ECU quetions

nsxincali · 8 January 2005

I was wondering if there are any ways to reprogram a 95 3.0 ecu. I noticed comptech sells one for the 91-94. Any other options besides a stand alone system? I would like to reprogram the ecu for headers, intake, exhaust and raising rpm to 8200. Also are the Apexi v-tech controllers safe to use if tuned right? Any suggestions.

D'Ecosse · 8 January 2005

nsxincali said:
I was wondering if there are any ways to reprogram a 95 3.0 ecu. ....

No, unfortunately not.

The Kid · 8 January 2005

yea, what about v-tec controllers???...

xxx · 8 January 2005

nsxincali said:
I was wondering if there are any ways to reprogram a 95 3.0 ecu. I noticed comptech sells one for the 91-94. Any other options besides a stand alone system? I would like to reprogram the ecu for headers, intake, exhaust and raising rpm to 8200. Also are the Apexi v-tech controllers safe to use if tuned right? Any suggestions.

VTEC!

nsxincali · 15 January 2005

xxx said:
VTEC!

What does that mean? And does anyone recommend the VTEC controller?

jgtcnsx · 16 January 2005

im sure apexi has a piggy back system you could use

AndyH · 16 January 2005

nsxincali said:
What does that mean? And does anyone recommend the VTEC controller?

That meant you spell VTECH instead of VTEC

nsxincali · 16 January 2005

AndyH said:
That meant you spell VTECH instead of VTEC

That is very very helpful. Thank you very much XXX!!! :tongue:

kpond · 16 January 2005

nsxincali,

Good question, but with the mods you mentioned, you're still well within the parameters of what the stock ECU can address. In other words, your ECU has already adjusted itself and you will not see any improvements with another add-on. (The exception, of course, is the slightly higher rpm limit that your current ECU will not allow.)

For an ultra-summarized summary of your ECU (and virtually all other ECUs), I offer the following.

After you are full operating temperature and at engine loads < ~75% (which translates to about 80%+ of your typical driving styles), your ECU is in closed-loop mode. It is controling injector pulse duration and then reading the A/F ratio from the O2 sensor. It keeps the A/F balanced - actually bouncing back and forth on either side of 14.7:1. In your case, let's say that you added all the mods at once - exhaust, headers, intake, etc. As soon as you drove the car, it would "discover" that the pulse durations that it was previously using may now be too short. These mods would typically cause a lean condition and your ECU will find that it has to add additional pulse width to keep balancing around 14.7:1 as indicated by the O2 sensors. The ECU also contains short and long term fuel trim data and it will adjust the trims so that even its initial guesses are correct.

The important point here is that if, at any time, your ECU cannot achieve the desired 14.7:1, it will trigger a check engine light and go into limp mode.

Now, in ~75-100% load conditions (you might loosley translate this to throttle position), the engineers want a slightly richer and safer A/F ratio for the engine. Since O2 sensors can only report if you're above or below 14.7:1, the ECU reverts to open-loop mode. It no longer uses a feedback loop with the O2 sensors, choosing instead to in internal table pre-programmed into the ECU. Now, you might be concerned that your mods are not accounted for in this pre-programmed, non-dynamic table. However, worry not, as the ECU will utilize the aforementioned fuel trim data to modify the closed loop tables.

And I said this was the brief answer....

Hope it helps.

nsxincali · 20 January 2005

kpond,

Thanks for your help. Also, if I added straight pipes and a 70 shot kit, would my ecu still be efficient enough? And do you have any imput on a Apexi VTEC controllers? A performance shop in Sac highly recommends one. Thanks again.

kpond · 21 January 2005

There are numerous owners here on the forum running Nitrous set-ups and allegedly with good reliability. Done right, the nitrous systems simultaneously inject fuel to compensate for a potential lean condition.

Regarding the Apexi VTEC controller, I don't see how it would be advantageous but I am sure you will get plenty of other opinions.

flight · 21 January 2005

kpond said:
The important point here is that if, at any time, your ECU cannot achieve the desired 14.7:1, it will trigger a check engine light and go into limp mode.

What do you mean by "limp" mode? Do you mean that the ECU reduces the fuel fed to the engine? Wouldn't a safer option be to run the injectors at a higher than normal rate? Just curious because my 02's are damaged and will be replaced soon, but I cannot feel any difference in the car's power or fuel efficiency.

