DA 170 gas engine forum/thread

[Phil.Griffin]

Excellent.. Thank you guys.

 

[Super08]

Robotech;10611 wrote: And they nailed it. One small hole was all it took. It's amazing sometimes how little it really takes to solve a seemingly large problem.

Yup, it completely changed how my engine ran.

 

[Phil.Griffin]

I want one of these on my next 37.5. The 150 does ok, but I'm thinking the 170 would be just about perfect.

 

[yakken]

That's good to hear. My brother had a early da170 that ran like crap. We went to dle 170 engines and have had good luck so far. Now that the da170 is fixed I would consider it again.

 

[Robotech]

The fix was implemented at least two years ago. I have had both the DLE170 and DA170 on the same airframe ( at different times-ha ha) and while the DLE170 was no slouch, it won't touch the DA170 performance-wise.

 

[kd4jaz]

All that information is good, however, the RPM will NOT increase with a tailwind as stated in the opening statement. Wind only affects ground speed. Otherwise all of the info is very helpful. My DA 170 on RE3 pipes is only turning 6050 with a Mejzlik 28.5x12x3B

 

[dhal22]

All that information is good, however, the RPM will NOT increase with a tailwind as stated in the opening statement. Wind only affects ground speed. Otherwise all of the info is very helpful. My DA 170 on RE3 pipes is only turning 6050 with a Mejzlik 28.5x12x3B

So a 4 year old thread but I'm curious, what makes rpm increase when you dive your plane towards the ground? Not a tailwind but still wind is affecting the rpms...... no?

 

[Bartman]

So a 4 year old thread but I'm curious, what makes rpm increase when you dive your plane towards the ground? Not a tailwind but still wind is affecting the rpms...... no?

When you're diving towards the ground your airspeed increases so the engine unloads a little and the RPMs go up. When you lift the nose to climb without increasing throttle, the airspeed goes down a bit which loads up the engine and so RPM's drop a little.

A headwind or tailwind wouldn't change the engine RPM, it's only airspeed that would do that.

To a lesser degree, a well designed intake can use higher airspeeds to force more air into the carburetor increasing RPM, which would be in addition to higher airspeeds unloading the prop both causing the RPMs to increase.

Think about when the engine is on the ground with zero airspeed, the RPM's are well below what the max will be in the air. That's because without any airspeed the prop has it's maximum air loads to work against so RPM is lowest for a particular throttle setting.

 

[kd4jaz]

When you're diving towards the ground your airspeed increases so the engine unloads a little and the RPMs go up. When you lift the nose to climb without increasing throttle, the airspeed goes down a bit which loads up the engine and so RPM's drop a little.

A headwind or tailwind wouldn't change the engine RPM, it's only airspeed that would do that.

To a lesser degree, a well designed intake can use higher airspeeds to force more air into the carburetor increasing RPM, which would be in addition to higher airspeeds unloading the prop both causing the RPMs to increase.

Think about when the engine is on the ground with zero airspeed, the RPM's are well below what the max will be in the air. That's because without any airspeed the prop has it's maximum air loads to work against so RPM is lowest for a particular throttle setting.

Barrman is absolutely correct, wind only affects GROUNDSPEED. For instance at WOT going downwind your airspeed is xxx, make a 180 into the wind your AIRSPEED remains the same and RPM remains the same but your ground speed changes, but the loading on the prop is constant. In a dive your AIRSPEED increases therefore unloading the prop.