Compression ignition gasoline engines

bartlettj wrote:
NOx emissions are a big problem with compression ignition engines. I wonder if we will see exhaust fluid there too.

Mazda is still using a spark plug as well for finer control over the ignition, it's kind of a hybrid.

Not strictly compression ignition 100% of the time.

They explain how it works and how they control NOx emissions here:

Mazda Press Release

Very interesting stuff. I would love to see if they could make this work with the BMW tech that uses no throttle valve on a gas engine. What kind of efficiency would we be seeing then!

“If” I’m not mistaken, NASCAR engines run somewhere around 15 (or so) to 1 compression, and get 5+ mpg .....at 200 mph and near 9000 rpm. High compression seems to be working pretty well for them! Of course they are not required to meet EPA standards.

NOx emissions are a big problem with compression ignition engines. I wonder if we will see exhaust fluid there too.

Boils down to the ultimate PSI on the piston top...factored by many other attributes...

Like the stroke...which begets the length of the crank lever arm pushing on the crank shaft...and having more PSI on the piston top...has more pounds pushing on that longer lever arm

CI (compression ignition) requires a higher compression to ignite the fuel charge. Diesel requires a higher compression than gasoline. Factored by diesel having more BTU's per unite measure over gasoline...which begets higher PSI on the piston tops

Pre-ignition becomes a lesser issue with gasoline when there is no fuel in the mixture...until the 'direct injection' squirts fuel (gasoline) into the CC...but there is a runaway if the injection is before TDC...why higher oxtane is preferred...but...not necessary. That can be managed by multiple squirts (today's injectors are now fast enough to have several squirts for each Otto Cycle...The main difference between Otto cycle and Diesel cycle is how the heat is supplied to initiate combustion. However, in practice, a compression ratio of 20 can be achieved in a Diesel engine. Therefore, the Diesel cycle efficiency rises up to 64.7%.)


There is even a combo setup in testing...manifold injection of gasoline and diesel/gasoline inside the CC. This cleans the intake valve that direct injection gasoline has a problem with (Ford's ecoboost)

Been waiting/watching GDICI for a few years...wish it to become mature enough and after market folks offering something for my 1996 7.4L big block...

Posted By: BenK on 06/01/14 04:29pm

Comment that the 'fashion statement herd' has driven the OEM's to drop
the 'truck' from most all SUV's

I keep my vehicles forever and with the latest on these trucks and even
vans, will keep my GMT400 Suburban even longer

Yes, the small block is very capable, but nothing like a big block. Again
say it is like trying to explain sex to a virgin... :)

To back that up with experience, I LOVE small displacement ICE's that
spin up there...but...not for my trucks. Closest to that would be my
Silverado (see sig) and it's 5.7L that used to beat up stock muscle cars
My 2 seater's 3.1L (hogged out 2.7L & diesel crank, CC'd, cam'd,
flowed, matched, etc...etc) is rated ~350 HP and red lined at 7K
(builder says good for 8K, but I'm not going there with an in-line six
circa 1969)

Waiting for the day I decide to rebuild the 7.4L...noodling forced fed
in some fashion...along with a better cam and breathing...or even
GDICI components...if can find them

A 5 speed manual too...sorry Jeremiah...back to your topic

I checked out the Excursion when it came out. Not enough capacity
compared to my Sub. Again when they refreshed the engine options. Nope,
still not up to my Sub's performance. Didn't like the diesel in either
the Sub or Excursion.

Do prefer the live axle front, but not the way Ford did it. Love my
IFS, but dislike it much off roading.

Get 7-8 towing a +8.5K, 28foot boat from sea level to Lake Tahoe.
City is 10MPG. High way is 12.5MPG and some times (often enough to
claim it) get 15.2MPG fully loaded with my volleyball team going to
tournaments (6'4 guy tallest and gals 4'11 with all seats filled) with
gear on the rack and back

John B sent me a Suburban link that I've only glanced at...but a half
ton Sub going for near $100K is nuts and again driven by the fashion
statement herd. Have talked to many of this crowd and when ask them
if they are willing to scratch their sides from the head lights to the
tail lights...get a weird look and ask me 'why?'....

It is NOT a truck to them, but the latest 'station wagon' or 'mini
van'...so 'car' attributes trumpets truck attributes

Towing HEAVY is lost to the OEM marketing departments...

Also, if you look at GMT400's...careful...the brakes are truly awful
but can be made GOOD to almost GREAT. I've out stopped many cars
and a 5 series BMW among them

I had a higher horsepower Volkswagen that had compression ignition if you didn’t put 110 octane fuel in it. Made a lot of power (for a ‘68 Volkswagen) but wouldn’t have lasted long. I lowered the compression ratio to limit the detonation. I could see the benefits if you could control the fuel delivery and timing well enough to make it work. This new technology is great. I would love to be able to sit down and talk with the engineers that design it to hear what they did to make it work.

CaLBaR wrote:
The higher the compression in an engine the more efficient it is and the better the gas mileage. More power too!!

Bingo....

Gasoline engines were limited in compression ratio because of detonation, the higher the compression, the greater the efficiency and power. Recent engines have been getting better by controlling the fuel delivery with advanced injection systems. Apparently this new engine has even better control by burning fuel as it is injected, that takes extremely high pressure. If this is the case, the compression ratio is likely very high to take advantage of compression ignition.

The higher the compression in an engine the more efficient it is and the better the gas mileage. More power too!!