Why does it seem like sometimes people have a certain amount and others say it's "a lot" or "to much", then in other applications it doesn't seem so. I understand how a turbo works.... sort of, but this is something i've been wondering about for a while now so I thought i'd ask. Give me the simplest way possible, as I am not really to car savvy lol. Sorry if this seems like a dumb question.

 

If not being tuned properly, too much boost will lean out the AFRs to dangerous levels which can result in going Kaboom with your engine. Too low boost will net too rich AFRs and will certainly result in very poor performance and foul up your plugs, etc.

I'm no gearhead too, but I've read enough info here to at least understand the concept a little bit.

 

yeah I see what you are saying, it just seems like sometimes a guy will say they are running say 27 psi... and people will say that's to much and then others will say they are running 27 psi and it's ok and they could run more. Does a bigger turbo allow for more boost with an equal set-up to a car that just previously had a smaller turbo?

 

Typically fuel is the key to higher boost. 91 octane and you can run to around 26 psi. 93 octane and you can up it some more, lets say 27psi. All cars act differently, but at some point you will run into knock. E-85 can take much higher boost levels, someone around here ran 30 psi on the stock turbo.

Now here is the kicker. The more air your engine can flow, the less boost it needs. Take Hollywood's car. He makes excellent power with his boost in the low 20's. But he has cams and a FP Green.

And you are correct, one man's overboost is another man's underboost. lol It really is setup dependent.

 

I would say the stock turbo should not really be pushed above 27 psi. So in this case it is more turbo dependent.

 

Think of it this way. You need air and fuel for combustion. Stoichiometric or Theoretical Combustion is the ideal combustion process during which a fuel is burned completely. There is a corelationship between the two for optimum ignition. Boost is just compressed air, and the PSI is the amount of compressed air. The amount of fuel to use is dependant on boost and vice versa. Different cars have different set ups, so some may run out of fuel or run out of boost for their set up for safe combustion. AFR is what tuners use measure the combustion, which allows them to denote whether a combustion cycle is too rich or too lean.

 

That's too general of a question. Too much boost on a stock engine setup is not enough on a fully built car. A lot has to do with fuel setups, power goals, what people think is possible... It could refer to running too much boost on a turbo making it work so hard, all it's pushing is hot air. Then you get a big turbo that someone is pushing 20psi through and it's not enough to make the turbo worth having. Your question can mean a number of things.

 

Also, boost effectively increases compression, so a motor that has higher compression to begin with may not like as high of boost.

PSI is a measurement of force against an object, not volume of flow. Depending on the design of your turbo and the airflow characteristics of your engine 20lbs of boost may be 300CFM and way under the efficiency range of both, or it could be 800CFM and way over the efficiency range of both. Then there are situations where 25psi may be leaving the motor wanting more, but more air than the turbo can efficiently compress (so it has to heat it and wheez). Both items need to be matched to eachother, and designed for a specific purpose.