Does The Ecu Store R&r?

[TUF250]

Hi all, I have been searching for an hour now and cant find the answer to this question.

I understand why r&r happens, cold night, afm maxes etc.

I have been having this problem, well the problem started one cold foggy night in melbourne. Ever since the car hasnt been the same again.

Does the ecu store the r&r protection mode or should it go back to normal after the engine ahs been shut off and restarted?

Cheers

[lachlanw]

the ecu self learns (trimms fuel and timing to what it thinks is good )

no it doesnt store r&R

get someone to plug a laptop into it and "Clear self learn" or reset it yourselft . you should do this after every mod really

[**RB2530**]

First of all R&R is triggered by excessive knock...The ECU 'does' remember this because it enacts Rich and Retard maps and slowly creeps back to the factory maps over time (unless of course excessive knock is detected again then it goes back to R&R and so on..) Resetting ECU does clear R&R unless there is a fault in the knock sensor. From memory it is either error 55 or error 53 for a faulty knock sensor. Btw disconnecting knock sensors will cause ECU to default to R&R.

What you are talking about (cold nights etc), I think, is air-flow cut which is 'not!' R&R. Air flow-cut happens when AFM exceeds a threshold voltage. The threshold increases with rpm. As soon as the threshold afm voltage is exceeded, the ECU cuts fuel and ignition. As soon as the afm voltage drops below the threshold voltage, fuel and ignition return, until the afm voltage exceeds the threshold again. It is a binary function.(ie air-flow cut is either on or off). There is no learning or memory involved. Turn the boost down (reduce air flow) and the ECU is happy.

R&R and airflow cut is about the most misunderstood topic on these forums.

[Adriano]

Sorry paul have to disagree, knock causes it to go into the knock map, which is richer and less timing, however R&R is generally referred to the cells in the fuel and timing map above which a factory car sees, where the fuel and timing maps are severely richened and timing pulled. It is easy to see ont eh dyno, add 5 psi to a stock setup, with no knock, and power figures will go all over the place, not fuel cutting.

[R31Nismoid]

^ Agreed. R&R is certainly not triggered exclusively by knock.

You can almost see it the same everytime around 4000-5000rpm where the typical 'dip' in the graph appears, AFR's go to shit and there is not one iota of knock being produced.

[rob82]

Agree with the adriano.

Alot of people dont realise that some r32 and most R33 ecu's will apply learned closed loop fuel corrections at open loop as well. So if your fuel trims are learning +10% of fuel in closed loop there will also be 10% extra fuel in open loop condition such as WOT.

[TUF250]

great information guys, this exaplains some of my problem that I am having trouble resolving.

If you send the computer into R&R or similar. Will this be registered with a fault code? I ran my codes the other day (using the paperclip method and engine fault light) and got code 55 - no fault found.

[R31Nismoid]

R&R is not a fault.

[paulr33]

i think it's important to list them clearly as the others have said, as they are different things

1) R&R or excess airflow cut or boost protection or boost cut or fuel or overboost protection

this is where the ECU detects too much airflow via the AFM signal and goes into a proteciton mode to save the engine from blowing up (or it assumes)

so the timing and fuel is mega retarded to protect itself for the duration of the "excess" and it is usually around 4000rpm to 4500rpm

after this "window" the ECU takes the protection off and car resumes normal power. this is obvious with std ECU and base mods and more boost

the usual result is the car boosts fine, then all of a sudden it feels flat and sluggish then as you reach the Redline the power comes back on normally

this R&R or protection is only applied during run time of the current cycle. that is, when you return to idle, or gearchange etc, the protection does NOT exist

2) ECU reverts low octane map

this occurs when the stock ecu picks up detonation from the knock sensor or picks up a knock sensor fault

the ecu revers to a lower octane map which is basically less timing and more fuel to protect itself.

from the knock sensor it assumes you have put in penis fuel and runs the low octane map

this usually occurs from penis fuel or too much boost / high intake temp

the result is the whole ECU TUNE runs on sluggish maps until you power off the car.

That is, the state of "low octane" map is permentant until you power the car off. so if you trip the too much detonation level once at any time

then you are stuck on the low octane maps until you power off the car and clear is "state"

[paulr33]

there are also other protection modes but i cant be bothered typing them all up

they are in the nissan service manual in clear english so its not hard to read

ie if the AFM signal is disconnected rev is capped at 2500rpm is another "protection mode"

[MBS206]

^ Agreed. R&R is certainly not triggered exclusively by knock.

You can almost see it the same everytime around 4000-5000rpm where the typical 'dip' in the graph appears, AFR's go to shit and there is not one iota of knock being produced.

The strange thing is though, if you watch your AFRs as you hit "R&R" the car leans out... So not really richer...

From what I've seen from the consult being connected, they just dump to 5 or 8 degrees worth of timing, fuelling stays the same and it reads "leaner" as the fuel hasn't all been burnt by the time it's going out the exhaust, and hence, reads lean.

[JonnoHR31]

never seen any read lean. this is my standard 25 with fmic, zorst and too much boost

[TUF250]

wow check that dip out!!

thanks for the information paulr33. Very nice to have that cleared up. seems to be alot of confussion in the threads that I have been searching through as to the differences.

When you say power off the car, do you mean just switch it off via ignition switch or actually power down the ecu and reset? I assume you mean ignition just want to be sure cheers mate

[R31Nismoid]

never seen any read lean. this is my standard 25 with fmic, zorst and too much boost

R&R @ it's finest

[paulr33]

yep just off at the key should be enough

ie at boot car the car clears all non-permenant errors etc and assumes clean slate

[TUF250]

ok so when you get the error codes fron the flashing check engine light they are just the stored codes?how does it decide what to store and what not to?

[paulr33]

the nissan service manual would give you some clues on this

im not sure what codes are stored and which ones arent

but R&R is a temporary measure applied in real time at the point of issue and it is not an "error code"

low octane map is applied to the state of tune and i dont even think low octane is an "error code"

ie i dont know if you'll get an error code

and im not sure ECR33 has flashing light style error codes?

i thought all diag was via consult and only HR32 had error lights on ECU

[TUF250]

i found a thread when searching. You use a paperclip or similar on the consult plug, bridge the bottom left two pins (thats if the mount is on the top) for 2 seconds, release the bridge, the check engine light flashes the codes and then bridge for another two seconds to clear codes. seemed to work for mine (1997 S2)

[nicr4wks]

there are also other protection modes but i cant be bothered typing them all up

they are in the nissan service manual in clear english so its not hard to read

Is this the partial service manual floating around the net or a proper fsm?