What's the deal with timing and the HO's? I've been running an Edge Pulse (wire to VP44 not connected) in step-above-EZ mode for a couple of years without problems. I don't race, but I do tow at sea level and high altitudes.

Am I risking a problem? How so? Not detonation....

 

Not likely, but the higher compression ratio of the HO (17.0:1 versus 16.3:1 of the SO) will result in higher cylinder pressures for the same amount of timing advance when compared to the SO. This has been a topic of discussion primarily among those of us who routinely tow HEAVY.

Rusty

 

My personal idea is that fuel flow to the vp (good pusher pump or replacement lift pump setup) is more critical than which box you're running. I'm sure any power mod will tax the equipment more than stock, but the fuel flow through the vp for cooling (fuel NOT used for cylinder combustion, but bypassed back to tank) is critical. Many failures have been electronic ,which I attribute to heat or vibration. Deal with the heat by cooling the vp better. Vibration is not as critical, I think the variation truck-to-truck is slight.
I have a couple of years on my Edge Comp with the wire tapped, the last 6 months in Drag revision and no trouble since I grounded it better (knock on skull or wood, whichever is harder).

 

By way of clarification, I'm speaking of the effects of timing boxes on HO's. I've read that they can blow out head gaskets.

Thanks, RJC, understand about cylinder pressure. I take it with "normal" use and towing this isn't so much an issue.

 

It shouldn't be since, at lower GCWs, one wouldn't have to work the engine as hard. Less fuel = lower peak firing pressures.

Rusty

 

not to hijack your thread, but i would like to know...

1) the timing in degrees of a stock HO

2) the timing in degrees of a HO with a timing box

3) comparison to a 12 valve with advanced timing to see where HO sits (i dont see this as apples and oranges, just how early the fuel comes in)

there is a lot of talk about this issue, but i never see evidence through numbers. not that i dont want to believe others just that i want to see something back it up.

any truck can blow head gaskets, obviously, and since the HO begins with higher compression ratio it is more at risk with timing enhanced boxes, but is it necessarily too much timing??? i dont know.

i had no problems to speak of with my old truck, but i did not tow heavy.


Pat

 

if the map sensor is towards the back and below the fuel filter on my '02 it is a flat, greyish plug. It is frustrating not having the right parts.

 

Edge comp on a 2002 HO hybrid turbo 60mm/ 14WG and 275 injectors hauling 20-30k lbs for 140k miles for a lumber company not mine but i watched it closely never a hg failure

 

Yep, most HOs don't have a problem, but there have been a few blown head gaskets and a few instances of toasting a cylinder (usually #6). I'd be interested in knowing how much the EZ advances the timing myself, but you can certainly hear the advance in the form of "timing rattle" with the EZ plugged in.

Rusty

 

These instances of damage probably can't be directly attributed to timing advance.

While the EZ adds timing (which you can hear), the stock HO timing curve is less aggressive than the SO (or so I am told by some VERY knowledgeable folks), so it gives you a little more margin.

Effective timing of the HO/EZ combo is probably a little less overall than a similar SO/EZ combo.

jlh

 

Justin,

With all respect, I think we have to look at the whole picture - that is, timing, compression ratio, boost levels, combustion chamber shapes, pump injection curves, etc., all of which add up to peak firing pressure and peak firing temperature differences between the SO and HO.

I don't think anyone is making the case that an EZ by itself will grenade an HO. Rather, what I'm saying is that timing advance is just one more factor in the whole picture that increases internal stresses, especially in heavy towing applications. If the HO is closer to the limit than the SO in stock form, then a timing box in conjunction with other factors could be enough to push it over the limit in extreme applications.

As my dear old dad used to say, "Son, be extremely careful in saying always and never." I wouldn't ever say that a timing box always results in problems with an HO, but I would be just as reluctant to say (especially based on rare examples seen in these forums over the last 5-6 years) that a timing box never results in problems with an HO.

Rusty

 

I had the ez box on last summer, but when winter came around it was very had on the timeing side when it was cold. When the engine warmed up to operating temp. it was fine. With no way to turn it off untill it hit op. temp. I exchanged it for a comp box (and taped the wire) I find it much more manageable............ and more fun

 

Agreed. Note the absence of those two words in my post You guys are keeping me more on my toes.

I'd also go so far as to say that timing has more effect than anything else upon peak cyl pressure and piston crown temps.

Certainly, all the factor you listed are considerations when it comes to keeping the engine within its limits, but I submit that you have to be the MOST careful with timing.

As they say... Timing is everything

justin