Right, now I see it. My statement with parallel to the radiator is wrong.
Rauq's Twincharged LSJ in SC - #240 - GOBZILA
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Rauq
Goblin Guru
I installed a 340lph fuel pump recently and my base fuel pressure increased by about 10% (~42psi to ~46/47psi). I drove the car once without adjusting the regulator and fuel trims were expectedly rich. Against all common sense, I adjusted the baseline fuel pressure and updated my tune strategy at the same time.
I updated my tune with injector scaling (50% or 40lb/hr) versus my previous scheme (62# injector flow rate and 1.3x voltage multiplier). When I installed the turbo, I included a 4" diameter section of intake tube, about 12" long, after the A2A intercooler for the MAF. For reference. the MAF is the same part number as is used in the LS7 C6 Z06 corvette which is in a 4" diameter intake. I believe that without this modification, I would have run out of range with the stock the MAF sensor. As it is, on low boost (18psi on the turbo), I peak about 9khz, with a valid sensor range of about 12khz. Fitting a smooth curve to the MAF in the tune yielded a MAF curve plateauing at the max 512g/s at about 10.5khz, thus the need to go to injector scaling to turn the boost up any further.
I've driven the car once on this new tune and it drove well within the correction capabilities of closed loop fuel trims. I will be dialing in the MAF and VE tables here soon and maybe dabbling in spark tuning. For now, I'm running the GMS1 timing table, which doesn't really look like it creates any KR issues for me.
I'm signed up to run the Sunday HPDE at Gridlife at CMP in April which should be a great time. A buddy of mine is running his LS swapped FC in Time Attack, so I may masquerade as crew for him as well.
I updated my tune with injector scaling (50% or 40lb/hr) versus my previous scheme (62# injector flow rate and 1.3x voltage multiplier). When I installed the turbo, I included a 4" diameter section of intake tube, about 12" long, after the A2A intercooler for the MAF. For reference. the MAF is the same part number as is used in the LS7 C6 Z06 corvette which is in a 4" diameter intake. I believe that without this modification, I would have run out of range with the stock the MAF sensor. As it is, on low boost (18psi on the turbo), I peak about 9khz, with a valid sensor range of about 12khz. Fitting a smooth curve to the MAF in the tune yielded a MAF curve plateauing at the max 512g/s at about 10.5khz, thus the need to go to injector scaling to turn the boost up any further.
I've driven the car once on this new tune and it drove well within the correction capabilities of closed loop fuel trims. I will be dialing in the MAF and VE tables here soon and maybe dabbling in spark tuning. For now, I'm running the GMS1 timing table, which doesn't really look like it creates any KR issues for me.
I'm signed up to run the Sunday HPDE at Gridlife at CMP in April which should be a great time. A buddy of mine is running his LS swapped FC in Time Attack, so I may masquerade as crew for him as well.
MX184
Well-Known Member
I tried to run there last year in the superunlimited class and they denied entry saying they needed enough open wheeled cars to have their own run group. I didnt think about the hpde angle. I'm totally jealous. Enjoy the event!!
Which fuel pump did you buy? and how did you measure the fuel pressure?
I looked in HP Tuners and hoped that the fuel pressure would be logged, but only found the fuel tank pressure. I wonder if there is a way to install a fuel pressure sensor and feed it to the fuel tank pressure or AC pressure sensor to the ECU.
Ross
Goblin Guru
There is a schrader valve at the end of the fuel rail, and the threads happen to fit my AC pressure gauge set.
My LSJ gets 59-63 PSI of fuel pressure.
I did an arduino oil pressure gauge by removing the LSJ oil plug, and putting in a pressure sensor. It could be done for fuel pressure too.
Use a 5V pressure sensor, and you could wire it to the AC pressure sensor.
My LSJ gets 59-63 PSI of fuel pressure.
I did an arduino oil pressure gauge by removing the LSJ oil plug, and putting in a pressure sensor. It could be done for fuel pressure too.
Use a 5V pressure sensor, and you could wire it to the AC pressure sensor.
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Rauq
Goblin Guru
They did require that my front wheels are covered. They said DF's fenders will work just fine so I ordered them.
Racetronix. Nearly drop in, just required a little trimming of the in-tank hose inlet and around the electrical connector on the plug.
I have a boost referenced fuel pressure regulator mounted to the fuel rail with an analog gauge on it.
You actually can log through the fuel tank pressure input signal wire. I hijacked that input to log the supercharger inlet pressure sensor which isn't loggable in HP Tuners for some reason. You could also use it to log fuel pressure or anything else you can put a 0-5v sensor on. Just wanted to reiterate that on an LSJ you can wire two separate 0-5v sensors into the ECM, one on the AC pressure sensor input and the other on the fuel tank pressure sensor input. I don't think there are any other available channels, though. I will double check again sometime to be sure.
