L31 Extreme Budget Build

[L31MaxExpress]

It will have your a$s walking home if that counts as a change.

Ran that box for 5 years on the 83, been in my climate controlled office of the shop since it came off. I will throw some Deatschewerks connectors in line so that I bypass it easily. The box I have is the OG one not the newer digital design. It made a noticeable difference on the old 83 G20. That MSD equipped engine once made it home after the fuel pulsator (springy rubber fuel hose GM used on the TPIs to help prevent fuel rail noise and injector tapping) in the tank split, dropping the TPI from 46 psi to ~20 psi. Wideband was pegged lean the whole way home yet the MSD was still lighting off the mixture, no idea how lean it was, the wideband went off the scale at 1.25, so it was leaner than 17.6:1.

 

[L31MaxExpress]

I replaced the rubber pulsator with the later design unit. Honestly thinking the Proflow 4 system on this 87 would have benifited from a Pulsator too. If I have to drop the tank in the future, it will get one too. I have a couple of new ones in my tool box. It helps prevent the injectors from experiencing a pressure hammering effect and smooths out the fuel flow as the injectors pulse.

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[L31MaxExpress]

So the MSD6a box is on and running the same MSD resistance coil speced by Edelbrock for the PF4 and running the same 0.044" gapped plugs with the essentially new ignition system has cut the idle pulsewidth an additional ~15% at hot idle. The MSD6A seems to be providing the same benifits on this as it did on other vehicles I have run one on in the past. Engine is idling smoother than ever, starts instantly, nice crisp throttle response too. The fuel that is getting injected is getting burned. I leaned the idle and cruise target air/fuel ratios out to 15:1 and it is just as smooth as it was at 14.1 or 14.7:1 before.

 

[Scooterwrench]

So the MSD6a box, running the same MSD resistance coil speced by Edelbrock for the PF4 and running the same 0.044" gapped plugs with the essentially new ignition system has cut the idle pulsewidth an additional ~15% at hot idle. The MSD6A seems to be providing the same benifits on this as it did on other vehicles I have run one on in the past.

You ought get exceptional fuel economy when you get it all sorted out. Are you eventually going to set it up for lean cruise?

 

[L31MaxExpress]

You ought get exceptional fuel economy when you get it all sorted out. Are you eventually going to set it up for lean cruise?

If I ever swap it to a GM PCM I will. 15:1 is as lean as the PF4 controller lets you target. The engine is perfectly happy there and there is ZERO unburned fuel exhaust smell to it now with the cats.

Kind of makes me wonder now if a CDI box would not have fixed the lower rpm misfiring the cam in the 97s 383 gives it due to exhaust dilution. I have a Pertronix Second Strike I may put on it to test out.

The 2nd strike operates in a unique way. It has both an inductive spark as well as a capacitive discharge spark. The first spark is the ordinary inductive spark. The collapsing magnetic field in the coil from the inductive spark helps charge the capacitor which then provides the capacitive discharge. The Pertronix box is thus able to provide 2 sparks all the way through the RPM range vs only under ~3,000 rpm.

 

[Supercharged111]

Will the Proflow oscillate north and south of stoich to keep a 3 way catalyst happy?

 

[Scooterwrench]

I did that by accident when I was a kid by adding a second condenser on my Honda 50 mini trail. It buzzed the spark plug good and screwed up grandpa's TV every time I rode past the house.

 

[L31MaxExpress]

Will the Proflow oscillate north and south of stoich to keep a 3 way catalyst happy?

Yes it still oscillates in a similar range to the GM PCMs. Cats only need stoich for maximum emissions reduction effect. Cats were on vehicles for years before feedback fuel control systems existed. On the road you transition so much in throttle position and load the air/fuel ratio has a natural rich/lean swing to it anyway.

 

[HotrodZ06]

So where's $2000 in machine work coming from then?

That was a quote from another thread i was reading listed as a budget build showing the subjective nature of "budget" lol

 

[Scooterwrench]

I replaced the rubber pulsator with the later design unit. Honestly thinking the Proflow 4 system on this 87 would have benifited from a Pulsator too. If I have to drop the tank in the future, it will get one too. I have a couple of new ones in my tool box. It helps prevent the injectors from experiencing a pressure hammering effect and smooths out the fuel flow as the injectors pulse.

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Would TBI benefit from one of these?