What make the ECU go into LIMP mode?

Vortech 350z

 

A bad MAF will cause it to go limp..Probably several other causes..

 

It has happened 2 times in about 20,000 miles.
I've reset the ECU and then its ok.

 

the list is so long, need to be more specific.

 

The limp mode on FI cars is caused by the MAF voltage exceeding 4.87V prior to 4600rpm. It is more common on turbo cars, since they build boost sooner. If you have an eManage, then the voltage is clamped and you wont get a limp mode. On your SC kit, its likely that your boost is building right on the threshold of limp mode, and based on your driving, you are occasionally hitting it.

 

Sharif...Im getting 6.6psi at 4600rpm with the T-trim blower and it doesnt send me into limp . At what psi would send the volts over 4.8v ?

 

I looked at the R4 and there is a setting to clamp off the MAF volts at or below 5 volts . And its set for 0 to 30 psi/5vdc FS...what ever that means

 

I didn't start seeing this issue until boost was greater than 8psi.

--Steve

 

Couple points to be made..The MAF measures amount of air passing by the wire which is calibrated for temp and flow rate etc. Boost pressure is not the same as flow rate so trying to relate boost to MAF signal is not equateable..Not all similar boost pressures are the same. Same boost pressures on different cars are not the same relative to mass flow rate thru those cars..A 6psi boost on your car could flow more air than on my car. I could be more restrictive in exhaust. Also as I understand it the S.S box takes the stock MAF signal and manipulates it and sends its equivalent signal to the ECU to keep it happy...

 

Thats correct, and answers booger's question. This also explains why the limp mode can be sporadic thing. The pressure level where you hit the 5.0V is going to vary. On the R4 software, its clamping the voltage at 5.0V, just like the eManage, BUT if you are building boost/airflow fast enough to hit 4.87 prior to 4600rpm, then it can trigger the limp.

 

I'm not so sure that does answer Booger's question - at the risk of putting words in his mouth which from across the pond is playing with fire!

It doesn't seem to me to make sense to say that the MAF voltage is clamped (@5v) supposedly at high RPM whereas Booger is hitting 'high' boost (6.6 psi) at 4,600 rpm which you're saying triggers the CEL. Unless you're saying 6.6 @4600 is not that high - and compared to your motor I guess not

And the question still remains, WTF does 0/30 psi vs 5VDC mean?

Blame me for being dumb and BTW is a JWT clutch/flywheel good for stock ++ Vortech tunes. Sorry = got my question in there

 

I dont know understand why the 4600rpm is the point where it triggers it . But I understand that the same boost preasure on one car , may flow more air than the same boost on another car .

And the.... 0 to 30psi/5dvc FS ......is just the setting to clamp off the volts.....there are several other settings to choose from in the PWM mode

 

The JWT Flywheel and Clutch seem to be a good combo relative to stock as well as with a Vortech.. Only problem is the much discussed "cement mixer" acoustics...Not sure I understand what your referring to relative to what doesn't make sense??

 

Edited.

 

Please Talk about clutches in your own thread.
This is for ECU's in Limp Mode
Thanks
Timrod

 

i used to go into limp mode ALL the time, car was running extremely rich in lower rpm, around 3500 rpm in 2nd or 3rd gear it would go into limp mode, i got the car retuned to an almost perfect a/f by cpracing and hasn't done it once since then.