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Discussion Starter · #1 ·
Engine Management at War

I wanted to bring this topic to it's own thread (makes easier to search for) because I have been on .NET for a while and do not ever remember reading a topic deticated to this subject. I know folks have always said that a stand alone system is the way to go. I have always read hints and bits-n-pieces of why. But, no one has come straight out with the facts to back up their opinion. It's similar to all the times folks blew hints that there was no Santa Claus and but no one comes straight out with the true story behind it. Then, you hear the words from your parents and you now believe it. Below is a comment that Freelance wrote. I know what he wrote has to have some kind of truth to it because I had this same discussion with doublins about a week ago (reached the same conclusion). I would like to hear some other thoughts and info on the topic. I think this should scare every person who is using a piggyback system.

Freelance said:
The problem w/ the OBD II is that it is SOO dominating that it keeps on correcting your cars readings above and over the Greddy e-manage, so no matter what you do to the greddy the OBD II over corrects the mixtures that your greddy gives off. A way around it is to reset you ECU but even that won't hold for long, the OBD II keeps adjusting the cars settings to copensate for the over the top reading that the car is giving. You can keep resetting the ecu but it will keep trying to adjust the cars settings to compensate for the extra readings it is getting.
If this is the case, how do piggybacks work after a time frame as short as 48 hours? Is there a way to anticipate the OBDII's counter attack into your tuning? If this is such a problem, why do tuners keep offering piggyback's as an option?
 

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This will be an excellent post... great idea Mark.

I'm not the expert but I do know people have been working to keep a stable piggyback installation running for months and the OBDII keeps throwing wrenches in the works. As you drive the car around, the stock ECU learns your driving style on both a short and long term basis and adjusts the car accordingly.

The current "solution" is to reset the stock ECU by unplugging the battery... You have to leave it unpluged overnight so it drains both the long term and short term maps it builds. I might have this backwards, but when you just unplug the battery for 10 minutes the ECU will lose its short term maps (how it learns your driving style) but not its long term.

Unfortunately, even resetting the maps only lasts for so many miles before you have to reset again so this isn't a good way to release a kit.

You can skirt around all these issues by going with a stand alone management system such as the Haltech... unfortunately that means $$$ and non-shippablility so it makes the appeal of some kits (like the superchargers) very lackluster.

This is all based on my limited understanding of the issue... I've been doing a lot of research into this and spoken with quite a few knowledgeable people.
 

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He's pretty much right. The only real way to do it would be standalone.

For example...fuel

You can tell the piggy unit to dump more fuel in, but the O2 sensors will read that the car is running rich. This'll cause the car to cut back on fuel to run .


Tuners do it for cost reasons...and simplicity reasons.

That's why we should all go up to the sticky and call AEM.
 

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Discussion Starter · #4 ·
Are there any current piggyback owners who had their tuner specifically tell them to reset their system (on there predetermined date schedule)?

If so...what was the suggested frequency?

I know I was never told I needed to, or should, unplug the battery every so often. Then again, I bet this happens anyway because they have to get rid of that CEL :lol:
 

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Awesome post!

I have a couple of question about the stock brain.

1. Does anyone know if there's a limit to how much the car can adjust the fuel by itself? I would imagine that the manufacturers would create a limit to how much the fuel is adjusted by the O2 readings, since those can go bad themselves. Hence maybe a +-5% variance?

2. And how about bugging all of the O2's like the headers from toyo? Wouldnt that "fool" the brain into thinking that everything is running nice and strong?

I'm just running on an assumption that everything is close loop, so as long as the computer is fooled, it shouldnt be hard to control it.
 

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Discussion Starter · #6 ·
youpeopleareweird said:
I'm just running on an assumption that everything is close loop, so as long as the computer is fooled, it shouldnt be hard to control it.
The positives and negatives of a closed loop vs open loop system...another good topic...
 

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I would love to be a part of this post. However I'm leaving for a mini vacation until the 30th, so I won't be able to. Sorry, I guess I'll have to start my own when I get back.
 

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Piggy backs are cheap.

Especially SRT's non user-friendly propprietary POS. (sorry...just having issues w/ my shifting and can't get it tuned anywhere else) This is why the kit sells pretty well I think however, I don't think the price justifies the savings you should have....I mean a Tec3 is like what $1500-2g's ish? Piggyback = $500 or less although the kit prices don't reflect this much in savings.
 

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So here's my little 2pennies on this subject. Please feel free to correct if I mistate anything.

As you guys know I've had a s/c and a turbo w/ an emanage. I've also done a lot of tuning on my own and a lot of datalogging on my own with the emanage and a Palm w/ Auterra obd2 software. After talking w/ [email protected], doublins, [email protected], other various people and a lot of digging on my own I've come up w/ the following. I've proven it as true as well even recently on a dyno run of a car w/ a safc and a turbo.

