Fuel Cut ! I Got No Fuel Cut. Stock Ecu

[robots]

Hi!

I've been struggling to get my fuel cut running. RB20DET.

Motor was wired in a carb car. Car had a socket for nissan efi pump, but I didn't connect the wire from the ecu to fuel pump.

What I wanted to know is:

1)Will I regain fuel cut function if I get a wire from ecu to fuel pump relay ? So it will turn off fuel pump, hence fuel cut ?

Or if ecu turns of inj. for fuel cut, where do I look ? Inside the ecu for a modded chip ? LOL

Thanks!

Edited September 6, 2007 by robots

[blind_elk]

How is the pump wired now? At worst it should be wired through the ignition switch, so that turning the engine off should disable the pump.

[robots]

Its wired directly to to ignition switch.

What I wanted to know if how does the limiter work and how should I change the wiring for it to work ?

[blind_elk]

I'm pretty sure Nissan use a "spark cut" as the rev-limiter. (too many WRXs have melted pistons, because Subaru uses fuel-cut limiter).

[Strik3r]

i always thought it was a fuel cut and not a spark cut... ??

[robots]

So where does it cut fuel ? Fuel pump, or injectors ?

[OFENSV]

not a very safe way of wiring up a fuel pump straight to the ignition. I always thought it would cut the injectors not the fuel pump

[blind_elk]

IF a fuel cut is used, it will be by shutting down the injectors.

[bubba]

RB limiters cut fuel (probably injectors, easier for ECU to deal with) not ignition, if they cut ignition we'd have built in bee*r limiters

[robots]

Do u think there is a possibility to mod standard ecu to cut ignition ?

[JiN_MaN]

RB limiters cut fuel (probably injectors, easier for ECU to deal with) not ignition, if they cut ignition we'd have built in bee*r limiters

Bingo!

As for cutting ignition rather than spark, I don't think its that easy. I remember reading about it and it either couldn't be done or was too hard or was more expensive than buying a Bee*R Limiter. Best to ring a ECU tuning place like Dr Drift ans asking.

[abu]

Can someone confirm why they decided to cut fuel?

I mean, cutting fuel will definitely do more damage then cutting ignition? Excess ignition is usually what kills a motor not access fuel?

But there must be some logical explanation behind it, maybe simple as JIN_MAN said, its easier to cut fuel than ignition?

[blind_elk]

Bingo!

As for cutting ignition rather than spark, I don't think its that easy. I remember reading about it and it either couldn't be done or was too hard or was more expensive than buying a Bee*R Limiter. Best to ring a ECU tuning place like Dr Drift ans asking.

Why would it be so difficult? All it is is a piece of computer logic:

If <too many revs> then don't send a signal to injector.

Why would it be so hard to implement it as:

If <too many revs> then don't send a signal to spark.

As I said previously, too many WRX engines have melted pistons because Subaru chose to implement a fuel cut limiter.

[Duncan]

I'm pretty sure its a fuel cut too, and I'm surprised to hear it could melt a piston.

When the ECU tells an injector to shut, the cylinder is not firing at all, its not running lean - so I don't see how it can melt a piston?

Anyway, it is simple to disable rev limit in the software of the standard computer, so the one you have might have had this done already. However without hooking up the mapping interface to fix it I don't know how else you could put it back.

[JiN_MaN]

Why would it be so difficult? All it is is a piece of computer logic:

If <too many revs> then don't send a signal to injector.

Why would it be so hard to implement it as:

If <too many revs> then don't send a signal to spark.

As I said previously, too many WRX engines have melted pistons because Subaru chose to implement a fuel cut limiter.

When I said "As for cutting ignition rather than spark, I don't think its that easy." I was referring to an ECU tuner trying to chance the setting, such as Dr Drift.

[1400r]

dont think theres any problem with melting pistons as its a fairly hard cut

it feels like some just switched the engine off and I hit mine a number of times before I got a FCD fitted