Air/Fuel Testing
Thread Starter
Instructor
Joined: Jan 2007
Posts: 233
Likes: 41
From: Simpsonville SC
Air/Fuel Testing
I’m borrowing a buddy’s Dynojet Wideband Commander A/F meter. http://www.widebandcommander.com/ I was looking around on the forum at various posts on the subject and noticed most referred to a write up done by Matt Gruber @ http://community.webtv.net/MATTGRU/AFtesting but I can’t find it. The links dead. Does anyone have this write up?
I want to have a good understanding of the ideal idle/cruse/wot A/F ranges before I start. I’m working with a stock 78 L-82. I would like to get some final tuning results from others who have done this before using an LM-1 or something similar.
I want to have a good understanding of the ideal idle/cruse/wot A/F ranges before I start. I’m working with a stock 78 L-82. I would like to get some final tuning results from others who have done this before using an LM-1 or something similar.
Thread Starter
Instructor
Joined: Jan 2007
Posts: 233
Likes: 41
From: Simpsonville SC
Here’s my AF testing result charts using the Wideband commander. I made a few runs down the interstate and logged the results (A/F and RPM). Use the "zoom" to see the charts better.
The first run is with my secondarys locked out so I could verify my primary jetting. http://picasaweb.google.com/Walllpar...39851846575410
Second is a normal run with the secondaries unlocked. http://picasaweb.google.com/Walllpar...39860436510018
Third is a sample cruse log at 70mph. http://picasaweb.google.com/Walllpar...39869026444626
I think I’m good. What do you guys think?
The first run is with my secondarys locked out so I could verify my primary jetting. http://picasaweb.google.com/Walllpar...39851846575410
Second is a normal run with the secondaries unlocked. http://picasaweb.google.com/Walllpar...39860436510018
Third is a sample cruse log at 70mph. http://picasaweb.google.com/Walllpar...39869026444626
I think I’m good. What do you guys think?
Thread Starter
Instructor
Joined: Jan 2007
Posts: 233
Likes: 41
From: Simpsonville SC
Thanks for the feedback. I’m pleased with everything except my idle. Wouldn’t you want your idle to be as close to 14.7:1 as possible? When I adjust the idle mixture screws to achieve this, I start getting the “lean” smell. It’s not bad but I thought 14.7:1 was the cleanest burning mixture? I had it set at 13.5-13.8 like BigBlockk suggested and the smell was not as bad. The car idles fine at ether setting just would like to get rid on the smell.
Race Director
Joined: Sep 1999
Posts: 11,361
Likes: 383
From: Plano TX
22 degrees might explain the smell. Try disconnecting the vacuum and see if the smell goes away.
BTW, the 78 did not have idle vacuum advance from the factory for emission reasons. If you still have the stock cam you could run ported vacuum.
BTW, the 78 did not have idle vacuum advance from the factory for emission reasons. If you still have the stock cam you could run ported vacuum.
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Thread Starter
Instructor
Joined: Jan 2007
Posts: 233
Likes: 41
From: Simpsonville SC
Yep, still got the stock cam. The only changes from stock I have done is removed the A.I.R system and CAT. I think you might be on to something though. I have always questioned the vac. advance specs for the 78 L-82 because the manuals I have don't say anything about it. Here's a post I had a while back on the subject. http://forums.corvetteforum.com/show....php?t=1779460
. I'm going to set my idle back to 13-13.5:1 and double check my vac. advance.