17 A/F after new tune for Comp Cams??
08-09-2014, 06:26 PM
#1
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17 A/F after new tune for Comp Cams??
Hey Guys,
Just had my FRPP intake manifold installed as well as my 127200 Comp Cams.
First drive, i notice an air sucking sound from mild to hard throttle, from what i assume to be because of the intake manifold. Heard this was common?
Also, the car idle's fine, when driving normally the car's a/f is anywhere from 14 to 15.5.
At harder acceleration i see 13's..
However when i let off the throttle, the a/f sometimes goes all the way up to ~17 where it sounds like the engine wants to die. At idle is stays aroudn 14-15.
My tune is for the cams and purchased at Brenspeed. Will contact them on monday.
But can i drive the car like this? Also is there a break in procedure for the cams?
Just had my FRPP intake manifold installed as well as my 127200 Comp Cams.
First drive, i notice an air sucking sound from mild to hard throttle, from what i assume to be because of the intake manifold. Heard this was common?
Also, the car idle's fine, when driving normally the car's a/f is anywhere from 14 to 15.5.
At harder acceleration i see 13's..
However when i let off the throttle, the a/f sometimes goes all the way up to ~17 where it sounds like the engine wants to die. At idle is stays aroudn 14-15.
My tune is for the cams and purchased at Brenspeed. Will contact them on monday.
But can i drive the car like this? Also is there a break in procedure for the cams?
08-12-2014, 11:12 AM
#5
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Been driving it for 5 days now.
The A/F spikes to about 20! when i let off the gas.
Feels like the cars wants to die when it goes above 17..
I've emailed brenspeed, they got back to me saying that they only adjust fuel at WOT in their tune. The rest is set by the engine computer.
I'm also seeing some difference between the leftbank and rightbank's A/F...
Both go nuts when i let off the gas, but durinng etc it seems that the left bank is usually running "richer" than the right bank. (14.2 /\ 15.2 )
Would like to get some input from some cam guys..
The A/F spikes to about 20! when i let off the gas.
Feels like the cars wants to die when it goes above 17..
I've emailed brenspeed, they got back to me saying that they only adjust fuel at WOT in their tune. The rest is set by the engine computer.
I'm also seeing some difference between the leftbank and rightbank's A/F...
Both go nuts when i let off the gas, but durinng etc it seems that the left bank is usually running "richer" than the right bank. (14.2 /\ 15.2 )
Would like to get some input from some cam guys..
Last edited by Mellowdien; 08-12-2014 at 09:28 PM.
08-14-2014, 12:29 AM
#6
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It's the tune and not the cams. There is a part of the tune called the "dash-pot"? I probably spelled it wrong. It adjusts off throttle fuel and can be used to compensate for a hanging idle or problem like you have. Under idle or off throttle I wouldn't be concerned unless the car drives bad.
For them to say they do not adjust for WOT doesn't sound right. Part of the reason for tuning for cams is to make drivability good.
For them to say they do not adjust for WOT doesn't sound right. Part of the reason for tuning for cams is to make drivability good.
08-15-2014, 08:40 AM
#7
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There are parameters in the tune that control when the fuel injectors shut off when coasting, which I believe Brent (and alot of other tuners too apparently) doesn't mess with and leaves stock. With stock cams there is a tiny lean spike when getting off throttle, cams just multiply that spike. I have the same problem you do. Although it feels and sounds horrible, it won't hurt anything, and the car is still driveable. (you can blip the throttle and the AFR will come down). But yes - I hate it and want it gone. I have the SCT PRP and am going to attempt to tune out or minimize the issue.
At idle and cruise the ideal AFR is 14.7 (aka stoich) if the WB is set for straight pump gas (or 1.00 lambda). WB's actually measure in lambda - so even if it is set for straight gas and you put E85 or something else in the tank, the WB will show the ideal stoich point as 14.7 AFR (even though it is actually a completely different number - WB controllers can be reprogrammed to show the real number though). The AFR on the WB will swing back and forth to either side of that during closed loop because of the O2's continually adding and removing fuel. You will never see a WB stay at a solid 14.7. At start and WOT the engine goes from closed loop to open loop and uses the AFR target point set in the tune by the tuner. The ideal WOT AFR (most power) is different for every engine. Theoretically, a rule of thumb for ideal (safe) WOT for an NA engine is 12.5, and for boosted around 11.0-11.5.
At idle and cruise the ideal AFR is 14.7 (aka stoich) if the WB is set for straight pump gas (or 1.00 lambda). WB's actually measure in lambda - so even if it is set for straight gas and you put E85 or something else in the tank, the WB will show the ideal stoich point as 14.7 AFR (even though it is actually a completely different number - WB controllers can be reprogrammed to show the real number though). The AFR on the WB will swing back and forth to either side of that during closed loop because of the O2's continually adding and removing fuel. You will never see a WB stay at a solid 14.7. At start and WOT the engine goes from closed loop to open loop and uses the AFR target point set in the tune by the tuner. The ideal WOT AFR (most power) is different for every engine. Theoretically, a rule of thumb for ideal (safe) WOT for an NA engine is 12.5, and for boosted around 11.0-11.5.
Last edited by jpplaw; 08-15-2014 at 08:59 AM.
08-21-2014, 03:16 PM
#8
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@JPPLAW, at WOT, the AF is around 12.7
Started a new thread at the strip section.
Went there, ended up being slower than before the cams and intake.
12.8 was my best,... 12.9 my most consistent... (before)
(now) 13.1 my best... and 13.3 my most consistent..
Super frustrated about it.
Started a new thread at the strip section.
Went there, ended up being slower than before the cams and intake.
12.8 was my best,... 12.9 my most consistent... (before)
(now) 13.1 my best... and 13.3 my most consistent..
Super frustrated about it.
08-22-2014, 10:21 AM
#10
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Location: Redding, CA
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If your car is slower after all the new mods and tuning, then check to make sure everything is mechanically correct. Then I would lean towards tuning. This is why I use a shop very experienced with our cars.
Just a slight leak between the MAF and the manifold can cause an issue. Sorry I can't be more help but I have gone through things like this and sometimes it's taken a few months to figure it out. Or, find a good shop and pay the piper.
Just a slight leak between the MAF and the manifold can cause an issue. Sorry I can't be more help but I have gone through things like this and sometimes it's taken a few months to figure it out. Or, find a good shop and pay the piper.
