Fuel Boost Pump Useage With Takeoff At Very High OAT?

[EricShr]

Hi, I'm seeking advise from other Southwest Mooney Ovation owners on how to deal with VERY high cylinder temps on climb out at VERY high OATs (110-115). I have an Ovation 1 that has been converted to 310HP/2700. Fuel flows at takeoff are 27.5Gal/Hr. with GAMI injectors. Runs excellent LOP, idles at 700. At startup runs like crap with boost on and smooths out as soon as pump is switched off. At reasonable OATs, no issues with cylinder temps.

My question is: will adding low boost during the early climb (5-10 minutes) with WOT or even reduced power/RPM add enough /any additional fuel to the cylinders to help mitigate the high cylinder temps? Or is there no or negligible effect?

I have read that adjusting fuel flow to that of the N model engines (31/gal/Hr) is the only method mentioned in other posts. What is the collective opinion? Thanks, Eric

 

[NickG]

There is no fuel boost pump use in takeoff. Make sure you don’t lean too much on the ground as this will increase CHTs quickly. On takeoff it’s WOT, full fuel, full prop. Keep leaning to maintain EGTs at 1250. If you’re still getting hot, flatten out. Don’t touch mixture prop or throttle until ur at cruise altitude. This is the John Deacon method and I use it all the time. I live in Vegas, hot and high DA’s my CHTs rarely go over 380 in climb. You are adding too much fuel in climb with the boost pump on. and as you climb, your mixture will naturally get richer anyhow. If you are still having issues, you may want to have your baffles checked. Oh, and I also use 100W oil during the hotter months - helps keep the oil temps from spiking.

[LANCECASPER]

5 hours ago, EricShr said:

Hi, I'm seeking advise from other Southwest Mooney Ovation owners on how to deal with VERY high cylinder temps on climb out at VERY high OATs (110-115). I have an Ovation 1 that has been converted to 310HP/2700. Fuel flows at takeoff are 27.5Gal/Hr. with GAMI injectors. Runs excellent LOP, idles at 700. At startup runs like crap with boost on and smooths out as soon as pump is switched off. At reasonable OATs, no issues with cylinder temps.

My question is: will adding low boost during the early climb (5-10 minutes) with WOT or even reduced power/RPM add enough /any additional fuel to the cylinders to help mitigate the high cylinder temps? Or is there no or negligible effect?

I have read that adjusting fuel flow to that of the N model engines (31/gal/Hr) is the only method mentioned in other posts. What is the collective opinion? Thanks, Eric

 

If I remember correctly the fuel flows need to be set higher than Continental shows. @StevenL757 will know the answer.

EDIT: I looked back and Brian Kendrick set my to 29.5 GPH when he did the 310ho on an Ovation I used to have.

 

Also are you starting with the Boost Pump on?  Or just using it to prime before the start?

[NickG]

3 hours ago, EricShr said:

Hi, I'm seeking advise from other Southwest Mooney Ovation owners on how to deal with VERY high cylinder temps on climb out at VERY high OATs (110-115). I have an Ovation 1 that has been converted to 310HP/2700. Fuel flows at takeoff are 27.5Gal/Hr. with GAMI injectors. Runs excellent LOP, idles at 700. At startup runs like crap with boost on and smooths out as soon as pump is switched off. At reasonable OATs, no issues with cylinder temps.

My question is: will adding low boost during the early climb (5-10 minutes) with WOT or even reduced power/RPM add enough /any additional fuel to the cylinders to help mitigate the high cylinder temps? Or is there no or negligible effect?

I have read that adjusting fuel flow to that of the N model engines (31/gal/Hr) is the only method mentioned in other posts. What is the collective opinion? Thanks, Eric

 

What's your altitude at take off?

[N201MKTurbo]

4 minutes ago, NickG said:

What's your altitude at take off?

KFFZ 1400 feet.

[NickG]

For my Ovation (310HP):

On a Sea level climb KHHR Hawhorne (34ft), I'm 100% Power and 29 GPH.

Departing KHND Henderson (2,490 ft), I'm generating 94% power and 28.7 GPH .

