20b single turbo and a MAF conversion?
Thread Starter
working towards the goal
Joined: Apr 2004
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From: Georgia
20b single turbo and a MAF conversion?
I've been reading alot in this thread that talks about converting the Rx7 from a speed density based system to a MAF based one. Most of the thread talks about keeping the sequential twins but I know alot of us are doing single turbo upgrades while we have the chance. It's a great idea to keep from over boosting. A pop off valve would work good to prevent boost spike problems but I like the idea behind a MAF conversion.
Have any of our wonderful 20b engineers tried this?
Have any of our wonderful 20b engineers tried this?
Thread Starter
working towards the goal
Joined: Apr 2004
Posts: 402
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From: Georgia
The "need" supposedly is to give the car the ability to detect sudden increases in air flow (boost spike) and compensate with added fuel. Something the rx7s ems doesn't do. Not even an aftermarket one. Because all the engines, minus some FCs, have a MAP sensor based system.
Rotorhead
Joined: Feb 2001
Posts: 9,136
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From: Charlottesville, Virginia, USA
Originally Posted by Drag'nGT
The "need" supposedly is to give the car the ability to detect sudden increases in air flow (boost spike) and compensate with added fuel.
Boost spikes are almost always caused by a poor wastegate. If you don't want boost spikes, then buy a good, new, wastegate for your single turbo application.
A boost spike is a sudden increase in pressure, right? Then why do you think that a MAP (Manifold Absolute Pressure) sensor cannot detect a boost spike?
A speed-density system uses a MAP sensor to determine the y-coordinate for fuel injector control. Therefore, when the MAP sensor detects a boost spike, it will trigger the ECU to move up to the next load (y-coordinate) cell for increased fuel injection. For example, if the engine were running at the point shown below (x = 4000rpm, y = 71% load), which injects 9.31ms of fuel, and then a boost spike occured, it would move up in load to the 79%, 86%, or higher load point, where you can see that the fuel injection rate increases to maintain value (10.00ms, 12.00ms, or higher) set for that point.
Rotary Enthusiast
Joined: Jan 2003
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From: planet earth
Originally Posted by Evil Aviator
All types of EMS will detect sudden increases in airflow, except for the Alpha-N types, which you will probably only find on competition NA engines like the R26B.
Boost spikes are almost always caused by a poor wastegate. If you don't want boost spikes, then buy a good, new, wastegate for your single turbo application.
A boost spike is a sudden increase in pressure, right? Then why do you think that a MAP (Manifold Absolute Pressure) sensor cannot detect a boost spike?
A speed-density system uses a MAP sensor to determine the y-coordinate for fuel injector control. Therefore, when the MAP sensor detects a boost spike, it will trigger the ECU to move up to the next load (y-coordinate) cell for increased fuel injection. For example, if the engine were running at the point shown below (x = 4000rpm, y = 71% load), which injects 9.31ms of fuel, and then a boost spike occured, it would move up in load to the 79%, 86%, or higher load point, where you can see that the fuel injection rate increases to maintain value (10.00ms, 12.00ms, or higher) set for that point.
]
Boost spikes are almost always caused by a poor wastegate. If you don't want boost spikes, then buy a good, new, wastegate for your single turbo application.
A boost spike is a sudden increase in pressure, right? Then why do you think that a MAP (Manifold Absolute Pressure) sensor cannot detect a boost spike?
A speed-density system uses a MAP sensor to determine the y-coordinate for fuel injector control. Therefore, when the MAP sensor detects a boost spike, it will trigger the ECU to move up to the next load (y-coordinate) cell for increased fuel injection. For example, if the engine were running at the point shown below (x = 4000rpm, y = 71% load), which injects 9.31ms of fuel, and then a boost spike occured, it would move up in load to the 79%, 86%, or higher load point, where you can see that the fuel injection rate increases to maintain value (10.00ms, 12.00ms, or higher) set for that point.
]
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