LB7 to LLY: timing differences?

[Whitetail Addict]

Is there a difference in timing from and LLY to an LB7? Will an LLY react differently from the same timing tables used in an LB7? A buddy of mine was troubleshooting one of my tunes in his LLY and he said it had bad timing rattle and it didn't in my LB7.

 

[The Neens]

I just compared the tables in our '02 and '05, pretty darn similar...Neither truck rattles, so I never had to do any fine tuning...

 

[Whitetail Addict]

Thanks Chris....The LLY has an aftermarket charger, would that have something to do with it?

 

[The Neens]

A buddy of mine was troubleshooting one of my tunes in his LLY and he said it had bad timing rattle and it didn't in my LB7.

The LLY has an aftermarket charger, would that have something to do with it?

Quite possible, now we're comparing apples to oranges to lemons

 

[The Neens]

Send the tune and I'll take a look...

 

[JOHNBOY]

Is there a difference in timing from and LLY to an LB7? Will an LLY react differently from the same timing tables used in an LB7? A buddy of mine was troubleshooting one of my tunes in his LLY and he said it had bad timing rattle and it didn't in my LB7.

I have seen this in LB7s. Same tune exact same mods. trucks act different. One rattles, one does not, one dynos way better. What I have found is we are assuming that TDC in are motor is where the ECM thinks it is. It is not always where the ECM thinks it is. The ECM figures TDC by using a sensor to locate a gap in the reclator wheel. This wheel is a stamping. It is simply bolted to a the waterpump drive gear. The holes have clearence for ease of assembly. The gear is loacated on the crank by one little dowel pin. There is claerence in this fit to. The sensor mounts in the cast front cover. It is located by pins and bolted to the block. The block is just a casting and both peices are machined to tolerances. Moral of the story is there can be a fair bit of difference between TDC assumed and TDC actual.

What I did on the above mentioned low performing, rattling LB7 was to simply subract 3* form all three tables. Rattle went away truck ran much better.

Thanks Chris....The LLY has an aftermarket charger, would that have something to do with it?

Yes it can. The reason being that until a bigger charger starts to come on it can be moving less air then the faster spooling stocker. Logging the MAF of both trucks will show you this. Bigger turbos typicaly need less timing until they start to spool.

 

[Fingers]

I have seen up to 6* variation in TDC timing from one motor to the next using the chamber pressure monitor.

Things that make you go hmmmmmm.

 

[Whitetail Addict]

Wow. Thanks for the input guys, I'm learning alot in this thread.

Johnboy, very interesting facts. I never would have considered the TDC factor.
What you explain after the second paragraph about the affects of the aftermarket charger, that sounds like what my buddy was experiencing with his truck. He said it would be at about 70, stand in it, and it would rattle until the charger lit.

Chris, thanks for the offer. I don't plan on running that tune again until spring due to the weather, so its not a big priority, but I will send it to you before I run it.

 

[Bluemax]

I have seen this in LB7s. Same tune exact same mods. trucks act different. One rattles, one does not, one dynos way better. What I have found is we are assuming that TDC in are motor is where the ECM thinks it is. It is not always where the ECM thinks it is. The ECM figures TDC by using a sensor to locate a gap in the reclator wheel. This wheel is a stamping. It is simply bolted to a the waterpump drive gear. The holes have clearence for ease of assembly. The gear is loacated on the crank by one little dowel pin. There is claerence in this fit to. The sensor mounts in the cast front cover. It is located by pins and bolted to the block. The block is just a casting and both peices are machined to tolerances. Moral of the story is there can be a fair bit of difference between TDC assumed and TDC actual.

So would it be worth it to check the alignment of the reluctor wheel and sensor while a motor is apart and make any corrections to them, or easier to tune around and not worry about it?

 

[Fingers]

Most people are not set up to check the reluctor timing, but there are shims to allow you to shift the pick-up sensor. Personally, I would just take note of what the error is and tune around it.