Explanation of piggyback and stand alone needed

[kuruption1983]

supz all,
I have been reading so much about turbo setups recently, and i have come to 2 concepts very often. One is the piggyback system and the other is stand alone fuel management. I have no idea what exactly these do, but i know there are several cars that have both and have to do something with the amount of fuel injected in cylinders, and some have just one of them. Also i was reading that one of these controls the timing of the engine, the thing that doesnt make sense to me is that, the timing of the valves are controlled by camshafts and not electronically controlled, so how can an electronic device control the timing.
oh and one more thing that concerns me is boost controllers, the boost created by the turbo manifold does depends on the revolution power created from the exhaust side of the turbo and the size of it, so how can a boost controller take control of the boost; can it increase the boost on a small size turbo. I also need some explanation on what T2, T3 or T4 turbos mean and what defers them from each other; is there any other kind of turbo bigger than this that i dont know of ??
Will appreciate anyone's input on this matter, we can post this in the FAQ section if inputs are enough.

[mazdamaniac]

Each and every question you just asked is answered in some detail in the book "Maximum Boost" by Corky Bell, which you will find highly recomended here and elswhere.

That said...

A stand-alone engine management system replaces the engine control functions of the stock computer module in your car with a programmable unit that can be customized to control your engine adequately in response to modifications made to the drive train.
A "piggy-back" system is a device that coexists with the stock computer to give some additional level of control (but not complete like a stand-alone system) of fuel delivery and some times ignition timing, which is the "timing" you have heard referred to - it has nothing to do with valve timing.
Boost control on a turbine-driven supercharger (turbo) is effected by modulating the vacuum/boost signal sent to the wastegate actuator.

[tiburon]

ok where to begin?

Piggy backs and stand alones: A piggy back unit works together with your stock ECU to run your car. It dose this by intercepting values and changing them to get the desired result from the ECU. While this seams like a nifty idea, its never that easy. Most of these units cause choppy changes and work particularly funny with mazdas. Stand alones(like haltech) completely replace the ECU and take full contol of the motor. These use their own sensors and your programed settings to run the motor. With enough time, stand alones can be made to run just as well as a stock ECU(if not better) with higher performance. Stand alones are very adaptable unlike piggy backs which usualy limit the amount of change from factory settings.

Timing: Ignition timing and valve timing(your timing belt/cams) are completely diffrent things. "Timing contol" is refering to changing when the spark fires in the cumbustion chamber. The more "advanced" in crank rotation the spark fires is the more power your generaly going to make. The problem is if the timing is to advanced detionation can occur produsing extreme heat and stress. Good timing control is needed to produce the most out of your motor.

Boost contolers: Boost controlers don't really contol boost, they contol your wastegate. A wastegate is like a little trap door that lets exhaust gasses pass by the turbo without going into it. As your boost pressure increases your wastgate will start to open letting exhaust pass it by. This action will limit the amount of work the turbo is aloud to do producing "boost". Every wastegate has a preset value set by a spring, sence there is no easy way to quickly change out a spring on the road the only way to change when the gate opens is to change the amount of boost the wastegate sees. A boost contoler is nothing but a little valve (or electronic solenoid) that lets some air out between the wastegate and the pressurized intake. So while your motor is seeing 10psi your wastegate may only see 5 and stay closed.
T2, T3, T4: These are standard garret turbo sizes, but are little more then a name. Not all T3's are created equal. Some T3's will produce better results then their larger T4 brethren, it all depends on the specs and your set-up.

Hope this helps.

<small>[ October 02, 2003, 02:35 AM: Message edited by: RiceRocket666 ]</small>

[tiburon]

damn I type slow.... you beat me by a whole 17 mins

[kuruption1983]

Aight, there is one question that remains which might have nothing to do with mazda engines FI, but how do they turbo or supercharge a carburator engine, such as a Z24 from nissan; and what makes more sense, changing the entire carburator or FI; and what would a bigger carb do, i mean what does it have different from the OEM carb. Another question that remains is, do you always have to change the amount of fuel delivered to the engine when building a turbo setup, by such ways like getting bigger injectors or bigger pump or changing the fuelrail (i dont know what this does)
This was just an absolutely amazing write-up which i think many people are going to ask over and over. many appreciations to both of you guys. I think this calls for barry to add it to the FAQ section. And I think if we can gather enough info here, we could write our own book.

