I have fuel injection, the MP/FF factory instrument as well as a digital fuel flow. On take off roll i adjust the fuel flow on the digital instrument to what it calls for on the factory gauge, seen here:

http://tinyurl.com/35c3ded

Zane wrote:

mr scout wrote:Just go buy a manifold pressure gauge for a twin, leave one side unhooked lean till the needles match you will be at full power. So easy a caveman could do it.

So what is max power? What's the true relationship between power and manifold pressure indication?

.

Zane in a naturally aspirated engine the manifold pressure isn't going to go above what ever altitude your at. Lets say your at 6000ft and the unhooked side of your gauge shows 24" If your engine is running way to rich or way to lean your manifold pressure isn't going to get to 24" Peak power is in most cases between 25*-100* rich of peak. Which will give you maximum manifold pressure deflection on your gauge or in this case the required 24" Remember fuel is cool so many manufactures use fuel to keep from overheating the engine.

The little TO-360 requires 24gph on take off and climb to keep it cool but can come back to 14 gph once at altitude, getting it to run on 24gph requires manipulating the mixture and throttle until the boost is past 32" then full rich + boost pump and pull throttle back as the turbo spools up to 42" when your rolling.

Most of the stuff we fly doesn't really care longs as its close. Like others have said most Cessna's are at the first finger joint leaning at cruise power on the ground is less than full power but your probably close enough to get above the trees.

First I have to (full disclosure) say I don't know much about MP and all its variations/implications/etc.
But this guy appears to:

http://www.advancedpilot.com/downloads/prep.pdf

Better yet, he simplifies it to a level I 'think' I understand.... ...... (some of ....).........

lc

I'm confused. I am actually interested if anyone can steer me right here.

I guess I still don't see MP as an indicator for mixture. There is a relationship between throttle plate position, RPM, and MP. Given any two of these, there is a unique value for the third. I don't see how mixture enters into the equation. The prop generally regulates the takeoff prop RPM, and the throttle is set the same (firewalled). If the mixture is so bad (lean) that the prop reaches the fine pitch mechanical limits and you begin to lose RPM, the MP will actually go *up*, not down. Any engine with this configuration will barely run.

At cruise, if you drop RPM while keeping a constant throttle plate position, the MP increases as anyone has seen. When I lean at climb or cruise, I don't recall any variation in MP. Changes in AS do make very small changes in MP due to ram pressure (less than 1/2" increase in a 182 from Vx to cruise speed). And a new air filter robs about 1/4" or so (paper ones actually being very slightly better than Bracketts), while a really, really dirty filter steals as much as a 1/2". Some Mooneys I've flown have a filter bypass that adds under 1/2" MP at cruise.

Again, very rough guestimates on mixture for takeoff will yield ground roll distances and climb rates within a few to several percent of optimum. I consider the situations I've placed myself in where this was even remotely relevant for my safety as serious personal errors in judgment...errr...learning experiences.

What am I not seeing here that seems to be obvious to everyone else but me? Does anyone else see a MP/mixture connection? Why not set mixture to the rough "finger" settings and focus on a safe takeoff, keeping the rocks and grass off the prop?

How bout this. Next ski takeoff ,no flap start with a left turn. Cruising along ,waiting to add your quick blast of flap,you decide to settle into a little bit of technical Leaning/ Richening procedure to make it Just right.Boom! Launch into the air on a big ol drift you never saw.Here comes that flap u wanted followed by a Super slow motion slight adjustment of the mixture. Really ?like gump says an o470 or something similar .Save the effort, focus on flying, and as the Infomercial says " set it and forget it" ....( within reason of coarse)

Lowrider,

You are obviously an Aeronautical Genius!..... All these years,.... I had no idea!,... So if I put a Nitrous Sticker on the side of my cowling will my takeoffs be shorter???? By how much?

If I use every bit of power available,.... and I push the throttle THROUGH the instrument panel,... trying to takeoff from one of Quinn's ridiculous homemade strips, will I gain 23.637 HP????

Please enlighten me!

Splash

A lot of what Sparky said made sense, but adjusting mixture during the high-workload part of a take-off made no sense to me. I do a rolling run-up on grass/gravel, which includes setting the mixture approximately. But I wait to fiddle with fine-tuning it until I'm in the air, the flaps are up, and I have the time to glance at the guages instead of the trees.

Cary