I have every flight complete with engine data uploaded to Flysto and Garmin so these numbers are pretty accurate.

Your fuel flows look a tad low but not that much.

[EricJ]

I can't address anything regarding how operating that particular engine may help or not, other than keep the cowl flaps open and watch CHTs.

In general, though, cruise-climbs, or just dropping the nose and climbing at higher airspeeds helps a lot on most airplanes.   Make sure your engine baffling is completely up to snuff, with no big leaks and the baffle gaskets sealing effectively against the cowl.   

Once I got the baffles sorted out on my airplane it's pretty easy to manage temps just with the cowl flaps and climb airspeed, but that's for a 4-cyl Lycoming.

[NickG]

23 minutes ago, EricJ said:

I can't address anything regarding how operating that particular engine may help or not, other than keep the cowl flaps open and watch CHTs.

In general, though, cruise-climbs, or just dropping the nose and climbing at higher airspeeds helps a lot on most airplanes.   Make sure your engine baffling is completely up to snuff, with no big leaks and the baffle gaskets sealing effectively against the cowl.   

Once I got the baffles sorted out on my airplane it's pretty easy to manage temps just with the cowl flaps and climb airspeed, but that's for a 4-cyl Lycoming.

There are no cowl flaps on an Ovation

[EricJ]

6 minutes ago, NickG said:

There are no cowl flaps on an Ovaton

I keep forgetting that.   It always seems weird to me.

 

[KLRDMD]

29 minutes ago, NickG said:

There are no cowl flaps on an Ovation

Also no cowl flaps on the Cirri and 310s.

[Shadrach]

4 hours ago, EricShr said:

Hi, I'm seeking advise from other Southwest Mooney Ovation owners on how to deal with VERY high cylinder temps on climb out at VERY high OATs (110-115). I have an Ovation 1 that has been converted to 310HP/2700. Fuel flows at takeoff are 27.5Gal/Hr. with GAMI injectors. Runs excellent LOP, idles at 700. At startup runs like crap with boost on and smooths out as soon as pump is switched off. At reasonable OATs, no issues with cylinder temps.

My question is: will adding low boost during the early climb (5-10 minutes) with WOT or even reduced power/RPM add enough /any additional fuel to the cylinders to help mitigate the high cylinder temps? Or is there no or negligible effect?

I have read that adjusting fuel flow to that of the N model engines (31/gal/Hr) is the only method mentioned in other posts. What is the collective opinion? Thanks, Eric

 

It would be helpful to know your full power/full rich take off EGTs. Ideally you want to be 250° ROP or more. 

[EarthboundMisfit]

Hello Eric,

I see similar OAT's here in my part of the world in summer.  When you say very high CHT's, what numbers are you seeing? Pics or video to share?

I have found that running low boost at WOT and ROP increases FF by only 0.1 GPH or so.  In other words, negligible.  Our engine is 280hp and we're set at 25.5GPH on takeoff.  I like your 27.5GPH better. 

We are typically ISA+20 here, and we rarely have a need for Vx or Vy climbs.  So cruise climbing full rich at 120KIAS (or more) keeps CHT's in a range of 320F-350F or so.  This profile allows climb performance of over 1000fpm at sea level.  Our no. 5 cylinder is hottest. often around 370-380 in climb due to the alternator blocking airflow. 

The natural enrichment of mixture during climb is most noticeable above 3000' AMSL. 

Adjusting FF higher (to N model settings) would be an interesting experiment.  I'd have no fear of testing it to see if it improved the situation, afterall the red knob can reduce the FF if it's too much. 

Hope this is useful. 

Hayden

[GeeBee]

Before you get too wrapped around the axle, make sure your baffling and baffle seals are tip-top. Ever since I installed Gee-Bee Aeroproducts (no relationship to me) my temps have been very manageable even in the GA heat. I run about 24.7 fuel flow on take off and rarely see temps over 380 on climb out. After you tighten your baffling, get your fuel flow in order and your problems should cease. I should also add that multi-viscosity oil tends to run cooler. I've heard a number of explanations but let's just say it just does.

