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Discussion Starter · #1 ·
Check out this deadly quick Polaris Slingshot as it gets the jump on a sportbike for a great race to the finish! Driven by Bill Hahn Jr (who clearly needs to stay out of the rev limiter when he gets all excited!), this machine sports an off-the-shelf Hahn RaceCraft SST Stage 2X SlingShot Turbosystem running unleaded fuel. It's run as quick as 11.48, and still has more left! Learn more about the World's Quickest Slingshots in both normally aspirated and boosted form: www.hahnracecraft.com


 
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Discussion Starter · #3 · (Edited)
Good question! Thanks to a considerable amount of chassis development and track time, we've been as quick as 1.59 seconds 60-foot time, which rivals RWD cars of similar ET. The current combination will not spin the tire at all, so arguably, all a second tire and resultant complexity of a 4-wheel conversion would add at this point is more weight to tote down the 1/4 mile.

That said, my goal is to maintain the title of World's Quickest Slingshot, and its important to me to do it in traditional Slingshot configuration, so we can show what's possible without the extent and expense of a 4-wheel conversion. Which is not to say I don't respect the four-wheelers, but that's just not my mission.
 
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Discussion Starter · #5 ·
That is fast! Strip out as much as you can, lower it, laser align the steering, and put an aluminum pan underneath and air dam in front to reduce drag. (Ask me how I know... 🤣 )

Great job Bill, that's an amazingly fast Slingshot!
Thank you! I have considered gutting it for weight savings, but it's important to the overall mission to keep it representative of a fully-equipped street Slingshot, so I have resisted that urge. So far, the effort has been one of exquisite restraint; not only is this our standard off-the-shelf Stage 2/2X SST turbosystem, Slingshark is even still equipped with a stock clutch, albeit one I have modified for more holding power.

The engine is also stock, but with one caveat: it's a salvage yard engine from a 2006 HHR, identical to the 2.4 LE5/9 in Slingshot save for one aspect: forged factory connecting rods, which allow us to safely run 15 PSI of boost (so far!). We've taken these engines to 20 PSI in previous applications in Solstice and Sky with great success, so it's an established player, and for a total investment of $600, considerably more affordable than an internally built engine.

Overall, the goal with this program has to show the most potential with the least-possible money and effort exerted, thereby best exemplifying what a typical enthusiast can achieve with our parts and techniques. Rather than "throw the kitchen sink" at it, we are striving to show what can be done in a careful and methodical fashion while expressing the maximum Bang for the Buck.

That said, I like your aero comments. We did craft some carbon-fiber "gap fillers" which will assist in deflecting air away from the front suspension, and we've also removed the fenders behind the front tires to help clean up the aero drag. Can you please tell me more about your efforts with the undertray you touched upon?
 
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Under the engine area I have an aluminum pan with aluminum mounts which causes a heat buildup in the engine bay, so I have a real hood vent up top, block-off plate between the engine and dash, gutted down-pipe & aftermarket exhaust (Cerakoted). (Also a brake master-cylinder support and custom pads, because stopping is important.)

In my experience OEM Slingshots experience lift at about 85 MPH due to the open cockpit (depending on the windshield height/type and weight in the cabin) and then pushes down at about 105 MPH. That sets the vehicle up for instability due to a high center-of-gravity in that speed range. The pan greatly helps reduce that lift.

Similar to what Hahn offers, I also have tuned adjustable racing shocks to lower the SS, further reducing underbody turbulence, so there's now no rise at 85 MPH and it stays incredibly stable at all speeds. A laser-alignment is then needed to correct for geometry changes due to lowering.

It worked out so well I have two extra pans so if one was ripped due to a speed bump, wildlife, or brick (which was a common roadway obstruction a while back) I'd have backups; so far no damage. (No dented rims either--I have an extra set of Base rims with new rubber also).
 
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Discussion Starter · #7 · (Edited)
Under the engine area I have an aluminum pan with aluminum mounts which causes a heat buildup in the engine bay, so I have a real hood vent up top, block-off plate between the engine and dash, gutted down-pipe & aftermarket exhaust (Cerakoted). (Also a brake master-cylinder support and custom pads, because stopping is important.)

In my experience OEM Slingshots experience lift at about 85 MPH due to the open cockpit (depending on the windshield height/type and weight in the cabin) and then pushes down at about 105 MPH. That sets the vehicle up for instability due to a high center-of-gravity in that speed range. The pan greatly helps reduce that lift.

Similar to what Hahn offers, I also have tuned adjustable racing shocks to lower the SS, further reducing underbody turbulence, so there's now no rise at 85 MPH and it stays incredibly stable at all speeds. A laser-alignment is then needed to correct for geometry changes due to lowering.

It worked out so well I have two extra pans so if one was ripped due to a speed bump, wildlife, or brick (which was a common roadway obstruction a while back) I'd have backups; so far no damage. (No dented rims either--I have an extra set of Base rims with new rubber also).
Excellent info! Insofar as our chassis setup, to maximize traction and chassis reaction we have raised the rear and lowered the front, which has the additional benefit of keeping some air out from under the machine. That said, I don't doubt we could clean up the under-aero in the fashion of the pan you suggest. I hear you on the instability issues - Slingshot is about as aerodynamic as a Model T Ford, and even that may be an overstatement!

I even had a minor mishap at the track as the front upper fenders/hood begain their usual oscillating antics at speed. A chunk of the black hood filler piece broke free on the left side and smacked me in the windshield and helmet at about 100 MPH. I pressed on, never lifting, as I had a pretty good idea of what the flotsam actually was. To be forthcoming, the part was already cracked. All the same, I never expected it to fail in such a spectacular fashion! I suppose I should also employ the push-button hood locks which can help stabilize this region.
 
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Discussion Starter · #9 ·
Did you try the magnet trick in the front corners of the hood? For me it kept the flapping to a minimum. (I also added outboard stability bumpers to the rear of the hood by the latches.)
Good ideas. I'm old school, so I am even thinking about adding good old fashioned hood pins. Easy and affordable!
 
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