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Old 11-18-2007, 01:10 AM   #1
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Default AFR Bouncing on Wide Band

We went out tuning the mspnp on the 1.6l greddy for the first time. We set EGO % to 0 because we did not have narrow band hooked up. We also changed the open loop control on the kPa to 10 so it would run open loop for anything greater than that volume, as we did not want closed loop at all. Then we put the idle control on PWN Warm up only. Then we started playing with the fuel table to get the afr's to where they should be. At a steady cruise, not moving the gas pedal, the afr's would sometimes stay consistant, say at 14.0 and all off a sudden jump to 11.0 or 10.0. I do not understand why it would behave like this. The map is pretty smooth and it stays in one cell, at one number, but the duty cycle gauge in the Megatune would also be steady and then jump once in a while as well. So I cannot get a steady tune. I dont know if this has anything to do with my TPS problem that I have posted about in another thread or if this has something to do with some other setting. Any help is greatly appreciated. Thank you in advanced.
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Old 11-18-2007, 04:52 PM   #2
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fix the TPS problem first... this is probably acceleration enrichment kicking in when your TPS blinks. How is your rpm signal? If it drops off for a split second the MS might be going rich to prevent a stall, even if the engine isn't really dropping down.
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Old 11-18-2007, 08:32 PM   #3
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RPM signal stays solid. Remember, this is when I am cruising at 3000 rpm. The AFR will hold at 14-15 then go rich to like 10 for a split second. You can also feel a slight hesitation in the car when it does this. Is this related to an issue the stock TPS? Before I installed MSPNP, I had no issues at all with the TPS.
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Old 11-18-2007, 08:47 PM   #4
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Make sure you're using mapdot and not TPSdot.
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Old 11-18-2007, 08:55 PM   #5
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turn the acceleration threshold to 255 (off) to see if it's the problem.

If so, you should move the location of your MAP sensor line to the line off the FPR and maybe install an inline filter.
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Old 11-18-2007, 11:33 PM   #6
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^^^Braineack thank you! I think this may have fixed it. I changed it to 255and went for a test drive. I was not able to recreate the symptoms, however my laptop died and I could not see AFR's, so I am charging it right now to so I can go for another test drive just to make sure. My MAP sensor line is running off of the cruise control nipple and directly to the MSPNP (My car does not have cruise control). It is a direct route, with nothing else spliced into it. For a FPR I am running the Vortech FMU, but with a 3:1 recalibration disk. Do you think it would better for me to run the map off of this vacuum line? Also, do you think because I am running the FMU with a 3:1 disk is the underlying cause of my problems? Thank you very much again. Your input is greatly appreciated!
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Old 11-18-2007, 11:53 PM   #7
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First of all, you don't really want to run the FMU with megsquirt though it can be done, it's not ideal. You're better off running appropriate sized injectors with the stock fuel system. You can still tune the fuel with the FMU included as well though.
As for the vacuum line, the cruise control nipple on the front of the manifold near the throttle body has been known to be a "noisy" signal. Moving your vacuum signal to the FPR line or another fitting near the rear of the manifold is a more stable "clean" signal that will alleviate some issues you might have when trying to tune the accel enrichments that you've turned off.
When tuning your fuel map manually you want to turn off your enrichments so that you know they're not modifying your AFRs while driving.
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Old 11-19-2007, 12:08 AM   #8
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Gotcha. I am however not running stock fuel system. I have a walbro 255 fuel pump, the 3:1 FMU, rx7 red top 460cc injectors. I did not know that the cruise control provides a noisy signal. Tommorrow I am going to reroute all of my vacuum connections. So an ideal splice for the MAP sensor line would be off of the line that connects to my FMU?
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Old 11-19-2007, 12:34 AM   #9
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you;ll never boost more with the 15g than the 460cc injectors can give you without the FMU, but yes off the back of the intake manifold is best.
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Old 11-19-2007, 12:55 AM   #10
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That 255 might over power your stock fuel pressure regulator at idle causing some issues as well. If you still have a stock pump and it's healthy don't sell it incase you notice you start having problems.
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Old 11-19-2007, 08:47 AM   #11
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yeah but it's nothing the MS can't fix. But yes, your fueling system is overkill. The 460cc injectors and stock pump with the MS can support a good 300rwhp, something you'll never see with that turbo.
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Old 11-19-2007, 11:03 AM   #12
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Yes I am aware that it is a bit overkill, but I bought both the injectors and fuel pump from a good friend of mine for 70.00 all together, so for that price I am not complaining. So i took the car for another ride last night and the issue was gone. The only thing I noticed now is that my afr's were leaner than they were before, but I guess that is to be expected. Well at least now I can continue to tune. Thanks again guys.
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Old 11-19-2007, 11:05 AM   #13
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Great. good to know because i have failed to relocate my map line from the same spot to solve the same problem. I've been rocking no enrichments for a few months now.
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