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Discussion Starter #1
I've done a few searches and could'nt find anything on this so i'll just ask:D

Firstly can anyone recall or quickly get their hands on the equation for calculating oxygen mass from air density and temperature?

Also the voltage range at different pressures of a 3 bar MAP sensor?

T5 must use this calculation in it's fuel maps and as both IAT and MAP are essentially variable resistors i was wondering, if using this equation you could use a 3 bar map sensor and then some how alter the resistance of the IAT linearly with boost.

So although the ECU may see 3.3 volts at 1 bar rather than 0.75 from the MAP, it at the same time reads a lower temp from the IAT, somehow you would have to create a linear voltage rise with boost.

It would be a bit easier if the IAT decreased in resistance as temperature rises as you could just run a second MAP/resistor combo in parallel to it, i'll have to get my head back into my electronics books to come up with some way of decreasing the resistance across the IAT linearly with boost.

If possible i can test it with a wide band O2 to make sure the a/f ratio's are OK, i'd probably have to fine tune it to a certain extent from the WB02 as i guess a basic maths calculation will only give a rough area to start tuning from.
 

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Si said:
Firstly can anyone recall or quickly get their hands on the equation for calculating oxygen mass from air density and temperature?
Not possible without knowing Volumetric Efficiency. Since you cannot measure that without a MAF sensor, there's no way to do this ... though you could show proportional changes. If you assume that there are no mechanical changes to the engine, the VE will not change, so any change in air density, will be an equally proportional change in airflow.

The way the car is programmed from the factory, since even they don't know the VE until they program it, they just estimate it, and then monitor O2 readings (assuming they didn't use a MAF sensor to program it, which is possible) ... and once they get the O2 sensor readings where they want them, they leave the program alone. Only long term additive (near idle) and multiplicative (in adaption window) changes in the MAP are possible through O2 feedback, which is basically the ECU re-programming itself to adapt to mechanical changes in the engine, or fuel system.

There's no reason you couldn't run a higher BAR MAP sensor with proportionally sized injectors, but the ECU would think it was in the wrong load sites, and the ignition timing would be way off. It would run ignition timing for 8 psi when it's now running 15 ... though properly sized injectors WOULD solve the fuelling disparity.

A better solution is really just a custom tune with the 3 bar MAP sensor.
 

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Discussion Starter #3 (Edited)
Thanks Adrian, i shall endevour to keep looking for alternatives to spending between £4-600 ($800-1200) for a custom ECU for the mean time:D , expect more random questions until i bite the bullet!

I should have completed some more HW changes by the first track day of next year in April, so will consider an off the shelf ECU or custom tune in a few months, I will have to look into what Abbott racing and Nottingham Saab offer.

edit!
After thinking about what you said in regard to the disparity caused in the ignition timing, i wonder if this then could be used in conjunction with a water/methanol injector, as that may allow the engine to run more advance at higher boost levels?:confused:
 

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Why not order one from the US - Nordic T5 ECU's are $550 from GS which is around £225 plus shipping. That's where mine came from.
 

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Discussion Starter #5
Given the exchange rate, that's probably the best option availiable.

Are you aware of any differences in the ECU's for UK and US market?
 

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Only rumour that I heard is that euro cars are optimised from the factory for 95Ron but that US cars may be different. This would make sense as fuels do vary between countries. The rest of the components that feed into the ECU and that are effected by the ECU are identical - MAP, O2, IAT, CAT, Injectors etc so I can't see an obvious problem. Both Nick at GS and the head of Nordic respond well to emails so maybe worth dropping them a line.
 

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si said:
So although the ECU may see 3.3 volts at 1 bar rather than 0.75 from the MAP,
that is essentially the easy part, the hard part is getting the ecu to deliver enough fuel for 1.1 bar when it thinks its only seeing .75 bar


fooling the ecu is dangerous and could end up with this happening


 

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Discussion Starter #8
touche:cheesy:


You'd have to do it in conjunction with the IAT so the correct amount of fuel was being added, but as Adrian said, you could'nt compensate for the timing at different boosts.
 

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Shirozina said:
Only rumour that I heard is that euro cars are optimised from the factory for 95Ron but that US cars may be different. This would make sense as fuels do vary between countries. The rest of the components that feed into the ECU and that are effected by the ECU are identical - MAP, O2, IAT, CAT, Injectors etc so I can't see an obvious problem. Both Nick at GS and the head of Nordic respond well to emails so maybe worth dropping them a line.
Well, 95 RON is like 90 AON octane, and even the worst states, like here in California, have gas that has 96 RON (91 AON) for "premium"), and many states have as high as ~98-99RON (93-94AON).

So, if anything, the US version are just calibrated for 96-98RON, which means you'll hafta run the expensive stuff if you do buy it. :confused:
 

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Shirozina said:
I think most tuners of these ECU's in Europe recommend that you run premium or high RON fuel with them anyway. Take a look at the Dyno graph from Nordic Europe for the T5 http://www.nordictuning.com/data/tuning/files/SAAB_9-3_185HK_T5ST3.jpg
Holy ... look at the change in oil temp! It's almost like they did it on an engine that was still warming up. Either that, or the oil gets awful cold normally, untill you hit the "go pedal", and then it needs a better oil cooler ASAP. :eek:

edit: unless that was the temperature BEFORE the cooler, in which case, the cold readings either mean it was, indeed, warming up still, or are just scary low. If it's after the cooler ... it definitely needs a better one.
 

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This is on a dyno with poor airflow over the stock oil cooler though - may not be the same on the road. At least the sump is exposed to the airflow on a NG/9-3 unlike the old c900 where it was buried in the grearbox. If oil was overheating or overcooled on these cars we would be seeing a lot of bottom end problems? - as these are virtualy unheard of I wouldn't be too worried. There was a thread about this earlier.
 

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Adrian W said:
Holy ... look at the change in oil temp! It's almost like they did it on an engine that was still warming up. Either that, or the oil gets awful cold normally, untill you hit the "go pedal", and then it needs a better oil cooler ASAP. :eek:

edit: unless that was the temperature BEFORE the cooler, in which case, the cold readings either mean it was, indeed, warming up still, or are just scary low. If it's after the cooler ... it definitely needs a better one.
The temp is taken via a "dip-stick" sensor, so not after cooler.
Also the measurement is statistic, points measured individually not through a dynamic sweep. The cool time between the poins is up the user and therefore a conclusion cannot be made how the oil temp behaves under a rpm sweep.
Being this the case the measurement of the points have began far before the engine is up to operation temp.
 
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