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Sneak Peek- A look Inside Mad Mike Whiddett's Radbul MX-5

by Mike Kojima

A few weeks ago we were fortunate enough to get a close look at the car that we think is perhaps the most radical and innovative drift car ever built, Mad Mike Whiddett's Radbul Mazda MX-5.  After a 5 year absence, Mad Mike is back on the US drift scene with a car built for today's exceedingly competitive Formula D environment. 

The Radbul is out to break many suppositions about how a drift car is supposed to be and shows great promise. The Radbul is different from other cars in many aspects from its size, power plant, power level and weight distribution.

In it's first US events the car has shown plenty of promise.  New car blues have given many well established FD team fits and although it's clear that the Radbul is not fully dialed in yet, it has shown hints that it will be perhaps the deadliest drift car ever built once it has some development time.

What do we find so fascinating about the Radbul, well let's check it out.

 

How do we afford to have Larry Chen take pictures for us?  Get Larry Chen pictures of the Radbul in action via Red Bulls PR department! The Radbul is a beast, it can change directions faster than any current car and is the fastest accelerating car in Formula Drift.
The heart of Radbul is the 26B Rotary engine.  The 26B is a 4 rotor engine and was previously only available to the factory Mazda team where it was used for Prototype racing.  The 26B in Radbul was the vision of Pulse Performance Race Engineering or PPRE.  PPRE made the bespoke components for the engine such as the unique 3 piece eccentric shaft and some of the castings that made the consumer version of the 26B possible. The amazing thing about the PPRE 26B is its reliability. When other rotary powered teams have faltered and had reliability issues tying to squeeze FD competitive levels of power out of the 13B or 20B, the 26B seems bulletproof and has kept on giving with no signs of distress all season long!
Yup, 4 rotors right there.  The equivalent of two 13B's connected together. Although it's a huge engine as rotaries go it is still pretty compact as far as powerplants in general.  When you consider how much power the engine makes, it is a lot of power in a small place.  The beautifully fabricated intake manifold is built by PPRE using a Plazmaman big throttle body.  The trick charge pipe clamps are by Plazmaman as well.  The eccentric shaft bearings are fed oil via the middle galley on outward by these external oil lines from the drysump system.
The 26B is boosted by twin Garrett GTX40 turbos. Pretty appropriate for the power level.  The car makes 1032 horsepower on low boost and has the potential for over 1500 hp.  On low boost the engine is pretty mildly stressed which is responsible for the car's reliability. The engine uses stock rotors and 3mm factory seals, nothing exotic. Mike reports that the engine isn't laggy and has a wide powerband.  You can see that the engine is quite compact and sits behind the front axle centerline even though the firewall has not been modified as per FD rules.  A low stress turbo, compact 26B 4 rotor seems like a viable powerplant for many potential classes of racing in many different cars.  Time Attack car anyone?
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Comments
Dan DeRosia
Dan DeRosialink
Monday, September 21, 2015 6:06 AM
Will take more time to have a more in-depth thought on the rest, but what do you think they're doing with the front roll center relative to the rear? Knock-on effects from spring rates compensating for the unusual weight bias maybe? I mean, they fabbed uprights so they could have put the roll center almost anywhere they wanted, and I'm not going to assume any build at this level is ignorant of geometry effects...

Also really do wonder about porting on the engine and what irons they were using. Typically the homebrew 4-rotors are peripheral port because (among other reasons) the Mazda non-20B center irons have smaller intake ports than the end irons, so the middle two rotors end up with less potential port area. 8 intake runners on the Radbul engine means side intake ports though. If they picked the right irons though, I suppose it might not be too off - obviously it works pretty darn well.
Mike Kojima
Mike Kojimalink
Monday, September 21, 2015 8:40 PM
I asked about the porting and it's proprietary. We can respect that. Personally I think this is one of the coolest, most reliable and the most useful power Rotary ever built.
Dan DeRosia
Dan DeRosialink
Tuesday, September 22, 2015 5:46 AM
Oh sure; I don't expect I have any right to know all the details, it's just interesting to speculate when it's obvious something unusual is going on. From power per rotor, fuel choice and turbo size, I wonder if they're using boost more than rpm to make power, at least compared to big power rotary orthodoxy. I'll leave out speculation on what parts combo they used - as I said before though, obviously it works.

Something I noticed - no sway bars. How unorthodox is that for drift setup, and could that be related to the choice of front roll center? Spring rates front to rear are going to have to compensate for the weight distribution, maybe there wasn't room for a good sway bar setup so that's the compromise they made to get the balance right? Like I said before, fun to speculate.
Mike Kojima
Mike Kojimalink
Tuesday, September 22, 2015 9:23 AM
I don't want to comment on the suspension too much if you know what I mean.
Mike Kojima
Mike Kojimalink
Tuesday, September 22, 2015 9:24 AM
I think this car should be called "slate wiper" instead of Radbul. At least it has the potential to be that.
Dan DeRosia
Dan DeRosialink
Tuesday, September 22, 2015 9:41 AM
Sure thing; appreciate that you can share as much as you do.
Dan DeRosia
Dan DeRosialink
Tuesday, September 22, 2015 5:15 PM
Did some detective work on publicly available media. A bit funny actually - I've come across some dyno sheets in videos, but the RPM scale is blurred. Something interesting is going on there, I wager. And I know I'm not going to get an answer of what, but I just want to say that it doesn't look like a "garden variety" 4-rotor setup (if such a thing can be said to exist) from everything I'm seeing.

Interesting too is looking at the FD rulebook and the visible tires, it's not like it's a flyweight car. Having been underneath an NC MX-5 a lot recently (albeit rather less power) I really have been pretty impressed with the general design.
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