R34 Gtt Boost Sensor, Does It Affect Af/r?

[msports180]

Does anyone know of the R34 Gtt boost sensor (the one on the firewall) affects AF/R's? and secondly the rev limmiter?

Had my Skyline tuned last year and had some problems, ended up having to unplug (the hose not the wiring) the boost sensor as i had plumbed it up after the throttle body, this was causing issues, I didnt know at the time, It resolved most of the problems and off we went.

I have now hooked it up before the throttle body, will this affect my AF/R's at all? From having it tuned without it? to now the same tune and it hooked up?

And secondly when my car hits the rev limiter it dies, for approx 5 seconds, no power at all. Im hoping this is associated with the boost sensor as in the workshop manual i have it says this controls the fuel cut?

Im in now way complaining about the tune, its awesome, we simply ran out of time on the day as i went in with a car not running, and due to where he is located externally gated car's are not allowed on the the dyno till late afternoon, coupled to my 3 hr drive home we couldnt finish all the fault fixing. I'd rather not tow the car all the way up there to find out its fine.

Thanks!

[Ben C34]

in the stagea section there is a tutorial on how to bypass the boost cut, the Guy just disconnects the hose going to the sensor. I am reasonably sore it has no effect on afr.

[Simon-S14]

its not a fuel cut.. its boost cut. the sensor tells the ecu when its going over 12 psi and then the ecu protects the engine by cutting it to prevent over boost. so with it connected you pretty much cant run over 12 psi.

[Hanaldo]

its not a fuel cut.. its boost cut. the sensor tells the ecu when its going over 12 psi and then the ecu protects the engine by cutting it to prevent over boost. so with it connected you pretty much cant run over 12 psi.

Pretty sure the standard ECU doesn't have a boost cut. It's a TP cut. So yes, the sensor reads over 12psi and tells the ECU, but the ECU doesn't cut boost, it cuts the injectors to prevent overboosting. Could also be an ignition cut, but my understanding is the standard ECU uses TP cut to prevent overboosting.

But to answer the OP's question, while the cut is a boost cut, it doesn't affect your AFR's in a harmful way. It cuts fuel altogether so your engine doesn't fire, it doesn't lean things out and cause damage. That said, it's still not a good idea to hit it. You should try to bypass the sensor so that the ECU thinks it is still working, but it doesn't actually do anything. Can wire in a resistor to do this so that the sensor always reads a certain voltage.

Edited April 13, 2013 by Hanaldo

[GTSBoy]

The Neo has teh same TP limit cut that the earlier RBs have, but adds the boost sensor as an extra layer of protection.

So it has both.

[Hanaldo]

The Neo has teh same TP limit cut that the earlier RBs have, but adds the boost sensor as an extra layer of protection.

So it has both.

But how does it actually perform the cut? I'm quite sure the stock ECU doesn't shut the throttle, so it's either fuel or ignition. Fairly sure it uses the same TP cut method as it does for AFM voltage, it's just triggered by the boost sensor in addition to the AFM.

[GTSBoy]

Yeah yeah. Details. Doesn't matter what it does, just why and when it does it.

[msports180]

Possibly left out some important info, sorry posted this at the end of a night shift! Its running a Stagea image in the R34 ECU with a Nistune board and Z32 AFM, not sure if this changes anything?

Its not connected now, so how could it be instigating a cut when hitting 12psi if its only see's atmosphere? If it was connected i could see it happening as im running 17psi.

[Hanaldo]

You said you had hooked it up? If it's not connected then it's not the problem, it won't be doing anything .

[msports180]

Sorry the OP is not very clear! I was way rooted this morning.

It was not hooked up, and when it was not i was having the limiter issue with the engine dying.

I have now hooked it up, but have not driven it yet as i was just wanting to check to make sure it was not going to affect the AF/R and kill the motor. I am hoping hooking it up was going to fix the limiter issue as i was thinking the ECU is getting all confused. If it does not fix it then its another trip to Perth

[GTSBoy]

How much power are you making? Matt from Nistune has told me that there is a problem with Neo ECUs chucking a spaz and doing some wierdo fuel/ign cut when the power level climbs up fairly high (like in the 300 rwkW region). This is separate to and over and above the known about and expected cuts discussed above. Seemed to be associated with the traction control and ABS stuff. I don't know if this has been resolved yet, because it was a year ago since we were talking about it, but at the time it was known exactly why and how it was happening.

[Hanaldo]

Definitely happens before 300rwkw. Those are the issues that forced me to be switch to the Link. But they aren't really noticeable like how Neil has described his issues. The only thing I noticed was an intermittent misfire in high revs when the ecu pulled timing. There was no cut or massive loss of power.

[Simon-S14]

i was making 360 rwkw with nistuned r34 ecu, no boost sensor plugged in and zero issues (threw up plenty fault codes when laptop connected tho)

[msports180]

So not what i wanted to hear

Mine has no traction control as its using the stagea image to remove it so i can run a R33 TB.

Might just drop the boost a bit and hope it goes away just so i can do a track day on the 27th!

[Hanaldo]

i was making 360 rwkw with nistuned r34 ecu, no boost sensor plugged in and zero issues (threw up plenty fault codes when laptop connected tho)

Yeh it's an odd one. Mine was intermittent, sometimes it was perfect, other times the ECU pulled fuel/timing randomly. Made it a real pig to tune apparently.

So not what i wanted to hear

Mine has no traction control as its using the stagea image to remove it so i can run a R33 TB.

Might just drop the boost a bit and hope it goes away just so i can do a track day on the 27th!

I doubt it will be an issue with too much boost. If Sean has tuned your car like he tuned mine, then he will have moved the TP cut to the uppermost limit of the map, so you will never hit it. Are you 100% sure it's not a vacuum leak or something similar? Doesn't really sound like it, but have you checked?

[msports180]

Yeh it's an odd one. Mine was intermittent, sometimes it was perfect, other times the ECU pulled fuel/timing randomly. Made it a real pig to tune apparently.

I doubt it will be an issue with too much boost. If Sean has tuned your car like he tuned mine, then he will have moved the TP cut to the uppermost limit of the map, so you will never hit it. Are you 100% sure it's not a vacuum leak or something similar? Doesn't really sound like it, but have you checked?

It was tuned at Hyperdrive, i have no idea what he did with the cuts, we really ran outta time.

How would a vac leak affect this? It does have a tiny one through the throttle shaft, the bush is stuffed, have spare one, just havnt changed it yet.

[Hanaldo]

Ah sorry, thought you had it tuned at ASG.

To be honest I'm not sure if a vacuum leak would cause your issues, but if you know it has one then I would get that sorted, otherwise it will always be a question mark.

Edited April 14, 2013 by Hanaldo

[msports180]

Yeah i'll chuck the other TB i have on, will get it running again this week and see how it goes.

[msports180]

All running again with the boost sensor hooked up. It certainly runs better at idle and cold start, no more black soot pouring out the exhaust. I haven't driven it yet, but even free revving to the limiter it dies so im thinking its not associated with any boost cuts etc?

May be an actual issue with the limiter setting in the ECU? Maybe the hard limiter is set before the soft for some strange reason?

[Hanaldo]

Have you spoken to Andy about it?