Originally Posted by ImportLabSRT
Now for the turbo news.....I daily drive this car and have yet to have any problems other than a little overheating issue. 2 weeks ago there was a few days where the outside temp was over 100deg and where my FMIC is located, it was blocking most of the air going to the radiator. Nascar style, I pulled the front lower grills and the temps went back down to normal.
I now have 2k miles on this setup and love it. City I get about 22mpg and highway I get 28mpg with A/C on and 31mpg w/o A/C. I have yet to up the boost and play with the tune. The car is on the rich side for safety so more power is there even at 15-16psi that I am at now. When its cold out at night, I see 18+ psi at times and the car hauls ***.....bbbbuuuuttt if the car sees 20psi, the ECU gets a little pissed off and cuts fuel + spark.
As for track use, a torque converter is going to be needed to get the car off the line. I can only get 11-1200 rpms out of my stock converter at the line before I push the front wheels thru the beam. At 1100rpms, the turbo only builds about 1lb of boost and when I let off the brake the car bogs and slowly crawls to a 2.6 60ft and blows my Hoosiers away going into 2nd and at times 3rd. My next goal is to get 20-21psi out of this thing. Fuel injectors and a fuel pump will have to be sourced
Thanks for posting the driver impressions. You do a great job of describing the way the car has changed. A electronic trans-brake or a brake placed on the driveshaft could solve your launch issues. Hit the button to apply the brake, gas it up to build some boost and when the tree falls or the light turns green. release the button and go. But if it is blowing away the tires in 2nd or even 3rd now, lol then gawd help you in first if it is up to even moderate boost. Bigger rears tires and really great rubber (maybe even DR's) would be required to really get the most out of it. I am very impressed to see how much the fuel mileage has improved. I never dreamed that the SC'er was placing that much drag on the engine when cruising.
Now for the Fuel Cut issue. Find the pressure sensor module the reads analog pressure and converts it to a voltage. That voltage input will be routed to the ECU and when it reaches a set value will trigger fuel cut which is supposed to be at a preset inlet pressure. In your case you reported 20-21 psi. You can put a voltmeter on the output voltage and use a pressurized outside source to apply adjustable pressure to the module until it reads 20psi. Note: take a 6 in piece of 3" PVC pipe, glue two end caps on it and place a tire valve stem in it and a small nipple with a rubber hose to the module. Install a pressure valve or use the one on your compressor/pump to pressurize this resouvoir and the module in a controlled manner. Do this slowly and take care to not apply extreme pressure to the module to avoid damage.
Read the voltage and you now know how high it must be to trigger fuel cut at the ECU. Many common automotive pressure modules will read 5 vdc but that can only be determined by manipulating the module to see what it does. Once you know this, you can fairly easily adjust this to reach the desired fuel cut. Some people even defeat the entire FC system but that is very risky on a expensive engine.
For a different turbo car project I built an adjustable voltage splitter circuit that takes the input voltage from the sensor and reduces it by using a fixed resistor and a adjustable resistor. It is a simple, adjustable, reliable device that can be spliced into the harness and arbitrarilly reduces the voltage seen by the ECU. Then with some trial and error, this will enable you to manually increase the level of boost that triggers the fuel cut to a higher value. WARNING - this can lead to engine damage if you increase boost to a level that either maxes out the injectors/fuel rail/fuel pump whichever turns out to be the bottleneck and/or causes detonation. It is guesswork to edge this up and somewhat unknown territory. With our engines the knock sensors will start pulling timing advance if detonation occurs but going too lean is bad news. You really need to install a wide-band O2 sensor in the turbo downpipe to monitor that cause it is gonna drift with atomospheric conditions every day. Normally the ECU will compensate but when you push the systems to their max fuel flow rates, they can no longer adjust. Simply putting in bigger injectors is not enough unless you also can reprogram the ECU. If you get that done, I want to hear about it as it has been a constant problem on the C-Klasse MB forum.
In my case I set my FCD to 18psi but my injectors max out at 16-17 psi. I use the boost controller as my first line of defense and the FCD as my 2nd. The final line of control and protection is the knock sensors. My car is set very rich also for safety. If I wanted to lean it out by a percent or two, I could safely run up to 18 psi on that system (it was set to 12 psi from the factory). Yours is different and the limits will also be different but there is usually a small safety factor that can be stolen albeit with added risk. At some pressure limit you will begin to over stress mechanical components such as rods, and head studs/bolts. It is a big guessing game to go there, lol -- You usually find those when you detonate at full boost unexpectedly and the pressures in the cylinder go up exponentially... have fun! You are breaking new ground. I am very impressed with it.
Irish