Tuning your Feul Pressure for PERFORMANCE
 

Hey all.

I have tuned a N/A car with a AdjustableFeul Preesure Regulator(AFPR)

We set the AFPR to standard 2.5 bar then we ran on dyno and it made the same power. Gewd. Then we Slowly increase the FP buy .1. power and torquw went up very Gradurly. then at 2.9 bar The power Dropped BIG time. So we set it back to 2.8 and left it at that! KEWL

anyway now im about to tune it on my turbo car. Spoke to a Guru last night and he said ajusting the FP will not Increase performance only control detonation, and he was adimant!

With a turbo car whats going happen? is there gonna be a point were the power Drops? or is the car just going to run execessivly rich?

Re: Tuning your Feul Pressure for PERFORMANCE
 

tune with real engine management if you want more power.

an fpr will only get you so far. and by far I mean it will get you rich and semi safe.

Re: Tuning your Feul Pressure for PERFORMANCE
 

Okie i understand adjusting the FP will only get you so far/is a very Small piece of the puzzle. i just want to get it right.

how do you know when you have gone to far? so okie i have a mangment system but it is set to super super rich and i dont know why. where would be a gewd place to start. reset the FP to stock and take it from there?

Im nervious cos Pinging/Detonating a turbo kar = big Kaboom

Re: Tuning your Feul Pressure for PERFORMANCE
 

Get a rope. "gewd", "kar", "KEWL" ::) :8

Re: Tuning your Feul Pressure for PERFORMANCE
 

get a wideband o2 sensor. tuning on the dyno for power is stupid without an AF reading.

Youd start rich, make power

lean it out, make more power

lean it out more, ,make more power

lean it out even more, start making more power then BOOM!

youd blow it up and bitch about how your engine blew up.

with forced induction, being leaner to the point right before detonation occurs will yield most power (in many cases) but its also the more dangerous place to be, any step leaner will result in knock and detonation.

Re: Tuning your Feul Pressure for PERFORMANCE
 

THE BOTTOM LINE IS I WANT TO RUN A NORMAL SAFE FEUL PRESSURE NOT Above 5

at the moment the car is setup to 5 and 5.5 Bars but the standerd car is only set at 3. what do you guys set yours to be safe +-. I do have Bigger Injectors and a managment to "Give " the car more feul. hence i dont need to do it from the FPR......

Re: Tuning your Feul Pressure for PERFORMANCE
 

Oh man, that is so wrong.

There is a point when you make less power by being lean and trust me it aint as lean as you might think.

Re: Tuning your Feul Pressure for PERFORMANCE
 

Hope you got the fire department on speed dial mofo.

80psi FP? What the ---- are you thinking??? If you gotta crank the FP up that much to get the car to run right, something is VERY wrong!!!
5bar is not safe at all. you really shouldnt exceed 3bar without having a fuel system that can safely support it, or an engine that needs it.

Tuning w/ just fuel pressure is dangerous and wrong.

Re: Tuning your Feul Pressure for PERFORMANCE
 

set pressure at 40~43 psi leave it alone, and add fuel through your fuel maps. If you don't have a tuning program running on your ECU then get one soon.

Re: Tuning your Feul Pressure for PERFORMANCE
 

Another problem to add to this debate is the fact of atomization...basicly reducing the fuel droplets to the smallest size possible to mix with the incoming air to provide the most complete and powerful combustion. This factor right here is why carbs are still king on high-power, high rpm n/a drag cars. People can argue that the fule injector itself does the atomizing, which it does to a point. Increasing fuel pressure does not increase fuel atomization, rather it decreases it by increasing the size of the fuel droplets...in order to provide more fuel. And seeing that the injector is placed so close to the ports on the head, it gives the fuel even less time to mix properly with the incoming air charge.
Of course running too low a fuel pressure will also produce the same results as too high a pressure, so it's a pretty thin line as to how far you can push your injectors. Stock pressure settings are usually the closest to best atomization, but you can go a little higher than that. It's best to tune fuel amount off the ecu with how long the injector stays open to increase fuel than to raise the fuel pressure itself.

Re: Tuning your Feul Pressure for PERFORMANCE
 

okay well with subaru's there is a small window. from what i have learned atleast.

