RV-12iS Details

[RFSchaller]

A deficit of tact and social grace is all too frequently the price for genius!😜

[Crafting N112DR]

Here is a little tidbit that I got from Ryan from Vans at Airventure. The new RV-12iS has the wiring harnesses traveling down the left and right sides of the fuselage. They are not routed down the center of the fuselage like the current version. Definitely a safer design then current version which is routed next to the fuel lines.

[croner15]

Originally Posted by rolick22

Here is a little tidbit that I got from Ryan from Vans at Airventure. The new RV-12iS has the wiring harnesses traveling down the left and right sides of the fuselage. They are not routed down the center of the fuselage like the current version. Definitely a safer design then current version which is routed next to the fuel lines.

Did they happen to have any performance numbers from their trip out there?

[Crafting N112DR]

Originally Posted by croner15

Did they happen to have any performance numbers from their trip out there?

There are some performances numbers on the new RV-12iS site.

https://www.vansaircraft.com/public/rv12iS.htm

What are you looking for?

[croner15]

Originally Posted by rolick22

What are you looking for?

I was just curious about their real world numbers flying it out there. A few years ago, I recall they had a pretty good PIREP from their trip in the 14A so I'm hoping to hear something similar.

[Mich48041]

The iS engine gets hotter even though it uses less fuel. The explanation is that the ULS engine does not burn fuel efficiently. It wastes fuel. That unburned fuel helps cool the engine. The iS engine does not have fuel cooling, so it runs hotter.

[DaleB]

Well, yeah. A leaner, more efficient burn raises temperatures, right? It's not just EGT that goes up.

[rv6ejguy]

Originally Posted by Mich48041

The iS engine gets hotter even though it uses less fuel. The explanation is that the ULS engine does not burn fuel efficiently. It wastes fuel. That unburned fuel helps cool the engine. The iS engine does not have fuel cooling, so it runs hotter.

There is no basis for these assertions. Lower fuel burn for the same TAS means higher thermal efficiency and that means less heat out through the exhaust, oil and cooling systems as I said before.

In my bench testing on the carbed 912 engines while developing EFI back in 2007, I measured the average AFR with a wideband at high power in the 12.6 to 13.3 range. This is approximately best power mixture. Extra cooling would be had only at mixtures substantially richer than this- in the low 11s.



For reference here, .09 is about 11 AFR, .08 is 12.5 AFR and .06 is 16.7 AFR.

To get 20% better fuel economy, you'd have to be running well LOP (16/17 AFR) with optimized ignition timing. This will drop both the EGTs and CHTs- nothing is running hotter. This would be about 25% leaner than best power and you'd lose something around 5-8% power depending on ignition timing, which will cost you some speed.

You could also advance power for the same speed (more MAP and/or rpm) and still get that better fuel economy over the carbed versions.





912 EFI running a decade ago on our test stand. One of our customers who does flight training has over 1700 hours now on his EFI/912 and we have dozens of others with many hundreds of hours each. This was all long before Rotax released their 912iS. Our testing, verified by an authorized Rotax partner showed a 5-7% gain in hp over the carbs and slightly lower fuel burn at similar AFRs. We also saw the EGT spread close from 150 degrees to 30 degrees. The carbed engines have a well known mixture distribution issue which mostly goes away with EFI.

We also provided the EFI for the first twin engined EFI/ Rotax 912 aircraft in 2008.

[deene]

Just returned from the show and am enjoying a Spotted Cow in the dorm...

Over heard Rian commenting at the show that the "is" showing some nice fuel economy over the uls...some 20-30% improvement, depending on altitude and power setting. Even half these numbers would be very welcome...

The new ship is really nice, with many small, but important improvements aside from the engine, i.e. tank, gear, cowl, canopy latch, console, handhold, cup holder, etc.

Deene

[rvbuilder2002]

I don't know enough about engines to explain why, but the iS engine that Rotax currently sells does indeed require additional cooling capability when compared to the ULS ( the effort required to modify the original cowl exit area, and other details wouldn't have been done if it wasn't necessary).
Representatives of Rotax have confirmed this and have said that many manufacturers have had to make changes to deal with it.

The final design of the RV-12iS allows for a climb at Vy to 10000 ft on a 100 *F day with temps staying in the normal range.