I have also noticed my mpgs come up slightly with the Supra injectors. From the low 12s up to 13 now but I also haven't gotten my tune even close to right. It's running rich as hell but definitely even cruising in vacuum feels like it runs stronger and I'm not hitting boost as hard as I was before.
[MENTION=115347]gamefreakgc[/MENTION] I've got a few questions for you about the Supra injectors. Prior to install untill I got boost my short and long term fuel trims were always below 10% in either direction. I'm now seeing them run all over the place for -21 to like +15. I'm mostly attributing this to my tune not being right yet and the stock ecu doesn't quite know what to do. The problem I am having is using the MAF adjust and o2 adjust features in my piggyback I'm not really able to tune open loop at all because it's not consistent when it transitions from closed to open.
Most times it seems to happen in 3rd gear but I'll be sitting right at 12.2 afr and then open loop happens and my gauge pegs on 10 but it doesn't seem to get better no matter how much I adjust the MAF voltage and going too far with the maf results in closed loop running lean.
Biggest issue I am having is after the truck has sat for an hour or two it won't fire back up easily at all. It takes 2 or 3 good 10 second bursts with the starter and it stumbles to life. I think the injectors are flooding it out as soon as I turn the key because after a few cranks I can smell raw fuel. I've adjusted my MAF voltage down .45 volts below 500 rpm but it didn't seem to help much. Kinda like open loop is unresponsive to my adjustments. Any ideas what I should try to remedy that?
I can share my experience but no guarantee it will fix your issues. It sounds like you have 3 main challenges, closed to open loop transition, open loop and startup.
1. Closed to open loop transition is a bit of a moving target. On my auto, it happens at around 60-70% throttle and around 7 PSI of the max 10 PSI that I see, so pretty heavy throttle. There's no good way to tell when it changes from open to closed loop except for the AFR's. I've learned to not drive in that transition area very much since mine will go rich as well as I have open loop enrichment via the O2 overlapping with fuel injector increase so it also tends to run rich. However, I will also say it takes the ECU a while to "learn" the new O2 skew voltages. It will start out super rich and then eventually start to pull fuel out to where you actually want it. Normally though you'd want to tune open loop first and then work backwards for closed loop. I actually am pulling fuel at all values except for 9 PSI+ over 4000 RPM's since I have a extra water/meth injector sending fuel. I'm guessing that at elevation with no extra fuel systems, you might see the same.
2. Open loop should actually be easy to tune. You want to view your tune as if you had two: closed loop is controlled primarily by the O2 sensor (use the MAF tune only to help dial in your STFT's close to 0) and open loop is exclusively controlled by your MAF tune since the ECU totally ignores O2 sensor voltages at open loop. For me I don't use the MAF since driving the injector pulse width is simpler but I realize you don't have that option. Try to limit your MAF voltage skewing to open loop as much as possible, the less tuning you have in closed loop the better. A great tip is use as little tables as possible. The more you add the more complicated it gets and also increases the risk of one value counteracting the other.
3. For the startups, take out any MAF skew under vacuum. That's across all RPM ranges and all vacuum values, except for maybe 1 PSI below boost (for me that's around 13.6 PSIA, you might be closer to 12 with elevation). For the ranges of 0-1500 RPM's make sure you have no MAF voltage change, O2 sensor change, nothing that would affect startup. The Supra injectors do run a bit rich at first but not enough to keep it from starting. They only flow around 25% more than stock injectors and are completely within the range of the ECU's ability to adjust. After a dozen or so cold startups the ECU will take out that extra fuel so you'll be more in the 11-12 AFR range on a cold start.
There's also an issue some have reported about a bad signal on the crank & camshaft sensor when using a piggyback. I had this on my previous engine whenever I had to reset the fuel trims or changed the tune and it would go away after a few weeks. It's never done it on the new engine (same wiring), so I can't say definitively what the cause was, other than it can go away on its own.
Im in the same boat just trying to avoid open loop. Mine seems to go into it easier then your buy the sound of it or I just have a heavy foot haha. Pretty much it will ran clear through second gear fine but once it shifts to 3rd and gets load on it it pops open loop and the afr plumits and it doesn't want to come into closed loop. Kinda like how with cruise control it wont go back into 4th for a long time once it downshifts.
I am finding the same that over the entire load and rpm band I am needing to pull at minimum 5% fuel in order to keep the fuel trims in line but I have gotten those pretty spot on where they need to be.
Thankfully my piggyback isnt tied into the cam and crank sensors, it controls timing directly through the igniter channels which is how I am able to advance the timing.
