Tuning carb'd 408W with WBO2 - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 10 Old 12-03-2012, 05:19 PM Thread Starter
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Tuning carb'd 408W with WBO2

Well, I WAS going to inject the car and run a Moates QH, but it's just not worth the hassle at the moment. 408W, considerably pumped up, planning to install my NTK Powerdex WBO2 to tune the engine, but need some targets for various states.

What AFR should I be targeting for idle, part throttle, and WOT? I'll be tuning on a BG Speed Demon 750 mechanical.


'89 5.0L LX hatch: all 90mm 2.2L Blowzilla Dart Iron Eagle 306 @ 8.4:1, ported Vic Jr heads, TMoss ported GT40 lower, Deka 80# injectors, EDIS8, GUFB-A9L2-Moates tuned, Tremec 3550, 3.31 gears w/31-spline TruTrac
'66 GT 2+2 Fastback: carb'd 289, Canfield heads - EFI transformation pending

'71 Mach 1: totaled - R.I.P.
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post #2 of 10 Old 12-05-2012, 12:42 PM
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Tune the idle where the engine is happy. What AFR that turns out to be is going to depend on how the engine is put together. 13.5 typically just works across the board, so I would start there and then try to run leaner. Light cruise you should be good at 14.7 to 15.5.. start at 14.7 which will stink the least, and if you care about fuel consumption see if you can cruise smoothly leaner than that.

Moderate acceleration (normal every-day but not grandma acceleration) I also run at 14.7. As you exceed moderate acceleration blend from 14.7 to 13.0 at WOT. Use a vacuum gauge to reference load, less vacuum is more load.

Those are all just ballparks, lock timing to something moderate (say 20 degrees) and adjust fuel to what the engine wants. Everything will be smooth when the fuel is right. After that your power is in the timing.


'94 GT, White, Cobra hood & bumper cover, '95R wheels
393w, Vic Jr 60cc, XE282HR, Victor 5.8 EFI, 80# injectors, Hooker LT 1 3/4 to 3", Borla proXS
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post #3 of 10 Old 12-06-2012, 11:39 AM Thread Starter
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Initially I had my Demon primary jets at #74 and the AFR was reading 14.8 - 16.0 during cruise and light accel. Engine seemed happy that way, it wasn't overheating and had plenty of power. I stepped up to a #76 primary and it was a bit rich, reading in the low 13s during cruise. I put in a #75 and it's back in the 14s, for sure. Not really sure whether I should go back to #74s or stick with the #75s. Fuel economy is important since the car is such a gas guzzler, but not interested in harming the pistons with very lean AFRs.

Is it normal for the AFR to read rather rich during decel and off throttle coasting? I'm seeing values anywhere from 10 to 13 during these conditions.

I was able to fix a lean bog transition issue by replacing the accel pump nozzles (went from stock #31 to #35).
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post #4 of 10 Old 12-06-2012, 12:27 PM
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Just being lean isn't going to hurt the pistons, it's lean in combination with high cylinder pressures that you get at large loads. When we're talking about cruising, if the engine continues to be smooth, you can continue to lean it out without hurting anything.

Your rich decel is normal. The really short but not so perfect answer is that high vacuum decel (aka: over-run) is essentially the same thing as choke so you're going to be richer than cruise.

A better explanation of what's going on and how to minimize the effect if you want is here. http://www.theturboforums.com/thread...tle-decel-rich

'94 GT, White, Cobra hood & bumper cover, '95R wheels
393w, Vic Jr 60cc, XE282HR, Victor 5.8 EFI, 80# injectors, Hooker LT 1 3/4 to 3", Borla proXS
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post #5 of 10 Old 12-06-2012, 01:01 PM Thread Starter
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Interesting read. It seems that the best way to minimize the rich decel effect is to find the initial timing that maximizes idle speed, then tune the carb at that setting. The result being that the carb's transition slot exposure is reduced by the reduction in carb idle speed brought about by the timing adjustment.
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post #6 of 10 Old 12-06-2012, 05:47 PM Thread Starter
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Well, I found that my engine produces maximum vacuum at around 30* of initial timing advance. Unfortunately, this doesn't play very well with vacuum advance and the advance curve built into the mechanical advance. I ended up reducing the timing to 18* of initial and will see how that goes. Car is definitely running pretty satisfactorily... still unsure of whether to step down to the #74 main jet to go a bit leaner. It didn't seem to have any hesitation running between 14.8 and higher.

'89 5.0L LX hatch: all 90mm 2.2L Blowzilla Dart Iron Eagle 306 @ 8.4:1, ported Vic Jr heads, TMoss ported GT40 lower, Deka 80# injectors, EDIS8, GUFB-A9L2-Moates tuned, Tremec 3550, 3.31 gears w/31-spline TruTrac
'66 GT 2+2 Fastback: carb'd 289, Canfield heads - EFI transformation pending

'71 Mach 1: totaled - R.I.P.
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post #7 of 10 Old 12-06-2012, 07:20 PM
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Mine cruises smooth all the way up to 16.0. In the mid 16's it starts acting up a bit. Cruise tuning is really to taste. I'd suggest giving your current setup some time to soak in and get familiar, then make a change to the leaner jet and see if any subtleties creep up that annoy you. If it still feels just as good, enjoy the extra mileage.

'94 GT, White, Cobra hood & bumper cover, '95R wheels
393w, Vic Jr 60cc, XE282HR, Victor 5.8 EFI, 80# injectors, Hooker LT 1 3/4 to 3", Borla proXS
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post #8 of 10 Old 12-09-2012, 11:30 PM Thread Starter
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Thanks for all of your insightful responses. I've got the car running very smoothly and efficiently now. I certainly didn't know how to setup the initial timing before reading that turbo forum post... the engine is running better than ever now.

'89 5.0L LX hatch: all 90mm 2.2L Blowzilla Dart Iron Eagle 306 @ 8.4:1, ported Vic Jr heads, TMoss ported GT40 lower, Deka 80# injectors, EDIS8, GUFB-A9L2-Moates tuned, Tremec 3550, 3.31 gears w/31-spline TruTrac
'66 GT 2+2 Fastback: carb'd 289, Canfield heads - EFI transformation pending

'71 Mach 1: totaled - R.I.P.
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post #9 of 10 Old 12-11-2012, 05:24 PM
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Glad to hear that it helped. I've been in a similar process with my own car and it has very much been a learning experience. I've particularly enjoyed this subject as it's one of those where the more you learn, the more you realize how much you don't know, but at the same time you can apply the new things you have learned with positive results. Very encouraging and rewarding and motivating to stick to it.

'94 GT, White, Cobra hood & bumper cover, '95R wheels
393w, Vic Jr 60cc, XE282HR, Victor 5.8 EFI, 80# injectors, Hooker LT 1 3/4 to 3", Borla proXS
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post #10 of 10 Old 12-11-2012, 07:42 PM Thread Starter
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Yes, it's been a great experience tuning with the wideband. This was actually my first attempt and it took all the guesswork out of the process. It was clear that there was a lean transition, easily corrected. Before the wideband I wasn't sure whether it was too lean or too rich during the transition. Excellent tuning device!

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