Spud's "The Definition of Ghetto-Rigged" M90 Supercharger Build Thread (lotsa pics)

[RedCavyRS99]

I had to join just to say your insane and its freaking awesome!!!!

[BMWidmer]

shits dope

[Spudchucker]

Thanks guys


I put the hood on hold today for more important things, like using my new tuning cable to let me know running my stock sized pulley is safe I know, the intercooler isn't in yet, but I couldn't wait 1 day, forget til the weekend haha. On the stock pulley, while I don't know what the max boost is because I'm too scared to try it, I know that I at least hit 8 psi before I pussy out. Oh, and it sounds like a SCREAMING BAT OUT OF HELL, at 8 psi. M90s are apparently reallllly loud when you use em like you're supposed to haha. No more whistle, it's all whine now

So now I'm going into ROMRaider again and working on the tune. The intercooler will hopefully be in this weekend so I can really be safe. Until then I will just drive like an old lady, which yes, I do have the self-control to do haha

[Skidd]

Hey Spud, when you get that IC put in, do me a favor, and pay close attention to any throttle response delay. I'm curious if it will pose an issue with your setup. Actually, not an issue so much as, just something to notice. I know that having your TB before your SC reduces throttle response "some", but I want to know how much, if any at all. I don't know if I actually will, but I still my try putting my TB before my SC. But, I gotta admit, I love the instant-freakin-tanious response of where it is now.

[Spudchucker]

Originally Posted by Skidd

Hey Spud, when you get that IC put in, do me a favor, and pay close attention to any throttle response delay. I'm curious if it will pose an issue with your setup. Actually, not an issue so much as, just something to notice. I know that having your TB before your SC reduces throttle response "some", but I want to know how much, if any at all. I don't know if I actually will, but I still my try putting my TB before my SC. But, I gotta admit, I love the instant-freakin-tanious response of where it is now.

Sure, I'll keep ya posted. The reason I moved my TB was because I didn't have the BPV in, so I figured that was how I needed to compensate, at least that's what Corky Bell said. I'll prolly just keep it there even when my BPV goes in, just because that's how the book said it should be, but I'm still kinda researching the area a bit

I actually haven't noticed much lag at all with my current setup, but that could just be because I was in closed loop before, and went permanently open loop when I did the install.. That 1/2 second delay with the closed loop system would likely more than account for any throttle delay I put in with the new TB setup

[Spudchucker]

If anyone wants my AC compressor, I have it for sale now, give me an offer and we'll go from there

I'm definitely open to trading, especially if there's a wideband o2 sensor involved

[Spudchucker]

Bit of an update.. My supercharger rebuild kit came in and I tried rebuilding it, but I could only replace the coupler due to my pulley being stuck on wayyy too hard. My pulley puller wouldn't get it, so I built a super hardcore wooden fixture to pull it, powered by a 4 ton car jack.. see below




I completely maxed out the jack and the pulley wouldn't budge under 4 tons of pull, so I gave up and jumped onto installing my 31" front mount intercooler

I've made two brackets thus far, and plan on a few more to really keep it in place tomorrow. I cut out the middle of my bumper with a dremel, and spent like 30 minutes grinding 2" out of the bumper bar so I would fit snug. I had to slap the bumper back on, even if only hanging loosely, just so I can daydream a bit





Can't wait til it's in! I'm gonna hold off modifying my injectors, cause I plan on routing the output side through the stock airbox in the fender, hopefully sucking a couple of pounds out and leaving me with 6 pounds of boost (which they could handle). I'll clean it up later when my whole fuel system is updated

[williaty]

Originally Posted by Spudchucker

I'm gonna hold off modifying my injectors, cause I plan on routing the output side through the stock airbox in the fender, hopefully sucking a couple of pounds out and leaving me with 6 pounds of boost (which they could handle). I'll clean it up later when my whole fuel system is updated

Ouch! Chemistry fail!

The amount of injector necessary is based on the grams of air entering the engine. The pressure drop in the intercooler is due to a reduction in temperature. Therefore, the pressure drop in the intercooler does not result in fewer grams of air entering the engine. Therefore, an intercooler does not reduce the need for injectors.

In fact, there's a decent chance that the intercooler will raise the required fueling. Since engine filling is based on volumetric efficiency, and the air pulled in with the intercooler in place has a higher volumetric density, you actually should be getting MORE grams of air into the cylinder, requiring more injector.

[Spudchucker]

Originally Posted by williaty

Ouch! Chemistry fail!

The amount of injector necessary is based on the grams of air entering the engine. The pressure drop in the intercooler is due to a reduction in temperature. Therefore, the pressure drop in the intercooler does not result in fewer grams of air entering the engine. Therefore, an intercooler does not reduce the need for injectors.

In fact, there's a decent chance that the intercooler will raise the required fueling. Since engine filling is based on volumetric efficiency, and the air pulled in with the intercooler in place has a higher volumetric density, you actually should be getting MORE grams of air into the cylinder, requiring more injector.

I'm thinking of it more in terms of there being a whole lot of space between the SC and the intake maifold, so the air loses pressure over the weird bends and flow disruptions (via the air tank in the fender, which is both very volumnus and constricting at the same time). The intercooler itself should be fairly free-flowing due to it's size

[williaty]

Originally Posted by Spudchucker

I'm thinking of it more in terms of there being a whole lot of space between the SC and the intake maifold, so the air loses pressure over the weird bends and flow disruptions (via the air tank in the fender, which is both very volumnus and constricting at the same time). The intercooler itself should be fairly free-flowing due to it's size

You're right that the IC is fairly free-flowing, but so is everything else, really.

If you set up a series of pressure gauges, you'd see that almost the entirety (I'm acknowledging that some heat is shed in the piping here) of the pressure drop is over the intercooler itself. This is because the IC sheds heat from the air. Since the volume in the intercooler is fixed (since it's made of metal), the pressure of the air MUST drop as a consequence of the drop in temperature.

Now, the engine takes in a fixed volume of air (Volumetric Efficiency). However, if you increase the pressure, or drop the temperature, the engine will take in an increased mass of air for the same volume. The question that's relevant to your injectors is wither the drop in temperature increases the mass of the air faster or slower than the drop in pressure decreases the mass of the air.