Down shifting and gas consumption

[Santana'sCB7]

Does the 5 speed JDM dump gas when down shifting. It seem I am noticing a bit of this or maybe my float is off.

[92LxCoupe92]

depends what sort of downshifting you're doing.. lol

[deevergote]

An engine spinning at 3,500 RPM has 50% more combustion events per minute than an engine spinning at 2,000 RPM... so yes. More fuel is being used when you downshift, as the injectors are firing more frequently.

[cp[mike]]

if the Throttle Position Sensor (TPS) signals to the ECU that you aren't pressing on the gas, then it should know to not add any extra fuel. It shouldn't drastically affect mileage if you are engine braking. But if you are downshifting to rev up and accelerate, yes, of course it will use more gas.

[lbus9168]

of course it will use a tiny bit more, thats logical, but Blipping the throtlle/double clutching is alot better for your car anyway. I do it every single change.

[deevergote]

I do it all the time because it's fun... though I've read conflicting arguments regarding the benefits (or lack thereof).

[Santana'sCB7]

Thanks

Ok thanks guys, wasn't to sure beings though it does seem like it when engine braking, it seem to break a lot easier when doing it this way verse clutch and brake seem harder on breaks. No worry for the most part. Thanks

[92LxCoupe92]

if the Throttle Position Sensor (TPS) signals to the ECU that you aren't pressing on the gas, then it should know to not add any extra fuel. It shouldn't drastically affect mileage if you are engine braking. But if you are downshifting to rev up and accelerate, yes, of course it will use more gas.

exactly what I meant by what sort of downshifting hes doing

[GhostAccord]

Based on the street tuning that I have been doing and datalogs that I have read. Engine breaking or downshifting with a closed throttle uses 0 fuel. Most PGMFI programs use a fuel cut when engine RPM and/or vacuum are high and the TPS signal is below a certain %. AFRs usually shoot to 22:1.

Each manufacturer will have different hysteresis for this type of fuel cut. XXXX RPM @ XX TPS % = Fuel cut. And then there is usually a re-engagement point as well. under XXXXRPM or over XX TPS % and fuel is added. Some manufacturers go as far as to us a fuel and spark cut.

[Santana'sCB7]

Thanks

Thanks for the info guys, I'm not to deep in the car specs and knowing how all the mechanics of them work, but can do so of my own labor that's about it. So thanks again

[oni_cb7]

I get why people downshift while slowing down to come to a stop. It's fun.

However, I've never understood any benefit for this. If you know you are coming to a stop, then why use the engine braking to slow down while downshifting?

I'd much rather replace worn out brakes than a worn out clutch....

[deevergote]

I agree. Brakes are cheap and easy to replace. I can replace my brakes 2-3 times for the price of a clutch! (especially since I've paid to have my clutch changed on my Fit the last 3 times it went... $1500 a pop!)

My new CR-Z recharges the battery when engine braking, so I try to do it in that car. It's weird not to shift into neutral when slowing down. I'm afraid I'm going to forget I'm in gear and stall out! (I wonder what would happen... the engine shuts off when stopped anyway.)

I downshift to accelerate, and I heel-toe downshift when taking a turn or an exit ramp (whenever it's safe and useful to do so.) That's probably why my first thought regarding downshifting is actually fueling the higher-revving engine!

[GhostAccord]

I have yet to have to replace a clutch due to wear. I Engine brake/downshift to a stop all the time! Your clutch shouldn't slip while downshifting/ ngine breaking! If you are shifting properly and not feathering or slipping the clutch. down shifting should have only a slight effect on your clutch wear.

I was always taught never to neutral brake!

Not to mention, putting the car in neutral while you brake still consumes fuel. The ECU is programmed for both moving and stationary idle. So you have no fuel cut when you roll in neutral. The ECU maintains idle even while rolling.

[GhostAccord]

I am even downshifting in my current winter beater, and it's an automatic.

2-each-his-own!

[cp[mike]]

i usually try to see if I can get the car to decelerate to a stop without using the brakes at all. I ALWAYS engine brake!