SKUSA IAME 175 SSE Rule Changes

Billy was the only one smart enough to use the torque monster. :joy:

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Absolutely! Can’t knock anyone for running the best package for the ruleset. It’s why I ran a Sonik a couple times back in the day in mixed TaG even though I needed to strap on 100 lbs of lead to my kart.

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Stars still uses VP MS98L, a fuel that the SSE 175 had no trouble with. The 2021 ruleset doesn’t feature the exhaust spacer, and it was competitive but not dominant, where an organizer would want it to be.

As for USPKS, well, it’s amazing how quickly people’s minds change on engines, and how slowly they do on chassis. I remember seeing a 175 being used as a doorstop in a competitor’s shop this winter, then Billy goes out and wins with one and all of a sudden it’s like Mark Donohue’s Penske Porsche 917/30-KL out there.

So, before the loosening of the rules?

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Charles, why the multiple engine failures for Factory at the 2022 SuperNats? I take it they were 175s not Screamers (KZ), which Billy has also recently used.

I run the Euro version of the 175 (with an electric starter) which came as standard with the Tillotson HB-15A. I’ve had no end of problems trying to deal with high EGTs, including on sprint tracks (like peaks well north of 700 C (1300 F)). Long track I’ve simply seized (not the greatest experience at speed). The alternative is to run super rich on the high needle, but it becomes impossible to drive (rich bogs etc) and/or requires mid race tweaks (far from ideal). I’ve since gone back to a Dellorto (36 mm in our Australian homologated case), and no issues.

Yes, that solves a problem, but now I’m back to mid event jetting and needle changes, just like my Stock Honda (which is a shame).

You’ve said previously that Billy is still working with/using the Tillotson. Any free tips/experiences to share. Why the success between then and now? And has the team come close to going back to the Dellorto (slide) - albeit I think you need to use the 30 mm than the base Euro 36 mm?


The 175 engine failures were caused by an inappropriate fuel and an engine that was more sensitive to the issues it had than its competitors.

If you’re getting EGT spikes you’re getting detonation. If EGT is extremely sensitive to needle tweaking you’re going lean due to poor fuel evaporation. EGT will gradually rise on straights and anything over 1150 F (625 C) should allow clean running the whole way up. If your fuel is below 100 RON, or if you have an initial boiling point more than 20C above your ambient temperature, and you’re allowed to change it, this will be a lot more effective than carb/squish/timing changes. X30s only need 95 RON fuel…

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I think this is a big part of it. IMO, best thing is to at least not start talks with teams and engine builders until this week. Everyone, and I mean everyone, in the industry was burnt out, tired, and probably sunburned from 5 weeks straight in Orlando. Then to have an all-out ass kicking on Sunday to cap things off, those who lost are pissed.

Nobody I think had an issue with Billy hovering the top 5 on the thing last year, or even if he were to have won a race on the 175. And on the flipside, there’s only minor grumblings about the typical superstar TM engine that shows up at SuperNats, which last year was in the hands of race winner Pedro Hiltbrand.

Difference from Pedro to Billy is you can actually buy Billy’s engine. You won’t get Pedro’s.

But, you won’t get free engines from IAME like you can if you’re Danny with Vortex, AJ with SRP, PSL with TM, etc. So there’s pros and cons. Those guys can’t go out and run on the 175 in their eyes.


Well SKUSA have ditched it for the protour too so I guess that’s the end of that (at a national level).


Great. Now my engine is prohibited, so there goes my SuperNationals run as a driver.

Makes sense. At this level you can’t have multi-format racing without issues arising pretty quickly.

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Only the pro shifter class. Masters is still using the SSE.

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The first S in SSE is “SKUSA” ! The abbreviation is of “SKUSA Shifter Engine”.

“Super* Shifter Engine”

I believe it’s based off a 175cc engine run in Europe but detuned for reliability

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IAME West calls is SKUSA Shifter Engine. I’m sure we can guess why.

Everywhere else it’s Super Shifter Engine.