Gearbox upgrade - MX5 to M series engine

No idea as yet Riccy, it was just dismissed as an easily resolved issue..... and their couplings mentioned.

I went for a blast in one of their 2.5 Zetec engined cars and was so impressed that I failed to ask many pertinent questions... 0-100-0 less than 14 seconds... A lot faster than the previous fastest car I had been in, a group A Cossie... Mind at 670kg, it would be quick if it was powered by knicker elastic...

I hope to get back to them soon, I need a CAD drawing of the engine or get one CMM'd at an old clients.

sniper

sniper wrote: Busta - The motorsport engineers I've spoken to today fit the boxes in a number of different cars and according to their CAD, it can be done with just a small shifter move and a modified gearstick, as mentioned... No bubble burst... A £500 ECU won't resolve an iron blocked engine weighing nearly twice as much as an all alloy M series... Oh and apparently 6" is plenty....

sniper

Perspective. You are discussing a fairly significant level of modifications in order to achieve a small change in one of the gear ratios, and after all that you will still have an 80hp car. Yes the MX5 engine is heavier (as is the gearbox) but it also offers a very significant increase in performance for just a little more outlay than you are considering spending to "fix" the ratio of 1 gear...

I'd also be interested to hear why they suggested a viscous coupling between the gearbox and transfer case.

Lambert wrote: Any chance of pictures of your mx4by2?

As the old saying goes, a video speaks a thousand pictures.



We had 2 Jimnys going around the field at the same time and the MX5 was literally running rings around them. And it was the only one that didn't overheat!

Busta - The box will offer far more than just the resolution of the long 2nd issue, the gearing changes across the box will suit what I want and the driving experience with it, will be what I want too. I'd guess that my 1300 will be pushing 95 bhp as it stands and the gearbox modifications are just another step towards a more powerful engine. I may continue to tune the 1300 or I may move to larger displacement. Gearing is a bigger issue at the moment, resolving that will make the car much more drivable. Driving is what I do with it, not comparing numbers....

As for spend, I do things differently to most but I have a car that does what I want it to, how I want it to do it....

sniper

I've read many of your posts and I fully appreciate that you have your own ideas of what you want from a car. That said, here you are calling out for the assistance of 9 other people who also are also looking to change those very specific details.
If it helps you can put my name down for the propshaft, gearstick and gearbox mount but I have no interest in the parts required to mate it to the M series engine.

Calling for assistance... No... Asking if anybody else would be interested... Yes... Big difference...

A batch of 10 would keep the numbers to a cost/benefit ratio that some may be interested in, that's why I asked. Still feel that it is a sound proposal for me....

If you have no interest....

sniper

Just another observation. 2nd gear in the MX5 isn't really any shorter than the Jimny. 1.888 vs 1.947. That's a 3% differencee. 9.7mph rather than 10mph. 14.55mph rather than 15mph. The MX5 has a much higher 1st (14%) so the gap will be smaller form a standing start, but you'd still be looking at dropping back into 1st gear in the situations where you say 2nd drops out of the power band. And the downside of that significantly higher 1st is that if you do need to take it off-road, your crawling speed is massively higher.

Thank you for your advice..... But having driven 1600 MX with just a little more power than and a similar weight, to my car. I have no concerns.... Mazda diff ratio's are similar, the Jimny should be a similar drive, which is what I am aiming for. My last 1600 MX was a pleasure in tight low speed corners.

The taller first would be a benefit off road from my (limited) experience, anything that it won't cope with will be addressed by low range.

sniper

The gearing might be similar but there are some key differences, namely the extra low end power of the Mazda's bigger engine and the significant difference in tyre size.

I must say, the concept of a higher 1st gear being better off road is a new one to me!

Engine power will be equal to the 1.6 Mazda engine even if I stay with the 1.3. 109bhp & 100 lb.ft is not too much of a target and a 1.6 M series would yomp it, should I fit one....

There are low box gears when needed and a slightly higher crawl in first would suit a lot of the very slow driving that I do....... I have a 410 transfer and three selections of diff ratio's to play with..... and then tyre size isn't fixed either....

If the engineers can sort it, I'll be doing it.

Keith very kindly gave me a CAD drawing of the rear block, we should be able to find out if it is a goer next week.

sniper

You might manage to match the peak figures of the MX5 if you throw enough money at it but you won't match the bottom end, which is what you would require to overcome the 2nd gear issue you were to hoping the gearbox swap would fix. My old M16A Jimny took just under 12 seconds to get to 60mph. It was a good match for my girlfriends C1 but nowhere near the performance of an MX5. How you think a 1.3 with an exhaust is close I have no idea! The Jimny drivetrain losses are significant. Compared to other cars with a similar bhp/ton it will always be slower.