LocostUSA.com

I found this forum looking for some ideas and thought I'd sign up to mention a build I'm doing.

I have an RX-8 with a bad engine and searched high and low for a v6 swap options. The other forum is burning me at the cross for this but I picked the Isuzu v6 for my swap.

I'd recommend the multiport-injected (not GDI) 3.2L or 3.5L from '98 and up Trooper, Rodeo, Amigo, Axiom, Vehicross, and Honda Passport. It's not the cheapest thing in the junkyard (about $1500 on average) but it has quite a bit going for it as far as drivetrain options and general "connectability" (oil/water/wiring). The block has Isuzu's own and also the GM 60 bolt pattern on it. The Isuzu bellhousing has a R154/etc bolt pattern. Trans options are ENDLESS including 6-spd manuals. I'm using the 5spd Solstice on mine. The Isuzu 4-cyl flywheel also bolts to the v6, is significantly lighter, and uses a push type clutch and fits a 9-7/8"(?) disk. GM has a few that fit that size with splines for any input shaft you choose. There are many CPU options as well and it's a fairly simple electrical system.

Now before you shrug off this engine...

They use it in a production model of the Spitfire aircraft. It's 230-240hp depending on the year. The stock pistons are good to 450hp, stock rods to 650hp, stock crank to 750hp. Highest record is 1680hp on the block. Pistons and crank are cast. Rods are forged with oil sprayers. Solid bucket cam followers, 6 bolt mains (think LSx), THICK block webbing, semi-closed deck, gerotor oil pump with easy filter/cooler retrofit, and large head ports with a combustion chamber design that's very resistant to detonation.

This is my thread with lots of engine info and pics. http://www.rx8club.com/frankenstein-rx- ... ad-241226/

Interesting information on the engine & it's adaptability, thanks for posting. Any good data on the weight that engine? That description definitely does sound like the engine has potential.

_________________
.. in the world

Thanks for the info, Kicker. Ever since my wife and I rented an Isuzu Rodeo while on vacation in New England, I've been intrigued by that little engine. Always thought that it would make a great power plant for some sports car.

_________________
Mike - Read my story at http://twinlakesseven.blogspot.com/

Hey Kicker-
Put some BowTie stickers on the 'Suzu, tell everybody it's a Chebby V6... The GM faithful will all love ya...

_________________
JD, father of Quinn, Son of a... Build Log
Quinn the Slotus:Ford 302 Powered, Mallock-Inspired, Tube Frame, Hillclimb Special
"Gonzo and friends: Last night must have been quite a night. Camelot moments, mechanical marvels, Rustoleum launches, flying squirrels, fru-fru tea cuppers, V8 envy, Ensure catch cans -- and it wasn't even a full moon." -- SeattleTom

I'm rebuilding one now so I'll get some accurate numbers for you.

Supermarine says the complete engine dry is 163KG (359.35lb) and is 260hp. The supercharged one is 320hp.

http://www.supermarineaircraft.com/Marc ... Engine.htm

It's a peppy engine. Isuzus aren't exactly light either. The engine was built by Honda of Japan for Isuzu. It looks A LOT like the NSX engine. Both of the images below are the NSX. Note the oil feed atop the main bearings. Isuzu did the same. It'd be really easy to dry-sump this engine.

[img]C32B%20http://www.todaracingusa.com/images/gt-large2.jpg[/img]

Wow, some of those guys are pretty dense. A powerband that doesn't kick in until 5000 isn't much good for a DD on the street, but they seem to have the rotary sitting high up on a pedestal.

_________________
Ford 5.0 into an M3
mikaelvroom.com | @MikaelVroom

I don't let those guys get to me. It's almost entertaining sometimes. I've owned a few RX7s and drove this RX8 2500mi before I yanked the rotory. It's a fun engine to drive. I'll give it that. It just revs and revs but it's only 158ft of torque. It makes pretty good use of what it has it but it doesn't have the torque to kick the rear end out without dropping the clutch at 6k.

'99 Rodeo: (the engine I'm using)
205hp @ 5,400 rpm
214 ft-lbs @ 3000 rpm (200ft-lb starting at 1800rpm)

It's nothing to write home about out of the box but the throttle body and exhaust are VERY restrictive. The outlet of the exhaust manifold is smaller then the exhaust port. TB and header gets you ~20% more power according to the Aussi tuners. Supermarine gets 260hp from them NA. I'll be using twin T25 Garrets @ 15psi on this build. I'm hoping to hit 400~450hp.

That reminds me about the weight. The above weight (per Supermarine's specs) included a 30kg (66lb) prop drive reduction unit. In which case the dressed engine is 133kg (293lb). I would think the weight measurement to be fairly accurate considering it's for an aircraft. I'm going to measure my parts separately and get you guys block, head, and rotating (crank/rods/pistons/flywheel/clutch) measurements. I'd like to know for myself. I can tell you that the Isuzu engine set into the RX8 engine bay with the trans attached made my front end sit 1" higher.

