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roxanne68 roxanne68 is offline
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Join Date: Aug 2005
Location: New Brighton, Minnesota
Posts: 37
Garage
Turbo Glowing with no Boost at steady State Cruise

Title pretty much says it all. When I take the car out for an extended cruise of 25 miles with no boost, holding rpm in the 2300-3000 range in 4th gear (70mph) the hot side housing is glowing red orange. I mean really glowing, from the inlet flange, to several inches down the exhaust exit pipe towards the muffler. The headers were not glowing at all, and had surface temps near the head of around 550-600F. To contrast this, when I just go out on shorter trips, boosting many times (8-10 pulls) when I return from the garage there is only what I would consider to be a normal dull red glow in the center of the inlet flange.

After I let it idle for 3-4 minutes, the housing has cooled back down. So idle temps are under control, its just the extend low load cruising that is the issue.

Here are the facts:
Timing: 8 BTD at idle, 25 at 4000 no vacuum retard, still has boost retard
Boost: 0.9 bar comes in around 3000-3200
AFR: 12.5 at idle, upper 14ís at steady cruise, low 10ís to low 11ís during boost depending on rpm
Engine temps never exceed 230 at the gauge or 220 at the engine case, or thermostat housing measured with a pyrometer.

I am stumped; I have swapped out a new O2 to confirm that itís not the sensor. What do I go after next? Sticky mechanical advance (seems to advance fine when revving the engine)? Poor oil supply to turbo (I checked flow when I installed the engine 500 miles ago and it was fine)? Plugged muffler (doubt it). Could my timing marks be off on the pulley (donít know if itís a stock one)? I am planning on trying to fatten up the cruise AFRís to the low 14/upper 13 range and see if that helps.

Sorry for the poor pics, the build is still in progress, with brakes, body, interior, and suspension on the list for the long upcoming Minnesota winter.

Cheers and thanks


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-Derek

'81 Euro SC coupe, 79 3.3 930 engine, 930 transaxle, B&B full dual outlet exhaust, 964 intercooler, 964 cams, CIS injection, K27 7006 turbo. '08 Triumph speedtriple. '06 BMW 330xi
Old 10-30-2011, 06:09 AM
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