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Disabling Rich And Retard On Stock R33 Ecu

**RB2530**
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**RB2530** Proficient

**RB2530**

Posted
Posted

Hey all,

Just thought I would write a quick one on how to disable the Rich and Retard function on the stock R33 ECU by disabling knock sensors...

Disclaimer: Do not do this unless you understand what detonation is and what causes it. Basically it involves disconnecting the knock sensors and fooling the ECU that they are still there. I have done this modification because I am running forged pistons in an RB30 block and had concerns that piston slap on cold starts 'may' have been mistaken for pinging by stock ECU and therefore ECU keeps using R&R maps...Also the stock ECU would be very conservative wrt to knock detection and tuned for the acoustics of the RB25 block and not the RB30..

If are running stock RB25 there is no advantage in doing this and you risk f**king your engine....Don't do it...I have written this post just out of interest

First off R&R is triggered by engine knock and not excessive airflow. Airflow cut is is completely different and doesn't revert to R&R maps...R&R maps and R&R mode is a protection against bad fuel and once the ECU goes into R&R is slowly creeps ignition advance and leans back the AFR over time.

'Airflow cut is always active and actuates as soon as afm voltage exceeds a certain threshold. It is a constant and cuts ignition when the threshold has been exceeded...as soon as the afm v drops it brings back ignition...there is no learn/relearn function once it has been triggered'.

Now for how to do it:

If you just disconnect the knock sensors the ECU gives error code 55. When ever this happens the ECU reverts instantly to R&R anyway...Also if you ground the Knock sensor signal wire it also goes to error code 55 which again reverts to R&R mode...(maybe a few people reconnecting their knock sensors about now)...

The only way to do is to make the ECU 'think' that they are connected. The resistance of the knock sensors is about 500kOhms at DC. So what you do is disconnect the knock sensors and put 500kOhm resistor across the knock sensor input and ECU ground...On R33 ECU knock sensor inputs are pins 23 and 24. Check the picture for how I did it internally. I have actually used 2 1MOhm resistors and tied the two pins together and grounded them to the ECU chassis...

You should not really do this mod unless you have Nissan Consult gear. Then you can check you have done it the right way and not caused any errors.

I set ignition timing as per normal way but have worked out how much extra base timing I can run without excessive knock based on the all of the other mods I have done...It is no substitute for aftermarket ECU and good tune but I am happy with the 277rwkW I have been reliably making for the past 2 years with the stock ECU...

post-43757-1212573083_thumb.jpg

Mister25t Explorer

Mister25t

Posted
Posted

Nice work man.

So the extra engine noise of a modified engine over stock triggers R&R not the extra airflow, tha be right?

Bloody good thinking and thats got to be a record amount of power with a stock ecu. :)

**RB2530** Proficient

**RB2530**

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Posted
Nice work man.

So the extra engine noise of a modified engine over stock triggers R&R not the extra airflow, tha be right?

Bloody good thinking and thats got to be a record amount of power with a stock ecu. :)

Depends on what you mean by modded engine...If you run forged pistons the extra slap when the egnine is cold 'may' (and I say may here cause I haven't measured it) be seen by stock ECU as detonation...It shouldn't be a problem if you run cast pistons....

And yeah the extra airflow will cause ECU to drop ignition which is very noticable...It starts by dropping alternative spark and if bad enough will cut ignition right out until airflow drop below certain level...If you keep on the throttle it will stutter (like on rev limiter) because highairflow causes ignition cut which cuts engine, airflow drops, ignition comes back, airflow comes up again, ECU cuts spark and so and so....

joeyjoejoejuniorshabadoo Grand Master

joeyjoejoejuniorshabadoo

Posted
Posted

1)... why wouldn't this be usable on a 25? if you can disable R+R surely this must enable more power...

2)... why not just use this in conjunction with an aftermarket knock sensor and knocklight?

**RB2530** Proficient

**RB2530**

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once the engine warms and piston slap stops

would not the stock ecu stop R/R ?

YES and NO....the ECU stops R&R gradually...its function is to protetct against bad or low RON fuel so it once it is triggered it kind of goes into a learning mode when it brings back fuel and ignition parameters very slowly...

reseting ECU brings it back straight away but I think even then the maps are a little conservative...Not sure on this...never tried to measure it...

