Engine Build - Conrods and Pistons

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Mitevo7

1,000 RPM
Senior Member
Jan 14, 2008
1,456
179
3,163
Dear All,

After missing in action for a while, i am back with some questions. Currently i am looking to build an engine for my Lancer GT 08, which bolted on custom turbo kit in late 2021. The car is running without much issues, boosting at 0.67, producing 257whp and 280 Nm of torque. The engine was tuned with safety in mind and AFR running 11.1 at full throttle. Recently i bought a used and running engine to start on a journey on building it to be a proper turbocharged engine with oil jets. I am researching on conrods and pistons to match up with my 4B11 NA crankshaft and i found that aftermarket rods for SR20DET is the closest one to the 4B11 crankshaft.

1.) Want to check with you guys if the SR20DET conrods can be bolted up to the 4B11 crankshaft. From the table i presented, it seems like the big end diameter is a match, but the small and big end width is 1mm larger for SR20DET, compared with 4B11. Not sure if that 1mm difference is make a lot difference in clearance. I also attached measurements table for all of you guys to refer to. Can someone enlighten me ?

2.) And also note that SR20DET rods are shorter by 12.9mm while having the same 86mm x 86mm bore and stroke. In theory shorter conrods can benefit from low RPM exhaust gas scavenging, which helps turbo to spool even earlier and faster, however due to the length of the rods being shorter, that increase lateral thrust force, which can increase wear on cylinder wall.

Hope to get some opinions for the board on this :) Thanks in advance.

P/S: Please don't ask me why didn't get an 4B11T engine, i am not interested to go with that setup that commonly people use, furthermore, the manual gearbox requires some shaving to matchup with the bellhousing and that would be very dangerous at the wrong hands. My turbo kit is 100% custom and i can safely said i am the only one with this build.

1674023113300.png
1674024125046.png
 

Izso

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Helmet Clan
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Mar 28, 2004
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I honestly have no idea whether this rojak will work or not. I'm a snob when it comes to aftermarket parts - like why not just CP/Wiseco terus for peace of mind. haha
 

Mitevo7

1,000 RPM
Senior Member
Thread starter
Jan 14, 2008
1,456
179
3,163
Dear All,

After missing in action for a while, i am back with some questions. Currently i am looking to build an engine for my Lancer GT 08, which bolted on custom turbo kit in late 2021. The car is running without much issues, boosting at 0.67, producing 257whp and 280 Nm of torque. The engine was tuned with safety in mind and AFR running 11.1 at full throttle. Recently i bought a used and running engine to start on a journey on building it to be a proper turbocharged engine with oil jets. I am researching on conrods and pistons to match up with my 4B11 NA crankshaft and i found that aftermarket rods for SR20DET is the closest one to the 4B11 crankshaft.

1.) Want to check with you guys if the SR20DET conrods can be bolted up to the 4B11 crankshaft. From the table i presented, it seems like the big end diameter is a match, but the small and big end width is 1mm larger for SR20DET, compared with 4B11. Not sure if that 1mm difference is make a lot difference in clearance. I also attached measurements table for all of you guys to refer to. Can someone enlighten me ?

2.) And also note that SR20DET rods are shorter by 12.9mm while having the same 86mm x 86mm bore and stroke. In theory shorter conrods can benefit from low RPM exhaust gas scavenging, which helps turbo to spool even earlier and faster, however due to the length of the rods being shorter, that increase lateral thrust force, which can increase wear on cylinder wall.

Hope to get some opinions for the board on this :) Thanks in advance.

P/S: Please don't ask me why didn't get an 4B11T engine, i am not interested to go with that setup that commonly people use, furthermore, the manual gearbox requires some shaving to matchup with the bellhousing and that would be very dangerous at the wrong hands. My turbo kit is 100% custom and i can safely said i am the only one with this build.

View attachment 584648 View attachment 584649
Sorry all, made a mistake on the measurement of 4B11 conrods, the length is 143.6 vs SR20 136.3, so its a 7.3 mm shorter, but i am pretty sure SR20 pistons height are taller than 4B11 NA pistons.
 

Mitevo7

1,000 RPM
Senior Member
Thread starter
Jan 14, 2008
1,456
179
3,163
I honestly have no idea whether this rojak will work or not. I'm a snob when it comes to aftermarket parts - like why not just CP/Wiseco terus for peace of mind. haha
I am going aftermarket actually, mostly looking at Carillo or Maxipeedingrods as they are kinda affordable. Pistons wise maybe go with 1JZ ceramic coated pistons. As for conrods big end width, my mechanic buddy said shaving off 0.5mm per side on the SR20 rods is safe to do so to fit on the 4B11 crankshaft, as long as not the mid rod. What do you guys think ?
 
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