ECU questions... (no, not a chip question)
01-19-2004, 11:38 PM
#1
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ECU questions... (no, not a chip question)
Ok, so I want to maximize power on this car (who doesn't?). Firstly I would like to put get about 400-440HP out of the car which I recon is the highest I can go with the car still being "streetable". In other words without weekly oil changes and bi-monthly engine rebuilds. And later... well, sky's the limit.
In any case I don't see how the current Hitachi ECU can stay. Initially I'd like to keep the engine naturally aspirated (turbos or superchargers are a big step money wise). I'd like to make it a very high reving engine by replacing the internals with Titanium 5 and forged components.
Anyways, my question is basically how do I go about putting in a new ECU. And is this needed?
I'm really not sure how much the current ECU can do. Basically how well it automatically adapts, if at all, to physical engine changes.
Hopefully I can start a discussion on this topic and enlighten all of us a big. Especially me.
Cheers.
In any case I don't see how the current Hitachi ECU can stay. Initially I'd like to keep the engine naturally aspirated (turbos or superchargers are a big step money wise). I'd like to make it a very high reving engine by replacing the internals with Titanium 5 and forged components.
Anyways, my question is basically how do I go about putting in a new ECU. And is this needed?
I'm really not sure how much the current ECU can do. Basically how well it automatically adapts, if at all, to physical engine changes.
Hopefully I can start a discussion on this topic and enlighten all of us a big. Especially me.
Cheers.
01-20-2004, 08:14 AM
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Other, "weekend" tuners believe that the Hitachi ECU can handle 400+ hp easy. . .
An OBD-II ECU mainly measures O2 levels and adjusts the injector spray accordingly.
At about 220+ hp that my car makes, my only problem is getting enough fuel through the injectors rapidly enough (I presently run high fuel pressure to accomdate my mods); thus, I need larger injectors.
However, after measuring the A/F ratio for the last couple weeks. The Hitachi ECU does a pretty good job of keeping good A/F ratios in closed loop operation. Only in open loop (WOT) does the A/F ratio become lean--but not dangerously lean as I had expected.
At about 220+ hp that my car makes, my only problem is getting enough fuel through the injectors rapidly enough (I presently run high fuel pressure to accomdate my mods); thus, I need larger injectors.
However, after measuring the A/F ratio for the last couple weeks. The Hitachi ECU does a pretty good job of keeping good A/F ratios in closed loop operation. Only in open loop (WOT) does the A/F ratio become lean--but not dangerously lean as I had expected.
01-20-2004, 09:19 AM
#3
where it kills us is on timing. We run fully 12-14 fewer degrees timing advance...
compared to the 93-early 94 2.8 12V on the 95-98 2.8 12V. If I've done the math correctly using displacement, CR's, cam timing/overlap, A/F ratios and octane at 91RON that I believe timing alone could net 25-30HP additional HP and a similar amount of torque with no other modification whatsoever. Timing advance is a WONDERFUL thing. I'm currently trying to find an old Apexi Super ITC timing controller to piggy-back with my fuel controller. Apexi discontinued it almost 2 years ago ( betcha I know why too!) so I keep searching Ebay as I don't wanna pay $300 for "new/discontinued" merchandise before knowing if it's even compatible with the Hitachi. I'll go out an a $100 limb but the $300 ones scare me.
01-20-2004, 10:14 AM
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How does the ECU calculate the timing?
I would guess the ECU monitors the cam sensor and then calculates timing based upon some algorhythm that depends on other sensors.
What if you modify the cam sensor's position or the "marker" on the cam, so it's 12-14 degrees advanced to fool the ECU as to where the cam is?
I assume that "timing advance is a WONDERFUL thing," because it allows more burn time per stroke and earlier pressure build-up in the combusion chamber to force the piston down?
P.S. "Betcha I know why too!" So tell us why you believe Apexi discontinued the ITC timing controller!
What if you modify the cam sensor's position or the "marker" on the cam, so it's 12-14 degrees advanced to fool the ECU as to where the cam is?
I assume that "timing advance is a WONDERFUL thing," because it allows more burn time per stroke and earlier pressure build-up in the combusion chamber to force the piston down?
P.S. "Betcha I know why too!" So tell us why you believe Apexi discontinued the ITC timing controller!
01-20-2004, 10:29 AM
#7
I believe the OBDII Hitachi to have a pre-set timing advance limit in addition to
the knock sensors. The reason I believe this to be so is I cant get more than 24 degrees total from the VAG with 95, 97, 100, 103 and 105 octane fuel even in cool (sub-60F) weather. Yet on the 94 90Q I tested it could easily pull 34-36 degrees with 91 octane fuel on a 85 degree day. Thats a HUGE HUGE difference in timing tables!!
Your assumption is correct on "why", ie: the actual spark and subsequent combustion occurs before the piston is at TDC.
As for why Apexi would've stopped making them: Adjustable timing advance is a dangerous thing. Since Apexi is a mostly ricer-driven tuner consider the mentality, mechanical expertise and temptation. Mucho exaggerated if you're just a hairs breadth behind someone at the end of the quarter mile. Give a monkey a shiney red wall-mounted button that injects him with nicotine, cocaine, heroin or adrenalin and see what he does with it.
Your assumption is correct on "why", ie: the actual spark and subsequent combustion occurs before the piston is at TDC.
As for why Apexi would've stopped making them: Adjustable timing advance is a dangerous thing. Since Apexi is a mostly ricer-driven tuner consider the mentality, mechanical expertise and temptation. Mucho exaggerated if you're just a hairs breadth behind someone at the end of the quarter mile. Give a monkey a shiney red wall-mounted button that injects him with nicotine, cocaine, heroin or adrenalin and see what he does with it.
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01-20-2004, 11:14 AM
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Thus, regarding the Apexi, the ECU would not retard the timing . . .
when the "monkey" pushed the shiny red button too many times? It seems that any ECU's programming should not rely just on one set of sensors to calculate timing--at some point the other sensors should trigger the ECU to shut down the engine when sensor readings exceed program specifications.
Still, would altering the cam and/or crank position sensors to read 10 degrees off not remedy the timing tables' limitations a little?
If the ECU has a particular equation that it uses, changing the variables supplied by the sensors by 10% could theoretically advance the timing without significant detriment?
Still, would altering the cam and/or crank position sensors to read 10 degrees off not remedy the timing tables' limitations a little?
If the ECU has a particular equation that it uses, changing the variables supplied by the sensors by 10% could theoretically advance the timing without significant detriment?