Man with spanners - thinks he's a mechanic

[b33fy]

Apologies if I’ve missed this.. what is the state of the bores? Are there honing marks present, are they super smooth or glazed?

[ChrisL]

Bores are all good, heads good no. 3 piston not so! What I don’t understand is I’m running a very conservative amount of boost IIRC 9 psi!!

2861480D-AAE0-443F-BDD3-816C3084AE72.jpeg (92.29 KiB) Viewed 2838 times

And any recommendations for some cheap pistons that can cope with 9 or (if I’m going down this route) 12 psi?

[ChrisL]

And by cheap I mean relatively, forged pistons aint cheap!
Am I right in thinking I'll need rods as well? I seem to remember that blacktops use a heat process to secure the gudgeon pins?

As another thought as to why I'm still mashing pistons even at 9 PSI, although it's only one (I think) could this be a pre ignition problem? I thought I was being v very conservative with my ignition map but as I'm learning every time I do something atm... Here's my ignition map, does it look sane/safe:

[SteveRST]

Standard pistons and rods should be good for at least 15 psi. But the ignition timing, fueling and intake air temps have all got to be right.
So I don't think the pistons themselves are the problem - rather the result of another problem.

What compression ratio are you running? I can't remember if you have a decomp plate fitted?

I was running 12 psi (180 kpa) for many years with standard internals (but low compression) and no issues. And the engine was ragged!
This is my ignition table for that engine, but this was running a 3mm decomp plate and 2 x headgaskets, so very low compression. Prob 7.5:1.

The new engine I'm building - which doesn't have the decomp plate fitted - will be about 9.5:1 compression ratio and I'll be taking a good few degrees of timing off the map above. I'll maybe take off another 4 degrees of timing under boost.

So yeah, I'd say your ignition map is too far advanced under boost conditions.

Also - What air charge temps are you getting under boost? Anything over 60 degrees you want to start retarding timing too.

Fueling you can monitor, but I'd be aiming for the 11's AFR at around 10-12 psi. It's better to start mapping it richer and then analyse your datalogs and lean the map off where you can.

Also - run on super unleaded. Especially for mapping or if you're ragging it. Less chance of pre-ignition.

Finally, what plugs are you running? You want something rated colder than the standard zetec plugs. I've always run the Ford Motorcraft Focus RS Mk1 plugs.

[ChrisL]

Hi Steve, appreciate the detailed response.
Looking back through this thread it seems that I originally started off with a more reducing timing (download/file.php?id=12256&mode=view) however this got lost on all later versions of my tune!!

Compression ratio is standard, normal head gasket and no machining so should be 10:1.

MAT peaked at 60.8, AFR is about 12.7 above 100kPa, and running standard plugs.
Quite a few things pointing to pre-igniton then, it all makes a lot of sense and saves me an awful lot of cash.
Question now is where to get my hands on a zetec piston? I think it'll be buy a new engine time, unless anyones got one knocking about their garage? If you have please ping me (see what I did there?)

[ChrisL]

New engine on its way, well hopefully next week! I'm planning on just nicking no.3 cleaning it up and putting new rings on.

Re: Spark plugs, seems there's a premium for the motorcraft plugs, so am thinking of getting an equivalent. The motorcraft part number is AYFS22FE-1J which using this site https://uk.sparkplug-crossreference.com/convert/ford/AYFS22FE1J is the same as NGK PLTR6A-10G which I can get for about £30, leaving enough change for a couple of beers...

[ChrisL]

And I've updated the AFR and ignition tables to something slightly more sane! Was watching a YouTube vid last night and I quote "the last time they let me loose with a laptop the car was knocking its t1ts off!". My how I scoffed
New on the left, old on the right:

[ChrisL]

With more than a little trepidation I went out in the car! Seems to be OK so far. Will run a compression test once things have cooled.

[ChrisL]

And the scores on the doors? All within 10% of each other

[greenwoo]

well that's good news....so where are things at overall Chris?