Lean of Peak, Rocket manual says NO, is it OK for TSIO-520?

[fixnflyr]

I just bought a rocket and the Rocket conversion does not recommend LOP in their manual supplement. I have GAMI injectors and a GEM 610. I would like to be able to run LOP if safe because fuel flows of 20-22 gal. per hour are not fun. I don't mind slowing down 15-20 knots for 4 of 5 GPH, I would love that trade off. That speed loss would not make much time difference on a 2.5 hour trip anyway.

 What have some other Rocket owners with the TSIO-520-NB engine getting for fuel flow and speeds, temps. etc.?

Please keep these responses to the TSIO-520-NB engine and not the other models of engines.

Thanks to all,

Swaid

[mcpilot]

LOP theory is based on chemistry; more exactly stoichiometry.  It should work    in any type of piston engine.  After reading Mike Busch's material, I actually lean to CHT, and not EGT...  As long as the CHT's are below 360 F you are good...  

 

You can do the same thing with your Rocket...  Take it up to altitude and lean until you have a fuel flow that is at peak or leaner and then you can lean further until your CHT's are happy and engine still runs smooth... Then close the cowl flaps and cruise...

[David Mazer]

Congratulations on your purchase of possibly the finest Mooney (albeit converted) ever built IMHO.

 

I presume you have a 231 conversion with the Gami injectors.  One must remember the manual was written a long time ago and there was much less data available about LOP at that time.  I believe Continental still recommends ROP operation also despite all the available information.  There are plenty of guys with Rockets on this forum that run LOP as SOP and it is probably fine as long as your total EGT spread is sufficiently small with the balanced injectors.

 

My spread is too large to make LOP comfortable to me and I have not spent the effort to tune my injectors so I just power back a little in ROP.  I usually fly at 30" and 2300 RPM and about 18.3-8 GPH for a TIT of 1480 but my TIT is running lower than actual by about 70 degrees (I've had it checked and there is nothing wrong with the probe it just is off) so my actual TIT is closer to 1550.  There is an SB out on the engine not to run below 2300 RPM at cruise.  I also will dial back to 29" when I'm in no hurry and that takes the fuel flow down to the low 17s.  When I'm just flying, with no particular destination, I fly at 25" and 2300 and that brings the fuel flow down to mid 14s.

 

Enjoy your new bird!

[DS1980]

The manual says no and the experts say yes. A good thing to keep in mind is that engine manufactures know how to produce a good engine from a mechanical standpoint. They never really learned how to run them. A good example of this is Lycoming, who states to run their engines at 50 degrees ROP. They could try to be more incorrect, but they would not succeed.

 

Oh, and congrats on a wise purchase. Well, not wise from a money point of view........you know what I mean.

[mcpilot]

The manual says no and the experts say yes. A good thing to keep in mind is that engine manufactures know how to produce a good engine from a mechanical standpoint. They never really learned how to run them. A good example of this is Lycoming, who states to run their engines at 50 degrees ROP. They could try to be more incorrect, but they would not succeed.

 

Oh, and congrats on a wise purchase. Well, not wise from a money point of view........you know what I mean.

Couldn't agree more!!

[Shadrach]

LOP theory is based on chemistry; more exactly stoichiometry.  It should work    in any type of piston engine.  After reading Mike Busch's material, I actually lean to CHT, and not EGT...  As long as the CHT's are below 360 F you are good...  

 

You can do the same thing with your Rocket...  Take it up to altitude and lean until you have a fuel flow that is at peak or leaner and then you can lean further until your CHT's are happy and engine still runs smooth... Then close the cowl flaps and cruise...

Yes and no... If the DA is high and OAT is 90df then a CHT of 360df is acceptable. If the OAT is 5df, a CHT of 360df is not so good. The same ICP will generate vastly different CHTs depending on air temp and volume available for cooling. CHTs of 360df does not necessarily translate to a kind mixture setting...

