ForcedFirebird's m20 dyno thread.

[AliBOSS]

It's not an 85.8mm stroke but a 3.0 crankshaft from an m54 that we balanced and lightened. So we are talking about 89.6mm

The diesel block we used the block only and adapted it to accept the 885 head. We didn't use bigger pistons, because the diesel block wouldn't support more than 84mm of boring from previous experience.

The block is actually longer that's why we used it, also a lot of modifications and grinding has been done to be able to rotate the crank without the rods hitting the cylinder wall.

Also we are using one of the worst pump gas quality wich is the only available.

[digger]

Those are some of the highest m20 numbers I have seen. I want to know every detail of this motor! I've never heard of an m20 diesel block before or anyone using 140mm rods in an m20.

MM were using 140.5mm rods 20 years ago. The diesel block is an m21 and it is where the forged 81mm crank comes from that Alpina used in their engines, and where the the high flow oil pumps that are sometimes mentioned come from.

[2mAn]

I'm not sure, we are using stock parts from other engines, nothing is forged. The static compression is around 180 but our giant retarded camshaft is lowering the numbers

Trying to break this down a little more with my failed ME math

84mm Bore X 85.8mm stroke = 2853cc or a solid 2.9L

Compression Ratio is still a mystery because US S50 had 135mm rods, EU S50 had 142mm…

What fuel does the motor like?

[88Sedan]

Those are some of the highest m20 numbers I have seen. I want to know every detail of this motor! I've never heard of an m20 diesel block before or anyone using 140mm rods in an m20.

[AliBOSS]

Those are some impressive numbers!! What’s the compression ratio on your setup

I'm not sure, we are using stock parts from other engines, nothing is forged. The static compression is around 180 but our giant retarded camshaft is lowering the numbers

[2mAn]

Those are some impressive numbers!! What’s the compression ratio on your setup

[AliBOSS]

Good Morning everyone,
I would to share with you our Frankenstein M20 that we finally dynoed 1 week ago

It's diesel block, 885 hand ported head,Dbilas open M5 3.6 itbs with their trumpets, 3.0 crank knife edge and balanced and 84mm pistons on 140mm rods, electric water pump and fan, mechanical pump deleted. Standalone ecu tuned by me.

[zaq123]

I meant thrust crank clearance.. I'm sure you got it but just in case.... Thrust bearing is the reason you should not use an impact wrench on that crank bolt btw. Hand tools only

[McGyver]

I appreciate both of your perspectives on this! The cylinders have all been bored for 0.50mm over pistons, main and rods have all been cut and bored to match the crank. Plastigauge will confirm there weren't machining mistakes. It would be cool to get the actual measurements, but I don't think that justifies buying tools with enough precision to provide a real measurement.

I plan to file the ring end gaps per cylinder for a Turbo application. I'll also measure/swap piston/rods to get even piston height at TDC for all six cylinders. And I'll balance the piston assemblies as best I can. I'll also check valve clearance to the new guides with the new cam and check piston to valve clearance with the new-but-crushed head gasket. Should be good!

[digger]

Plastigauge should not be frowned upon. Most backyard mechanics are doing this with measuring equipment not upto the job because proper equipment is expensive and cannot be justified for a once or twice off endeavor so plastigauge is probably more accurate in some circumstances than using junk equipment without experience

[zaq123]

plastigauge is fine. It has a pretty good range to get you in the ball park. I would not worry about the bore gauge ( gotta trust your machinist somehow), just make sure you measure piston ring gap once in the in the bore and adjust it accordingly. Piston to valve clearance is a must so get a second head gasket on hand...just in case. Also make sure to measure crank trust clearance ...very important

[McGyver]

most is pretty generic, the only thing thing kinda specific is the intermediate shaft bearings

I've reached the stage where I'm ready to start measuring and assembling the engine. I don't have a bore gauge or OD mics in the 0-6" range. I know that I should double check my machinist's work, so I bought plastigauge for the main and rod bearing clearances. I'm not building a 10/10ths engine, just looking for some decent longevity on a 2.7i that will get a turbo in the future.

Is plastigauge good enough?

I don't really want to buy a bore gauge right now, especially because it would only make sense to get one that reads in 0.0001" and I'd need a 0.5-1.4" for the small end of the rods, 2-6" for everything else, and a set of 0-6" mics. I plan on building at least another engine in the future, so I would get more use out of the tools. But it would also be nice to have time to find a quality used set on eBay instead of getting a cheap set of Chinese tools.

[zaq123]

I plan on using Redline Assembly lube for the whole build. Any suggestions for the break in oil?

Also, I have new mahle 84.5 pistons (11251714810). This should be roughly 9.0:1CR and then will get boosted. Should i use the rings that came with the pistons? Looks like a shiny barrel top ring, grey Napier 2nd ring, and oil control ring.
I plan to measure/gap the rings for boost.

driven br40 for the oil. follow instructions.
Mahle are good rings. Follow Mahle instructions for break-in. Keep in mind that cam break-in supersedes rings break-in but it's all plus minus the same.
Easy on the oil when assembling rings and on cylinder walls.
I recommend using Marvel mystery oil for that, coat piston bores with it and coat rings/pistons with that. Good assembly Lube on all bearings, cam, crank. If you gonna crank the engine after the assembly, plugs out so no to squeeze the lube with compression from crank bearings. Drill with long extension and 6mm socket to prime the engine before first start. Setup ECU (I assume wont be stock) to prime fuel pump so it starts asap. Didn't start withing first 3-4 sec of cranking? STOP and Start troubleshooting. Don't just sit there and keep on cranking the started while polishing your bores and messing up new rings.

https://www.us.mahle.com/media/usa/motorsports/mms-break-in-recommended-procedure-web.pdf

some general info from JE just to give you an idea
https://www.jepistons.com/ring-insta...X2NF1LyhZ44atp

[McGyver]

I plan on using Redline Assembly lube for the whole build. Any suggestions for the break in oil?

Also, I have new mahle 84.5 pistons (11251714810). This should be roughly 9.0:1CR and then will get boosted. Should i use the rings that came with the pistons? Looks like a shiny barrel top ring, grey Napier 2nd ring, and oil control ring.

I plan to measure/gap the rings for boost.

[zaq123]

don't use Lucas assembly lube or any green/blue coloured assembly lube. I almost had a heart attach when I was adjusting valves after the first start, opened the valve cover and saw some green residue mixed with gold coloured break-in oil sitting in the head.