Stock vs MTM data
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Stock vs MTM data
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There was some concern about richness of the charge mixture on chipped engines. I made a graph of the ratio of mass air flow (grams/sec) to fuel injection time (milliseconds). This will indicate if the engine is running leaner or richer than a stock set-up. Above 3500 rpm the MTM chip is richer. A second graph was made of the mass air flow readings. Previously posted was a graph of commanded, turbo and manifold pressures. It showed that at high speeds a greater pressure was commanded and more pressure was produced but the pressure was lost at the manifold. High speed power was also shown to be lower with the chipped engine. Mass air flow readings substantiate that greater flows are not achieved at high speeds. If the turbo's compressor is limiting total flow then increasing pressure (with its subsequent reduction in efficiency) will only further limit flow.
<IMG SRC="http://im1.shutterfly.com/procserv?si=00002937301920010623041421352.JPG&ps=0 &rx=640&ry=480">
There was some concern about richness of the charge mixture on chipped engines. I made a graph of the ratio of mass air flow (grams/sec) to fuel injection time (milliseconds). This will indicate if the engine is running leaner or richer than a stock set-up. Above 3500 rpm the MTM chip is richer. A second graph was made of the mass air flow readings. Previously posted was a graph of commanded, turbo and manifold pressures. It showed that at high speeds a greater pressure was commanded and more pressure was produced but the pressure was lost at the manifold. High speed power was also shown to be lower with the chipped engine. Mass air flow readings substantiate that greater flows are not achieved at high speeds. If the turbo's compressor is limiting total flow then increasing pressure (with its subsequent reduction in efficiency) will only further limit flow.
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Joined: Apr 2000
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When we did the Dyno Day this spring we found out several things about chips vs OEM ..
1.At higher rpms all chips (MTM, GIAC, APR) began to run rich compared to the OEM. JPCliff and I were 'wondering outloud' about this characteristic and he came up with what I feel is a plausible answer...high speed knock is controled by rich A/F ratios. Also soon as the A/F began to run rich there was a proportionate decline in torque and HP.
2. In comparing 2 separate TTs with MTM ECU/FM exhausts against the OEM ECU it was found that at around 6300+ the OEM setup was producing slightly higher HP but that situation was occurring in the 'declining' hp/torque mode for all the engines (eg all engines had past their peak ratings and were in decline).
3. The obvious advantage of the chipped cars was that there was a noticeable increase in HP and torque in the rpm ranges that were most often used in day to day driving and even in spirited driving...that is 2400 to 6000 rpm. Both MTM'd TT dynoed got 300+ lbs torque in the 5400 rpm range.
4.When I was driving at Summit Point (2.1 mi track) I did notice the power drop at 6500+ rpm and as such had to adjust shift points...but this only could work due to the much higher engine outputs in the 5000+ rpm range. A specific example was increased exit speed coming out of turn 10 into the long straight away...by keeping engine in the high 6000s rpm range terminal speed going into turn 1 (120 deg into a second mild turn) was 120 mph...shifting out to higher gear and bringing engine down into the 5000 to 6000 rpm ranges increased terminal speed to around 132 mph.
My thoughts on the issue...
2. In comparing 2 separate TTs with MTM ECU/FM exhausts against the OEM ECU it was found that at around 6300+ the OEM setup was producing slightly higher HP but that situation was occurring in the 'declining' hp/torque mode for all the engines (eg all engines had past their peak ratings and were in decline).
3. The obvious advantage of the chipped cars was that there was a noticeable increase in HP and torque in the rpm ranges that were most often used in day to day driving and even in spirited driving...that is 2400 to 6000 rpm. Both MTM'd TT dynoed got 300+ lbs torque in the 5400 rpm range.
4.When I was driving at Summit Point (2.1 mi track) I did notice the power drop at 6500+ rpm and as such had to adjust shift points...but this only could work due to the much higher engine outputs in the 5000+ rpm range. A specific example was increased exit speed coming out of turn 10 into the long straight away...by keeping engine in the high 6000s rpm range terminal speed going into turn 1 (120 deg into a second mild turn) was 120 mph...shifting out to higher gear and bringing engine down into the 5000 to 6000 rpm ranges increased terminal speed to around 132 mph.
My thoughts on the issue...
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