Pre Lean with a JPI in a Bravo

[kortopates]

1 hour ago, Dsal1 said:

I run my Bravo at 2200 RPM it is much better on the engine lowers frictional loss and gives more time for gasses to move in and out of cylinder. The prop is also more efficient at the lower RPM. LOP ops work just fine here and allows a higher MP for a given HP rating. Mike Busch also recommends low RPM.

Exactly, Lower RPM improves your ignition systems resiliency to running LOP and thus will allow running deeper LOP smoothly over a faster RPM. With the Bravo's challenged ignition system, it can really make a difference and has for many of my Bravo clients.

[alexz]

6 hours ago, Dsal1 said:

I run my Bravo at 2200 RPM it is much better on the engine lowers frictional loss and gives more time for gasses to move in and out of cylinder. The prop is also more efficient at the lower RPM. LOP ops work just fine here and allows a higher MP for a given HP rating. Mike Busch also recommends low RPM.

What is MP for 2200 rpm ? For long cruise ?

[carusoam]

Welcome aboard Dsal!

Best regards,

-a-

[rbp]

On 3/6/2020 at 5:07 PM, alextstone said:

Upon reaching cruise altitude, I set my MP/RPM to 29/2400, cowl flaps either closed or half open (usually about 16k or above) and my FF to about 20 GPH.  I then wait a couple of minutes for the engine temps to stabilize.  Then, I go through the ROP or LOP leaning procedure.  

Same, 20gph until stable, then fine tune. The reason is it takes a long time to stabilize TIT, but the fuel flow is instantaneous. 

[Rick Junkin]

I'm one of the Savvy clients Paul @kortopates is referring to.

23 hours ago, kortopates said:

Exactly, Lower RPM improves your ignition systems resiliency to running LOP and thus will allow running deeper LOP smoothly over a faster RPM. With the Bravo's challenged ignition system, it can really make a difference and has for many of my Bravo clients.

 

I posted this in another thread but repeating here for convenience.

Here's some JPI 830 data from my flight from Gatlinburg to Alton IL yesterday that shows some real numbers for a Bravo running 30/2200, 13.7gph and 40 degrees LOP TIT at 8,000 feet.  This power setting consistently yields an indicated airspeed of 143kts which gives me 180KTAS+/- in the mid to upper teens but the westerly winds at altitude yesterday were horrendous so I settled for 160KTAS at 8K. My #5 CHT is from a ring probe and reads 50 degrees lower than the OEM gauge, so add 50 to the #5 CHT value.

For reference I have GAMIs with a spread of 0.3gph at peak, Tempest fine wires (URHB32S) and a dynamically balanced prop/engine. This power setting is very smooth, much quieter and I believe less fatiguing. I'm meticulous with my maintenance and so far it is really paying off for me.

I'll add that I do the big mixture pull straight to my LOP fuel flow (13.7gph on my TIO-540-AF1B at 30/2200) and cross check the TIT and CHTs once they settle out and adjust as desired from there. It's one of the recommended techniques to get to LOP quickly and to use it you'll need to determine what that FF number is for your preferred power settings. Also I let the engine "rest" at 30/2200 with full rich mixture and cowl flaps open for about 5 minutes after a long climb before I go LOP. If I don't do this and immediately go LOP I get fuel pressure fluctuations at the lower fuel flow rate, presumably due to percolation in the fuel lines from the heat generated at climb power. On a hot day I will also run the fuel pump for that five minutes to keep the pressure up and assist the cooling process

If I want to find out exactly where I'm running with regards to peak TIT and also crosscheck the individual EGTs I enrich the mixture from the LOP side back to peak, and then dial the mixture back to LOP. That keeps me away from the high ICP zone. I do the peak check occasionally just to have another crosscheck that nothing has changed with the way my engine is running and to confirm I'm still where I think I am on the LOP curve both with TIT and individual EGTs.

Cheers,
Rick

 

Edited July 21, 2022 by Junkman
added detail about top of climb cooling technique

[kortopates]

Perfect Rick! Great details! ^^^^^

[thinwing]

On 7/20/2022 at 9:07 AM, kortopates said:

Exactly, Lower RPM improves your ignition systems resiliency to running LOP and thus will allow running deeper LOP smoothly over a faster RPM. With the Bravo's challenged ignition system, it can really make a difference and has for many of my Bravo clients.

I havent heard the Bravos lycoming ignition system as being described as "challenged"before...do you mean induction system??

[kortopates]

9 minutes ago, thinwing said:

I havent heard the Bravos lycoming ignition system as being described as "challenged"before...do you mean induction system??

No, the slicks pressurized mags are weak link in getting the bravo much leaner than 20F LOP; even with great mixture provided by Gami's. Ignition misfire typically sets in at about 30F LOP.
The Finewires and lower RPM help with this but don't solve it, 

Edited July 21, 2022 by kortopates