[StevenL757]

On 9/26/2024 at 2:15 PM, LANCECASPER said:

If I remember correctly the fuel flows need to be set higher than Continental shows. @StevenL757 will know the answer.

EDIT: I looked back and Brian Kendrick set my to 29.5 GPH when he did the 310ho on an Ovation I used to have.

Also are you starting with the Boost Pump on?  Or just using it to prime before the start?

Yeah, 29.0 - 29.5 is optimal for that platform, which provides for better cooling...but you didn't hear it officially, as the STC actually says 27.3 - 27.4.

Haven't seen @EricShr's reply yet here about @LANCECASPER's boost pump question, but the boost pump should not be running whilst the engine is being started under normal conditions...hot or cold start.  Also agree with @GeeBee on the baffle seals.  Minimizing their importance proper placement and consistent inspection and repair as necessary will cause more long-term harm than good.

Edited October 5, 2024 by StevenL757
Lined out and replaced with more accurate content

[hais]

On 10/4/2024 at 1:08 PM, StevenL757 said:

but you didn't hear it officially, as the STC actually says 27.3 - 27.4

It does? Ours is set at 24, when I asked, the shop said that's what TCM requires, so we left it at that. 

[LANCECASPER]

7 hours ago, hais said:

It does? Ours is set at 24, when I asked, the shop said that's what TCM requires, so we left it at that. 

Does yours have the 310hp STC?

[Schllc]

A few of mine struggled here as well, what I found to work best is as soon as you are at a safe/ish altitude, either stop the climb or reduce it to about 200fpm and wait to see cht’s trending down. As soon as it start to move down you can resume the climb without the temps being a problem. 
at least that worked for me. 
this is of course after you confirm fuel flows are correct, and baffling is tight. 

[Ed de C.]

My Ovation has the 310hp STC and is setup with 28gph WOT on takeoff.  I have no problem with CHTs here in Michigan (max is 370 degrees with OAT of 30C.)  My baffling is very good.  In fact, I struggle to keep the oil temps high enough in cruise and CHTs routinely run below 300 F (LOP).    

I lean in climb to the white bar on the EGT on the G1000 engine page (1400-1450) per the manual.  I checked my EGTs full rich when departing a sea level airport and found that they settled within the white bar, so, per George Braly/Mike Busch, you can lean to that in climb and be good.  I climb out at 120 kts indicated in summer, 140 kts in winter.  Both give 1,000 fpm from my home field at 1,000 AGL.  

Baffles have to be good with plenty of RTV.  

Oh, one thing the A/P found in the ongoing annual:  The timing is set for 20 degrees Left mag, 19 degrees right mag.  That's a little under the 22 degree spec on the OI-550-G, meaning the retarded timing will tend to have CHTs run a little cooler (and a little less power).  The A/P did not feel it was enough to make adjustment.  Your magneto timing is a factor in CHTs.

Ed

[hais]

18 hours ago, LANCECASPER said:

Does yours have the 310hp STC?

Yes. No issues with CHTs, no problem staying around 380F. But we did suffer an inexplicable detonation. 

[LANCECASPER]

5 hours ago, hais said:

Yes. No issues with CHTs, no problem staying around 380F. But we did suffer an inexplicable detonation. 

That's not inexplicable. Your fuel flow is way too low if you're going to use the STC that allows 2700 rpm

 

 

[NickG]

On 10/7/2024 at 10:05 PM, hais said:

It does? Ours is set at 24, when I asked, the shop said that's what TCM requires, so we left it at that. 

That’s pretty low. As I mentioned earlier, mine around 29 or so - I don’t have any CHT issues. I have the 310 HP STC. 

[StevenL757]

On 10/8/2024 at 12:05 AM, hais said:

It does? Ours is set at 24, when I asked, the shop said that's what TCM requires, so we left it at that. 

You're getting incorrect information.  Mine comes from Bob Minnis - former owner of the 310BHP STC, and from Continental directly...who corroborates Mr. Minnis' data...which I reflected above.

[NickG]

Here is the page from the STC; Fuel flow 160lbs/hr at max power Thats 27.5GPH. Mine is set a little higher than the STC at 29 or so.