- Apr 18, 2006
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Piggyback applies what we call a lambda on the original fuel mapping.thanx 4 the info..
blown my engine last month..
now left at danau kota woksop...
but, why can't use the piggyback??
remember the tables your tuner looks at?
as an example,XXXX| 1 | 2 | 3 | 4 | (more, but omitted)
1000 | 2.00 | 2.10 |2.50 | 3.00 |
2000 | 3.00 | 3.20 | 3.6 | 4.00
(more, but omitted)
The RPM is the 1000,2000 value, called the RPM index,
The 1, 2, 3, 4, is the load zones (or load index), some, like the PowerFC, uses numbers, while hondata, uses actual units (it doesn't matter really) Most piggybacks just use TPS to simulate the load index, like VAFC, Neo, etc. which means a little like guessing where the computer is ACTUALLY reading the map from.
You can also replace the load zones with TPS indexing on standalones, but usually that's done for running quads, because they can't have good part throttle (on/off driving) at low rpms due to lack of good MAP signal (it's doable, but well, what's the benefit of running quads with a tuning method designed for manifolds?)Yes, unlike what most people think, tuning is not really 100% exact science. Remember vacuum advance? Lol, that's not controllable at all, but the old fellas did it by use of springs and such, heck, they don't even care what kind of ignition it's running, as long as it made power.
That's why that's there manifold versus ITB, which is better? debate down in honda-tech, I think.
Back to topic. Well, what the piggyback does is apply 'adjustments to the map'
Like emanage, and unichip, they work in this method. They add adjustments to the original mapping, which is all good and fine, if the original mapping is static.xxxxx| 1 | 2 | 3 | 4 | (more, but omitted)
1000 | 1% | 1% | 1.5% | 3% |
2000 | 1% | 1% | 1.5% | 3% |
(more, but omitted)
The thing is, the mapping of honda ecu's in open loop mode is not static, (for the most part, at near to full throttle it's static) it changes from time to time, courtesy of it's long term and short term fuel trim. I think powerFC does this feature the best as an example, just start and wait for it to find it's own idle during intial setup. That is a more extreme example of how it works, but even the stock honda ecu's have that feature, although not at such a high correction rate.
But it's not like piggybacks are bad, they are good for minor adjustments, esp when the original ecu mapping is suited to the engine, but just need a little tweaking.
In the B20B case, most of the ECU's used, the original mapping is for the B16A, imagine what kind of adjustments are needed for that, and what kind of fuelling changes the original honda ecu will do as time goes by.
having a static lambda (fuelling adjustment) while the stock keeps adjusting itself, it's like trying to swat a moving fly while driving a car in the rain. lol. those raindrops and the fly start to blend in.. and both are moving, so you can't really see where the actual fly is.
I'm not sure if the newer gen piggybacks start tricking the 02 into a closed loop mode yet, but if you're the curious type, if D14 on the P30/P08 ecu is connected to the piggyback, then it probably is. I think that's probably one way to get around it, but well, originally piggybacks were made to map more accurately the original mapping (cleaning up the mapping due to added mods that changed the flow of the engine, when the original cannot cope anymore)
I don't think it'll ever come to that since it's like the piggyback trying to become what it's not, but well, just thinking out loud.
Well, that's just a small aspect of tuning. Now I know why mat salleh find it so fun. :P
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