give me feedback on your opinions. boost, power, a/f
- Thread starter SuperSonic
- Start date
Maybe i didnt clarify in my first post. I dide a base line. I didnt pay bisi to dyno run and tune it. So when ppls tell me if he could of done something he would have, let me say again i didnt pay him to do so. Thats why i was asking about adjusting the fpr. Since im under rhe impression test pipes more so affect back pressure and slightly lean it out, along with this old s/c being set up for the equipment at the time. Ie it shouldnt need a stand alone or fuel system. All this leads me to simply ask will adjusting the fpr richen across the board.
Im still trying to understand the full boost at 6 psi droped to 12.5 but at 5 psi is at 13.5 a/f but that at 5k rpm. The unit should be at full boost at 4k i thought thus my a/f should be 12.5 at 6 psi at 4k rpm. I was under assumption the whipple didnt need special tunning stuff so i want to know if i can just adjust the fpr. AGAIN i didnt pay for a tune, just a base line. I dont think bisi would even mess with fpr for a base line run.
Sry if the post confused anyone.
Im still trying to understand the full boost at 6 psi droped to 12.5 but at 5 psi is at 13.5 a/f but that at 5k rpm. The unit should be at full boost at 4k i thought thus my a/f should be 12.5 at 6 psi at 4k rpm. I was under assumption the whipple didnt need special tunning stuff so i want to know if i can just adjust the fpr. AGAIN i didnt pay for a tune, just a base line. I dont think bisi would even mess with fpr for a base line run.
Sry if the post confused anyone.
Sorry Guys, this is going to be a long post to explain all the moving parts.
Please understand I am trying to help here not picking apart any other persons work or advice. I am also making the assumption that the data gathered at you dyno session is accurate. For me running a stock bottom end boosted NSX CTSC or Turbo, without any addtional charge cooling on pump gas at AFR's higher than 12.0:1 is in my opinion not safe. Not knowing what the fuel trims are on this car and going into boost is not safe. Not knowing the fuel trims is why you should not adjust the FPR.
A little background about Fuel Trims, the CTSC and its fuel system:
How the ECU decides how much fuel to inject at any given load range and any given RPM is done by looking at the factory written Base Fuel Table. This table would have been made over all kinds of testing and under all kinds of conditions but the mechanical parts of the engine would have been in perfect working order. After hours of testing to find the safe limits, best fuel economy, and best drivability for the vehicle the engine will be used in the perfect fuel table will be made. The real world is never perfect, there are so many variables within manufacturing, with aging components, with fuel, environmental conditions, and many more that this perfect fuel table can only account for a perfect environment. If anything changes then the fuel table is no longer correct for the conditions so the fuel system has to be flexible to deal with any changes. These changes from perfect are reflected in the Long and Short term fuel trims calculated and stored by the ECU.
How exactly the fuel trims work on an OBDII NSX is not known 100% as of yet but this is basically how they work. After your car is warmed up and everything is considered normal by the ECU the ECU will start to monitor the cars O2 sensors, the bad thing about our cars compared to some newer cars is our cars have narrow band O2 sensors. Meaning the ECU only knows if the car is richer or leaner than 14.7:1 AFR, the ECU does not know how much richer or leaner it just knows the condition is either rich or lean. The ECU makes short term adjustments to the amount of fuel at a given RPM and given load range that the engine is running at. It will continue to make short term adjustments until the O2 sensors toggle very quickly between rich and lean. once this starts to happen the ECU knows the AFR is at 14.7:1. If the ECU had to add 10% more fuel to the factory base table for fuel then the ECU thinks the car is running 10% lean. If the car runs in this state long enough the ECU "learns" this condition and applies it to the long term fuel trims. Once the long term fuel trims have been adjusted they are applied to the entire operating range of the cars fuel table. What is unclear at least on the NSX is what happens when the car goes into WOT and the ECU stops looking at the O2 sensors for feedback, does the ECU keep adjusting the base fuel table based on the last known long term fuel trims? Most manufacturer's use the long term fuel trims in this open loop mode but recently SOS did some testing with a car setup with an FIC and Chris felt that based on his test the long term trims were being ignored in open loop WOT conditions. I have not tested this my self but most manufacturers do use these long term fuel trims in the open loop WOT conditions thinking that if the car was either rich or lean when the ECU was looking at the O2 sensors that it will still be either rich or lean when it is not looking at the sensors.
How will the fuel trims effect your car? Your car can no longer use the Base fuel table to get the accurate amount of fuel because you have added the CTSC the car is getting more air pushed into it than it could have normally sucked in. So CT had to trick the ECU into doing what it wants to get the right amount of fuel injected for the increase in air added by the CTSC. This works in most cases but is not ideal, the best case would be to take your engine with its new power added re-do all the testing and rewrite the Base Fuel table, not practical. So you do the next best thing and strap your car to a dyno and adjust what you can to make things as close to perfect as possible. The only thing that CT could really play with is fuel pressure, injector size, and the time to start tricking the ECU. Fuel pressure is changed by adding the adjustable FPR and a Boost-A-Pump, the time to start tricking the ECU is done by the ASM/ESM (voltage clamp) wired to the ECU's MAP sensor. The factory FPR is a 1:1 ratio, this means the amount of fuel added as the load of the engine increases at a constant predictable rate, the change to the OEM FPR is done by referencing the manifold air pressure (MAP). The problem is that now that you have more air being shoved into the engine than can normally be sucked in is the engine becomes more efficient and will need more fuel to keep up with increased air, so CT added an adjustable FPR to adjust the fuel pressure at a ratio higher than 1:1. This means that rate the fuel pressure is increased is faster. So as the load increases the amount of fuel pressure increases and it does so at a rate faster than the OEM unit did so you are adding more fuel pressure and as a result more fuel. This works great for the increased air added to the engine but you are still limited by what the fuel pump can supply. CT added a Boost-a-Pump to the fuel system that is active when the system is in boost and the fuel demands are the highest. The Boost-A-Pump will run the fuel pump at a higher voltage than the 13.8VDC that the battery is supplying. This increased voltage increases the speed of the pump, as a result the amount of fuel and pressure that can be delivered to the injector is increased. Get it all right and the new ratio of the CT FPR takes care of the additional fuel needs just prior to boost and the Boost-a-pump takes car of the additional fuel needed in boost. This system is really simple with not much to adjust, it works but after doing all the testing to design a system like this at the end of the day you really have very little control over the fuel system, but it works.
