My GAMI fiasco

[azure]

I've posted before that I bought GAMIjectors for my IO-360 this summer and have been working on getting them tweaked so that I can run LOP. I'm now on my third (and presumably last possible) tweak. Still no joy. In fact. by the numbers I'm worse off now than with tweak #2. At least then I had the spread down to pretty close to 0.5 gph. As of yesterday it's 0.8 gph. Unlike before though, I find that I can (just barely) get all cylinders LOP without roughness. The problem is that the fuel flow range where that's possible is razor thin. Just a hair leaner and the knots start to drop off like a stone (the "sweet spot" still costs me at least 10 kts), and the roughness comes in right behind. A hair richer and #2 is right at or slightly rich of peak. Even so I wouldn't dare run WOT like this except above 8000 MSL.

GAMI's John Paul has already said that the injector diameter difference he has me at now is VERY unusual for an IO-360 and he is suggesting that something else might be going on.

But what?? My mechanic and I are both scratching our heads and coming up with zilch. He has already checked several times for induction leaks, recently replaced a spark plug, and has checked condition and timing on the mags more than once. Now to be fair, my mechanic is NOT an LOP advocate, and says that what I'm finding is pretty much what he expected, and why he doesn't recommend the practice. So I wouldn't expect him to devote a lot of brain cells to trying to troubleshoot something he considers basically normal.

I'm about at the point of giving up and just treating the whole fiasco as an expensive mistake. (Maybe not so expensive, on the AMU scale.) Before I reach that point, I'm hoping someone here might be able to suggest something else to try or investigate.

 

[txflyer]

Thank God I'm still in the stone age with a carburetor.

Lean to peak minus 75 and fly all day.

Engine starts immediately on the hottest or coldest days ... sorry to hear your pain broseph...

 

[wabower]

I'm aware of a couple of TSIO-520-equipped planes in which the stock factory injectors were as good as it got, but the patterns were normal. I'd keep looking, but find somebody else to do it. Fortunately, this problem and diagnosis are highly portable.

FWIW, I'd quit flying if I had to put up with your mechanic situation. Nobody needs that much aggravation when trying to enjoy a past-time.

 

[bbchien]

My Continental "flow matched" injectors for both engines let me get 125 LOP smoothly. I had a set from George but these are as good as it gets, and they went back with the Continental parts.

(I also had to do something "unspecified" to my aneroids to get this to work....)

 

[Marauder]

I've posted before that I bought GAMIjectors for my IO-360 this summer and have been working on getting them tweaked so that I can run LOP. I'm now on my third (and presumably last possible) tweak. Still no joy. In fact. by the numbers I'm worse off now than with tweak #2. At least then I had the spread down to pretty close to 0.5 gph. As of yesterday it's 0.8 gph. Unlike before though, I find that I can (just barely) get all cylinders LOP without roughness. The problem is that the fuel flow range where that's possible is razor thin. Just a hair leaner and the knots start to drop off like a stone (the "sweet spot" still costs me at least 10 kts), and the roughness comes in right behind. A hair richer and #2 is right at or slightly rich of peak. Even so I wouldn't dare run WOT like this except above 8000 MSL.

GAMI's John Paul has already said that the injector diameter difference he has me at now is VERY unusual for an IO-360 and he is suggesting that something else might be going on.

But what?? My mechanic and I are both scratching our heads and coming up with zilch. He has already checked several times for induction leaks, recently replaced a spark plug, and has checked condition and timing on the mags more than once. Now to be fair, my mechanic is NOT an LOP advocate, and says that what I'm finding is pretty much what he expected, and why he doesn't recommend the practice. So I wouldn't expect him to devote a lot of brain cells to trying to troubleshoot something he considers basically normal.

I'm about at the point of giving up and just treating the whole fiasco as an expensive mistake. (Maybe not so expensive, on the AMU scale.) Before I reach that point, I'm hoping someone here might be able to suggest something else to try or investigate.

Have you looked at your fuel flows to see if they are constant? If it is not staying within a couple of tenths GPH, you may be dealing with a fuel servo problem. This would explain the roughness.

