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Old 04-18-2007, 01:24 AM   #1
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Default Decrease High Fuel Pressure

Hi guys, been wondering why my car has been stuttering and bogging when i get on it recently. I have the 305 supra injectors, emanage, vortech fpr and the walbro 190HP fuel pump.

I measure my fuel pressure today under boost and it is hitting 130 PSI at high boost and the car is running like **** (not to mention the gas gauge practically visually goes lower as your driving in that range!!)

Is there any way to decrease the max fuel pressure on the vortech? I was thinking maybe a bleed valve in the vacuum line or something? Its scary seeing that much fuel pressure.

Anyone else measure max fuel pressure with the walbro 190HP pump?

Thanks
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Old 04-18-2007, 01:25 AM   #2
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You change the disc's out in the vortech to lower your fuel pressure.
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Old 04-18-2007, 03:27 AM   #3
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Well, you can do a couple of things. You can change your 190lph hp to a 190lph gss250 (only runs 90-100psi max).....since you already have bigger injectors and an emange, this is the route I would of gone. Reason being is the vortech takes longer to add fuel with the smaller disc sizes (You may want to see if the GSS250 has adequate flow at that PSI though). The cheapest thing to do is just buy the 4:1 Vortech disc, and tune in or take out any fuel as needed with the emanage. If you fudge for an LC-1 wideband, you can attach the input wire from one of the channels to the tps input on the Emanage, then you can draw back fuel based off of a/f percentages in the airflow map....this kinda works like Olderguys autotune, but will not add fuel, just take away....so it only works on rich setups. I've been using this technique for awhile and works great.
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Old 04-18-2007, 09:22 AM   #4
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14psi x 6:1 + 50psi = 120psi, are you sure you using a 6:1 disc?

FWIW, when using 305s you should be with a 3:1 or 4:1 disc....you can bleed off some pressure, but it's a pita to tune and eaiser to swap out to another disc.

but once you start getting into high boost, you see where engine management becomes key.

but here is something I did: https://www.miataturbo.net/forums/sh...1&postcount=28
If i would have done it again, id of just bought a 3:1 disc and called it a day.
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Old 04-18-2007, 10:06 AM   #5
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I saw that much pressure. Corky says you'll blow the seals at the rail before the injectors will lock... ie, running that much pressure isn't a problem.

I've got the Begi 2025 AFPR and couldn't figure out why I couldn't dial the pressure down below about 100psi even with the adjustment needle backed all the way out. I bought mine used and the PO didn't send me the very small plastic restrictor that Begi sends with their AFPR's that go in the boost line, hence, I didn't know that one existed. Corky said that it gives the thing two ranges, essentially a high and a low. I think I'm running around 100psi now, with 1.8 inj's, and 10-11psi of boost. It feels great, but I don't have any AF's to check. We'll see on the 12th.

I'm not sure I'll see any advantage if I put in the restrictor, step up to the 310's I've got, and dial down the pressure. The restrictor is very small... I almost missed it in the package they sent. Call Steph at Begi and she'll send you one.
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Old 04-18-2007, 10:31 AM   #6
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I couldn't tune it without a restirctor. it would fuel past 100psi with the needle all the way out, with the restrictor i could tune from 50-130psi.
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Old 04-18-2007, 10:44 AM   #7
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I've heard the WD40 "straw" restrictor works just as well.
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Old 04-18-2007, 11:31 AM   #8
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How about removing your vortec? I am currently using a Blue Emanage with 336 cc injectors with no vortec.
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Old 04-18-2007, 11:40 AM   #9
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Quote:
Originally Posted by samnavy View Post
I saw that much pressure. Corky says you'll blow the seals at the rail before the injectors will lock... ie, running that much pressure isn't a problem.
I've been testing injectors trying to get a good solid set of RX7 units to use with my link. I FINALLY found 4 that flowed nearly identical to each other. I've had four sets tested just in the past month or two.

I had two injectors lock at 55psi and at 60psi. So it does happen, especially on older injectors. The guy who does my cleaning says this isn't unusual on injectors that are starting to get weak.

Maybe it doesn't happen on brand new RC injectors, but out of 16 injectors (two different types of RX7 460cc) I had two with this issue. And keep in mind that it wasn't at 130psi or even at 100psi, but at only 5-10psi over what the NA Miata runs at the rail. I would imagine had he tested to 100psi more of the injectors would have failed. That's 12.5%. On the other hand all of the injectors flowed with in a couple of %, even the one that spewed gas throught the body of the injector.

Corky knows a lot, but he isn't an all knowing god.
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Old 04-18-2007, 04:18 PM   #10
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Quote:
Originally Posted by 1991BRG View Post
How about removing your vortec? I am currently using a Blue Emanage with 336 cc injectors with no vortec.
HOw much boost are you running? How do your AFR's look?

@Braineack:

Thanks for that link! Doing some informal testing one day with vortech, i dont believe the rate of rise is linear. I find the vortech eventually just clamps the line after a certain psi. It really is the weakest link in all of our setups around here for people who use the FPR method. I believe Pop VII found the same problem. A perfect rise ratio of 3:1 or 6:1, etc just doesn't happen consistently. However i will try a lower ratio disk as soon as i get one and do some more testing.

The superior solution with the emanage is add an extra injector (of which will be my next project) and get rid of the shitty FPR. Anyone done that here with good results?? Also has anyone got AFR's using the Supra 305 injectors with no FPR up to 15 psi? I would be curious to see when it goes lean as the RCENG calculator is overly conservative.

Regards
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Old 04-18-2007, 04:24 PM   #11
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I always see 115-120psi. every disc I've ever put in I see exactly the fuel pressure I calculate for. With the needle valve I believe I brought it down to 90psi, but it always reacted to the different levels of boost, basically matched the boost gauge.

You could buy my BEGi unit in the for/sale section and get that **** working.
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Old 04-18-2007, 10:30 PM   #12
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Hey Aaron,

I have the 305 Probe injectors and no fpr atm. I went lean at around 9 psi. I'm not convinced that I couldn't have added more fuel though. I was just too lazy to log my injector duty cycles because I'm not planning on running that amount of boost without upping the fuel pressure. My gut tells me they maxed out though.
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Old 04-19-2007, 03:20 AM   #13
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I think max, you can achieve 8psi without a vortech and the highest injector size the blue can handle. I'm surprised no one has done a 5th injector setup like the Fast Forward "E-cool" system uses with the Emanage Blue.
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Old 04-19-2007, 09:16 AM   #14
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Anyone has a idoit install write up for this 5th injector operation?

I would love to take out my VORTECH!
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Old 04-19-2007, 09:45 AM   #15
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...and here i thought of leaving my vortech temporarily in even with a MS install.
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