Stage III/ 6-Speed going to the Strip

[svxfiles]

Originally Posted by Nemesis Destiny

I should point out that I wasn't being critical, or anything; just trying to help

Thanks.
Desk picture box good now.

[oab_au]

Originally Posted by svxfiles

On my set up I had my adjustable fpr set to 35-36 at idle, and it was going up to 43 under boost, even without the rrfpr, also when I disconected the vac (boost) line to the adj fpr, it now reads 39psi all the time.
And on the wideband, the afr's are MUCH more consistant.
Thanks, Young Tom!

Lernding iz fun!

I see you and Mike are not using the vacuum line from the manifold to the pressure regulator. If the vacuum line is run from the throttle body, or removed, the necessary 36psi across the injector, won't be maintained. This will affect the spray pattern, and the injector output.

If it is removed, the pressure across the injector will vary between, 50psi at idle, to 27 psi at 9 lbs of boost. If it is run off the throttle body, it will idle at 36 psi, and have 27 psi at 9lbs of boost. It should vary from 36 psi at idle to 45 psi on 9 lbs of boost.

To have the injector working as it should, it should have 36 psi across the injector. Thats the difference in pressure in the manifold, and the fuel pressure in the rail. The vacuum line maintains the 36 psi pressure, regardless of manifold pressure.

Harvey.

[svxfiles]

Harvey, with my Walbro 255, and now, with the vacuum line disconnected, i have 40 fuel line pressure when the engine is cold, and 39 psi everywhere else.

Originally Posted by svxfiles

According to the Slow GT fuel pump calculator, all you need for 400 HP is 122.7 LPH if you have a B.S.F.C. or 0.50.
Sorry for the bad picture, but I did not know how else to transfer the #s.
http://www.subaru-svx.net/photos/fil...iles/35220.jpg

Well, I don't know what or how that calculator is calculating, but I can tell you this. An 80lph NA Legacy pump doesn't flow enough fuel for an EJ22T, rated for 160hp/181lb/ft. This is real world experience. So that calculator isn't factoring something in. Or it's using some different variables than what different cars use.

[Phast SVX]

stock pump is making great power for me....

Harvey, i must completely disagree with your statement. Im sorry, maybe you just reversed what you are trying to say?

[oab_au]

Originally Posted by Phast SVX

stock pump is making great power for me....

Harvey, i must completely disagree with your statement. Im sorry, maybe you just reversed what you are trying to say?

Yes Phil I did make a mistake there. The bit " It should vary from 36 psi at idle to 45 psi on 9 lbs of boost. ". Should be 23 psi to 45 psi.

The pressure that the injector injects fuel has to be 36 psi. This is to maintain the right spray pattern, and the right flow rate for the injectors 'on time'. The spray pattern is set for the 36 psi, if it is lower, the fuel will not atomise as well, causing droplets of fuel that do not burn as well. Also the amount of fuel injected for a 10 mil sec 'on time', at 36 psi will be more than, 10 mil sec at 23 psi.

The regulator maintains this pressure, through the vacuum line connected to the inlet manifold. If we connect a pressure gauge to the fuel rail and turn the Ign on the pressure will be 36 psi. This is because the manifold pressure is zero, so the pressure across the injector is 36 psi. Now if we start the engine the manifold pressure will have a -13 psi vacuum in it, so rail pressure will drop to 23 psi. If it did not there would be a 36 psi pressure pushing the fuel in, and -13 psi vacuum pulling it in. This would be a pressure different across the injector of 36 + 13 = 49 psi. To prevent this the regulator uses the manifold vacuum to lower the fuel pressure to 36 - 13 = 23 psi.

So in Toms case, the idle fuel pressure, across the injector, would be about 49 psi, and when it gets to 9 psi of boost the pressure across the injector would drop to 27 psi, instead of 36+9=45 psi. So the amount of fuel injected would be less than it should, for the same injector 'on time', and the spray pattern would not atomise as well.

In Mikes case, it will be OK at idle, but will be too low at full boost, the same as Toms.

Hows that, make more sense?

Harvey.

