As the title says, I'd like to open up a discussion on engine tuning with a piggyback or standalone ECU. Feel free to post up any questions you have and I'll do my best to answer them here. We're gearing up for a video series covering various tuning topics, so any questions that are asked here may end up as the basis for a video segment.
Ask your tuning questions here; open discussion thread on engine tuning.
- Thread starter Zach
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Ok so I just put 264 cams in my 7M running on a MAFT Pro speed density. I had to pull quite a bit of fuel at idle-2k to get the wb back to stoich at idle and cruising, is that normal? I guess what I should be asking is I've never had the ability to tune a car when upgrading cams before, what should I expect to have to do to fuel, timing, etc? Should i be bringing the WB back to stoich when tuning outside of WOT? Quick setup is 560cc's, forged bottom, ported head, upgraded springs, turbonetics bolt on 63 trim, fmic w/pipes, 3" catback.
There's very rarely a free lunch when it comes to increasing power output. Going with more aggressive cams will typically improve breathing at high RPM, but usually at the expense of efficiency down low. Your car simply isn't moving the same amount of air at low load/RPM as it did with stock cams, so you had to trim the fuel map to match. You should also expect to have to add fuel up top since the efficiency increased in that range.
With speed density calculation your fuel delivery is calculated by a table that represents how efficient your engine is at different points as you change RPM and inlet pressure (pressure in the intake manifold). Changing a part like a camshaft directly changes the efficiency, so you have to retune. With a system that uses a direct measurement for airflow (like the stock MAF), fuel calculations are based primarily from a direct measurement of the volume of air entering the engine, so the efficiency increase due to cams would be accounted for automatically.
Stoich is fine for part throttle cruising and idle, and if the stock ECU is still seeing the O2 sensor then it'll try to keep it there. Depending upon how aggressive your cams are in terms of overlap, you may find that a slightly richer mixture runs more smoothly. Lots of overlap will lead to an increase in unburnt fuel being pumped through the engine when both the intake and exhaust valves are open, and indicating a leaner mixture on the wideband than what the cylinders are actually seeing. 264s aren't too aggressive, but it's something to experiment with to see if it runs better.
Adjusting timing is something that should be done on a dyno (or using the Virtual Dyno feature of our DET3 or EMU, shameless plug). That's something that really needs to be tuned for effect, and with pump gas you don't want to get too greedy since fuels aren't terribly consistent and the stock ECU doesn't have great knock control.
With speed density calculation your fuel delivery is calculated by a table that represents how efficient your engine is at different points as you change RPM and inlet pressure (pressure in the intake manifold). Changing a part like a camshaft directly changes the efficiency, so you have to retune. With a system that uses a direct measurement for airflow (like the stock MAF), fuel calculations are based primarily from a direct measurement of the volume of air entering the engine, so the efficiency increase due to cams would be accounted for automatically.
Stoich is fine for part throttle cruising and idle, and if the stock ECU is still seeing the O2 sensor then it'll try to keep it there. Depending upon how aggressive your cams are in terms of overlap, you may find that a slightly richer mixture runs more smoothly. Lots of overlap will lead to an increase in unburnt fuel being pumped through the engine when both the intake and exhaust valves are open, and indicating a leaner mixture on the wideband than what the cylinders are actually seeing. 264s aren't too aggressive, but it's something to experiment with to see if it runs better.
Adjusting timing is something that should be done on a dyno (or using the Virtual Dyno feature of our DET3 or EMU, shameless plug). That's something that really needs to be tuned for effect, and with pump gas you don't want to get too greedy since fuels aren't terribly consistent and the stock ECU doesn't have great knock control.
Processing power has virtually nothing to do with it, an engine at 9000 rpm may as well be standing still compared to any modern processor. Fast processor speeds make for good marketing bullet points, but it has no direct correlation to performance.
Here are the biggest factors in terms of idle quality:
Cam profile- the more aggressive it is, the more difficult it will be to get a stable idle. Like I mentioned before, lots of overlap causes unsteady combustion at idle (meaning under the exact same measurable conditions, combustion is different from one cycle to the next).
Injector flow rates- If you have large cylinder to cylinder variations in flow rate at small pulsewidths (not static flow rate), then you'll have a very difficult time locking down a stable idle.
Injector nonlinearities- Some larger injectors have nonlinear behavior at small pulsewidths (usually under 2 milliseconds), meaning that there's not a predictable link to how long the ECU gives it a signal to open and how much fuel is delivered. We plan to add a table to our software so that you can define this curve at small pulsewidths, but there are several cars running ID2000s with our EMU on gas with small cylinder sizes and have no issues with idle quality. Some other injectors have far worse behavior at small pulsewidths, but you don't see too many of them these days.
