LOP dilemma

[lr172]

Superior mentions in one of their talks that having 80 compression (or very close to it) on a mid time engine is a concern that the rings were not installed correctly. he sounded like it's a bigger concern than if you see 60s.

Yes, if you get 80/80 there is a good chance you have a 0" ring gap and cracked rings are in you near future. It is theoretically impossible to get MORE than 80 PSI of measured pressure with an input pressure of 80, assuming the piston is not moving, hence the comment about inaccuracies in the gauge. This is an issue with superior, as they ship their rings oversized and expect the installer to file them down to size. Major opportunity for errors, as Lyc ships them pre-sized. Easy to forget if you usually use Lyc.

Very easy to create offsets for gauge inaccuracies. With the tester not connected to plug adapter, run the input up to 80 and read the other gauge. Your offset is 80 +- whatever the indicated gauge reads. Mine reads 2 PSI low, so I just add 2 to each measured result.

 

[Carl Froehlich]

My GAMI spread is about 0.5gph. I really want to put a slightly larger orifice on #4.

I suggest the preferred approach to balance cylinders is to always go leaner (smaller nozzle) on the rich cylinders. Don Rivera discusses this from time to time. I do not go bigger than the stock 0.028” nozzle.

On an IO-360 my experience is two new nozzles and GAMI is down to 0.0 to- 0.1gph. My first IO-540 took ~4 new nozzles.

Side note - on the IO-540 I was using a plenum without turbo nozzles. This caused me to do more nozzle iterations to get the desired GAMI spread. It started off at 1.5 GPH but it too got down to 0.0 - 0.1 GHP. Still deciding if I want to put turbo nozzles on the new RV-10. Phase One will provide the needed decision data.

Carl

 

[skirting_virga]

I suggest the preferred approach to balance cylinders is to always go leaner (smaller nozzle) on the rich cylinders. Don Rivera discusses this from time to time. I do not go bigger than the stock 0.028” nozzle.


On an IO-360 my experience is two new nozzles and GAMI is down to 0.0 to- 0.1gph. My first IO-540 took ~4 new nozzles.

Side note - on the IO-540 I was using a plenum without turbo nozzles. This caused me to do more nozzle iterations to get the desired GAMI spread. It started off at 1.5 GPH but it too got down to 0.0 - 0.1 GHP. Still deciding if I want to put turbo nozzles on the new RV-10. Phase One will provide the needed decision data.

Well, I was a dumbass and got GAMI injectors for certified prices instead of going to AFP. I couldn't figure out if the restrictors were removable, but I have certainly considered turbo-style injectors plumbed to the snorkel for max ram air pressure differential.

So what this boils down to is I have no idea what the orifice sizes are. I believe the front #1/2 injectors are GAMI's minimum size and no smaller size is available, so it is only possible to make 3/4 larger. If there's a way for me to investigate orifice sizes, I would like to do that (but that assumes the value is stamped somewhere and the orifice is removable).

 

[[email protected]]

Yes, if you get 80/80 there is a good chance you have a 0" ring gap and cracked rings are in you near future. It is theoretically impossible to get MORE than 80 PSI of measured pressure with an input pressure of 80, assuming the piston is not moving, hence the comment about inaccuracies in the gauge. This is an issue with superior, as they ship their rings oversized and expect the installer to file them down to size. Major opportunity for errors, as Lyc ships them pre-sized. Easy to forget if you usually use Lyc.

Very easy to create offsets for gauge inaccuracies. With the tester not connected to plug adapter, run the input up to 80 and read the other gauge. Your offset is 80 +- whatever the indicated gauge reads. Mine reads 2 PSI low, so I just add 2 to each measured result.

Ya I'm in the cracked/broken ring group on somebody else's over haul in the past. I always check the ring gap per manufactures rules and don't create problem not needed. And yes I run LOP as much as possible. TRUST AND VERIFY!!!
The OP's mechanics are out to lunch on this one.
My luck varies unless I am the one screwing it up. FIXIT

 

[Carl Froehlich]

So what this boils down to is I have no idea what the orifice sizes are. I believe the front #1/2 injectors are GAMI's minimum size and no smaller size is available, so it is only possible to make 3/4 larger. If there's a way for me to investigate orifice sizes, I would like to do that (but that assumes the value is stamped somewhere and the orifice is removable).

I would hope each nozzle has a stamp on orifice size. I do have any experince with GAMI nozzles so see if you can pull out a nozzle and look.

Carl

 

[Treekiwi]

So who makes this claim?

I really don't want to name the shop, but suffice to say they've been doing this a long time, and have a good reputation. Which, of course, could make them even more susceptible to OWT I suppose.
It didn't sound quite right to me, which is why I threw it out there.