L-Jet going full Rich on Deceleration Options

[Brian Fuerbach]

1974 1.8 with L- jet. Been playing with a wide band air fuel meter and noticed that when I lift the throttle the AFR goes to max value on the gauge. I thought it was supposed to go lean. I checked the throttle position switch and it checks out fine. Going to check the wiring harness next.

What else should I check? Decel valve?

[emerygt350]

No, no fuel cut on the djet, but I found the rich decel startling as well. I am used to the mustang which goes to 17 or so when you are dragging down a hill. The 84 cfi system is entirely different of course. Speed density with an O2 sensor.

Just really interested in why we don't see the lean mix on our cars (so far)
I want to figure out if this is just the way it is or if something isn't right. I need to look at the manual and see if they mention anything about coming down hills. I could imagine a decent hill could completely foul a plug if that is actually what is happening. I will check that this weekend.

[wonkipop]

No, no fuel cut on the djet, but I found the rich decel startling as well. I am used to the mustang which goes to 17 or so when you are dragging down a hill. The 84 cfi system is entirely different of course. Speed density with an O2 sensor.

Just really interested in why we don't see the lean mix on our cars (so far)
I want to figure out if this is just the way it is or if something isn't right. I need to look at the manual and see if they mention anything about coming down hills. I could imagine a decent hill could completely foul a plug if that is actually what is happening. I will check that this weekend.

i know the vac retard distributor did part of the work on the cleanup.
wasn't all down to the ECU being a transistorised german rocket scientist with the enrichment.

but when you look at it, the most extra retard its offering all the way down is about 3-4 degrees? i am pretty sure that is the extent of the retard.

in our double cans the vac advance comes off straight away the minute you close the throttle from cruise. its the other side of throttle plate. and the retard is the only bit still on. subject to manifold vacuum. so it immediately is pulling the distributor back the full retard. and it will be the full retard travel due to the strong vacuum. ie distributor is at centrifical advance - retard acting = actual advance. that was supposed to help clean up the gunk by burning it slightly later even as it came out the exhaust valve. the later burn meant less NOX in combustion and the hydrocarbons got done in a burn in the exhaust port after the valve and the upper exhaust. in the so called "thermal reactors".
(IMG:style_emoticons/default/laugh.gif) (IMG:style_emoticons/default/laugh.gif)

the idea that brian had that the engine cools down coasting down hill does have merit. in the original set up the hydrocarbons that are there are being burned not entirely and not very well in the combustion chamber on back off.

they were going after NOX and could deal with it in the combustion chamber. get it lower. by making combustion cooler (later).
side effect. more hydrocarbons. burn those on the way out using heat of heads and upper exhaust and letting the combustion flame out into those areas. (side effect making that part of the heads hotter than normal) and further side effect - much more CO. ok they said we will put up with more CO because the cats are coming in a year or two and they turn the CO into "harmless" CO2 (and we don't know about ice caps melting yet so its ok) and H2O.

thats how i understand the emissions equipment to work.

the rocket scientist ECU helps heaps during normal cruise and acceleration etc. does it real good. but its still not genius enough to do the back off thing. and then all the semi mechanical, vacuum gizmos come into play. thing turns into a bavarian cuckoo clock at that moment?

so. maybe brian is on to something with the coasting down hill and cooling off.
like this is actually what they do.
when their so called "thermal reactor", afterburner idea gets cold enough to stop doing the burn.

and of course the EPA never tested that. just revved the engine on a test bed and measured the drop off and whatever came out the exhaust pipe.

one thing i did find out on the EC-A and EC-B research was how closely all these manufacturers tuned everything to the precise parameters of the EPA test to the letter. and then cheated like hell beyond that. thats how VW ended up getting caught in that first EPA cheat way back in 73.

has brian discovered something?