 

[airguy]

How 'bout you take the airplane to GAMI and let them deal with it? They will be happy to do it...

I fly an IO360 with GAMIjectors and I absolutely love them, and I'll put them in my RV9A sometime during Phase I as well. The difference they make is real, I'm seeing a spread of 0.2 gph now on the IO360 in the 172, and I can pull power back all the way down to ~2100 rpm smooth and WOT using the mixture alone before the fire goes out in #3.

The one spot I have an issue with them (and it's not so much GAMI as LOP in general) is pulling the mixture way back on descent. As the airspeed keeps the prop RPM up if you go to lean it will start popping in the exhaust as the ignition fails to light off the too-lean charge. Then it's time to richen up a bit and pull the throttle back. In the 172 I usually don't see this happen until I hit about 1200fpm descent rate, in west Texas we tend to do space-shuttle descent rates from cruise when possible in the summer due to high ground temps.

 

[azure]

Have you looked at your fuel flows to see if they are constant? If it is not staying within a couple of tenths GPH, you may be dealing with a fuel servo problem. This would explain the roughness.

The roughness is because in order to get my richest cylinders LOP, I have to take my leanest pair so lean that they aren't making power.

The mystery isn't the roughness, it's why all of GAMI's flow matching fails to get my leanest pair anywhere close to as rich as my richest pair. They've made #1 and #2 as lean as they possibly can, they're both A's IIRC. For #3 and #4 they gave me their widest diameter injectors, and then for tweak 3 they specially drilled them out to make them even wider. No joy.

I'm not sure what you mean by fuel flowS in the plural. I only have an analog Cessna fuel gauge which is actually a pressure gauge calibrated to read in gph. I don't have a real fuel flow gauge and I don't know if there's any way to measure the fuel flows to each cylinder, if that's what you meant.

 

[azure]

How 'bout you take the airplane to GAMI and let them deal with it? They will be happy to do it...

I'm sure they would. But Ada OK is a bit of a long haul for me. I'm up in Michigan.

It might come to that, though...

 

[Tom-D]

What gauge are you using to get these numbers?

has it been tested for accuracy ?

 

[txflyer]

I'm really stupid about all this, but do the runners on the intake all have to be the same length and c.f.m. flow?

If you have two cylinders that are not doing right, but all the others are, that sounds like an intake problem if you have ruled out all other problems like compression, spark, fuel, etc....

 

[Tom-D]

I'm really stupid about all this, but do the runners on the intake all have to be the same length and c.f.m. flow?

If you have two cylinders that are not doing right, but all the others are, that sounds like an intake problem if you have ruled out all other problems like compression, spark, fuel, etc....

It sounds to me like there a few probes in the wrong place, giving the wrong indications. each probe must be an equal distance from the exhaust valve to be comparable to the others.

 

[docmirror]

Disclaimer, I don't own an IO-xxx engine. I used own one, but that was pre-GAMI.

Here's how I would proceed. On YOUR plane, with YOUR injector harness and YOUR fuel pump; Remove all the injectors and fit them back in the fuel delivery runners. Fit each injector into it's own plastic pickle jar. Run the elec fuel pump at four discrete settings, full rich, 3/4 rich, 1/2 rich and 1/4 rich. Compare the fuel delivered into the pickle jars at each setting. If you are getting what GAMI thinks you're getting two of the jars should be much fuller than the other two.

Based on the results you will have either four very close delivery rates, or two high and two low rates. If you have(as I suspect) two very high rates, and two very low rates, then you will take apart the induction air delivery system completely and find out why the air delivery is so wildly different. I'm thinking you have a serious air leak that hasn't been discovered. It's strange that it affects two jugs and not just one.

If you have four delivery rates that are close, then investigate why the fuel delivery system is having different pressures at the injectors.

 

[azure]

What gauge are you using to get these numbers?

has it been tested for accuracy ?

Which numbers? The fuel flow gauge is stock Cessna (replaced with a rebuilt 2 years ago when the MP side died). The EGTs are from a JPI EDM-700. AFAIK neither has been tested for accuracy. That might be worth a try, but actually that makes me wonder about something else. If the EGT probes weren't properly placed, would that affect the point at which the reading peaks? Or just the indicated temperature?

