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Apexi PFC Question

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I have a PFC Pro on my R33 GTS-T,

My problem is that it only allows factory boost (5 PSI). I have a bleed set to 13psi but the computer does ignition cut if I boost over 5 PSI. I am getting a tune in 2 weeks and I would like to know how to turn this of just incase the turner does'nt know.

Can it be done with the hand controller?

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Hi GunMetalR33, I am sure I have posted this before...but just in case.

I have never seen a boost limit on any PFC. I have used both Commanders (GTST's and GTR's) and Datalogit (on GTR's) and nowhere have I seen even the slightest mention of a boost limit. Now I haven't used a Pro Version, but I have never heard of any differences in the area of boost limit.

So I reckon it must be something else. Have you tried driving around with someone watching the Commander readout? Or videoing it and playing it back in slow motion? There must be a sensor that is telling the ECU something that makes it cut the ignition.

You can do this 2 ways, the most common is by viewing the sensor input screen, this shows the raw data, like voltages in real time from the sensors. Watch them and see if anything strange happens (ie ; voltage drop, spike etc).

The second is with the MAP tracer, watch the tracer on the map layout and note where the problem happens. Then go to that sector on the map and see what numbers are input. You can do this for both ignition and fuel.

If you don't see anything from this (most unlikely) then it must be something else like fuel pressure, spark plug problem, ignitor failure etc. You just have to work your way though each one, one at a time.

Hope that helps

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G'day guys,

GunmetalR33 was over my place today and we tried a few things with no luck :D

Tried a few things like plugging the stock solinoid in and told the PFC that it had a boost controller - we knew that the PFC/stock solenoid wouldn't let us adjust boost, or even control boost in anyway, but it was worth a try to get rid of the (feels like) boost cut. I think we tried almost ever combination of things with the stock solenoid.

Fiddled with a few settings with regard to the 4 options on the boost - no luck.

I thought there may be a boost/ignition cut table that may be set to stock boost levels on the base (untuned) map, but I couldn't find a thing (I've seen such tables in the E6K etc).

Also tried changing the options in the AFM menu to 'Super Airflow' and the others with no luck.

SydneyKid - I did a few trace map runs and the injector side of things looks fine with no major change when the stutter starts, although watching the ignition trace there is a definite reduction in timing advance when the stuttering starts. It sharply moves from around ~28 degrees advance to ~15 degrees advance.

Also did a trace map run against the AFM voltage and things didn't get over 4.8 volts, although saying that, the stuttering is prelevant at even 4 volts !

We found that the stuttering started consistantly at ~3000rpm regardless of what changes we did via the handcontroller.

I do recall that GunMetalR33 had some ignition problems a long time before the PFC was installed, although the problems were fixed and he was running 13psi with no problems on the stock ECU before the PFC went in. It was just a matter of reducing the plug gap from 0.8mm to 0.74mm.

As he is still running the base map, maybe one of the last things we can try is putting his PFC into my car (I'm running 12psi) and see if the boost cut is still there. If it is, then it's in the tuning of the PFC, if not, well it must be something in GunMetalR33's car ;)

One question, if say the coil packs are delivering a weak spark, or if the plug gap is wrong, how would the timing be affected, or would it be affected at all?

Do you think it's possible that even though he is still using the base PFC map, that it's timing is a little more aggressive than the stock ECU and this is bringing back the weakish spark problem that he encounted before? (I'm stabbing in the dark here !!)

Is there anything else you think we could try?

This is frustrating me as much as it is GunMetalR33 !!


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Green line contacted apexi for me and apexi informed them that the PFC is designed to limit to stock boost when running the base map. (not sure if this is just a Pro thing or not). I think it must be something to do with boost as this problem only happens when I turn my bleed on and boost over 5 psi.

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If you are still running the initail map, have you tried a reset? Might fix the problems, quick and easy with out any downsides. Might need to make sure the boost control is switched off after the reset, not sure whether default is on or off.

I had no boost cut with base map on my power fc. The ignition retard at 3000rpm seems a bit strange. With base map my car went alot harder than stock ecu (series 1 gtst).

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Hi Guys, this smells like a unique PFC Pro feature. Logically it sounds like Apexi believe that when you buy a Pro you must have a highly modified engine. Therefore their base maps are goingto be a long way out. This is not the case with a normal PFC, where they must figure that you only have a mildly modified engine. Thus their base maps are going to be pretty close.

So for the Pro they protect the engine by limiting the boost to a low number whenever the standard maps are used ie; until it is tuned properly to suite the large number of modifications.

To fix this, I would modify the base fuel and ignition maps a tiny amount (maybe a few cells here or there) and the boost correction table and then save them. Since you will then not be running on the standard maps my theory is that the Pro software will then think that you have done a full tune and unlock the boost.

I'd give it a go, it should only take a few minutes.

Hope that helps

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and the boost correction table and then save them

SydneyKid - Is the boost correction table the table with four options on it with (for example) boost pressure in kg, a value that can be varied between 20 and 90, and a value at the far right of the screen that is set to 255 ?

There's four lines of this info if that makes sence?

I was trying to figure out what the variable value (20-90) represented. Our guess was RPM. eg. 20 stood for 2000rpm...

We put all these four lines upto the maximum boost value of 2.0kg (about 2 bar), but had the same effect (nil) ;)


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the variable figure is solenoid duty cycle. The higher the boost the higher the duty cycle needs to be.

If after adjusting boost and duty cycle the boost spikes, adjust the duty cycle down until it brings the boost up to the correct pressure.

If the boost is slow to come up, adjust the duty cycle up until it starts to spike, then knock it back a bit.

It is supposed to automatically learn the correct setting once you are close to the correct duty cycle - but if you are way out, I have found that the boost will be a fair bit off.

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Ahh cool, thanks for that Steve.

Now, SydneyKid was talking of a 'boost correction table'. Where is that in the menu as I couldn't find it. I've got a funny feeling that this is the cause of the problem, eg boost correction table set to retard/cut ingintion timing at anything over stock.

Anybody know where the boost correction table is in the menu, and also what it's called??

Thanks heaps


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