Idle Mixture w/FI

Carbs & F.I.

Moderators: Sluggo, Amskeptic

Post Reply
User avatar
vwlover77
IAC Addict!
Location: North Canton, Ohio
Status: Offline

Idle Mixture w/FI

Post by vwlover77 » Sun Apr 20, 2008 7:11 pm

I got a BIG improvement in the "stinky rich" smell I used to have at idle when I went back to the stock cam and close to the stock CR.

But, my idle still smells a bit rich (no catalytic converter), so I thought I'd try out the CO meter I bought off eBay last year to dial in the idle mixture.

The sticker on the engine lid says 1% CO, but that's for a '78 California model and I'm running an ECU from a '77 49-state model. (I do have the original '78 California ECU that I could put back in, though.)

The best I could get on the meter was 3.5% CO, and I must have the bypass drilling in the AFM wide open because further backing out of the mixture screw makes no difference. It still smells a bit rich, but maybe that's just the way it is going to be with this ECU and no cat. converter.

Were these engines being "coerced" into running lean at idle? I moved the AFM wiper just to see where things stood after the adjustment and the idle speed went WAY up when I moved the wiper in the "more fuel" direction.

Thoughts?
Don

---------------------------
78 Westy
71 Super Beetle Convertible Autostick

"When we let our compassion go, we let go of whatever claim we have to the divine." - Bruce Springsteen

User avatar
Amskeptic
IAC "Help Desk"
IAC "Help Desk"
Status: Offline

Re: Idle Mixture w/FI

Post by Amskeptic » Sun Apr 20, 2008 7:51 pm

vwlover77 wrote: Were these engines being "coerced" into running lean at idle?
Yes. Driveability was compromised and it showed up in all of the reviews. FI was considered quite good except when cold.

Do not adjust to the numbers. Adjust to the engine's preferences. For all we know, your CO meter is picking up fuel vapor from the recovery system. The official method was to block off the fuel vapor recovery system when testing the CO.
Colin
(even a clean '78 FI engine will smell pretty fuelish in comparison to modern cars, you need to breathe my '62 Lincoln's exhaust to get straightened out pretty quick)
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

vdubyah73
IAC Addict!
Status: Offline

Re: Idle Mixture w/FI

Post by vdubyah73 » Mon Apr 21, 2008 4:30 am

Amskeptic wrote:
vwlover77 wrote: Were these engines being "coerced" into running lean at idle?
Yes. Driveability was compromised and it showed up in all of the reviews. FI was considered quite good except when cold.
Well, that explains some of my disappointment with FI. I almost want to go back to the dual Weber ICT's. I have a midrange miss, it's more of a moderate throttle hiccup. Light throttle is fine and if you mash the pedal it's fine. But if you just maintain speed up hill and dale, with moderate throttle there is a miss that feels almost like a rippled road surface working the suspension just a bit. This goes away when fully warmed up, but in cold weather, bopping about the Cape, running errands, I don't often get fully warmed up. My gas mileage only went up about 1 MPG, I get about 15-16 now, in mixed driving. With the carbs I got 14-15 MPG and had a lot better throttle response.

FI is quieter than dual carbs, no induction roar. It's nice to hear that sweet little tractor sound the AC VW makes as you drive down a Cape Cod cow path that we call roads.

FI just starts, period. turn the key and a few compression strokes shes running.

FI is smoother than carbs, but feels like there is a disconnect between the gas pedal and the response. This is not a bog, it's asking for a shot of whiskey and getting air and a whiff of cheap rum. FI is kinda like " who me, you want me to what? OK here we go then". With carbs you get nearly instant throttle response both when gunning it and when letting off. I can distinctly feel my decel valve working on the FI.

FI is just as complicated to learn and adjust as dual carbs, it's just different.

I'm gonna leave the FI in for a full year. Maybe the FI will redeem itself in the glorious summer weather that is around the corner.

If I had to suddenly take off on a loooong journey, for a family matter or sumpin, I would probably put the dual Weber's back in. I know I can make a knackered up Weber run to get home. I wouldn't know what to do if, say my ECU, AFM, fuel pressure regulator, injector or resistor pack went south on me.Everything else has a work around.

Colin, see my old post about " going back to FI" In " Fuel Delivery"

Bill
1/20/2013 end of an error
never owned a gun. have fired a few.

Post Reply