North American Turbocoupe Organization



vam tuning
Boostbird16 Offline
Member
#1
I have a large vam and plan on doing some tuning using my autometer air/fuel guage. Does anyone have any advice, or past experiences they'd like to tell/warn me about. A friend of mine has a mustang with an air/fuel guage and when he drives it's almost constantly changing. I don't understand how to tell if once i have it tuned, whether it's too rich or too lean. any help would be appreciated
Adam Rafferty
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Noname
Guest
#2
I'd recommend against trying to tune your a/f ratio by modifying the VAM in any way. It came relatively calibrated from the factory, and the only reason to modify it at all would be in response to the door's tendency to open further than normal because the spring loses some of it's strength over the years. If anything, this would make the car run richer, so I still wouldn't bother.

Instead, tune your car with an adjustable fuel pressure regulator. I have absolutely no faith in my o2 sensor's output (and therefore don't even run my a/f gauge anymore), and instead have relied on gut instict and my ears to determine how much fuel pressure to run (and how much extra fuel to put into my tuner).

If your a/f gauge DOES seem to provide some accurate data under WOT and doesn't dip into the red no matter how much fuel you give it (as is the case with mine), then just play with your base fuel pressure until you're a couple of bars into the green under WOT. You're pretty safe as long as your o2 sensor is putting out at least .90v.

Let us know your setup (specifically the turbo and desired boost pressure) and we'll recommend a good starting point.

And in regards to your friend's mustang's a/f gauge bouncing around while driving...the car is in closed loop under normal driving conditions (under 3000rpm and not WOT) and uses the o2 sensor to adjust fuel delivery. It basically bounces back and forth between delivering too much fuel (green) and too little fuel (red) several times a second to try and maintain a stoich ratio (yellow). However, the gauge should go into and stay in the green area under WOT or when cruising above 3000rpm.

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Estoril blue 1987 TC 5spd, 141k miles
PRofec B electronic boost controller, kirban fpr, walbro 255 pump, Bailey BOV, Spearco 26x8x3 FMIC, a237 cam, t3/t4 50 trim / stage III .63, 3" exhaust, eec-tuner, 55pph injectors,
Best 1/4 mile: 13.64 (with 2.19 60' time) @ 102.91mph And that was on 93 octane [Image: wink.gif]

[This message has been edited by SteveXX82 (edited 09-30-2003).]
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Glenn 88TC Offline
Posting Freak
#3
What Steve said. I know from experience.

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mods: SDS Digital Fuel Injection, ported & polished big valve head(1.89/1.59), .500 lift roller cam, custom upper and ported lower intakes, 60-1 stage III .63 turbo, powerstroke intercooler, 60mm throttle body, 75pph injectors, Walboro 255HP pump, Kirban adj. fuel reg., ATR header, 3" exhaust with Dynomax Ultraflow muffler, MSD 6al, MSD coil, MSD Launch Control, MSD 8.5mm wires, K&N filter, Star stage III clutch, Greddy Profec B boost controller, Weld Draglites with M/T ET Street 26x11.5/15
NO TC and NO headaches.
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jabobia Offline
Member
#4
ditto [Image: biggrin.gif]

-james

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87 TurboCoupe - 5spd
87 Thunderbird TurboCoupe - 2.3T, T5, 3.55L - K&N, 18psi - [email protected](2.37 60')
88 Thunderbird Sport - 5.0SO, AOD, 2.73L - [email protected](2.39 60')
www.cardomain.com/id/jabobia
jabobia.com
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Pete D Offline
Administrator
#5
Quote: Does anyone have any advice, or past experiences they'd like to tell/warn me about.

Yes! Don't!
Pete Dunham


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Turbobob_dup1 Offline
Member
#6
I too tune with the AFPR. As long as I stay within 2-3 green bars at WOT it's safe. My A/F guage bounces back and forth as well adjusting the fuel as need under normal driving. Some people don't like seeing lights blinking all over the place,but I like it. Tells me where my mix is at and if the o2 is working at all.

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87 Turbocoupe,T3/T4 turbo,much porting,AFPR,255lph pump,GN cooler,K&N in the fender,gutted upper/knife edge lower,big valve head,roller cam,60mm throttle body,Talon 1G BPV.
www.geocities.com/turbobob23/photopageThunderbird.html
87 Turbocoupe,T3/T4 turbo,much porting,AFPR,255lph pump,GN cooler,K&N in fender,gutted upper/knifed lower,big valve head,A237 cam ,60mm throttle body,Talon 1G BPV.
4 + 1 = 8!!
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Boostbird16 Offline
Member
#7
Here's my current perdicament: about 2 years ago I read an article on the web (not from nato's site) about "tuning your vam". It seemed to make sense so i did it. Before long my engine was dying at stoplights because the mixture was so rich. what i did to counter this was i went to the junkyard, I could only find a vam from an 88 tc so i took it (didn't know it wasn't compatible). Since then, i've just ran the newer Vam w/out a newer computer. I figured that as long as i didn't put boost over 10psi, it wouldn't make too big of a difference. After seeing the light (turbocoupe.org) i found out that what i had done was a no-no. So what i've been thinking about doing was trying to find a way to richen up the mix by loosening up the door to the 88 vam. I've also been thinking about getting an AFPR to help fix my delimma. THIs weekend, i'm gonna try to find an old vam at a junkyard. this would be my simplest solution i believe. any comments? thanks
Adam Rafferty
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Glenn 88TC Offline
Posting Freak
#8
Why not just get the correct vam? If you need the small vam you could probably pick one up fairly cheap and it will work right without guessing,

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mods: SDS Digital Fuel Injection, ported & polished big valve head(1.89/1.59), .500 lift roller cam, custom upper and ported lower intakes, 60-1 stage III .63 turbo, powerstroke intercooler, 60mm throttle body, 75pph injectors, Walboro 255HP pump, Kirban adj. fuel reg., ATR header, 3" exhaust with Dynomax Ultraflow muffler, MSD 6al, MSD coil, MSD Launch Control, MSD 8.5mm wires, K&N filter, Star stage III clutch, Greddy Profec B boost controller, Weld Draglites with M/T ET Street 26x11.5/15
NO TC and NO headaches.
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Boostbird16 Offline
Member
#9
alright, i'm going to a junkyard this weekend to look for a vam for my year. if that works i guess i can try a napa,advance, or the zone. thanx for all the help everyone!
Adam Rafferty
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Noname
Guest
#10
Quote:Originally posted by Boostbird16:
alright, i'm going to a junkyard this weekend to look for a vam for my year. if that works i guess i can try a napa,advance, or the zone. thanx for all the help everyone!

I'm sure there are quite a few guys either here or at Turboford.org with small vam's just laying around and collecting dust. You'd have to pay for shipping, but it's a better option then spending loads of money on a new one from a parts store.
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