Reliable M20B20 Turbo Build

[TriniGT]

Hi guys, I have been searching for some time trying to get the info before I jump on here with a new post.

I recently acquired a 320i E30 with an M20 engine that I assume is a B20 unit and as this is not planned to be my power monster I still intend to want at least a bit of fun with it.

The plan is to rebuild the engine with some quality stuff and hang a snail on it along with some subtle upgrades to give it some HP in the vicinity of 300HP.

Car is currently an auto so will be looking for a getrag 260 box but need some opinions on a proper rebuild kit, is it worth it to upgrade rods and pistons or for my power the standard setup refreshed is fine.

I am planning management of some form and also what clutch setup can handle the power?

I come from a nissan background, Silvias, GTRs, Primeras, GTiRs but have been working with BMW for several years now and drive a couple of them, soon to have complete my E60 M5, along with a E30 with an SR20VET swap but that is for another day.

Your wealth of knowledge and guidance is much appreciated as I take this unchartered journey.

Thanks in advance and go easy on me!

[TriniGT]

Ok plans have changed a bit, I reside in the Caribbean so access to parts are limited. I have since purchased an M20B25 engine that is on the way to me and would like to do a refresh on it and turbo charge it.

I am not looking for crazy power, maybe 350-400HP, so would like to have a reliable engine that the turbo can survive on as a daily/weekend street car.

What would you guys recommend in terms of rebuild items that would need to be replaced and upgraded? I have seen both Irelandengineering and bimmerheads have lots of packages but what is recommended, windage tray, baffle plate?

I am thinking irelandengineering's bottom-end & head gasket kit along with replacement water pump and timing belts etc. In terms of cam and rockers I am seeing persons using stock reground rockers. Is it recommended to change out valves, and have an angle job done.

Also for my power goals what injector size is recommended and also what clutch setup as well with the getrag 260 that I collected this weekend?

Lastly, swapping the 320i B20 for the B25 is the harness the same? I am getting a complete engine with harness and whatnot but wanted to know if to swap the entire lump or just the motor.

Jason.

[Northern]

Bottom end is fine for that power stock as long as it's in good shape.
Crank scraper/baffle should help with oil starvation in long corners if you're tracking the car.
You'll get away with a stock style headgasket (anything other than Victor Reinz) if the tune is fine.
Will want ARP head studs or "Metric Blues" from McMaster-Carr as a cheap alternative.

Head-wise, a rebuild with some sort of upgraded cam and HD rockers. Springs to suit the cam, could be stock or otherwise.
Wouldn't bother with replacing valves unless your HP or RPM goals change significantly, but some sort of valve job should be done with the head rebuild.
Maybe mild porting of the head, but only if you are getting the head done somewhere that knows M20 heads well

Injectors: Probably would go for something 50lb/hr+ because there's not much cost to be saved by anything less.
Siemens Deka 60lb (~630cc) injectors are popular because they're cheap, but be wary of where you buy them from because there are a lot of counterfeits (this goes for the EV14s below as well.)
Bosch EV14 are going to be a little more expensive but may need adapters for the connector, or installed height.
0280158117 are a Ford Motorsport 52lb/hr (~550cc) injector that are fairly cheap but need adapters for connector/height.
0280158123 is a Porsche 977 injector that is something like 60lb/hr (~630cc) but also needs an adapter for installed height only.

I'm not sure if the harnesses are the same, but if you can find both Electrical Troubleshooting Manuals online, you could compare. Might be variations depending on the year also?

Side note, I'd look at the M20b25 you receive and make sure it has the sintered intermediate gear and cam gear, and not the older stamped steel versions.
Should be able to google those for pics to verify, and some gnarly failure pictures of the stamped versions.

[TriniGT]

Bottom end is fine for that power stock as long as it's in good shape.
Crank scraper/baffle should help with oil starvation in long corners if you're tracking the car.
You'll get away with a stock style headgasket (anything other than Victor Reinz) if the tune is fine.
Will want ARP head studs or "Metric Blues" from McMaster-Carr as a cheap alternative.

Head-wise, a rebuild with some sort of upgraded cam and HD rockers. Springs to suit the cam, could be stock or otherwise.
Wouldn't bother with replacing valves unless your HP or RPM goals change significantly, but some sort of valve job should be done with the head rebuild.
Maybe mild porting of the head, but only if you are getting the head done somewhere that knows M20 heads well

Injectors: Probably would go for something 50lb/hr+ because there's not much cost to be saved by anything less.
Siemens Deka 60lb (~630cc) injectors are popular because they're cheap, but be wary of where you buy them from because there are a lot of counterfeits (this goes for the EV14s below as well.)
Bosch EV14 are going to be a little more expensive but may need adapters for the connector, or installed height.
0280158117 are a Ford Motorsport 52lb/hr (~550cc) injector that are fairly cheap but need adapters for connector/height.
0280158123 is a Porsche 977 injector that is something like 60lb/hr (~630cc) but also needs an adapter for installed height only.

I'm not sure if the harnesses are the same, but if you can find both Electrical Troubleshooting Manuals online, you could compare. Might be variations depending on the year also?

Side note, I'd look at the M20b25 you receive and make sure it has the sintered intermediate gear and cam gear, and not the older stamped steel versions.
Should be able to google those for pics to verify, and some gnarly failure pictures of the stamped versions.

So much thanks for replying, as for the sintered gear the engine came out from a 1990 325i, so hoping that is a good sign. I am looking at adding a GTX3071/76R to it along with cam and possibly rockers.

What clutch setup you recommend for me if I were to drive it as a daily driver application with normal traffic.

Also I am seeing many recommend the MS2 but seeing the cost getting into the standalone ECU range so was thinking of an AEM Series II used maybe but not fully convinced on any ECU in particular.

In terms of injectors would prefer a drop-in set to not make things complicated so any suggestion on this is also appreciated.

I will have a small swirl tank setup to eliminate starvation, walbro pump, FPR, custom made possibly twinscroll manifold for a twinscroll turbo, does anyone know the firing order/sequence to develop a twinscroll maniflold setup for the 6 cylinder?

Also anyone with knowledge that may have done a 320i to 325i engine swap?

Thanks.

[Northern]

Clutch, I'm not very well versed in current M20 offerings, but I remember SPEC Stage 3 was popular a few years back for that power level and decently cheap. Fits with the M20b2 flywheel, 6 puck sprung hub clutch disc.
Another long standing popular option is the Sachs SRE -618 pressure plate and an organic disc. Hopefully google can find the rest of the part number from that, and clutch disc that fits.

ECUs, I'd shop around. Depends on who is tuning the car, lots of tuners will have a brand preference. Also depends on how much wiring you can/want to do.