abecedarian

Well, injection and timing settings are contained in "maps" which are correlated to throttle position, air flow and engine and air temp and engine RPM. It's a lot easier for the ECU to simply look up something in a table and do minor adjustments based on sensor inputs than it is for the ECU to calculate actual values based on those sensor inputs. This, combined with the way the O2 sensor is used for fuel mixture control- oscillating around lean and rich conditions and the comparably 'lax' emissions requirments for trucks of the time (when compared to passenger vehicles), didn't/doesn't require a particularly fast processor to control engine conditions. The 22RE/RET ECU's main ability to adapt to changing conditions is via the "fuel trim" setting which is an adjustment to injector opening duration to compensate for consistant lean or rich condititions that still fall within the O2 sensor operational range. It cannot learn and optimize ignition timing.

Most modern engine management systems still use maps for baseline settings, i.e. so they can operate from an extended 'power off' situation with minimal learning. Many also maintain maps or "overlays" that allow the ECU to alter operation at each point on the map and learn that setting for future use / optimization. Combined with newer, faster processors and dedicated signal processors, more complicated circuitry, more accurate sensing systems and more advanced knock detection algorithms, they can identify when a particular cylinder misfires or detonates and adjust fuel injection and timing for that particular cylinder to minimize the problem as well as inform the user / tech of the problem, and can even adapt to blended gasoline fuels.

tried4x2signN

So, can you just change the computer to get it to work faster? or is that another issue?

dfarr67

You JUST change the plugs and oil, you don't JUST change the ecm Engine harness and sensor compatabilities- does the dash rum off the computer- transmission shift/lockup....I'm finding out even for a basic installation the learning curve is steep with all these different maps- real easy to hurt an engine and here anyways its tough to find good tuner talent. Also depends on the vehicle model- I think AEM makes some plug in ecms for Subara and Honda cars. I brought up Dynamic EFI because for my 1990 Chevy truck it actually does just plug in- that fact alone may sway you against the work of putting a better ecu in. I was lucky that the vender put together a basic bin so at least I could drive the truck- I think normally things start off pretty basic.

abecedarian

Well, I suppose you could but you're limited by a few things:
-the fuel injectors are wired in the harness to be batch fired. It's possible to separate them into two banks of two injectors and gain some added flexibility but you wouldn't be able to control the injectors individually, i.e. for sequential injection, without rewiring them
-the distributor provides a simple pickup signal, basically emulating points set with 45 degrees dwell with no indication of which cylinder is firing next: that is handled by the rotor. You'd find it difficult to implement sequential injection due to that.

you might check out megasquirt or http://www.diyautotune.com/

shaeff

While I agree with you, if someone wanted to argue, they could say that the ct26 is a "relic from the 80's" as well. Turbo Supra debuted in '87 in the 'States.

dfarr67

Do you really need sequential? I know I would LIKE to have it put sometimes the work is not really worth the effort. For my Chevy, FAST makes a reasonable priced dual sync distributer that can tell the ecm the crank position- still not as acurate as a cam/crank sensor- but a relatively easy bandaid (whats out there for Toyota- probably nothing), I was told there was only 3-4% better economy to be gained over batch, oems mainly went to it for better emisions. For performance apps where there was a big cam I think it is good to control idle, after 3000 rpm there wasn't much difference with bank to bank. All this being said- what is really needed to make a na 22re live on a turbo? Wide Band O2, timing boost retard, water injection, good intercooler...I read that these days the trend is toward higher compression with super/turbo charging, stud the top end, mls/copper gasket- which means you might need to refinish the block. Without being able to tune the oe ecm I can't imagine just putting in a factory generic RET ecm either.

abecedarian

You don't "need" sequential, per se, but sequential injection can allow you to time the injectors to fire just before the intake valve opens thus reducing the amount of puddling or pooling of fuel on the back side of the valve. The benefits are more thorough atomization of fuel, the possibility of more power being available more easily due to that, and lesser tendency to misfire due to abnormal droplets of fuel and cleaner emissions from that. The downside to sequential over the 22re's batch fire is that you would need injectors capable of spraying a full cylinder's requirement in one pulse- batch firing as the 22re does allows smaller injectors to be used since they are fired twice as often and also keeps the injectors cooler since fuel flows through them more often. Batch firing also reduces the ability of the ECU to have fine-grained control over the fuel mixture since multiple cylinders will receive similar amounts of fuel- so one cylinder in a 'bank' or 'batch' running rich can cause the other cylinder(s) in the 'bank' or 'batch' to run lean since the O2 feedback determines the mixture as a whole.

True that at higher RPM's batch firing is nearly as efficient, if not equally so, as sequential but that is mostly due to the minimal amount of time spent with fuel setting behind the valves waiting for them to open.

One should realise though that modern gains in engine performance and economy are due to ECU's capable of responding quickly to rapidly changing sensor inputs, being able to monitor combustion events and adapt to them before the next cylinder fires. You only need to look at the improvements made between the 22RE and the 2RZ to see that- 116HP / 142ft-lb vs 142HP / 160 ft-lb. Arguably, much of that increase in power (into the 3VZE V6 range) is due to the more efficient fuel and ignition control offered by OBDII electronics as is due to changes in engine design.

But anyhow, yes... making an N/A 22RE live with turbocharging to moderate to high boost levels is accurate, precise fuel and ignition control. The stock ECU can compensate the fuel mixture a bit but the fact that the ECU only requires "rich" and "lean" signals from the O2 sensor and oscillates the fuel mix around stoichiometric, as opposed to calculating exactly how "rich" or "lean" the mixture is and adjusting the mixture accordingly before the next injector firing event leaves a lot to be desired for precise mixture control. Likewise, the ECU does not have the necessary resolution to affect timing beyond how the engine RPM, throttle position and air-flow contols affect the ignition map, with the possibility of knock sensing removing all advance if knock is detected.

Imagine being under boost, say .5 Bar, and advance is at say 18 BTDC... then the knock sensor detects knock and timing suddenly drops to 5 BTDC... I bet you'll feel a sudden loss of power there right? So figure that modern ECU's would retard the timing a bit, maybe even enrich the fuel mixture, as the next cylinder fires, until knock subsides, as opposed to dropping it straight to baseline.

dfarr67

I cannot say I know all the terminologies but the story is straight...for example, Edelbrock 'once' offered a TBI to MPFI conversion for GM TBI trucks and cars and they supplied a semi generic chip which really never ran right for me and worse when I strayed with a bigger cam (this was where I learned just how sensitive speed density is). I believe you would call this true batch fire and injection was twice per revolution. I got rid of that system and installed Dynamics plug in ecm which did away with chips but most important changed to bank to bank which was firing once per revolution- what a difference, I am sure sequential would be another great step- but I really didn't want to start hacking into the harness- in fact as the years rolled by on that particular vehicle I found myself slowly moving back to factory hardware, things may look a little different but still a variation on factory- mostly for reliability reasons.
Another comment is regarding superchargers- I talked to LCE about upgrading their Camden supercharger and using a small Eaton unit like the TVS- their responce was that the 22re was not worth the additional r&d, Camden wanted $400 just for the intake that I would mod from there. With all the used Eatons out there- would be nice to have a kit for a reman'd Eaton with their helical rotors and bypass.