UPDATE – One year after
10-18-2011, 03:07 PM
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Join Date: Mar 2010
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UPDATE – One year after
Some of you may remember my threads from a year ago, concerning an engine failure which was caused by a combination of too much timing, too lean a mixture, too low octane fuel and too hot plugs.
Engine failure: https://rennlist.com/forums/911-foru...ure-again.html
Fuel: https://rennlist.com/forums/911-foru...el-to-use.html
I had relied on an engine builder who seemed to know how to generate power, but didn’t provide good advice regarding durability.
My engine is a 3.2 litre based on a 3.0 case with 98 mm pistons, PMO 46 mm carburetors and WebCam 120/104 cams, with a compression ratio of 9.3:1.
Thanks to the advice gathered here and from other engine builders all over the continent, I tuned the newly assembled engine for durability.
After the break-in period, for all subsequent track days I mixed 109 unleaded with Shell 91 for an average octane of about 96-97. Timing is set to peak at 32-33 BTDC. I use NGK BPR7ES plugs with an MSD system, gapped to 0.050”. The carburetor main jets are 160 and the air correctors are 180, producing an air/fuel ratio of about 0.85 Lambda at 6000 rpm. I have an Innovate AFR gauge with 2 oxygen sensors and VDO Cylinder Head Temperature gauges with thermocouples on plugs number 3 and 6. I have also installed block-off plates on the engine to direct all of the cooling air to the cylinders. CHT’s never exceeded 350 F all season long. Oil pressure and temperature remained at acceptable levels except on the hottest of days, when the oil temperature reached 120 C, when I stopped to allow it to cool down.
This year I have done 28 track days at seven different tracks, for a total of about 30 hours on this engine. The engine is pulling as strongly as ever and compression/leak down measurements are still very good. I may not be getting quite the maximum power that I could, but the engine will last and I’m enjoying myself thoroughly. BTW I have also installed a roll bar, Sparco seats and Schroth harnesses and removed the radio, speakers, back seat and door panels, substituting a set of home-made RSR-style panels. The weight is about 2680 lbs including me, which is about as low as I can go without changing body panels or bumpers.
I hope this is helpful to someone and I thank you guys for the help you provided in the past.
Engine failure: https://rennlist.com/forums/911-foru...ure-again.html
Fuel: https://rennlist.com/forums/911-foru...el-to-use.html
I had relied on an engine builder who seemed to know how to generate power, but didn’t provide good advice regarding durability.
My engine is a 3.2 litre based on a 3.0 case with 98 mm pistons, PMO 46 mm carburetors and WebCam 120/104 cams, with a compression ratio of 9.3:1.
Thanks to the advice gathered here and from other engine builders all over the continent, I tuned the newly assembled engine for durability.
After the break-in period, for all subsequent track days I mixed 109 unleaded with Shell 91 for an average octane of about 96-97. Timing is set to peak at 32-33 BTDC. I use NGK BPR7ES plugs with an MSD system, gapped to 0.050”. The carburetor main jets are 160 and the air correctors are 180, producing an air/fuel ratio of about 0.85 Lambda at 6000 rpm. I have an Innovate AFR gauge with 2 oxygen sensors and VDO Cylinder Head Temperature gauges with thermocouples on plugs number 3 and 6. I have also installed block-off plates on the engine to direct all of the cooling air to the cylinders. CHT’s never exceeded 350 F all season long. Oil pressure and temperature remained at acceptable levels except on the hottest of days, when the oil temperature reached 120 C, when I stopped to allow it to cool down.
This year I have done 28 track days at seven different tracks, for a total of about 30 hours on this engine. The engine is pulling as strongly as ever and compression/leak down measurements are still very good. I may not be getting quite the maximum power that I could, but the engine will last and I’m enjoying myself thoroughly. BTW I have also installed a roll bar, Sparco seats and Schroth harnesses and removed the radio, speakers, back seat and door panels, substituting a set of home-made RSR-style panels. The weight is about 2680 lbs including me, which is about as low as I can go without changing body panels or bumpers.
I hope this is helpful to someone and I thank you guys for the help you provided in the past.
