Can we talk gearboxes?

[m1tch]

Hi all,

Just researching into the project again, really getting concerned about the fact that the engine performance is there in both the 1zz and 2zz options but upgraded gearbox options don't seem to exist to fix the OEM failures which for me is starting to cause doubt on even using the MR2 as the base car.

The options see to be:

Store piles of OEM boxes in the garage and use them as expendable items
Run a C64 box with Jubu upgraded 3rd and 4th gears and swap in the stock LSD - gears cost around £700 for the 2
E153 swap from the mk2 - kit requires a fair bit of work to fit with the box being much heavier than the stock box

Currently I am thinking the options for me for a slightly higher power setup - or indeed a reliable OEM power level is to get a C64 box rebuilt with the JUBU gears as they are rated to around 300 ft/lbs.

Other option is to go for a K swap instead of a 1zz or 2zz turbo engine which I don't really want to do.

[beavisrules]

Hi all,

 but upgraded gearbox options don't seem to exist to fix the OEM failures which for me is starting to cause doubt on even using the MR2 as the base car.

 OEM failures?, never heard of this.
Assumed it was a good box overall and just doesn't need upgrades , other than maybe ratios to suit.

[Dudi]

The thing with gearboxes is unless it's your only car/daily then it's a risk that has little consequences if the gearbox does go as it's going to be confined to the gearbox only and usually just a couple of components. You just get a replacement for a couple of hundred unlike a rod going through the block on the engine.

Unless you're thinking of running major power where the standard one has no chance?

[jonty]

As per your other thread, I'd look at using a rotrex since the power is made at higher rpm and therefore you get higher peak power without the midrange torque that will kill the box. You'll be able to keep the stock box up to about 350bhp.

The other option with a turbo is to get a decent standalone ECU and limit your torque through the boost pressure target at different rpm, rather than using mechanical actuator control or cheaper management that is more crude.

[1979scotte]

Not sure the MR2 MK23 is the car for you mate.
You seem obsessed with high power figures and drag times.
Not what this car is about.
Why not a MK2 tubby? You can get loads of power out of them and there are loads of mods.

I bought MK3 with no intention to mod. She just drove so well and it felt so right.
It was only after a few months that lack of straight line performance got me down a bit.
She is so light and nimble that 230bhp makes her feel like a rocket.

Also consider a 2gr swap.
They make the fastest most reliable mk3 imho.

[m1tch]

Hmm I will have a think about the project, seems like a lightly boosted over 1zz or a 2zz swap is the limit in terms of power before needing expensive gearbox work etc. Reading up on some of the lotus threads with the standard 2zz and c64 box there are a few who have broken their gearboxes at stock power levels.

I understand that the mk3 isn't meant for drag racing as that's not the point, might look into the mk2, however those are now getting on a bit and rust will become an issue. It's more of a case of having something Japanese that is lightweight, rwd and can run a respectable 14 mile time for straight-line speed.

I guess I am just looking to see what the best power to weight ratio is, I'm not going for all out power but more about maximising the power I can get as I know I can't lighten the car too much below stock weight.

[shnazzle]

I think Civics are still the kings of the strip in this league. Maybe a different price bracket but if you're going to extensively mod anyway, a decent EP3 will tick the boxes

Mk3 is an amazing platform but to get it past 300hp reliably means lots  of cash and hard work.

Agree with Scott that 2gr is pretty much the only path. Or boosted k20, which I believe is used in that 900hp Mk3 in the States

Sent from my SM-N9005 using Tapatalk

[lamcote]

I would suggest you need to be really clear about what you want. In your main thread you seem to suggest you would be happy with no more than 250bhp/ton. You could easily achieve that with a 1zz and standard gearbox and have decent reliability, by using a nice turbo conversion. There will be several people on here with that level of power and there are no tales of gearbox problems and no need for 2zz swaps to achieve it.

I agree with you that 250bhp/ton will get you well into the 12s 1/4 mile time. That's pretty quick! Whenever I have been in a 12s 1/4 mile car, the the one thing I have never wanted is more straight line performance!

On the other hand, you do sometimes refer to wanting mega power, and that is leading you to worry about the gearbox.

If you can decide which of these you want, it will help you find the best way forward.

[m1tch]

I will have a think about exactly what I am after, the car will be a road car most of the time, will look to do a few track days and have fun on the drag strip. If it's a case that I am able to run around the 250bhp per ton figure on the stock box then perfect. I would go for a civic but I don't want a fwd car, it would get the same or more power to weight ratio but wouldn't be as rewarding.

I enjoy handling more than all out power but I enjoy the acceleration which I guess I would get from the closer ratio boxes, pointless to have a car than can do more than 120 as we don't have an autobahn here anyway and most tracks won't have long enough straights to max out.

[Mark A]

Or bite the bullet and get a Quaife sequential gearbox?

