Modern Manual Transmissions Engine Brake

I am a fervent advocate for manual transmissions. My last four vehicles have had 5 or 6 speed manuals. Two were Hondas, two are Jeeps. The older Honda had a two-stage variable valve timing. The older Jeep has no variable valve timing. The other two vehicles have continuous valve timing, which makes for very smooth power delivery, but they -at least in my opinion- also have very limited engine brake capability. Whereas my old Jeep and Honda engines would cut down speed on a downshift, I feel like the newer engines rev-up on the downshift without slowing down the vehicles much. Is variable valve timing the culprit? Could it be that the valves open up so much at the downshift and allow the engine to breathe freely as if it was accelerating instead of slowing down. In the case of my newer Jeep, the Pentastar engine uses speed dependent oil pressure to regulate the valve timing, so I am afraid nothing could be done to have a more effective engine brake. Does this theory hold water? Does anyone else experience good engine brake with other modern engines. Could the problem simply be in the more fuel efficient transmission ratios?

Variable valves are part of the reason. “Pumping losses” largely consist of the energy necessary to pull air into the cylinders, are what slow the car when your foot is lifted from the pedal. They also include the energy needed to push air out of the cylinders, but I’ll simplify the answer by only addressing pulling air in, and you can I’m sure extrapolate the flip side of the problem out. Pumping losses adversely affect fuel economy when your foot is on th pedal, thus engineers try to reduce pumping losses as much as possible. One of the way they attempt to do this is to optimize the valve timing under all operating conditions. Thus, less engine has less loss from pulling air in and slows the car less.

It’s also true that engines are getting smaller. In the quest to get higher mileage and still satisfactory performance, manufacturers are turning to smaller displacements with turbochargers and even superchargers. The small engines have to draw in less air, so the pumping losses are reduced. Turbochargers and superchargers are a part of this dynamic in that they pump air in, reducing pumping losses and reducing even further the engine’s tendency to “engine brake” the car.

I’m sure other factors like drivetrains with less inherent resistance and low rolling resistance tires add to the reduction in the car’s inherent tendency to slow too, but perhaps only to a much lesser amount.

My thanks go to Rod Knox, who only recently reminded me that it was the pumping losses that slowed the car.

I never depend upon engine braking. I just use the brake pedal to apply the brakes or…in the steep mountains…I just downshift one gear or two.

Today’s cars have the ability to reduce engine braking during coasting (for increased mpg).

Drive by drive by wire provides the ability to open the throttle a bit, and engine management can shut down the fuel injectors.

As TSMB noted, valve timing can now easily be controlled to also contribute to less engine braking.

I can’t comment for how widely this is implemented.

Both the cars we have use engine braking by automatically downshifting while in cruise control and the truck does it all the time, especially on hills when the attitude sensor, seems to pick that up. The bigger motor seems more effective as the smaller four seems to still gain speed albeit at a slower rate. I DONOT look at engine braking as a way of effectively “slowing down” a vehicle on a regular basis but more of a way of controlling speed. Being in the correct gear to begin with based upon your needs and the situation is more effective.

That’s why the the car provides owners with that option to preselect gears which the manual advocates. Dropping a transmission down a couple of notches is a no no just to come to a stop on a routine basis. Being in the right gear to begin with is more effective.

Have you tried engine braking in first gear? That will dispel any notion of limited engine braking capability. Modern engines seem to have reduced engine braking, but you are free to keep downshifting until you find the right gear for the situation

Brakes are cheap. use them or step up to a Hybrid and get regenerative braking…

I have 2 cars with variable valve timing and manual transmissions. One Honda, one Ford. Both engine brake very well although I use it sparingly. I’ve had a string of manual trans cars without VVT and all engine braked similarly and way better than auto trans cars I’ve had. I’m not sure there is a problem.

Brake pads are cheaper and easier to replace than engine bearings.

Though I whole heatedly agree that brake pads are cheaper then repairs to the transmission and motor, we often miss state the comparison. For the average driver who does not do their own brake jobs, they can run as high as $750 to $1000 on per axle as it isn’t the pads alone that get replaced before you can get out of there.

Judicious use of both is the best way to control speed. In modern cars, the motor and transmissions are designed to help control speed as much as the brakes are. When I drove my friend’s Miata (6speed manual) at sane speeds, it stayed in fourth in 35 mph zones and fifth in 45 mph zones. Letting up on the gas with out using top gear gives you immediate braking assistance. That’s the type of dual roll the brakes and transmission are meant to play with the new autos doing it automatically. It does save money on brake jobs and has little negative effect on the transmission and motor. We live on the side of a small mountain for nearly 20 years and we always engine brake going in and out, every day. We never had clutch or transmission or motor problems.

I rode so many motorcycles with two cycle engines during my youth that I got used to not having any engine braking.
Lifting off the gas pedal when you see a red light up ahead or even a green light that you know you won’t make, will do a lot more to “save your brakes” than aggressive use of engine braking will not to mention that your gas mileage will stop sucking.

B.L.E.: I totally agree. I drive a 2010 Kia forte SX 6 speed manual. When putting around town I use 3rd gear for 30mph or less and 4th gear for 35 mph up to 45mph. If I am approaching a stop sign or red light I close the throttle which is by wire and also have VVT. It seems to slow normally as far as I can tell even though it has a 2 speed differential which is 4.10 in reverse, first and second gear and 3.10 in third through sixth. I use fourth gear in mountain passes with no problems. I rarely use the 4 wheel disc brakes except to stop or for a downhill sharp curve. I also turn off traction/stability control on curvy dry roads as it tends to engage at Grandma speeds and is rather rough and annoying. I asked the salesman if traction/stability control could be turned off and he replied yes but why would anyone want to? That would be me. I no longer drive anywhere near limits on curves and still know what I’m doing!

@sgtrock21‌ I wonder if it’s Kia’s stability control at fault? Because I drive a Subaru and have traction and stability control, and I almost never notice it kick in. Then again, maybe I’m oblivious, but the only time I’ve felt it was on an icy road. I can skid the back end out on sharp corners a bit, though I try not to…

I had my front pads replaced at 60k, then those new pads lasted until I sold the car at 150k. If the situation calls for it, ie going down a steep hill, I’d engine brake in first or second. I could have changed my oil every 7500, but given how much I engine braked, I changed every 5000. No damage to the transmission nor clutch as I rev match every downshift. The engine was running great, exceeding epa mileage estimate the last time I drove it.

I drive an automatic, but around town I often leave in in 3rd to save braking and my painful foot.
Yesterday, after driving on the highway for 30 miles, I said to my passenger " you know, my engine sounds a bit louder than usual"… whereupon I realized I was still in 3rd. No harm done except to my ego… the engine was well within its operating range. So now it’ll probably wear out in 499,000 miles instead of 500,000 miles. Oh well. Woe is me.