Any increase in FC after OBIT

[Shaun]

look for the step from around stoich to noticably sub-stoich eh? logical and simple

yah sleepy but then I realized that if I sleep now then I can't wake up for school.. so tahaning till the morning hehaha. thus the low quality thought process

 

[Crufty Dusty]

does anyone know if there was a time when manufacturers made the switch over to more closed loop situations? was it a time when a new emissions standard was enforced? was there a specific year?

If I'm not wrong EuroIV will come into effect next year and manufacturers get a tax break if they roll out vehicles which are EuroIV compliant ahead of schedule.

Also, what is a good way to identify whether or not a stock ECU is operating in closed or open loop when not relying on an OBD scanner? Like what basic instruments would you use and what would you look for on what wire?

Now why would you want to do that? Heh...

I suppose you could influence the control variable by introducing errors before the feedback signal. e.g. keep the engine at a stable load/RPM site, monitor the AFR, then introduce CO or some other gas into the exhaust manifold. Definitely easier with a scan tool.

 

[otto]

In general FC goes up with power, but when looking at a gain in power, always look at whether it came from increased efficiency (friction reduction, combustion chamber and port optimization, accuracy and closeness to the limit of AFR and ignition timing, cam timing optimization, intake/exh. tract optimization etc. - basically anything that does not change, but makes better use of inducted air and fuel masses). The rise in FC accompanies rise in power only when that power has come about by increasing inducted air mass and burning the required fuel.

There is no real limit to increasing power through efficiency. But there are limits to increasing power by burning more mass... detonation, component strength/thermal resistance/capacity.
Gains from piggybacks can be made from increasing efficiency.. so the associated FC gains do not necessarily exist. It has been done many times before.

Hi dude,

how is obit compaired to hihop programmes?

I heard hihpo can be loaded directly to the stock ECU. and it's much cheaper that piggy backs.

any advice?

OttO

 

[Shaun]

If I was a busy man with a street driven car, I would go for hiop. If I had a little more free time or into a lot of track driving or automotive performance was a large interest of mine, I'd go with the piggyback and look for as good a tuner as possible, learn as much about piggyback tuning before going to the tuner.

 

[Shaun]

If I'm not wrong EuroIV will come into effect next year and manufacturers get a tax break if they roll out vehicles which are EuroIV compliant ahead of schedule.

oh I meant in the past.. like if it was when the switch from Euro 2 to 3 occured.. was that when they started holding on to closed loop till higher RPMs? As in... what years roughly had WOT straight switch to open loop.. and what years were manufacturers forced to have closed loop held till later RPM even at WOT.

 

[yendor]

IMO, the switch to Open loop at WOT is not a consideration. The main thing is the speed at which the Lambda sensor can read the fuel mixtures and modify the mixtures as necessary. Thus RPM becomes the deciding factor. the faster the engine turns over the greater the latency between whole cycles of pistons running as sub-optimal mixtures. Thus manufacturers use RPM as a guage for the switch over point. In the cse of WOT, it is left to the perogative of the manufacturer to design the ECU. Should he use 14+:1 mixtures or what?

Cheers

 

[Shaun]

hmm interesting cos I've talked to some people and they say that the sensors and ECUs are fast enough to handle anything within the 13,000 RPM range. Others have said that switchover is based on both load ans RPM. Also, in offshore powerboats where fuel consumption is a major concern and where RPMs are always high and loads are floating around 100% for hours on end, they run full closed loop.

I've talked to crufty (erik) before about this too and we kind of think the same thing in that going open loop saves effort in mapping as well as over reliance on sensors.

I dunno man.. all this is really interesting. Quite undecided on what is concrete cos getting into that level of detail takes a lot more time. Really appreciate your input though

cheers!

 

[yendor]

Ah you have struck the nail on the head. The RPM speeds in boats do not vary as much as cars. Henc the lambda sensors have time to fully reflect the burning mixtures. Closed loops are always more stable as they self correct.

IMO i think that open loops are actually harder to tune to get the maps right cos they have to take into consideration all the various what if's.... The second reason sounds more right as an over reliance on sensors may yield $$$ repair bills.

I think to answer the question, we will need to delve into the principles of control. There are basically 3 responses to a vertical step function.
1st, Underdamped, fast response to the change but oscilates about the steady state value until it comes to a rest.
2nd, Over damped, slow response but changes never overshoot the desired value.
3rd, Optimum response, follows the input changes closely and achieves zero error. (not fully achievable in real life totally)

If you think about it step by step, the lambda sensor is always taking the AFR 1/2 a stroke behind the conbustion process and assuming that the changes effected will result in extra fuel being squirted in another half a cycle later. Thus during thta time, 2 other pistons would have gone through the 4 cycle process by virtue of their intakes. All this is assuming that the sensor and ECU combo is able to follow the 3rd response of optimum control.

Now when we bring in the reving engine as experienced by cars, the over damped situation makes more sense that the ECU does not try to be perfect rather it just minimises the errors all the time to achieve the perfect desired outcome. Once past a certain rev range, especially for multi-cylinder cars, the underdamed response cannot catch up with the combustion process and they revert to open loop to base fuel calculations on. To get top grade processors and sensors is simply not worth for a car that cost so little to build...

 

[Shaun]

yeah erik was showing me a control system tech page previously that showed graphical representations of those types of responses you mention. was discussing using such quantitative methods and applying it to boost control since it is somewhat similar. This over the current testing that wastes more time than necessary.

good point in the 4th para! 4 stroke you mean. 4 cycles would be 16 strokes. 1 cycle, 4 strokes.

very interesting. MUCH appreciated man!

 

[yendor]

Yep, 4 strokes.... me blur... neber eat lunch....yet......

Interesting to see if the the under damped system works for boost control... those negative ringing areas are sure not good for power. But to bring up the boost higher and earlier is something worth considering.

To everybody else, sorry if the 2 young farts have dominated this thread......

Cheers

 

[Crufty Dusty]

Yep, 4 strokes.... me blur... neber eat lunch....yet......

Interesting to see if the the under damped system works for boost control... those negative ringing areas are sure not good for power. But to bring up the boost higher and earlier is something worth considering.

To everybody else, sorry if the 2 young farts have dominated this thread......

Cheers

Actually most of the boost controllers in the market are already using PD.

 

[yendor]

aaahh... the joys of forced induction......

Crufty, thanks.... now i must be good boy to resist temptation...

 

[Nuke]

:shock: :angry: :thinking:

cheemz ballz.. :furious: