M52 Turbo Build Help

**zr7685** · 04-11-2018, 08:56 AM

As the title suggests, I’m looking for some of you e36 vets out there to see if you can help me with a couple questions i have in relation to a turbo build I’m about to undergo with my e36.

I’m looking to make around 580+ hp reliably with the ability to go higher in the future.

I have not picked out any turbo components yet, right now I’m looking solely at building the engine to handle high hp and e85, components are as follows:

m52b28 block (I assume i should bore cylinders out to at least 84.5mm to fully take advantage of crank?)

S52 crankshaft

Wiseco Low Compression Pistons (8.0:5:1)

Eagle H-Beam Forged Connecting Rods w ARP 2000 Hardware

CES Cutring Head Gasket

ARP Head Studs

S52 valvetrain

Supertech Valve Seals

S52 cams

M50 Intake Manifold

Turner Motorsport Underdrive Pulley Setup

Fully Upgraded Cooling System (All aluminum radiator, stewart water pump, electric fan etc.)

Right now I’m leaning towards Southbend Stage 5 Clutch, anybody got any other recommendations?

Walbro 450 E85 Fuel Pump

E85 Compliant Fuel Lines (Anyone know where i can get quality new lines)

So thats pretty much it for things i have specifically selected right now. My questions then become mainly two things:
1. Is 8.0:5:1 too low of compression to be running e85 effectively? What compression ratio should i be after to make good power with good spool but still keep that margin safety? (Somewhere in the 9s i assume?)

2. Is running an s52 crankshaft going to change my compression? Specifically raise it? Or will m52 pistons designed to get me to x:x:x compression ratio still get me to the advertised compression ratio?

Also, slightly off topic from building the engine, but where do you guys usually run your oil feed and return lines for the turbo?

Many thanks to any of you who are able to help me out

**pbonsalb** · 04-11-2018, 08:58 AM

Why would you lower compression for E85?

**zr7685** · 04-11-2018, 09:13 AM

Originally Posted by pbonsalb

Why would you lower compression for E85?

An added safety margin. However thats why i was asking if that would be considered too low, which by your reaction i would say yes. Im really looking for that magic compression ratio that gives me an extra safety net, but still the ability to make more than enough power than what i want.

Theres some nuts out there that slap some head studs and a head gasket on a stock motor and push it till theyre making 600hp, but my main concern is to maintain reliability and build the engine to handle more than I’m wanting.

**hotdish** · 04-11-2018, 09:37 AM

I don't even have my car tuned yet, but I can probably answer some questions.

Don't forget an e85-rated fuel filter, probably more important than fuel lines. You might also want to look into adding an oil cooler if you want a really stout cooling system.

Running an s52 crank on pistons/rods designed for an m52b28 will raise your CR. Turbo oil lines depend on top or bottom mount turbo. I am running a feed off the VANOS bolt and return to an added fitting at the top of the oil pan.

**lbennyboobool** · 04-11-2018, 09:45 AM

where are you at in Missouri?

**zr7685** · 04-11-2018, 10:18 AM

Originally Posted by hotdish

I don't even have my car tuned yet, but I can probably answer some questions.

Don't forget an e85-rated fuel filter, probably more important than fuel lines. You might also want to look into adding an oil cooler if you want a really stout cooling system.

Running an s52 crank on pistons/rods designed for an m52b28 will raise your CR. Turbo oil lines depend on top or bottom mount turbo. I am running a feed off the VANOS bolt and return to an added fitting at the top of the oil pan.

Yes good call on the fuel filter, that completely slipped my mind. How much would you expect that crank to raise my CR? Enough for me to grab those 8:5:1 pistons if i wanted to shoot for somewhere around 9:5:1 Compression?

Also, I’m gonna go top mount, ive read and seen a few setups where they tapped the metal s52 oil filter housing for a feed and had a return similiar to yours in the oil pan which is what I’m leaning towards since i have an entire s52 laying around for parts.

Any recommnedations for an oil cooler?

- - - Updated - - -

Originally Posted by lbennyboobool

where are you at in Missouri?

St. Louis

**lbennyboobool** · 04-11-2018, 10:22 AM

cool! there's allot of good BMW people up there. I'm like 6 hours away, so I was just curious.

Bradley Motor Werke would be a good resource to bounce ideas off of too, if you wanted someone local to chat with

Good luck with your build though!! Sounds like it will be fun!

**zr7685** · 04-11-2018, 10:33 AM

Originally Posted by lbennyboobool

cool! there's allot of good BMW people up there. I'm like 6 hours away, so I was just curious.

Bradley Motor Werke would be a good resource to bounce ideas off of too, if you wanted someone local to chat with

Good luck with your build though!! Sounds like it will be fun!

