I am seeing high injector duty cycles despite the fact I have huge injectors for my power level. I have 750/2200 cc injectors and make around 400 hp on high boost. I can see high 80s no problem. My question is why? Is the Supra fuel pump not adequate ? I have a fuel pressure regulator as well. Perhaps that isn’t dialed in correctly. Thoughts ?

 

Is that a new issue, or something you just noticed? What's your pressure? How's your AFR?

Jason

 

what ecu and i believe the supra pump is a 190lph. how do you have the pump wired? if its the factory wiring then you may be seeing a voltage drop translate into a higher duty cycle. its pretty easy to test. i'm not sure if a 190 is a adequate for your power level

 

i went through this with my car, and the stock car doesn't have a fuel pressure sensor so the ECU doesn't measure it directly, although it will give symptoms.
symptom #1, on my car it wouldn't quite hit the AFR target, it was always a couple tenths off. FC Tweak would add duty cycle, and it wouldn't help.
symptom #2, this took the light bulb to go on, but the HP it listed was getting to be more than was possible with the turbo i had, by a lot.

i ended up building a spreadsheet based on the maths in Hugh Mac Hinnes's Turbocharging book, and between the FC Tweak and my sheet, it was clear something was wrong.
i replaced the fuel pump and duty cycle is way down, AFR is too rich, lol

i could have checked fuel pressure too

 

I am seeing 38psi at idle. I believe this is the correct pressure. I’ve been reading a bit and it seems 43.5 is the correct base pressure on a fully warmed up car. If you subtract the idle vacuum of about 7psi you get 36.5. So I am thinking 38psi is correct . Of course this assumes what I am reading is correct

my afr is great. Little rich. Around 10.8

 

I do not know how the pump is wired. But I can check. I can search the faq for more info.

but it sounds like you are saying that the Supra pump wasn’t the right choice for this car. Is there a better pump that’s plug and play. I’ll buy it.

 

@j9fd3s

i am 95% tuned so I think I am hitting my targets.

oh man. My hp estimates are wayyyy off. But I think that number is kinda fake. It doesn’t know what turbo you are running. I thought it was just a made up number. My car shows a potential or 700hp. And that I should be at 560 right now. I think it’s just a simple calc of what your injectors could produce. I don’t know. I don’t know where Xavier gets those number at all


thsts awesome you solved your issue with a better pump. As I learn more about this it seems that could be my issue bc based on what I am reading my fuel pressure is great. (I could be wrong). I just started to focus on this. So I am just now starting to learn.

what pump did you go with? Is there a drop in plug and play that good for 450ish hp?

 

If the fuel pump can't keep up, the fuel pressure measurement will look OK at idle but the fuel pressure will not be high enough at high RPM and high load. For instance, if your base pressure is set to 40psi then you should always measure fuel pressure 40psi higher than manifold pressure. When the boost is 10psi, the fuel pressure should be 50psi. Anything less than that means the fuel pump isn't flowing enough fuel to maintain pressure when it matters. A fuel pressure sensor might be a useful thing to add to the car, if you really want to know. Even if the PowerFC can't convert the sensor voltage to pressure, you can build yourself a cheat sheet to remind yourself what voltage you expect at 10psi boost or 15psi boost or whatever.

Also, if you've got an aftermarket fuel pump you should not be using the factory fuel pump wiring or the factory bulkhead connector. Both of those are known to cause low voltage at the pump, which will prevent it from flowing the advertised amount of fuel. It's common to see more than 1V lost in the factory wiring, which will affect flow significantly for a fuel pump.

 

how do I know what the voltage is at the pump. Is that the reason on the power fc sensor check?

 

well the PFC knows engine size, rpm, injector size, injector duty, and potentially AFR, so it has all the info to come up with a good estimate.
i'm not 100% sure where it comes from, its possible the PFC is making it.

i ended up using a Deatschwerks pump, although there are plenty of choices. my sheet wants at least 310lph at 60psi for 450hp and 4x1000cc injectors. keep in mind this is kind of a ballpark number, it depends on the AFR you want to run, and duty cycle you want to end up with, Xavier wants less than 85% to keep the injector driver cooler

for fuel pressure it should be ~38psi at idle, and then it goes up with boost, so at 15psi of boost, you should see 53psi. if you don't its a problem.

with my specific car, which is a 13B-REW in an FC chassis, with an FC turbo the PFC said 212hp at 7psi, which is about right i think.
i did some testing and found my exhaust was awful, so i fixed that, and hp went to 310. this is not possible with a stock FC turbo.
i fixed the pump in there (the goofball O ring was leaking), and hp went to 247, which is what a stock FC turbo can do.
round 2 was an upgraded compressor which came out of the gate at 315hp, but after replacing the fuel pump with a DW, it was like 280 or something.

current setup is an HKS Sport kit, which was advertised at 350hp at 13psi, and i'm currently ~9psi and 305, so i'm right there.

so in summary: the dyno number is reasonable. if you have a 450hp car and it says you're making 475 i wouldn't worry, but if it thinks you're making 700hp, something does not add up.
second, fuel pressure needs to go up with boost, so you can either check that, or do math

 

my sheet shows
750/2200cc injectors at 85% duty, and i'm assuming 7000rpm; is enough for 683hp and it takes 35psi of boost to get there
going the other way, at 420hp (15psi), 7000rpm, and 750/2200 injectors you should be around 55% injector duty.

so something is up!

 

I'm not sure on the FC but I upgraded my fuel pump on the FD and my wiring melted at the fuel pump connector. If your wiring is stock and your pump isn't I'd do a rewire. Tons of examples in the forum and I think there are kits out there as well. Lucky for me I got stranded at Dale Clark's house so we made a project out of it or I would have had to tow it.

 

Be weary of those kits out there that just boost the voltage to the STOCK connector. If the wiring does not go into the tank, it's wrong.

We have a video on our YouTube of the correct way to adapt a stock hanger. There are many variations but the methods we cover are the key points to address by whatever means you see fit.

 

what you’re saying makes a lot of sense. And I now understand why I thought it was entirely made up. for me, it thinks I am making 560rwhp so I discounted the number as made up. But I get it now. It thinks I am making all this power bc my duty is so high which is the red herring. Thanks for taking the time to explain this to me.

I am going to send you a quick pm about something

 

yes. I saw a kit on YouTube that replaces the connector from the pump in the tank. Maybe this is the next project. Or maybe I should just the replace the pump. Many people are saying the Supra pump isn’t adequate for 400 hp in our cars.