Power Loss On Downshifts, Bouncing Idle And Slight Hesitation At Specific Rev Point -R34Gtt

[rondofj]

Lookin back at the original thread, some issues on the car HAVE been fixed:

Bouncing/rough idle- new O2 sensor

Stickiness/hesitating @1500-2000rpms- as above

Headlights increasing idle - tighten alternator belt, sand and clean main earth

Dramatic power loss after swapping cas (current problem) - timing, not fully sorted but thats what it is.

DIY Boost leak tester- found/fixed 4 leaks @18-20psi pumped air, minor ones.

Huge power loss during shifts- possible reversion/bov entry not ideal- not worried/last thing on list to fix

Rubbish fuel economy- first fill with new O2 sensor, lets see- also afm is untested- may/may not be f£#ked.

And thats it really

[rondofj]

Next move- log afrs, get wideband or just go to tuner.

[XGTRX]

Im glad I do have the controller- learnt a lot of stuff- if it blows then it blows, its not a Porsche, another 3-5k will have an RB25/30 sitting under the hood with a whole lot of lifetime knowledge n experience : win

Something basic for you to read because if you blow something you really wont learn anything.

This is from garrett.

When discussing engine tuning the 'Air/Fuel Ratio' (AFR) is one of the main topics. Proper AFR calibration is critical to performance and durability of the engine and it's components. The AFR defines the ratio of the amount of air consumed by the engine compared to the amount of fuel.

A 'Stoichiometric' AFR has the correct amount of air and fuel to produce a chemically complete combustion event. For gasoline engines, the stoichiometric, A/F ratio is 14.7:1, which means 14.7 parts of air to one part of fuel. The stoichiometric AFR depends on fuel type-- for alcohol it is 6.4:1 and 14.5:1 for diesel.

So what is meant by a rich or lean AFR? A lower AFR number contains less air than the 14.7:1 stoichiometric AFR, therefore it is a richer mixture.

Conversely, a higher AFR number contains more air and therefore it is a leaner mixture.

For Example:

15.0:1 = Lean

14.7:1 = Stoichiometric

13.0:1 = Rich

Leaner AFR results in higher temperatures as the mixture is combusted. Generally, normally-aspirated spark-ignition (SI) gasoline engines produce maximum power just slightly rich of stoichiometric. However, in practice it is kept between 12:1 and 13:1 in order to keep exhaust gas temperatures in check and to account for variances in fuel quality. This is a realistic full-load AFR on a normally-aspirated engine but can be dangerously lean with a highly-boosted engine.

Let's take a closer look. As the air-fuel mixture is ignited by the spark plug, a flame front propagates from the spark plug. The now-burning mixture raises the cylinder pressure and temperature, peaking at some point in the combustion process.

The turbocharger increases the density of the air resulting in a denser mixture. The denser mixture raises the peak cylinder pressure, therefore increasing the probability of knock. As the AFR is leaned out, the temperature of the burning gases increases, which also increases the probability of knock. This is why it is imperative to run richer AFR on a boosted engine at full load. Doing so will reduce the likelihood of knock, and will also keep temperatures under control.

There are actually three ways to reduce the probability of knock at full load on a turbocharged engine: reduce boost, adjust the AFR to richer mixture, and retard ignition timing.

These three parameters need to be optimized together to yield the highest reliable power.

Lookin back at the original thread, some issues on the car HAVE been fixed:

Bouncing/rough idle- new O2 sensor

Stickiness/hesitating @1500-2000rpms- as above

Headlights increasing idle - tighten alternator belt, sand and clean main earth

Dramatic power loss after swapping cas (current problem) - timing, not fully sorted but thats what it is.

DIY Boost leak tester- found/fixed 4 leaks @18-20psi pumped air, minor ones.

Huge power loss during shifts- possible reversion/bov entry not ideal- not worried/last thing on list to fix

Rubbish fuel economy- first fill with new O2 sensor, lets see- also afm is untested- may/may not be f£#ked.

Can be all due to retarded timing

possible reversion/bov entry not ideal- not worried/last thing on list to fix

No, Fix this first before this

Next move- log afrs, get wideband or just go to tuner.

