JPI 830 settings for a 231

[rainman]

I just had a JPI 830 installed in my 1979 231. I have GAMI injectors and an intercooler. I fly lean of peak in cruise. The manual says to set the default for ROP and then lean to the first cylinder if your engine is turbo charged. Is this how to use it, or should I use the TIT? This forum seems to be the best place for me to go for experienced users. Thanks . Ray

[FBCK]

Rainman I can only say my tit would go beyond 1650, (I know the poh states 1725 as the max for 30 seconds) but I don't want to go there. I just do the big pull of the red knob and then perhaps rich to smooth. I guess use the tit then, I keep it at 1575 or lower if I'm not in a rush.

[rainman]

Thanks, when I had the JPI 700 I used TIT and started in cruise at a "pre-lean" of about 100 degrees rich and then leaned past peak to about 50 degrees lean. With the 830 I may be able to lean to the first cylinder rather than TIT. According to the manual, using the ROP setting will lean to the first cylinder rather than the last cylinder if the LOP setting is used. This assumes I understand it ?? Ray

[jlunseth]

I am a little confused by the question, you say your fly lean of peak in cruise but want to know how to set the 830 up for ROP (rich of peak)?

 

In any event, the GAMI/APS seminar people teach to always use EGTs.  If you are leaning ROP, you lean to the first cylinder to peak.  If you are leaning LOP and leaning across peak from the rich side, you lean to last cylinder to peak.  The reason for using EGT's is that your engine is comprised of six (or 4 if you are a J) separate small engines, each operating a little differently from each other.  If you lean with reference to peak TIT, some of the cylinders may be in the red box or over on the other side of peak from what you intended to lean to.  Example:  Cyl. #1 and Cyl #4 have fuel flows lets say .8 GPH apart, lets say 1 is richer than 4.  If you lean to TIT, your peak may be somewhere in between 1 and 4, and if you lean back to the rich side, you may be leaving 4 exactly at peak while 1 is rich of peak.  That is hard on 4. 

[rainman]

Jlunseth, the manual for the 830 reads to set the default to ROP if you have a turbocharged engine. My question is : am I supposed to set the default for ROP and then run LOP based on the EGT from the first cylinder to peak? I fly a six cylinder 231 with GAMI injectors and an intercooler. It appears the thinking is that if the LOP default is used, by the time you get 50 degrees lean of peak on the last cylinder, you may be too lean on the first cylinder to peak. Does that make sense? Ray

[jlunseth]

I have a 231 also.  It does make sense.  There are a lot of issues with the TSIO-360-GB or LB that make it difficult to run LOP.  For one thing the induction system is about as far from tuned as you can get.  It is basically a straight tube with perpendicular droppers.  This means that the run for induction air trying to get to the last cylinder on the tube is significantly longer than the run for the first cylinder.  Induction tuning technology also has to consider the pressure pulses set up each time a valve closes (a pressure wave is generated back into the induction system).  The turbo is not perfectly regulated so MP tends to move around just a little.  Taken altogether it is a difficult engine to get all of the cylinders running consistently enough that LOP works.  Most of the time the engine starts running rough as soon as you get on the lean side, so you can't lean far enough to operate the engine out of the red box.

 

I have my engine to the point where I am able to experiment with LOP.  I have the 930, so at the start of each flight I can choose whether to lean LOP or ROP.  I know the ROP settings well enough that I can set the engine there without help from the 930, and then choose LOP and lean over to the LOP side.  To do it though, the power and MP begin to fall of once I am on the lean side so I need to put MP back in, and quite a lot of it comparatively speaking.  I need to cruise LOP at 75% HP with about 34.5 - 36", which is the 100% HP setting at sea level.  But when operating LOP, power is determined by fuel flow, not by MP.  I have my fuel flow set at 11.4 - 11.5.  The multiplier for our engines (based on compression ratio) is 13.7, so this is a 75% HP setting when operating LOP. 

