[urq] What cause overboost ?

[martin at quattro.ca]

Louis-Alain,

Early '83s had a different pinout on the ECU (yellow vs blue lable).

THis might cause some problems as well.  Use matching ECU or rewire the plug.

YOu can see the valves throuhg the oil fill cap.  It's clear if they are
solid or hydraulic.

YOu need to have a Air/Fuel gauge, I keep telling people that this is very
important tool for turbo engines.  I had one fuel distributor running out
of fuel at 7psi, wouldn't have known that without the gauge.

Hope this helps.
Martin


> On Eric's 1985, I tried 3 ECUs:
>
> - the one that came with the car. Cut-out at near 4000 rpm. When I opened
> the ECU, one of the chips (OEM stock is :HITACHI R21021 2332(A) 421
> MAC02V1)
> looked it had been replaced with an unmarked chip except for a paper tag
> (AXJ103 <04>). So it might be chipped. No one knows for sure.
>
> - Brady's chipped ECU. The same chip (HITACHI R21021) is obviously
> replaced
> with a (LD2732A25, paper tag L24E Mo2) chip which is mounted on longer
> "legs". With this one in the car, we were able to push the engine over the
> 4000 rpm for a short period then the cut-out came back.
>
> - My own 1983 not-chipped ECU. With this one, cut-out is at 3000 rpm under
> load, but the engine can go over 3000 rpm if we feather the throttle.
>
>
> Now, this leads me to believe an overboost situation that cause any ECU to
> stop the fun at different RPMs. But, if there is no obvious leaks in any
> hose, as I found last night, what can cause overboost ?
>
> If the timing is way off, could it be enough to cause overboost ?
>
> By the way, at idle, the engine is VERY smooth and quiet. This made me
> wonder if the head was replaced (hence my question about the vacuum pump
> boss) with an hydraulic one.
>
> Is there a way to identify a correct WX head from another hydraulic head
> easily ? Without removing the valve cover, obviously...
>
> Last question: could it be a failing fuel pump relay, or a failing
> distributor ? It does feel like an ignition cut-out.
>
> Thanks in advance,
>
> Louis-Alain
>
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