closed loop, open loop, loop de loop-help

[greg donovan]

i need some help understanding closed loop and open loop mode when it comes to tuning.

what is the difference and what does sean at rallitek mean when he says that a OBD-I ecu drops into closed loop mode almost immedeatly.

thanks.

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edited to change open loop to closed loop in the comment from sean at rallitek.

[-K-]

Ok good question.

Closed Loop: The easy way to explain this is that the ECU and the O2 sensor go into a closed loop. The O2 sensor tells the ECU what the AFR is and the ECU changes the injector pulse to try to get a good AFR. This goes around and around as the ECU trys to keep an optimal AFR for low loads. The car is in closed loop when you are just rolling down the highway at 65mph. So you get better gas mileage and less emmisions.

Open Loop: The ECU uses different sensors to adjust the fuel. It takes the sensors input and looks up what fuel to inject off tables but there is no loop. The ECU looks at the MAF, MAP, TPS, RPM etc and decides how much fuel is needed. Max power at full boost is not great for mileage or emissions. Not good for emissions means newer cars try to stay in closed loop much more than our cars.

This is the simple answer.
I would not want you to get a Perfect Power unless:
1 You get it tuned by a pro.
2 You wait untill someone makes maps for your car and mods.
3 You learn everything you can about tuning and still want to mess with it.

Not saying you are dumb but I would hate for you to go out and blow up your engine.

[greg donovan]

i dont plan on adding any power to this car untill next spring. i have alot more to learn about turbo charged motors and plenty of time to do it. when all is said and done i may just leave the car stock as i cant really take advantage of the small amount of power it has in stock form. they are such fin cars to drive in stock form. so my focus may remain solely on handling.

i had an idea what closed and open loop were but that helps alot.

i have some really good people to help tune the car. but i want to learn as much as possible.

rallitek is planning a tuning "class" some time that will have some content available to those of us who are geographically challenged.

[greg donovan]

help me understand the benefit of this a little more please:

The OBDI is easier to tune. They drop into closed loop almost imediately!

is it because you can tune the heck out of the PP for open loop and leave the closed loop stuff alone and it wont need adjusting on the closed loop mode?

i need to learn ALOT about tuning. any tips on some tuning books out there.

when i realise just how much i need to learn i begin to think the car is just fine as it is in stock trim. that is definately the cheapest option but not nearly the most fun.

i have the basics down, i think.

more boost needs more fuel. more boost makes more heat. more heat is bad. more fuel will cool things down, as will an intercooler and water injection. advanced timing will result in more power but increase the risk of detonation. so we need to cool things down some more and add more fuel.

[-K-]

It's easy to tune for power when in open loop. Closed loop should be kinda self tuning, the ECU will try to get a good AFR.

I was way impressed with my car after I put in my AGX/H&R setup. Makes my car more fun to drive than my old winestone and it had a lot more power.

You can get a healthy amount of power over stock without tuning.
It's been a while but I think my 1/4 times were in the high 14's, a few tenths slower than my stock WRX. Turbo, AWIC, DP, More Boost.

If you are not doing much for a bit I would wait and see what the LegaCU does when it is finished. I think it will have more options than the PP because it's made just for the Legacy Turbo.

[Kelly]

Hopefully by next month, I'll have some maps ready for the turbo leg.

[greg donovan]

If you are not doing much for a bit I would wait and see what the LegaCU does when it is finished. I think it will have more options than the PP because it's made just for the Legacy Turbo.

is the LegaCU what is going on in that massive thread in the engine forum?

i followed that for a while but it got WAY over my head w/programming and stuff like that. im fine w/following instructions and turning knobs and stuff like that but programming is a bit of a mystery.

as far as tuning and modding goes i want to do it properly if i do it at all and i want to maximize the modifications.

Hopefully by next month, I'll have some maps ready for the turbo leg.

that would be really cool! how would having the PP mapped by you guys affect the pricing?