[lamcote]

If it is track days and not drag strip, then going for just(!) 250bhp/ton and then using some of the money you saved on the engine/gearbox for suspension upgrades and tyres, you should be pretty much uncatchable on a track.

[m1tch]

If it is track days and not drag strip, then going for just(!) 250bhp/ton and then using some of the money you saved on the engine/gearbox for suspension upgrades and tyres, you should be pretty much uncatchable on a track.

It won't be a 100% drag or track car but it's not going to be a daily driver either, will be looking to change suspension, wheels and tyres as those will improve cornering speed etc.

It sounds like a 1zz turbo might be a good option then go from there, just trying to nail down the right platform etc, genuinely thankful for the help I am getting from this forum.

[1979scotte]

If you want a MK2 i know one for sale with a 1mz v6 in it.
Rebuilt engine and gearbox £5.5k.
Pulls like a train.
I want it but i just bought a mk3 v6.

[Tedtiler]

I've a shed load of wrecked 6 speed c series boxes in my garage so yes they have their weak points but a rebuild using new stuff isn't serious money.
We are running a track 2zz and found a low mileage coroll a 190 box which is standing up to a lot of abuse at the minute. Keep a spare known good one ready to go in case of issues and rebuild as you need to.

[m1tch]

I've a shed load of wrecked 6 speed c series boxes in my garage so yes they have their weak points but a rebuild using new stuff isn't serious money.
We are running a track 2zz and found a low mileage coroll a 190 box which is standing up to a lot of abuse at the minute. Keep a spare known good one ready to go in case of issues and rebuild as you need to.

Thanks for the info - how much does it usually cost for a box rebuild? Did they all have the same issue? I am thinking of getting a few boxes as spare anyway and if/when I do go with a 2zz swap I would be using a C64 box but would get a LSD swapped in as per the OEM 6 speed in the MR2 - might then check to see if running the Jubu gears for 3rd and 4th are worth it or not, they are rated to around 295 ft/lbs.

[Tedtiler]

Certainly 3rd - 4th seems weak. Generally syncros cant keep up. Not sure if its the extra engine speed wearing them faster.
Specialist maybe 300 to rebuild- then new syncros etc on top of that.
I've come from mk2 mr2 racing/road cars and even the na s54 is a king compared to these c series.
If you're going for that torque you'll strip the 6 speed gears pretty quickly. Gets expensive. Even the 5 speed box is stronger and would be better on a turbo setup

[m1tch]

Certainly 3rd - 4th seems weak. Generally syncros cant keep up. Not sure if its the extra engine speed wearing them faster.
Specialist maybe 300 to rebuild- then new syncros etc on top of that.
I've come from mk2 mr2 racing/road cars and even the na s54 is a king compared to these c series.
If you're going for that torque you'll strip the 6 speed gears pretty quickly. Gets expensive. Even the 5 speed box is stronger and would be better on a turbo setup

I have heard that the 3rd and 4th gears are the ones with the issues, the Jubu gears are much chunkier vs the OEM gears, not the cheapest but might be worth it for me further down the line but as its already been mentioned the stock box can hold up ok for low 200bhp.

What sort out power and torque is your engine putting out - guessing it is also at a higher RPM as well? Also thinking that the constant shifting is also a factor, I believe the E153 box has an oil cooler whereas the C series doesn't - wonder if anyone has look into the gearbox oil temp as well to see if they run too hot and cause the oil to thin out too much causing the wear and damage?

Will see if I can find the torque ratings for the 5 and 6 speed but I have a feeling the only difference (apart from the extra gear) is the ratios rather than anything to do with internal structure, I don't know what torque figure the modded engine would make but there might be a way to run a torque limiting map on the ECU.

[1979scotte]

Stock box will hold plenty of bhp.
Stupink is running 290 on stock engine and gearbox.
Just mapped to keep torque in check. 250lb max.
I wouldnt want to push a stock engine passed 260/270 bhp for longevity.

[m1tch]

Stock box will hold plenty of bhp.
Stupink is running 290 on stock engine and gearbox.
Just mapped to keep torque in check. 250lb max.
I wouldnt want to push a stock engine passed 260/270 bhp for longevity.

Perfect. will plan to install an AEM ECU rather than a PFC as this would give me future tuning options if/when I do go 2zz, I doubt I would be running full boost all the time anyway, used to have a Apexi AVC-R boost controller that allowed me to control the boost by gear, I have a feeling ECUs have moved on since so I should be able to do that using the AEM.

Will look to maximise the power to weight by reducing the weight as much as possible so I don't need to go for a high power build - just needed to find where the limits were on stock components and upgrade paths a lighter car will handle better which is where it will be the most fun.

[Mark A]

2ZZ MR2 on eBay currently, unfinished project

[m1tch]

2ZZ MR2 on eBay currently, unfinished project

Planning to start with stock engine and stock power and learn more about the car before upping the power - need to sort suspension, brakes and other supporting mods before adding power anyway - sounds like a low boosted 1zz might do the trick anyway!