The history of turbocharging is
almost as old as that of the internal combustion engine. As early as 1885 and
1896, Gottlieb Daimler and Rudolf Diesel investigated increasing the power
output and reducing the fuel consumption of their engines by precompressing
the combustion air. In 1925, the Swiss engineer Alfred Büchi was the first to
be successful with exhaust gas turbocharging, and achieved a power increase of
more than 40 %. This was the beginning of the gradual introduction of
turbocharging into the automotive industry.
The first turbocharger applications were limited to very large engines, e.g.
marine engines. In the automotive engine industry, turbocharging started with
truck engines. In 1938, the first turbocharged engine for trucks was built by
the "Swiss Machine Works Saurer".
The Chevrolet Corvair Monza and the Oldsmobile Jetfire were the first
turbo-powered passenger cars, and made their debut on the US market in
1962/63. Despite maximum technical outlay, however, their poor reliability
caused them to disappear quickly from the market.
After the first oil crisis in 1973, turbocharging became more acceptable in
commercial diesel applications. Until then, the high investment costs of
turbocharging were offset only by fuel cost savings, which were minimal.
Increasingly stringent emission regulations in the late 80's resulted in an
increase in the number of turbocharged truck engines, so that today, virtually
every truck engine is turbocharged.
In the 70's, with the turbocharger's entry into motor sports, especially into
Formula I racing, the turbocharged passenger car engine became very popular.
The word "turbo" became quite fashionable. At that time, almost
every automobile manufacturer offered at least one top model equipped with a
turbocharged petrol engine. However, this phenomenon disappeared after a few
years because although the turbocharged petrol engine was more powerful, it
was not economical. Furthermore, the "turbo-lag", the delayed
response of the turbochargers, was at that time still relatively large and not
accepted by most customers.
The real breakthrough in passenger car turbocharging was achieved in 1978 with
the introduction of the first turbocharged diesel engine passenger car in the
Mercedes-Benz 300 SD, followed by the VW Golf Turbodiesel in 1981. By means of
the turbocharger, the diesel engine passenger car's efficiency could be
increased, with almost petrol engine "driveability", and the
emissions significantly reduced.
Today, the turbocharging of petrol engines is no longer primarily seen from
the performance perspective, but is rather viewed as a means of reducing fuel
consumption and, consequently, environmental pollution on account of lower
carbon dioxide (CO2) emissions. Currently, the primary reason for
turbocharging is the use of the exhaust gas energy to reduce fuel consumption
and emissions.
HOW-TO-READ A COMPRESSOR MAP
using a map of a T04E 60 trim I will explain all the numbers on the map
1-left side, PRESSURE RATIO
(14.7 + amount of boost) / 14.7 = PR
so to figure out the PR for 8 PSI
(14.7 + 8) / 14.7 = 1.54 PR
2-bottom side, AIRFLOW RATE UNDER BOOST (LB/MIN on this map)
Most methods of calculation your engine's airflow rate will give you the answer in cubic feet per minute (CFM). However most compressor maps measure airflow rate in pounds per minute (LB/MIN). As some of you may know the weight of air varies with the temperature. To convert CFM to LB/MIN use the following numbers.
@ 48 degrees F : (CFM * 0.078125) = LB/MIN
@112 degrees F : (CFM * 0.070318) = LB/MIN
@175 degrees F : (CFM * 0.06251) = LB/MIN
Say for example our airflow rate is 500 CFM , and the temperature is 112 degrees F.
(500 * 0.070318) = 35.16 LB/MIN
*For those of you that know anything about ideal gas law, if you know a better way of explaining how to convert CFM to LB/MIN, your input would be appreciated. But please explain it in "laymans" terms, so that everyone can get a grasp on it.
3-dotted line on far left side of "ovals", SURGE LIMIT
It is important to try and keep yourself on the right side of this dotted line whenever possible. If you fall to the left of this dotted line you will experience compressor surge. This type of compressor surge will occur when there is too much boost, but not enough airflow through the system, usually this is between idle and the point at which full boost is reached. The chirping sound that can be heard is a result of the oscillating air. This sound is often described as a "Snakelike" sound or a che-che-che sound.
*staying in the "surge limit" area for too long could possibly damage your turbo.
4-numbers on far right, 46,020, 69,640, 83,972 etc, COMPRESSOR RPM
This is RPM at which the compressor fans will be turning. an average RPM is between 90,000 and 130,000. The line that branches out from each of these numbers that goes towards the surge limit line shows you the RPM range of the compressor fan across the entire compressor map.
5-78%,75%, 74%, COMPRESSOR EFFICIENCY
This is related to the temp of air and how much it is being heated up as it is being compressed by the compressor. A low number (60%) means that the compressor is heating the air more a high number (78%) means the air is not heated as much when it is compressed.
6-"Ovals"
I you look closely you will see that the compressor efficiency numbers usually sit right on top of one of these Oval lines. These Ovals show you the boundaries of the compressor efficiency at the different percentiles. Think of it as a topography map that shows you different elevations or changes in elevations. The innermost Oval on the sample T04 E 60" is not labeleb but it is probably 79% or 80%, so any where inside that Oval and you would be operating in the 80% range of that compressor.
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OR
to compensate for an intercooler.
on number one, with the formula:
(14.7 + amount of boost) / 14.7 = PR
you can figure to loose 1.5 psi in a pretty good intercooler.
so you can change the formula by simply adding 1.5:
(14.7 + 1.5 + amount of boost) / 14.7 = PR
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