It lives, but isn't feeling well
Turbo Mini Forums

Got the car running yesterday. Had time for one stab at a tune. Guessed wrong and had the midrange too rich. This is a Weber 32/36 downdraft. The good news is that it looks like I'll be able to tune the high RPM mixture using my now extensive collection of Weber air correctors, without having to put a restriction at the carb inlet.

On the dyno it went way rich in the midrange, like 10:1 A/F, then started leaning out above 3500RPM. At 4200RPM, was still running 12.2:1, but then it started misfiring. Dyno operator thinks maybe the spark is getting blown out by the compressed mixture. I have the a 65DM4 electronic dizzy, so if it is all I can think of is maybe the coil is weak. This is based on my experience of electronic ignitions on other cars, which seem to be maintenance-free for decades. Is the Lucas module prone to going bad? I'm running NGK BP6-whatever plugs, gapped to 0.035" (~0.9mm) as I recall. Cap, rotor, wires, plugs have only a few thousand miles on them, less than a year old.
#2 plug looked rich, #3 looked right on. Don't think I can tell much from that until I get the overall mixture straightened out.

I'm considering replacing the coil (Lucas gold, unknown age) and the plugs, and tightening up the plug gap.

Any advice would be greatly appreciated.

One other problem: There was oil smoke from the turbo. There is a kink in the oil return line, but we were thinking the scavenging pump would be able to push the oil through it OK. Fixing the kink, hoping that takes care of the smoking.

Pretty much standard Metro LE engine, weird rear turbo setup @ 5PSI (for now), 20psi electric fuel pump, rising rate Aeromotive regulator, Weber 32/36 with a pressure hat.

Edited by fortfun on 25th May, 2006.

1275 with Back Door Turbo

Didn't run well enough yet to get meaningful power numbers.
I thought the restrictor rings were to keep it from going too lean at higher airflow under boost. This is a downdraft with a choke plate on top, so if I must have the restrictor enrichment effect I can fiddle with the choke plate so it doesn't fully open.

1275 with Back Door Turbo

Hi,
I wouldn't use the choke as a restrictor, it will cause you more mixture problems. Are you running suck through or blow through? The restrictor is vitual on the blow through system, so that the plenum is at a slightly higher presure than the carb.
This higher pressure also needs to be fed into the float chamber as well as the fuel pressure regulator, to increase fuel pressure with boost pressure.
Sorry if you already know all this. Take a look at Jukka's site, although it's a side draught, the principal is the same.
Also a Gold coil is the wrong one for an electronic setup, it will overload the amplifier.
Cheers,
Gavin :)

Edited by Bat on 25th May, 2006.

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It is blow through. Have the bowl and regulator pressurized from a tap upstream of the carb hat. I'll get the right coil. Ignition ran fine naturally aspirated, but maybe it was on the edge.

1275 with Back Door Turbo

Coil was not gold, I was mistaken. Lucas DLB102. It was leaking oil, though. New coil on and ignition seems sorted. New fuel system had a kinked hose. Then seems the fuel bowl is still not getting enough fuel, suspect a fouled float valve. Hitting it again today.

I'm sticking with the Weber for now, but if it doesn't work out I have a regular HIF44, just have to get the turbo seal kit and a plenum.

1275 with Back Door Turbo