Re: Tuning your Feul Pressure for PERFORMANCE
 

40~43 psi

Okie What is 40~43 psi in Bar's pressure? i have been chatting to some Guru's and they say the Stock feul pressure is 3 bar so i must up it to 3.5 and leave it at THAT!!!. the last time the car whent for tune up they Adjusted the Feul Pressure but to what im not sure but previosly i have seen the Feul pressure sit at 5 bar at startup will get it sorted....
That is Very valid Piont So increaseing te Feul Pressure change's the Spray Pattern!?!?!. You should NOT be giveing more feul Via you FPR!?!?!

Re: Tuning your Feul Pressure for PERFORMANCE
 

Divide the amount of psi by 14.5037 to get the amount in bar. As stated before, set the fuel pressure to 40-43 psi, and then get a fuel management such as Uberdata, Crome, Crome-Pro, Neptune, etc., etc., and properly tune the fuel and ignition maps.

Re: Tuning your Feul Pressure for PERFORMANCE
 

the car is N/A. Why even bother fuckign with fuel pressure. you're only gonna squeeze out 1hp if you're lucky. go boost or go home.

Re: Tuning your Feul Pressure for PERFORMANCE
 

agreed :y

Re: Tuning your Feul Pressure for PERFORMANCE
 

We Squeezed out 9 Hp (when u N/A you scrtach for every drop of power...)

Well the new car is Turbo so just want to set the FPR then tune with the Managment...

Re: Tuning your Feul Pressure for PERFORMANCE
 

whats with you and FPR's ???
For this "turbo" car , ditch all that get a ecu chipped and some 450's ..you'l thank everyone later

Re: Tuning your Feul Pressure for PERFORMANCE
 

Leave the fuel pressure alone. The only reason you made more power on that NA car (if you even did, which I doubt) is because you got lucky. If you went back on that same NA car and put the fuel pressure back to what it was, and then tuned it with whatever engine management possible, you would see better results.

Adjustable FPR are only needed if your pump/lines flow too much for the stock one to handle, or you want to squeeze a bit more fuel out of your injectors.

Re: Tuning your Feul Pressure for PERFORMANCE
 

Tuning fuel is not really the best way to make power. Gasoline's max power range is in the range of 12-13:1 AFR. This has been confirmed by engineers doing testing on single cylinder engines in controlled environments. Based on some thought on safety factor in regards to combustion chamber conditions one should chose a fuel ratio in that range. Boosted vehicles generally go slightly richer to gain an even larger safety factor but is not necessary really as the same safety factor can be applied via tuning ignition timing. As far as fuel pressure is concerned, I wouldn't worry about better or worse fuel atomization based on pressure. Generally speaking injector companies set fuel atomization to be best at a paticular pressure. In our case it will be in the 3bar area(or 40-45psi).

PS: Carbs will always make less power than EFI because of precision. It's just entirely too ridiculous to design an EFI fuel system for 5000hp engines. The design and manufacturing of the necessary components is just not feasible, so they use carbs as mechanically they are easier to develop and manufacture.

Re: Tuning your Feul Pressure for PERFORMANCE
 

Sorry...check again. You had it good up until the bottom paragraph. Anyone who has every worked with carbs vs. injection on high hp race applications will tell you the same thing...carbs are king when it comes to high rpm fuel atomization. Downside to carbs is slow response time off the line and they can be very picky when it comes to lower rpm tuning and afr's, but when your all-motor car spends most of it's time above say a 5,000 rpm mark, carbs will kill any injection system as far as fuel atomization and power.

Re: Tuning your Feul Pressure for PERFORMANCE
 

omg not the efi vs. carb arguement :l

Re: Tuning your Feul Pressure for PERFORMANCE
 

Okay, find me ONE dyno chart or academic article which illustrates carbs making more power than an EFI system. Both properly tuned. I've challenged a number of people to this, none have succeeded. I generally can find a handful of half assed attempts at it but the EFI system always ends up making more power. The carb is better myth is just that, a myth. Cheaper, simpler, better bang for the buck? Yes. More efficient? Absolutely not.

