Quote:
Originally Posted by neal64ss
Just got caught up and subscribed. You are very good at explaining complicated things in a simple way. I hope you continue on with some info on tuning as this is where I have had trouble understanding the process.
|
*** Please learn to tune a stock engine first before making any mods! ***
Thank you, yes of course, I like interaction so I will sprinkle a little primer here for you. Not sure if you have experience with carburetors but for those of us who do, I sometimes use analogies and comparisons. Point being when I was learning I would look at a carburetor and go "oh carburetor" as in one thing one piece one system. Now when I look at a carburetor I go "hmmm, ok that's the choke, that's the idle circuit, that's the accelerator pump, those are the main jets, those are the secondary jets, that's the power valve circuit, etc" I now see it as a collection of systems.
So what does that have to do with tuning fuel injection. Well we may have traded a flat screw driver for a laptop but the goal is still the same:
Mix the right amount of air with the right amount of fuel, at the right amount of time.
Great, so how do we do it? Well first we don't say I am going to tune my truck, or tune my engine. We must divide and conquer and be more specific. So the circuit names may have changed but the car still goes through the same stages, and so we pick a stage or a phase and tune it, once done we move on to the next phase.
0. start and warm up
1. idle
2. cruising
3. acceleration phase
4. WOT (Wide Open Throttle)
5. deceleration phase
but before we even do that, let's ask ourselves are we about to polish a turd? let's think about it, as great as these little engines are, they are now turning 20 years old and 200,000 miles, do we expect their components to function as accurately as when they rolled off the assembly line, no of course not, so I am not saying let's go out there and replace every sensor on the engine, but let's at least make sure they are within spec first before we take to our laptop keyboards and start clicking and double clicking our mouseses
so let's do some basic checks, I absolutely love the following automotive thread I read about MAF sensor problems and what was done to fix it, please read it here
MAF Sensor values on Scanner
Things we should do a basic check on to eliminate glaring problems:
0. are there any
engine codes DTCs before we even start, ok let's be honest here you did an engine swap, did you even wire up the MIL light? Did you wire up the OBDII port, not being a wise guy I have spoken to guys who have not. Did you take the time to suppress all the benign codes like secondary O2s, EGR, EVAP, CATs, etc. so that you are not ignoring valid ones thinking it's just those.
1. What are the three key ingredients to great French cooking? ... butter, butter, and butter! Similarly what are the first things you should check and the easiest things to check and eliminate when your engine aint running right?
Vacuum leaks, vaccum leaks, and vacuum leaks. Do you know the five areas to check for leaks on your intake manifold? If your engine idles like crap but the problem goes away as you rev it up to say 1500 or 2000 RPM and it seems to drive ok, I bet you have a vacuum leak. Do you know how to find it?
2.
battery voltage (because now we are running electronic fuel pumps instead of mechanical and no matter what Walboro million dollar pump you shoved in the gas tank, if it don't get sufficient voltage it aint worth the money you paid for it) so is your battery 6 years old already, ha ha, what voltage does it read sitting still vs under load? what's the voltage at the fuel pump?
3.
spark plugs and wires - (see MAF article link above) remove all the plugs label them with a sharpie pen and lay them out in front of you and stare at them, even if you don't know what you are looking for, do they all match, are they all the same coffee color or are the middle four WHITE and the outside four BLACK? type of thing I recommend OEM plugs and wires, let's not try to outsmart the army of GM engineers here, periodic tune up should be a no brainer, plugs and plug wires as well as an oil change should be done before dropping the new engine in the old engine bay, ha ha - or I'm telling gramps!
4.
O2 sensor voltage - simple this should read between zero and one volt (.100 - .900) for the stock factory Narrow band O2s)
5.
MAP barometric reading - this should match the weather app on your iPhone
6.
fuel pressure - is this STILL within spec for your donor engine year make and model or is the fuel filter clogged or the fuel pump under performing, did you cheap out on the wiring and used what ever skinny wire you could find to wire in that new fuel pump? Did you ground it properly with a star washer to your thickly powder coated frame or POR15ed frame rail? Is it getting proper ground all the time?
7.
MAF - did you move it from the ugly black plastic snorkle by the passenger side wheel well and mount it directly on the nose of the intake? If you did that did you change HP Tuners to tell it where it's at now? If not then it's probably giving you inaccurate readings, no wonder the MAF gets a bad rap. Also our engines have an Intake Air Temp sensor in the same box as the MAF so when you move the MAF you also relocate the IAT, talk about confusing the PCM!
etc. etc. etc.
I don't mean to preach or sound condescending or like a smart aleck I just want us to be realists and encourage critical thinking so we can analyze and better understand the changes we are making and why we are making them, and not just blindly follow along what some knucklehead is telling us to do on the InterWebs