Experience with Piggy Back ECUs

[Normal_aspirated]

Can read some of the threads here:

 

http://www.mycarforum.com/forum/gforum.cgi...%20back;#326295 http://www.mycarforum.com/forum/gforum.cgi...%20back;#220489 http://www.mycarforum.com/forum/gforum.cgi...20back;#565604"]http://www.mycarforum.com/forum/gforum.cgi?post=363965;search_string=piggy%20back;#363965

 

http://www.mycarforum.com/forum/gforum.cgi...%20back;#326295

 

http://www.mycarforum.com/forum/gforum.cgi...%20back;#220489

 

http://www.mycarforum.com/forum/gforum.cgi...%20back;#565604[/url]

[Cyrix]

thks bro...very interesting....been to N2CS recently....boss rtecommend

some ECU ROM to put on my ECU...did not really catch what he was referring

.....whether he intro a piggyback or add on some memory for my existing

ECU....any ideas????....can the existing ECU actually add more ROM like

the PC adding more RAM like tt???....quite interested to know.....

can enlighten???

[Modeldriver]

Hiya... my understanding of things is basically the ECU is just like what you said, a computer. It has series of programs to control the various functions of the car, one of which is the amount of fuel to inject based on sensor readings of the trottle position and the air flow.

 

Piggy backs have its own computing to decide on how much fuel to put in based on the same sets of inputs (air and trottle). The 'common' one is the SAFC/SAFC-2/VAFC from Apexi. The more thoroughbred type are Buddy Club and HKS. Main difference is the number of steps the tuning can be done (by rpm steps).

 

The ROM upgrades is another approach. Either by plugging in a chip or doing a software override - not unlike your PC's bios firmware upgrade. Not exactly a piggy back. Software reprogramming takes more to 'undo', while piggy backs are bolt on. In addition, piggy backs can be transferred to your new car (although so far it's mostly for Jap cars, might not be so easy to transplant to contis).

 

Hope this helps.

[Cyrix]

bro...me finally understand more liao....just wondering...how much roughly is the HKS and Buddy Club piggyback...am i rite to say tt the piggyback can be transferrable to other cars and reprogram to suit the other car or a certain piggyback is only suited to certain cars???....like suspension like tt??....most impt of all now...which is the beta deal????....cos me went to N2CS recently....they offer to upgrade my ECU ROM....but forgot to ask how much...does it mean tt a ROM upgrqade is not transferrable???....

[Silver_z]

Greddy Emanage with all harnesses.......

 

(1) Control air/fuel

(2) Control Ignition Timing

(3) Control Additional Injectors

(4) Control Boost

 

Results:

(1) On Crank HP improve from 200bhp to 320bhp

(2) FC increase tremendously from 9km/L to 6km/L

(3) Can fight against EVOs and more.....

 

Above from a 1.8L DOHC VTEC to a 1.8L DOHC VTEC Turbo.

 

Not my car..... My dream only.....

[Zrun]

Piggy back will control a/f mixture, and if you are lucky, it can also fine tune ignition timing. For example, E-Manage can control both timing and af ratio. SAFC can only control AF mixture.

 

Piggy back systems are extremely simple device, and all they do is to increase/decrease ECU's injector signals. As piggy back system does not work in close loop, ECU will eventually offset the settings and your car will drive normally.

 

Piggy back systems is only good for altering open loop settings. i.e if you don't go 100% WOT, you don't feel the effects of piggy back system.

 

 

Another shortcoming of piggy back is that it cannot alter the signals too much, usually + or - 20%. If you have turbo setup, +20% will not be sufficient for your usage.

 

So, emanage has option for additional injector support, however, the problem with additional injector is that you do not really know if the fuel is evenly distributed.. It is always better to go larger injectors.

 

In fact, there's no need to tune close loop cycle, because your ECU is far more advance than any piggy back units, and it will make the car run at near max fuel economy and lowest emission. It is when you stomp on the gas, the factory ECU will ignore fuel economy/emission and use a preset mapping.. This preset mapping is good for a stock car, however you might want to tune it when you mod your car.

Edited August 24, 2004 by Zrun

[Zrun]

Most piggy-bags "hijack" the airlfow sensor signal and fool the ECU to to believe what it wants to do. Good tuners using dynos will give best results. Some newer piggy-bags can hijack the O2 sensors to prevent overriding by the ECU.

 

From what I know, piggy back systems does not hijack airflow signals, it uses airflow signals, rpm, throttle position to come up with a value to add or subtract to ECU's signals.

 

 

Not sure if any piggy back system hijack O2 sensors. Usually, O2 sensor is very critical component, if it goes out of range, it means something is seriously wrong in the engine.

 

Usually, people hijack/simulate the 2nd O2 sensor which only indicates the effectivenesss of the catalytic converters. They leave the 1st O2 sensor alone..

