[alien]

Hey guys... any thoughts on why a fully rebuilt 1.6 bottom end with jimny EFI top end would do its rings after only 9000km??? 2nd time mines done it now and im wondering if its me or possibly bad rings (brand?)

some background info on me and my driving style:
- i let it warm up in the driveway in winter (about 5-10mins) before driving to get the heater cranking before i get in.
- i rarely, if ever take it to redline - maybe once every 2-3 months
- i always drive in the ideal rev range (2500-3000rpm)
- i don't put my foot to the floor
- i always downchange to slow down (engine braking)
- offroad i keep revs low (1500-3000rpm)
- it never overheats as i run a thermo on separate switch for crawling (when it heats up)
- always run 20w50 oil, non synth
- never let oil get below half way.

Anything else that might contribute???

[steak_knife]

What brand of ring's & are you honing the bore's??

[joeblow]

too small a piston for the bore size.

[rogerworkman]

do you have a air filter in it

[jonno_racing]

whats the clearance like bore to pistons?

get it reboared with new slugs and rings and it should be fine.

[Brett]

bores are ovaled or pistions are the wrong size would be my bet. also letting a engine idle is the quickest way to glaze the bores.

what exactly is happening? blow buy, blue smoke low comp?

[steak_knife]

o2 sen stuffed & running rich, washing the oil off the bore's..

[alien]

compression is fine, don't think theres blow-by... but getting a TON of blue smoke under load... its not anywhere near as noticeable on road except for a cold start (leave it for 2hrs plus) - offroad it just lays a smoke screen. Heres a pic from last weekend driving on a slight uphill:



im not doing the work myself - its been done by a shop both times. Both times its been rebored with brand new rings and pistons. The current engine is a fresh one with only honing as a precaution (it was very clean to start with). They were very embarassed the first time it did the rings, theyre outright ashamed right now... lol

As for idling, like i say its only 5-10mins, usually 5... the engine doesnt get up to temp in this time, its only enough that the heater just starts warming up and de-fogs the front window so i can see. I've not glazed the bores ever before and this is technically my 3rd engine if you count the old 1.3.

Whats interesting is when it was converted from 1.6 carby (which ran strong for 7 years) to the jimny top end and EFI, it did the rings about 6 months after that - and the bottom end was never touched when the EFI conversion was done... I question whether the jimny top end is giving too much compression and shortening the life of the rings? Doubtful i know given rings are designed to remedy exactly that, but possible?

EDIT: O2 sensor thing is a great idea - thanks!

[royce]

check your mixtures under load

[joeblow]

alien wrote:

Whats interesting is when it was converted from 1.6 carby (which ran strong for 7 years) to the jimny top end and EFI, it did the rings about 6 months after that - and the bottom end was never touched when the EFI conversion was done... I question whether the jimny top end is giving too much compression and shortening the life of the rings? Doubtful i know given rings are designed to remedy exactly that, but possible?

EDIT: O2 sensor thing is a great idea - thanks!

are you running an o2 sensor and a working speed sensor?

also what efi ecu and sytem are you running?

[alien]

1) unsure, i think i have an O2 sensor and no speed one.

2) efi and ecu is jimny.

[joeblow]

without an o2 sensor you will be running rich.



and without a working speed sensor your ecu will go into 'limp' mode.....once again making the engine burn too rich.


if the shop had known this i'm sure they would have sent you packing.

[atari4x4]

i think the shop is the one who did the install & would have thought they would have known better.....

[joeblow]

atari4x4 wrote:

i think the shop is the one who did the install & would have thought they would have known better.....

oh dear then.....................

[oozuk]

Most problary running lean with the jimny ecu being the fact that the ecu is mapped for a 1300cc engine

[joeblow]

oozuk wrote:

Most problary running lean with the jimny ecu being the fact that the ecu is mapped for a 1300cc engine

no.....without either of those two sensors working properly....let alone together it will be running way too rich.

[alien]

worth checking out for sure! thanks guys =)

[MacDaddy]

alien wrote:

Hey guys... any thoughts on why a fully rebuilt 1.6 bottom end with jimny EFI top end would do its rings after only 9000km??? 2nd time mines done it now and im wondering if its me or possibly bad rings (brand?)

some background info on me and my driving style:
- i let it warm up in the driveway in winter (about 5-10mins) before driving to get the heater cranking before i get in.
- i rarely, if ever take it to redline - maybe once every 2-3 months
- i always drive in the ideal rev range (2500-3000rpm)
- i don't put my foot to the floor
- i always downchange to slow down (engine braking)
- offroad i keep revs low (1500-3000rpm)
- it never overheats as i run a thermo on separate switch for crawling (when it heats up)
- always run 20w50 oil, non synth
- never let oil get below half way.

Anything else that might contribute???

To my way of thinking, there 2 things that leep to mind, Temp and Lubrication, they are getting to hot, and lack of good lubrication...

My first thought was that that oil is too thick, i ran 15W 40 Semi Synth in my G16A, and i noticed the difference from 20W 40 Mineral, the engine just felt looser to me ... 20W is, to me, a bit too thick for an high revving, higher performance alloy engine... i may be talking in an area i dont know much about... but i would definitely think about switching to a thinner Semi Synth Oil !

[shandy92]

off topic, macbear you have a PM,

[Lokidog]

Actually I think MacBear may have a point with the oil grade. Most newer engines run on a lighter grade oil. A freshly rebuilt engine shouldn't need to run on 20w50. Especially if it has a later model head.

I use to run 20w50 before my rebuild. Post rebuild I have only used a 15w40.

I also wouldn't think 5-10mins of warming up an engine would glaze the bores. Not unless this was done while the engine was still bedding in, during it's first 1000k's.

[alien]

yeah was never done in first 1000 - was summer then =)

will also ask about oil for sure as that will directly affect rings.

[royce]

that small a difference in oil grade isnt going to cause that, 20-50 is still within the recommended grade limits

[Hybrid]

I would have thought they could tell it was running rich when they tore it down the first time. Surely fueling would have been one of the first thing they checked.

[JrZook]

Hybrid wrote:

I would have thought they could tell it was running rich when they tore it down the first time. Surely fueling would have been one of the first thing they checked.

Whats your economy like? Seems like you ain't too hard on it at all so you should be getting around 10k's per liter or better. How about the r8un in procedure? Same for both times? What did it consist of?

Dan

[royce]

keep in mind too that smoke under load isnt so much a factor of poor compression ring sealing but poor oil rings, they could of been installed wrong

[shep]

i would look at the cleanliness of the air that the motor is eating.
sounds like you are dusting the motor.

[alien]

economy is pretty good - its the same as when i ran the weber on the 1.6... around 9km to the litre... not bad considering 31's and SPOA.

i agree on rings vs oil rings - but does that still explain smoke on startup? Also, i've not had someone tail me on the road to see if it is smoking - i just cant see it like i can offroad.

as for cleanliness of air - i'm running a snorkel with no pre-filter to standard sierra airbox running a paper filter. My oil is also pretty clean still so i dont think dirt is an issue.

[losfer]

need more info , when you say going through rings , are they breaking , or wearing out (unlikely) , or when its pulled down the rings are fine but the bores are glazed ?

im sort of siding on bore washing / bad run in .

[alien]

last time it was pulled down the bores were fine and rings were worn, oil rings were stuffed... not sure on this time but i'd assume the same has happened.

[shep]

is the ring gap being checked during assembly? if not then that would be a good start.