Background:
Further testing of the Mabotech M600 turbocharger with the GESi cat section of the exhaust removed and replaced with a catless exhaust.
Test Setup:
The GTI is set up as follows:
- Mabotech M600 (0.58 A/R turbine) turbocharger
- Russell Road and Racing IS48 E40 ECU tune
- Eventuri Intake
- MST Performance turbo inlet hose
- DBV2 turbo inlet elbow
- 034 Motorsport TMD
- aFe Power charge pipes
- Majesty Competition IC & FMIC
- Stock “Euro” intake manifold
- CC Design 4″ catless downpipe
- CC Design 3.5″ catback exhaust
Engine and vehicle data is logged in fourth gear, starting around 2,000 RPM and ending around 6,500 RPM.
Test Results:
Note: In the following charts M520 tune corresponds to the catted test session and IS48 v7 tune corresponds with the catless test session.
The test conditions are similar to the previous test with the catted exhaust, but was a few degrees cooler outside and the Ethanol percentage in the fuel was slightly reduced.
The removal of the catalytic converter helps to increase the rate that boost pressure rises.
The reduced backpressure also produces a reduction of the turbo’s wastegate duty cycle.
The faster boost onset with the catless exhaust corresponds with a greater acceleration rate up to the point where the boost curves coincide, around 4,500 RPM.
The next chart shows the turbine inlet pressure of the M600 configurations and also the Shuenk IS48 turbo which was tested with an IS38 turbine wheel (IS48) and a 5+5 splitter wheel (IS48T).
The M600 turbo combined with the catless exhaust has the lowest turbine inlet pressure once boost pressure plateaus.
The next chart shows the engine pressure ratio.
(Engine Pressure Ratio compares the pressure on the exhaust side of the engine to the pressure on the intake side of the engine)
The next chart presents the pressure data as Engine Delta Pressure (Boost Pressure − TIP).
The Virtual Dyno estimated power curve for this pull is shown next.
Conclusions:
The Mabotech M600 turbocharger is tested with a catless exhaust and results were compared with the catted exhaust.
Unsurprisingly, turbine inlet pressure decreased with the removal of the GESi cat from the exhaust. Boost onset and initial acceleration rate increased and the turbocharger wastegate duty cycle decreased.
Notably, the Engine Pressure Ratio never exceeds 1, meaning the exhaust turbine inlet pressure is never greater than the intake manifold boost pressure. This indicates this specific turbine/housing/exhaust combination has enough flow capacity, at this boost level, that it’s never forced into a backpressure-limited region.