to move the same weight.

Suppose you want to accelerate (which is the same as moving a heavy weight). If you use a lower gear, the engine might turn 10 times (spreading the load across multiple cylinder firings) than if you used a high gear, which might place all the strain on a single cylinder (in the same distance).

So, within reason, running a car in a lower gear places less stress on the engine because it spreads the load across more firings of the cylinders.

If you are cruising along a flat road at a steady pace, there's only a light load on the engine, so you can often use a higher gear and save petrol.

But accelerating, going up hills, etc., places a much greater load on the engine. These are the times to especially use a lower gear.

As others have noted, the S&S generally starts to object in going below 3000 rpm. But with most cars you can hear the engine start to labor if you place to great a strain on it at too low an rpm.

I agree Richard, six speeds would be great. There are times in traffic when even 1st gear isn't low enough.