Francois
Thank you Francois. That is the best information we have on the stock
turbo
so far. Now what is that rule of thumb on turbine RPM? Here it is in
the Macinnis book on page 105. 2% increase in RPM per 1000 feet. 20%
faster RPM for 11,400 feet or 126,000 RPM. That combined with a couple
hundred degrees hotter exhaust ought to do the job on the turbine.
230 HP at .5 BSFC is 115 pounds of fuel per hour or 1.9 pounds of fuel
per minute. At 14.7 to one stoechemetric (s?) that is 28 pounds of air
per minute. My guess is the pressure ratio is about 1.2 to 1.4.
Looks like we are well off in the right regions of the T3 "60"
trim compressor map at 1400 feet. The super 60 trim is about the best
we can do in the T3 size but not good enough. So it is going to take a
TO-4 compressor wheel. That is possible and is known as a hybrid in
Turbonetics speak.
A larger compressor wheel should slow the RPM and put the stock turbo
in a more efficient place on the compressor map. My guess is a TO-4
"40" trim if that is mechanically possible. Perhaps it is also possible
by souping up the stock compressor housing.
I will attempt to measure the A/R ratio of the stock turbine
housing to get a better feel for just what this turbo is equivalent
to in Garret turbos.
Paul Lamar
Paul and Francois,
I know you wanted to test the possibility of stock Mazda turbos, but now
they have failed we may need to fall back on information given in past
postings.
My past notes indicate a TO4E-50 ( 50 trim compressor), with P trim exhaust,
with modified 1.3AR ratio housing- turbine wheel Inconel.
Intercooler Spearco ( small)
Boost 6.4 psi@ 6,500 RPM ( 43 " manifold pressure)
Boost control -Turbonetics " Deltagate".
Additional info gathered indicated AR inlet as .6, AR exhaust .96.
It pays to keep notes - hope it helps.
George (down under)
Plotting Francois's data on the TO4E-50 trim map is the intersection of the green
and the red line. To keep the air flow constant as one gains altitude
means you move straight up on the green line... roughly.
You can roughly identify the stock Mazda compressor by measuring the wheel
and comparing it to this chart.
Paul Lamar
Aubrey Thompson wrote:
Paul,
Some thoughts for the group that do not necessarily form a paragraph:
I haven't seen it mentioned that the Mazda turbos are Hitachi HT-18 (single turbo engines) and Hitachi HT-12 (twin turbo engines). Hitachi apparently made these only for OEM use, thus the lack of
data on them. The twin turbo Toyota Supra had HT-12's. At least one version of the Supra HT-12's had ceramic turbine wheels. Maybe someone can find some HT-18 info by looking to auto brands
other than Mazda. Our best bet for using the stock Mazda housings is to find a turbine wheel/shaft assembly with the fattest possible shaft that will fit the turbine housing and then pick a
compressor wheel with a largest possible major diameter. The bearings would have to be bored or changed to fit the fat shaft.
I'll have Ben's 20b turbos in a week or so. I intend to take them apart asap and measure everything.
A ram-air system that supplied 1 or 2 psi to the intake of the compressor would make a huge difference in the feasibility of this effort.
One other observation about the data from Francois, if the manifold pressure is measured at the intake plenum and the pressure drop across the intercooler is not accounted for, then the actual
pressure ratio for the compressor wheel would be higher than indicated.
Aubrey--
You are absolutely right and that is an excellent idea. Cheap to do in the bargain.
That should load down the compressor.
Paul Lamar
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