RX-Hate: A Cummins Diesel-Powered Mazda RX-8
A Victim of Circumstance

Despite the name, this wasn’t an RX-8 built to incite keyboard warriors around the world, although it inevitably will.

When Comhghan Locke looked into the empty RX-8 engine bay before him, his Cummins diesel-powered Land Rover just happened to be sat beside, its bonnet open. The Land Rover had served him well for several years, and in that moment it seemed like the most obvious thing in the world to do.

His friends that were present, didn’t agree. They told him that it wouldn’t work, but this only spurred Comhghan to prove them wrong.

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“Why did I do it? It was just a victim of circumstance,” he told me over Messenger after the Juicebox BBQ. RX-8s, without engines, are pretty easy to come across in Ireland, and across most of the world to be honest. What’s not easy to find here, is a Cummins 6BT turbo-diesel engine.

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In fact, Comhghan had to buy a complete DAF 45 to acquire the 5.9-litre inline-six and related componentry. Over the course of the same day he drove his new acquisition home, and by nightfall the 12-valve was sitting in the Mazda’s engine bay. “Getting it to fit was actually the easiest part of the swap. I just cut out what I didn’t need,” he added.

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Equipped with a Holset HX35W turbocharger, Comhghan tuned the fuel pump before fitting a boost pin to increase fuel delivery.

For a transmission, he used a Ford ZF S5-42 two-wheel drive gearbox with an E46 BMW 330D differential. The diff, with a 2.2.8 ratio, was sourced from an automatic model.

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I like how sedate it looks from the rear, until you look through the rear window.

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This is the view from the driver’s seat. “The overall aim is to evolve this car to match my skill, as I learn to drift,” says Comhghan. “I’m a beginner, and the car is at the early stages of being a drift car. So, all going well, the car will surprise people with its drifting ability at the same rate that I’ll surprise myself with what I can achieve as a driver.”

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“I’ll probably cage it, and add more grip/weight to the back end, while designing and building my own proper steering lock kit.”

Comhghan is very much a hands-on sort of person, his hydraulic e-brake setup created with the brake master cylinder of a Toyota RAV-4 and a 37mm spanner is one of countless parts which is testament to this.

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“Other plans are to stiffen the front up a lot, replace the injectors to get more fuel to the engine, and possibly fit compound turbos,” he added. “They’re not necessary, I’ve just always wanted to mess with a compound setup.”

The RX-8 is the epitome of backyard engineering, and it’s all the better for it. It’s that quest to do something, just because you can. Of course, there will be bemoaners, but I hope that most can appreciate this for what it is. Absolute lunacy.

Still, at least it’s not another V8, right?

Paddy McGrath
Instagram: pmcgphotos
Twitter: pmcgphotos

Cutting Room Floor

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I love it. I bet it's a hoot to drive.


It'd be a different story if it was an RX-7, but the RX-8 was so shit the only way you could make it better was to slap a diesel engine in it.


Best idea ever.

Matthew Everingham

I love it when people break the rules.

Subscribed for comments.
Popcorn ready. Backup popcorn waiting in microwave.


I always want to put a duramax into a Commodore and then put Chev badges on it! Just to take the piss out of all the bogans!


Hahaha, insane! :-D
For all who would complain, just think, better to drive it with a diesel or to let it rot. Definetly a fun car. How much did the engine add to weight?


That engine is roughly 1000lbs dry, depending on configuration. Not exactly a weight saving swap.


I see. I know diesel engines ain't kind of light. Well, than rest depends on hp to weight ratio. Is't that engine a problem for drift? As far as I know diesel engines are kind passive, it might not behave well for example on throwing back of the car on the other side for curve changing. But, definetly sure it has momentum to start a drift even without e-brake. :-D


Diesels passive? I don't know if that's the word I'd use to describe gobs of low end torque.


i'm all in for swapping wankers to reliable piston engines, and this one has torque as well. +1 !


The car is cool, the swap a pretty original idea, but ew, that engine runs so dirty.


its awesome


anything better than the renesis engine :P


and I thought I was the king of Frankenstein.

this goes to show, that people will do anything with anything and a little ingenuity.

he built a drift car on the cheap because wankel motors are premium and expensive and still kept the same dynamics.

this is a pretty rad build, took alot of thinking and it would be cool if this was someones engineering class project.


kept the same dynamics? this monster is front heavy as shit. the engine is 500kg dry. twice as much as even basicly any decent v8, not to mention better alternatives.
took alot if thinking? then what do you think of real, engineered drift cars? piece of cake, right?


Completely stupid and pointless, and that's what makes it awesome. Bonkers and I love it.


I'm no deisel fan but this is RX-8 is one of coolest I've ever seen. I'm also really into that madmax like front bumper delete


Man I'd love to sit shotgun while this thing is sideways. Must be intense!!!


i see torque.


"At least it's not another V8"

Imagine saying this to a Can-Am designer. *face palm*


Google: 'Flippant' :-)


hey, I figure, they just made another RX-8 reliable!!!!


it would be rx-hate if it had an LS and the owner giving us the finger. This is fine lol.


Haha front springs almost at coil bind static. Thing is going to gobble front wheel bearings, ball joints, tie rods, racks etc. fighting that weight.


literally nobody sees that except us. you already got your proof in their previous update video. steering rack housing cracked open.


Second last paragraph :)


I love this stuff, this is what I call engineering. Everytime I see a new swap on the internet it pushes me to study, get a well paid job and start doing this kind of things. I'm not a diesel guy but this build its just awsome, purely awsome.


That's gas! :-D What's the road tax like on it?


RX-8 bodies with killed engine are cheap as..... in uk/irl. thats why Cummins. Overall, I'm not even mad. Even as a die-hard rotor-head.

Mazda WHY U don't Turbo Renesis!




I'm all for it.
The bonnet and boot lid seem completely pointless now... There's no front bumper, you could almost give the front end the open wheeler treatment


Dang man, that's some legit Mad Max-level crazy right there! I love it!


3500rpm. this project failed before it started.


Truly this is the #DevilsDonkey and we should all fear it (in a good way) I want one.

One day I will hope for a new Nismo spec Nissan Leaf in the driveway as my daily driver... but will have an S15 with a 3.9L/4BT (from the truck I currently drive) in the garage for weekends (Cummins 6BT powered R32 would be cool but maybe too far) Don't produce any emissions all week then kick 'em all out at once an a Saturday ;-)


Wouldn't ever be my choice. Personally, I wouldn't see this as an improvement in any sense. For me, it's rotary for life.


I'm a huge fan of this frankenswap.

Curious how much the F-R weight balance is affected?


A lot.


This is so wrong in so many ways...


Nothing special. In poland we have two or three diesel powered RX-8 :D
We have even one with 1.2 petrol engine from old Twingo :D Beat this (yes, i have photos)


So happy to see a write up of this car. I'm used to seeing Cummins engines swapped into old Land Rovers so stumbling upon this on Youtube was certainly a surprise..


oh wow I love the rotor shaped hole in the trunk for the rear radiator. that's cheeky


This is by far the "most pure" form of joy one can hope to achieve from a build. Challenging convention, and at the same time evolving as a driver. Maybe one day I can start a project like this, lunacy and all....