M30B35 on petrol / LPG. CR increase - discuss please......

[petrol_1]

Speaking to ANT ,
hes run a e30 m20 on 11.4 on motronic which was ok on 95 ron too!
so im looking at 11:5 or 12;1 on lpg!!!!!!
lpg forums recon that uk lpg is the purist avail so this implies 12:5 but i m not that brave !!
is your system venturi or 6 seperate lpg injectors like mine, , the venturi systems do nt give even fueling / cylinder ,so i would be careful and not push to far but it appears 11 o4 would be ok hope this helps

[gareth]

Cheers for that.

Mine is a venturi system, though i doubt it will give uneven fueling with the position of my venturi being before the AFM.

the head is off getting a 1mm skim as we speak (9.8:1 CR). I keep getting tempted to mess with it more but i don't really see the point - if significantly more power is the target - i'd change the engine for something better suited.

[petrol_1]

the design of the inlet manfold directly effects the uneveness of fueling .
i think the 325 ones good no to sure of the m30 , but the hi the C/R the more efficient the engine the more power /more MPG too,

Remember most cars will be ok 9.8 to 95ron so i would be looking a least on 11 :1 ish to max the LPG , mines looks link 12:1 or just over for the first trail , as its free if your skiming it any way.
I beleive the m30 heads stronger / less cracking than m20 s so if its getting new big ends and main s it will take it well but the choice is yours ,
yo can alwalys swop the front end lpg sytem over later , but be aware the single multivalve tanks do nt flow much over 200bhp ( also use 8 mm pipe to the froont of the car , not 6 mm ok fot micra s not BMW s )

[Andy335Touring]

Do a dummy build to check your *squish* clearences, not too sure what they are supposed to be but after a lot of googling when i did mine 1mm seems the norm.

*piston to head*

[gareth]

Petrol_1, skimming much more will lead to a longer string of issues to sort which are all going to hinder getting the thing back on the road and back into daily use. my E30 has spent enough time immobile during the time i've owned it, i just want to enjoy the thing! Anyway, the whole time i have a flappy AFM and a new (LPG) venturi restricting the airflow, it's never going to be a firebreathing engine. a solid reliable 200+ bhp on either fuel will keep me happy for this car. It is after all the car i use every day for the school run (and occasional track day) and when i'm not buggering around with it, it's a very reliable and practical everyday hack. it would be a shame to spoil that.

I don't have the money to throw at the 'ideal' build spec so there's no point going too far with it. The engine looks very fresh (100k miles) so i'm not going to touch bearings etc as i bet they'll be good for another 250k yet!
If i chase more power on a E30 again, it'll be a something like a supercharged 2.8 M20 powered ix and i'd build the engine up from scratch to suit the necessary work. I do keep getting tempted with more and more things i could do to the engine at the moment but must be restrained!

Andy, on my dummy build, there was loads of clearance in the squish areas. probably one of the reasons Alpina had a fettle in that area... as you well know


while i've been waiting for the head to come back, i've been getting tarty... i now have a lovely satin black rocker cover with polished ribs and BMW lettering the manifold is getting the same treatment too once i've finished fitting the pressure release valve.

[gareth]

I took delivery of my freshly welded and skimmed head yesterday the welder reckond it's ont of the best condition old heads he's seen and went to town on it as he liked it! every bit of corrision was ground out beyond where the metal was grey and porous then welded back up. thid has now been degreased and pressure waahsed ready for some valve lapping (joy) and rebuild!!!!

the manifold is now modified for the pressure relief valve and painted up. looking utterly awesome too! that and the rocker cover will make the rest of the engine bay look really bad now! the new inlet hoses should help though...?

hopefully i'll get some tasty pics up this weekend

i'm not expecting to get a hge amount done this weekend as i am busy getting another year closer to death tomorrow but i should be back on the road this month, in time for the zone roam to scotland next month!

[DRIFTBOY]

Happy birthday mate!

I look forward to seeing the beast re-fettled, maybe catch you at a Kent Diner meet sometime...?

Good luck with the build, don't forget the piccies!

[petrol_1]

WHO have you used for the welding and skimming ? any b4 and after pics

[gareth]

cheers martin! I'll definately be along to a meet or two in it soon!

I'll have to get some more pics this weekend but it's all coming along nicely!

The skimming and welding was done by this lot http://www.applegate.co.uk/engineering/ ... 600139.htm local to me and a jolly splendid bunch cost me £138 for a helecoil job on one spark plug hole, the 1mm skim and the welding (8 places in the end iirc!)

[gareth]

a productive morning today - but no time to spend on it in the afternoon which is frustrating as the head is now back on and awaiting a torqueing session

piccies time...

the head as removed:




naughty inlet gasket!!!! bet it'll run a bit better with this sorted!:


freshly skimmed and cleaned up, valves cleaned on a lathe and then nicely lapped back in:




behold the tartyness!:




injectors having a blast through my ultrasound cleaning tank


all rebuilt and ready to fit. note the addition of a pressure blowoff valve to aid things in he event of a LPG blowback:

[320Touring]

luvverly work Gareth!

should be plenty pokey up them pesky scottish hills

[gareth]

and if not, at least it'll look nice when i'm fixing it!

[DRIFTBOY]

Oooh, sexy big six rightness!

Lovely looking job mate.

[gareth]

cheers