Is it common for AFR's to go leaner as new apex seals seat.
02-21-17, 09:58 AM
#1
Is it common for AFR's to go leaner as new apex seals seat.
I rebuilt my motor about a year ago and followed the usual break-in procedure for about 500 miles. The motor now has about 1700miles on it. The car is not driven much, but when driven, it gets a workout at about 25psi(BWS366). I tuned it myself, and find every now and again it gets leaner in the 5000 - 6000rpm range and I have to richen up that area of the map.
Could it be because the apex seals are now seating and the compression is now rising and requiring more fuel?
I log fuel pressure and see no drop over the time.
Has any one had any experience with this?
Could it be because the apex seals are now seating and the compression is now rising and requiring more fuel?
I log fuel pressure and see no drop over the time.
Has any one had any experience with this?
02-21-17, 01:50 PM
#3
Come to think of it, I've had to add fuel to the idle cells. I usually tune idle at the very leanest possible afr , just before where the motor will begin to attempt to stall. Did'nt think anything of it since it would only stall after everything was heat soaked after along drive and I thought it was associated with the fuel compensation map.
02-21-17, 03:33 PM
#4
Racing Rotary Since 1983
iTrader: (6)
"it gets leaner in the 5000 - 6000rpm range and I have to richen up that area of the map"
it is interesting that you mention 5-6 K as it is around peak torque depending on the ports.
peak torque is peak airflow and therefore is peak fuel
if this specific area requires more attention than higher or lower i wouldn't be surprised that it could be at least partially related to the important marrying process between the apex seal and housing.
my personal motor gained 16% compression over 4 years so the seal of our motors is a dynamic process.
i bet your S366 at 25 PSI is a hold-on ride
Howard
it is interesting that you mention 5-6 K as it is around peak torque depending on the ports.
peak torque is peak airflow and therefore is peak fuel
if this specific area requires more attention than higher or lower i wouldn't be surprised that it could be at least partially related to the important marrying process between the apex seal and housing.
my personal motor gained 16% compression over 4 years so the seal of our motors is a dynamic process.
i bet your S366 at 25 PSI is a hold-on ride
Howard
02-21-17, 04:57 PM
#5
"it gets leaner in the 5000 - 6000rpm range and I have to richen up that area of the map"
it is interesting that you mention 5-6 K as it is around peak torque depending on the ports.
peak torque is peak airflow and therefore is peak fuel
if this specific area requires more attention than higher or lower i wouldn't be surprised that it could be at least partially related to the important marrying process between the apex seal and housing.
my personal motor gained 16% compression over 4 years so the seal of our motors is a dynamic process.
i bet your S366 at 25 PSI is a hold-on ride
Howard
it is interesting that you mention 5-6 K as it is around peak torque depending on the ports.
peak torque is peak airflow and therefore is peak fuel
if this specific area requires more attention than higher or lower i wouldn't be surprised that it could be at least partially related to the important marrying process between the apex seal and housing.
my personal motor gained 16% compression over 4 years so the seal of our motors is a dynamic process.
i bet your S366 at 25 PSI is a hold-on ride
Howard
'Hold on ride' Oh yea It was scary at first. I used to be very nervous when taking it out, but over time I got used to the power and now it doesn't seem so scary fast anymore.
02-21-17, 07:50 PM
#6
Old [Sch|F]ool
Did you clearance the apex seals before installing?
I have never once seen compression get better. Every rebuild I have done had its best compression when first run.
I have never once seen compression get better. Every rebuild I have done had its best compression when first run.
Trending Topics
02-22-17, 08:06 AM
#8
Racing Rotary Since 1983
iTrader: (6)
"Did you clearance the apex seals before installing?
I have never once seen compression get better. Every rebuild I have done had its best compression when first run."
my experience has been different. perhaps it is due to most of my motors have honed contact surfaces. yes to clearanced.
jetlude, what was the nature of your build rotor housings (new, used, re-honed) and what apex seal and premix?
H
I have never once seen compression get better. Every rebuild I have done had its best compression when first run."
my experience has been different. perhaps it is due to most of my motors have honed contact surfaces. yes to clearanced.
jetlude, what was the nature of your build rotor housings (new, used, re-honed) and what apex seal and premix?
H
02-22-17, 06:02 PM
#12
Old [Sch|F]ool
I mean the apex seal length clearancing... I have the exact spec written down somewhere, but I'd like to say that I use .004" as the difference between apex seal length and rotor housing width with Atkins seals. I've never had Atkins seals that didn't need significant shortening to get in spec.
I, too, hone my rotor housings. Manually. I have enough stuff kicking around that I can probably make a rig to do it automatically, along with a lapping rig.
I, too, hone my rotor housings. Manually. I have enough stuff kicking around that I can probably make a rig to do it automatically, along with a lapping rig.
02-24-17, 07:46 AM
#13
I mean the apex seal length clearancing... I have the exact spec written down somewhere, but I'd like to say that I use .004" as the difference between apex seal length and rotor housing width with Atkins seals. I've never had Atkins seals that didn't need significant shortening to get in spec.
I, too, hone my rotor housings. Manually. I have enough stuff kicking around that I can probably make a rig to do it automatically, along with a lapping rig.
I, too, hone my rotor housings. Manually. I have enough stuff kicking around that I can probably make a rig to do it automatically, along with a lapping rig.
03-03-17, 08:25 AM
#16
"Elusive, not deceptive!”
I rebuilt my motor about a year ago and followed the usual break-in procedure for about 500 miles. The motor now has about 1700miles on it. The car is not driven much, but when driven, it gets a workout at about 25psi(BWS366). I tuned it myself, and find every now and again it gets leaner in the 5000 - 6000rpm range and I have to richen up that area of the map. Could it be because the apex seals are now seating and the compression is now rising and requiring more fuel? I log fuel pressure and see no drop over the time. Has any one had any experience with this?
On aspect to consider is weak ignition... You are at high load on that system and if it is going to misfire this is usually where it starts.
When it misfires the AFR increases from unburned fuel... And unused oxygen.
Barry