Reported Timing Discrepancy
Thread Starter
Pro
Joined: Jan 2005
Posts: 686
Likes: 62
From: San Jose Ca
Reported Timing Discrepancy
I've been doing some dataloging and tuning on my dads '90 and noticed that there is approx a five degree discrepancy between whats in the various tables and what is reported by Datamaster at any given point. For example, at 5500rpm, 100kpa, the timing table commands 28.8 degrees, but datamaster reports 22-23 at the same conditions. It even does this with the closed throttle spark advance. Set it to 20 and you get approx 15. In other words, everything seems to be retarded 5 degrees from whats commanded. This isn't due to knock retard, as there is none of that going on, and a Tech 1a reports the same as Datamaster. In my experience with my '94 LT1, it actually went the other way. Whats reported by a scan tool (or datamaster) is approx 4 degrees more than whats commanded. Popular opinion in the LT1 scenario is that there is an unknown table thats adding the timing. Is this the case with the LT5 as well?? Which do I believe, what I'm commanding or whats reported. If I go by what's reported, I'm leaving alot of performance on the table. Does anybody have and explanation for this????
Thanks
Scott
Thanks
Scott
Instructor
Joined: Jun 2000
Posts: 121
Likes: 0
From: Decatur Indiana
ZR1 Spark
Scott,
There is a 6 degree, advance, offset in the LT5. This is taken into account in the calibration, the base offset is a calibratable value at address 1B in the cal. The scan tool does not reference this offset.
Graham
There is a 6 degree, advance, offset in the LT5. This is taken into account in the calibration, the base offset is a calibratable value at address 1B in the cal. The scan tool does not reference this offset.
Graham
1st Gear
Joined: Dec 2007
Posts: 1
Likes: 0
I've been doing some dataloging and tuning on my dads '90 and noticed that there is approx a five degree discrepancy between whats in the various tables and what is reported by Datamaster at any given point. For example, at 5500rpm, 100kpa, the timing table commands 28.8 degrees, but datamaster reports 22-23 at the same conditions. It even does this with the closed throttle spark advance. Set it to 20 and you get approx 15. In other words, everything seems to be retarded 5 degrees from whats commanded. This isn't due to knock retard, as there is none of that going on, and a Tech 1a reports the same as Datamaster. In my experience with my '94 LT1, it actually went the other way. Whats reported by a scan tool (or datamaster) is approx 4 degrees more than whats commanded. Popular opinion in the LT1 scenario is that there is an unknown table thats adding the timing. Is this the case with the LT5 as well?? Which do I believe, what I'm commanding or whats reported. If I go by what's reported, I'm leaving alot of performance on the table. Does anybody have and explanation for this????
Thanks
Scott
Thanks
Scott
visit this site and Zr1 folks going to give you the answers
http://www.zr1netregistry.com/forum/...splay.php?f=14
Le Mans Master
Joined: Jul 2005
Posts: 5,328
Likes: 405
Hello there..
visit this site and Zr1 folks going to give you the answers
http://www.zr1netregistry.com/forum/...splay.php?f=14
visit this site and Zr1 folks going to give you the answers
http://www.zr1netregistry.com/forum/...splay.php?f=14
I agree the registry is a great place, but he won't get a better answer than he already got here.
Thread Starter
Pro
Joined: Jan 2005
Posts: 686
Likes: 62
From: San Jose Ca
Scott
