mx5-kiwi

I have a new project in mind..

For ages I have wanted to play with reliable 250 + HP, 10" wheels and front and rear Aero and strip out weight etc. The class I race in won't allow aero etc but will in the invitation class, which is the almost anything Japanese goes class.

I figure I will build an all out race only car (unlike current car that is still road capable and legal) and have a bit of fun with the build.

Now that Trackspeed have the superlight brake package it is pulling me even closer.

So in the interest of NON turbo related issues I want to run a VVT Toyota V8 WITH the mazda 6 speed.

before you all start on the "why waste your time just go LS" bandwagon...this is why.

1. LS motors outside of the US are VERY expensive

2. LS motors outside of the US are very rare.

3. LS Motors REQUIRE a stronger Diff and Gearbox, not to mention a lot of fabrication etc associated.

4. I want to stay in the Classic Japanese class

5. Toyota VVT motor is not expensive, is not rare

6. Toyota VVT puts out a proven (with a megasquirt) OEM 300 HP and 300 ft lbs at the wheels.


further reasons are IF we can mate the motor to gearbox, the rest of the installation is easy. i.e. oem diff, retain PPF etc.

So, thoughts and comments on whether the gearbox and / or diff will hold up to the power curve of a 300 hp 300 ft lbs v8?

It will be a reasonably driven race car so it wont be abused like a drag or drift car with burnouts etc, though we do do standing starts.

18psi

iTrader: (76)

I don't have any problem with the toyota v8, and it will likely hold up at those levels (though close to the limit on a race car, but then you'll be light so it might still hold up)

but

why a v8 for only 300? surely there are smaller engines that can achieve the same reliably even in n/a trim?

psyber_0ptix

iTrader: (4)

What's wrong with the Toyota gearbox? Custom driveshaft, done.

Diff will be fine.

Savington

iTrader: (31)

I would not expect a Miata 6-speed to hold up to 300wtq for very long.

mx5-kiwi

has to be japanese for the class and available here, remember its totally different to there.

Also, heaps of info on how to fit motor to car, so should be relatively easy. Mazda v6 seems like a hassle and hard to get. Honda's are okay but I race against heaps of hondas so would prefer to not join that crowd...Also the kits are hellishly expensive once $, freight and customs etc factor in.

mx5-kiwi

hmm, this is my concern.

My hope is that it would last a season or two...then stage 2 if/when it did prove to be a problem would be to look at a toyota gearbox.

Glad to hear the diff should be okay.

custom gearbox mount, custom diff mount, chassis bracing .....toyota gearboxes here are $2,500.00, the motor is only $1,900.00 (NZ $)

mx5-kiwi

appreciate the input so far, thank you.

bbundy

300 wheel torque 4th gear in the 6 speed will not like. been there done that multiple times over and over.

mx5-kiwi

Bbundy, thank you.

As an avid reader of the gearbox thread I know this is an ongoing problem...my hope was that the torque curve of a lower power V8 being a bit more progressive than most turbo cars would / will have a positive impact on longevity.....

you dont think so?

deezums

iTrader: (3)

There was talk about lighter flywheels being harder on the gears. The smoother power delivery of a v8 should make a difference, but how much?

Could you tune in some torque management with VVT, the initial shock of all the v8 torque is probably what will break everything.

tehzack

Are W58 and R154 trans expensive/rare in NZ? Folks put those behind 1UZ motors all the time.

Edit - It appears they are. Reading comprehension fail...

Adapters can also be had to run the Nissan S13 or Z32 300zx 5spd trans for toyota v8's.

