370cc injectors + ajd. fpr - questions!

[crzycav86]

My fuel setup(sr injectors, walbro, safc2) could not handle 10 psi from the z31 turbo. The wideband showed the a/f up to 13.5:1 at peak torque, and the safc was not adding any fuel.

So I installed an adjustable fpr to increase base pressure. What I want to know is how much should I increase the base pressure to run the 250whp safely?(yes, the z31 turbo made 250hp @11psi on the lean runs)

According to some formula, new flow=old flow*(new pressure/old pressure)^.5 If I recall correctly. So with a base pressure of 60 psi, the injectors should flow about 450cc worth of fuel. Can anyone verify that this is enough for 250whp? Can anyone tell me if 60psi base pressure is safe?

Now, suppose the boost bug strikes again really soon. Would it be safe to turn up the boost to 15psi and increase the fuel pressure more if necessary? I'm aware that the turbo will be out of its efficiency range, but I'm starting to get very curious. (base timing would be retarded more)

Thanks in advance.

[Jookmasta]

i dont think the turbo will b out of its range at 1 bar.................as for ur fuel, ur gonna soon need bigger injectors but i guess the increase in fuel pressure could compensate for the a/f's. ur main worry would be if the injectors are going to handle em. did u get the injectors flow tested and cleaned? btw, me and u have very similar setups unless ur not a KA24DE

[C-Kwik]

Out of curiosity, can the SAFC monitor the duty cycle? Is it hitting 100%? If not, then it might be a limitation of the MAF not allowing the SAFC to add any more fuel. Just a thought.

As far as using a FPR, you can do it, but keep in mind that higher fuel pressures equate to less overall flow from the pump. Depending on how much pressure, it couls starve the injectors when trying to flow large amounts of fuel. If you can find out the flow vs pressure of your fuel pump, you should be able to calculate the max flow you can get at each pressure.

[Structure240sx]

hardwire your fuel pump so it gets a soild 12-14 volts

did you check peak maf voltage on the safc?

no it doesnt not show duty cycle ckiwk

also when a maf gets maxed out the ecu will dump in all the fuel it has. i foudn this out when i used a stock maf roubleshooting and also my z32 maf last time at the dyno.

[:: orion ::]

I ran ~58psi base pressure (made 370cc act like ~414cc IIRC) with 9psi from my T04E 57-trim compressor...and it was fine for ~6 months until I upgraded to JWT/50lb.

I would estimate ~255-260rwhp.

This was with my hacked MAF...so the flow capacity was increaded a little...and I WAS seeing ~5.11 volts in the upper RPMs.

- Brian

[Jookmasta]

i concur as i am in the same boat as what structure described at the moment. if u are running a stock MAF which i am doing also, if u have maxed out ur MAF, u will just start dumping as much fuel as possible. definitely at that power level, ur gonna need an MAF upgrade. whats ur base timing at btw?

[crzycav86]

i dont think the turbo will b out of its range at 1 bar.................as for ur fuel, ur gonna soon need bigger injectors but i guess the increase in fuel pressure could compensate for the a/f's. ur main worry would be if the injectors are going to handle em. did u get the injectors flow tested and cleaned? btw, me and u have very similar setups unless ur not a KA24DE

Yeah, the reason I went with the fpr is so I wouldn't have to get bigger injectors. I did not get them flow tested or cleaned. I just received them in the sr rail, so I popped them out and put them in the ka.

As far as using a FPR, you can do it, but keep in mind that higher fuel pressures equate to less overall flow from the pump. Depending on how much pressure, it couls starve the injectors when trying to flow large amounts of fuel. If you can find out the flow vs pressure of your fuel pump, you should be able to calculate the max flow you can get at each pressure.

Ok. So I found a map for some walbro pumps.



Assuming I have the lowest flowing walbro on that chart(GSS315), at 70psi, the pump will flow 150lph. Converting that to cc: (150L/1hour)*(1hour/60min)*(1000cc/1L)=2500cc/min

The 370cc injectors should be flowing 470cc/min at 70psi. I guess since there's 4 injectors, the total flow would be 470cc/min*4=1880cc/min, which is below the 2500cc/min. I don't know if I did that last part right, but it sounds good imo.

hardwire your fuel pump so it gets a soild 12-14 volts

did you check peak maf voltage on the safc?

no it doesnt not show duty cycle ckiwk

also when a maf gets maxed out the ecu will dump in all the fuel it has. i foudn this out when i used a stock maf roubleshooting and also my z32 maf last time at the dyno.

I will look into hardwiring the fuel pump.I did not check the peak voltage on the safc.I wasn't really interested in replacing the maf. I figured that if I could keep the a/f good, then everything will be just fine. But I will go to z32 maf if need be.

i concur as i am in the same boat as what structure described at the moment. if u are running a stock MAF which i am doing also, if u have maxed out ur MAF, u will just start dumping as much fuel as possible. definitely at that power level, ur gonna need an MAF upgrade. whats ur base timing at btw?

Base timing is at 16*.

[crzycav86]

I guess what I want to know is how much can I increase the base pressure without hurting the injectors? What happens when you increase the pressure too much(besides increased chance for leaks)?

[crzycav86]

The graph of the walbro pumps seemed to have stopped working. You can get it to work by right clicking and selecting view picture on it.

[onosqv]

I guess what I want to know is how much can I increase the base pressure without hurting the injectors? What happens when you increase the pressure too much(besides increased chance for leaks)?

NONE, hahaha. You are basically hurting the injectors as soon as you make them flow more than they are suppose to - how long can you get away w/ it? depends on the state of your injectors & your driving, etc.

I believe the JGS guys increased their sohc ka-t project car 370cc to 56 or so psi. 70 psi seems overkill. You're gonna be burning fuel reallllll fast w/ that much psi too.

At the very least I would say get your injectors flowed & cleaned (deatschworks is having a special) - if they have been sitting in an sr rail for a while and the fuel wasn't cleaned out, they could very well be stuck shut (all my ca18det injectors were when I got them).

At least w/ a clean & flow, you would know that your injectors are "like new condition" when you start abusing it.

Would you rather spend 40-60 dollars now cleaning them, or a few days swapping another engine in later?

[crzycav86]

Well I'm just saying it will be 70 psi when the motor is taking in 10 psi of air(the fpr is 1:1). So the base pressure is more like 60 psi.

Anyway, I guess I'll search else where for what I'm looking for.

[KATwo40]

Stock MAF peaks at 240whp -ish. You're about to blow your motor because you want to push your equipment beyond it's limits. Do yourself a favor and patiently collect the parts and pieces you need to reach your power goals efficiently and safely.

[crzycav86]

Thanks for the advice, but a maxima maf is already in the works.