RETed

Yes.

You see anything wrong with that?



On a side note, we managed to blow up a built 13BT that didn't get a hint of problems on the EGT gauge, and I doubt any wide-band would've caught it. It was an ignition timing (set-up) problem that was firing about 20-degree retarded. Yet another example of what the wide-band would not catch.





-Ted

j9fd3s

thats why you gotta not only zero the timing but make sure that when its unlocked, reality agrees with the computer. ie when it says 5btdc at idle that its actually at 5btdc with the timing light yada yada. in my experience you can't trust that its gonna be right, just cause

Fd3BOOST

I bought this book a few months ago. I thought I would share. It's a good book for someone interested in learning how to understand efi and tuning.







http://www.amazon.com/exec/obidos/tg/detai...061461?v=glance

psyclo

I just bought that one not long ago, its good but I like 'How To Tune and Modify Engine Management Systems' by Jeff Hartman. Its thick, and detailed. Covers everything from how to choose an EMS to tuning to intake design.

Turbo III

Sorry but I thought the Jeff Hartman book was about the dumbest things I've ever read. It is about the same as magazine advertisements in technical detail and doesn't actually tell you anything about how to perform tuning, just how the systems are setup.



My preference is the Corky Bell books;

http://www.amazon.com/gp/product/185960691...=books&v=glance



this one;

http://www.amazon.com/gp/product/083760160...=books&v=glance



and I can't find the last one but it's called "4 stroke performance tuning" by A. Graham Bell although this one goes into great detail on piston engines, it does help with the why even though it spends a lot of time on the how as well.

toplessFC3Sman

I found this statement a bit confusing, and thought Id clear it up, because timing usually refers to when the spark plug fires, not when the fuel is injected. Since we are not dealing with direct-injection engines (diesel, mazdaspeed6 2.3 liter etc), the precise moment of fuel injection is not nearly as important as spark timing.



In regards to spark timing when running a N/A engine, it is directly related to the engine speed, and to the afr. Regardless of what speed the motor is spinning at, at TDC there is still the same volume of fuel and air that needs to be burned. But the faster the engine speed, the less time the motor spends at TDC. Ideally, the spark plug would fire at TDC all the time, and combustion would be instantaneous. However, it is not, and there is a finite time (the flame propagation time) that it takes all the fuel in this fixed volume to burn. As the fuel burns and the hot gasses expand, there will be a point of maximum pressure. The whole idea of advancing the timing at higher RPMs is to anticipate how long it will take for the fuel to burn and subtract that amount of time from the point at which you want maximum pressure (generally right after TDC). The flame propagation time depends on the rate of compression (or expansion), the afr, the pressure of the chamber, the temperature, humidity and a few other things, and these would affect how much the timing is advanced at any one time.



Now for fuel stuffs:



All the fuel is initially liquid at approx ambient temperature, and when injected into the intake runners, it uses the heat from the air and hot metal of the intake runner itself for vaporization to become a gas. This cools the entire intake charge. The more fuel you inject, the cooler the intake charge will be b/c more heat will be used for vaporization. This is the same principle behind water injection, but it just happens naturally with the fuel. all of this is in the intake manifold, and then the mixed charge just waits to be sucked into the chamber. This doesnt have much to do with egt's tho. Because of this necessary waiting for the valve to open, or for the port to become clear, the timing of the fuel injection is not very important, just the amount injected.