NSX PTY · 21 January 2005

wow kpond, seems you're very knowledgable on ECU matter

can you or anyone give me an idea of possible cause on a situation I had, I think its something with the ECU.

i was cruising at 120mph, 6,000rpm, suddently throttle is not responding, first thoughts: something is wrong with clutch or transsmision. But, when rpm went below 4,000 exactly, throttle respond again, I mean between idle and 4,000rpm everything is ok, above 4,000rpm looks like there is no gas (which was not the case).

Stop the engine, wait 1 minute, start again, everything is back to normal. Took it to Honda dealer (no Acura down here), can't find the cause, ECU did register any code for that. Usually i have the check engine lite up cause i don't have catalytic conv.

Any idea?? thanks anyone in advance !! :smile:

AutoVation · 21 January 2005

I believe Technosquare can provide you with a custom programmed ECU for the NSX. When you call, ask for Danny.

02#154 · 21 January 2005

"Limp mode" is another section of the ECU's programmed tables with parameters set to protect the engine. Typical measures include pulling timing, running rich and even possibly limiting RPM, though I haven't heard of that one before. The O2 sensor feedback loop is probably ignored. Mileage goes way down but the ECU limits damage to the engine.

Like kpond said, nearly every ECU uses the same principals with the details of how it is achieved being the only differences.

J

Joseph · 21 January 2005

NSX PTY said:
can you or anyone give me an idea of possible cause on a situation I had, I think its something with the ECU.

i was cruising at 120mph, 6,000rpm, suddently throttle is not responding, first thoughts: something is wrong with clutch or transsmision. But, when rpm went below 4,000 exactly, throttle respond again, I mean between idle and 4,000rpm everything is ok, above 4,000rpm looks like there is no gas (which was not the case).

Any idea?? thanks anyone in advance !! :smile:

your ecu might have a speed limiter

vtecNSX1 · 21 January 2005

I dont know of any way to program other than buying a standalone ecu or piggyback but science of speed sells a reprogrammed ecu that works really well.

kpond · 22 January 2005

02#184 provided an accurate description of limp mode. The NSX limp mode will limit RPMs as well.

NSX PTY: First, tsk, tsk for "cruising" at 120mph. I hope it was an isolated/remote area! Based on your description, my guess would be that somehow your traction control either malfunctioned - or potentially functioned "correctly". High-speed straight line NSX runs will often work best with the traction control turned off. The reason is that at high speeds, even the slightest tire bounce may cause what the traction control computer perceives as a slipping condition. The description of what happens when the traction control steps-in are almost exactly what you describe.

SexyRed · 22 January 2005

4000 rpm

nsx pty,

From what I know the fuel pump might switch to higher voltage. I recalled the pump voltage kicks around 4000 rpm. The resistor is located on the right side in the engine bay; near the fuel filter. It is the silver box size of cigarette box.

You can try disconnecting it and jump the wires.

That will switch the fuel voltage to 18 volts I believe.
Just my thought.
Danny Lai

NSX PTY · 22 January 2005

Thanks everyone,

kpond,
first, thanks for the concern about "cruising at 120mph", usually don't speed this high, just occasional fun. i agree, traction control sensor in one of the corners was recently replaced, and still tcs jumped-in when there's no slipping, maybe another sensor is malfuctioning. Or, as you said it is functioning correctly because streets down here are not as smooth as in the US. Strange is that fuel cut-off was permanent at 4000rpm even at low speeds, before i restarted the engine.

SexyRed,
i will comment this to my dealer in PTY (Panama). you might also be right because the fuel cut-off at exact "4,000 rpm" is key to the problem. nothing related to speed.

does anyone can relate this symptom to VTEC engaging at 5,000 - 5,500rpm (don't recall exact rpm). my thoughts are that something (maybe mechanical) is wrong with VTEC and to prevent major damage, ECU just limit rpm to say 1,000 rpm before VTEC engage? makes sense??

last, my NSX is 91, and the computer didn't record any code, do newer models record all codes from check-engine light, i know newer model carry a different "computer" (there is a name for this, don't remember). if it happens again, i'll have to brigde the blue plug below the glove compartment and get the code for the problem.

thanks everyone again.

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