I think my Corvette has something wrong because normally when you're engine braking (was breaking ), the fuel consumption should be zero as it cuts off the fuel injection. But when I'm engine braking with my Vette, there's always some fuel consumption based on the computer. In faster speeds it's 99 MPG which seems fine (but actually if you change to metric it still shows 2-3 liter/100 km), in lower speed MPG is then lower, something between 50-99 depending on the speed.

It should be always zero. At least after couple of seconds engine braking, but now I can go e.g. downhills long time engine braking and computer shows some instant MPG not 99... Any ideas what could be wrong?

 

The injectors dont shut off completely as far as I know it just cuts the fuel way back. Engine has to stay running and wont do it without fuel.

 

Yeah ... you are confused .....if the car is rolling and using no fuel ..... your MPG is theoretically infinite .... Chevy just chose 99 MPG as the arbitrary cutoff .... they could have gone to .... say 300 MPG .... but I suspect the 99 limit probably keeps the "average" fuel mileage more accurate.

The instant mileage should show 0 MPG when you are not moving with the engine running (like at a stop light).

 

The only time it will show 0.0 is when you are not moving. If you are moving, there will always be a number. The DIC instant mileage is not entirely accurate, don't put too much stock in it. The engine is always using fuel whenever it is running. My method of engine braking will always use more fuel than actual braking. I blip the throttle and match revs (estimated) before letting out the clutch. It is easier on the drivetrain this way. Still, the fuel consumption is just a small fraction of what it takes to start from a dead stop (most of your consumption)

The best way to estimate your MPG is to take your trip meter reading since your last fill up and divide by the gallons till full on your next tank. This method is more accurate than the DIC.

 

DFCO on a factory tune only kicks in when you are slowing down from above 2100 rpms. Fuell will be turned back on below 1900 rpms. You also have to be above 30 mph.

 

yes but that would also depend on if stock or ?? and the tune (maf or map tables/fueling), etc. etc. play a role.
In some cases, when in dfco and, if using a afr meter and logging, may you see the BPW and DC go to "o".At that point you will then see the AFR jump very dramatically above 14.7:1. As stated above (depending on rpm look up in the ecm tables of your year) this would only occur through decell above 1600rpm. That should be the only time you see 'o' BPW (which would indicate the inj. shut down).

 

I generally try to avoid engine breaking

 

Thats what brakes are for

 

First reply with some real knowledge Does it really turn it back on already 1900 rpms? In most of cars it turns back on just before idle rpms. Maybe Corvette is just different then to maintain good acceleration if I decide to kick down

For other posters.. I use normally engine breaking to save fuel (because of zero fuel consumption) + save breaks of course. Normally fuel injection is shut down during engine breaking. During engine breaking engine doesn't need any fuel to run because it's just lowering RPMs

And yeah, I know Chevy has selected 99 MPG as max, that's why I checked metrics (litres per 100 km) which should be naturally 0 when engine breaking. MPG is zero when stopped e.g. in lights but on the other hand l/100km is then 99 So, to really see zero consumption in engine breaking you need to change to metrics (the E/M button under the Options button )

Ok, back to actual topic. So mseven said some mods could affect to this. I think only mods I have are K&N filter, some larger intake pipes + of course exhaust Could this really cause this problem? I don't think so, but on the other hand I don't know if someone has done some tunes or something that could cause this.. I have just fixed some intake air leaks, the plastic pipe between MAF & throttle body had "pleat" caused by some idiot's installation of mods which caused air leakage. It didn't help to this problem but seemed to fix cruise

 

OK, now I know we are talking to an idiot here .....

Hey veppe

It is engine BRAKING ... not "breaking" ..... if you "break" an engine (we have these ancient tools called dictionaries .... look it up) it will no longer work ...... it is "broken" ... it is unable to function. A "brake" is a device to slow something down ....

OK .... obviously hasn't passed 4th grade .....

oh and veppe .... you complete idiot .... doesn't matter if you use Metric or English units .... at a stop light with your engine running the trip computer is going to show either 0 miles per gallon, or 0 kilometers per liter

Read that very carefully idiot .... it is NOT "liters per kilometer" ... it is "kilometers per liter" ........ just as it is miles per gallon .....

The rest of what you wrote is meaningless .....

OK .... 2nd grade dismissed .... and veppe must stay after and write 100 times on the board ......

"I'm stupid not to understand what the trip computer and other people are telling me"

 

Have to somewhat agree with BlackZ06 on this. If the engine is breaking , pistons and heads etc. should be the real focus (not a Ford) If you're braking then you'll observe a favorable DIC None of this applies to Barack-ing.

 

The DIC read out is just like any other computer. It appears that in that section of the display they have allowed for 4 display spaces only or 99.9

 

Brakes are for braking. Eggs are for breaking.

Edit: Hey BlackZ06- Nice job restraining yourself to just two "idiot" usages in your post. I can see you're making real progress on the anger management.

 

 

Nice job Black Z06, I'm totally with you on this one!

 

Shhhhhhhhhh ....

that damn nurse is gonna be back with the medications any minute now ... don't let them know I've been back on the net unmedicated ...

 

Focus ... Ford ...

Braking .... Barack-ing ....

GREAT sense of humor

 

It taxes my mental limits(not to be confused with rev limiter) to compete with you BlackZ06

 

Ooh
What an idiot. Yeah, I'm not native in English, and I did a mistake when I wrote breaking instead of braking. I apologize that. You can try to write something in Finnish, let's then see how idiot you are if the conclusion comes from writing something in foreign language...

Besides, it is liters per 100 km. IDIOT Read this very carefully idiot: liters per one hundred kilometres What a stupid idiot barking someone first idiot and then writing something like that without even checking first how it really is

I can see that you're American and just used to MPG. I'm from Europe where liters per 100 km is used so I really know what does it mean You didn't even check. Stupid

You are really complete idiot
OK... BlackZ06... All grades dismissed .... and BlackZ06 must stay after and write 100 times on the board ......

"I'm stupid not to understand what the trip computer really says and I'm absolutely stupid idiot when publishing this out in public forums so that everybody can see my level of stupidity"



I'm sorry about flaming. I just had to answer back

 

I really hope that you didn't thought same about litres per 100 km with Black06 Otherwise we have at least two idiots here

I once more apologize my wrong word which definitely drove you crazy...