[XGTRX]

another 3-5k will have an RB25/30 sitting under the hood : win

dreaming

[Badgaz]

Better still, go and do some of the high performance academy training courses at www.Learntotune.com

[AngryRB]

my money is on cyl 5 or seeing you on an episode of hwy patrol, lol

[rondofj]

haha. So where on pfc do you need to check to match the base timing - the 2,4,8 channel monitor where the idle always shows as 15 degrees? It also shows as 15 degrees in the settings> ign/inj > ign cor > fin 15 degrees.

[Ben C34]

http://paulr33.com/powerfc-faq/powerfc-faq.htm#40a

Sounds like you have it sussed , except that you have your cas set to 20 when the power fc thinks it's at 15. Which is a critical problem.

Edited August 26, 2014 by Ben C34

[rondofj]

Yes I will be taking it down to 15 (with TPS connected as others have said), with 20 it 'looks like' where it was before I took it off.

[rondofj]

Yavuz said to set timing as shown on pfc with TPS connected or disconnected doesn't matter - well in my case it does matter by 5 degrees extra with TPS off.

And yeserday the engine dwindled down to a weak cough/ low idle and died after 5 secs of disconnecting the IACV plug haha

[rondofj]

The idle cell N02, L02 on my timing map is 19 not 15, is this correct? I know you set base timing from power fc settings but no one has said where exactly - I just set it from the settings>ign/inj>ign map> and the map/fin is usually 15 degrees when warm enough. Assume this is correct.. :S

[Badgaz]

i'm still convinced the powerfc changes ign timing in idle control circuit.

[rondofj]

Does that mean the cas needs to be set to 19 degrees as thats the idle cell on my timing map?

[GTSBoy]

Does that mean the cas needs to be set to 19 degrees as thats the idle cell on my timing map?

No. It does not. That picture is just the normal timing map yes? And you say that when it is idling you see the PowerFC accessing the N02, L02 cell, yes? Well, what if we told you that even though that cell is highlighted, because the TPS idle is detected, the ECU is NOT making its decisions about fueling and timing from the main maps, but instead is making them from the idle maps?

Now, I must point out that I don't KNOW that PFCs do that. But every other bloody ECU in the world does. The Nissan ECU certainly looks up a separate idle timing map, not the main map.

What the CAS must be set to is what the PFC has been told the CAS is set to, which will be in some other location in the ECU althogether, not on the main timing map. Some basic setup screen.

[Ben C34]

I'm sure I've already mentioned it you have to set it to what the timing the power fc is putting out.

It's in the monitor settings somewhere. As written in the link I gave you..

[rondofj]

No. It does not. That picture is just the normal timing map yes? And you say that when it is idling you see the PowerFC accessing the N02, L02 cell, yes? Well, what if we told you that even though that cell is highlighted, because the TPS idle is detected, the ECU is NOT making its decisions about fueling and timing from the main maps, but instead is making them from the idle maps?

Now, I must point out that I don't KNOW that PFCs do that. But every other bloody ECU in the world does. The Nissan ECU certainly looks up a separate idle timing map, not the main map.

What the CAS must be set to is what the PFC has been told the CAS is set to, which will be in some other location in the ECU althogether, not on the main timing map. Some basic setup screen.

Oh ok thanks Brad - I think it would be in the monitor>channel>idle as Ben said, the reason I asked is because the monitor is exactly that - a 'monitor', not a setting. The idle once warm always shows 15 degrees here.

In the setting menu theres a Ign/Inj (temporary correction) - under this menu > Ignition > Map shows 15 degrees. Under Ign is also a Fin which shows 15 degrees. When u apply the correction the Map shows that correction eg 20 or 10 degrees but the 'Fin' remains at 15. And I assume but dont KNOW this 'Map / Fin' is what the powerfc has been told the cas is set to. Without correction, the map shows 15 degrees AFTER its warmed up.

Edited August 28, 2014 by rondofj

[hy_rpm]

That's when you have to set the base timing

Once warm and what ever the power fc is showing the timing should be the same at the crank as the tuner told you so it synchronized With the ecu

Otherwise the tuner will be inputting 15degrees or whatever in the ecu to tell it spark then but Infact the spark will be firing at 20degrees or whatever the base timing is set off

[Badgaz]

I have the power excel software and ill see if i can find an idle map or system.. I know the datalogit can only change the settings that are in the hand controller plus a couple extras.....

[rondofj]

hand controller has no access to idle maps that I know of :S

[Ben C34]

Have you tried looking at the monitor function. I'm sure it monitors timing.