4 Rotor AWD FD RX7 | Rob Dahms 1000HP+ Quad Rotor Build [TECH TALK]

4 Rotor AWD FD RX7 | Rob Dahms 1000HP+ Quad Rotor Build [TECH TALK]


– While there’s always plenty of fresh builds
to check out at SEMA, one of the ones that I was interested in having a look at is Rob’s
26B or four rotor powered FD RX7. Now if anyone’s been following Rob’s
build on his YouTube channel, this build has been in progress for some time
now but it’s now at a point where it’s actually starting to look like a car,
it’s got an engine in it that runs so it’s a pretty exciting time. We’re here with Rob to find out a little bit
more about this build. So Rob, five years on the build so far? – Five years since my original dream was
conceptualised. – OK so when you take a completely stock
standard FD RX7 road car and the path to get it to what we see behind us
which is essentially now basically full tube frame four wheel driver, four rotor
turbocharged, that’s a bit of a stretch so can you tell us how that progressed,
or was this exactly what you had in mind right from the outset? So initially what happened was I had my 20B,
three rotor street car, stock chassis and my brother beat me in a street race with his
R35 GTR and the problem was traction. And so I was like OK, he’s got two more wheels
driving the vehicle, I need to play his game. And so that was the seed, the kernel that
started the desire to make the build a street monster and I didn’t know much about
fabrication, I saw a lot of pictures but it wasn’t until Gymkhana 7 was released in 2014
that Ken Block was drifting an all wheel drive custom Mustang and I reached out to the guys
that had built that to figure out how I could do something similar. – Alright so four wheel drive FD RX7,
at least to the best of my knowledge, I haven’t seen another one in the world
so when you’re starting with a fresh set of paper, obviously you just talked about
Ken Block’s Hoonicorn obviously giving you some inspiration there, what made you
decide to go with the combination of drive train parts that you’ve got here. – Yes so what happened was, ASD Motorsports,
which was ran by Ian Stewart who is a kiwi, he used to work for Rod Miller, at least job
shadowed or whatever the case is. And so I was inspired, as soon as I told him
my idea. he said you’re crazy, I love it, let’s work together and so he supplied me
a lot of information that encouraged me to move forward so maybe I bit off more than
I could chew at that point but it was the way to accomplish my goal. So then it was OK let’s try and use as much
of the Hoonicorn drivetrain as possible, none of that worked, zero, absolutely zero,
the SADEV, that’s meant for rallying, his car has a top speed of 150 mph and so
then it came down to how can I solve the drivetrain issue so I actually reached
out to Hollinger and they said hey we have an RD6, six speed sequential that
works with Mad Mike for the rotary side but then on the back side a lot of
Australians use it for their GTRs and so I was like OK that’s a potential solution. – Yeah so that has been a popular choice,
personally one of the cars I was involved with back in the day, R32 drag car ran exactly that
combination with the RD6 sequential with basically the Nissan transfer case box
at the back of that so that gives you your four wheel drive transfer case then you’ve
got your driveshafts running forward and back. So tell us about the rest of that drivetrain,
what have you got in terms of the rear diff and the front diff? – Yes so the differentials were both going
to be BMW initially and so the front still is. We’re running 3.65 ratio but then a lot of
people covinced me to use a Winters Quick Change like a lot of the Formula
Drift cars use. I was leaning towards that because of the
quick change ability to swap out gearing and there’s a lot of R&D left on this car
so why not be able to fine tune quickly? – So you’re not going to plan on running
the same final drive front and rear, so you’re going to actually have a split
between that so essentially there’s going to be some amount of slip in that centre
differential? – Right so right now they’re almost
identical, one’s 3.64 the other’s 3.65 so there’s that slight inconsequential
slip but I’ll turn off the front while I’m testing the rear ratio to feel powerband
issues. – So I think that’s the important things
as well to mention there with that R32 GTR, or the GTR transfer case, it isn’t
a mechanical fixed split, it basically is a rear wheel drive gearbox and then it has
a train drive to the front and using hydraulic pressure you can apply more
or less pressure to put more or less drive to the front so how are you controlling
that, are you varying that or are you going to run a fixed pressure for a fixed amount
of front drive? – Right well there’s two approaches, one is
