Cheap boost retard?
Ok so I think I have an idea for a boost retard unit.
If you have a voltage outputting intake temp sender, it could potentially be used as a boost retard unit if a MAP sensor is used as an interceptor.
If the temp output is used as the earth for the MAP sensor, earth is used as the voltage input, the output of the map sensor then contains both intake temperature AND boost information. This setup would see the voltage falling towards zero as the boost increases.
Now all I need to figure out is how to make the output of the map sensor equal to the input at zero vacuum, and change as boost increases, instead of it being constantly modified (atmospheric pressure is normally half way through the range on a 2 bar map sensor).
thoughts people?
cya Ben
*of course this would have an unknown effect on timing unless you had access to both the IAT sensor output data, and the contents of the Air temp/Ignition Timing table in the ecu. It may also reduce fuel input. But one things is for certain, if you make the computer think it is hotter, timing will be reduced.
Comments
Cheap boost retard?
IMHO modifying sensors in front of the oxygen sensor is useless as a long-term solution. The ECU will eventually "learn" around it... Let me tell you why.
You've got two operating modes in the ECU, open and closed loop. In open loop, the ECU takes the information from the intake sensors (MAF, MAP, TPS, etc.) and "guesses" how much fuel should be injected. Without the oxygen sensor, this is all it goes by (and would make "tricking" the ECU easy). However, when in closed loop, it then reads the oxygen sensor to see how far off the mixture is. The next cycle, it'll compare the current intake sensors to the previous cycle, and take into consideration how far off the oxygen sensor said it was. You can mod all the intake sensors you want, but eventually the ECU will adjust for 14.7:1 via the oxygen sensor.
You could try to force open loop mode, but ECU's are usually tuned to run rich when in open loop. Also, ECU's generally have tables that give a percentage of error between the TPS, MAF, and MAP sensors. In other words, if the TPS says the engine is WOT but the MAF says it's only ingesting 5CFM of air (for example) the ECU will throw a code and generally run like crap.
This is why most experienced tuners scoff at the resistor mods and "chips" sold on ebay, etc. It'll usually work for a while, but after a number of miles the ECU will tune around it. The only truely viable methods are a wideband O2 with narrowband emulation, or an ECU software tune.
Cheap boost retard?
Thats sometimes true Pinhead, but not always. My Tercel operates in open loop almost all the time. Only in cases where I am at [i]very[/i] light loads does the engine switch to closed loop. Its just the way that specific engine is. In my Matrix its hard to kick that thing into open loop. Different engine behaves totally different.
Cheap boost retard?
pinhead, you are forgetting that closed loop is for fuel control. I am talking about retarding the ignition timing under high load conditions only. The computer would be in open loop, and wouldn't ignore instructions from the air temp sensor unless it thought it was faulty. And the signal would be incorrect only one or two percent of the time anyway.
Cheap boost retard?
Hmm, interesting... I guess that's true. It'd be handy to figure out at what %LOD the computer switches to open loop.