SKUSA Doubling Down on 175 SSE

I’ll be running Masters Shifter at NCMP. Would run the entire series if I wasn’t so crunched for PTO this year. :sob:

@WheelSpin

Yes, Dell’orto is an end user option on the engine. They ship with the Tilly, tho.

@Alan_Dove1

Well, looking at it from the distributors stand point, do you want to send 15+ $6000 engine packages out to Joe Bob’s house and hope he actually does all the races or sends the engine back? Using approved teams for possession and maintenance of the engine is a compromise to get the engine out to racers and a CYA for their investment.

Evan, that sucks that you can’t run them all! It’s fun being in the HMG tent with you, but I’m not looking forward to getting my ass handed to me by you at NCMP… :grimacing:

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He’s damn good at sim too. I’ve had to beat him off with a stick, repeatedly. I suspect with effort and a wheel, I’d be doomed.

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Believe me, if I could run them all I DEFINITELY would. I love the HMG tent environment as well, and can’t wait to be back in the mix! And think of it this way, you can look through as much of my data as you want when we get to NCMP :innocent:

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Whoo! Data!

Pass along some talent while you’re at it. :grin:

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KZ is still faster then IAME supershifter.
Cilinder size is tricky in cold conditions,i.e. you have to warm up the engine thoroughly.There’s little space between the sleeve and the cilinder wall.

Karters pitting out of their own vehicle/trailer, and not a teams’ tent, seems to be a quickly vanishing segment in sprint karting at the national level, and slowly encroaching into the lower-levels too.

The steel sleeved cylinder in the IAME will inhibit thermal transfer compared to an aluminum+Nikasil lined cylinder (eg. TM), so there’s that.

What I mean is that the outside cilinderdiameter is about the same as a 125cc
but the bore is 64mm,the 125cc 54mm so there is llttle room for water.
Seizing is a big problem.

What are the implications of this?

Could this be why piston clearance is so much greater for the 175 compared to a KZ? I’ve only seen seizing become an issue when break-in is rushed. I’ve personally gone through 5+ pistons with ~8hrs run time on each (some more some less).

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I think people talking about the reliability issues of the 175 are basing their assumption on the initial release that had the couple of problems (carb needles, etc) that have long since been rectified.

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Frankly, if it’s designed correctly, next to nothing. When seizing was mentioned, I thought maybe thermal transfer was a factor. Thermal transfer is inversely proportional to material density. Same goes for expansion rate. Since steel density > aluminum, the former will expand at a relatively slower rate as it heats up. Something to keep in mind when warming up the engine.

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Evan and Gerard
I think one should consider that the european supershifter and the Skusa SSE version have a lot in common, but are not identical.
First of all, since the USA version came out in 2019, it benefited from several years of reliability improvements that had already been made in Europe, in particular on cylinder coolant flow.
Furthermore, the Usa version comes with a bigger diameter con rod lower bearing, and therefore different crankshaft, that also does not allow for the fitting of an electric starter. To further increase reliability, a spacer was added on the exhaust manifold, to lower the rpms at which the maximum power is reached, and improve torque at low rpms, allowing for a wider utilization rpm band.
Finally, a 34 mm Tillotson carburetor, to avoid having to deal with a slew of different size jets, atomizers, etc etc
Because of all these differences, the performance of the european and usa version are not identical. On the performance side, at the 2019 Supernats in Vegas, the fastest laps were practically identical between the 175 and the kzs, even with a 10 lbs penalty on the 175. Furthermore, extracting the best performance from the kz at the limit, with its narrow powerband, should be considerably harder, especially for less experienced drivers. In any case, the engine was clearly not designed for maximum performance, but for improved longevity and ease of use.
On the use of an iron liner: the main advantage is that a 100% cnc machined liner will allow increased parity and consistency between engines, vs a cast aluminum version. Here too, the point is not absolute maximum performance, but as high parity as possible. Hope this helps clarify the situation.

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Evan and Gerard
I think one should consider that the european supershifter and the Skusa SSE version have a lot in common, but are not identical.
First of all, since the USA version came out in 2019, it benefited from several years of reliability improvements that had already been made in Europe, in particular on cylinder coolant flow.
Furthermore, the Usa version comes with a bigger diameter con rod lower bearing, and therefore different crankshaft, that also does not allow for the fitting of an electric starter. To further increase reliability, a spacer was added on the exhaust manifold, to lower the rpms at which the maximum power is reached, and improve torque at low rpms, allowing for a wider utilization rpm band.
Finally, a 34 mm Tillotson carburetor, to avoid having to deal with a slew of different size jets, atomizers, etc etc
Because of all these differences, the performance of the european and usa version are not identical. On the performance side, at the 2019 Supernats in Vegas, the fastest laps were practically identical between the 175 and the kzs, even with a 10 lbs penalty on the 175. Furthermore, extracting the best performance from the kz at the limit, with its narrow powerband, should be considerably harder, especially for less experienced drivers. In any case, the engine was clearly not designed for maximum performance, but for improved longevity and ease of use.
On the use of an iron liner: the main advantage is that a 100% cnc machined liner will allow increased parity and consistency between engines, vs a cast aluminum version. Here too, the point is not absolute maximum performance, but as high parity as possible. Hope this helps clarify the situation.

Steel v. aluminum should not be an issue here. Precision honing is a thing.

what causes the 125 to be faster than a 175? whats different on the engines?

I think it’s important to note that the 175 SSE for use with SKUSA is a lot different to the 175 super shifter in the IAME cup.

That said, my observation is that the track seems to determine which has the upper hand between a KZ and a 175 SSE when they are run together. Although I’m sure class weights play a part as well.

A KZ makes more power at the higher end of its RPM range whereas the the SSE is more of a “stump puller”, delivering more power lower down. We have dyno curves on the forums comparing an SSE and a TM KZ (Same dyno) somewhere.

It’s got +25% more displacement, so the power curve should naturally be wider.

10 posts were split to a new topic: IAME Super Shifter 175 Cutting out