Hello guys! Maybe some of you guys have read my 750 CFM vs 600 CFM thread. I replaced the 750 CFM Edelbrock 1407 with a 600 CFM Edelbrock 1405. I rejetted the 1405 to the 1406 settings before I even installed it on the Scamp. And with the AEM Wideband, I have tuned it from there. I've got it now the best I've had it yet.
I took it to my 33 mile round trip "mpg test route." It starts out at a gas station in a rural area and drives 16.5 miles further out into the country. I hold it as close to 50 mph as I can hold it. It is very consistent. I drive back to the fuel station and refuel.
On the 750 CFM, the best I managed was 15.0 mpg before I gave up on trying to tune it further. After learning that the difference between the 750 CFM and the 600 CFM was on the primary side only, I decided to go for the 600 CFM. The secondaries are the same. But the venturis and bore of the primaries are a quarter inch smaller on the primaries of the 600 CFM.
Based on the fact that the 600 CFM has more than enough capacity for my LA 360, what motivated me was that I would be able to flow the same volume of air through the primary side, but that same velocity would have to move faster through the smaller area. That increased air velocity (in my mind) should yield better atomization.
And that seems to be the case. The smaller primary side, and tuning, I've got it to 21.6 mpg! And, the car is quicker than it has ever been. It starts up quite easy now (compared to crank up on the 750 CFM).
However, I still have room for improvement. It is too lean on acceleration, and too rich (still) while cruising. I'm running about 15.7 AFR accelerating, and 14.7 AFR cruising.
Over the weekend I purchased 2 more sets of metering rods. I'm going to send both of these off to a machine shop. I'm tuning for 11% more fuel during acceleration, and 5.5% less fuel during cruising. And I'm going to change the step location. I'm going to move the step higher on the rod so the acceleration richening comes on sooner. I'm hoping this will eliminate the 1.5 second lean spike. (1.5 seconds after pulling away from a dead stop). I'm having 2 pairs of metering rods machined (differently) to try in 2 different sizes of main jets.
My current setting only runs about 12.7 AFR at WOT, and I want to bring it to 12.2. But WOT is the last thing I will tune, as it going to get affected by the small end of the metering rod. Since I'm about to richen up my acceleration with the custom metering rods, that will richen my WOT somewhat.
And lastly - I've leaned out my idle from ~13.0 AFR to ~13.5 AFR, thinking it was more conservative / better. But it does not like it. It does sound mean idling and mildly loping, but via the AFR gauge, the loping is actually misfiring. At 13.0 or maybe even a skosh richer, it misfires much less. Idle AFR is simple to set also. So, in the future I'm going to adjust it to where it misfires the least.
Anywho, sorry for the long post, but the tuning of this car has been FUN!
I took it to my 33 mile round trip "mpg test route." It starts out at a gas station in a rural area and drives 16.5 miles further out into the country. I hold it as close to 50 mph as I can hold it. It is very consistent. I drive back to the fuel station and refuel.
On the 750 CFM, the best I managed was 15.0 mpg before I gave up on trying to tune it further. After learning that the difference between the 750 CFM and the 600 CFM was on the primary side only, I decided to go for the 600 CFM. The secondaries are the same. But the venturis and bore of the primaries are a quarter inch smaller on the primaries of the 600 CFM.
Based on the fact that the 600 CFM has more than enough capacity for my LA 360, what motivated me was that I would be able to flow the same volume of air through the primary side, but that same velocity would have to move faster through the smaller area. That increased air velocity (in my mind) should yield better atomization.
And that seems to be the case. The smaller primary side, and tuning, I've got it to 21.6 mpg! And, the car is quicker than it has ever been. It starts up quite easy now (compared to crank up on the 750 CFM).
However, I still have room for improvement. It is too lean on acceleration, and too rich (still) while cruising. I'm running about 15.7 AFR accelerating, and 14.7 AFR cruising.
Over the weekend I purchased 2 more sets of metering rods. I'm going to send both of these off to a machine shop. I'm tuning for 11% more fuel during acceleration, and 5.5% less fuel during cruising. And I'm going to change the step location. I'm going to move the step higher on the rod so the acceleration richening comes on sooner. I'm hoping this will eliminate the 1.5 second lean spike. (1.5 seconds after pulling away from a dead stop). I'm having 2 pairs of metering rods machined (differently) to try in 2 different sizes of main jets.
My current setting only runs about 12.7 AFR at WOT, and I want to bring it to 12.2. But WOT is the last thing I will tune, as it going to get affected by the small end of the metering rod. Since I'm about to richen up my acceleration with the custom metering rods, that will richen my WOT somewhat.
And lastly - I've leaned out my idle from ~13.0 AFR to ~13.5 AFR, thinking it was more conservative / better. But it does not like it. It does sound mean idling and mildly loping, but via the AFR gauge, the loping is actually misfiring. At 13.0 or maybe even a skosh richer, it misfires much less. Idle AFR is simple to set also. So, in the future I'm going to adjust it to where it misfires the least.
Anywho, sorry for the long post, but the tuning of this car has been FUN!
