Discussion in 'High Tech for Old Iron' started by theone61636, Apr 6, 2010.
What is your target AFR at an idle? Have you tried to lean it out yet?
13.5, leaned it out to 14.1 yesterday, haven't check ADL yet. Might have to go even higher with overlap of firstname.lastname@example.org". I have a buddy with a MS set up and similar cam. He is set at over 15:1.
I think I may have a false lean situation as my plugs are fouling quick at idle, even with the idle cell pulling fuel. Exhuast smells slightly rich, though it's hard to tell since it dumps under the car.
Due to the large overlap in the cam, at low rpms there is enough time for unburnt intake charge to enter the cylinder and join the exhaust gas prior to the exhaust valve closing. This will make the O2 sensor read lean sense it only measures oxygen and not fuel. It may be reading 13.5 when I am really 12.1? Messing with things it has had more time at idle than anything else, not much time to clear the plugs with spirited runs.
Would being overly rich cause the initial stall if the throttle is barely touched?
Fouled plugs can cause any number of things. Get it out and clean the plugs.
If I am not entirely correct someone can correct me but a wide band works different than a narrow band. A wide band has two parts, a pump cell and a sensor cell. When on the rich side the pump cell pumps air into the sensor to bring it to stoic and on the lean side it pump air out of the sensor to get it to stoic. It measures the amount the pump cell works one way or the other to determine your AFR. A wide band can be fooled by a bad running engine producing some types of gasses. I think excess CO can cause a sensor to read as lean.
The factory ADL min/max is 25%, so it may not lean out much more. You could go in and up that for testing.
Yup. One of my customers iinstalled the fuel pressure sensor there to be used with the Fuel On Demand (FOD)
Your tires will melt before the PIII does. :Brow: You'll be fine. Everything is tested from -40 to 400
I changed EMS's many times through updates, but Daily drove my car for five years with "RetroTek Inside" under the hood and NEVER had to be towed home. I had 250+ hrs on one Stage III EMS...
You will need 2 profile if you want to run that rich.
Target AFR would need to be the same with and without nitrous; or the ECU will pull fuel like you suggested
It is as accurate as a OEM, They spent the +3K and checked it. I was adamant on that.
Your buddy with the MS has the right idea. You need to shoot for an overly lean target AFR at idle because of the overlap in the cam
I dont have the engergy to think this one out and brush up on my 5 gas haha, In the morning.... Also I have a new Super Calc for you guys... It already got deleted from the Pro Products forum.... Not a great start :rant:
When is the new forum starting up for the Powerjection users?
I will find out why this happened. Other than it did not close with Excel 07.
I am have been busy and not at my desk lately to work on the forum so I have handed it over to another one of the techs. I ask him daily and i still get the its not quite finished answer. Do you care if you have to read pink text? haha.
As soon as the forum is ready I will post the link here. If it is Friday and it is still not complete I will still post it. We need to get the show on the road!
I maybe missing something but with a carb, big cam, low vac and lots or intake reversion you end up needing a richer idle. You can run it leaner but it won't have enough power to get out of it's own way. Most times the exhaust goes into the intake as opposed to the intake charge going into the exhaust. The pressure in the cylinder is higher than the pressure in the intake during the valve overlap period. Ever see a carb that is black in the venturis, that's why.
A carb and high overlap cam relies on vacuum to pull fuel in at idle. Since it's low with a high duration cam you have to richen up the idle or shut down the low speed air bleeds just to get fuel into the cylinders at low speed.
With EFI and a high overlap cam, the dilution causes erratic sensor data and like Cody said can lead to rich mixtures being read as lean. This is why cams ground for EFI typically have fairly wide separation angles....it is typically geared more towards low speed tuning compensation. It's also why the PJ-III has the option to set a fixed pulsewidth idle instead of using the idle cell if necessary.
Personally I run a single pattern 224/224 108 LSA cam on a 400 with AFR-195 heads. It makes 14-15" of vacuum at idle, my low speed fueling is at 57 on the fuel wizard, and the system still pulls fuel in the idle ADL table with a 14.6 target so personally I don't seem to have an issue. The cam and heads are on the small side if this were an all out 400ci engine; however, the engine was built to run a 0.64 OD trans with a 3.42 rear at low speeds which it does very nicely while still cracking 500hp and being able to pull over 6000 RPM with just 30 degrees of total timing. The EFI helps the low speed and the good heads help the high speed. Number one though is having a builder that listens to your setup and how you want to drive the car.
As for the question about the AFR accuracy, I can back Cody up. The place I did my dyno at uses one of the wideband systems that OEM's use for development. The system alone costs more than a couple of PJ-III's and just the sensor costs more than a good wideband logging system. It read right with my logs during my five runs.
I was thinking carb still and started out with 12.5 idle, then 13.1, then 13.5...
I will try 14.7 this weekend or even higher until I get better plug readings. It shoudl also not idle as much since it's drivable now. Hopefully the leaner idle will help with the initial tip in hesitation. Pretty embarrassing to stall at a stop sign.
Dr. EFI, The multi quote button is second from the right, quit trying to pad your post count.
:TU: Perfectly done. Yes the wideband in the Powerjection III was calibrated with a Boush calibrator system. From what I understand it is used to calibrate the machines used to calibrate the manufactured sensors.
Call Tech Support!
Oops! Didn't even think of that! o No: :moonu: