Piston Slap: Depressurizing Compressed Air Engines?

Sajeev Mehta
by Sajeev Mehta
We’re committed to finding, researching, and recommending the best products. We earn commissions from purchases you make using links in our articles. Learn more here
piston slap depressurizing compressed air engines

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

More by Sajeev Mehta

Join the conversation
2 of 33 comments
  • 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.

  • Carsofchaos The bike lanes aren't even close to carrying "more than the car lanes replaced". You clearly don't drive in Midtown Manhattan on a daily like I do.
  • Carsofchaos The problem with congestion, dear friends, is not the cars per se. I drive into the city daily and the problem is this:Your average street in the area used to be 4 lanes. Now it is a bus lane, a bike lane (now you're down to two lanes), then you have delivery trucks double parking, along with the Uber and Lyft drivers also double parking. So your 4 lane avenue is now a 1.5 lane avenue. Do you now see the problem? Congestion pricing will fix none of these things....what it WILL do is fund persion plans.
  • FreedMike Many F150s I encounter are autonomously driven...and by that I mean they're driving themselves because the dips**ts at the wheel are paying attention to everything else but the road.
  • Tassos A "small car", TIM????????????This is the GLE. Have you even ever SEEN the huge thing at a dealer's??? NOT even the GLC,and Merc has TWO classes even SMALLER than the C (The A and the B, you guessed it? You must be a GENIUS!).THe E is a "MIDSIZED" crossover, NOT A SMALL ONE BY ANY STRETCH OF THE IMAGINATION, oh CLUELESS one.I AM SICK AND TIRED OF THE NONSENSE you post here every god damned day.And I BET you will never even CORRECT your NONSENSE, much less APOLOGIZE for your cluelessness and unprofessionalism.
  • Stuki Moi "How do you take a small crossover and make it better?Slap the AMG badge on it and give it the AMG treatment."No, you don't.In fact, that is specifically what you do NOT do.Huge, frail wheels, and postage stamp sidewalls, do nothing but make overly tall cuvs tramline and judder. And render them even less useful across the few surfaces where they could conceivably have an advantage over more properly dimensioned cars. And: Small cuvs have pitiful enough fuel range as it is, even with more sensible engines.Instead, to make a small CUV better, you 1)make it a lower slung wagon. And only then give it the AMG treatment. AMG'ing, makes sense for the E class. And these days with larger cars, even the C class. For the S class, it never made sense, aside from the sheer aural visceralness of the last NA V8. The E-class is the center of AMG. Even the C-class, rarely touches the M3.Or 2) You give it the Raptor/Baja treatment. Massive, hypersophisticated suspension travel allowing landing meaningful jumps. As well as driving up and down wide enough stairs if desired. That's a kind of driving for which a taller stance, and IFS/IRS, makes sense.Attempting to turn a CUV into some sort of a laptime wonder, makes about as much sense as putting an America's Cup rig atop a ten deck cruiseship.