Re: Engine pressure analysis tuning
The company as pictured below (TFX) low cost system is $2495 (2 channel). The LCS 4 channel is $3695. Of course there is a 5 channel with live display that runs $3995. You also need an plug (you would likely want your regularly run plug) modified with a pressure transducer, which costs $1295. I don't got that kind of money floating around.
The tech was good enough to email me some specifics about why their data analysis system is so good. It is kinda cool to be able to scope MAP, Exhaust and combustion pressure to make determinations, but I already have 2 of those sensors. A high resolution crank sensor might be kinda nifty, but really we can run the crank sensor at TDC or properly locate it and do the calculations off of that based on time to the next TDC (720 degrees) to know the pressure/piston relationship. Throw an inductive spark probe on the plug wire, graph the MAP, primary ignition pattern, through an exhaust probe in the tailpipe and you have yourself a party! Heck if I had an 8 channel scope instead of 4, you could add the wideband in real time and suprise yourselves on how sensitive the sensor is compared to what the Datamaster or gauge is showing you.
The bottom line is that via the SAE website and a few (hundred) bucks, I can get enough engineering papers to work out a better understanding of MBT vs Mass Fraction Burned and come up with a good way to calculate not only where best mechanical advantage over the crankshaft occurs, but a good idea where the fuel is being consumed as well.
The additional components to make this work for me is simply the fiber-optic pressure sensor incorporated into one of my plugs and a power supply. While it won't do the math for me, it will give me (within reason; the sensor inside the plug shell will likely "soften" the pressure waveform a bit depending upon plug angle, depth of plug, electode shrouding and such..) a good waveform, triggered to TDC that I can use to determine where combustion pressure is compared to crankshaft position. If I understand correctly that MBT is usually found when approximately 50% of the fuel shot is consumed at around 4-16 degrees ATDC, then we should be able to fine tune for a cylinder pressure peak that is not only putting pressure on the piston to provide maximum brake torque without knock (and at much lower amounts than the knock sensor will ever be able to identify), but also that pressure isn't wasted into the intake track due to reversion and/or backpressure, nor is it burning out the exhaust valve or being held up by a restriction due to mechanical obstruction or exhaust collector tuning. That is where the MAP sensor and exhaust pressure transducers come into play. Once again the timing of that would have to be figured out, which is why some should hit the easy button and pay for the software. I feel that 1/3 of the cost will get me 80% of the way. I doubt that I would fiddle with header collector tuning or intake runner tuning, but if I was running a 11.00, I probably might.
A Pico scope is nice, I run a 4 channel from ATS which is pretty good. I also have cylinder pressure transducers, vacuum transducers, exhaust pressure transducer, primary and secondary ignition attachments, high and low current probes and such to keep wires wrapped all around my legs, arms and the occasional fan blade....
I used to connect the current probe to measure relative compression, but found it was just as reliable to watch AC voltage during cranking since it is also just a representation of the actual cylinder pressure (and starter condition). There are a few other benefits as well. Here is a waveform that I snapped outside at near 30 below. This car had been to a number of shops and nobody could get the OBDII monitors to set to complete. Long story short, I went outside to the car that had just pulled up to the office, hooked up my scope leads to the battery, disabled the coil and cranked it over. 30 seconds later I told her how to fix her car.
You can see the battery voltage drop to about 8V when it initially cranks over. That is enough to cause an ECM reset, which clears the monitors of course. Since this vehicle needed to drive-cycles to complete the monitors, every time it was restarted to run the second drive-cycle it reset. You can also see the battery voltage was low KOEO, but it was charging over 14V running......
Scopes and their accessories are awesome. I think that while this transducer will not only good tuning capabilities, but will also be able to identify real knock from "phantom knock".
If it means getting the transducer to Nats or not, I might get it dropped-shipped to the hotel or to a friend to save one or two days travel time.