[N201MKTurbo]

It is your airplane, you can operate the engine anyway you please. If you fry the engine you have to pay to get it fixed.

 

BTW I have run my engine LOP for years with no problem. The only difference is if you disassemble the engine it has brown sludge instead of black sludge.

[aviatoreb]

Congratulations on your purchase of possibly the finest Mooney (albeit converted) ever built IMHO.

 

I presume you have a 231 conversion with the Gami injectors.  One must remember the manual was written a long time ago and there was much less data available about LOP at that time.  I believe Continental still recommends ROP operation also despite all the available information.  There are plenty of guys with Rockets on this forum that run LOP as SOP and it is probably fine as long as your total EGT spread is sufficiently small with the balanced injectors.

 

My spread is too large to make LOP comfortable to me and I have not spent the effort to tune my injectors so I just power back a little in ROP.  I usually fly at 30" and 2300 RPM and about 18.3-8 GPH for a TIT of 1480 but my TIT is running lower than actual by about 70 degrees (I've had it checked and there is nothing wrong with the probe it just is off) so my actual TIT is closer to 1550.  There is an SB out on the engine not to run below 2300 RPM at cruise.  I also will dial back to 29" when I'm in no hurry and that takes the fuel flow down to the low 17s.  When I'm just flying, with no particular destination, I fly at 25" and 2300 and that brings the fuel flow down to mid 14s.

 

Enjoy your new bird!

 

My ROP numbers generally agree with yours as far as fuel flow.  And as you know, but for the others, I agree completely with following that AD that came out recently regarding running the continental big bores at no less than 2300 in cruise, despite the original rocket POH that has 2200 settings on it.

 

David, I am curious, what did testing your TIT setting to cross check with your TIT readings involve?  I have often wondered if my JPI EGT and TIT readings reflected reality in any way.

[aviatoreb]

I just bought a rocket and the Rocket conversion does not recommend LOP in their manual supplement. I have GAMI injectors and a GEM 610. I would like to be able to run LOP if safe because fuel flows of 20-22 gal. per hour are not fun. I don't mind slowing down 15-20 knots for 4 of 5 GPH, I would love that trade off. That speed loss would not make much time difference on a 2.5 hour trip anyway.

 What have some other Rocket owners with the TSIO-520-NB engine getting for fuel flow and speeds, temps. etc.?

Please keep these responses to the TSIO-520-NB engine and not the other models of engines.

Thanks to all,

Swaid

 

My TSIO520NB runs smoothly at all settings.  I achieved a "gami-spread" of 0.3gph simply by swapping the injectors around, but without needing to buy Gami's.  Actually the good folks at Gami received my gami-readings and told me I might not need to buy gami's and told me which ones to swap to lower my spread - and by golly they were right.  How is that for customer service turning away business??!!!  I will definitly buy product from them in the future.

 

But despite smooth running engine at all settings, even very deep LOP I am not comfortable running LOP at high power settings at higher altitude because TIT becomes my limiting parameter.  IF I try higher power settings my TIT starts become 1600...1610...1620, and even though I have read in some litt that this is not a problem I am not happy with that.

 

I have run low power settings LOP when trying to extend range.  One setting I like is 13gph (just below 60%) gives me 175TAS at 15k with TIT ~1550-1560 and ~40-50 lean of peak EGT (again I need to lean more lean of peak EGT than you might think necessary since I hate to see 1600 TIT which I would get closer to peak EGT on the lean side).  That is a lot slower than the ROP speeds we can get at 15k, but the mpg is relevant when extending range.  I have rarely used this setting since I like to go fast and I rarely have need to go more than 2.5hrs.

 

There is a good deal written by the good Cessna twin folks who fly the C340 using the very same TSIO520NB - albeit with different install/baffling, etc.  They seem to indeed run some very high TIT's including up to 1650 which is right at redline.  If I were willing to run 1650TIT then I think it would be possibel to run 85% cruise setting at 19gph, which would give faster cruise settings than anything you see written in our POH.

