Hahn portfueler a/f question

[scottyhops]

so when i bought my car it came with the hahn port fueler with stage 5 calibrated software. since then i did-

8:1 forged pistons
h beam forged rods
arp head studs
fel pro mls gasket
232 cams

when i bought it there was no front o2 sensor hooked up but it idles fine, the other day i had it out and put in a front o2 sensor and my idle isn't messed up but my a/f ratio jumps around from high 10-16. When I'm on it the a/f goes to 12.3

anyone know the reason my wide band and narrow band are going 10-16 a/f?

 

[eclipse420ags]

Idk how it ran good at idle with out front o2. Did you reset the ecu?

 

[glowryder]

reset the ecu.. not sure how or why you would be running without a front one.. thats what the stock ecu needs.. So out of boost your MPG is ###### horrible..You should be setting at 14.7 at idle.. if your not, somethings wrong.. Either Your B is junk or theres another issue. ditch the narrow ban and never mention it again. where exactl is your wide band 02 sensor located? in the correct place/distance? that will also have a bearing on the reading.

 

[BoostedPhoenix]

Does no one really know how its supposed to work ?

Every electronic fuel injection system made in the last 20 years does this. With a narrowband O2 your ECU will fluctuate the Air/Fuel mixture from rich to lean to hunt for 14.7/1 mixture. It does this to keep your catalytic converter happy when you are in stock form. Only with a programable computer, wideband O2 sensor, and no cat will you be able to maintain a constant stoich when not under load.

What his car is doing is absolutely perfect for what a stock ECU is looking for.

Also the front O2 was most likely left out to make tuning the portfueler a bit easier. With no O2 feedback to the stock ECU it was in open loop, meaning the fuel mixture would be very predictable. As long as you are not getting any knock then 12.3 should be acceptable under load.

 

[glowryder]

Correct.. but with no front O2, its going to act funky.. And yes it should sweep. NO ONE said it shouldnt? However.. it shouldnt sweetp to 10:1.... Thats a huge sweep /Hunt. My stock 420a with wide band doesnt sweep like that.. it will warm up around 13.x and sweep 13.7-15.X before it finds its window.

I was telling him to ignoie his narow band "blinky lights" guage.. its inacurate.

12.3 WOT? really.. Poor advice. 11.8, or 11.5 for sterrt . Since your PF you have no way to adjust your Boost Tune for Temps changes in air and Baro.. So you run a little richer to make a tolerance. Even tho hes low CR ( i think he means 8.8:!, not 8:1, that would be a custom piston for the 420a), he still needs a tolerance in there.. Granted if hes truely getting away with that AFR in boots, im sure it screams, but riding the line like that is for Drag cars, not a WW or a street car where condtions change..

Hell he could have an exuast leak causing his WB to read like that, and his idle could be just fine..

You can tuune the car in open loop, fine, but why it wasnt put back in.. sounds janky.

 

[BoostedPhoenix]

Some of the older piston options for the 420a were down to 8:1 compression, the more recent years they revised them to 8.5 and then 8.8. I suppose it depends how much boost its running, I prefer to see closer to 11.5. With the 4g cars I have run over 12:1 afr on 92 octane, of course I was watching EGT's too so, as general advice, you got me that is in the danger zone.

The sweep is normal, and until the ECU gets used to seeing O2 feedback it tends to want to stick on the rich side, give it a few drive cycles, it will learn.

 

[glowryder]

Hmm, well I got in the game in 02, i dont recall any 8.1 or 8.0 , those sound more like stock srt pistions, but w.e.

OP, how long does this sweep last, perhaps thats the better question, if its a few seconds, then its normal, if it just does this always at idle, then id say, issue.

 

[BoostedPhoenix]

I remember reading about a Neon back around '03 (when I bought my avenger) who had 8:1 pistons and his cam gears came apart, and after his experience decided that with that deep of a dish made his engine non-interference at least with the cams he was running. Its been so long they could have been custom too I don't remember.

Since this guy isnt coming back after 3 months i'm thinking he got his problem sorted out.

 

[scottyhops]

i just left the car how it was, ran fine and gas mpg was at 17 around town. but i sold the car