RS2.5 REV LIMITER

[j smith]

Can anybody enlighten me concerning what happens when you hit the rev limit.
The reason I am asking is I believe that I may have hit the limit because
the engine back fired through the intake but ran OK afterwards.

--

 

[Verbs Under My Gel]

Can anybody enlighten me concerning what happens when you hit the rev limit.
The reason I am asking is I believe that I may have hit the limit because
the engine back fired through the intake but ran OK afterwards.

--

On the Phase-II EJ25, fuel is cut at around 6500 rpm. You'll stop
(positively) accelerating. That's it.

How do you know you had a backfire?

 

[j smith]

Thanks for the info, (Verbs Under My Gel)

It certainly made a quite loud bang type sound which sounded like it came
from the intake. I would have identified a similar noise on other cars as
the mixture being too lean if it was intake noise so the fuel cut off theory
appears valid. I believe that on some cars power to the ignition coil/s is
cut when rpm limit is exceeded rather than fuel being cut off which can
cause the car to miss repeatedly as the engine speed ramps up and down with
the throttle held fully open.

I couldn't say whether the EJ25 motor would maintain its speed just under
the rev limit since I naturally backed off anyway. If the fuel cut off valve
is either on or off then the fuel flow would stop until the engine speed was
below the rev limit. Therefore the mixture would be correct air/ fuel to
begin and then (lots of air) / fuel at the limit which equals lean and hence
the backfire.

If the fuel cut out was a true regulator as you have suggested and not a
cutoff then the airflow would have to be reduced also to maintain correct
mixture at the rev limit with the throttle wide open.

 

[Verbs Under My Gel]

Thanks for the info, (Verbs Under My Gel)

It certainly made a quite loud bang type sound which sounded like it came
from the intake. I would have identified a similar noise on other cars as
the mixture being too lean if it was intake noise so the fuel cut off theory
appears valid. I believe that on some cars power to the ignition coil/s is
cut when rpm limit is exceeded rather than fuel being cut off which can
cause the car to miss repeatedly as the engine speed ramps up and down with
the throttle held fully open.

I couldn't say whether the EJ25 motor would maintain its speed just under
the rev limit since I naturally backed off anyway. If the fuel cut off valve
is either on or off then the fuel flow would stop until the engine speed was
below the rev limit. Therefore the mixture would be correct air/ fuel to
begin and then (lots of air) / fuel at the limit which equals lean and hence
the backfire.

If the fuel cut out was a true regulator as you have suggested and not a
cutoff then the airflow would have to be reduced also to maintain correct
mixture at the rev limit with the throttle wide open.

I'll dig through the service manuals when I get a chance, but most
likely the fuel is "cut" by the ECU ceasing to send signals to the
injectors.

 

[j smith]

Thanks (Verbs Under My Gel)

"j smith" <(e-mail address removed)> wrote in message

I'll dig through the service manuals when I get a chance, but most
likely the fuel is "cut" by the ECU ceasing to send signals to the
injectors.

 

[j smith]

Hi verbs,

It happened again when I was passing a truck and it hit the rev limit but
this time it did as you suggested and positive acceleration stopped. Pity it
didn't have a buzzer on it like some WRX's have to warn the driver that
revs were about to be limited. Never had a car that did that before,
normally one would keep going until torque ran out then change up a gear
when in a hurry. So I was halfway passed a long truck with oncoming cars
approaching and acceleration stopped. You don't study the tacho when your
busy passing, one normally watches the traffic.

 

[GTT]

Hi verbs,

It happened again when I was passing a truck and it hit the rev limit but
this time it did as you suggested and positive acceleration stopped. Pity it
didn't have a buzzer on it like some WRX's have to warn the driver that
revs were about to be limited. Never had a car that did that before,
normally one would keep going until torque ran out then change up a gear
when in a hurry. So I was halfway passed a long truck with oncoming cars
approaching and acceleration stopped. You don't study the tacho when your
busy passing, one normally watches the traffic.

No, you don't. Pardon my butting in here, but surely your ears can tell you
that
you're about to run out of revs! My 2.5L AT downshifts to hold a set speed
and
when it gets around 5K, I pull the plug very shortly. How fast were you
going to overrev yours? (sounds scary to me!) <g>