Getting Rid Of R&r With Safc Ii, Bump Up Fuel Pressure And Then Down Bring Everything Down With The Safc Ii

[WogsRus]

Hi All

well i had recently had my computer tuned, but now am wondering if i went to the right person, don't get me wrong, 187rwKw at 10 psi is still dam good, but what i can see is that the car is hitting R&R at 4500 rpm.

This is basicaly, because the tuner first pulled the AFR up with teh FPR and then trimmed the values with teh SAFC II wich meant that at 4500rpm we are adding 3%.

So that means R&R is eaven easier to hit.

So to overcome this, i was thinking of bumping teh fuel pressure up 5 psi, lets say, and then bringing all the values down so that at 4500rpm we are taking fuel out. This would mean no R&R as the ecu will no longer see 5.1v.

Is this a correct assumption. I presume so as bending the signal ensures the ecu does not see full voltage.

ONLY question is, how much do i bump the fuel pressure reg up, i don't want to pay for a new run as yet, as i am waiting for a new boost controller, but i just want to see if this would work.

Is there anyway of seing how much increase in pressure gives in fuel flow to the injector and then i could take that bit out by teh SAFC II.

ANY IDEAS< WELCOME. PLEASE

[mad082]

only way to do it safely is with a wideband o2 sensor.

also if he increased the fuel pressure, then he the 3% of the safc should be reducing the signal to the ecu, not increasing it.

Edited October 16, 2006 by mad082

[WogsRus]

nope the map is basically adding 3% at 4500 and then reduces it form there on, like i said, he got teh fuel pressure to be as close to possible for best AFR, so the map bassically goes 0,0,0,0,0,1,1,2,2,3,2,1,0,-2,-5,--6,-8-7-5.

So i need to add more fuel with the fuel reg pressure and then pull the fuel out with the SAFC II???

[R31Nismoid]

You shouldnt be adding pressure at all.

Put the stock fuel reg on it mate. They are perfect.

The tuner should be pulling fuel out of it as all skylines run rich as.

You adding more fuel to the thing isnt helping you.

[WogsRus]

NOPE, you are missing the post, The stock reg is ok, but i am in the process of setting up for a biger turbo ect so this was on the list, so it was already in the system and running.

The map does pull fuel out. You are missing the point a little. What we did instead of taking a shitload of fuel out everywhere, we played arround with the fuel pressure, unitll the map was almost spot on on the stock ecu, and it is very easy to get and works well, the only problem is, and hence my question and downside, that the tuner had to add a littel bit of fuel at 4500rpm, so hence the R&R now comes on more. I did not think to up the fuel pressure more and then BACK the fuel map off with the SAFC. SO

MY question then again is, if the fuel pressure is upped and i take the fuel back out with the SAFC, the computer will see less air and hence fix the R&R, Correct thinking, or not.

WHat i need to know, is how much does the pressure at the injector relate to fuel flow. IE. What PSI rise does to fuel rate.

KAPISH?

[WazR32GTSt]

calm down mate everyone is offering advice the best they can based on the information they are given

maybe you should take it back to the tuner for clarification?

or to another tuner for their advice?

[WogsRus]

I am calm, i am simply asking, if i richen the car up by adding extra fuel via the FPR, and the lean it out with the safc, will that help R&R as teh AFM voltages will be lower????

Thats all mate, all good.

[mad082]

I am calm, i am simply asking, if i richen the car up by adding extra fuel via the FPR, and the lean it out with the safc, will that help R&R as teh AFM voltages will be lower????

theoretically yes.

[WogsRus]

thanks, i'll give it a go and see what happens.

ALSO, does anyone know if you can use one of the jaycar Fuel Mixture displays at all with the stock O2 sensor, only asking as a basic tuning guide.

[mad082]

thanks, i'll give it a go and see what happens.

ALSO, does anyone know if you can use one of the jaycar Fuel Mixture displays at all with the stock O2 sensor, only asking as a basic tuning guide.

you probably could ,but it won't be accurate at all. the stock sensor is only shortband, so it basically says either rich or lean.

[cameron]

Get a Power FC, make things easier!

[WogsRus]

Buga, so the use of the display is virtually usless then. I thorght that the sensor gave a reading out between 0 and 1 volts or something. I take it i am wrong???

No need for a PFC, at the moment, i was just seing if my theory is correnct.

[chrissso]

Buga, so the use of the display is virtually usless then. I thorght that the sensor gave a reading out between 0 and 1 volts or something. I take it i am wrong???

No need for a PFC, at the moment, i was just seing if my theory is correnct.

Thats correct, however, the sensor goes straight from .3 volts at 14.6ish AFR to .7 volts at 14.8ish AFR. That's why the voltage read outs from the sensor on criuse and idel flick back and forth from .3 to .7 v. The computer knows that if it continually adjusts the mixture slightly for the voltage, it knows the mixture is in the 14.7 area.