I would buy a built engine from Petit, they are about $5K and make 220WHP which is about 40 more than the stock Renesis. I take it you are outside of the 8 year 100,000 mile warranty Mazda provides for the engine.
If you take the engine out of the Rx8 you lose what it is is all about, have you checked for and engine out of a crashed Rx8 with low miles. I would think one can be sourced locally for about $2K.
The other option would be to rebuild the engine yourself, it would cost about $500 for the gaskets and seals. This is the route I am going to take if I can not get a reman from Mazda.

If not though good luck, remember the most important thing is the gear stick location which will determine your engine location. Make sure the gear stick it is going to fit in its correct location before before you buy an engine.

_________________
2015 & 2016 EMod Florida State Autocross Champion
2013 & 2014 DSP Florida State Autocross Champion

Scrap Metal Build Log viewtopic.php?f=35&t=14558

I don't know how different the RX8 engine is. I rebuilt my RX7 engine. If you have ever done any engine rebuild before, the rotary is not more difficult. Just different! The difficult part is determining if the housings and irons are still within acceptable wear limits. Mazda publishes those limits.

Maybe not, but in a 1400# car it is certainly more than enough. And don't forget, when the rotary engine wakes up at 5K, there is no other feeling like it. IMHO. But I would imagine that in the full weight of an RX-8, there must be better options.

This thread is about an engine swap. So changing over to a V6 in the RX8 is certainly a good option. Don't let the other forum cloud your vision. It is your car. Do it your way.

_________________
Chuck.

“Any suspension will work if you don’t let it.” - Colin Chapman

Visit my ongoing MGB Rustoration log: over HERE

Or my Wankel powered Locost log : over HERE

And don't forget my Cushman Truckster resto Locostusa.com/forums/viewtopic.php?f=36&t=17766

I shopped around. The Solstice trans has a bracket for the shifter which makes it easy to adjust position (see attached). Turns out it was a bulls-eye for shifter location. Solstice guys run v8s in front of it without any issues. Strong trans.



I've never noticed anything happen at 5000rpm in any of my rotory cars I've owned. It's not like a newer 2-stroke dirt bike power band where the torque suddenly doubles. It's like an old 2 stroke dirt bike from the 60s when it's pretty much suck from idle to WOT. (see attached)

I decided against rebuilding the rotory. Bad investment. For under $5k I'll have a 450hp twin turbo v6 in it.

As for the car. It handles good and I think the interior is pretty comfortably. It's a bit heavy though and the torque of a v6 is better suited for it imo.

You'd do well on the RX-8 forums. All of them also missed the part where his project could easily cost under $2000 total and he'll have more power, better reliability, and better gas mileage than if he stayed with a rotary.



You have the patience of a saint. There are just pages and pages of someone joining the thread, not reading your responses to the first 20 people that brought up their (weak) points, and forcing you to reiterate everything.

My current 3000lb car has 146 lb-ft of torque, my last 3000lb car had 220. I totally understand your motivations for this project. I think you even outright said it at one point - you just want to be able to put your foot down and catch that gap in traffic without having to drop down two gears to get into the powerband. They act as if revving to 9000 is an advantage in and of itself - like you said, there's about 4000-5000 rpm worth of usable powerband on both engines, but the V6 gives it to you instantly.

_________________
Ford 5.0 into an M3
mikaelvroom.com | @MikaelVroom

Your missing my point and not sure why you feel the need to treat me like an idiot

The beauty of the Rx8 is not its power buts its handling. My Rx8's raw time (Dirty) was the 5th fastest at the Florida State Championships on a stock motor. By putting in a V6 I feel there are more cons then Pro's on the handling side of life but then I am an Autocrosser where the primary concern is handling.

@kickerfox I wish you all the look in this process and look forward to seeing how you achieve the engine swap. The Renesis motor is certainly lacking torque and to make it go fast you really need to make the engine scream. I thought about adding power to my car (Turbo) but instead started to build my Locost with an F22C1, S2000 power plant.

_________________
2015 & 2016 EMod Florida State Autocross Champion
2013 & 2014 DSP Florida State Autocross Champion

Scrap Metal Build Log viewtopic.php?f=35&t=14558

That was one of the engines I considered. I also like the Nissan SR20DE/DET and love the Mazda BP but I've done too many i4 builds. I decided on a v6 just to be different and I think it's a good match for the car. It's shorter then an i4 and ~80% of the engine still sits behind the front axle and fairly low in the engine bay.

Here's what the Isuzu v6 sounds like. https://www.youtube.com/watch?v=WDfazp0u4CA

Here's how it sits in the RX8 engine bay. That last pic is the Isuzu rod/piston next to a bent Miata 1.8L rod (programing error in the EMS for my 2-step). Note the size of the first ring land. If those Miata rods can handle 75hp each then maybe the meatier Isuzu rod can do it too. 75*6=450hp ...but we'll see.

And you're missing my point. Nothing you said hasn't already been hashed out 20 times in the thread on the RX-8 boards. Everyone thinks that they have this killer unique insight and instead of looking over what's been said already, they feel the need to jump in and correct this poor lost soul when he's already considered your viewpoint and has a completely reasonable rationale for making the choices that he has so far.

_________________
Ford 5.0 into an M3
mikaelvroom.com | @MikaelVroom