I’m actually on my way to Bradleys right now! Toms always been a good guy to deal with in my experience. Very knoledgeable. In addition to forum threads like this he has also been a big help in the process. I’m gonna be getting the m52 thats going to be built from him in about an hour. Thanks for the good wishes, I’m sure theres plenty of stressful nights ahead trying to put this in my car so I’m sure ill need them 😂

**JOutterbridge** · 04-11-2018, 10:39 AM

E85 is better at high compression. If you lower it that much you're only losing efficiency. 8.0 is good for 90 octane and boost. I wouldn't go lower than 9.5 on an E85 build. Your power levels aren't that high for supreme caution...

**wgknestrick** · 04-11-2018, 10:41 AM

I wouldn't bore the block if you don't have to. The added material between cylinders is helpful to seal the head.
Pistons....would try to target around 9:1-9.5:1 CR. Lower than that starts to feel dead off boost. If running E85...will allow for much high CR

**hotdish** · 04-11-2018, 11:23 AM

Originally Posted by zr7685

Also, I’m gonna go top mount, ive read and seen a few setups where they tapped the metal s52 oil filter housing for a feed and had a return similiar to yours in the oil pan which is what I’m leaning towards since i have an entire s52 laying around for parts.

Any recommnedations for an oil cooler?

If you have the engine apart, the front timing cover might be a better location for the return depending on your setup. I'm running the rallyroad vanos bolt with a -4an fitting for my feed since it was pretty cheap, clean, and easy.

The euro s50 had an oil cooler with thermostat integrated into the filter housing and some vendors sell versions modified for the standard m50/m52/s50us/s52. There are also oil cooler caps with fittings for a cooler, but no integrated thermostat there. You're going to have to ask someone else for recommendations on cooler size and fitment.

**zr7685** · 04-11-2018, 11:52 AM

Originally Posted by hotdish

If you have the engine apart, the front timing cover might be a better location for the return depending on your setup. I'm running the rallyroad vanos bolt with a -4an fitting for my feed since it was pretty cheap, clean, and easy.

The euro s50 had an oil cooler with thermostat integrated into the filter housing and some vendors sell versions modified for the standard m50/m52/s50us/s52. There are also oil cooler caps with fittings for a cooler, but no integrated thermostat there. You're going to have to ask someone else for recommendations on cooler size and fitment.

Yeah the engines apart so i can pretty much put an oil feed wherevers best right now. As for the oil cooler, Alright will do. Thanks for the help. As for a tune i planned on going through RK Tunes but as of right now i need to make sure i know what CR pistons to get to put me somewhere right around 9:5:1 with this s52 crank.

**someguy2800** · 04-11-2018, 02:42 PM

I wouldn't do anything less than 10:1 for strictly E85 use. Mine is 12:1. The underdrive pulleys are a waste of money. S52 valve springs is not much if any of an upgrade, they are pretty much the same. The best and most durable valvetrain in my humble opinion is a complete non vanos M50 head. Just takes a little grinding on the front and you can put your vanos unit and S52 cams in it. The pistons have to match the stroke, M52 pistons with an s52 crank will hit the head. If I were buying a new clutch I would get the twin disc that CES sells. You don't need an oil cooler unless your tracking the car.

**zr7685** · 04-11-2018, 05:55 PM

Originally Posted by someguy2800

I wouldn't do anything less than 10:1 for strictly E85 use. Mine is 12:1. The underdrive pulleys are a waste of money. S52 valve springs is not much if any of an upgrade, they are pretty much the same. The best and most durable valvetrain in my humble opinion is a complete non vanos M50 head. Just takes a little grinding on the front and you can put your vanos unit and S52 cams in it. The pistons have to match the stroke, M52 pistons with an s52 crank will hit the head. If I were buying a new clutch I would get the twin disc that CES sells. You don't need an oil cooler unless your tracking the car.

If i shouldnt go less than 10:1 for a stricty e85 car then i can assume a slightly lower CR is preferred for a car that is not strictly run on e85? Meaning if i chose not to permanently run the car on e85 i should reduce compression?

Also if running the s52 crank with stock m52 pistons will hit the head then how can i tell that I’m buying oistons that wont hit the head? This is the first time ive heard of this being the case. The whole point of using the m52 block is to keep the advantage of having a smaller bore so I’m obviously not going to be using s52 pistons. How can i tell whatever aftermarket option i go with wont hit the head like the stock m52 pistons would?

**someguy2800** · 04-11-2018, 06:03 PM

Originally Posted by zr7685

If i shouldnt go less than 10:1 for a stricty e85 car then i can assume a slightly lower CR is preferred for a car that is not strictly run on e85? Meaning if i chose not to permanently run the car on e85 i should reduce compression?

Also if running the s52 crank with stock m52 pistons will hit the head then how can i tell that I’m buying oistons that wont hit the head? This is the first time ive heard of this being the case. The whole point of using the m52 block is to keep the advantage of having a smaller bore so I’m obviously not going to be using s52 pistons. How can i tell whatever aftermarket option i go with wont hit the head like the stock m52 pistons would?

