Hey guys. It's been awhile since I've had much to say in Miata-land since I sold my turbo'd Miata...which was since driven into a brick wall. :(

I now own an '04 RX-8. LOVE the car. HATE the engine. (Sorry rotory guys) I've been considering v6 options and it dawned on me, don't alot of Miata guys yern for a v6? Well...I found one with bolt-on RWD options. It's VERY similar to the KL but by golly there's a transmission that fits it.

Who's interested? Should I start a thread on it here or are there enough swap threads going?

 

There are not that many v6 miatas. Most don't beat around the bush and go straight for 8

 

Same thing goes for the RX8. They do LSx or xUZ swaps.

I'd imagine there isn't alot of v6 Miatas because there arn't alot of good v6s out there with RWD options ...until now. mwahaha

 

TurboTimmah is building a KL beast. Check out his thread

 

https://www.miataturbo.net/cars-sale...2412500-67451/

CodingParadox has a KL Miata as well, no idea if it sold or not.

 

Quad turbos? I remember his twin turbo build.

 

Engine in question... Isuzu 6VD1 (3.2) and 6VE1 (3.4). Aluminum block, DOHC, 75deg V (short height), forged rods, cast crank, open deck, and COP ignition. Built by Honda. They can be found everywhere. Troopers, Amigos, Rodeos, and Honda Passport as well as various Isuzu and Holden trucks. Good news is, there's bolt-on options to bolt a Toyota Supra (r154 ect) transmission to it. It has the GM 60-deg bolt pattern. Hello options.

Check out the 6-bolt mains and main bearing support plate with the oil rail in it. The forged rods have oil squirters also (like the SR20).

 

very interesting. cast crank kinda sucks if you wanna make a ton of torque. but it will still probably be a beast.

has anything else like this been done or will you be the 1st?

 

I'll be the first. I didn't jump in thinking "hey lets put a Isuzu truck engine in an RX-8". I did want a v6 though. I was looking for transmission options for the Toyota 1MZ-FE when I stumbled across pics of the Isuzu v6. There was a supercharger kit available for it and another company (I spoke to the builder) did over 800hp on the cast crankshaft. The widest part of the engine (valvecover to valvecover) is 24". Having spent countless hours in my Miata's engine bay, I think it'll fit. Obviously that honking intake will have to go unless stump pulling torque is what you want. It looks larger then it is for some reason. If you reference it's size off things like the cam pullys and water inlet and outlet you get a better feeling for it. Oh that's another thing, could it get any easier to plumb a radiator to it? Here's some dimensions.

 

what do you plan to control it with?
Im sure MS can do it (and many others) but won't you be completely alone in setting it up and tuning it?

 

Yes I would be. I'll use the electronics that ran that engine before. The problem I'll have is getting the RX-8s canbus cluster working. There are chip swaps available for it so it's unlikely it can be reflashed through the OBDII port. Nothing a piggyback can't solve. Depending on the year ('92-95 and '96-04) I can get cable or drive-by-wire electronics.

I really wish I had an MX-5 now. This would be a cakewalk.

Another interesting tid-bit. The image below is a production powerplant for a plane using the Isuzu v6. It's supercharged and rated at 350hp. Weight (INCLUDING the prop reduction, supercharger, and alternator) is stated at 352.74lb. The reduction itself is stated 66.14lb. That leaves 286.6lb leaf for an impressively light 350hp supercharged v6.

 

Lets put one in my Fiat if I get bored next year.

 

Hey what's up Split. How you been? Hell yeah lets do eeet! You hold the hood open and I'll kick it off the roof. Seriously though. If I get this nailed down you guys are golden for v6 swaps. The Dodge Dakota 2.5L bell housing has a GM 60 on the engine side and a Toyota on the transmission side. Here's just a few transmissions that will bolt up. Including a 6-speed from the Supra. Here's 13 transmission options for it.

Some Toyota transmission info...

R150 - A 2WD transmission found in many Toyota trucks.

