vance wrote:

snips...

Incidently gasoline direct injection is of course associated with
stratified charge techniques, and will probably result in less power per
displacement because the stratification will preclude the near uniform
stoichiometric mixture which you can get with good carburation or port
injection, and is a requirement for max power. They will run into the
same "smoke limit" problems that Diesels experience. You can see this in
the power ratings of the new outboards.
Vance

I like to say one HP = 550 lbs ft per second. Makes it clearer.
Force times a speed.

Part of the smoke problem with a diesel is the fuel is "throttled" and
not the air. Consequently when you slam open the diesel "throttle" the mixture is
momentarily too rich hence the black carcinogenic smoke. It takes a while for
the RPM to build up and pump more air to catch up with the increased fuel.

The opposite happens in a gas engine. The air is throttled so you get lean stumble.
The accelerator pump in a carb is designed to handle that. In a normal
EFI system the mixture is momentarily enriched until the fuel flow catches up.

In a diesel there is no accelerator air pump so the problem is much
harder to handle. The electric motor boosted diesel turbo charger was invented
to mitigate this problem. There might be a rate switch connected to the accelerator
pedal. Throttle by wire could also be used. When the pedal goes to the metal the
switch closes and speeds up the turbo charger. With EFI diesel injection this
can be coordinated to keep the mixture in the right range at all times.
Old fashion mechanical injection is not going to cut it.

Paul Lamar

vance wrote:

The "smoke limit" that I was referring to is the steady state smoke at
full throttle, where the total fuel injected has to be limited to well
less than theoretical because of mixing limits. Often owners defeat the
factory set limits, and indeed get more power, but at the expense of
very visible and possibly illegal levels of smoke and carcinogenic heavy
hydrocarbons - Vance

Judging by the number of trucks on the road putting that stuff out I would
say if it is illegal it is not enforced. Perhaps CA will make trucks go through
smog checks at the border :-)

Paul Lamar
 
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