Piston Slap: Depressurizing Compressed Air Engines?

Sajeev Mehta
by Sajeev Mehta

Maxim writes:

Just saw your post about running out of questions. Just wanted to say that you have a fan in Montreal, Canada! Love the subjects you guys talk about!

Everyone is talking about electrification and hybridization, but battery cost is a big negative point. PSA (group Peugeot Citroen) has developed a hybrid air system using compressed air as an alternative to electricity. A very smart and cost effective system. Where is that system now?

Why are the manufacturers not using tech like this to reduce their fleet MPG?

Sajeev answers:

The answer is almost always money, honey.

Peugeot isn’t risking it because they’d take a bath. Without the government incentive, why would a manufacturer put their eggs — ANY eggs — in a Hybrid-Air system basket?

The R&D costs, the durability and safety testing of components/subsystems/the whole vehicle, production/marketing of the final product must all be considered. I reckon this “moonshot” is a dangerous investment: only Tesla has the juice (and dat market cap) to make cars while often losing money.

There’s nothing wrong with moonshots: the Toyota Prius is proof. Between a Federal boondoggle Partnership for a New Generation of Vehicles that (not?) surprisingly produced zilch for would-be buyers, the California ZEV initiative, and whatever Jim Press was alluding to, Toyota had ample reason to give their hybrid system a shot in Japan and the USA.

I’m not gonna speculate to the validity of Hybrid Air Systems in the real world of motoring: it’d be awesome to see it hit the road to see the pros and cons firsthand.

But follow the money and you’ll totally see why it had to die.

[Image: Shutterstock user Syda Productions]

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.


Sajeev Mehta
Sajeev Mehta

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  • Vehic1 Vehic1 on Sep 29, 2018

    golden2husky: Oh, yeah - them thar smarty-paints sah-in-tists is a-gittin' rich, pickin' on them POOR fossil-fuel comp'nies, whut ain't got NO muney! A ex-purt with orange har, done tole me!

  • Makuribu Makuribu on Sep 30, 2018

    As Scotty might say, "Ye cannae change the laws of thermodynamics, Jim!" The energy efficiency involved in compressing and expanding air is very low. In the bottom of a mine where you might run in to pockets of methane, you can operate vehicles by running an air hose down from a honking big compressor, and plugging it in to a modified ICE engine. It's not efficient, but it avoids explosions. Your bulldozer or pickup truck is tethered to a hose, but it's in a mine, not driving on streets. Compressed air engines, like fuel cells, are only applicable to very limited applications where overall thermodynamic efficiency and cost is superseded by some other requirement, like operating in explosive atmospheres or outer space.

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