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Old 02-24-2016, 12:50 AM   #1
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Default Prep question after small off season engine changes

So I have a 1999 sport that is currently a dedicated track car. The only street driving it does it back and forth to the track. Over this off season did a few budget engine upgrades, the bp5a ecu (The extra 500 rpm will make a major difference at my local tracks) the exhintake swap and installed a 01+ exhaust manifold. The car seems to run and idle well, but I lack the knowledge on the ecu and how much tuning/adjusting it does if any.

My question is with these changes do I need drive around for a week first to the ecu can learn and adjust or just drive to the track and it will be good after that short drive?
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Old 02-24-2016, 04:57 AM   #2
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Holy Moly, cant tell if your joking or not...if not hold on for the replies....clench butt cheeks tightly and maintain a good sense of humour...

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Old 02-24-2016, 10:07 AM   #3
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The stock ECU is not going to have a problem adjusting. It just doesn't do much of it except at cruise. At WOT it will go open loop and not respond to any changes. The problem is that the changes you made to the volumetric efficiency will not be compensated for by the ECU. If it now flows a slight bit more air there won't be additional fuel added to make use of it.

An aftermarket ECU is the best way to go. The most common in the Miata world is the Megasquirt.
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Old 02-24-2016, 11:16 AM   #4
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The stock ECU is not going to have a problem adjusting. It just doesn't do much of it except at cruise. At WOT it will go open loop and not respond to any changes. The problem is that the changes you made to the volumetric efficiency will not be compensated for by the ECU. If it now flows a slight bit more air there won't be additional fuel added to make use of it.

An aftermarket ECU is the best way to go. The most common in the Miata world is the Megasquirt.
Thanks for the reply. My question was if the ecu just responds(timing,fuel etc) to sensor input just at a static point in time or if it averages out input value over a period of time. It sounds like at WOT (90% of the time) it will run the richer stock map and not do any adjusting.

Engine management is the area I need to learn. Proper engine management will probably be my next purchase but that'll have to wait since I just dropped half the value of the car to buy xidas.
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Old 02-24-2016, 11:33 AM   #5
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The only thing the ecu "learns" are the fuel trims and the emissions readiness monitors
Drive it around a little bit and you're fine.

But like six said: there's potential you're gonna have a bad time if the mods you did increased breathing enough to be out of range of the oem ecu.
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Old 02-24-2016, 11:47 AM   #6
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The only thing the ecu "learns" are the fuel trims and the emissions readiness monitors
Drive it around a little bit and you're fine.

But like six said: there's potential you're gonna have a bad time if the mods you did increased breathing enough to be out of range of the oem ecu.
I agree that things may go boom if I lean out the mixture too much. But from the what I found the bp5a ecu may run a little bit richer map than the US ecu. One because it uses the bp5a intake cam (a little bit less lift/duration) than the US exhuast cam and the 4-2-1 oem tubular exhuast manifold over the US cast iron brick. I was hoping the air passing through the engine was similar to what the bp5a was used to and not get too lean.

That being said I may have to go buy a wide band as insurance to keep an eye on everything.
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Old 02-24-2016, 11:49 AM   #7
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Acquire a wideband & find out
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Old 02-24-2016, 11:50 AM   #8
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If you are racing your car, a wideband should have been your very first investment.
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Old 02-24-2016, 11:59 AM   #9
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Short term trims should correct fairly quickly, but like others said it goes to open loop pretty quick. I think disconnecting the battery deletes long term trims, or you can get a scan gauge/code reader to find out. It'll also tell you the health of your engine. Or at least your fuel/o2 sensor health.
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Old 02-24-2016, 12:26 PM   #10
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Old 02-24-2016, 03:25 PM   #11
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you've changed bro......

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