DFCO (deceleration fuel cut-off)

[berry]

hi dudes
do berettas come stock with DFCO (deceleration fuel cut-off)?
thanks!

[Slinky]

Yes I believe they do @109mph for most, I've been told it's safer to change that and modify it to shut off the spark instead of the fuel so that it doesn't spike lean when it happens, It can all be modified with a DHP tuner

[RobertISaar]

ummm.... wrong topic. that's a speed limiter. and fuel vs spark cut could be argued for hours, but fuel cuts have worked fine for decades.

DFCO is the ECM cutting fuel when the engine is in an overrun condition(relatively high RPM, but very little to no throttle).

and pretty much everything EFI GM has ever made has had it.

[Slinky]

Oopz Just woke up and was tired whenever I read that post sorry

[woody90gtz]

I love watching the wideband peg lean going down a hill! haha

[berry]

thanks for the replies guys. woody, that sounds great! I think I could need a wideband too, hehe

[Rettax3]

Yes I believe they do @109mph for most, I've been told it's safer to change that and modify it to shut off the spark instead of the fuel so that it doesn't spike lean when it happens, It can all be modified with a DHP tuner

ummm.... wrong topic. that's a speed limiter. and fuel vs spark cut could be argued for hours, but fuel cuts have worked fine for decades.

DFCO is the ECM cutting fuel when the engine is in an overrun condition(relatively high RPM, but very little to no throttle).

and pretty much everything EFI GM has ever made has had it.

People can and will argue whatever they like, but no manufacturer cuts-off only spark for speed-governors: -Hmmm, let's shut off spark to a high-revving engine while at speed to keep it from accelerating the car any faster, but let the injectors continue to dump fuel into the engine/exhaust system, you know, for safety reasons... Argument ENDED.


-Sorry, I don't mean to come off sounding like an @$$, though I probably do. Slinky, aren't the governors set for 114 or 115 MPH? Is it different year-to-year? I know most speedometers aren't really accurate, but my '90 'Retta used to shut off at ~118 indicated, which seemed like ~114 actual, assuming the 'Your Speed Is' signs were accurate and the speedometer error in that car was linear (e.g., if 30 actual MPH showed as 31 MPH, then the car would be traveling at 60 MPH when the speedometer indicated 62, and so-on). I also remember hearing someone say that the Berettas were governed for 114, and thought that it seemed right... It was a long time ago anyway, I could easily be wrong on this.

[Asylum]

Let me get my .02 in here.
It is RPM based as well.
Had a huge problem with the 3500 when first swapped.
Kept hitting the limiter until Rodney finally disabled the damn thing.
I wanted a 6800 shift point and the ECU was having no part of it, LOL!
FWIW

[Slinky]

I believe OBD 1.5 four-speed automatic Beretta's all shut off at 109 mph, i could be wrong but I have gps'd mine and it has never gone over 109 before I had the cut off bumped up to around 120 mph.. Other berettas from different years or transmissions might be different I'm not the expert to ask but I just know that your speedo gauge in the dash is not very accurate Just like the RPM gauge...

[RobertISaar]

94-95 L-body 3100 = cut at 112, back on at 109.

[Rettax3]

94-95 L-body 3100 = cut at 112, back on at 109.

Okay, so that sounds pretty close to what I had heard, and certainly close enough to what I experienced with my '90 that I couldn't say for sure that it was any different. I never did hit those speeds with my '95 3100 Z-26 regardless. I think my niece did when she had it though... When the engine was supposed to be in break-in from getting a new top-end, too. Oh well, it was her car at the time...
Asylum, are you talking about the rev-limiter, or electronically-controlled auto-trans shift-points (4T60E vs TH125), or are you saying that the car actually has a different top-speed governing depending on if you are in top gear or not? Would any of our cars be able to exceed 109 MPH in anything other than top-gear without exceeding red-line? I'm sure several people here know the gear-ratios right off the top of their heads and could answer that without thinking too hard, if it matters...

[Asylum]

Asylum, are you talking about the rev-limiter, or electronically-controlled auto-trans shift-points (4T60E vs TH125), or are you saying that the car actually has a different top-speed governing depending on if you are in top gear or not? Would any of our cars be able to exceed 109 MPH in anything other than top-gear without exceeding red-line? I'm sure several people here know the gear-ratios right off the top of their heads and could answer that without thinking too hard, if it matters...

Ya my bad

[woody90gtz]

A 4t60e will hit about 140 in 3rd and over 80 in 2nd. My 5spd just hits 4th gear around 90.

And as far as the speed limiter is concerned...I hit mine in the Z26 around 110, but in my 90 GTZ the speedo was well over 120 and did not cut out. I have no reason to believe that car was not 100% stock.

[RobertISaar]

but in my 90 GTZ the speedo was well over 120 and did not cut out. I have no reason to believe that car was not 100% stock.

believable... i only have 1 1990 Q4HO L-body BIN (ANFU), speed limiter is set for 143.

[woody90gtz]

That makes sense, then. I had it pegged on "unleaded fuel" going down a little hill wide open...on a state 2-lane highway...haha To be 16 again.