[ryanlindenberg]

Another question that remains is, do you always have to change the amount of fuel delivered to the engine when building a turbo setup, by such ways like getting bigger injectors or bigger pump or changing the fuelrail (i dont know what this does)

yes. basically air + fuel = power. the turbo is forcing more air into the motor, in order for this air to make more power you need more fuel. if you don't add fuel you will have a lean(not enough fuel) condition which will lead to detonation(which is bad). However, since the turbo only starts generating boost at a certain RPM range, you don't need the extra fuel when at low RPM. there are many ways to control the fuel rates at differing RPM ranges. Some of them are the stand-alone, the piggy-back, and a rising rate fuel pressure regulator (RRFPR). a RRFPR increases the fuel pressure when the turbo begins to produce boost. when you are putting more fuel into the motor, often times the OEM fuel pump can't keep up with the amount of fuel needed. this is why you put in a high-flow one. if you don't you could run lean. same thing with the fuel rail, some of them don't flow very well and won't be able to keep up with the fuel needed.

i mean what does it have different from the OEM carb.

different carbs have different flow rates. you want to get the carb that is closest to the ammount of air that will be going in the motor. i have no idea how to calculate the flow rates(cfms) by the way. hope this helps

[Manach]

Curious like that..

Is there something that can adjust the fuel feed automaticaly with the detection of a O2 sensor?

Of you want 12:1 Air/Fuel ratio all the way, is a program capable to detect that, and adjust the fuel accordingly? What is the name of such a tool?

Thanks!

[OsoSlo z28]

some stand-alones have something like that. it has a function called "closed loop" which takes the O2 sensor's reading and lengthens or shortens the injector pulse therefore taking away or adding fuel. this can only be done to a certain extent which is why good tuning is needed before hand. if people are serious about effecient tuning, a wideband O2 sensor is suggested. the lamda sensor is good, but comes nowhere close to the widebands precision. this is why dyno's use a wideband.

<small>[ October 03, 2003, 10:42 PM: Message edited by: cre8v mx3 ]</small>

[kuruption1983]

Originally posted by cre8v mx3:
This can only be done to a certain extent which is why good tuning is needed before hand. if people are serious about effecient tuning, a wideband O2 sensor is suggested.

could you please explain tuning turbos a bit more and exactly what is involved.

[ryanlindenberg]

could you please explain tuning turbos a bit more and exactly what is involved.

basically tuning is trying to get the fuel mixture right through out the entire RPM range. you don't want it lean or rich. too lean will get you detonation, too rich will wash the oil off the cylinder walls.

[Manach]

Originally posted by ryanlindenberg:

could you please explain tuning turbos a bit more and exactly what is involved.

basically tuning is trying to get the fuel mixture right through out the entire RPM range. you don't want it lean or rich. too lean will get you detonation, too rich will wash the oil off the cylinder walls.

But if you go into VACUUM, you'll want one setup, if you BOOSTED, you'll want a different fuel map..

That's why I asked for one that adapt itself accordingly..

[OsoSlo z28]

in a fuel map, you have many points to tune. from vacuum to full boost and in 500rpm incriments(for the hatlech). the ecu takes your fuel map, what rpm you're at, and the map sensor's reading to determine what the fuel supply should be.

[Manach]

Originally posted by cre8v mx3:
in a fuel map, you have many points to tune. from vacuum to full boost and in 500rpm incriments(for the hatlech). the ecu takes your fuel map, what rpm you're at, and the map sensor's reading to determine what the fuel supply should be.

Humm.. Can a APEX'i S-AFC do that?