that I’m going to run the stock Attesa system and that has a lot of the inputs
that I’m looking for, wheel speed, yaw and all the other sort of controls but I do
want to make sure I can control that. And like you said, the fixed ability, I might
control it with the hydro brake and also being able to set it on/off, 50/50 or 100/0,
that’s going to be something that’s going to shake down throughout the videos. – Alright so four wheel drive drivetrain,
we’ve kind of covered that off, I want to get into the engine but before
we talk about the engine, the fact that it’s now essentially fully tube framed,
was that essential to fit all of the components or was that in terms of just
getting things where you wanted them to be and getting the weight down? – So initially I built the vehicle in CAD,
that was my goal was to see if it was possible within a 28 inch wide frame of
the RX7 and it could. It would have been very difficult,
things would have been shaved but I could have done it. And then the next questions became
length. Well the GTR transfer case would be directly
under the butt of the passenger and I felt that would be really difficult and the car
is meant to have more than one person, emotionally that’s what I wanted and so
extending that vehicle put the transfer case closer under your knees and that
pleased or that satisfied my requirements. And of course a longer vehicle has better
stability at high speed which that’s one of the big boy adult goals that I want to
do with this vehicle is break Mazda’s ** record. – That’s a big aim to go for but you’ve
probably got a pretty good package to do it. Now that engine, the four rotor, again
there’s not a lot of quad rotor engines out there, Mazda obviously use them
themselves in their Le Mans prototype car or their Le Mans winning car I should
even say. But doing this in the aftermarket,
is a little bit problematic, there’s a few people making the components. Can you talk us through what’s gone
into this particular engine, ’cause I know you’ve had a few trials
and tribulations along the way. – Very much so, one of the things I’ve
come into is that I’m a very public person, I share both my successes and my
failures because that shows the younger audience, the people getting into the
rotary world, that there are people that are doing these superlative things but
making mistakes. So the problem I found is as I pushed the
ceiling further, I realised that you’re starting to get into race teams that hide their
secrets. They don’t want you to know their
competitive advantage where really to me I don’t need a competitive advantage,
it’s YouTube, I’m not racing. That has been probably one of the biggest
challenges that you know that there are groups out there, a handful of people, but
they’re very careful on how they share information. That’s why I’m kind of excited that as I
find things out, I share them with the world and that helps the rotary
community as a whole. – Definitely there is a lot of secrets as I’ve
seen that go into producing a reliable rotary engine. Now this one’s actually come from pretty
close to our home, from Carl Thompson all the way in New Zealand. So can you tell us how that deal came
about? – Yeah so Carl has been a friend of mine for
a long time and when my first engine stalled in production, I still have about 98%
of it, but there we concerns about it being non billet, it’s the traditional irons were
grafted with the bearings. Then the question was OK has billet
improved enough to produce reliability? They can produce power on the drag strip
but can they produce power reliably? So this is one of the very first, it’s the first
in the United States but one of the very first billet four rotors to run and as that,
Carl has told me in secret, in confidence that there are a lot of experimental things
on this block. So being in my spot, the experimental
aspect is kind of worth the risk because of the YouTube payoff, could be worth it. – Just to give some background info for those
who aren’t aware, Carl used the four rotor in his previous drift car which was a
Toyota Aristo. For those who are interested in learning more,
we do have a video that we can link to about that however we’re talking about your car
here. I want to get back into this engine,
so the billet versus the cast plates, so can you talk us through, first of all when
you’re putting together an engine that never really existed off the showroom floor
from Mazda, what is required to make a four rotor engine out of a 13B or even
20B? – Absolutely well speaking first about the
cast approach, you actually take more bearings and put them further inside of
the motor, otherwise that eccentric shaft will flex and you start having weird issues
with the rotors. The current solution is to put bearings on