Except at idle and very low load conditions, an engine is never even near running on a stoichiometric mixture (14.7 lbs air vs 1 lb fuel => 14.7:1). Just for clarification, a stoichiometric mix is dictated by the chemistry of gasoline and the amount of oxygen in air, such that there is the perfect chemical ratio of oxygen and gasoline to only produce CO2 and H2O. This will produce the most power for a given amount of fuel, because the enthalpies of formation for CO2 and H2O are the lowest of any realistic byproducts of hydrocarbon combustion (aka, they have the least amount of chemically stored energy, so more can be released). This creates a lot of work, but also a lot of heat, and because many of the components of the engine are only rated up to a specific temperature, at higher RPMs where more gas would be burned at a faster rate, more heat would be output than coudl be dealt with by the cooling system and the whole engine could excede the heat rating of various components. All of this extra heat would definately create hot spots and increase the pressure of the charge inside the engine, creating great conditions for pre-ignition or detonation. These are basically normal combustion explosions that are caused not by the spark plug, but by the principles off of which a diesel engine operates (compression ignition, not spark ignition), or by hot-spots in the engine that ignite the charge. Since they would most probably occur before the spark as the charge is compressed, the force of the explosion tries to push the piston or rotor in the opposite direction in which it is moving, causing knock, ping, and all sorts of bad-ness. Thus at high RPMs, you do not want to run a stoich mixture, and all engines are tuned away from that, and more fuel is injected. This is done because not only of the effects of fuel vaporization on the intake charge temperature, but because as more fuel is injected, it actually serves to quench the explosion inside your engine. There is more fuel than the air can completely burn, and because of this, not all of the energy of the fuel is released, so temperatures do not get as high. Some carbon monoxide gets formed, which has a greater amount of chemically stored energy, some fuel only gets partially burned, and overall less energy is released. This is not good from an efficiency point of view, but is wonderful if you dont feel like melting or blowing up your engine.



Stock, under the conditions described above, all gas engines run more fuel than necessary when compared with stoich. However, from a tuning standpoint, the terms "rich" and "lean" are relative to the stock fuel map. Thus, as the engine runs "leaner", it is actually running closer to stoich, and much hotter than otherwise, resulting in higher egt's. Conversely, as more fuel gets injected, it takes longer to burn because of the lack of oxygen, and ends up partially burning in the exhaust, increasing egt's even though less overal energy is released. Thus, for proper tuning, you want to find the middle ground where the engine is running coolest but still producing decent power.



Thats about all the depth I have time for right now, time to get to class (thermo incidentally). Hope this is helpful.

tunerx

What I have learned and seen on many cars and from factory training by the auto manufacturers. When you put a AFR in a factory stock car in front of the convertor you will see a very rich mixure. Richer than is neccesary for maximum power and safety. the reason for this is the catalytic convertor. If the factory ran the mixture at 12.1 or 13.1 on NA they high exhaust temps under full load would creat temps in the convertor would cook it and cause it to self destruct, Why you see high convertor failure on cat cars with mods. The eccesivly rich mixture flames out or shuts the cat down while at full load to keep it from self destructing. As explained to me by a factory engineering rep.



Bill

toplessFC3Sman

yea, thats also another concern of automakers... getting the cats to start working asap and keeping them functional. Cat. converters have a small range of temperatures in which they work efficiently. If the egts are too cold, the cat just doesnt work; it doesnt have the residual energy required to continue to react the exhaust to remove harmful emissions. If they get too hot, this starts to break down (or melt, depending...) the cat, which will result in a blocked exhaust, an under-car fire, or other nasty stuff. So extra fuel is run to cool the engine operating temps, and thus manage the egts.



This is especially apparent on start-up. Since the cat is cold, the ECU runs an accelerated warm-up, essentially burning more fuel than necessary to warm up the engine, exhaust, and cat to get it to operating temperature more quickly. This sucks for fuel consumption, but due to the emissions standards that the car needs to meet, it is the most expedient way to do it.



A lot of stock engine tuning is basically compensating for the emissions system, not trying to get the most power out of the engine.

Tomoya

Wow guys lots of useful information here!



Sadly to a tune noob like me... its hard and time consuming to swallow all of this in a short time.



My question is. Is there a way to tune your afm without a standalone EMS? (Im talking about an FC Turbo) I have this Blitz M.F.C.S (multi fuel computer system) that came with the car when i bought it, but it was never hooked up. Appearantly its a piggyback of somesort. Will I be able to use that and tune?

toplessFC3Sman

In re-reading, I realized I was wrong on a part of this... detonation is not the same as a normal fuel combustion in the engine. A normal combustion is actually a really quick burn, starting at the spark plug and spreading outwards, whereas detonation is an explosion, when all the fuel (experiencing the same temp and pressure) reaches its threshold and simultaneously explodes, causing shockwaves and damaging engine components, especially apex seals. So to clarify, detonation is an explosion with a shockwave and a very sudden, severe pressure spike, and preignition is a burn with a flame center (some sort of hot-spot) that occurs before the spark