[David Mazer]

David, I am curious, what did testing your TIT setting to cross check with your TIT readings involve?  I have often wondered if my JPI EGT and TIT readings reflected reality in any way.

One year at Sun N Fun I spoke with Dar Conrad about the TIT testing.  The procedure is simple, and in the Rocket POH, lean to peak TIT.  It should peak at 1650.  Don't spend a lot of time there.  Just lean it out to just past peak (it will run a little rough), note the temp, and then rich it out again.  The peak you get less or more than 1650 is the error.  In my case it was only 1580.  I was very surprised since I was typically running a TIT of 1510 (1580) without knowing it.  Dar recommended not going over 1550 so I now lean to 1480

[aviatoreb]

One year at Sun N Fun I spoke with Dar Conrad about the TIT testing.  The procedure is simple, and in the Rocket POH, lean to peak TIT.  It should peak at 1650.  Don't spend a lot of time there.  Just lean it out to just past peak (it will run a little rough), note the temp, and then rich it out again.  The peak you get less or more than 1650 is the error.  In my case it was only 1580.  I was very surprised since I was typically running a TIT of 1510 (1580) without knowing it.  Dar recommended not going over 1550 so I now lean to 1480

 

Huh - but at what engine setting rpm and mp?  Surely the true peak tit varies with rpm and mp?  Also, what if there are tiny leaks in your baffling?  Then I would expect a higher true Tit peak, yes?  In my own case, when I first got my airplane, as part of tuning it up to run uber-smooth- I soon found that there were many pin sized holes in the baffling which were cured by replacing some of the baffling.  And as a consequence the TIT ran cooler at various settings, and likewise it was part of getting my engine to run smoothly LOP - but which as I said I do not really do much for reasons of stil the tit would be hotter than I would like.

[David Mazer]

Dar said about 8,000 ft and typical cruise settings.  Sorry.  I should have mentioned that.  I'm not sure about the effect of baffeling or other factors on the TIT reading but the variance from peak shouldn't change regardless.

[rocketman]

There is a TIT check in the Rocket "POH" that commands you to fly between 8,000 to 12,000 MSL, full rich, RPM at 2400 and 35 MAP. GPH should be around 24 and then lean to max TIT. It should be at 1700. If it above 1700, then your TIT probe-guage is reading high by that many degrees. So adjust accordingly downward. If your TIT temp is below that 1700 mark at peak, than adjust upward accordingly. The problem occurs during the latter when your TIT probe indicates a lower temp than actual since you will be flying higher than you think. 

 

I am a stickler on temperatures and always error on the safer (cooler) sides, right or wrong. 

 

I note that there is not a similar TIT check on the TLS/Bravo. Wonder why?

[David Mazer]

Dar said the power settings aren't that relevant and one could use lower settings.  Glad you checked, I thought it was 1650.  Also, Ron, I spoke with JPI about the likelihood of the probe failing if the temp is off and they told me that is unlikely unless I see the temperatures starting to vary at the same settings and they suggested I check EGT, CHT, and TIT temp before starting the engine to confirm they are all reading ambient.

[aviatoreb]

Thanks guys - I will look into this calibration right away.  I can't believe I missed that in the POH.

 

35'' 2400 sounds like a pretty high pressure setting to be searching for peak TIT.  I hope it allows for a bit lower setting as David suggests.

[rocketman]

Good point. I didn't have the POH with me when I posted it but I fell certain it was a high setting. Check it out, if you need a copy PM me and I'll email you the page.

 

The POH says to check it every time you fly.

[David Mazer]

The POH does say to do it every flight.  I don't.  I've only done it a couple times.  Also, I mentioned my concern about the high TITs and Dar minimized it saying it can run 1700 for over a min.  Just don't sit there looking at it.  Lean it to just past peak rather quickly and then rich again.