 

[jesse]

Which numbers? The fuel flow gauge is stock Cessna (replaced with a rebuilt 2 years ago when the MP side died). The EGTs are from a JPI EDM-700. AFAIK neither has been tested for accuracy. That might be worth a try, but actually that makes me wonder about something else. If the EGT probes weren't properly placed, would that affect the point at which the reading peaks? Or just the indicated temperature?

I would sure think it wouldn't change your ability to detect the peak. The actual values are really quite relative and worthless.

 

[John-Paul Townsend]

I'm not sure if I mentioned to you performing what's sometimes called the "Bottle Test." It's similar to the procedure described by the poster above, but instead you perform it WITHOUT the injectors installed. Use only the lines.

Here is the reason: The GAMI system (and any fuel injection system) assumes the flow going TO the nozzle FROM the line is the same for each cylinder. If it is, then we can take a specially tuned set of injectors which will deliver a little more fuel to your leanest cylinders and a little less fuel to your rich ones, so they all reach peak EGT right about the same time. However, let's say you have one or two cylinders that are getting a LOT more fuel to the nozzle than the others. They will run very rich, even if we make the nozzle orifice smaller than the others. We need to be sure they are all the same prior to the nozzles. Here are some brief instructions: http://www.gami.com/gamijectors/bottletest.php

If it turns out the nozzles are each getting the same fuel flow, then we have to worry that you are getting a very large difference in the amount of AIR getting to each cylinder. On a Lycoming engine that shares an intake cam lobe on opposing cylinders, sometimes some wear of that cam lobe will make those two cylinders very rich.

I found an IO-540 back in the Apr-May timeframe where I made 3-4 adjustments and the spread wasn't getting any better and the engine was progressively running worse. We had gone through the bottle test, induction leak test, etc, with no luck, and the only remaining thing was to check the valve train. It was only a 160 hour engine, so we were convinced it was a long short. Unfortunately, it turned out the cam was indeed the problem. I hope that isn't the case with you, but once we've exhausted all other possibilities, you have to check.

I would like to take a look at your flight data from yesterday, especially now that the spread seems to have gone from 0.5 gph (which is marginally acceptable) to 0.8 gph. It's odd to have an inconsistency like that. Maybe with your recent data, I can compare it to the old and see some trend.

Thanks,

John-Paul Townsend
General Aviation Modifications, Inc.
888-359-4264

 

[Henning]

Which numbers? The fuel flow gauge is stock Cessna (replaced with a rebuilt 2 years ago when the MP side died). The EGTs are from a JPI EDM-700. AFAIK neither has been tested for accuracy. That might be worth a try, but actually that makes me wonder about something else. If the EGT probes weren't properly placed, would that affect the point at which the reading peaks? Or just the indicated temperature?

Have you considered checking the JPI unit and probes for calibration? Are they all equidistant from the exhaust valve?

 

[Skylane81E]

Does your engine have the intake runners that are swedged into the inside of the oil sump? I've seen them come loose and cause inconsistent running when leaned

 

[azure]

Have you considered checking the JPI unit and probes for calibration? Are they all equidistant from the exhaust valve?

Yes I've considered it and am considering it, that was the point of my question... so are you saying that calibration or placement would change relative readings, i.e. the mixture setting at which the EGT reading peaks?

 

[azure]

Does your engine have the intake runners that are swedged into the inside of the oil sump? I've seen them come loose and cause inconsistent running when leaned

Not sure about that. What do you mean by inconsistent running? The results I'm getting are very consistent. They just don't seem to be affected by injector bore size.

 

[azure]

Disclaimer, I don't own an IO-xxx engine. I used own one, but that was pre-GAMI.

Here's how I would proceed. On YOUR plane, with YOUR injector harness and YOUR fuel pump; Remove all the injectors and fit them back in the fuel delivery runners. Fit each injector into it's own plastic pickle jar. Run the elec fuel pump at four discrete settings, full rich, 3/4 rich, 1/2 rich and 1/4 rich. Compare the fuel delivered into the pickle jars at each setting. If you are getting what GAMI thinks you're getting two of the jars should be much fuller than the other two.

