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3000gt SL Twin Turbo ECU and MAF?


drakered6
09-05-2010, 07:43 PM
I am in the middle of doing a swap in a 3000gt SL with an Automatic Tranny. Im swapping the engine out with the vr4 engine, using the same tranny. I have all my parts to do the swap, i just have a question. I have a Greddy E-Manage Ultimate and am wiring that to the stock auto ecu to feed more fuel to the turbos and have the tranny shift. But my question is, with the e-manage do i still have to run a MAF sensor or can i scrap it? Cause i know that the sensor helps caculate the A/F mixter but wont the e-manage interupt that? I have a stock vr4 MAF but was thinking of doing Blow thru pre turbo pipes and i know with those you can either use a GM MAF or no MAF witch im trying to figure out how that works.

toddrs93
09-27-2010, 05:11 PM
I am in the middle of doing a swap in a 3000gt SL with an Automatic Tranny. Im swapping the engine out with the vr4 engine, using the same tranny. I have all my parts to do the swap, i just have a question. I have a Greddy E-Manage Ultimate and am wiring that to the stock auto ecu to feed more fuel to the turbos and have the tranny shift. But my question is, with the e-manage do i still have to run a MAF sensor or can i scrap it? Cause i know that the sensor helps caculate the A/F mixter but wont the e-manage interupt that? I have a stock vr4 MAF but was thinking of doing Blow thru pre turbo pipes and i know with those you can either use a GM MAF or no MAF witch im trying to figure out how that works.
it depends, you can run the emanage both ways. her's some good info I copied.
Tuning Method #1 on non-gutted stock MAF.

Hardware requirement:

EMU unit
EMU main harness
Greddy pressure sensor and harness
compatible Wideband o2 controller
Greddy harness for reading wideband o2 results (0-5V)

With stock 360cc injectors and stock MAF installed, we need to record some EMU datalog runs. What were interested in capturing is Boost (PSI), RPMs, Wideband AFRs, and actual timing numbers. Make a few runs in 1st, 2nd, 3rd gear. Preferrably you want to capture a datalog run without any knock -- and if this is a problem turn down your boost and try again. Also it is worth mentioning you should get a datalog run with injector duty cycle below 100%.

Make note of your current fuel related mods, such as:
Stock fuel pump (yes/no):
Fuel pump wire rewired(hotwired) (yes/no):
Stock Fuel relay low/high voltage bypassed (yes/no):
Stock Fuel Pressure Regulator (yes/no):

If you have an OBD datalogger take note of the low, mid, high fuel trims as they might be useful sometime for future reference.

The more datalog runs you save the better. Even normal cruising ones are good too.

Now you're ready to replace the stock injectors with larger injectors. Go ahead and make the hardware changes.

Setting up the airflow correction map. Switch from TPS tuning to Boost PSI tuning and set up your custom PSI load scale, such as -12.5 PSI, -10 PSI, -7.5 PSI, -5 PSI, etc.

Do not be tempted to use the I/J size before and after, as this confuses people when they run into the 100% input injector duty cycle problem. Yes this makes life easier, but it's also a double edge sword and most people don't understand the consequences so it's better to ignore that feature for now.

Use the formula: (stock injector size) / (new injector size) - 1
For example (360/550) - 1 will give you -34% correction.
One would think that inputing -34% in all the cells in the airflow correction map should be good enough but it is not. Our stock MAF is not linear, so this is one reason why we need to put more work into the airflow correction map.

With -34% populated in every cell and if you did manage to get your car to idle you'll notice it is running very lean. Change the low load cells to -20% and see how that works. Depending on which fuel related mods that have been installed on your car, this -20% will vary greatly. Use the interpolate feature so there's a gradual step from one cell to the next. Now it's time to test your settings, for safety reasons turn down the boost as low as it can go and get all of your tuning done in 1st gear first. If the car starts bucking during WOT then most likely you're too lean at that given RPM and PSI point. Refer back to your original stock 360cc datalog runs to see what AFR you should be running.

Tuning Method #2 Speed density on gutted stock MAF.

Before you reach this step, be sure to complete tuning method #1 first as this will allow you to create a perfect airflow output table for your car. Sharing speed density maps are fine, but note they fluctuate more from one car to another because any modifications that influences V.E. directly influences the HZ numbers in the map. Modifications such as exhaust, downpipe, gutted cats, air filters, intercoolers and many more directly influences speed denisty. This also means every time you a make a minor modification you need to recheck your tune as it may need changing.

Why go speed density? Turbochargers spoolup much faster (makes a 15G car feel like a 9b car spoolup, well at least thats what it feels like to me). The stock MAF is limited to xxxx HZ or xxxx airflow and the greddy pressure sensor can go alot further. Speed density continues to work if intercooler pipes blow apart, and doesn't mind open blow off valves.

Now the hard part, creating an airflow output map for your car. With v2.00 of the emanage software, you can use the data sampling map to assist you. Every cell needs a number, so you need to drive your car under many different RPMS and load conditions. Turning down your boost at different increments will help you find the HZ numbers for each cell. Some cells will be impossible to do as you may never get there ie (20psi at 1000 rpms) and I wouldn't worry too much about those.

Just estimate the HZ number from the neighbouring cells. Take a look at the example airflow output number to get a better understanding of what belongs there.

