Which Standalone ECU is the best?
Senior Member
Joined: May 2001
Posts: 1,436
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For you Subie guys, I'd suggest getting a UniChip. They work for absolute shyt on the Tiburons and Elantras here, but more than a few WRX guys have had MASSIVE increases of power with a Unichip. Of course, this is only a piggyback though...
Still, do you know Nathan from the I-Club, who now works for TurboXS and used to live in New Mexico? For a long time, he held the record for the fastest North American WRX -- ran like a 12.3 in his on one of those ISHI VF33's.
He was using a Unichip at the time.
Now that he popped both head gaskets, I've had a chance to see what kind of evil he has stuffed under the hood
No, he's not using the Unichip anymore, but when he WAS, it was able to help him produce more power than his motor could live through.
That reminds me, I need to call him...
Still, do you know Nathan from the I-Club, who now works for TurboXS and used to live in New Mexico? For a long time, he held the record for the fastest North American WRX -- ran like a 12.3 in his on one of those ISHI VF33's.
He was using a Unichip at the time.
Now that he popped both head gaskets, I've had a chance to see what kind of evil he has stuffed under the hood
No, he's not using the Unichip anymore, but when he WAS, it was able to help him produce more power than his motor could live through.That reminds me, I need to call him...
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Joined: Jul 2002
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One question about the piggy backs; As the beta ecu will eventually correct for a piggy back such as the s-afc if running the new fuel maps at all throttle positions and rpm's (or so I have been told), will the more sophistocated piggy backs(unichip, smt-5i) have the same problem? I don't think that anyone wants their piggyback ecu'd turbo tib, over time, eventually going back to the stock fuel/ignition maps on its own, do they?
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Joined: May 2001
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On all piggyback devices (S-AFC, Greddy E-Manage, SMT-5, etc), the computer will only learn around them if you try to modify fuel delivery during NORMAL driving.
the differentiation here is OBD2 in closed loop versus open loop operation.
When you're just dinking around the city or cruising down the highway at low throttle, the onboard computer is running in OBD2 closed loop mode. This means that the computer is following the generally-accepted rules to supply fuel: based on incoming air mass, coolant temp, air temp, RPM's, etc. But in closed loop mode, it is ALSO watching the O2 sensors.
When in closed loop mode, it uses the O2 sensor readings to make slight adjustments to the fuel delivery, because at light load the car can run much leaner without damage -- thus sucking less fuel and emitting less carbon monoxide/dioxide.
This is where the car ''learns''.
But when your foot is on the floor, the computer switches to OBD2 open loop mode. This mode is only used under heavy load, and it doesn't even TRY to learn. It instead just goes something along these lines: FUEL DUMP! It just throws fuel at the problem, because overly rich will not cause damage like overly lean would.
The piggy-back computers should only modify fuel when your foot is on the floor; ie open loop mode. This way, the computer only works on the information it's being fed and doesn't attempt to learn around it.
On an S-AFC, this is why you always leave the Lo throttle maps alone (if you're running stock injectors) and only modify the Hi throttle maps. You also must adjust the throttle points so that Lo is around 75% or higher and Hi is around 90% or higher... This is to ensure that fuel changes are only made when the computer is in open loop mode.
If you're running bigger injectors, the story changes quite a bit.
the differentiation here is OBD2 in closed loop versus open loop operation.
When you're just dinking around the city or cruising down the highway at low throttle, the onboard computer is running in OBD2 closed loop mode. This means that the computer is following the generally-accepted rules to supply fuel: based on incoming air mass, coolant temp, air temp, RPM's, etc. But in closed loop mode, it is ALSO watching the O2 sensors.
When in closed loop mode, it uses the O2 sensor readings to make slight adjustments to the fuel delivery, because at light load the car can run much leaner without damage -- thus sucking less fuel and emitting less carbon monoxide/dioxide.
This is where the car ''learns''.
But when your foot is on the floor, the computer switches to OBD2 open loop mode. This mode is only used under heavy load, and it doesn't even TRY to learn. It instead just goes something along these lines: FUEL DUMP! It just throws fuel at the problem, because overly rich will not cause damage like overly lean would.
The piggy-back computers should only modify fuel when your foot is on the floor; ie open loop mode. This way, the computer only works on the information it's being fed and doesn't attempt to learn around it.
On an S-AFC, this is why you always leave the Lo throttle maps alone (if you're running stock injectors) and only modify the Hi throttle maps. You also must adjust the throttle points so that Lo is around 75% or higher and Hi is around 90% or higher... This is to ensure that fuel changes are only made when the computer is in open loop mode.
If you're running bigger injectors, the story changes quite a bit.