[SVXRide]

Harvey,
So how can the super/turbocharged SVXi among us address this apparent problem with fuel pressure under boost? If I follow your explanation correctly, the almost "spot on" A/F ratio Phil is seeing under boost does not correlate to an optimum "spray" from the fuel injectors.
-Bill

[oab_au]

Originally Posted by SVXRide

Harvey,
So how can the super/turbocharged SVXi among us address this apparent problem with fuel pressure under boost? If I follow your explanation correctly, the almost "spot on" A/F ratio Phil is seeing under boost does not correlate to an optimum "spray" from the fuel injectors.
-Bill

Don't know what Phil is running Bill, just Tom and Mike both said that they weren't running the vacuum line from the manifold.

Harvey.

[svxfiles]

Harvey, you are who we all go to for answers.
But I am confused.
My fuel pressure stays at 39 psi, give or take 1 psi.
And my air/fuel ratio is between 14.7 or so at idle, to 11.8 at WOT, 9psi boost.
17-18 a/f on coast.
I am not pulling much timing, 4 degrees max, according to the SSM.
And it feels pretty strong.
I ran one 0-60 run today, warm engine, 76f ambiant, and with my built in
G-tech, pulled a 5.07
I will have to check my old notes, but as I remember, that was pretty good.

[svxfiles]

I ran into Dave Clark today, a turbo/NOX fan/mechanic with a strong local following, and he said, all of his buds tune for a 11.7 a/f ratio.
Since most of those guys are Diamond Star/Honda and all run turbos, I would expect them to run richer.
I believe 13 to 1 would be right for an axial vane SC that has an intake manifold temp of 150f.
What do you think?

[SSSVX]

Originally Posted by svxfiles

I ran one 0-60 run today, warm engine, 76f ambiant, and with my built in
G-tech, pulled a 5.07

Tom, 5.07 is goooood.

I felt she pulled stronger on the ride last time compared to the very
first time.

[oab_au]

Originally Posted by svxfiles

Harvey, you are who we all go to for answers.
But I am confused.
My fuel pressure stays at 39 psi, give or take 1 psi.
And my air/fuel ratio is between 14.7 or so at idle, to 11.8 at WOT, 9psi boost.
17-18 a/f on coast.
I am not pulling much timing, 4 degrees max, according to the SSM.
And it feels pretty strong.
I ran one 0-60 run today, warm engine, 76f ambiant, and with my built in
G-tech, pulled a 5.07
I will have to check my old notes, but as I remember, that was pretty good.

Well, yes Tom the fuel pressure will stay at your 39 psi, as it can't be adjusted by manifold pressure, if the vacuum line is not connected.

What was the reasion, that you removed the line in the first place.?

Harvey.

[TomsSVX]

because Tom was trying to figure out why his fuel pressure was jumping while under boost. I told him it was because the manifold pressure was boosting his FPR even without the boost based regulator disks

Tom

[oab_au]

Originally Posted by TomsSVX

because Tom was trying to figure out why his fuel pressure was jumping while under boost. I told him it was because the manifold pressure was boosting his FPR even without the boost based regulator disks

Tom

Yes mate that is what it is suppose to do. If it has problems with the line connected up, then the problems have to be cured some other way.
What reg is he using, give me a link to the type of unit, so I can check it out.

Harvey.

[svxfiles]

The digital fuel pressure gauge on the A-pillar was reading 35-36 psi at idle with the line connected, and up to 43 psi when the rpms came up.
I am ok with that, BUT,
the wideband was showing 20 to 1 to 18-1 at idle and as much as
10.somthing to 1 at 8-9 psi boost.
Since I removed the vacuum/boost line the a/f ratios seem much more stable.
I made a short video of "normal" light throttle driving, followed by a WOT 0-60 run, slightly uphill, with 550#s of people and some bookbags/tools.
The in dash G-tech showed 5.51 btw at 72f.
If I can I'll download the digital film to my locker and post a link.
I left Di's camera cable at work or I'd do it now.
More later.

Oh, the regulator is a Mallory from Summit.
And I don't think they make it anymore.

And Reading is coming!