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The setup (Saabine);
92 mm bored block w/Cosworth pistons; ~8.5:1 CR; fully weighted & balanced
'87 B202 head, intake ported to match 2.1 intake
'Stage One' full race Garrett T03 w/360 thrust bearing, stock .48 turbine, what looks like a trim 55 compressor wheel with blades angled differently to aid high rpm flow at the expense of midrange
3" custom downpipe eliminating front muffler (no cat on '85 Euro cars), 2.5" single box sports exhaust (Simons) from there
Stock IC + fan, 89+ piping
Cone air filter at AMM
Water not connected
Forge MBC set at ca 0.9 bar (preliminary)
LH 2.2 + DI
Speedparts LH 2.2 chip, 6,800 rpm limit
Custom DI eprom from race c900
Bosch 220 l/hr rated fuel pump from Speedparts (actually a K-Jet pump, Bosch # references to 78-81 99/900T...)
5th injector still there, just not connected & driven by anything
Fuel set ups tried after DI install, stock downpipe still:
stock injectors + 3.3 bar rrfpr (1.7:1) setting as before: did not run or idle well at all. Adjusted rrfpr so that it would idle half decently - OK on the road save for big misfire (like a rev limiter) at 5K rpm. Would misfire a bit on idle, more so when revving it to 2-3K when stationary.
Borrowed fuel pressure gauge from Saab shop and found 5.8 bar at idle!
Swapped stock injector for my set of 2.3T (33.9 lbs/3.0 bar) jobbies and turned rrfpr down to 3.2 bar. Ran much the same. Trying to set it lower - more misfires.
Checked values with vacuum line connected on test run: idle was about right at 2.1 bar (for 1.7:1 rate) - only when on boost I did not see it go past 4.0 bar. Strage, that)
Went to Saab shop with this set up for stationary mixture check. Way too rich at idle (4.3% CO @ 1K ish), dropping to 0.8% whenever throttle was applied. PPM value way too high at 118 @ 2,500 rpm.
Diagnosis: weak spark: Swapped DI cassette for new (black T7) one: misfiring gone, ppm value dropped to 43. Sorted, I thought.
At home: still misfiring on revving car when stationary as soon as I try to lean out mixture a quarter of a turn or more. So I leave it at just over 3.0 bar with the 33.9 lbs injectors. Car starts, idles and runs fine -only I still got 'rev limiter' at around 5,000. Car is pulling vigourously up to that mark.
Havecustom downpipe made nad installed. Guys at tuning shop confirmed that car seems to idle and run very nicely even though injector + fuel pressure combo and stationary CO value would indicate it's running way, way too rich. All techs I talked about it confirmed 4% static CO would not cause bore wash problems or anything - only problem with this that I must get stationary CO to under 1.6% @ 850 rpm by Februari for smog check!
Now get this - the 'rev limiter' is still there with the downpipe, only it has shifted to 5,500 rpm! Now if fuel pressure breaks down at the point the misfire starts (what I orginally thought) it would be logical that the better exhaust flow would make this happen at a -lower- rpm than before, right?
I would like to have this sorted -before- I go to the dyno as I cannot afford to make the dyno session an open-ended affair (which could easily run to $1,000 including Eprom programming). If I can trace the fault and find a fuel set up that idles and runs normally, I could use a 5th injector driver that can handle the DI rpm pulse signal (MF2 et al) and only be bothered with tuning at WOT on the dyno - which should be possible to do properly in an hour or so.
So, where to start? Try the stock injectors with 3.0 bar fpr? Go to a shop where they can read injector duty cycle and ignition pulse on the road?
TIA,
Eric
posted by 217.149.2...
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