timing belt wrap

[ThunderChild]

just wondering, are there any articles pertaining to timing belt wrap for the 4g63/64? ive looked and cant find anything on it.

just wondering if anyone has looked at the lack of wrap on the crankshaft pulley, compared to other engines. im wondering if theres a correlation to the higher propensity for timing belt skipping due to that.

just a thought, wondering if anyone has anymore info. i have the gates timing belt pdf and have read a few other general papers on the subject, but nothing definitive has come through.

 

[bling5tatus]

I have never heard of timing belt wrap. Do you have more information on this that we can read elsewhere?

 

[Mauispyder]

VFAQ has pictures, and I also used a version by Kim Steele for guidance but I don't know of any articles specific to "wrap".

 

[tmoney20g]

I think he means wrap angle. Where if you look at an installed t-belt on a 4g63 crank pulley, which has 24 teeth. Figure each tooth represents 15 degrees. The belt is only forcibly touching, let's say, 10 teeth, so the wrap angle for us is 150 degrees. I think ideal wrap angle is 180 degrees or more, so I see his concern, but there's nothing we can really do about it.

 

[turtlebain]

If you are referring to actually "wrapping" the belt around the gears, I took some pictures and was going to make a write up on installing the belt easily. I struggled until I found a couple of tricks that got me by. You don't need a gear holder tool, but you will need a couple zip ties and 2 wrenches to hold the gears in place while you "wrap" the belt around.

There's vfaq yes but most of those pictures are old and hard to see what's going on I used a combination of Vfaq, and other articles, youtube clips:

DSM Graveyard 4g63 Timing Belt Tutorial - YouTube
Pictorial: Installing/Timing a timing belt (6bolt/2g) | DSMtuners

And of course the bible.

 

[GRAVEDIGGER]

These engines have proven themselves time and time again regardless of "belt wrap", "wrap angle", or whatever you wanna call it. If the timing belt, the tensioner, and rollers are replaced at the scheduled interval and the belt tension is set up properly there is no need to worry IMHO.

 

[ThunderChild]

I think he means wrap angle.

This. I'm referring to the amount of wrap the belt has on the lower crank pulley, sorry should have been more clear.

Under normal driving, even some rough conditions, I'd say it's not a problem. I'm talking about those harsher and more extreme cases where a belt skips.

Could it skip from knock, misfire, pre-ign Etc? Maybe yea. Could it possibly be prevented if there were more total wrap on the t-belt? I think so, and I think it'd save alot of cylinder heads as well.

Idk if there's a longer belt out there that could be used in conjunction with another idler pulley. I'd like to see if it would be possible, given the space and belt length, but it would take some r&d.

 

[GRAVEDIGGER]

Under normal driving, even some rough conditions, I'd say it's not a problem. I'm talking about those harsher and more extreme cases where a belt skips.

Could it skip from knock, misfire, pre-ign Etc? Maybe yea. Could it possibly be prevented if there were more total wrap on the t-belt? I think so, and I think it'd save alot of cylinder heads as well.

Idk if there's a longer belt out there that could be used in conjunction with another idler pulley. I'd like to see if it would be possible, given the space and belt length, but it would take some r&d.

These cylinder heads you speak of saving could have been saved from proper routine maintenance, that's all there is to it. Timing belts don't skip a tooth, or two from knock, misfiring, or preignition. They skip teeth from being worn out, having improper tension, have failing tensioners etc.

Again, these engines have proven themselves to be just fine the way they are already set up with proper maintenance. There is no need to re-engineer the timing belt system...

 

[turtlebain]

150 deg. vs 180??

I highly doubt this is having any effect. I think you'll find that people that use the correct tensions and procedures, replacing auto-tensioner when out of spec, and other components when necessary aren't having any issues with skipping. If you're really concerned about it though, there's a difference between the 1g and 2g tensioner arms. One you torque clockwise and one counter. That could give you an additional couple degrees.

 

[turtlebain]

To add to the above (reading some of the other responses) I believe the amount of wrap angle to have nothing at all to do with belts skipping. That comes from worn or improperly tensioned belts. I don't think they would skip even if coming in contact with just 2 teeth.

But if it was you'd be putting all that torque on 2 teeth perhaps causing the teeth to be chewed right off the belt.. That is the only problem with wrap angle. The 150 deg. or so allows about 10 teeth to come in contact with the crank sprocket ... You don't see any teeth being ripped out by DSMers so I'd call that sufficient.