Thread: MYY Gearbox?

Originally Posted by Dougal

<SNIP>
Can you imagine your wife driving and trying to gently remind her that she is in the right gear but the wrong splitter ratio?

Ah there's 99% of your problem... I don't have a wife, I still wash my parts in the dishwasher.

Originally Posted by Dougal

For my own (special) circumstances we are talking not much difference in work between fitting a 5 and 6. For others it could be a complete show-stopper.
Actually, my only decisions right now are MXA-6 speed or MYY-6. For the same work to tidy up my current adapters and convert from long-stick to short-stick position I can just as easily start again. The MYY ratios are a better fit.

Fair enough. I was just throwing in the idea that the 5 speed with splitter may even be easier to fit than the 5 speed or 6 speeds you were looking at..... and give you the result you were after. Without knowing your (special) circumstances, it hard to help.

Originally Posted by Dougal

I like to accelerate in the 1500-2500rpm band. With the 5 speed this is a stretch in some ratios. Particularly the ones which a 6sp will help.
2,500rpm in second becomes ~1300rpm in 3rd (not good, have to pull ~3000rpm in second to make 1500 in 3rd)
2,500rpm in 3rd becomes ~1550 in 4th (good)
2,500rpm in 4th becomes ~1900rpm in 5th (good).

In my circumstances I don't find my 5 speed at all inadequate in accelerating in that RPM range of 1500-2500RPM. That's why I am wondering why you do.

Originally Posted by Dougal

This 2-3 jump isn't a problem for 98% of driving, but for that last 2% it's again a PITA. That 2% is suburban where I don't want to look like the tool revving way too high or the muppet who can't drive with the rumbling vehicle.
The MSA-5P box (used to be fitted, I still have it) had a lower 3rd. So 2-3 gap was nice, but the 3-4 gap wasn't.
Those are of course when cruising. If you want to make progress then closer gear ratios would help far more. We have a power band (peak torque to peak power) of about 1200rpm. It takes more than four usable gears to stay in it.

I'm confused again, you want to drive a race car or cruise?

Originally Posted by Dougal

Did the guys on 4BTswaps get hold of you? Website was down and they couldn't find any contact details.

I don't think so.

Originally Posted by Dougal

I'm sure you've heard me doubt the turbo'd 4BD1's put out the same fuel as the factory 4BD1T's. What's your max boost and what rpm with the 650C and I'll give you some idea of what it's actually doing.

Max boost - above 15 psi... that's all my gauge goes too Obviously enough boost to burn all the fuel cleanly seeing there is no smoke.

RPM not sure, I haven't refitted my RPM gauge since I changed the bulkhead and alternator.

I'd love to know where I sit, even considered getting a dyno just for the hell of it.

Originally Posted by Dougal

I didn't ask for your opinion. I asked if anyone had seriously looked at these and if they would fit.

No you asked if anyone had seriously looked at these, not whether they would fit as well. I gave what I thought was my best answer.

I guess my answer should of simply been 'yes' and shut my trap Not much help with that though... of course anything fits with enough effort.

Originally Posted by Dougal

I don't sell conversions. I work on my own vehicles for my own satisfaction.

He he, I know that. I was having a dig

I forgot how much fun forums are!

Originally Posted by the_grubb

In my circumstances I don't find my 5 speed at all inadequate in accelerating in that RPM range of 1500-2500RPM. That's why I am wondering why you do.

I'm confused again, you want to drive a race car or cruise?[/quote]

Oh it's not in any way inadequate. But there's a gain to be had in peformance and drivability, so I'm out to get it.

Originally Posted by the_grubb

Max boost - above 15 psi... that's all my gauge goes too Obviously enough boost to burn all the fuel cleanly seeing there is no smoke.

If you've got 140cc of fuel, then to burn it all cleanly you'll need 25psi boost at 2,500rpm ramping up to 32psi at 3,200rpm.
That's why I doubt the originally non turbos are putting out 140cc/1000 shots. A single turbo at 32psi puts out a hell of a racket.

John, didn't you convert your MXA from a 4H fitment to 4B?

Do you remember the input shaft differences?

Just called some wreckers. The only MYY6's they've had through to date were AMT's. $7-10k.

Originally Posted by Dougal

Oh it's not in any way inadequate. But there's a gain to be had in peformance and drivability, so I'm out to get it.

So you do want a race car.

Originally Posted by Dougal

If you've got 140cc of fuel, then to burn it all cleanly you'll need 25psi boost at 2,500rpm ramping up to 32psi at 3,200rpm.
That's why I doubt the originally non turbos are putting out 140cc/1000 shots. A single turbo at 32psi puts out a hell of a racket.

I rarely go over 2400RPM, as the acceleration between 1500-2500 is excellent, so no need to go higher. I would safely say I easily have 25psi at 2500RPM. No requirement for me for 32psi at 3200RPM (yet).

Back to your circumstance.... peak torque (2000RPM) to peak power (3200RPM) (power band), taken from your graphs.

So we have an engine with a power band between 2000-3200, and to make use of that apparently we need more than 4 useable gears.

I am confused again. Your wishing to accelerate between 1500-2500 and so you have the little problem of having to over rev in 2nd (up to 3000RPM) to get into 3rd at 1500. However, that just means you are actually using the engines power band....

Did you want to use the engines power band or not?

I am so confused, you want to match gears to 1500-2500 or to utilize the gears for 2000-3200 where the power band is??

Tell me I am missing something... why not just drive in the range of 1500RPM up to what ever suits?

If we are utilizing from 1500 to 3200 then 4 useable gears is adequate. If you don't want to rev over 2500RPM then why keep talking about peak torque to peak power??

Originally Posted by Dougal

<SNIP>
Do you remember the input shaft differences?

What's it matter. If you want it, just do it.

Horses for courses fellas Dougal probably does a few grade changes in 10 minutes I can drop into top and not change for 10 hours so lets agree to disagree 2- 3 -4-5-6-7- or 18 what ever suits your driving situation most off the time

AM

^what he said