89.6mm Crank, 135mm Rods, Which Pistons?

[AWDBOB]

Hey R3V-

Currently have a myriad of parts in my garage that I can make a stroker out of quite easily, and since I am selling off my 24v stuff I am entertaining the idea.

Option 1:

M52b28 Crank, 130mm ETA Rods, late "i" pistons (84mm bore)
Results: 2.8L, 9.7:1 if block shaved down 5mm

Upsides: cheap+easy
Downsides: refitting an 84mm piston in a stock sized bore and lowest displacement
Poor R/S Ratio w/stubby 130mm rods
Crank/Block need to be clearanced due to large couterweights



Option 2:

M52b28 Crank, 135mm Rods, IE Mahle Pistons (85mm bore)
Results: 2.9L, 9.8:1 compression

Upsides: nice set of pistons, best R/S of the bunch
Downsides: same/less money to go 3.1L
Crank/Block need to be clearanced due to large couterweights


Option 3:

S52/M54b30 Crank, 135mm Rods, Custom Pistons (either IE or Cp VAC Pistons), 85mm bore
Results: 3.1L (really 3.051L), compression of your choosing (10.5:1)

Upsides: same cost as going 2.9L
Smaller couterweights on S52 crank than M52
Downsides: I'm assuming this pushes the wrist pin up into ring territory? Oiling/longevity issues potentially?
Intermediate shaft needs to be clearanced.
24v 135mm rods supposedly clear fine+are lighter, but this config with m20 135mm rods needs clearanced


Supporting mods:

I have a Schrick 284/272 and am working with John @WOT to figure out a cylinder head. IE Longtubes, RR throttle body. SSSquid tune on 1.3 ECU for now until standalone.



Questions:

What would you do? Option 1 above, I have everything. Both Options 2+3 all I'd have to buy are pistons.

IF you chose Option 3, what pistons are best to work with?

I have seen CP: https://store.vacmotorsports.com/cp-...ank-p2921.aspx

And then whatever IE sells on their site (maybe ross?)

Thanks for any thoughts you may have-

[redlightpete]

For option 1, the crank needs to be cut down to clear the pistons. It should clear the block fine (or at least mine did). You'll probably need to cut the valve pockets deeper in the stock pistons too.
I don't think you need to cut down the crank if you use the IE/Mahle pistons, so that would offset the cost a little. Also, you'll have new pistons and a presumably optimal bore size, not loose worn parts.

[AWDBOB]

For option 1, the crank needs to be cut down to clear the pistons. It should clear the block fine (or at least mine did). You'll probably need to cut the valve pockets deeper in the stock pistons too.
I don't think you need to cut down the crank if you use the IE/Mahle pistons, so that would offset the cost a little. Also, you'll have new pistons and a presumably optimal bore size, not loose worn parts.

Yes, my thoughts as well. Option 1 may not be any cheaper because of the machine work that the pistons will require.

Did you use an early block? I've read they have better clearance for whatever reason. I also have an S52 crank and 135mm rods. S52 crank has smaller counterweights and supposedly only requires light machining to the intermediate shaft.

My worry with that combo is pushing the wrist pin up too high and having it interfere with the ring pack. I'm trying to find a specific piston that folks have had success with using the S52 crank/135mm rods.

[digger]

if you are going to get custom pistons, go with OEM dome, so on a 3L forget about IE or VAC.

certain dealers can get JE with OE dome, otherwise send of a OE slug to CP and get them to copy it

A 3L needs a big valve head, decent lift cam and good intake manifold to make power

[AWDBOB]

if you are going to get custom pistons, go with OEM dome, so on a 3L forget about IE or VAC.

certain dealers can get JE with OE dome, otherwise send of a OE slug to CP and get them to copy it

A 3L needs a big valve head, decent lift cam and good intake manifold to make power

Good to know- I figured (hoped) that since IE asks what head you'll be using with your piston set they would have a dome that works with it. I'll try to find a JE dealer who is familiar with the platforms. Although if they're crazy expensive, I'll just buy the Mahle 2.9l pistons that are built for it from IE and use my 84mm/135mm setup.

I read about squish band with the 885 frequently, but am wondering what exactly are the 'side effects' of going wirh a piston done that doesn't have a raised squish band. Is it (pre)detonation? Not maximum efficiency? I'm just curious, as there have to be thousands of M20 strokers out there, only a few of which I'm sure have custom pistons fitted to work with an 885.

And I don't think I'll be doing OS valves or ITBs just yet, I just want to add some beef to the bottom end once it's out of the car since I have most of the parts to make it happen.

[SkiFree]

On a scale of minimizing risk/unnecessary cost, while maximizing power/engine longevity, option 2 makes the most sense. Little biased obviously, but these were the parameters I balanced.

[zaq123]

On a scale of minimizing risk/unnecessary cost, while maximizing power/engine longevity, option 2 makes the most sense. Little biased obviously, but these were the parameters I balanced.

also option 2 will not require any crank machining, balancing etc...only minimal clearancing of the block would be needed, very very minor. Depending on the machine shop prices, option 1 can get close to the price of the option 2 due to all required crank work, piston work (had to relieve valve pockets, balance etc) etc.

I did all the comparison a while back and the option 2 with Mahle pistons made much more sense.

