Why Electronic Throttle Bodies Are Ruining Modern Manual Shifts

Rev hang is a conspicuous problem for a lot of modern manuals, and most of the time, it's an electronic throttle body that's to blame
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In a lot of ways, electronic throttle bodies are very good. One perhaps unexpected benefit of ditching a traditional cable-operated setup is a potentially more linear torque curve since response can be tuned however the engineer desires.

As Engineering Explained, erm, explains, electronic units are also better for efficiency, but there is a side effect of this - rev hang. Heavy flywheels are usually blamed for this, but on modern manuals, rev hang is usually down to a deliberate choice in the way the throttle body is set up.

Jason takes us through in-depth using his trusty whiteboard, but to summarise, it’s all down to the wastage associated with suddenly shutting off the throttle. Bleeding it off slowly is much more efficient, but that comes at the cost of fast gear shifts feeling much less satisfying.

Why Electronic Throttle Bodies Are Ruining Modern Manual Shifts

The problem is often worse with direct port injection, where there’s usually a little fuel still making its way into the combustion chamber when the throttle closes. A slower closure can ensure the fuel/air mixture isn’t too rich, lowering emissions and fuel consumption.

We shouldn’t be too mad about this - manufacturers are up against it when trying to comply with ever more stringent emissions regulations, so if there’s a way to make less nasty stuff belch out the tailpipe, they’re going to want to do it. Plus, some cars have more aggressive mapping on sport/dynamic modes that allow for faster closure of the throttle, cutting down on hang.

Is rev hang an issue for your car?



No rev hang on my car with a throttle cable and port injection :D
Not so great emissions tho…

06/25/2020 - 10:43 |
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06/25/2020 - 13:57 |
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Matthew Henderson

The car in which I noticed rev-hang the most was the 1.4 Hyundai Kona. It’s a great car, but shifting is a horrible experience because it’s nearly impossible to get it to shift without it jerking. But what it comes down to is DI is better, right?

06/25/2020 - 10:47 |
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With 1.4 liters, just very slowly and no jerky. Who needs to shift fast with a 1.4 liter car? haha

12/23/2020 - 05:13 |
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Andrés Cely Herazo

I’ve had the experience of driving a VW Gol and a Skoda Rapid. Both of them have electronic throttle bodies and they are a bit uncomfortable. Doing rev matching is not easy as their response tends to feel laggy. By now I prefer using traditional mechanical throttle bodies.

06/25/2020 - 16:13 |
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I drove a Genesis coupe 2.0 some time ago… The revs even went up when you pressed the clutch, unless you would go off the throttle a second before… So stupid

06/25/2020 - 16:29 |
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Myrmeko (#CTSquad)

Plus, it can break all together. Like how the has pedal failed completely when i was at the driving school.
I felt something was wrong. I didn’t know it had a name.
The pedal also had the weirdest sensitivity. The sweet spot for constant speed was about a milimeter.

06/25/2020 - 17:01 |
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<EV owner has left the chat>

06/26/2020 - 14:29 |
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I find my Clio 3 RS 200 isn’t too bad for rev hang, heel and toe is fairly easy. Not a fan of the electronic steering though.

Cable throttles were much better for general driving, can be smoother

06/29/2020 - 08:39 |
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