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I am developing a high hp NA 2 litre Subaru engine and as part of that I am experimenting with a long duration exhaust cams. At 1 mm they are 264 degree, EVO 64 BBDC and close 20 ATDC The intake are 26 BTDC and 30 ABDC.
We are aiming to develop max torque at 11,000 rpm.
The engine has a standard exhaust at this time so it fires but won't start.
Any rules of thumbs such as timing to get it to start?
As it's NA, you're going to be looking at rather a lot of ignition timing - check it's around 20 degrees as a start point - also check it's firing on the compression, not exhaust, stroke.
You may find you're not cranking it fast enough, you can use a second batter on the STARTER to use 24 V BUT you will need to double, and triple, check it's isolated from the rest of the electrical system - they generally object to that voltage in an expensive fashion.
I may have to reduce the over lap a bit, the engine has AVCS on the intake so if I can figure out how to control that with the Link then it may also help.
Checked all the timing etc this morning as you suggested and its all good. I wonder if changes to the exhaust header pipe would improve things.
If it won't start, be sure to feed it enough fuel. I disagree on ignition timing for starting, you don't want too much timing, the engine will probably start a lot easier on 4-8 degrees of advance while cranking. If it cranks slowly (high compression), use less ignition advance.
Hi David the compression is 10:1
I just realized that the ECU had a fuel cut based on rev and temp, when the engine would fire the ECU would see a spike rpm of 12 k, the rev limiter was shutting the fuel at 5k. I have since tried it again and getting close to starting but not quite there. I will let the starter coll down tonight and give it a go tomorrow, I will adjust the exhaust cams forward 10 degree which may help get it started for now.
When I get it running I have pressure transducers in the exhaust so I can tune it.