Right after I made that last post I took some logs of the truck cranking and not starting. I skewed the maf value down about 40% so when it starts cranking its basically telling the injectors to not fire at all. It seems to be helping the more times I start it but if it doesn't work tomorrow morning my next step will be zeroing out the lower maf value and trying to let the stock ecu figure its shit out.
I can share my experience but no guarantee it will fix your issues. It sounds like you have 3 main challenges, closed to open loop transition, open loop and startup.
1. Closed to open loop transition is a bit of a moving target. On my auto, it happens at around 60-70% throttle and around 7 PSI of the max 10 PSI that I see, so pretty heavy throttle. There's no good way to tell when it changes from open to closed loop except for the AFR's. I've learned to not drive in that transition area very much since mine will go rich as well as I have open loop enrichment via the O2 overlapping with fuel injector increase so it also tends to run rich. However, I will also say it takes the ECU a while to "learn" the new O2 skew voltages. It will start out super rich and then eventually start to pull fuel out to where you actually want it. Normally though you'd want to tune open loop first and then work backwards for closed loop. I actually am pulling fuel at all values except for 9 PSI+ over 4000 RPM's since I have a extra water/meth injector sending fuel. I'm guessing that at elevation with no extra fuel systems, you might see the same.
2. Open loop should actually be easy to tune. You want to view your tune as if you had two: closed loop is controlled primarily by the O2 sensor (use the MAF tune only to help dial in your STFT's close to 0) and open loop is exclusively controlled by your MAF tune since the ECU totally ignores O2 sensor voltages at open loop. For me I don't use the MAF since driving the injector pulse width is simpler but I realize you don't have that option. Try to limit your MAF voltage skewing to open loop as much as possible, the less tuning you have in closed loop the better. A great tip is use as little tables as possible. The more you add the more complicated it gets and also increases the risk of one value counteracting the other.
3. For the startups, take out any MAF skew under vacuum. That's across all RPM ranges and all vacuum values, except for maybe 1 PSI below boost (for me that's around 13.6 PSIA, you might be closer to 12 with elevation). For the ranges of 0-1500 RPM's make sure you have no MAF voltage change, O2 sensor change, nothing that would affect startup. The Supra injectors do run a bit rich at first but not enough to keep it from starting. They only flow around 25% more than stock injectors and are completely within the range of the ECU's ability to adjust. After a dozen or so cold startups the ECU will take out that extra fuel so you'll be more in the 11-12 AFR range on a cold start.
There's also an issue some have reported about a bad signal on the crank & camshaft sensor when using a piggyback. I had this on my previous engine whenever I had to reset the fuel trims or changed the tune and it would go away after a few weeks. It's never done it on the new engine (same wiring), so I can't say definitively what the cause was, other than it can go away on its own.
Im in the same boat just trying to avoid open loop. Mine seems to go into it easier then your buy the sound of it or I just have a heavy foot haha. Pretty much it will ran clear through second gear fine but once it shifts to 3rd and gets load on it it pops open loop and the afr plumits and it doesn't want to come into closed loop. Kinda like how with cruise control it wont go back into 4th for a long time once it downshifts.
I am finding the same that over the entire load and rpm band I am needing to pull at minimum 5% fuel in order to keep the fuel trims in line but I have gotten those pretty spot on where they need to be.
Thankfully my piggyback isnt tied into the cam and crank sensors, it controls timing directly through the igniter channels which is how I am able to advance the timing.
Right after I made that last post I took some logs of the truck cranking and not starting. I skewed the maf value down about 40% so when it starts cranking its basically telling the injectors to not fire at all. It seems to be helping the more times I start it but if it doesn't work tomorrow morning my next step will be zeroing out the lower maf value and trying to let the stock ecu figure its shit out.
And I'm just sitting here like, email me better tunes please :thanks:
Is the extra 50hp and HP/TQ curve flattening worth it?
That's a very subjective question! No one can answer that for you, only you can. What are your goals for your rig? If it's just a weekend toy/offroading rig, probably not. There's no practical use for the supercharger except for towing if you have issues pulling heavy loads. If it's your daily driver then perhaps it is worth it. I enjoy it, but I've got like an extra 130 HP/TQ lol.
Is the extra 50hp and HP/TQ curve flattening worth it?
I stumbled upon a 99 w 200k miles auto 2wd with a 2nd gen sc. What would you guys pay for it? I believe i can get it for around 2.5k. Good deal or no?