Re: Tuning your Feul Pressure for PERFORMANCE
 

Actually, these days efi is cheaper than good carbs. Most people hear "carbs" and think of old Holleys or Edelbrock...I'm talking about side-drafts and down-draft carbs like webers, solos, mikuni's etc. These carbs won't make more power than efi at all...until they reach over a certain rpm point (like I said, usually a pretty high one, and continue to become more efficient as rpm increases). Efficiency and carbs is a joke, there's no denying that efi owns it in that aspect, as well as the torque curve. I wish I had a copy of the interview done by Honda Tuning mag from october '03 with bisi...he explains some things misunderstood with carbs (he holds a chemical engineering degree...he knows his ----), and here are some highlights I did a quick search for. http://www.autoindustriya.com/yabbse...2945.msg285730
Not saying that injectors can't be made to produce the same profinciency of atomization as carbs do, it's just not feesable with where they'd have to sit. Not to mention it'd have to be an itb setup.
For efficiency and fuel economy, efi is the way. I personally wouldn't want to deal with all the issues associated with carbs on any of my cars, n/a or not...way too many problems.

Re: Tuning your Feul Pressure for PERFORMANCE
 

I need a legit source from a legit person. Bisi interjecting his opinions is not of interest to me. I like to see hard data or reasonable logic one way or the other. You've offered me neither. Again, I need a legit source of carbs producing more power than EFI.

Re: Tuning your Feul Pressure for PERFORMANCE
 

Why does an organization such as Nascar (OMG NASCAR~!!!!) use carbs? 750-850 hp at 9000 rpms. Do they do it just to keep things simple, or is there another reason?

Re: Tuning your Feul Pressure for PERFORMANCE
 

Carbs smarbs, I use direct bio deisel injection via the intake manifold. I don't have fuel injection either. Just direct port with nozzles and a 60lb bottle :y. I made 3.8whp on my Murray lawnmower. Suck on that you bitch ass trick. ZOMG fuel injection is better for street cars and boost, at least for the average tuner. This isn't NascarHMT.com.

Re: Tuning your Feul Pressure for PERFORMANCE
 

NASCAR is not a good source for this at all.

They use such old technology everywhere they can. The suspension design is old and not very good and guess what, so is the engine.

Also they try to make the playing field pretty level. Using carbs is a good way of doing that.


The real power producing sport (non-drag of course) F1 uses EFI. They wouldn't make nearly the power that they do or as reliable is they used carbs.

Re: Tuning your Feul Pressure for PERFORMANCE
 

Tuning with fuel pressure is good for gross (big) adjustments, if you need a huge adjustment do it with fuel pressure. BUT you'll still need to fine tune by what ever means to get it right and stay safe. If you're running 70 psi, get larger injectors and then back fuel pressure down by a precentage roughly equivilant to the increase in injector size and start there.

You can look at fuel trims with a scan tool and check fuel trims, if your ECU is add or subtracting large amounts of fuel, play with fuel pressure to get the trims closer to +/- 0 so long as the AFR under load stays safe. It gets diffrent if you use a 1:1 rising rate FPR vs. a static. Moral of the story, fuel pressure for gross adjustments, but you still need most likely need some fine control over AFRs.

Re: Tuning your Feul Pressure for PERFORMANCE
 

I knew that all types of "real" racing still (mostly) use EFI these days. Just wondering if Nascar was really that bad or there was some special reason behind it.

Re: Tuning your Feul Pressure for PERFORMANCE
 

To retain that redneck appeal.

Re: Tuning your Feul Pressure for PERFORMANCE
 

Ahh, but F1 uses TBI with exact length runners for maximum power. I really don't see why Nascar would even benefit from efi...they pretty much just rev their motors to 9k and stay there almost the entire race. F1 on the other hand has alot of changes in rpm.How is he "interjecting" his opinions? He holds a degree in chemical engineering...do you? Regardless, this argument has been around since the dawn of EFI and probably will be around for much longer. Great improvements have been made in injector technology and can only continue to get better. Take for example the Lucas plate style injector...they give a better atomization pattern at high fuel pressure than pintle style.

Re: Tuning your Feul Pressure for PERFORMANCE
 

I'll be a Civil/Environmental engineer in 2 years. Does that mean once I am I can say ridiculous ---- and just claim, "Hey, I'm an engineer!" Again, an engineer is a person of applied science. If he has no data validating his opinion its meaningless.

Re: Tuning your Feul Pressure for PERFORMANCE
 

Obviously he has hard data if he's applying it to his cars ::) I'm done trying to argue a point, this thread has become useless. Somebody just lock it up already :P