Sequential vs. semi-sequential fueling- If you're running a stock 7M or 1JZ (JZA70) ECU then you have three injector channels with 2 injectors on each channel. This won't pose a problem with idle quality until you start running larger injectors. Switching to sequential fueling allows you full control over the injection event, meaning you can adjust the timing of the injection event relative to intake valve opening event. Open versus closed valve injection is a topic for another time, as that's a bit of a lengthy explanation.
Here are the biggest factors in terms of idle quality:
Cam profile- the more aggressive it is, the more difficult it will be to get a stable idle. Like I mentioned before, lots of overlap causes unsteady combustion at idle (meaning under the exact same measurable conditions, combustion is different from one cycle to the next).
Injector flow rates- If you have large cylinder to cylinder variations in flow rate at small pulsewidths (not static flow rate), then you'll have a very difficult time locking down a stable idle.
Injector nonlinearities- Some larger injectors have nonlinear behavior at small pulsewidths (usually under 2 milliseconds), meaning that there's not a predictable link to how long the ECU gives it a signal to open and how much fuel is delivered. We plan to add a table to our software so that you can define this curve at small pulsewidths, but there are several cars running ID2000s with our EMU on gas with small cylinder sizes and have no issues with idle quality. Some other injectors have far worse behavior at small pulsewidths, but you don't see too many of them these days.
Sequential vs. semi-sequential fueling- If you're running a stock 7M or 1JZ (JZA70) ECU then you have three injector channels with 2 injectors on each channel. This won't pose a problem with idle quality until you start running larger injectors. Switching to sequential fueling allows you full control over the injection event, meaning you can adjust the timing of the injection event relative to intake valve opening event. Open versus closed valve injection is a topic for another time, as that's a bit of a lengthy explanation.
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You'll need to use one of the latest versions of the firmware for use with the stock multiplex ignitor. Send me an email at support@ecumasterusa.com and I'll provide you with a base map.
Thanks!
Thanks!
Send me an email with your current map and a log of you trying to start it. Also, include what firmware version you're using. There's a video on our youtube channel that shows you how to save a log. Email the info to support@ecumasterusa.com
I use the apexi safc2. I have low throttle at 30, high at 70. I have the lexus afm, 550's, and afpr. Also a very large intake manifold and throttlebody. For some reason the safc has to be set at 25% to be at 14 on wideband. But the ecu and SAFC are fighting eachother. The wideband sweeps back and forth and back and forth. Im rich one minute and lean as hell the next.
Hi there,
The car I’m working on is a 1988 Toyota Supra Turbo (7MGTE).
Preparing to install the unit and was checking configurations. I do have a couple of questions that I’m hoping that you can answer.
I have the classic with a plug and play harness adapter.
Thanks!
The car I’m working on is a 1988 Toyota Supra Turbo (7MGTE).
Preparing to install the unit and was checking configurations. I do have a couple of questions that I’m hoping that you can answer.
I have the classic with a plug and play harness adapter.
- FPR signal seems to be mapped to pin 5 Grey (AUX 3), but physically the wire goes to pin 6 Grey (Injector #4.) I’ve re-pinned to 5 Grey, is this correct?
- Both my RC 550cc injectors as well as the stock 440cc injectors are low impedance. Based on the EMU manual, it is necessary to install a 4.7 ohm 50W resistor inline to limit the current. Is this correct, or is there another current limiting circuit somewhere between the ECU and injectors that would remediate the issue?
- Do any of the standard connections (PnP harness wired pins) require the flyback diode? It doesn’t look like it, but just wanted to verify that I hadn’t missed something.
- IAT signal in the PnP harness (21 Blk) goes to THA (Air Temp Sensor.) When I install the GM IAT sensor, I should sever that connection and take one lead to 21 Blk and the other to Gnd, correct?
Thanks!
1. That was the issue I had as well and I moved it to gray 5. You can change the settings under the software to any open pin available under your settings.
2. No, as long as the new injectors are low independence you keep it wired up like it is. I am running sequential injection so I got a Acura Legend fuel injector resistor box so I can have 6 separate injector channels.
3. Not that I seen. I am not running any.
4. Correct. Polarity does not matter either on the GM air intake temperature sensor.
2. No, as long as the new injectors are low independence you keep it wired up like it is. I am running sequential injection so I got a Acura Legend fuel injector resistor box so I can have 6 separate injector channels.
3. Not that I seen. I am not running any.
4. Correct. Polarity does not matter either on the GM air intake temperature sensor.