**RB2530** Proficient

**RB2530**

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Posted
1)... why wouldn't this be usable on a 25? if you can disable R+R surely this must enable more power...

2)... why not just use this in conjunction with an aftermarket knock sensor and knocklight?

Because if a stock RB25 ECU is running a stock RB25 bottom end and the ECU is detecting pinging, the engine probably IS pinging and R&R will save the engine.... piston ring lands are the achillies heel of the RB25...

**RB2530** Proficient

**RB2530**

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Posted
Hi Paul,

What parts are you using to make that power? I realise it's a rb30 but what turbo etc? Are you using any other piggy backs with the stock ecu?

Cheers

Turbo is GT3076R...Airflow cut is managed by playing tricks and games with boost curve which is done by camshaft timing....and other things...

**RB2530** Proficient

**RB2530**

Posted
  • Author
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ahhhh Dr Paul up to his usual engineering tricks....

;) long time no chat

Ahhh yes Dr Power FC how are you??...Hey when we did that power run I hadn't yet done this mod so it may have been in R&R to some degree...

Guilt-Toy Grand Master

Guilt-Toy

Posted
Posted

I might be on the dyno again this weekened if i can get all my mods installed on time.... PM me your phone number cos i lost it and if i end up gettin the dyno i will let you know...

It did feel like it was breaking down a little, i figured it was spark issue... could have been r&r as well. gap your plugs to .7 and lets chuck it back on ;)

ohhh and im good.. i got quite a few more mods done to the beast... getting her ready to race!

**RB2530** Proficient

**RB2530**

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Posted
I might be on the dyno again this weekened if i can get all my mods installed on time.... PM me your phone number cos i lost it and if i end up gettin the dyno i will let you know...

It did feel like it was breaking down a little, i figured it was spark issue... could have been r&r as well. gap your plugs to .7 and lets chuck it back on ;)

ohhh and im good.. i got quite a few more mods done to the beast... getting her ready to race!

Yeah I took the plugs out and they were copper, a bit tired and gapped to 1.0mm. Put in some Brisk plugs and gapped them at 0.7mm so Im keen to see if this fixed it...From what I know about R&R it is fairly slow to react and certain doesn't jump around...I think on a dyno you would just see richer mixtures and over the whole rev range and wouldn't look like break down typically does...Anyway

Are you going to Wakefield on the 21st June??

Guilt-Toy Grand Master

Guilt-Toy

Posted
Posted

yeah thats why i suggested its the plugs.

It would be interesting to see if you can break the 280rwkw mark! damn that would be cool.

I don't think i will be going to the track days just yet, i need to sort my car out and make sure its all reliable and setup right before i go do any racing. I need a few weeks.

Sydneykid Grand Master

Sydneykid

Posted
Posted

Interesting.............I have a a question though. If excessive airflow on its own doesn't activate R&R why do I see rich A/F ratios and retarded timing on the dyno even when there is zero knock? The Stagea suffers from this on cold days. I run 100 ron fuel (Shell V Power Racing) with the SITC retarding the ignition and so there is no knock that I can detect, but the A/F ratios drop from high 11's down to low 9's and the ignition retards 10 to 15 degrees. Maybe the ignition cut can explain the richer A/F ratios due to the resulting unburnt fuel, but it doesn't account for the retarded ignition. The R&R isn't as severe as when there is knock, but it's still there.

Cheers

Gary

Adriano Grand Master

Adriano

Posted
Posted

From what i have read on here of your setup, there are two factors playing here. IMO this mod is only preventing your ecu from dropping into the low octane(knock) map. R&R is basically cells in the mapping that do exactly that, and when you increase the airflow(at relatively low/mid rpm's it hits these cells. Coincidently these cells are where the knock detect is enabled, where it isnt at the higher rpm's. IMO there is another function in the ecu which detects excessive AFM voltage rise rate, and also exhibits similar traits to R&R, which is what results in the sawtooth power graph you see when you turn the boost up on a stock ecu.

Have you tried having the knock sensors on a switch, so they can be off when its warming up, and then turn them on once its warm. I believe it wouldn't change your power output, as its your other tricks that are giving oyu the power. As SK said this is merely fooling the ecu into believing there is no knock, so if there is no knock, in theory there should be the same outcome.

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