High timing small displacement - does it matter

madmikeismad

madmikeismad

So mad
Joined
Dec 19, 2009
Messages
14,347
1.9l vw block, electronic ve pump. Who thinks 30* on the high end would be safe? I've never really thought about timing vs displacement before.
 
I have no idea, but a day on the dyno would tell you pretty quick.
 
I'm curious about this as well, but opposite, a larger displacement engine. A 672 cid, 12mm p-7100, 15:1 compression running around 3000RPM, is at 40* and feels like it would like more, but I'm too chicken to up it any further. I was always under impression that timing was RPM related. My 5.9 would not like 40* at only 3000RPM.
 
motorwood said:
I'm curious about this as well, but opposite, a larger displacement engine. A 672 cid, 12mm p-7100, 15:1 compression running around 3000RPM, is at 40* and feels like it would like more, but I'm too chicken to up it any further. I was always under impression that timing was RPM related. My 5.9 would not like 40* at only 3000RPM.
Click to expand...

A guy on the a vw forum told me they don't like much over 25 IIRC before they run weird, which is crazy. But it might really have something to do with overall air pumped through the engine. Like a 1.9L at 6000rpm would be moving as much air as a 5.9L at 2000rpm, and you sure wouldn't run a 5.9L at 30* at 2000rpm unless you're static and have no choice lol. (not solid math obviously, but for the sake of conversation).

Does that logic make sense?
 
Spray angles, injection pressure, piston bowl, boost, backpressure, cams etc. effect optimal timing so you cant compare 2 different engines. Also where you measure it, at the pump or at the injector.
 
MadMike, let me know if I'm hijacking too much.
Leiffi, let's say fuel systems are similar (p-7100 mechanical), for the 5.9 and 11L? I can move the 11L from 34-40* and barely notice a difference. On the 5.9 that same movement is huge. Why? Also, I assume your 12L is a modern common rail or unit injection?
 
motorwood said:
MadMike, let me know if I'm hijacking too much.
Leiffi, let's say fuel systems are similar (p-7100 mechanical), for the 5.9 and 11L? I can move the 11L from 34-40* and barely notice a difference. On the 5.9 that same movement is huge. Why? Also, I assume your 12L is a modern common rail or unit injection?
Click to expand...

No, P-pumped MAN race engine. My 14,2 Scania race engine didnt like much over 27 degrees, at 30 I lost bottom end coming out of corners. It was 27 at the pump, at the injector something like 20 depending on rpm due to 65 centimeter injection lines. 13mm 8-cylinder P-pump.
 
it has more todo with stroke of crank then anything. Smaller stroke crank can run more timing as the Piston is moving "slower" think of a 2" stroke vs 6" stroke and keep timing the same.

If I wasn't on my phone I would figure out the distance the Piston have left to travel between the 2 that will help you understand the amount of timing you can run.
 
The 11L has a 6inch stroke. Thanks Leiffi, I'll try the transducer near the injector and see the difference, our lines are 96cm. With our pull class, bottom end isn't a factor. Great info folks!
 
I'm not sure what the stroke is on a 1.9 vw tdi, but I'm sure it's not much LOL But based off that I should be able to really crank the timing up right?
 
motorwood said:
The 11L has a 6inch stroke. Thanks Leiffi, I'll try the transducer near the injector and see the difference, our lines are 96cm. With our pull class, bottom end isn't a factor. Great info folks!
Click to expand...

Bosch makes some injector bodies with sensor for ECM, if your engine happens to have same type of injector you might be able to use it. But you can just try more timing, just be careful at lower rpm at max load, only way to find perfect timing.
 
turbom700 said:
it has more todo with stroke of crank then anything. Smaller stroke crank can run more timing as the Piston is moving "slower" think of a 2" stroke vs 6" stroke and keep timing the same.

If I wasn't on my phone I would figure out the distance the Piston have left to travel between the 2 that will help you understand the amount of timing you can run.
Click to expand...

It is about the pressure in the cylinder, not piston travel. Longer stroke usually have more volume to compress. It has more to do with rod/stroke ratio, that tells you have fast piston is moving close to tdc.
 
You must log in or register to reply here.
Back
Top