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98 900SE with stock ECU, downpipe, exhaust, K&N, Viggen intercooler, 17in tires/wheels and finally got the SMBC installed and tuned...wow...definite must do update. See below for my "seat of the pants" results.
I now have a question about the downstream effects. Since the wastegate is not letting go of boost less than 8-10psi, then the pressure under this threshold has to be released via the bypass valve when I don’t crest the SMBC limit, right? SO, more hot air is making it back into the intake than normal, maybe not much, but it’s more right? Does this make a stronger case for a BOV in a T5 setup??
Also, at times of low boost, say in the lower half of the yellow on the boost gauge (1-6psi?), I get a ghostly moaning sound that I think is annoying (my wife likes it). Sometimes I hear it for more than 5 seconds, I think a beefier non-diaphragm BPV would fix it, but now I am thinking a BOV would be better??
I also think the car is running hotter, no evidence other than my nose under the hood; would a lower temp thermostat be in order??
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1st gear, much quicker turbo spool-up, breaks 17s loose at 5500 rpm. Turbo gets halfway into the red (I don't know how or why, but ye-ha, I never made it to the red in first before). I am guessing that this is around 15 psi. I now shift just before 5500 rpm to save the tires and tranny.
2nd gear, spool is better, breaks the 17s loose at around 5000 rpm. Really gotta hang on when turbo comes on in second, really pulls it hard, going to install a beefier steering rack brace next. Turbo gets halfway into the red again, yipee!
3rd gear, spool is better again, blasts to 80 are really fun, and turbo goes to about 1/3rd into the red and stays there as long as I keep the foot is to the floor (I think that is 12-13psi?). Previously, I would just tickle the red zone, and it would back down to the space between the yellow and red.
4th/5th gear, have not tried the full blast run into fourth and beyond, just no safe place to do it. BUT the time from no boost to halfway thru the red (15psi) is around 2 seconds (used to be closer to 4 seconds). In both gears, I get middle of the red, and it will stay there as long as I have my foot down to the floor.
I tried a stage 3 ECU, and my wife and I both agree that this SMBC setup is better. The SMBC gives more boost down low and the ECU upgrade was just producing hot air over 18 psi and not producing speed. So if I were to get another ECU, I would only want to max out at around 18psi anyway, and I feel that 15 psi is pretty close; especially when the boost builds faster. I might still get another aftermarket ECU, but I don’t have 800 bucks burning a hold in my pocket right now!
posted by 24.175.2...
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