Stock, stroker or ghetto capacity increase? ( supra 7m gte pistons bmw rods )

[prj]

Should be between 2.3L and 2.4L.
Someone should really take a scientific approach to calculating this.

But the lower compression ratio and the fact that you can run 30+ deg timing while it is spooling up without getting knock really helps spool as well.
Of course not on these graphs, because here it is spooling early in the rev range, I mean if you suddenly floor it at 4000 rpm for example.

[A80Avant]

definitely.

well there you go, another way of doing a half way stroker then!

[prj]

Yep, technically of course it is not a stroker, because stroke is the same.
It is the bore that is increased.

[prj]

Btw, driving this thing feels exactly like driving a car with stock turbo.
Except it has 400+ hp.

It has all the grunt down low, like with the stock turbo, you never feel that it is laggy, don't need to downshift to overtake etc etc etc...

[Rusty]

Did you have the crank eccentrically ground to take the BMW rods and thus give more stroke?

86.4mm stroke x 83mm bore = 2.34 litres.

[prj]

I did not build it!
Possible actually that the stroke did increase somewhat.

All I know is that it is an MC crank, taken to a machine shop with some BMW rods and bearings and the machine shop was told to "make it fit".

If one of you guys wants to build this frankenengine, then I will try to find out the exact details.

[Rusty]

you've been selling it too well, so we all want one now!

Approx. stroke to give a 2.4 litres is 88.7mm, thus an eccentricity of (88.7-86.4)/2 = 1.15mm . Depends on what the big end bearing diameter is on the BM rods vs. 20vt crank - if it's 2.3mm or thereabouts then 2.4 is on the cards.

Audi S2 is 48mm big end, 144mm length, from what I've found.

BMW M50 information (here) is -

Standard--mm--45.00(-0.009/-0.025)
size 1--mm--44.75(-0.009/-0.025)
size 2--mm--44.50(-0.009/-0.025)

Based on the above information, the crank could be eccentrically ground by up to 1.5mm, thus giving a stroke of 89.4mm.

There are 2 sizes of rods for an M50B20: 135mm or 145mm - it appears to depend on whether it's a VANOS engine or not - (USA linky)

Just need the deck height of the S2 and Supra pistons now...

[Rusty]

Thread renamed and stickified

[Jamo]

sorry Jamo, i did not understand you
but Prj,has anwered now , thx¡¡



, stock or very soon chipped? i believe to heard sometime that these machines can handle 420Hp only with mapping....without invest anything

It's the american term for building something on a budget using used or stock parts from other systems.

Infact half the threads on motorgeek seemed to be named this!

[prj]

I think they used non-vanos rods.

[AndyP]

Not bad for a ghetto 500 quid engine build.

Where were you two years ago before I spent a small fortune building a tall block stroker?

[prj]

Where were you two years ago before I spent a small fortune building a tall block stroker?

Driving Toyotas

Rusty, can you calculate the maximum possible displacement using this approach?
Also check the MC crank specifications.

I like that someone is working with numbers on this thing, I just don't have the time to get into it atm.

[Rusty]

Using 83mm pistons and eccentrically grinding the crank 1.55mm to give 89.5mm stroke (if that's possible) you'd get 2.42 litres.

If 83.5mm pistons and double oversized shells (44.5mm) were used, you could even take it out to 89.9mm stroke and thus 2.46 litres but that's perhaps a bit much for a small gain.

[rst]

I built this engine for this red Audi S4 that was now tuned by PRJ.

In this engine there was used MC crank and it was just milled to fit the BMW rods. Stroke stayed the same 86.4mm. Also it uses BMW NA rod bearings. (I have used 1.8 golf rod bearing on my own engine that pushed about 400kW from wheels. So dont worry people so much about the rod bearings.) I think in this setup you can go up to 7500rpm as you can with the stock pistons.

It is possible to build small block stroker with these pistons, again with BMW rods and diesel crank. The crank has to be eccentricity milled to about 94mm. Even then the pistons must be modified to clear oil squirters, but you dont have to mill down the pistons. Then you can have an engine that has about 2.54L of capacity and 8.0 compression (83mm bore and 94mm stroke). But i would not recommend to go over 7000 rpm with this setup.

[s2_wot]

The MC Crankshaft is part number "034 105 021 K" according to Kate for anybody who is searching.

Listed on the following page as shown in this photo.

http://eurospecsport.com/Eurospecsportdotcom.pdf



Andy is this eccentric grinding of the crankshaft going to be a run of the mill operation? Surely if it's a ghetto build it'll need to be easier than that process?


EDIT: For anybody reading I don't think the stroke indicated in the picture above is accurate.