the second and fourth irons so that way you constrain it a little bit more. There still is not, in the vast majority
of four rotors, a bearing in the very centre iron, that is something that might
be slightly different in this motor. – Alright so you’ve talked about the
modifications there necessary, obviously it’s a custom billet eccentric
shaft as well to go along with that but then the limitations of those cast
plates, where do we see the reliability problems, what actually fails and why do
they fail? – Yes so what happens is because now
you’re putting bearings inside of these cast plates that weren’t supposed to
be load bearing like that, they will shatter and shear because of that new piece grafted
into them. As for billet, I don’t know the answer to what
fails first, I don’t know what the weakest link is and that’s kind of what we’ll find out
together. – It will be interesting to see I mean billet
obviously in the piston engine world has become the go to for a lot of the import
guys making big power. I can’t personally see any reason why it’s
not going to work for a rotary and we have seen some pretty impressive results
from some of the rotary engines already running billet in drag applications. Now in terms of power levels, what are you
expecting out of this when it is all fully dialled in and you’re giving it as much boost
as you can? – Absolutely so the issue for me has been
YouTube pays to be extreme and even though I’m a crazy person willing to try
something weird, it’s always been grounded with some sort of logic and so there’s a video
out there, old video of a four rotor doing 1664 at the crank on an engine dyno and so
my goal is to exceed that. – There’s no point being second best right? – Exactly there’s no point in that and of course
daily operations, I shouldn’t say daily, but when I go to use this vehicle on the
street, right now you’ll see I have a very small exhaust housing on this to make the
nastiest 1000 horsepower to the wheels possible but as we go, the first thing I’m
going to do after SEMA is an engine dyno environment, all AB testing, every exhaust
housing and tuning as we go. – Let’s talk about that turbocharger,
what actually have you got bolted onto it at the moment? – That is Garrett’s largest ball bearing
turbo, it’s a 106 mm turbo. – So that should be a fairly healthy starting
point, what sort of power level can that turbo support? – Well for me it’s a little hypothetical. But compared to my three rotor where I
was running a smaller turbo, rotors love to breathe and so you really,
compared to a piston engine, that turbo is a 2800 horsepower turbo
for a piston engine, maybe 1300 to 1400 horsepower in a rotary. Anything above that would be potentially
being a little positive. – In terms of fuelling, what fuel is it going
to run on? – E85. – So a standard go to obviously, gives you
the fuel characteristics that are going to support that boost with relative reliability
on the engine. Now let’s go through the electronics package
of the car, what have you got managing the engine itself? – Yes so this is running the Adaptronic M6000
and I need all of those extra modules that the 6000 offers, not only for controlling the
fuel injection or the ignition but also I have, I’m a tuner and I’m an electronics guys by
trade and so I love management by measurement so they have additional
modules for data input and output. – What are you using for managing that
data, is that all through the Adaptronic or have you got a separate logger somewhere
in the car that’s going to be a central logging hub? – Currently the Adaptronic, my goal is to
get everything to Adaptronic and potentially in and out through CAN. So for example, exhaust gas temperature
is an AEM unit that controls each of the four but again run through the CAN bus so I have
a dash that can control logging but again I’m trying to centralise, keep it simple. – One of the problems, particularly with high
powered rotaries is unfortunately, they don’t have a great reputation for being
reliable, particularly if you’re sort of starting to push 1500, 1600 plus flywheel
horsepower. So is there anything in particular with the
Adaptronic you’re using as safety features to help basically prevent damage occurring
to the engine? – Absolutely so two of my biggest failures
on motors, I’ve had my three rotor running for years but as soon as I started messing
with fuel, I disabled, I personally disabled one of the fuel safety cuts and electronic
fuel system, caused me some problems. And so that’s one of the biggest things is
watching differential fuel pressure, allowing the Adaptronic to do its safety
cuts and me stepping away from that. Because by default it does do those things. I got involved and I caused myself some