Based on the results you will have either four very close delivery rates, or two high and two low rates. If you have(as I suspect) two very high rates, and two very low rates, then you will take apart the induction air delivery system completely and find out why the air delivery is so wildly different. I'm thinking you have a serious air leak that hasn't been discovered. It's strange that it affects two jugs and not just one.

If you have four delivery rates that are close, then investigate why the fuel delivery system is having different pressures at the injectors.

Sounds like the best strategy I've heard, thanks. I will run the idea by my mechanic.

 

[Marauder]

The roughness is because in order to get my richest cylinders LOP, I have to take my leanest pair so lean that they aren't making power.

The mystery isn't the roughness, it's why all of GAMI's flow matching fails to get my leanest pair anywhere close to as rich as my richest pair. They've made #1 and #2 as lean as they possibly can, they're both A's IIRC. For #3 and #4 they gave me their widest diameter injectors, and then for tweak 3 they specially drilled them out to make them even wider. No joy.

I'm not sure what you mean by fuel flowS in the plural. I only have an analog Cessna fuel gauge which is actually a pressure gauge calibrated to read in gph. I don't have a real fuel flow gauge and I don't know if there's any way to measure the fuel flows to each cylinder, if that's what you meant.

Exactly. This still can be a fuel flow issue in the servo or flow divider. Think of it this way; you are measuring 10 GPH on the Cessna gauge. In an ideal world each cylinder is getting 2.5 GPH. In reality, there are some differences and what GAMi does is trying to match up injector nozzles to achieve this. In theory, if the flows match up and combustion is happening the way it is supposed to, then running LOP should be doable. In order to check the flows, most mechanics would do the bottle check. They would put each injector head in a bottle and run the boost pump for a set time to calculate the GPH that particular injector was producing.

If your fuel flows for any injector change in flight, then the flow match you are looking for to run LOP won't be there. The cause for this could be a problem with the fuel delivery system (fuel divider, etc) and may only be noticed at altitude or when changing the mixture.

 

[Marauder]

Exactly. This still can be a fuel flow issue in the servo or flow divider. Think of it this way; you are measuring 10 GPH on the Cessna gauge. In an ideal world each cylinder is getting 2.5 GPH. In reality, there are some differences and what GAMi does is trying to match up injector nozzles to achieve this. In theory, if the flows match up and combustion is happening the way it is supposed to, then running LOP should be doable. In order to check the flows, most mechanics would do the bottle check. They would put each injector head in a bottle and run the boost pump for a set time to calculate the GPH that particular injector was producing.

If your fuel flows for any injector change in flight, then the flow match you are looking for to run LOP won't be there. The cause for this could be a problem with the fuel delivery system (fuel divider, etc) and may only be noticed at altitude or when changing the mixture.

Sorry -- I see docmirror mentioned the bottle check. If you do see a problem on the bottle test, your fuel servo and/or divider could need to be overhauled. Sometimes you can see this problem in flight when your overall fuel flow is wandering a few tenths of gallons per hour on the display. It just won't stay at 10 GPH (my example of fuel flow) but fluctuate up and down around 10. Hope this helps.

 

[flyingron]

Have you considered checking the JPI unit and probes for calibration? Are they all equidistant from the exhaust valve?

The probe absolute value is largely meaningless. The EGT varies even if the probe is dead-on balls accurate (that's an industry term) just by small differences in the placement in the exhaust. What the JPI does for it's leaning modes is to find where each cylinder peaks. It's when the peak occurs rather than it's absolute value.

Similar to DocC's my IO-550 came from Continental with a pretty nicely matched set of injecters. The first and last cylinder to peak is less than a quarter turn of the mixture knob while leaning.

 

[Henning]

Yes I've considered it and am considering it, that was the point of my question... so are you saying that calibration or placement would change relative readings, i.e. the mixture setting at which the EGT reading peaks?