With any closed loop fuel system if you raise the fuel pressure at idle higher than normal the amount of fuel being injected at idle will increase as well and the ECU will see this by monitoring the O2 sensors. The ECU will start removing fuel and adjusting the long term fuel trims, once the trims have been changed the ECU will apply that trim to the rest of the fuel map and you will have the opposite effect of what you wanted to happen. You might think that if I lowered the fuel pressure than the ECU would add fuel and adjust the fuel trims to add more fuel to the rest of your fuel map and you are correct it would, but you also just lowered your base fuel pressure and the overall amount of fuel you have to deliver will also be reduced, and when the system goes into open loop or WOT there will not be enough fuel volume or pressure to add enough fuel under boost.
The best way to fix this issue after you know the health of your fuel system as a whole is to get complete control over the fuel system with either a stand-alone ECU or a piggyback ECU, and with the added benefit of timing control most of these units provide you will have all the tools needed to safely boost your car under any condition. Talk to your tuner, ask about the AEM FIC, it may fit your need perfectly and the cost to install and tune one really is not that bad. There is talk of a new stand-alone coming from AEM that will work on the OBDII cars, but that is just talk. Mike over at Autowave has a solution for OBDII cars to run both the OEM ECU and AEM stand-alone at the same time so that may be another option for you.
I can only share what I have learned from playing with my three NSX's. The OBDI cars are better suited to the CT approach of fuel control as the OEM ECU is much slower to react and easier to trick. The OBDII cars while nothing like modern ECU's are much faster to adapt and as a result much harder to trick into doing what you want instead of what it wants and really should have a better solution than the one provided by CT. I understand why they did what they did, but it is far from ideal.
Best of luck and make sure the car is safe before you boost it. Again sorry for the long post but this can be a complex problem.
Dave
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Lol long post but now i understand why the fpr cant be adjusted. It answers my question as well as gives me more background on the car. As for boist i did ask bisi. He said it is drivable, he would reflash it but i told him i dont track it and for normal driving it would be ok, it was mire the heat soak of constant tracking. According to him for my stock ct set up he said just a few points would be perfect for him as right now im running what he called on the edge or aggressive. Too bad i couldnt have just undid my 02 sensor in test pipe and stuck it there and put a fan literally in the air vent to provide the most realistic approach.
Thanks dave for helping me to understand my info. As you can see the red line in the run was the worst and was also the third so i understand what ppls refer to as "heat soak". Even the first run the car sat for 10 min prior to the run.
This may mean nothing but will mixing gas brands do anything to timming? I always ONLY run mobil and i firgot to fill up so i didnt want to dyno as i was literally almist on E so i put chevron in. That wouldnt make a diff i dont think.
Again thanks dave as i would prob have jacked my fpr up.
Thanks dave for helping me to understand my info. As you can see the red line in the run was the worst and was also the third so i understand what ppls refer to as "heat soak". Even the first run the car sat for 10 min prior to the run.
This may mean nothing but will mixing gas brands do anything to timming? I always ONLY run mobil and i firgot to fill up so i didnt want to dyno as i was literally almist on E so i put chevron in. That wouldnt make a diff i dont think.
Again thanks dave as i would prob have jacked my fpr up.
Cool
So I had mine dyno'd last week and my A/F line looks very similar to yours. I am going to ask mase to email it to me today so I can post it.
We are going to put in a walbro 255 and hopefully that will bring it down.
We are going to put in a walbro 255 and hopefully that will bring it down.
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I just got off the phone with Shad and he said my AF numbers are very common with a CTSC read at the tail pipes. They do not truly represent what the AF is.
I can't speak for your car, but you might want to give him a call.
He has done A LOT of cars, so I feel better about mine now.
I can't speak for your car, but you might want to give him a call.
He has done A LOT of cars, so I feel better about mine now.
Not enough lol. Since like i said at dinner last week she wants to be a teacher so all the rest i get will only be avitar sizemaybe i put my avitar up for a few days lol.
We're not interested in seeing u. Just a larger version of her.
MILF-to-be teacher eh?
And careful..... with ur AF ratios that lean = KABOOOOOM!!!!!!
Read my post above yours.
If memory served me right my car was reading 11.5 A/F ratios when shad showed me the chart throughout the RPMs and at 10psi~.
Here are the videos of the monitor and the location of where the A/F ratios were read from the tailpipes.
So what do you think the true A/F ratios are?
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Dunno, I ordered an X-wifi so I can tell you next week.
Shad called me today, im picking up my car tommorow after a engine rebuild. He smogged it for me too. With a set of catts he had there it passed with flying colors, I normally run cattless. It dynoed 390whp, with my test pipes (ctsc, headers, cat back, AEM f/i controller, RC 550 injectors) 8psi pulley. Ill get the rest of the info tommorow afternoon.
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