[AWDBOB]

On a scale of minimizing risk/unnecessary cost, while maximizing power/engine longevity, option 2 makes the most sense. Little biased obviously, but these were the parameters I balanced.

also option 2 will not require any crank machining, balancing etc...only minimal clearancing of the block would be needed, very very minor. Depending on the machine shop prices, option 1 can get close to the price of the option 2 due to all required crank work, piston work (had to relieve valve pockets, balance etc) etc.

I did all the comparison a while back and the option 2 with Mahle pistons made much more sense.

Thank you all for your thoughts on this, I think it's the route I will go.

[digger]

The IE pistons don't seem to give you the OE dome when you select the 885 head, I guess they just need to know the different chamber volume for the determination/calcualtion of the CR.

Squish/Quench helps with knock, if you have knock then you need to pull timing which hurts power. Also squish is worth a bit more power and torque due to the faster burn which means less negative work. There are SAE papers showing the benefits. The most benefits are at lower to mid rpm as at high rpm the higher velocity of the ports inherently creates more turbulence in the chamber anyway.

The OE design also has some other features that are proven such as centering the combustion space around the hotter exhaust valve and plug for improved vaporization and combustion.

It makes zero sense when designing a piston to use a random dome just because it happens to give you the correct CR but then again the aftermarket world is full of stuff that is less than desired.

The 3.1L in the UK that is one youtube etc had knock with IE pistons and they had to back off the timing and hurt the power to get a safe tune according to the owner. I also have a couple friends with essentially flat tops with a 2.8L and they are quite a bit knock limited on 98RON.

A set of pistons in either 4032/2618 will be under $1000. With a skirt coating they may end up the same the IE if you went that route. You can get pistons without the oil support rail if you use a modern total seal 1.0/1.2/2.0 ring and smaller pin.

A 2.8L is a sensible option and the overall package is more balanced with a mild cam and standardish ports, if you want a bigger stroker you need to push the limits of the head and cam much higher to get all the parts to work well as a combination otherwise it chokes too early.

[SkiFree]

Digger - they are referring to the IE/MahleMS pistons, which have the OEM dish.

[digger]

yeah i know, my comments were regarding the 3rd option

[clarkson]

Hey R3V-

Currently have a myriad of parts in my garage that I can make a stroker out of quite easily, and since I am selling off my 24v stuff I am entertaining the idea.

Option 1:

M52b28 Crank, 130mm ETA Rods, late "i" pistons (84mm bore)
Results: 2.8L, 9.7:1 if block shaved down 5mm

Upsides: cheap+easy
Downsides: refitting an 84mm piston in a stock sized bore and lowest displacement
Poor R/S Ratio w/stubby 130mm rods
Crank/Block need to be clearanced due to large couterweights



Option 2:

M52b28 Crank, 135mm Rods, IE Mahle Pistons (85mm bore)
Results: 2.9L, 9.8:1 compression

Upsides: nice set of pistons, best R/S of the bunch
Downsides: same/less money to go 3.1L
Crank/Block need to be clearanced due to large couterweights


Option 3:

S52/M54b30 Crank, 135mm Rods, Custom Pistons (either IE or Cp VAC Pistons), 85mm bore
Results: 3.1L (really 3.051L), compression of your choosing (10.5:1)

Upsides: same cost as going 2.9L
Smaller couterweights on S52 crank than M52
Downsides: I'm assuming this pushes the wrist pin up into ring territory? Oiling/longevity issues potentially?
Intermediate shaft needs to be clearanced.
24v 135mm rods supposedly clear fine+are lighter, but this config with m20 135mm rods needs clearanced


Supporting mods:

I have a Schrick 284/272 and am working with John @WOT to figure out a cylinder head. IE Longtubes, RR throttle body. SSSquid tune on 1.3 ECU for now until standalone.



Questions:

What would you do? Option 1 above, I have everything. Both Options 2+3 all I'd have to buy are pistons.

IF you chose Option 3, what pistons are best to work with?

I have seen CP: https://store.vacmotorsports.com/cp-...ank-p2921.aspx

And then whatever IE sells on their site (maybe ross?)

Thanks for any thoughts you may have-

Chiming in here on option one, as I have done it. Firstly, you would be decking the block .5mm not 5mm.

Secondly, if you are using the single vanos m52B28 crank no clearance machining necessary (well at least on my build).

But if I were to go again, I would go aftermarket pistons to retain the 135mm rods and get larger valve reliefs, higher compression and larger bore. The choices for pistons are much better now the dish dome shape of the factory piston has been mapped by JE etc.

Also, be careful with the sleeve you buy, or make. For the nose of the crank for the front timing case seal. Mine and a friend leaked. I have since had a spare inspected and copied and found the surface was too rough for good sealing. On my build I had to modify the front crank seal to stop the oil leak.

[zaq123]

Secondly, if you are using the single vanos m52B28 crank no clearance machining necessary (well at least on my build).

There were 2 M52 cranks. One you speak of, with smaller counter weights is not available in US market. I almost had one shipped from Germany but then went Mahle pistons

[clarkson]

I was unaware that the US m52B28 single vanos crank was different to the euro/Australian m52B28 single vanos crank....

[zaq123]

I was unaware that the US m52B28 single vanos crank was different to the euro/Australian m52B28 single vanos crank....

to be exact, there were two different cranks for M52. Unfortunately the one with smaller counterweight can't be found in US. Germany had both sizes.