"Big" 16G Compressor Map


Despite what some DSM and other sites may indicate, the following is the correct map for a TD05H-"big" 16G (verified by MHI).  What quickly becomes apparent is the high pressure ratio which allows high boost.  I suspect much of this is due to the large exducer/inducer ratio on the compressor wheel.  A downside to the high pressure ratio is a slightly lower compressor efficiency at lower boost levels.  Better peak efficiency could be attained by using a TD06 housing (the "big" 16G wheel was designed for use with the larger compressor housing):




The following is the same as above except the compressor housing was switched from a TD05H to a TD06.  Unfortunately, MHI only mapped it out to a low shaft speed of 130,000 rpm.  It would be nice to see it mapped to at least 145,000 (like above).  The problem with the TD06 housing is size, it is difficult to find enough room in our cramped engine bay; mounts, fan shrouding, firewall and more may need to be modified.




And how does this compare to the stock TD04-9B?, look below (TD04-9B in red & TD06-"big"16G in blue).  I must first thank co-worker Garry McKissick (small car platform powertrain engineer) for obtaining the map with Mitsubishi Motor's concurrence to make it public.


The text on the graph pretty much says it all, i.e. if you want more power (more air flow), you'll need to upgrade turbos and boost higher.  More on TD04-9B map here.  Note how the TD04 spins to 180,000 rpm to achieve the flow the "big" 16G can obtain at 105,000 rpm.  This is an extreme example where the TD04-9B is maxed out, but the trend holds up everywhere to varying degrees.



I used the following inputs to generate the engine demand lines.  Note that the volumetric efficiencies are extremely high and represent a modified engine with minimal backpressure, ported heads, and perhaps even requiring bigger cams.



There were many assumptions made during these calculations.  One being that the volume filled during every two crank revolutions was equal to only engine displacement.  Volumetric efficiency aside, it could be more or less than this value (displaced volume) depending on how much of the exhaust gas is scavenged from the combustion chamber during the exhaust stroke.  For instance, if you have high back pressure before the turbo (TIP - turbine inlet pressure), you may trap more exhaust gas in the combustion chamber (higher than intake boost pressure) resulting in less than the displaced volume accepting fresh intake charge.  On the other hand, even if the pressure upstream the turbo is higher than the intake pressure, the inertia of the escaping gases out of the combustion chamber during the exhaust stroke may allow for some scavenging and more than the swept volume of the cylinder may accept fresh new charge.  None-the-less, this is close enough to tell me the "big" 16G is a decent match for a moded 3S engine.


The high pressure ratio is good for high boost but a good intercooler will be needed to make up for the lost efficiency.  In short, not the most efficient compressor wheel, but can support lots of boost.


The next step in this model could be to factor in intake temps and calculate air density, but I've already violated enough gas laws.


For the hell of it, here is how a Turbonetics single T66 compares (using all the same variables except that now there is only one turbo):





since August 7th, 2002


Last Updated: 08/08/02 07:50 PM