iX stroker turbo Questions

[gstuning]

Nobody needs a ETA block for a stroker conversion,
the 84mm m20 block from a IX is fine for any m20 based conversion.

200whp from a M20 isn´t the hardest in the world in N/A form but it´s not cheap either.

[nando]

You don't, you use the ix block with the e crank.

[beamR X]

Got'cha.

So, excuse my total ignorance on the topic, but this means the ETA crank has simply a longer stroke,(hence the "stroker") which gives it more displacement and power all in a nice convenient package....
Cool.

Thanx!

[SpecM]

So, excuse my total ignorance on the topic, but this means the ETA crank has simply a longer stroke,(hence the "stroker") which gives it more displacement and power all in a nice convenient package....
Cool.

yep, you got it

[beamR X]

Cool.
So how much more stroke are we talking about? According to the spec sheet off of the main r3v page the "e" has 81mm stroke and the "i" 75mm. That 3mm gain on the compression. Is there enough room there for that or do I need a different connecting rod? ...specifically that I will have it resurfaced?




The M division played with 1mm on the S70.
I was studying the 850CSI V12 and I am starting to notice a bunch of parallels between the 325i "stroker" and the 850CSI "M" developed S70:

From this link:

http://www.bmwmregistry.com/model_faq.php?id=11

"DrivetrainHow is the S70 engine different from the M70 V12 upon which it is based?
When creating the 850CSi's S70 V12 motor, BMW Motorsport began with the standard 24-valve SOHC M70 engine and instituted the following changes:
-Increased bore (from 85mm to 86mm) and stroke (from 79mm to 80mm) for a new total displacement of 5,576cc (from 4,988cc)
-Lighter pistons
-Increased compression (from 8.8:1 to 9.8:1)
-More aggressive valve timing for increased high-rpm power
-Larger diameter exhaust pipes
-Variable rpm limit (6,400 in 1st+2nd, 6,200 in 3rd, 6,100 in 4th. 6,000 in 5th+6th)
-Adjustable throttle sensitivity via dual mode (Sport or Komfort) console-mounted switch
-Engine oil cooler (European-spec models only)

These modifications resulted in an increase in maximum power from 300 hp (DIN) or 296 hp (SAE) at 5,200 rpm to 380 hp (DIN) or 372 hp (SAE) at 5,300 rpm. In addition, maximum torque was increased from 332 lb/ft at 4,100 rpm to 402 lb/ft at 4,000 rpm.

This engine can be identified by the "Powered by M" inscription on the central cam cover between the two banks of cylinders."


So, reading between the lines: BMW "M" division made a 850CSI model and increased the size of the "stock" 5L V12 (pretty much 2 l6 2.5L blocks) to 5.58 L.

Hmmm.... What's more interesting is that they went from 8.8:1 all the way to 9.8:1 by increasing the stroke by just 1mm and advancing timing a bit.
Intriguing, since my Mark D chip already advances my timing so I have to run a minimum of 91 octane gas. I guess the "stroker" mod would pretty much do to 2.5 what the "M" division did to the V12. (less the bore, of course).
The torque gains are impressive. From 332 to 402. That's 70lb/ft!!!
Even if I 1/2 it that's 35lb. I don't know how much bore influences the torque in this motor, but I'd say a stoker on a 2.5 should bring at least 20-25lb/ft of torque...

How does this sound to you guys? Am I missing something? I find it hard to believe that by the same token I could gain 20-25 HP? I guess without lighter pistons that's not possible...

[nando]

it's 6mm, not 3 - and they didn't just change the stroke to get more compression, they used different pistons as well. if you used the same pistons with 6mm more stroke you're going to hit the cylinder head long before you get to TDC.

[SpecM]

don't get carried away with the v12 math, there...

you have to use either aftermarket (like MM) pistons with the "i" rods (135mm) or shorter eta rods (130mm)