Geo Metro 1.0L G10 engine rebuild mods for better MPG

[Christ]

Did you check Majestic Honda?

[Gasoline Fumes]

Originally Posted by Christ

Did you check Majestic Honda?

I checked their site, but I don't remember if I contacted them.
http://www.hondaautomotiveparts.com/...IN+Number+---#

[Wonderboy]

I spent a long time fighting with my lathe today... But I finally got an alright solution. I visually turn it down to just over half width with a dremel stone in the lathe chuck, with the ring clamped to a bit. Then, I used a file to gently and gradually bring it down to as close to halfway as my measurement tools/eyeballs can tell me. I found that the best way to do this is to measure the overall thickness of the lap instead of each half individually.






I don't know if it's an issue, but the corner of the cut on each edge of the ring kind of sinks down a little bit from the edge due to my imperfect filing abilities, but after I looked at the stock ring, noticed there was a bevel, and added a similar bevel to mine, it seemed to fit quite well. Whaddaya guys think, I don't know how much better I could get at this with the limited machining tools I have. I don't know how important perfection is here, but something tells me some imperfect lap is better than a gap. Edit: The filing looks a little rough, but of course I plan to use a whetstone to make it nice and smooth.

[Christ]

Not necessary to smooth the filing, just make sure the piston and cylinder bore sides (I.D. and O.D.) of the rings are smooth with no burrs.

That filing job is a thing of beauty, I must say. It's exactly what I had in mind when I described what was going through my head for making a gapless ring a few posts back.

Let's hope they work, eh?

[TimG]

Not a Metro owner, but I did install the Total Seal rings on a Datsun quite a few years ago. They never gave me any problems, seated up quickly, haven't worn prematurely.

The reason they can decrease friction/increase mileage is that they can function with a lot less spring pressure- the gapless design seals well enough when cold or upon start-up that normal spring pressure isn't needed. Gas pressure takes over, though, so I don't know how much of a FE increase you will get compared to standard rings, at least if you have a long commute where cold starts have a lesser effect. They do have a reputation of maintaining good compression for a long time because of the wear pattern of the two different ring materials.

I think you will need a much more precise step in the standard ring to actually get some gapless benefit. It does need to be a gas seal, after all.

[Wonderboy]

Welcome to EM, TimG! Thank you for the input. Now I'm back on the fence again. I PMed johnny mullet about this issue - hopefully he'll reply and put the last nail in this coffin.

[Christ]

Originally Posted by Wonderboy

Welcome to EM, TimG! Thank you for the input. Now I'm back on the fence again. I PMed johnny mullet about this issue - hopefully he'll reply and put the last nail in this coffin.

FWIW -

It's a gas seal, sure, but I don't think it really needs precision due to the pressures involved. I think that under the combustion/compression pressures, the rings will likely "close" themselves, especially at the speeds they normally travel up and down the cylinder bore.

You also have to remember that gasses will always take the path of least resistance... combustion gasses won't like changing direction 3 or more times to get through the filed ring, so you're not likely to lose much of anything.

No ring is totally sealed, either. There's always going to be some blowby, which is part of the reason that racers use gas porting on their pistons.

[robertwb70]

Originally Posted by Wonderboy

more spring force (= more compression?)

I dont think any of the 1.0l G10 engines had EGR, right?

I couldn't tell you what kind of change you would see if you were to remove all the 2nd rings from a stock G10 and added gapless top rings, but if it resulted in an efficient gain, I'm almost certain it wouldn't be as significant as swapping the cam out and getting an advanced timing sprocket

More spring force does not mean more compression, when it comes to ring pressure it's not a case of more is better but a case of adequate is all you want- any more is unnecessary friction imposed on what is (IIRC) already the single highest frictional loss in the motor.

As far as I know 1991 was the only year the G10 didn't have EGR ( for the standard model at least, don't know about the XFI)

I've thought about using gapless top rings and removing the second rings as well, bu the higher cost dissuaded me (and IIRC they didn't make gapless tops in the right size at the time, about 2 yrs ago) so I just went with gapless second rings instead.

If it were me I'd try the rings you've made, just make sure the ends can't butt up against each other once operating temp is reached and make sure you're OK with the possibility of tearing back into the engine if they don't work out...

I knew a guy that raced VW Sciroccos and used the zerogap rings, he told me he had to replace the pistons every season but that he used the same rings for 3 seasons so far at that point.

I think the real benefit from using them comes once the engine gets up there in mileage. Performance/ efficiency wise you'd probably get as much benefit from anti-friction (DFL) and/or thermal barrier (ceramic) coating (the appropriate part of) pistons.

[TimG]

Christ-

I think the stepped gap will work just fine, if proper care is exercised regarding gaps being adequate for thermal expansion. But the gain compared to going with the Total Seals is probably closer to 25% than 75% IMHO. It is cheap and easy, and should increase FE, hard to complain about that.

[Wonderboy]

I received another vote for reuse of the stock rings. Still a tough choice, but actually starting to lean toward reuse. I emailed the guy who made this site about our situation, but still no reply. There might be some value in heating up the original rings while they are open a bit wider than they are in their "relaxed" position to give them a tad more spring force. That would solve all the questions here if it actually worked. I PMed Johnny Mullet a while ago now about this, but no dice there either. I really wish he'd respond.