How much fuel pressure are you getting with that pump? I just ordered my boost reference fuel pressure regulator. I would love to go with a constant fuel pressure to the injectors, but currently I'm making 18.5psi boost and my fuel pump creates a maximum of 60psi, under load 54psi. That means if I want to go constant pressure, I have to regulate the pressure down to around 34psi, which I think with E85 I have to get a new pump.
Rauq
Goblin Guru
Base is 42psi with the engine off, so it idles at maybe 38 off the top of my head? Then it's 1:1 rising rate with boost. According to my gopro log of the gauge, it rises as it should... so it makes at least mid-60s psi of fuel pressure.
One of the biggest reasons to go boost reference is to get the fuel pressure low enough that big injectors will idle well, and still flow enough to make big power. I'm not sure if 60# injectors would require a BRFPS but I can't see 80# injectors idling well at 60psi of fuel pressure.
I'm not sure why a constant fuel pressure setup would require the base fuel pressure to be so low, or why doing that with E would require a new pump aside from fuel compatibility?
One of the biggest reasons to go boost reference is to get the fuel pressure low enough that big injectors will idle well, and still flow enough to make big power. I'm not sure if 60# injectors would require a BRFPS but I can't see 80# injectors idling well at 60psi of fuel pressure.
I'm not sure why a constant fuel pressure setup would require the base fuel pressure to be so low, or why doing that with E would require a new pump aside from fuel compatibility?
Great, that is for sure more than my pump is doing.
For me the main adavantage of going with constant fuel pressue is to have one variable less to worry about while tuning the car.
However, I put together this excel and calculated the needed injector size at the current boost level I run. Hopefully there is no error in the calculation.
Knowing that my Siemens Deka make 60lbs/h at 43.5psi and upt to 85lbs/h at 87psi I think what I want to accomplish is not possible.
Either I have to deal with variable fuel pressure, need a pump which has more pressure or larger injectors.
But this is also all theory. Since you are only at a very short time at high rpm and high boost I wonder how much tolerance would be in this.
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Rauq
Goblin Guru
I'm with you in theory but somewhere the math breaks down. Is it that, for every revolution, you only have 2 intake strokes, not 4? So your displacement -> m^3/hr should be halved, although I didn't do the math on that step of the conversion for myself. In that case, though, it would seem more reasonable that 18psi can be done on 75lb/hr worth of injector (which is feasibly a 60lb/hr injector run at higher than base (42psi) fuel pressure).
One thing to note, I don't completely understand the conversion of fuel pressure to injector flow, but Deatsch Werks (see the lower calculator) and other reputable companies with calculators seem to indicate it's not a linear relation; i.e., 60lb/hr injectors at 42psi don't flow 50% more at 61psi.
In any case, I think you're overcomplicating things because fuel injector calculators are common enough and fairly consistent enough to draw reasonable conclusions (see the upper calculator in the previous link). According to their calculator, a 300hp supercharged 4 cylinder on E85 needs 62lb/hr worth of injector at 85% duty cycle. Since a stock fuel system LSJ would run an effective 42psi fuel pressure making 18psi of boost (~60-18), that lines up pretty well in my opinion.
One thing to note, I don't completely understand the conversion of fuel pressure to injector flow, but Deatsch Werks (see the lower calculator) and other reputable companies with calculators seem to indicate it's not a linear relation; i.e., 60lb/hr injectors at 42psi don't flow 50% more at 61psi.
In any case, I think you're overcomplicating things because fuel injector calculators are common enough and fairly consistent enough to draw reasonable conclusions (see the upper calculator in the previous link). According to their calculator, a 300hp supercharged 4 cylinder on E85 needs 62lb/hr worth of injector at 85% duty cycle. Since a stock fuel system LSJ would run an effective 42psi fuel pressure making 18psi of boost (~60-18), that lines up pretty well in my opinion.
You're right, every value below the displacement needs to be devided by 2 due to that error. I'll do that tomorrow when I'm back at the pc.
I'll check out the calculator tomorrow.
I don't have a stock LSJ fuel system. I have the LAP 2.2NA fuel pump. Pressure falls down to the mid 50s under wot. That's probably the next thing I will change, that's why I asked so many questions about your pump. Don't want to buy a new pump and replace it again in a few month.
Another question, do you have your tune available? Would love to see what timing your running with 24psi boost.
Rauq
Goblin Guru
I think the point still stands since as far as I know the base design is the same with a returnless pump and regulator internal to the pump housing. The only difference would be if the stock pump can't keep up, so instead of going from 60->42psi effective fuel pressure when making 18psi boost, it might drop even further.
To be honest right now I'm just running a mix of the stock and GM Stage 1 timing tables, stock mostly in the mid-range area as I don't think the more advanced timing of the GMS1 tune accounts very well for how much boost I can make at like 3000rpms. I would like to get it on a dyno someday and do some actual spark tuning.
Here is the corrected table.
This is part of the issue I have. For the Siemens 60lbs/h injectors I do not have a flow rate vs fuel pressure. I found a conversion table from the Ford Perfomance team to the ECU we have in the HP Tuner forum and modified that to the LSJ tables. That brought me pretty close to a decent tune.