harm. – So basically you let the computer do what
it was designed to do? – Yes very much so. – Now in terms of the rest of the fuel
system there, can you tell me what you’re running in the way of injectors and fuel
pump et cetera to keep the engine fuelled? – Yeah so what I start with is a dual brushless
fuel pump system with low and high staging. So I can go, kind of a binary situation,
both off, one on low, two on low, one on high/low and then both on high. That’s a Holley system, I think it’s a
TI Automotive pump and capable of almost six gallons per minute flow. – So when you say, with these brushless
pumps you’ve got a speed controller so depending on the controller you’re using,
you can have basically infinite control of the pump output, you’ve got high and low so
is that just two fixed levels of fuel flow output from those pumps? – That is correct yeah. – Alright look that car’s here, it’s at SEMA,
it’s running which is great. Obviously still a little bit of work left to
do on the car. When do you actually envisage this project
being finished and hitting the streets? – Well first step is actually getting the block
broken in. Because there are billet pieces,
so bringing them up to temp, down to temp together, multiple oil
changes, watching for bearings, all of those sort of things so I’ve got a
thorough break in process before I even think about any sort of turbocharger
introducing itself into my life. – So you’re essentially there going to be
running this naturally aspirated to start with and then adding the turbo back in? – That’s correct, I may run the turbo as
part of the exhaust but the intake system will be disconnected. – Now also just something I caught up on
there that you just mentioned, breaking the engine in, looking for bearing
material. And I did notice while I was looking over the
car, you’ve got a fairly unique take on an oil filtration system. So often when we’re trying to look for material
in the oil, we can have samples taken or you can cut the filter open which is a horrible
job, it’s really messy and it’s time consuming. You’ve got quite a unique way of actually
viewing if there is anything in the oil, can you tell us about that? – Yes so what I did is I purchased a clear view
oil filter and as long as that material is larger than 60 microns, it’s a mesh screen,
that as soon as the oil exits the dry sump pan, goes through the scavenging pump unit and
before it makes it into the tank where it could potentially sit and settle, it goes
through this screen and you can basically force air into there after it’s
running and see what’s sitting on that screen. – So a quicker way of catching onto a
potential bearing problem inside of the engine rather than waiting for the inevitable
outcome or alternatively cutting your filters open? – Exactly, I’m a big fan of, if you don’t look
at it, there’s no problem, but I need to face the music and see it ahead of time. – Yeah there’s one theory that what you
don’t know doesn’t hurt you but unfortunately seldom does that work out
when we’re talking about a very expensive engine. Now just because you did mention that
as well, I haven’t touched on it so far, the lubrication system on the engine is
a full dry sump system so can you just talk to us about whether that was a
requirement for this particular engine, could you not work with the factory Mazda
wet sump system? – Well that was something that Carl said hey,
I took what he said and that was one of those things that he was like, you need to do this. And of course I love to ask why but the
control I have over the system is wonderful. I have six lines, five lines, each of the irons,
each of the places that there’s a bearing, gets lubrication and it’s been wonderful
’cause even when we did the engine test on the stand, we were able to fire up the
oil pump and filter the system before even turning the block over. So that’s been a wonderful thing for just
taking steps, I love baby steps when it’s such an experimental system. So yeah having an external dry sump has
been a totally new experience to me but it’s been wonderful for preventing
damage. – Look Rob it’s an incredible build, we can’t
wait to see what it actually does when it does hit the dyno, thanks for your time and
if our viewers aren’t already following you, how can they get hold of you on your
YouTube channel? – I make it really easy to find me, Rob Dahm,
on almost every social media avenue and that’s where you’ll find me. – Perfect, thanks Rob. – Thank you so much. – If you liked that video
make sure you give it a thumbs up and if you’re not already a subscriber,
make sure you’re subscribed. We release a new video every week. And if you like free stuff, 
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About the Author: Michael Flood