Sure, placement is vital. Heat is energy, all energy falls off at the square of distance. It wouldn't really change the timing of when cylinders peak, but it will effect the spread of temp. You likely have an induction leak if there is a difference in time between peaks. As Skylane pointed out, you have induction runners that go through your oil sump on that engine that are not perfectly secured to assure a lifetime seal. Since your engine is naturally aspirated, you could be sucking air from the crankcase there. Here's a quick experiment that can tell us if you have an induction leak. Fly along with high RPM an low manifold pressure (doesn't matter what speed), say 16" and go through a leaning process and gauge the difference between the first cylinder hitting peak and the last cylinder hitting peak in % of fuel flow as well as the total spread in temp. Now set the prop to lowest RPM and wide open throttle and do the same comparison. If you see a greater range in the first test than the second, you most likely have an induction leak. At that point, on the ground with the cowling off and engine running at 1200-1500 rpm, take a can of starting fluid and spray it along the length of all the exposed intake runners. If there is a leak, you will hear the difference in the engine sound when you spray it. If not, you may need to pull the sump and check your tubes by pressurizing them up and spraying a soap/water mix on the joints and looking for bubbles.

 

[Ted]

I'm with Wayne, I'd get a new mechanic first.

 

[Ted]

Oh, and I'd say that's pretty good service that JP has come into the discussion here to try to help!

 

[John-Paul Townsend]

There have been a couple of posts mentioning the calibration of the probes. That calibration WON'T affect WHEN the cylinders reach peak EGT. That is all that is important for the injector tuning, not the absolute value.

So the calibration isn't important. However, verifying that all the probes are going tot eh correct cylinder IS important. If you have the #2 probe hooked up to the #4 cylinder, for example, We would try to correct the F/A ratio imbalance by adjusting the #2 injector, when really it was the #4 cylinder that was not peaking correctly.

Please call me. 888-359-4264.


Thanks,

John-Paul Townsend
GAMI

 

[tmyers]

Liz,
Is your Mechanic a GAMI Rep? If not I know one that is set up to work with JP and the GAMI folks and I am sure JP can get you in touch with a local one if needed. Seems to be a bit of a disconnect with your mechanic on the issues.

 

[azure]

Tim, no he has no connection with GAMI -- which I would have thought obvious since he doesn't even recommend LOP. If he can't find the problem then I'll definitely be looking for someone with more experience troubleshooting fuel injection systems, so I might be PMing you down the line since you're fairly close by.

But for now, John Paul has suggested a strategy that makes a lot of sense and I've made contact (finally) with my mechanic and discussed the details with him, and he agrees that it's a good game plan. The trouble with my mechanic isn't that he's a bad mechanic -- he's actually quite good at most things, and that's not just my opinion but the opinion of everyone who knows him well. He may not be the best choice for a particular job, but that's true of just about every mechanic. At this point he seems to be convinced that this is something that needs looking into, and if there is something to be found along the lines of JP's suggestions, I'm sure he'll find it.

 

[Ted]

If your mechanic is anti-LOP, expect problems trying to get LOP working on your engine. He's not familiar with what is needed, and he really doesn't care since he thinks it's a bad idea.

Seriously. I had some clients with a Bonanza that ran LOP great. Then it went through an annual with anti-LOP mechanics, and wouldn't do it after that.

 

[azure]

Ted, that sounds like voodoo. Can you explain?

(FWIW he isn't anti-LOP, as in someone who thinks you'll burn up your cylinders. All he said is that he thought it was normal to only be able to safely run LOP without roughness in a very narrow fuel flow range. It's just not something he has a lot of experience with.)

 

[Ted]

Ted, that sounds like voodoo. Can you explain?

(FWIW he isn't anti-LOP, as in someone who thinks you'll burn up your cylinders. All he said is that he thought it was normal to only be able to safely run LOP without roughness in a very narrow fuel flow range. It's just not something he has a lot of experience with.)

It wasn't voodoo, my guess is that they screwed up the GAMIjector order. Maybe not on purpose, but maybe on purpose, so as to discourage the owners from flying LOP. Of course, there are a lot of reasons why that would've been a bad idea. But anyway, it was done, the mechanics refused to look at it further, and the owners wouldn't push it. Since I wasn't the owner of the shop nor the airplane, not much else I could do.