So for tuning, if the narrow band sensor goes to it's voltage change, it means that you are at 14.7 AFR under boost, by which time the damage will already be done...

Edit... Raising the std rail pressure and trimming down the values is usually a technique to get around fuel/ignition cut and R&R, and also getting more fuel out of stock injectors, or less fuel out of oversize inkectors, etc. All, which is better solved by a PFC.

Edited October 16, 2006 by chrissso

[WogsRus]

I know but i don't want a PFC because i am saving for maybe a wolf or there abouts, something to get rid of the AFM all together. And seing as this is some time away yet, i need to do a fixit job for now. I might just do it by ear. and go from there.

I know that there is a calculation you can do to see how much extra flow the car is getting by upping the fuel flow.

[R31Nismoid]

Who told you that you needed and FPR?

I got into the mid 300's with the stock one

[WogsRus]

No one told me i needed one, it is simply a tuning guide for teh SAFC II. For exactly the reason stated above.

[R31Nismoid]

Not what you said earlier

, but i am in the process of setting up for a biger turbo ect so this was on the list,

[Sydneykid]

Hi All

well i had recently had my computer tuned, but now am wondering if i went to the right person, don't get me wrong, 187rwKw at 10 psi is still dam good, but what i can see is that the car is hitting R&R at 4500 rpm.

This is basicaly, because the tuner first pulled the AFR up with teh FPR and then trimmed the values with teh SAFC II wich meant that at 4500rpm we are adding 3%.

So that means R&R is eaven easier to hit.

So to overcome this, i was thinking of bumping teh fuel pressure up 5 psi, lets say, and then bringing all the values down so that at 4500rpm we are taking fuel out. This would mean no R&R as the ecu will no longer see 5.1v.

Is this a correct assumption. I presume so as bending the signal ensures the ecu does not see full voltage.

ONLY question is, how much do i bump the fuel pressure reg up, i don't want to pay for a new run as yet, as i am waiting for a new boost controller, but i just want to see if this would work.

Is there anyway of seing how much increase in pressure gives in fuel flow to the injector and then i could take that bit out by teh SAFC II.

ANY IDEAS< WELCOME. PLEASE

I understand what you are trying to achieve, but you are perhaps overlooking one point. Sure, using the SAFC to reduce the AFM voltage that the ECU sees, leans out the A/F ratios But it also advances the ignition at the same time. So you can only take out a limited amount of fuel before the advancing ignition causes detonation, or at the very least pre-ignition. This is the usual compromise forced on tuners by AFM voltage benders like SAFC’s.

Keeping the above in mind, increasing the fuel pressure results in a linear increase in fuel flow though the injectors at all durations. But a 10% increase in pressure does not result in a 10% increase in fuel flow. Based on past experiences going from the standard 34-36 psi to 45 psi (~33% increase) results in around a 10% increase in flow.

I gather from what you have said (rather NOT said) is that the tuner leaned out the A/F ratios by REDUCING the fuel pressure. But if he then had to add fuel via the SAFC, he obviously reduced the fuel pressure too far. As you have found out (and he should have known) adding fuel with the SAFC simply brings on R&R mapping earlier. Which is exactly the reverse of what should have been done to avoid triggering R&R.

My suggestion is to take it back to the tuner and tell him what your problem is. This is what I would consider a “warranty” issue and he should fix it for you at no charge. Or at the very least, a small nominal cost.

Hope that was of some help

cheers

Edited October 18, 2006 by Sydneykid

[WogsRus]

I know i said that i am in the setup for a new turbo, and i am, but that's down the line, but for ease of adjusting the AFR it also helps. Anyways.

I have been to the tuner already and told him about the dip, and he told me that it will cost me the same again to get it tuned up, eaven though it's not 100% perfect, beacuse as you ahve already stated, it's a signal bender, so not perfect. Plus he's a bit pissed at me for stating something which was not 100% true on the net, small world hey.

SK, we did not pull the map down with the fuel reg, we are actually running higher fuel pressure, 41 psi. At stock levels the car was lean as hell (yess i do have a new pump Walbro Gss342 direct wire). Either that or the fuel pressure guage is wrong. I wish i could take it back, but i am afraid that he will just tell me to piss off, and being in tassie, he is the only guy that apparantly knows what he is doing.

So i'm a bit stuck between a rock and a hard place. But i will get it retuned down the tarck, once the new ignition is in, and the boost controller, as mine is cactus.

Out of interest then SK, how do you workout fuel flow vs pressure. I would like to play arround with the map a littel myself, but not to the extend of stuffing anything up to much. SO if i could work out theoretical extra fuel flow in % i could then take that same number away with the SAFC II.