M20 B3x Naturally Aspirated Stroker build past, present and future

[digger]

There was no need to goto the extreme of a tool steel. Some of those steels are very notch sensitive.

[ForcedFirebird]

To add..I have personally machined 4340, it's ratjer soft prior to hear treat. Straw color, dipped in carbonated oil, a file couldn't scratch it. Snapped like a pencil after we hobbed the gears. A & D tool steel in the raw, hardened, then ground took carbide to re-machine.

Perhaps it's too hard/brittle for an oil pump drive?

[ForcedFirebird]

If it were so easy, it would be common. Thanks again for the insight, Digger.

Why not treat it like a tool? Use something like D1, heat treat, harden, then grind? Wouldn't be far off from a HSS drill/mill

[digger]

Plain bearing journals are hardened to stop the journal being damaged if you get crap through the engine, the bearing fails or the film gets compromised to limit the damage that occurs, ‘normally’ its riding on a film and not required. I've seen many BMW engines with crapped rod bearings haven’t need a crank regrind (have seen others that do depending how severe failure is) it seemed like a good option.

The lip seal providers recommend (depending on brand) a HRC 35 for regular seals or 45 HRC for higher speed shafts or 55 for the PTFE seals. I don’t want the seal to wear a groove prematurely so seems like a good option. This should be noted for those wanting an oil seal sleeve for the stroker cranks when using in an m20 engine they need to be good quality steel to last a long time

Heat treatment to increase hardness increases the fatigue life though that’s not why I did it. Hardness is directly related to UTS which forms a large part of the endurance limit. Nominally the endurance limit is ~50% UTS then there are several knock down factors e.g. surface finish, loading, size, reliability factor and stress concentration and so forth.

It’s a modified “4340” material.

[LJ851]

It's a plain journal bearing and seals don't need hardened surfaces to run on. If it were a rolling element bearing, it would need to be hardened.

How did you heat treat it? Hardening can hurt fatigue life, depending on other factors.

I @$$ume you had at least the necked shank shot peened.

What steel did you go with? 4340?

What? Why are all plain bearing crankshafts hardened if they don't need it ?

[The Dark Side of Will]

Its heat treated because the journals , the oil seal surface and the press fit.

It's a plain journal bearing and seals don't need hardened surfaces to run on. If it were a rolling element bearing, it would need to be hardened.

How did you heat treat it? Hardening can hurt fatigue life, depending on other factors.

I @$$ume you had at least the necked shank shot peened.

What steel did you go with? 4340?

[LJ851]

Very Very Nice, digger !

[digger]

An important piece to the puzzle finished. I needed a custom intermediate shaft to clear the big 93.8mm crank as even with a nice aftermarket slim rod it fouls alot.

Most people know the intermediate shaft drives the oil pump, but it is also an idler shaft and as such carries the timing belt tension and loads to drive the valve train which are cantilevered off the end. This is the reason it is so large in comparison to the oil pump shaft. if you do some load calculations and stress analysis and estimate fatigue life you cant just hack into it and expect it to be trouble free

If you machine the stock ones down too much you can cut through the heat treat and end up with flimsy shitty cast iron of sorts so didn't want to risk it. Fortunately with the 89.6 mm shaft it needs minimal material removal so most don't encounter this. i did however get told by someone who lightened one to reduce rotating weight that it failed and that it is indeed hollow to get oil to the inner bearing.

Those with engineering back ground will know what a bending moment diagram is and be aware that bending stress is proportional to (D^3-d^3) and stiffness is (D^4-d^4). So if you have say an 18 mm shaft and neck it to say 14 mm the stress goes up x 2.12 and fatigue life reduces x 10.

Knowing this i also tried to minimize the amount of material removed so that I didn't make it too flexible which might cause the intermediate shaft bearings to crap out too soon. The reason they can crap out is as the shaft bends the edge of the bearing gets very high local pressures and improper lubrication and I’ve seen some blocks where the front bearing has deteriorated.

To address all this I got the shaft made from high tensile steel bar and had it heat treated, plus i designed it with very low stress concentrations in the areas I modified so i didn't introduce any issues.

Since i had no drawings to start with i had to do my own so onto designing one I destroyed a couple of old shafts to get the gear off to use on mine (press fit) and the oil gallery plug as well as measure some important parts like the oil gallery hole size etc

I measured every dimension in fine detail and then 3D modeled in CAD with full detailed drawings including dimensions, tolerances, surface finishing requirements and heat treat. Its heat treated because the journals , the oil seal surface and the press fit.

I got one 3D printed to check clearance before going to production.







did a test fit into the block i will be using and it glides nice and smooth

it may seem like a simple part but even being an Engineer i realised there is a lot more that goes into it than at first glance and i learnt a lot through the research i did in designing and understanding what specs to use etc.

[ForcedFirebird]

Personally, I prefer boosted assist.

Drove a car today, just around the parking lot with a Chase Bay booster delete kit. Lee's is far better IMO. Both have fairly hard pedals, and specially on high demand stops, it's for the birds. Lee's has instructions to re-drill the pedal for the brake clevis pin, which helps a lot. Need to tell this client to do that same.

To the defense of both situations, the car had a stock master. With a smaller master, there would be more pedal modulation, but perhaps I'm just a wuss and prefer assist. :/

[digger]

x3 of these in client cars...

http://www.massivebrakes.com/brake-systems.php?p=brake-booster-delete

If you purchased from Lee, he is a super stand up for support. Shoot him an email. He recently helped me set up an e30 with 300mm/298mm rotor weird brake system an owner brought in. Front are 6 pot and rear 4 pot and he was able to tell me within seconds my bias situation for the hydraulics to function predictably.

its one of those things that id like to try before i buy

[ForcedFirebird]

what sort of numbers did that make?

Hasn't been on the rollers yet. Showed up a couple times during tuning sessions, left both times before it was his turn to make pulls.

[digger]

Yes, I know where the build is going, and TQ is best for a street going car. :)

Your new engine will be a torque monster!

I had the pleasure of driving and tuning a 3.1l m20 built at e30 motorworks with ITB, 11:1, 282/284 dual patter cam (85mm/89.6mm). With 4:10 gears it can actually accelerate from a stop in 4th gear! Pulls like a diesel truck, but not exactly a revver.

what sort of numbers did that make?

[ForcedFirebird]

x3 of these in client cars...

http://www.massivebrakes.com/brake-systems.php?p=brake-booster-delete

If you purchased from Lee, he is a super stand up for support. Shoot him an email. He recently helped me set up an e30 with 300mm/298mm rotor weird brake system an owner brought in. Front are 6 pot and rear 4 pot and he was able to tell me within seconds my bias situation for the hydraulics to function predictably.

[digger]

which boosterless kit did you use? like below?

https://www.r3vlimited.com/board/showthread.php?t=368382

i have the wilwood calipers 1.5" pistons and 280mm discs on the front, standard rear so not standard setup but not exactly huge either.

im not after something touchy like a modern jap car but something that responds linearly with no oh shit moments

[ForcedFirebird]

Oh, and have done a couple massive booster delete's. Definitely change the pedal ratio, you will need the leverage. The pedal will be rock hard, and with standard pads is an unhappy experience. Going to use the smaller master as Lee suggested to bring pedal modulation back, but in all honesty, any brake assist is better than none. The 2002tii booster is tiny and has almost as much vacuum surface area as the stock e30 booster, but is expensive for what it is. There are so many hot-rod aftermarket variations that are cheap and reliable (domestic US), but the master bolt pattern is way off of anything German.