There's been discussion on www.ABdiesels.com on CR injection timing which involved some melted down CR's that has got me thinking.


The Smarty programmer allows for numerous options in injection timing.

I can see that if the injector nozzle size is increased but no other changes, this essentially "advances" the injection timing. The pulse width electronic signal has not changed, nor the start of the pulse width but more fuel is delivered & earlier with the same pulse width since the injector flows more fuel.

This must explain why the Smarty offers timing options to RETARD injection timing when larger injectors are used??

Carrying this further, if the rail pressure is increased but no other changes, wouldn't this also essentially "advance" the injection event? Similar to a larger injector nozzle, more fuel is delivered with the same pulse width.


Are there not 2 things going on here? Injection event timing & combustion event timing?

By increasing the injector size &/or rail pressure the combustion event is occuring earlier even though the electronic signal timing to the injector has not changed.

Advancing the timing of the pulse width to the actual injectors of course will advance the combustion event.


So if one has larger injectors, increased rail pressure plus advances the pulse width injector timing, you are essentially GREATLY advancing the combustion event??
All this is soooo easy & common on a CR, which may explain why so many are melted down??

Just thinking out loud here...

 

oh no, he's figured it out......

 

There is about a 40 page thread on this on compd.

In reality CR motors melt, because they were designed to do this, they melt even stock, it's just what they do.

 

Well I have never melted any of mine.. Melting mostly happens in the numbers 5 and 6 cyls. This is mostly caused due to high egts and very poor cooling on those cyls. This is where bypass kits such as opies or the like come in.
When you get too much timing you will cause a condition of higher (sometimes much) cyl pressure which will then cause the head to lift. This is what is happening to Torreys truck, he is just slamming the timing to it, and then running nitrous, which also increases timing. So as a result he ends up replacing head gaskets, even with the 14mm studs he has. With my old engine I ran my smarty on level 8 (no timing) and then hit the nitrous. Pressure does not add timing. It isnt changing the time that it come in, just allows for more to come in at the same time. I am still a fan of certain pressure boxes. Ones such as the dr p just plain old work. I have been smacking as much pressure into my injectors for several years now, never a single injector problem,, but then again I am very careful as to the fuel I put in it too.

 

You're also running an 03, instead of the the 04.5-07 engines, which have a notorious reputation. In reality, pressure doesn't add timing, but it does increase the rate of combustion, so the fuel is consumed much faster. Temps are now higher for longer, as well as the cylinder pressures are higher, which decreases the flame front to the surface of the piston. Just like how detonation does in a gasser.

Either way, no one really knows where the timing is set with these programmers unless you put a scope on it, and thats just bad way of tuning an engine.

 

I'm pretty sure DAve is wiht me on this one, Thank god forthe 12V's

 

well even if you scope them you wont know, because it is dynamic timing.

 

... I never thought about it that way, but it make sense.

 

Why not? Scope them on a dyno.

 

Run the injector outputs through a data acquisition system and plot injector signal to RPM.

 

they adjust timing, not just based on RPM, but based on load too. So a full rpm throttle with no load will produce a different ammount of timing than a full load pulling a trailer say.

 

So, the more injector/spray you have, the more you have to back timing down?

 

to a certain point.. I do not like adding extra timing for sure when you are modified to any degree. I think that anyone over 500 hp can cause serious detriment to their engine by adding extra timing. And, well if you add nitrous, you are really playing with fire on the timing end....

 

I like your idea, how fast is your sampling rate on your data acquision equipment. You could record each firing event for the entire pass or dyno run. I think it wouldn't be hard to do. You can see whats actually occurring and adjust stuff, to prevent nukes

 

Like I said, do it on a dyno. Then you can see what your timing will be, and adjust it so see gains/losses.