Welcome all 928 forum refugees!
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By Shifted
#10433
This is a before and after comparison of our 1987 928 S4.

In the before, it had S3 profile cams and a X-pipe and had a little tuning time with the SharkTuner. It also had 60 pound injectors and a Bosch 044 fuel pump, but I doubt that the fuel updates had any performance impact on the performance in the "before" configuration.

On the after, it has S3 profile cams, 11.6 psi of boost from a mid-mount turbo (starts hitting boost around 1,700 RPM and is at full boost by 2,800 RPM), air-to-water intercooler, 60 pound injectors and a Bosch 044 fuel pump. The car is 100lbs heavier with this configuration, as weighed with corner balancing scales.

These graphs were made by using RPM vs. time output from the SharkTuner and graphing it with Virtual Dyno. So, take it as a general ballpark just to show the relative difference of a before and after configuration.
928 - Before and After Turbo v2.jpg
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By worf
#10499
An extra 200 hp? Yeah. that works. :ugeek:
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By Shifted
#10620
As you gentlemen probably know from your own experiences, it doesn't feel like much when you're doing tuning acceleration runs on flat and straight roads with no other cars around. You pay so much attention to the data, and you're ready for it, that it just doesn't register.

When it hits me is when I get comfortable driving it around and give it the same amount of throttle that I used to use when I want to accelerate briskly (from a stop, passing, etc). That's when you can't deny that there is a monster kicking you down the road. In those moments, it's scary fast.

Totally worth the work and expense!
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By amdavid
#10820
Understood, and YES!...worth the time money and effort in those casual moments when you know the beast will react to the punch. :mrgreen: :mrgreen:
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By Shifted
#36637
RSMartin wrote: Mon Nov 23, 2020 2:28 pm What set up did you go with ?
Manufacturer, installation, final tuner ?
Mid-mount turbo mounted just in front of the transmission. Water to air intercooler, BOV, 11.6 psi spring in the wastegate, 60 lbs injectors. I did everything myself (design, fabrication, installation, tuning). Except for the exhaust pipe. I had Colin weld that up and ship it to me. My welding is pretty good, but I hadn't worked with thin walled stainless before, and the learning curve was proving to be expensive. Looking at my last few attempts on the stainless I realize now that they were just fine and I could have finished it up, but I was just being too much of a perfectionist. Colin also provided the on-going encouragement, sounding board and initial guidance to get me started. So, it felt right to give him the business.

Boost starts to build within 100 rpm of going from fully off of the throttle. I haven't tried WOT below 1,500, but if I am coasting at 1,500 with my foot off the gas, and then stomp on it, I have boost by 1,600. Full 11.6 psi comes on just before 2,800 RPM and does not fade or drop off after that.

Anyway, this is a more recent graph after the exhaust wrap, turbo blanket and some more tuning. You can see where the power comes on, regardless of boost levels.
1987 928S4 11.6psi Turbo.JPG
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