Common rail diesel discussion thread

diesel1972

Naturally-aspirated

8

01-25-2020, 06:49 AM #94

Believe me I’m a walking calculator if it comes to fuel models on diesel engines. LOL.

Here is one. When do you want max combustion pressure??? Around 20 up to 30 ATDC depending on stroke/conrodd length and bore size and just before you hit max piston speed so where the conrodd and crank are @ a 90 degree angle.
On a modern not a old CR engine you will have a burn delay of about 5 degrees under boost. And with a modern I mean Euro6 tier 4 final and stage 5 running injection pressure way over 2000Bar on the CR system but most of the small bore engines do not run or have this and partly due to development stop by some OEM it will never get there as well and combustion temp will be very hi making it hard not to use an all steel pistons. But anyway.

Old school is slam diesel fuel in as hard as you can and see what happens not getting to critical on start of injection gaining massive power sometimes. Try this on a modern engine that’s lots more efficient and you will lift the head bent connrods and so on as like a petrol engine it not very intolerant on advanced injection building combustion pressure very fast so how to get around this as for hi CR and boost unable to get more than 5 to 10 degrees advance in on start of injection??? Well two things. Follow the combustion and keep injecting up to about 30 ATDC if you can not go advanced in injection that’s is or lower the compression ratio able to get some more of this diesel evaporation cooling/delaying rapid rise of combustion pressure able to advance a bit more. It’s like getting best of both worlds on combustion/efficiency less smoke but hard to run alloy pistons as they will crack or melt due to thermal stress.
Things will get interesting when your able to build engines that can do over 450Nm per 1000cc engine displacement and you can not produce any visible smoke or you will get a black flag on track. If it can smoke we easy make 1000Nm per 1000cc and this year we ho to try to run some test on these 10.000Hp hub dyno’s as we are getting some finally in Europe as well.
Some fuel model we use for them derive from testing piston liner combinations for OEM suppliers starting years in advance for main production so we get to know most fuel systems in advance and know what not to do with them as these run 24/7 on test. After this the OEM can have there play time getting it emission approved so some of us can look for how to delete some of it again. LOL.

Will start on making a breakout loom today I hope for the DID1 Common Rail Diesel ECU.