To run speed density, toggle the airflow adjustment map to airflow output map. If you did your job right, you should notice no change. The airflow output map should now be emulating your factory MAF HZ signals along with your tune integrated. For example, you don't have to make corrections for larger injectors because you already did this in tuning method #1. Confirm everything is working as it should.

Now proceed to gutting your factory MAF. Removing the three honeycomb screens is pretty easy to do, and is reversible should you ever change your mind. Run your car again and make a test drive. You should notice the turbos spool up faster. By removing the honeycomb screens you've made a mod effecting the V.E. so you now have to go back and retune again.

When you want a richer condition you need to increase the HZ, and to make a condition leaner you decrease the HZ.

Note: If you're having trouble getting a steady idle with large injectors because the HZ value doesn't offer enough resolution, you can add more fuel outside of the ECU's control by using the I/J Adj. Map1 and add fuel directly.

Tuning Method #3 Speed Density using GM IAT, fixed baro signal.

The principles described in Tuning Method #2 is exactly the same except the factory MAF is removed completely. With a fixed baro signal you won't have elevation changes affecting your tune as the greddy pressure sensor already compensates for this. The GM IAT is not a 100% match to the mitsubishi IAT so don't be alarmed if your intake temperature numbers are off.

Tuning Method #4 stock MAF + I/J injector sizing correction

Hardware requirements: stage 3 wiring and greddy check engine light adaptor.

This has got to be one of the most interesting tuning features EMU has to offer. Instead of manipulating the airflow signal to the ECU, we manipulate the injectors directly completely bypassing the ECU. What benefits are to this? Stock drivability with stock ignition timing, no hot start issues (if you still have your high fuel pressure solenoid still connected), and the low/high fuel voltage relay will operate at appropriate times. And now the bad, you must keep your input injector duty cycle below 100% at all times. Let's identify the two injector duty cycles that now exist.

Input injector duty cycle - this is the duty cycle out from your ECU and into the input of the EMU.
Output injector duty cycle - this is the duty cycle out from the EMU and drives your fuel injectors.

The EMU allows you to enter injector lag time for more precision. When I tested this feature out it didn't work properly, and there's no harm in just leaving the before and after lag time to zero. I suspect this feature may work if your new injectors are laggier than the stock ones (ie. PTE) but someone else can experiment with this.

This feature alone isn't that useful, as you your limited to the same HP as stock 360cc injectors. Don't think for a minute that just because you've installed larger than stock injectors that you can run higher PSI than before. If this feature excites you then look at the Tuning Method #5 on how to proceed further.

UPDATE....Personal experiences:
Using v2.13 software and the global injector sizing (AKA I/J before and I/J after) alone made my car run idle very lean using (360cc before and 550cc after). I had to richen up the low load end of the map by 20%. I don't know why this was necessary.

Tuning Method #5 I/J injector sizing correction + Boost Cut Limiter + I/J Map

Hardware requirements: stage 3 wiring and greddy check engine light adaptor.

Gray Haze has come up with an interesting tuning method in which I'll describe here. This method improves on Tuning Method #4 and works around the 100% input injector duty cycle problem. This probably is the best tuning technique as you retain stock drivability with no short comings, and no need to monkey with the timing.

To combat the 100% input injector duty cycle, you need to determine at which PSI level this occurs. Once this has been determined, set the boost cut limiter feature before 100% occurs, in essence, you want the airflow signal to the ECU capped at a maximum so the ECU will never reach 100% input injector duty cycle.

Now that the 100% input injector duty cycle problem has been solved, you need to add fuel by using the I/J fuel map. You have a choice of whether to increase fuel based on injector duty cycle or injector duration. The latter is a better choice. Be sure to setup the I/J fuel map based on Boost (PSI).

Update 1: I gave this tuning method a try and was a little frustrated by the fact my v2.13 EMU had trouble subtracting injector duty cycle based on percentages which caused my car to run extremely rich at WOT. In my general tips section I remembered that EMU was known to struggle with injector duty cycle and subtracting injector duration time would be more reliable. I was gonna try the injector duration time method but then realized the amount of work involved. Each cell would have different entry and I don't have any solid datalogs to assist me. I've gone back to my stage 2.5 wiring on my boomslang harness as I'm too lazy to experiment with this tuning method any further.

Update 2: I decided to try this one last time. Speed density at stage 3 works fantastic. Now being addicted to how well stage 3 works with speed density I learned a few things. Boost cut limited feature sometimes overshoots and will cause problems if you're trying to keep input injector duty cycle below 100%. The better way is to hard code the max HZ level into your speed density map, such as 1850 HZ. This guarantees no more overshoots. Next I noticed I was getting an intermittent 20ms dropout or glitch of some kind. My input injector reading would momentarily drop to a very low level which becomes a problem at high rpms (feels similar to a fuel cut). I checked and rechecked my wire harness, moved my emanage to a different location, but couldn't get rid of this glitch. I went as far as buying a second emanage ultimate (rev. E) to see if that would make any difference. Sadly, it didn't. After two weeks I decided I'd much rather give up the excellent part throttle drivability & glitchy WOT (stage 3) for okay part throttle drivability and excellent WOT operation (stage 2.5). Don't let my glitch problem deter you from using stage 3, as Gray Haze has setup four vehicles without problems, I just haven't been able to identify why I'm having a problem on my car. When I look back at Update 1, I'm not sure why I was running rich at WOT, but this time around I was using speed density instead of MAF.

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