Snowsurfer03

12:1 comes with the kit right?

I am running really rich, so rich that everything bogs down at WOT.
My question is would a 10:1 Vortech Recalibration Disk do the trick?
OR sould I get the 8:1 & 10:1 and see what works best?

Braineack

iTrader: (62)

with your pump you'll probably want to go as far as a 8:1 disc. Speaking of I need to pick one up soon. Or you can spend the $5-10 extra bucks and get the complete set of discs and see what works best.

Snowsurfer03

thanks!

olderguy

iTrader: (19)

Does anybody have the specs on JR Pump?

street mod two

I believe the JR pump is just a re-badged walbro. The big question is which walbro. With the 255 walbro I could not get the base pressure down enough to keep the car from running pig rich. With the 190hp walbro my fuel pressure is perfect. FWIW, I'm using a BEGI AFPR, not the vortech.

olderguy

iTrader: (19)

I use a 10:1 as an emergency setup when I bypass the Emanage and turn down the boost. 8:1 runs a little lean in spots. I am running the 1.8's. What boost level are you running?

brgracer

iTrader: (14)

See the link:

http://forum.miata.net/vb/showthread.php?t=20858

olderguy

iTrader: (19)

Based on that discussion, seems it is supposed to be the 255 HP, which would probably be OK with an 8:1 disc.

Snowsurfer03

Hummm okay? So it's a 255. I am running 8psi right now because at 9-10psi it boogs down because its too rich.

Soo 8:1? Anybody got one they want to sell me?

MiataNuTca

8:1 with a 255 at 8psi is gonna fry your injectors. I was on the limit with the 8:1 when I was running 7psi. As soon as I upped my boost to 8psi, one of my injectors failed closed (leaned out one cylinder). My fuel was 100+ psi with the Pierburg and the 8:1 disk (I have a fuel pressure guage with sender). I would go for the 6:1 disk until you can muster some cash for an emanage and some injectors, or go with an adjustable Begi FPR.

Snowsurfer03

What in the world?

I have 1.8 injectors.

Older guy....help me out. Isn't 6:1 going to run way to lean?


Should I just give up and get a BEGi AFPR?

drftem

i have a slightly used 8:1 disk.

olderguy

iTrader: (19)

I would go for the 8:1 and install a fuel pressure gauge. Stop cranking up your boost when you get to 100psi(of fuel).

Snowsurfer03

thanks!

drftem - PM sent!

Braineack

iTrader: (62)

Ok from what I understand -

To calculate your needed fuel:

PR²x(idle_psi) + Boost = Fuel Needed

PR= 14.7 (atm. pressure) + boost / 14.7

So lets calculate 9psi

9psi = 1.61 PR

(1.61*1.61)x36+9=101.7psi of fuel needed


To calculate to amout of fuel given by your FMU:

Ratio x boost + idle_psi = Fuel Pressure

9psi with a 12:1 on the stock pump would supply
12 x 9 + 36 = 144psi about 30 more psi than required

so

9psi with a 8:1 disc would be
8 x 9 + 36 = 108 psi - 6 more psi than required, Corky recommends around 10, so this is close.

Checking Pump Pressures:
If you do this test you should be able to see how much boost you can safely run.

As far as figuring at when the injectors reach 85-90% duty and what the oem fuel pump can deliver is where I'm stuck. And make sure you calculate using your base idle pressure, I'm sure the 255 lb/h idles with more base pressure.

jayc72

iTrader: (14)

With these calculations there is no mention of injectors. I would think that 25cc more per injector (about 12% larger) would change the amount of fuel pressure needed at specific level of boost.

Would 1.8 injectors @ 90PSI be the same as 1.6 injectors @ 100PSI?

Or I'm I talking out of my ***?

Braineack

iTrader: (62)

From what I understand injectors just supply the fuel and can reach 100% duty cycle. You want them to run at 80% or so. But if they can only flow to a certain point. So 90psi of fuel on 1.8 injectors would be 90psi of fuel on 1.6 injectors. The reason you go to larger injectors is to supply more fuel for the higher boost levels. Where 1.6 injecotrs could supply enough fuel for 5-6psi 1.8 injectors can supply enough fuel for 7-8psi....I'm still trying to read and learn more about fueling, but so far this is what I understand.

jayc72

iTrader: (14)

Are you saying that at 100PSI the 1.6 and the 1.8 are flowing the same amount of fuel?

When I said:
I meant flow the same amount of fuel. At least that would be my assumption given that at the same fuel pressure a 1.8 injector will support higher boost levels than a 1.6 injector.

I wasn't saying that changing from a 1.6 injector to a 1.8 injector would lower fuel pressure.

I think we are saying the same thing

Going back to my original point. Which injector is being used with the calculation you posted? I assume that it is stock injectors on a stock motor, and that it is a pretty safe calculation, even more so if the injectors are larger.

Jay

olderguy

iTrader: (19)

Let us not forget that we do not have a fuel management computer added here, so the injector duty cycle will not be increased over what is in the open loop maps in the ECU. We are relying on larger injectors flowing more and higher pressures causing more flow through those injectors.

8:1 disc in my setup is just a little lean in some spots and rich in others when I bypass the Emanage. I'm running a 190lph HP. With the slightly larger pump I would expect the 8:1 disc will compensate for the lean spots based on a higher flow at specific pressures.

If it's too rich, I have a 7:1 disc available

Braineack

iTrader: (62)

Exactly why I spent the extra few bucks and bought the full set of calibration discs. I got the calculations from Corky Bell and I'm trying my best to understand it all.