too rich or too lean, any problem

[orlandopaulo]

is there any problem in mixture running to lean or too rich?? or are the only problems: too rich....consummes too much,,,, too lean......loss of power??

Im thinking of that because of a probable project for a turbo for my 172RS..

Thanks..

 

[orlandopaulo]

oh, the objective is 210-220hp turbo, intercooler, air filter, new program

 

[James20VT]

Well i must say.. going to the gym keeps me lean.. and i dont seem to have a problem with the rich part!! so id say the mixture is just right



LOL



couldnt resist

 

[Nick Read]

In theory, best power is at a ratio *slightly* richer than stoichiometric (the perfect air/fuel ratio). Richer than this is not really harmful to the engine but will not increase power and in fact will begin to lose you power the richer you go. You will also get problems like bore wash and plug fouling with too rich a mixture. And the obvious fuel economy problem.

Too lean is probably worse though. When you run too lean, you will still have a fuel economy problem because there is not enough fuel for the amount of air and its an inefficient burn, wasting fuel. The big problem is with detonation (pre-ignition): the leaner you go, the more certain it is to happen. This is a very common problem with turbo powered cars that are running more boost than usual, unless they take measures to stop it like using higher octane fuel, low compression pistons, water injection, bigger intercooler/chargecooler, ignition r****d etc.

If you were to plumb in a turbocharger onto your 172, without any other form of ECU reprogramming, and no means to deliver a lot more fuel, you would hit detonation straight away and be left with a big engine problem! As long as you can supply enough fuel, in the right amounts to match the boost that the turbo is providing, you can keep the air/fuel ratio correct - leading to the power you would expect when using a turbo.

 

[Captain Slarty]

yep, well said, and to add to that..

the limit on boost is the pressure the cylinder can handle and the ignition of a highly compressed mixture in a controlled way.

you would NEED to reduce the compression ratio by at least 3 points on a 172 !, you would NEED boost r****d and extra fueling as the std injectors cant handle it. you would also NEED an aditional or different ecu as the std maps will not allow the range needed.



Joe.

 

[orlandopaulo]

reduce?? do i?? why?? if i put nitro that is not necessary.. whats the diference??

Thanx

 

[Captain Slarty]

A turbo produce heat, and, as it is a std mix or normal air (just more of it !), burns in the same way as normal air, but gives increased pressure on burn leading to more power.

the flame burn at the higher pressure (of normal air) is extrmemley rapid and will lead to detonation, the only way to control this is to lower the mechanical compression ratio to lower the initial pressures, and control the flame front.

Nitrous has a higher o2 content, and the release of the gas causes an approximate temp drop at liquid to gas change of -127 deg F !!.. this rapidly cools the inlet charge (the charge is now denser)

the notrous oxide does not break down until heavily compressed (to > 500 deg F) well into the stroke.. at the breakdown point, as well as O2 being released, nitrogen is also released and acts as a buffer for the flame front to control too rapid a spread (leading to detonation)

there is no such thing happening with a turbo so you need to physically alter the parameters of the engine.

With NOS, the chemical change has the effect of negating or assisting these issues.

you cant compare one with the other Paul, its apples and oranges.

 

[Frosty]

With a turbocharger when the engine starts pulling boost, its as if you have upped the compression ratio because the cylinder is pressurised with ambient air (and fuel) before the compression stroke has even started.

With Nitrous Oxide, the gas is simply squirted in, and because it is so much more oxygen rich than the ambient air, not much of it is needed to produce the same effect as your avenage turbo setup. So no significant compression is made until the piston starts the compression stroke.

 

[orlandopaulo]

ahh ok... thanks for the explanations