100 Comments

  1. Man that Rob guy looks like he genuinely loves his job and what he does when he speaks, we need more guys with his energy in the car community/car industry. I don’t really even mess with Rotaries but I’m definitely giving this guy a follow!

  2. Rob is challenged and HE NEEDS YOUR HELP. Or it will be another 5 years. This would be a great project for you. I gave up watching his channel. You need to tune that car for him 🙂

  3. Been a while, but well worth the wait 🙂
    Been following Rob's build for some years, with his other projects also being worth watching – he shows pretty much everything, mistakes, frustrations and the joy when sh*t comes together and works, as he says in the interview.

    Diff' ratios should be the same if they're that close – I expect it to be rounding variations – easy way to check is a tooth count.

  4. Why, doesnt someone build a rotary motor bigger than the standard being used now, and 6 rotors design the rotors twice the size a billet block, is there a limit to the size and cant go any bigger or know has designed one, isnt it all about more power and speed,it would cost alot to design and machine, but technology and cnc machines make it actually possible to do, would it be to much power and not usable destroying drive train?

  5. A really good and honest interview with perfect questions watched it all the way through no skipping and was worth it for the knowledge

  6. Rob Dahm may not have the technical prowess of many of HPA's guests but damn does he have vision and passion. I understand when people get frustrated by his mistakes, I do as well, but they're a consequence of somebody willing to work outside of their comfort zone in order to accomplish something exceptional.

  7. Some haters here, but if someone can self fund a project like this without a hedge fund I'm impressed. I for one find him down to earth and honest…..we're not going to like every human on the planet, and I haven't met him personally! So who knows….

  8. What a sweet interview! Wow. I've been passively following/catching up on this build for a few months, but hearing this guy speak, with all the right questions being asked, has got me hooked. Such a sick machine this thing is. Utterly insane, all kinds of awesome! ??

  9. how the hell do you come to the place in your life that you're building a 200 grand car "for you tube" … mate from where I'm sitting your living in porn film

  10. What you have to keep in mind is that Rob was flat out for about 70 hrs or so by this point finishing up as much as possible and then going to LV. I'm amazed he managed to say anything intelligible.

  11. Damn, what a dream video, Two of my most favorite Youtube personalities Andre and Rob…This video flowed so well too! Fkn Awesome!!!

  12. Wilbert Anaya tuned a 26B that was on the New Ian long time ago and pushed 2,360WHP to the rears with a Microtech LT-16s ECU and I’m pretty sure he can tune for more HP now. Let me know and I set you up with him.

  13. Rob is a douche and he ruined that car. It’s not an Rx7 anymore, it’s a monstrosity made by someone with too much money and no brain.

  14. watching Rob because of the RX-7 built.. but the biggest part that nobody looks at the car hobby is the persistence the passion you have to get projects like this completed.. this building has been one of the most challenging builds that have ever seen and that in the engineering standpoint for the up and downs you go with a built like this the mentality that you have to have to see it through. to man the legend rob dahm

  15. Rob just ran it on the dyno, made like 550hp on 8lbs of boost at 6,800rpm, he plans on turning it up to 45lbs of boost and reaching 10,000rpm. I fully expect this thing to do rolling burnouts all day long.

  16. great content on an original design car. Rob is an awsome content creator as well. dont forget to check out his channel for updates on the FD! Rob Dahm

  17. Rob has just passed one of his major milestones! Check it out: https://www.youtube.com/watch?v=4P-F4kJEeSk
    Well done to Rob and his team, excited for all of you ?- Taz.

  18. Congratulations Rob for this awesome built.That was a big nightmare for you and the team but you never give up and realised your dream.

  19. I can only imagine Felix Wankel standing over this, smiling and shaking his head. Never once dreaming his Wankel Rotary engine would turn into a 4 rotor turbo juggernaut.

  20. He still has more work to do on the dyno as well so that number will continue to increase. Can't wait till they start track testing.

  21. Let's upload a video we did months ago that pretty much everybody has seen a variant of already right now right when Rob's 4 rotor just made a 1000hp All wheel drive to drive the likelihood of people watching are video because now the car is relevant again. Rob making car Relevant again = views of a old video = money in pocket without any lose. Well played.

  22. I’m frustrated this thing is taking so long as I want to see it ripping but as they say nothing good comes easy. It’s such a beautiful car you can see the time and dedication he has put into it.

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