BMW K-75 with Garrett GT-12 turbocharger

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fscott
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Posts: 3
Joined: Wed May 25, 2005 6:35 pm
Location: Bastrop, TX
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BMW K-75 with Garrett GT-12 turbocharger

Post by fscott »

Name: Fred Scott
Vehicle: 1990 BMW K-75
Engine:750CC triple with a GT-12 turbocharger, Saab intercooler, Eclipse BOV.
Injection: Port injection (bike is fuel injected from the factory

MS I CPU, v3.0 PCB.
B&G code
2 squirts (It ran on one squirt, but idles better on 2)
I set the Req Fuel to 10.5 and it started and ran on the default map, on the first try!

I'm still tuning the VE map, and may switch to Squirt and Spark Extra sometime soon just to get the 12x12 map.

I'm building a custom case to fit into the stock ECU location on the bike. The MS is bolted to a piece of lexan that I cut to shape, and the cover will bolt into place on top of the lexan. This setup is a little different because normally the MS board is supported by the cover. In this case the cover can lift off the top of the MS.

Free advice: The MS site tells you to tune your accel bins after you've already tuned VE. Save yourself a lot of misery by tuning as much of the VE map as you can with your vehicle in Neutral. Then tune your accel bins. Then finally tune the rest of your map. See, you gotta drive to tune the map, and driving without your accel bins set up properly really sucks.

Also, as soon as you've gotten the bike warmed up and idling smoothly, you can start tuning the cold start enrichments the next time the engine's cold.

Finally, don't be cheap like me and buy a 1 wire O2 sensor. When it's cold it reads lean, and it's hard to tell when it's up to temperature and when it's not.
fscott
MegaSquirt Newbie
Posts: 3
Joined: Wed May 25, 2005 6:35 pm
Location: Bastrop, TX
Contact:

Switched my code.

Post by fscott »

Just a note, I've changed my code to MS&S and started my tuning over again. The 12x12 table makes a huge difference, since I can now have higher resolution between idle and 3000RPM where boost is coming on.

I've still got to sort out an issue with my MAP. The readings I'm getting at idle are around 70KPA, far higher than they should be. I'm not sure if I have a vacuum leak, or if I'm taking my vacuum from the wrong place. I've confirmed the readings with two other vacuum gauges, and verified with other K-75 owners that I should see more vacuum.
I'll be pulling off the throttle bodies and checking it all out soon.

I've also decided to go with a wideband O2 sensor rather than the narrow band unit I'm running now. It's simple economics. To tune the bike as is would take about three hours on a dyno, at a cost of about $300. The LC-1 is only $200, and will allow me to alter my tuning at any time simply by assigning new AFR targets.
fscott
MegaSquirt Newbie
Posts: 3
Joined: Wed May 25, 2005 6:35 pm
Location: Bastrop, TX
Contact:

Post by fscott »

Over the past few months I haven't had much time to work on the bike. I have rebuilt the engine, and it runs better now. It still pulls a MAP of 70kpa, so I'm convinced that this is actually normal.

Installing the wideband O2 sensor gave instant results. The bike's fuel map fell into place quickly, although I still have some areas to work on.

Right now it's parked while I deal with a turbo problem. The oil pump on this bike puts out 60PSI at all times, and that's enough to make oil leak past the turbine seals and into the intake, which explains all the blue smoke I've been seeing. I'm fitting a restrictor to the oil line to fix this.

I'm also working on modifying the stock airbox to feed air to the turbo. This will let me ditch the K&N filter and run a paper filter again, which will let much less dirt into the engine.
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