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Just dyno'd with the new intercooler :D

wilch

By wilch,
in Engines & Forced Induction

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Sydneykid Grand Master

Sydneykid

Posted
Posted
Hard to tell....... Do a dyno run where they chart your psi.

I know of another that runs a bleed valve, and the boost runs up smoothly, then falls off significantly higher in the rev range (ie. doesn't peak, and hold... the ebc's tend to peak and hold if set properly, or like mine, spike right at the start then hold. LOL).

Doesn't amtter what type of boost controller you run, if the turbo can't supply enough airflow to hold the boost level it will drop as rpm increases. Changing boost controllers won't fix this, only a higher flowing turbo will. Sometimes removing restrictions will help a lot eg; better flowing intercooler and/or exhaust.

Hope that helps :D

wilch Grand Master

wilch

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haha wilch looks like that encouragement award from the dyno day did the trick :D

hehehe, evil!!!! Yep, seems like it's encouraging me to spend money on my car instead of nonessential stuff like...food, etc LOL :P

wil..

Beer Baron Grand Master

Beer Baron

Posted
Posted
I had my car dyno at unigroup. I got pretty much the same results as yours but i got a bigger dip at top.

Had Hybrid front mount running 12psi with avcr, exhaust and pod filter

There is something seriously wrong with that graph. The power drops like 30kws near the end, then picks back up again. I don't even know what it causing that.

Richard

Sydneykid Grand Master

Sydneykid

Posted
Posted
the SAFC wont alter the ECU timing

You really need to read this post I prepared earlier....

SAFC only adjusts A/F ratios in pretty broard steps (8 in the current version) wiht extrapolation algorithms filling in between. It does NOTHING for igntion timing, in fact in many cases an SAFC makes the ignition timing problem worse. Firstly a quick, simplistic explanation of how an SAFC works might help...

As the airflow into the engine increase, the AFM records this as increased voltage that the ECU sees. What an SAFC does is sit in between the AFM and the ECU and take the voltages from the AFM and either increase or decrease them depending on what you have programmed the SAFC to do. By increasing the voltage, this tricks the ecu into pumping in more fuel, you do this when the engine is running lean. By decreasing the voltage, this tricks the ecu into pumping in less fuel, you do this when the engine is running rich.

The next bit is hard to understand unless you remember that the standard ecu does not supply fuel in direct proportion to the afm voltage ie; 4 volts is not twice as much fuel as 2 volts. Engine rpm, boost and throttle position also help the ecu determine how much fuel to add.

It has been my experience that RB25's run a little lean down low in the rpm range (Nissan do this for fuel economy and emissions) and a lot rich up high (Nissan do this to protect the engine). So I have to increase the voltage (using the SAFC) up to around 3,000 rpm (part throttle especially) and decrease the voltage over 5,000 rpm (full throttle).

The real problem is in the 3,000 to 5,000 rpm range as the engine comes on boost. They really need lots of fuel very quickly in this area. This can mean that you need to increase the voltage (that the ecu sees) over 5.1 volts to get the right A/F ratios. The ecu then goes into engine protection mode, rich and retarded (sounds like a girl I knew once) . Past that rpm you can start leaning it out as it runs too rich, so the voltage needs to be turned down under 5.1 volts. The ecu sees this as the engine not needing protection mode any more, no more rich and retarded.

It is not unusual to get good performance up to 3,000 rpm, then sluggish from 3,000 rpm to 5,000 rpm and then good performance from 5,000 rpm and over. The SAFC may not help this, in fact as explained above, it can in fact make it worse if the tuner is not switched on to this stuff.

With bent afm voltages, the ecu (tricked by the SAFC) also fires the ignition to suite the airflow it THINKS the engine is getting. This is not a good thing as you generally end up with ignition that is too far advanced in some rpm ranges.

The poor tuner has to juggle the SAFC settings, so that the A/F ratios are OK, the ecu doesn't get into rich and retard (engine protection) mode and the ignition timing is not too far advanced so as to cause detonation. My experience (I am not a good tuner) has been that this is full of compromises, sometimes you just can't win and have to reduce the boost level a bit to get even a reasonable compromise.

Keep in mind that this explanation is very simplified to make it fit in a reasonable space, the rpm's used are rough guides only and every car is different.

Hope it helps (and makes some sense).

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