Limbach L2400 engine

[vigilant104]

The 100 HP Sauer 2400 UL can have both aluminum and magnesium casing. The aluminum being 6-7 kg heavier (still lighter than most "ordinary" conversion with the default magnesium casing).

So, the aluminum 2400cc (2332cc actual) Sauer comes out to approx 181 lbs dry. Another comparison in the same cc range for a pre-built engine (at least for US buyers) would be a Scott Casler/Hummel 2400cc engine (it has the same bore and slightly longer stroke than the Sauer : 86mm vs 84 mm). Aluminum cases are available in the US, I don't know if Casler can/does build with them. It would be interesting to see a apples-to-apples feature/weight/power/price comparison between the engines.

Dave Clay has a Casler 2400 in his Sonex, last I heard he was satisfied with the performance.

I wonder if Revmaster will ever come to market with the long-awaited R3000?

The Sauer's and Limbach's are great looking engines. I suspect the "overhead" for getting them certified and complying with the documentation requirements shows up in their price (like Lycoming, etc)

[SvingenB]

Not exactly, the aluminium version is 75 kg dry, 165 lbs. The magnesium version is about 68 kg or 150 lbs. The 85 HP 2200UL is only 66kg or 145 lbs, not much more than a Jabiru 2200. The "default" 2400 is with aluminum casing, but I think also the 2200 can have aluminum. Sauer makes their own casings.

[rizzz]

One thing to note if you considering a Limbach or Sauer, the mounting points on the accessory plate are positioned differently than the AeroVee/RevMaster/GP/Hummel. You would need a custom engine mount for one of these. You can see the dimensions of one of the engines here:
http://www.limflug.de/downloads/datashe ... eet-en.pdf

[SvingenB]

Sauers don't have the accessory box. The stuff are mounted directly on the casing. They could make me an adapter to fit the engine mount, no need to make a new mount. They sent me pictures of one adapter, but it seems like a fairly easy thing to make yourself. I can post them here when I get home. Limbachs, I'm not sure. I think there are various configurations around.

[SvingenB]

It would be interesting to see a apples-to-apples feature/weight/power/price comparison between the engines.

I agree. But just one detail. All Limbachs and Sauers have a very short manifold distance from the carb to the cylinders, some have dual carbs, one for each row of cylinders. Rotax has a similar configuration. I asked Sauer (Martin Manthey) if they could move the carb to the same position as the Aerovee. He said sure, but doing that you will loose 5-6 HP.

[vigilant104]

Not exactly, the aluminium version is 75 kg dry, 165 lbs. The magnesium version is about 68 kg or 150 lbs. The 85 HP 2200UL is only 66kg or 145 lbs, not much more than a Jabiru 2200. The "default" 2400 is with aluminum casing, but I think also the 2200 can have aluminum. Sauer makes their own casings.

Thanks. I can see how incorporating the accessory case into the engine castings (and eliminating the ports/fittings used only in the auto) could save some weight. The Sauer HP is quite a bit more than the figures I'm used to seeing for equivalent displacement and compression ratio VW Type 1s, does Sauer attribute the difference to the induction system (short runs, independent carbs/FI, etc)? I know high-reving engines derive a lot of benefits from very careful "flowing" and porting, but I would have guessed there were less gains to be had at 3400 RPM: at those "slow" speeds there's plenty of time to get the charge into the cylinder, at least compared to the 6,000+ RPM engines.

[SvingenB]

Thanks. I can see how incorporating the accessory case into the engine castings (and eliminating the ports/fittings used only in the auto) could save some weight. The Sauer HP is quite a bit more than the figures I'm used to seeing for equivalent displacement and compression ratio VW Type 1s, does Sauer attribute the difference to the induction system (short runs, independent carbs/FI, etc)? I know high-reving engines derive a lot of benefits from very careful "flowing" and porting, but I would have guessed there were less gains to be had at 3400 RPM: at those "slow" speeds there's plenty of time to get the charge into the cylinder, at least compared to the 6,000+ RPM engines.

The cylinder has to be filled up no matter what the revs are. 2200 cc at 3000 rpm is equal to 1100 at 6000 rpm. Also the length of the manifold has to be tuned for optimal performance and matched with the timing of the inlet valves apparently. The Sauer also has hydraulic lifters. The combustion chamber is also very different on the Sauer, similar to the Revmaster I think (or so I am told). All the others use standard automotive tops that are optimized for higher revs.

Anyway, performance of the Sauer 2200 UL on the Groppo Trial suggests that it does indeed deliver as adverticed. The Sauer 2400 UL is only slightly stronger. The 2200 has a CR of 8.8:1 and 80 HP continuous at 2700 rpm. The 2400 has a CR of 7.9:1 and 90 HP continuous at 3000 RPM. This is very comparable to a Jabiru 2200 with 80 HP at 2900 rpm (85HP at 3300 rpm) and a CR of 8.0:1

I know that the Sauer 1800 UL (1835cc, CR 8.5:1, 68 HP at 3200 rpm, 65 continuous at 3000 rpm) use the same propeller as the Aerovee. The Aerovee has the capacity of higher revs and thus considerably higher top speed, but still. During take off and climb a Aerovee does not perform much better than a 1835 cc Sauer.

These properties goes directly on the torque of the engine. The Sauer engines have a very pointed torque curve with a peak somewhere around 2600 rpm. So does the ULPower and the Jabiru. The max torque is about 210-230 Nm. The Aerovee has a flat torque curve from 2400 all the way up to 3400 rpm. but the torque is only 169 Nm at max (the Sauer 1800 has 165 Nm max at 2600 rpm). I would guess the Great Planes and Hummels are even "worse" since they run at even higher rpm, 3600. A flat torque curve is very good for a car, but not much use for an airplane. In an airplane it is better to have higher max torque in a limited rpm range. I'm no engine expert (but torque and power is well known to me through decades of working with turbines), it is fairly obvious to me that only Sauer/Limbach and Revmaster are specifically designed to run as aero engines, from an engine design point of view. The others are plain auto engines with aero peripherals. The max power is probably about the same, but the take off and climb performance with fixed pitch propellers will be much better with an aero engine design.