Leafy

iTrader: (1)

Wait, LS are really hard to come by in upside down land? I thought you guys had a shitload of Holdens over there packed with ls juans.

mx5-kiwi

Sadly, they are one of only 2 main brand v8 vehicles (ford Falcon the other) so the vehicles are treated like holy grails are not especially plentiful to start with, then when any do reach the wrecker or whatever, other Holden owners want them, hot rod builders want them and so on....so they start at $7-10k plus IF you can get your hands on one....and that's just a used 100km or more motor.

but, LS (GM) isn't in keeping with our classic Japanese class, build cost escalates rapidly, other drivetrain costs escalate etc...as per original post.

bbundy

I don't think the big factor is shock loading it is more fatigue loading of the teeth under load. It is time spent at full torque in a particular gear. lube choice or shock additives also have little or no impact on it. Run full throttle down a straightaway and the individual teeth are receiving ~ 5000-7000 full load cycles a second as the rpms sweep through the high torque range of the powerband. I've never had one pop upon a shift or any jerkiy type shock event such as landing off a yump or bump at full throttle its always been in a straight line pull with revs climbing through the power band on a smooth high grip straightaway.

Savington

iTrader: (31)

As a data point, I killed my 6-speed in the same way (4th gear pull through the torque peak).

patsmx5

iTrader: (16)

300tq from a V8 will be easier on the transmission than 300tq from 4 cylinder. Average torque of 300 will be the same, but the peaks will be lower from a V8 since it has more cylinders firing.

I'm running a stock 18lb flywheel on my 6 speed to keep the 4 cylinder torque peaks as dampened as I reasonably can.

mx5-kiwi

all of this wont be valid unless I can even get the 6 speed adapted.....and it seems like we are sort of covering off or rehashing the gearbox thread....

I guess that leaves me somewhat hopeful as there is some doubt how long it will last (worst case) or that it MIGHT be okay if the power delivery etc is any smoother or delivered different in any way.

At least its not a flat out, "it will blow apart in 3 laps time" ... (though it still might! )

I think at this point i'm going to hope that BBundy's and others (the few others circuit racing with 300 ft lbs or more) experience will at least give a year or so of use.....it will certainly beat bashing my head (and wallet) against a brick wall with all sorts of messed up engines in the turbo route..though wouldn't you know it we are close to getting a handle on that now...

Stay tuned... it MIGHT be interesting....

I do wonder if it does work out, whether its not a reasonably low cost, mid power option for people...I mean a 300 ft lb, 300 HP at the wheels mx5 is going to be a bloody quick little car.......which most importantly, if it can be done retaining oem gearbox, ppf and diff....WITH an OEM Motor (a relaible as all f**k toyota at that) seems pretty good to me.

How much are wrecking yard 1uz vvti motors going for in the US?

Mobius

iTrader: (2)

Can't you run a restrictor on the V8, combined with tuning, to keep the torque down to 250 or so? That should take care of your durability problem.

I see so many Utes running around down here, didn't think LS's would be so expensive. But if GM-Holden isn't selling them as a crate motor then that puts a real hurt on the supply.

DaWaN

People in the UK and Russia have mated 1UZ's to the IS200 / Altezza 6 speed box, which happens to be the same box as the Miata. I was thinking of going the same route (I own a Lexus IS200 which is terribly underpowered), but I am not sure about the gearbox. For street use I guess the box will be fine as is proved by people in the UK running IS200s/Altezzas with this combination. I would like to occasionally track the car and I do not want return home on a trailer though.
I am on the lookout for a R154 box ever since, but they are not cheap in Europe either. There are not much gearbox alternatives for the Lexus as it has quite a cramped transmission tunnel and I do not want to cut the tunnel. Alternatives are a W58 and V160 / V161, but the W58 is a bit old, weak and clunky whereas the V160 / V161 costs as much as a complete decent replacement car.

As for mating the 1UZ to the Miata box: that might be possible by swapping the front of the transmission case from an Altezza / IS200 and buying an adapter plate from one of the fabricators in the UK. Shipping to NZ might be expensive though...

tehzack

1998-2000 LEXUS GS400 SC400 LS400 4.0L ENGINE JDM 1UZFE VVTi MOTOR 1UZ | eBay

Looks to be about 1300-1500ish.