M30B28 EXPERIMENTING with DYNO PROOF - Overboring/Motronic conversion/manifold changes and more..

E28 technical advice asked and given! Troubleshooting, modifications and more.
RobertRO
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Re: M30B28 EXPERIMENTING with DYNO PROOF - Overboring/Motronic conversion/manifold changes and more..

Post by RobertRO »

If you still consider a setup of late B30 (E32/E34) pistons with an 80mm crankshaft, there's right now an ad in Netherlands for a (new?) set of very rare 9.2:1 pistons for stock 89mm bore.
Note that the stated compression ratio is calculated for the late B30 cylinder head. If you use an earlier head, make sure you do your due dilligence.

https://www.ebay-kleinanzeigen.de/s-anz ... 6-223-1309

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Tibo
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Re: M30B28 EXPERIMENTING with DYNO PROOF - Overboring/Motronic conversion/manifold changes and more..

Post by Tibo »

It's been a while since the last time i posted here so here's an update!

I finally managed to find a set of pistons locally, they are from a b32. This means i'll be building a 3.2 liter instead of the 3 liter. This also means i have to use an 86mm crank instead of the 80mm i had prepared. I have one from a 3.4 liter block so i dissassembled it and brought it to the machine shop to get checked and polished.

I am still waiting on the crank now, should have it by the end of the month.

I had the pistons and the throttle body sodablasted so they are ready to go.

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Shawn D.
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Re: M30B28 EXPERIMENTING with DYNO PROOF - Overboring/Motronic conversion/manifold changes and more..

Post by Shawn D. »

Are you going to get the piston tops treated? Otherwise, those are quite rough, which could lead to preignition due to hot spots.
Panici
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Re: M30B28 EXPERIMENTING with DYNO PROOF - Overboring/Motronic conversion/manifold changes and more..

Post by Panici »

Shawn D. wrote: Feb 13, 2023 7:53 AM Are you going to get the piston tops treated? Otherwise, those are quite rough, which could lead to preignition due to hot spots.
I was thinking the same thing, those look ROUGH.

What kind of treatment would fix this?
Shawn D.
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Re: M30B28 EXPERIMENTING with DYNO PROOF - Overboring/Motronic conversion/manifold changes and more..

Post by Shawn D. »

Panici wrote: Feb 13, 2023 9:32 AM
Shawn D. wrote: Feb 13, 2023 7:53 AM Are you going to get the piston tops treated? Otherwise, those are quite rough, which could lead to preignition due to hot spots.
I was thinking the same thing, those look ROUGH.

What kind of treatment would fix this?
I'm not familiar enough to know, but the places that do such treatments would. :dunno:
Mike W.
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Re: M30B28 EXPERIMENTING with DYNO PROOF - Overboring/Motronic conversion/manifold changes and more..

Post by Mike W. »

I can't say I like the looks of those pistons, the porosity does bother me, and I haven't seen it before.

But... These are used pistons, right? They've run like that before, likely a long time. And the top will carbon up more than likely, so I don't think it will be a problem, I really don't. I actually tell people who are rebuilding engines not to bother with the tops of the pistons. I suspect I'm universally ignored, but carbon on top of the piston won't hurt anything and will reform shortly if you do clean it off. So I wouldn't worry about it.

A little late now, but rebuilding engines about all I do is decarbon the ring grooves and maybe rinse the pistons in solvent or wipe them off. They might be at the factory, but it doesn't have to be white room clean. A couple of things like bearings and crank journals need to be perfectly clean, but for the most part, no, it's not needed.

Coatings? I can't say it's a bad thing at all, but probably unneeded.
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