Old Guy Finds Cure For 2,500 RPM Stumble (JRSC+BBK) - Ford Focus Forum, Ford Focus ST Forum, Ford Focus RS Forum
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Old 04-08-2008, 04:39 PM   #1
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Old Guy Finds Cure For 2,500 RPM Stumble (JRSC+BBK)

Those of you who have this setup (with the Ford Racing tune) know about this stumble at about 2,500 RPM. I discovered a cure: Use BP/Amoco 93 octane gasoline. I discovered this after using this fuel two different times (about a month apart). This totally cures the stumble (as long as I have 93 octane in the tank)! It is “smooth as a baby’s bottom” throughout the RPM range!
Normally I use BP/Amoco 92 octane, but the 93 octane stuff is available about 15 miles away from where I live (not exactly handy).
The bottom line:
1) WHY does higher octane fuel cure this stumble? Better yet, what is causing this stumble in the first place?
2) As octane seems to be going down (rather than up), what will the stumble be like when I can only get 91 octane fuel?



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Old 04-08-2008, 07:25 PM   #2
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umm.... I'll just get a better tune and not have to worry about finding a higher octane! lol
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Old 04-08-2008, 09:19 PM   #3
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You may want to go and have your tune checked, if going to a higher octane cures the issue then your tune is off somewhere.... since more than likely the stumble is the ECU pulling timing.
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Old 04-08-2008, 09:38 PM   #4
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Lose the F.R. tune and get a real tune. That tune has issues, I've been there, done that. Getting a real tune solves everything. You're pushing 9-10 pounds of boost. You have a balanced A/F ratio. The F.R. does not offer any of that.
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Old 04-09-2008, 11:54 AM   #5
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Yes, But Is The Tune SAFE???

Quote:
Originally Posted by 4 Bangin' Ben View Post
Lose the F.R. tune and get a real tune. That tune has issues, I've been there, done that. Getting a real tune solves everything. You're pushing 9-10 pounds of boost. You have a balanced A/F ratio. The F.R. does not offer any of that.
My understanding is that you cannot get a safe tune without a knock sensor system (like J&S Safeguard) and an A/F monitor. I discussed this in another post ("No Tune For The Old Guy"). I don't want to spend $1,500 for 10-15 more ponies.
So here's the $64,000 question: Is it possible to SAFELY tune my car without a knock sensor & A/F monitor?
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Old 04-13-2008, 06:21 PM   #6
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