You need to order pistons with the bore, stroke, and rod length you want. If you increase the stroke with the same rod length that means the piston is going to go higher up in the bore. Just have to call wiseco or JE or whoever you want to buy them from and tell them what you need. They are all made to order so its the same price. If your going to run 91 octane at any time I would do 9.0:1.

**zr7685** · 04-11-2018, 06:07 PM

Originally Posted by someguy2800

You need to order pistons with the bore, stroke, and rod length you want. If you increase the stroke with the same rod length that means the piston is going to go higher up in the bore. Just have to call wiseco or JE or whoever you want to buy them from and tell them what you need. They are all made to order so its the same price. If your going to run 91 octane at any time I would do 9.0:1.

That makes sense. I believe somewhere along the line i read a thread about a build very similiar using the s52 crank in an m52 block. They made it very apparent that 135mm rods specifically were what had to be used and now i believe that is for this reason. Ill go back and do some digging and see if i can find some threads to help me out

**someguy2800** · 04-11-2018, 06:11 PM

That has nothing to do with it. M52's and S52's both have the same 135mm rods. The height of the pistons are different. Lots and lots of people use S52 cranks in M52 blocks. Its been a very popular combo for a long time.

**someguy2800** · 04-11-2018, 06:17 PM

The distance from the center line of the crank to the top of the block is 210mm. Rod length is 135mm. Half the stroke of an M52 crank is 42mm, and half the stroke of an S52 is 44.8. Head gasket is 1.75mm and the minimum piston to head clearance is about 1.25mm

That means,

210 - 135 - 42 + 1.75 - 1.25 = maximum piston height for an M52 is 33.5 mm

210 - 135 - 44.8 + 1.75 - 1.25 = maximum piston height for an S52 is 30.7 mm

piston height being the distance from the center of the pin, to the top of the piston. This is called "pin height"

**zr7685** · 04-11-2018, 06:20 PM

Originally Posted by someguy2800

That has nothing to do with it. M52's and S52's both have the same 135mm rods. The height of the pistons are different. Lots and lots of people use S52 cranks in M52 blocks. Its been a very popular combo for a long time.

It doesnt have nothing to do with it. If i were to run rods longer than 1 i would run into the same problem with the pistons hitting the head. And if it had nothing to do with it then why make it seem like i really had a choice to be made as far as rod length? If s52 and m52 rods are both 135mm then it would seem that would be the rod length i should use.

Just to be clear then i should be asking whatever company I’m buying pistons from for pistons that match the height of s52 pistons?

**zr7685** · 04-11-2018, 06:26 PM

Originally Posted by someguy2800

The distance from the center line of the crank to the top of the block is 210mm. Rod length is 135mm. Half the stroke of an M52 crank is 42mm, and half the stroke of an S52 is 44.8. Head gasket is 1.75mm and the minimum piston to head clearance is about 1.25mm

That means,

210 - 135 - 42 + 1.75 - 1.25 = maximum piston height for an M52 is 33.5 mm

210 - 135 - 44.8 + 1.75 - 1.25 = maximum piston height for an S52 is 30.7 mm

piston height being the distance from the center of the pin, to the top of the piston. This is called "pin height"

Ok so then I’m after 135mm rods with pistons that have a pin height of 30.7mm?

**guc32** · 04-11-2018, 06:34 PM

Look into M54B30 pistons. They have the same crank and rods from the S52. If I recall, putting the M54B30 pistons into a M52 block, the piston sits 2mm below the deckline at TDC.

So getting a piston for M54B30 is what you are going for.

Many have done the M54B30/M52 Hybrids motors.

**someguy2800** · 04-11-2018, 06:35 PM

All M5X motors use 135mm rods except the vanos m50 which is 140mm. So there is no real choice in the matter, you have to use 135mm rods. Just call your choice of piston company and tell them you want 84.5mm bore pistons for an S52 and they will know what to do. And yes a pin height of 30.7 would be right. 30.5 would give you some room to surface the block.

**zr7685** · 04-11-2018, 06:48 PM

Originally Posted by someguy2800

All M5X motors use 135mm rods except the vanos m50 which is 140mm. So there is no real choice in the matter, you have to use 135mm rods. Just call your choice of piston company and tell them you want 84.5mm bore pistons for an S52 and they will know what to do. And yes a pin height of 30.7 would be right. 30.5 would give you some room to surface the block.

Sounds good. So then with me buying the right pin height pistons i shouldnt have to worry about the crank effecting my compression should i? Or as long as I’m buying 135mm rods, and 30.5mm pin height pistons, then the conpression will be as advertised on the pistons?

**someguy2800** · 04-12-2018, 07:31 AM

As long as the stroke is also specified as 89.6 so they know the swept volune

**pbonsalb** · 04-12-2018, 08:14 AM

Keep it simple. Buy from a shop or piston company that has done this many times. I would bore your M52 block to S52 aftermarket piston bore and decide whether you want E85 CR or pump gas CR. It’s all available. You don’t need to run M50/52 bore unless you want to make 900+ rwhp. Displacement helps spool a turbo.