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Truck Avenger 670 AFR Tuning

rcamacho

rcamacho

1/2 ton status
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Well I finally got around to installing a Truck Avenger 670 carburetor in lieu of my modified 780CFM Holley 3310-1 after coming to the conclusion that the latter was too large for my 402BBC intended usage. I'm happy to report the difference in throttle response is astounding on the primary side even though the 3310 pump was tuned. The AFR checks out well on my wide-band rig and is more stable to boot. The TA is in stock calibration other than a blue pump cam. The shooter size does not appear to need any changes just yet. Secondary actuation was a bit late with the plain spring so I'm trying the purple spring next.
 
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Well the wideband rig seems to have paid off.
The hole between primary and secondary (2000-3000RPM) was due to a lean WOT AFR on the primary. The TA670 primary calibration is way off for my application and some serious adjustment to the main/PVCR relationship was needed. Still working on the primary and have the main jets way up to cover the WOT lean condition.
http://www.innovatemotorsports.com/forums/showthread.php?p=70253#post70253
 
rcamacho said:
Well the wideband rig seems to have paid off.
The hole between primary and secondary (2000-3000RPM) was due to a lean WOT AFR on the primary. The TA670 primary calibration is way off for my application and some serious adjustment to the main/PVCR relationship was needed. Still working on the primary and have the main jets way up to cover the WOT lean condition.
http://www.innovatemotorsports.com/forums/showthread.php?p=70253#post70253
Click to expand...


Good luck, I hope it works for you. I love Holleys but I don't like the truck avenger after trying it. There are no high speed air bleeds (at all, they were never even drilled as part of the check valve system to keep it idling on inclines) which throws your fuel curve off, so if you tune it for one scenario (RPM/throttle) it will be off at a different one. But it will still idle on steep inclines. Unless you are doing low speed rock crawling, I would put the 3310 back on there.
 
Thanks folkenheath, I'm aware of the fuel curve issues due to the lack of bleeds/emulsion on the main circuit. I'll see what I can do with the PVCR/main jet adjustments to at least avoid catastrophic lean conditions and see how far it goes. I may well go back to the 3310-1 but am really enjoying the better primary response of the smaller carburetor.
 
Keep us posted how it turns out, I'm curious how the fuel curve looks through the RPM range at WOT once you get the PVCR channels tuned for proper cruising/WOT. Do you have your wideband linked to an RPM input too or just the A/F ratio?
 
I'll start logging the LC1 rig after I get the PVCR spot on to go back to #68 mains. My rig is set up for AFR only, no RPM or Hg feed yet. For the $ I may just borrow/purchase an LM2 rig.
 
Interesting tech note, some TA carburetor metering blocks had the check valves upside down which would impact main circuit fuel delivery. I'll be checking my blocks next time I have it apart.
 
rcamacho said:
Interesting tech note, some TA carburetor metering blocks had the check valves upside down which would impact main circuit fuel delivery. I'll be checking my blocks next time I have it apart.
Click to expand...

subscribed....

ill have to check mine out once she is running again... no 12v anywhere right now.. oh wait you need wires for that right... :crazy:
 
Still working on logs.
For now I've re-enabled the secondaries. Primary AFR ranges from 16:1 to 12.5:1 with secondaries coming in at 3000 RPM. The AFR does not go lean with the secondaries enabled so I presume the airflow does not break down due to velocity issues when the secondaries can split airflow. Additionally, the secondary jets are massive so it may just be covering up a lean high speed calibration on the primary.
 
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