-Basic operation-
---Reset ECU-
----As soon as you start it up the car starts logging O2 sensor data while running in closed loop. At this point LongTerm Fuel trims(which affect open loop) are around zero.
----Then the ecu see's that the car is maintaning 14.7 well and is only having to pull 5% fuel out in closed loop. After a while of logging(20 -30miles) the ecu starts to calculate LongTerm FuelTrims and will cut or add fuel based on what the shortterms are doing. For instance in this example the car is pulling 5% and will pull 5%on the longterms(I'm pretty sure but not possitive of this).


--Enter Piggyback
------Premise of closed loop in my understanding: If you add fuel to the car while in closed loop the ecu will adjust and pull out fuel.

With this premise you can see that if you do not completely know where the stock ecu goes into Open loop you will not be successful.


Example of the problem(limited to a couple variables to make it simpler)
--Say at 3000rpm and 40%tp your car is in closed loop, but because you don't know the closed loop extents you are trying to add fuel at this point. Everytime you add fuel your ecu will pull it out and the two will fight only the IS ecu is a bitch and will win everytime. You can see that by doing this your ecu will keep pulling fuel and pulling fuel until it's happy. By pulling the fuel to make it happy you will affect the longTerm fuel trims and will lean it out on the top end. This is VERY bad and will eventually spell BOOM!

[theory/opinion]
It is my premise that a 7psi kit is fine as it will never build enough boost in closed loop to worry about, but you HAVE to know exactly where open/closed loop operate. Without that you are in trouble. Now there are a couple other ways such as fooling the ecu and obd2, but they are involved and haven't been done yet on the IS.[theory/opinon]
 

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Discussion Starter · #12 ·
TBKO said:
fuct said:
DAMN, and just the person i wanted to hear from about this issue. have fun on your trip!!!
Yeah, I'm going to be thinking about this post the entire time I'm gone.
Jeff/TBKO uses a piggyback. So...it must be able to be fooled. Just as IS_Dude speculated.
 

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TBKO said:
Yeah, I'm going to be thinking about this post the entire time I'm gone.
Stop thinking bout my x-gf's ass.
 

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redline814 said:
TBKO said:
fuct said:
DAMN, and just the person i wanted to hear from about this issue. have fun on your trip!!!
Yeah, I'm going to be thinking about this post the entire time I'm gone.
Jeff/TBKO uses a piggyback. So...it must be able to be fooled. Just as IS_Dude speculated.
nope, nobody's fooled it yet that I know of.
 

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Discussion Starter · #15 ·
IS_Dude said:
redline814 said:
TBKO said:
fuct said:
DAMN, and just the person i wanted to hear from about this issue. have fun on your trip!!!
Yeah, I'm going to be thinking about this post the entire time I'm gone.
Jeff/TBKO uses a piggyback. So...it must be able to be fooled. Just as IS_Dude speculated.
nope, nobody's fooled it yet that I know of.
Damn. Back to reality... :lol:

So...
If several tuners use a piggyback system, there must be some sort of way to tune it to a "safe" parameter. You mentioned knowing when the car hits open loop vs cloosed loop can play a large difference in the tuning outcome. Maybe this is the key and all tuning revolves around such?

I am not fully wise to open loop and closed loop world (other than my brief schooling by doublins). Can anyone share what sends the car into one or the other.
 

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Discussion Starter · #16 ·
Another tangent I am going to head out on...

Could the demand for a cheap F/I kit for the IS300 be what is causing tuners to "settle" by using a piggyback system? Is this because if not all tuners jumped on the bandwagon, they would lose out an allot of potential customers? Could this be all about money and selling products?
 

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I have emanage and my car works great. I havent reset the ecu in months.

I'm not using the ignition harness though so I haven't messed with my timing at all.

No misfire either in months. I just always give my car about 15 seconds after I turn it on. A little while longer if it's pretty cold.
 

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Neo302 said:
I have emanage and my car works great. I havent reset the ecu in months.

I'm not using the ignition harness though so I haven't messed with my timing at all.

No misfire either in months. I just always give my car about 15 seconds after I turn it on. A little while longer if it's pretty cold.
what kit do you have?
 

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Discussion Starter · #20 ·
IS_Dude said:
[theory/opinion]
It is my premise that a 7psi kit is fine as it will never build enough boost in closed loop to worry about, but you HAVE to know exactly where open/closed loop operate. Without that you are in trouble.[theory/opinon]
When I talked to Mo/SRT (this Sunday) about my car and its weird acting up, one of the things he mentioned was to make sure my boost was set at 7psi or lower (until I get it to the shop for him to look over). Perhaps he knows this 7psi rule/conflict...as did TBKO when they released their original kit back in the day?
 
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