lilvee said:
Bottom line : Piggy Back cannot INDEPENDENTLY adjust fuel and ignition, any changes to fueling will produce a change in ignition too, and often this is undesirable. And also, tuning only piggy back without parts upgrade.. not give impressive result.
my 2c....
Maybe Mr. Zaki got more to chime in... heh heh
You're right, lillvee.. but there are workarounds around that.
Edited for the 4th time!!! Bwahahaah!! ...
Your post has my mind in tangles.. How come leaning out = ignition advance? I got confused for a while.. and edited this post a couple of times before realising where I went wrong... haha.. no wonder my knowledge conflicted.
Like zaki said.. too much can become 'merapu'... ROFL!
Let's consider a column of the ignition and fuelling map... from the left to right, you see that as fuelling increase, ignition advance increases as well, the severity depending on RPM.
What VAFC does is cheats the ECU to think that it's getting more air(flow) than usual, hence the advanced timing AND fuel enrichment.
So adding fuel with VAFC will ADVANCE ignition.. due to the fact that it doesn't really control the injectors, but rather cheats the MAF into thinking that there is more air(flow) present..
So, since VAFC doesn't allow you to do A LOT of enrichment without SIMULTANEOUSLY increasing ignition advance.. we use the fuel pressure instead...
Then if we have too much fuel at the mid bottom end, we trim it using VAFC, and compensate by advancing the static ignition.
This feels kind of short.. but I think if you played around with VAFC long enough.. you'd understand how to beat 'some' of the limitations of VAFC. It's initially meant for mild modded engines.. but you can really 'stretch' it's use for quite a while before actually needing a standalone unit.
That's why I said got workarounds... :P
Thing is.. if you need so much fuel enrichment and total control of timing.. WHAT THE HECK ARE YOU SHOPPING AROUND FOR A PIGGYBACK?? :P
Oh.. Observing
unichip version Q being done... It's quite clever (the design.. not the ECU.. computers are stupid.. period.. :P ) in the fact that it intercepts the ignition timing as well.. so
it's an old-minded belief that piggybacks do not allow ignition control :P It's near standalone capability.. but one has got to wonder.. do we have to go so far adding an EXTRA BOX that does almost everything??
It's cheap.. so that's probably one I have to consider a plus for unichip...:P
Piggybacks are the simplest to play with, but they're limited if you're comparing to standalones.. So I hope nobody misunderstand this.
There was no argument about piggybacks being THE ONLY TOOL for tuning.. rather.. it's quite a good option for those with mild mods... A LOT of people are sticking with the B16A and SOHC VTEC.. having a cheap method to tweak the maps is a good choice for them. The thing is.. the cost of the unit and 'one off' tuning cost kills the interest of most regular, slow-build modders.
Or do you think these fellas are going to put in a 3K standalone setup in their 'relatively' stock engine?
It's also the means to tweak a chipped ECU.. where the percentage changes are small, thus doesn't affect ignition so much.. a lot of people simply plonk in mugen/spoon/etc ECU without realising that it's not that great of a performance increase since it was programmed on a engine with a specific setup... So unless if you mirror that setup.. sometimes you get less performance gain than claimed.
A little tweak here and there... and you'd see some gains on the dyno.. sometimes more than expected.
If fact.. I think it will grow for quite a while along with the owner that does upgrade in stages, without an extreme step up in any of the stages.