 

[azure]

It wasn't voodoo, my guess is that they screwed up the GAMIjector order. Maybe not on purpose, but maybe on purpose, so as to discourage the owners from flying LOP. Of course, there are a lot of reasons why that would've been a bad idea. But anyway, it was done, the mechanics refused to look at it further, and the owners wouldn't push it. Since I wasn't the owner of the shop nor the airplane, not much else I could do.

GAMI gives you identifying tags for each injector specifically to make sure that no one accidentally mixes them up. If the mechanic who installed the injectors put the tags on then there should be no friggin' way they screwed up the injector order by mistake, unless they're seriously incompetent.

There is NO way my guy would pull something like that.

 

[Dav8or]

There have been a couple of posts mentioning the calibration of the probes. That calibration WON'T affect WHEN the cylinders reach peak EGT. That is all that is important for the injector tuning, not the absolute value.

So the calibration isn't important. However, verifying that all the probes are going tot eh correct cylinder IS important. If you have the #2 probe hooked up to the #4 cylinder, for example, We would try to correct the F/A ratio imbalance by adjusting the #2 injector, when really it was the #4 cylinder that was not peaking correctly.

Please call me. 888-359-4264.


Thanks,

John-Paul Townsend
GAMI

A little off topic, but have you guys considered franchising GAMI service centers? I know I would love to take my plane to somewhere closer than Ada to drop my plane off and pick it up running LOP smoothly. I can't be the only one. As is evident by this thread, getting your plane dialed in on your own can be a PITA! As it is now, a lot of diagnostic work and testing is put upon the owner and some people really don't have hours and hours to spend on this stuff.

 

[John-Paul Townsend]

Dave,

There is a GAMI Dealer network. That really includes anyone who is listed with us as a retailer, regardless of their product knowledge level.

However, over time, we have gotten to know a lot of really great shops over the years and can often point someone to a very knowledgeable mechanic not too far away from them.

Thanks,

John-Paul

 

[Ted]

GAMI gives you identifying tags for each injector specifically to make sure that no one accidentally mixes them up. If the mechanic who installed the injectors put the tags on then there should be no friggin' way they screwed up the injector order by mistake, unless they're seriously incompetent.

There is NO way my guy would pull something like that.

That's my point - it shouldn't be difficult to confuse them, but it happens. It wouldn't surprise me if the mechs in question forgot that Continental cylinders are numbered backwards from Lycoming.

As to "no way", never say never. Human factors errors happen in maintenance.

 

[tmyers]

Ted, A mutual friend of ours is a GAMI dealer.

 

[Ted]

Ted, A mutual friend of ours is a GAMI dealer.

Yep, I'm aware.

My story goes back to PA with some mechanics that were anti-LOP and definitely not dealers.

 

[azure]

That's my point - it shouldn't be difficult to confuse them, but it happens. It wouldn't surprise me if the mechs in question forgot that Continental cylinders are numbered backwards from Lycoming.

If they forgot something like that (now I'm not a mechanic but I have to believe that's common knowledge among mechanics) then I stand by what I said, they're incompetent. If they refused to go back in on their own dime once called on the mistake, they're not even worthy to be called professionals.

Even though normally I'm a Hanlon's razor type person, in this case, I'll vote for malice.

As to "no way", never say never. Human factors errors happen in maintenance.

Of course. That's why after every annual I fly above the airport for a half hour or so and do another thorough pre-flight, check for leaks, etc. before heading anywhere. Some errors are more egregious than others though.

 

[Dav8or]

Dave,

There is a GAMI Dealer network. That really includes anyone who is listed with us as a retailer, regardless of their product knowledge level.

However, over time, we have gotten to know a lot of really great shops over the years and can often point someone to a very knowledgeable mechanic not too far away from them.

Thanks,

John-Paul

I suppose this is sort of a PM thing, but I looked at your dealers list for my state and LASAR is on the list. I use them for my annuals and like them a lot and highly recommend them to all Mooney owners. I'm sure they will sell and install your products, but they are not LOP advocates. They have told me not to run LOP or their will certainly be problems.

What I'm hoping to find is a shop, or mechanic that is enthusiastic about LOP to really work at getting my engine to run smooth past 15 degrees LOP.