Rob Dahm, notorious rotary-powered car builder, has firmly jumped into the deep end of the pool with his latest project: The world's only 15.7-liter, tri-turbo Y12 rotary engine. If that doesn't make any sense, you're not alone.
Skip back 15 years when Tyson Garvin, founder and innovator at Apex Manufacturing & Design, got a wild hair up his ... you know ... and designed and built this insanely improbable Wankel engine with twelve rotors configured in a Y design.
Garvin built the Y12 from a solid block of 7075 aluminum – the same stuff used in NASA's Space Shuttle and the Saturn V rocket – due to its light weight and ability to withstand high stresses and extreme temperatures.
Why? Because his big-block Chevy-powered speedboat that he raced needed more power, of course.
He built the Y12 rotary to fit similar overall size specs and bolt pattern as the big-block Chevy, but as far as we can tell, the engine simply became an engineering internet sensation and never actually made it into his vessel – or anything else, for that matter. Even with its lightweight materials, the engine still weighs in at a hefty 830 lb (376 kg) or so. A fair bit more than the usual 680-750 lb (308-340 kg) cast-iron big block of the Chevy.
It did, however, make it to the dyno and produced some fairly impressive numbers. Like 800 lb-ft (1,085 Nm) of torque at 2,000 rpm. Or 497 hp (371 kW) at 3,200 rpm. Or nearly 1,400 hp (1,044 kW) at 8,500 rpm, all on 87-octane pump gas.
Garvin says the engine is designed to be run as high as 14,000 rpm. He reckoned that there are a number of ways the motor could be reconfigured to punch out insane horsepower figures, like 3,600 hp (2,685 kW) with a pair of turbos and race gas.
But this is all old news.
The new news is that Rob Dahm, the deep-end-of-the-pool guy I just mentioned, has the big Y12 Wankel on loan from Garvin and has been prepping the powerplant for a solid year-and-a-half to achieve those really big numbers Garvin thought his engine is capable of ... like maybe 5,000 hp (3,728 kW).
"'I want to see that thing eat,'" quotes Dahm in a YouTube video recalling Garvin's desire to see big horsepower numbers from the Y12 he built.
"And if that man wants to see it eat, it's gotta eat!" He continues, also explaining that Garvin was the reason why he'd decided to go with an even bigger turbo than was originally in the plan.
And not one, not two, but three Garrett G55 96 M24 turbos! He'll have no argument from us. Let it eat.
The engine is a tri-bank design with four rotors per bank, so each bank gets its own massive Garrett G55 turbo. These bad-boy turbos are designed for large displacement motors that put out serious horsepower. Think: 1,850 to 2,900 horsepower (1,380-2,163 kW) per turbo exceeding 40 PSI (2.76 bar) boost.
To accommodate the massive intake for three turbos, Dahm and crew had to redesign the fuel rails and exhaust, amongst other things. Given the engine is made almost completely out of aluminum – as are the fuel rails, intake manifold, etc – heat is the enemy and one of the beautiful custom 4-into-1 exhaust headers sit immediately beneath the intake manifold ... and between the fuel rails.
They've put in quite a bit of effort (and a lot of money) to make it as thermally compliant as possible, including switching from gasoline to ethanol fuel while testing – which inherently burns cooler than gasoline – but has its own issues. Like when running rich, excess water spews from the exhaust, or quenches the spark plugs. The end goal is to run the Y12 on methanol.
The team also had to tear the motor down to nothing when they realized it was having rotor clearance issues. After milling five to six thousandths off the rotors, they rebuilt it again, ensuring everything was tip-top.
During the Y12 test-fire, Dahm was able to reach 6 PSI (0.41 bar) of boost at 7,700 rpm at partial throttle with the turbos spinning at 47,000 rpm – far below their max speed of 88,000 rpm. But the team looked as though they were slightly apprehensive of really giving 'er the beans after an incident a few days prior, namely an explosion ... a bit of a ~200 PSI (13.79 bar) back-fire issue that blew the intake manifold apart when they attempted to start the engine for the first time (no one was harmed).
We can't wait to see what kind of dyno numbers this beast puts out when they really give it some throttle! And even better when they finally get it mounted into some sort of vehicle!
You can check out Rob's video here:
Source: YouTube/Rob Dahm