how much boost can a f22a1 handle

[awolanin21]

Not really lol i just know that they are decent turbos

[deevergote]

Then please don't waste anyone's time. If you don't actually know what's good for a given motor, then you could very well be giving bad advice. I don't want to see anyone blow up their motor because they trusted bad advice from an unknowledgeable member.

[Phate]

Ooooo knowledge, do explain.....

Okay, I'd be glad to explain it for anyone who is interested. Sorry to take a couple days, I was pretty baked a couple nights ago and wasn't really in a mindset to explain things. Kinda am now as well, but sometimes that lets me simplify things even better.

Looking at compressor maps (the graphs I have in this post), there are several irregularly-shaped "rings", which are referred to as "efficiency islands". These are the areas in which the turbocharger is working well (above 70% is pretty good) to compress air easily. The lower efficiency percentage, the more heat the compressor is releasing into the pressurized air.

The red line on the graph represents the air demands of the engine.

I made a similar point in this thread. Posts #9 and #11.

I'll say a lot of the same things that I did then, and probably use the same two turbo examples and graphs.

Lets start with the basics:

A turbocharger is an air pump. An engine is as well. At a given rpm and load, to achieve a given power level, an engine is going to need a given amount of air. Boost happens when the turbocharger produces more air volume than the engine uses. Because of this, you would think that 8psi is 8psi is 8psi, regardless of the turbo used. As far as volume air flow is concerned, this is correct. However, there is another factor involved in the measurement of airflow, and that is Mass Air Flow, a measurement of the amount of air molecules there. Volumetric air flow is effected by temperature, and Mass Air Flow is not.

Lets compare two fairly common turbos, a T3 50 trim (decently sized turbo for a mild street setup) and a Holset HX35 (commonly used in budget high power setups). Both are modeled on a 2.2L engine making 300hp at the crank. I picked this number, as it has started to max out the efficiency of the T3, assuming rediculously low charge temps are maintained. In reality, the 50 trim would have maxed out long before this due to the hot (thus low density) charge temps.

Notice that the 70% efficiency island only extends out to about 27lb/min or so, and at that point the pressure ratio is around 2.7 (2.7*14.7psi (atmospheric) = ~39-40 psi (absolute) - 14.7 (atmospheric) = ~24-25psi boost)

Here is the map for the holset.

Other than the fact that this turbo is 70% efficient all the way out to around 50lb/min, if you look at when this turbo is flowing as much air (by mass) as the other turbo maxes out its 70% efficiency island at (27lb/min), the holset is only at a pressure ratio of about 1.6 (1.6*14.7 = ~23-24psi - 14.7 = ~8-9psi boost).

Same amount of air molecules (what actually matters to the engine), less boost.