 

GAMI/APS says you should operate a turbo at about 60 degrees LOP and that would be the last cylinder to peak.  I have found their settings a little conservative for the TSIO 360, so I try to get the last cylinder to peak into the -20 range, and most of them will then be in the 40-60 range.  Seems to work well, as the fuel flow is at 11.5, right where it should be.

 

Having done a lot of work on my engine (actually the A&P's did the work, I just paid) I can tell you there are a lot of systems on this engine that need to be working exactly right for LOP to work, so be careful with it.

[skeptic]

jlunseth,

 

Do you ever operate your 231 LOP at less than 75% power?  If so, what are the approximate fuel flows at the lower LOP power settings?  Using the 13.7 multiplier I would assume that 65% power would be somewhere in the 10 gph range?

[jlunseth]

The multiplier is the key.  It looks like 10 GPH and whatever MP gives you -20 to -60 if you truly want to be LOP.  But the GAMI/APS people say that you cannot hurt the engine at 65% or below, so you could run it at peak or a little below and it would be fine.  I do run the engine at 65% from time to time, but not with any kind of precise fuel flow and MP setting.  I do not run it at prolonged cruise at the setting, because I would rather get there quicker.  I can generally cruise at a little over 140 indicated (the green ring on the ASI, not TAS) and 11.5 gph, which is really great economy as far as I am concerned.  Even at low altitude that is going to be a TAS of around 150-155 and 5 1/2 hours of fuel with a reserve. Mind boggling.

 

If I am coming in for a landing or doing an approach where I need less airspeed, I take off some MP and generally have to enrich the mixture a little or the engine will start to miss because the fuel flow goes too low.  But I just put in enough mixture to smooth the engine out, not looking for any particular fuel flow setting.

[rainman]

I just got off the phone with John Paul at GAMI. He said it doesn't matter whether I choose the ROP or LOP mode on the 830. The key is understanding the EGT of the cylinders as you lean. He said to expect fuel flows consistent with Jlunseth's numbers. I'm flying from San Antonio to Daytona this week an plan to experiment with the settings at 15K ft. Thanks for the info, I learned a lot . Ray

[jlunseth]

They advocate the "big pull" at GAMI/APS.  Doing the big pull means getting to cruise and pulling the mixture smoothly and fairly quickly over to the lean side, and then adjusting for the fuel flow you want.  This way you spend less time in the "red box" as you lean across.  The trick with a 231 from my experience is that there are two components that need to be adjusted, the mixture and the MP.  If you just pull the mixture across and don't adjust MP, the MP will fall off sharply.  If you let that happen, you can set the mixture to 11.5 but you will be on the ROP side at that fuel flow and probably in the 50% power range.  You need to put MP back in to get to the 35.5 - 36 " range on my aircraft, with the 11.4-11.5 fuel flow, to be LOP.  Exacerbating this, the MP and fuel flow are set up to move in concert, in other words if you set the mixture at, let's say, 11 gph and 28", and then put in MP, the fuel flow is going to go up, probably into the 12 range somewhere. 

 

My point is that it is necessary for the pilot to adjust both until the two settings are right.

[FBCK]

Jlunseth, I like the conversation above but I would be interested in seeing some picture of your panel.  My engine monitor roled over yesterday and died (UMG16 I believe) and I'm thinking about getting a 930. I was hoping to wait for my new GPS and do both, but Avidyne seems to be taking there time on that one.

[jlunseth]

http://mooneyspace.com/gallery/album/13214-jlunseths-album/

 

I hope the link works.  Click on the album in the upper left to open it.  The black panel is the old one, the white panel is the new one.  Those are pics of the panel when I first got it back from the shop.  I have had it for probably three years now.  The best things we did, were to put the 930 on the pilot side panel, in the instrument scan, and put the AP annunciator at the top of the pilot side.  That way, if anything goes wrong with the engine, or if the AP acts up, I see it immediately rather than when the problem has matured to critical.  The sole exception is the vacuum indicator, which is still over on the far right, factory location.  The vacuum must be dead as a doornail before I figure it out.

