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Looks like Saabines running problems are sorted as per this morning. Last Saturday, I took a fuel pressure gauge to the car and found that she only ran decently with the extremely high fuel pressure I'd inadvertently set before (5.8 bar above manifold w/vacuum hose disconnected & plugged instead of 3.3ish) - as soon as I turned it down to a normal level she'd start to miss and stumble.
I first assumed that somehow the duty cycle of the injectors at idle and high vacuum running was messed up for some reason (she would run OK when at low vaccum/boost on the road) and called my dealer's tech, who suggested trying to sort things with the adjustment screw on the AMM. As the 'blanking plug' on the latter (a Bosch 005 unit) was a bit substantial for a blanking plug and I wasn't sure whether it actually had a blanking plug, I decided to try the 34,6 lbs 9000 2.3T injectors that I wanted to put on at some point anyways. Which made the car run OK again aprt from some minor stumbles that seemed to be occurring randomly. So I drove to the Saab workshop to drop off the fuel pressure gauge, and made an appointment to check CO values at the test computer this morning.
Did that and sure enough, CO at idle was near 5%, HC values were through the roof and she would start to stumble and miss again as soon as you tried to lower CO by leaning the mixture out with pulling a vacuum hose and pinching it a bit. There also was a distinct miss when revving the engine to 2,500 - 3,000 rpm when stationary and with CO dropping to < 0.5%, and HC was still about 2-3x higher than it should be on a healthy engine
As I told the tech that she ran very well before the DI install (she had her MOT at the same place, using the same test equipment just 2-3 months before the install with the same engine config, and she idled perfectly well when within the specified 0.9-1.5% CO range for the T16) he thought that a weak spark might be the problem, and hance more fuel was needed to ignite the mixture properly. Whenever the engine was revved in a low-load condition (stationary or cruising), the mixture would lean out sufficiently for it to start missing - which correlated perfectly with my findings.
Enter a different DI cassette - bingo! Missing when revving the engine gone, hydrocarbons dropped to a perfect 43 ppm at near 3,000 rpm. CO at idle still high because of the big injectors, but it runs perfectly well with it, the 4.4ish% was in a sensible range according to the tech - apart from next year's MOT of course ;-) - so I should not worry about excessive fuel causing cylinder bore wash or so he says, and it drops to a perfectly normal level when revving under low-load conditions. So that means the fueling for my projected ~300 hp level is also sorted in one go. :-)
Got new DI cassette of latest version (black T7 version can be used as a replacement for earlier red versions, but not the other way round), installed it, drove home - cannot find anything to fault her running. Runs well when cruising, runs well under acceleration, smooth transitions between those states, rock solid idle. Sorted, then. :-)
Now to get that downpipe fabricated and maybe look at alternative IC options, final set up should be easy now...
posted by 213.116.1...
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