Ratios:

* First Gear: 3.830:1
* Second Gear: 2.062:1
* Third Gear: 1.436:1
* Fourth Gear: 1.00:1
* Fifth Gear: 0.838:1

R150F - A 4WD transmission found in many Toyota trucks.

Ratios:

* First Gear: 3.830:1
* Second Gear: 2.062:1
* Third Gear: 1.436:1
* Fourth Gear: 1.00:1
* Fifth Gear: 0.838:1

R151F - A 4WD transmission found in many Toyota trucks.

Ratios:

* First Gear: 4.313:1
* Second Gear: 2.330:1
* Third Gear: 1.436:1
* Fourth Gear: 1.00:1
* Fifth Gear: 0.838:1

R154 - This transmission is a robust 5-speed transmission found in the 1987-1992 MKIII Supra Turbo.

Ratios:

* First Gear: 3.250:1
* Second Gear: 1.955:1
* Third Gear: 1.310:1
* Fourth Gear: 1.00:1
* Fifth Gear: 0.753:1

V160 - Toyota MKIV Supra 6-speed

1- 3.827
2- 2.360
3- 1.685
4- 1.312
5- 1.000
6- 0.793

But wait there's more!

Jeep AX15 and NV3550
Isuzu AR5 (originally bolted to the Isuzu 3.2L and 3.5L v6s)
Jeep AX5
Toyota W55, W56, W57 and W58
The W-series Toyota 5-speeds share a common face pattern on the case. Any '88-99 Jeep 2.5L bellhousing (NOT Dakota) will bolt a Toyota W series transmission to a 60 degree GM bolt pattern.

 

I'm interested to see your results. I've always wanted to do V6 but most suck or are unpractical right now (Ford's new 3.5L ecoboost engine). I looked a little bit at Isuzu engines as I think the mazda KL is very similar or something, don't quote me though. I like all the transmission options too. That's another annoying thing about the KL swap.

 

Here's some interesting figures I calculated. I'm pretty sure I didn't screw this up.

Calculated rear wheel lb-ft torque.

Gear----Isuzu v6 w/ Toyota R154 (4.10 r&p)----Stock '95 Miata (4.10 r&p)
1-------------3607---------------------------------------1505
2-------------2170---------------------------------------868
3-------------1455---------------------------------------635
4-------------1110---------------------------------------475.6
5-------------835----------------------------------------387


205/60/15. 5th gear.

Equal 65mph@2850rpm

Red is Miata, Blue is v6+R154 (4th gear is equal). It should feel very close to the stock Miata gears. Shift points are very close to the same except for that nice .753 overdrive.

 

The Isuzu v6 in question is actually a Honda engine. It was built under contract by Honda of Japan for Isuzu. I REALLY like the 75deg V. I measured 13" from the crank to the tops of the valve covers. This could help quite a bit with manifold issues. There's one fitment issue though. Check out the goofy oil filter "bracket" (or whatever it is) at the front of the engine. If it fits, great. If it doesnt fit, check out that second photo. I'm thinking banjo bolts (or ANs) might thread right in there for a remote filter. The water outlets (from the heads) also have ports in the rear. If the stock front outlets are used, this engine may run into the same issue Miatas have with the rear cylinders running hotter. I think that's only an issue with boosted Miatas.

 

V8 > V6

If you're doing a swap like that. Why not go all the way...

 

Weight. The v6 is more then 100lbs lighter then an LS1 for example. It's also more manageable. There's horsepower, then there's usable horsepower. Race you through the turns!

 

I wouldn't be mentioning weight as an advantage until you see the engine, with the necessary ancillaries on a scale.

The supercharger is another 25lbs, which would imply the engine itself is lighter then the alloy Honda 4-bangers. I dunno, but general physics tells me that 2 extra con-rods and pistons + 4 added valves + 2 extra intake and exhaust manifold runners etc do not usually add up to a nett weight saving.

 

I like the noise V6's make more. Really though it's all personal preference. Why do people use superchargers instead of turbo's?