I have 2 points from the data sheet and can only assume its a linear equation which would result in the picture below. That brings me to the point of running the injectors at a constant pressure. Now, I know already that with my current set up on tank gas (not E85) the fuel pressure drops from 60psi idle to ~55psi under wot, high rpm and boost.
If I want constant fuel pressure that means I need to decut the boost from the lowest pressure I saw. --> 55-18.5psi = ~36.5psi. If it would be somehow linear 55psi would result in 56lbs/h flow. This would mean I can go up to AFR 11.54 with my current pump, current boost and current injetors. A new fuel pump would solve that issue, if it would deliver 65psi under wot. This results in 62lbs/h. Still not enough for E85 and power enrichment.
Maybe right if you just look at the injector size, but it is not to overcomplicated if you dial in your injetors yourself and it helps to understand how the ECU is dealing with the variables involved. I also think that the calulators at the websites are less accurate (but accurate enough) to guestimate the injectors sizes.
Again, if I there would be a decent set up for the injetor, that would make things easier, but since this is not existing I would like to take as much unkown or guestimated variables out of the equation.
Regarding E85 I have a million more questions, but will start a new topic in the forum, when I am ready for it.
Rauq
Goblin Guru
For quick clarification, when you refer to constant fuel pressure, are you referring to a non-referenced pressure regulated setup where it will try to maintain the same fuel pressure regardless of what the motor is doing, or a manifold pressure referenced pressure regulated setup where the injectors will see the same effective fuel pressure at all manifold pressures?
Out of curiosity, what does your stock tune fuel injector vs kpa table look like? Is it linear? I found this that you may find interesting as well. Obviously fuel pressure vs injector flow is not the same as injector flow rate vs manifold vacuum, but I'm curious how the correlate (or don't).
Out of curiosity, what does your stock tune fuel injector vs kpa table look like? Is it linear? I found this that you may find interesting as well. Obviously fuel pressure vs injector flow is not the same as injector flow rate vs manifold vacuum, but I'm curious how the correlate (or don't).
Rauq
Goblin Guru
I am not going to pretend to be a good builder or a good driver, but the car's performance this past weekend suggests I'm more the former than the latter. It didn't blow up and it made fun noises, so I was happy.
When I am talking about constant fuel pressure I am talking about manifold pressure referenced pressure regulated setup. This way I can set the ECU to one constant (and known) value.
Not sure what you mean by stock tune. The stock tune of the LSJ? My tune was an unkown state when I bought the engine. I started with the GM stage2 tune and adjusted it. The stage 2 standard table looks like this. The dotted line is a linear trendline:
I used the table out of this thread to and made it matching the values of the LSJ tables.
In theory the table would look like this:
But the LSJ ECU only allows to have values entered up to 63lb/h. I had to use the voltage table and set a multiplicator fixed to 1.3 over the complete table to scale the injectors down.
Manifold pressure in kPa also did not really told me something, so I created another graph where i converted from kPa to PSI. :
The curve is almost, but not quite linear.
The table in HP Tuners is called Manifold Vacuum (kPa). If I see that correctly, than this table is inverse. Means -17.4psi of Vacuum = 17.4 psi of Boost. What happens if you are above that range, I don't know. Maybe it used the last value, maybe it increases linear ?!? I am only 1 psi above that, so for me that problem is way smaller as it might be for you.
The LSJ ECU has no feedback over the fuel pressure, so the fuel pressure is set to either a fixed value or some sort of mathematical curve. Probably determined during the development of the engine. The two most important pressures to get the right flow are fuel pressure - the manifold pressure, then look in the data of the injectors to find the lb-h.
What I would like to achieve is a constant pressure difference between the fuel pressure and the manifold pressure --> fuelpressure worse case - maximum boost. I described that above already.
Hearing that noise makes me wanting to twin charge as well
Can you add the GPS Speed and G Force sticker in future videos? I love to see them.
Rauq
Goblin Guru
In that case I don't think you need to be worried about having enough fuel injector. The only reason you'd set your base pressure that low is to ensure the injectors can meter out a small enough flow for the engine to idle well (which isn't a huge concern with injectors smaller than 80#). I would be inclined to think the the stock in-tank regulator in the deadheaded setup is more incapable of making more than mid-50psi WOT than the pump.
I was mainly curious if any factory tune's injector flow rate vs kpa chart were linear. If it weren't, you'd have a hard time generating that curve without supplied data. All good.
I've read generally that when tables are maxed out, they continue calculating in some method, but I don't generally trust that. I'm also with you, I also concluded that table is inverse with pressure. Pretty silly.
I'm tracking. Low on my list, but still on my list, of reasons to go with a referenced fuel pressure setup is that it made that injector flow rate vs kpa table easy to sort with a single number all the way across.
Rauq
Goblin Guru
I never thought much of those stickers but here you go. I have a buddy with a Dragy who's been wanting me to log some stuff so hopefully I can do better data videos in the future.Hearing that noise makes me wanting to twin charge as well