[FBCK]

Looks good, I like the after shots, white work well, I might send the shots to my A&P before he spend 10 grand just trying to get the other thing fixed. How do you find people in the Gallery, I cant seem to figure it out.

[rainman]

Turns out my GAMI injectors aren't balanced well enough for LOP. I have about 80 degrees spread. I called GAMI but John Paul is at Sun and Fun until next week so I'll follow up then. Because of weather and winds I flew at 10K , MAP 28, FF 9.5 GPH. Ray

[carusoam]

I would surmise that an engineering company could balance the air flow to each cylinder in The way that Continental has done for the Acclaim(and others). Balancing fuel flow is 1/2 the challenge. Air flow is somewhat equally important for smooth LOP. Look for long curves and equal length runners to manage the pressure waves in the intake. Something akin to church organ pipes... Only with the six pipes playing the same note.

The TN-IO550(g) has a very nice intake system. Balanced for both fuel and air and turbo normalized.

So if you can't run LOP after moving the injectors around, and adjusting their individual fuel flow, take a look at the similarity of the individual intake tubes???

It would be nice to take a Continental system from the IO550 and scale it properly (if needed) for the 231.

Bravo owners would be interested in the solution as well... But with a Lycoming, they probably can't get help from the Continental guys...

Ask the GAMI guys about balancing the air flow and how they would do it? They are an engineering company with direct knowledge of the situation.

Best regards,

-a-

[jlunseth]

There is not much you can do about tuning the induction system on a 231 I am afraid. For one thing, it would require at least a 337 I am sure, but probably more than that. The issue is the basic design, it is just a long delivery tube with droppers from that tube at each cylinder, coming perpendicularly off the delivery tube. The distance to each cylinder is therefore inherently different. You would have to come up with a completely new (and STC'd) induction manifold. Also, delivery tube comes to a straight, capped, dead end, which is a good way to generate pressure pulses. It does seem to work ok though, if you get the GAMI's balanced properly and everything else in the engine is in good condition (talking about the TSIO 360).

I am curious about this though: "Turns out my GAMI injectors aren't balanced well enough for LOP. I have about 80 degrees spread. I called GAMI but John Paul is at Sun and Fun until next week so I'll follow up then. Because of weather and winds I flew at 10K , MAP 28, FF 9.5 GPH." 80 degrees spread between what and what? If you mean the EGT's from one cylinder to another, that is an irrelevant number. Probe placement alone can do that. If you have not done it already, go to the GAMI page and do the lean test, or download your data and lean test it in the JPI software. The number that is used to assess the balance between the GAMI's is fuel flow, whether the cylinders peak at or under .5 GPH apart.

Let me try to clarify what I am saying here. Your JPI displays two numbers, one is DIF and that is the absolute temperature difference between the highest and lowest EGT. One might be 1350 and one might be 1430, and you would have a DIF of 80 degrees. That number is irrelevant and I don't know why JPI bothers with it, because probe placement creates it. The other number is the difference when on the LOP side between the degrees of LOP of the leanest cylinder, and the degrees of LOP of the richest. If the leanest is -100 dLOP and the richest is -20, that is going to be too much, the leanest cylinder and probably a couple of others are going to be starving for fuel and the engine runs rough. If GAMI can get that number down to 20 degrees or less, let me know please I would love to be seeing that. Mine are a little more than 40 degrees apart.

[carusoam]

Clearly it would be a significant piece of hardware. The newer IO550s get it (g and n). TN'd and NA.

It has impressive results. With very little GAMI spread. The Acclaim can be run LOP with it. The Bravo doesn't have it.

Tuned intake + balanced injectors = happy campers... For both Chevy and Continental at least.

Since Continental has it for the IO550, could they deliver it for the slightly smaller engines? And fit it under the cowl as well?

Improving flow would also increase output...

Best regards,

-a-