Iceman1

i know both of these are intake air measurement methods... but how does Alpha-N (throttle position based system) interrelate with a standalone or the ECU? is an alpha-n system part of the ecu? or is it a seperate of the ECU? or is it a "feature" of a standalone ? if you know a link to detailed info, that would also be great.

thanks.

Fabrik8

As far as I know, alpha-n is just a method of minimalist sensor open loop management. In closed loop operation, the ECU corrects parameters based on it's sensor inputs in order to try and achieve it's optimum A/F ratio and other stuff. In open loop, the engine just does what you tell it based on RPM, throttle position, etc. This is what most race engines use, and is one of the reasons why they have to be slightly tweaked when the weather changes. The ECU doesn't have much latitude to correct itself, it just runs according to it's tuned parameters..
Alpha-n sucks usually is done with race engines on race cars. Supposedly it sucks for idle, part throttle driveability, and general street manners.

Are you sure you aren't talking about a speed-density(MAP) system as opposed to a MAF-based system? Most/all Hondas use a MAP based system, and if you put the ECU in open loop mode, and disabled/removed a few sensors, you'd get alpha-n.

Iceman1

thanks... ok... i guess what im aksing is that, an MAF is a seperate sensor that sits in the intake stream and tells the ECU how much air is coming in...

i understand these alpha-n race engines have no MAF sensor... so is "alpha-n" just an integrated table-based component of the ECU... or is it a seperate component (hardware) connected to the throttle that contains throttle position based air/fuel maps for the ECU... and where does a standalone fit in to this chain of processing...

thanks..

Fabrik8

Alpha- setups use a MAP instead of a MAF.. and it's not a component of the ECU, it IS the ECU. Kind of like telling your home PC to run DOS instead of Windows. It's the same computer, but it's running a different way.
alpha-n is just the name of the type of management they're doing. I'm sure alpha and n have some significance to something that is measured, but they could have called it something like "open loop with almost no sensors". Anyway, alpha-n schemes are done by the ECU, and a standalone could do it quite easily, because of the programming flexibility. That's the big benefit of standalones, they are made to be used a lot of different ways depending on what type of setup you need. Alpha-n setups use MAP (manifold absolute pressure) sensors instead of MAF sensors. If you measure the pressure of the air, and the temp of the air, and you know how much air the engine ingests at a given RPM, you can tune for that. A MAF-based system just measures the quantity of air coming in, hence "mass air flow"..

You're not grasping the simplicity of alpha-n though.. If you take a MAP based car's ECU (like a Honda), make it run in open loop mode (most tuning software allows for that), disable all but the really important stuff (like the TPS, MAP, RPM, etc) and tune the maps to run under the conditions you want to run, you've pretty much just made an alpha-n setup. Most tuning is done open loop anyway because they ECU won't try to correct or compensate for anything while you're trying to tune it. The simplicity is because that's all a race engine needs, it doesn't have any emissions stuff, and consistant peak power under race conditions is more important than making sacrifices to perform at less than peak power but under all possible conditions.

I'm having a hard time explaining this, I'll have to give you a crash course in how engine management works if you don't understand..

Iceman1

ahhh... thats exactly what i was looking for.. thanks... im no expert but i understand what you mean... my BMW is on a MAF system, and I kept thinkin of the actual sensor that sits in the air stream as the above mentioned "component"... yes i understand the simplicity of alpha - n... see, the M3 CSL, sold in europe as a street car, employ's an Alpha-N based ECU... (cause the car is ususally used by race teams for the DTM race circuits) and i was trying to understand how it works... i guess BMW gave the tuners of that car an easy access point (the alpha-n based ECU) to easily tune the car for racing from the getgo... makes sense..

so if i buy an AEM or TEC3 for a honda, it can be configured it to run in alpha-n mode if i want to for a race setup... or it can be configured for MAF or MAP mode (with all sensors) if im looking for a street setup right?

thanks for the info...

Fabrik8

It should be able to be used like that, yeah. YOu'll have to get more info and make sure they can run in open loop mode. This stuff will all be specific to whatever ECU you get, so make sure before you buy it. Talk to people that have similar race setups that you have, and see what they're doing..