Edited August 24, 2004 by Zrun

[Cyrix]

hiya bro....after listening to ur speech....does it mean tt the piggyback is

useless as the ECU will override it???....so does it mean that a replacement ECU is the

way to go to achieve all the control needed? btw..how do u define open loop???

does it varies from car to car's ECU??? any idea an EK4 is open loop or close loop??

Edited August 24, 2004 by Cyrix

[Zrun]

Open loop vs close loop.

 

Close loop means your A/F ratio will be maintained at 14.7:1, perfect for emission, but not perfect for power. The computer will constantly alter the fuel to 14:7.

 

Open loop means your ECU detects you want max horsepower, usually trigger by 70% or 100% throttle position (accelerator position). In this case, ECU will ignore your O2 signal, and follow a predefined fuel mapping.

 

As you can see, in close loop situation, the ECU will adapt to achieve near-maximum fuel efficiency. There's actually no need to tune the car here. Unless you want more HP/Torque during close loop situation and sacrifice emission and fuel economy. Piggy back is not able to do that, because the ECU will quickly undo the changes.

 

The piggy back can effectively tune the open loop operation. The ECU stock predefined mapping might be overly rich (to be on the safe side). You can use piggy back to lean it out to get more HP/TOrque and fuel economy. Also, if you have aftermarket modifications, you should use piggy back to tune to maximize hp.

 

There are a whole lot of tuning techniques on ignition too.. Personally, I think ignition tuning should be done with standalone ECU with advance features that will react to different situations.. A simple ignition advance device is very dangerous.

 

Here's how your stock ECU will modify ignition.

1. higher rpm -> advance timing

2. higher air volume(MAF) -> retard timing

3. higher engine load -> retard timing

4. engine overheat + not idle -> retard timing

5. engine overheat + idle -> advance timing

6. Altitude correction

7. EGR correction

8. Knock detection

 

As u can see, some ignition timing adjustments are trying to protect the engine.. If you use piggy back to advance nonetheless, it might cause damage.

Edited August 24, 2004 by Zrun

[Normal_aspirated]

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From what I know, piggy back systems does not hijack airflow signals, it uses airflow signals, rpm, throttle position to come up with a value to add or subtract to ECU's signals.

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That's exactly what piggybags does, add or substract the A/F signal to the stock ECU, like you have just said it.

[Zrun]

I used to think that the piggyback hijack the signals. Example, alters the airflow signals to trick the ECU to inject more fuel.

 

However, it uses the same airflow signals to add to or subtract from the fuel injector duty cycle only.

[Modeldriver]

bro...me finally understand more liao....just wondering...how much roughly is the HKS and Buddy Club piggyback...am i rite to say tt the piggyback can be transferrable to other cars and reprogram to suit the other car or a certain piggyback is only suited to certain cars???....like suspension like tt??....most impt of all now...which is the beta deal????....cos me went to N2CS recently....they offer to upgrade my ECU ROM....but forgot to ask how much...does it mean tt a ROM upgrqade is not transferrable???....

 

Bit out of touch on pricing these days, but last time I recall both HKS and Buddy Club would be in the region of $1000 to $1200 w/tuning. They don't come cheap. So far because they are from Japan, I suppose quite safe to say most tuners would know how to fit to Jap cars - that's why so long as you stay with the popular Jap cars, should not have a problem. It's when you go for Continental cars it's a bit harder, but I suppose not impossible.

[Cyrix]

hiya bro..thks a lot for the price....guess would be ard there oso....

guess i have to postpone the upgrade liao.....no $$$$...to play wif...

[Cyrix]

thks bro...very educational....btw...if i were to do a ROM upgrade...will it be beta??

[Zrun]

Dunno what is beta.. I think only some of the factory ecu can be flashed, because their reprogramming interface is not released to the public.

[Normal_aspirated]

"Beta" means not released to the general public yet, juz like any softwares. Those who want to try it at your own risk and wanna be "guinea-piggy".

 

Agree with you, many Jap cars here don't have OBD2 interface, very sad for pple like us who want to access the interface & programming.

[Zoomer]

Bro..

So does that mean that installing a SAFC2 on my VTi-S will no doubt improve the performance, but the stock ECU will overide it in time to come?? Normal cars like mine should b a open loop or close loop?? Thanks

[Zrun]

As a summary, for all modern cars, SAFC/E-Manage etc will significantly improve performance when you hold down the accelerator all the way. (This is permanent)

 

When driving normally, you'll feel improved throttle response, but they will be corrected by the ECU after a while. If the ECU senses that the AF ratio is off 14.7:1, attempted to correct it, and failed, it will definitely throw check engine light error. Usually "too rich" or "too lean".

Edited August 26, 2004 by Zrun