just been told its a engine that has a different a AFR to 14:7

is that true, sorry to ask but sounds something interesting as just heard thats what people are aiming to do now

so just wondering

 

correct, one that can burn a lean mixture, i.e. AFR greater than 14.7, or lambda greater than 1.

it's done by localising a burnable mixture to the spark, but having a weak mixture in the rest of the cylinder.

honda have been doing it for years, and their engine was the original development reason for the wide band lambda sensor

 

I would guess it is an engine that has been designed to run stoich and leaner on low loads.

Maybe not a big thing these days but i know ford made a point of putting it in their sales lit when they first started doing it.

 

so how can you make a lean burn engine and why dont cossies have that

or they just shite with the end power result ???

 

it's done by localising a burnable mixture to the spark, but having a weak mixture in the rest of the cylinder.

And as nick says, thats how its done!

 

You asked for this Ginge..............Lean burn...........YB style:

 

Cause the head was designed in the 80s before such things had been invented by clever people like those at Honda.

 

plus, cause its expensive.

 

ahhhh

so maybe rotory engines aint the only hope

a leanburn rotary would be a idea though, get ya rough book out chip and design one for me so when i sell the cossie i can have a RX7 with a decent engine

 

The humble CVH had a lean burn head. Most development work was done in Europe in the 80's, with the idea of increasing fuel economy. Very lean mixtures, of upto 70:1(!) were acheived without missfires. The sole purpose is fuel economy on light loads. There is no point running an engine lean burn on heavier loads. Mosrt development stopped in the 80's due to emission reuqirements. Lean burn engines throw out large quantities of polluting NOX gases. Strict laws came into place in 92, 86 and 2000 which would not allow these pollutants.

Modern catalytic convertors require a stoich mixture to work properly, which is why todays engines run 14.7:1 There have been attempts in the laboratory to make catalysts that can convert the high volumes of NOX hases to harmless nitrogen and oxygen, but even in the lab, they dont work too well.

My S2 runs 15:1 on cruise, which gives very nice economy, very low CO emissions, but high NOX emissions.

 

Rick

 

Also, does anyone remember the 'bishi GDI? the D was direct injection, rather than diesel. The idea was that u could place the injector in the combustion chamber, aimed at exactly the right place. This place would be where tumble and swirl would be at it's highest, giving the best hope for clean combustion. On this engine (and other jap stuff, as well as an ameican only CVH head used until v recently) used valves in the inlet ports, to alter their shape and induce this swirl.

This technology of inducing and burning the lean mixture had been around for a good while. There were also air injectors, which added extra air into the combustion chamber. The problem was emissions. Mitsu managed to develop a CAT that worked, but, it was easily poisoned by sulpher. It's only now that we are really starting to get petrol that is very low in sulpher, and it's all becoming a viable tecnology. European manufacturers don't seem that interested at the moment.

 

So now we know what it is, can someone explain why it is ???

Better fuel economy

 

Better economy!

 

I have a vague recollection of an early 80's 'Tomorrows World' show where Maggie Thatch had gone to japan where they had gone all lean burn instead of adopting catalysts and the Uk was going to follow suit .... but we didnt and adopted the cats instead.
Looking at it now from a greenhouse gas point of view - less CO2 and more NOx seems like it should have been the way to go.

 

later cvh's had a leanburn head I'm fairly sure that aint jap

 

So did the early CVHs'. I had an old C plate Mk4 with a lean burn head.

 

The Fifth Gear Lotus had a lean burn engine

mark

 

I'd be more worried if somebody run an AFR of less than 14.7 at cruise.


DazC, mk4 is the later CVH.

 

I thought he meant late late as in 1989 late, not the later design with the crank and oil pump as well as the different head.

 

[quote="JesseT"]I'd be more worried if somebody run an AFR of less than 14.7 at cruise.
quote]

How do you mean? Heat issues?

 

im shit at this quote stuff..

 

The 1.4 had a lean burn head

 

they wern't really proper lean burn, but the intention was there. The 1.4 was intoroduced with the rest of the 1.6 non inj lean burn range. Have u seen the 'true' lean burn american CVH head? Guess u must have living there

Rick.

 

Yeah, some of the american CVH stuff is bonkers. The weird flaps in the inlet manifold are a bit mental.
I did fancy buying an old Escort GT out here and converting it to partial RS Turbo spec but it wouldnt get through the smog check and besides the Escort out here looks awful !

 

That Escort is one ugly mother... With the right management, u could easily get it through the tests, especually if u "adjusted it" for the check. I'm guessing it's something simialr to our MOT? Or is it more often/random than that?

The heads over there are shit from a power point of view, but the later block with the thicker cranckcase looks interesting

 

Rick, just click the quote button over there!! ------------------------------------------------------------------->

 

Daz - i did! i Swear! It doesnt like me!

 

Crap efficiency and not high enough plug temperature to keep the cold plugs clean.

 

My final year group project at uni was to design a rig to measure tumble for perkins diesel engines. What a ball-ache