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Old 03-02-2007, 04:56 AM   #1
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Default Begi 4.2 Fuel Pressure Settings?

Hello!

I have ready installed my BEGI (Bell) 4.2 Turbo Kit. Does anyone here know, how I can set (more or less fuel) my Begi Fuel Pressure Regulator? What are the indicators of enough fuel (brown spark plug?). The Begi System has no control on the exhaust side like AFR or Temperatur?

I want to ride this year (3000 Miles) with the stock engine. Does anyone know a easy and cheap way to set the fuel pressure regulator so, that the engine will run save?

Additionally, I have bougt a new KOYO Radiator and a APEXI AVCR Boostcontroller (to slow down the Boost), for save mode.

Sorry for my bad English, i am from Austria.



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Old 03-02-2007, 09:09 AM   #2
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do this:

first:
You’ll need to connect a fuel pressure gauge on your fuel lines to do this test. $20 at NAPA can get you what you need. Ask the counter clerk that you need a temporary fuel pressure gauge and length of 5/16” fuel hose, they can get you what you need.

Turn your Miata to ON but do not start it. Open the diagnositics box and put a paperclip on F/P and GND. That will run your fuel pump. With a pair of pliers, squeeze the fuel line shut that connects the FPR to the original fuel pressure regulator. When squeezed shut, the pump will be forced to maximum output. Make sure the pressure available is consistent with your intentions. In all cases, the pressure must show, in this idle test, to be about 10 psi higher than the desired fuel pressure, as the available pressure under real load conditions will be less than that measured at idle. This test does not actually prove the pump to be adequate under boost, but if it doesn’t pass this test, it is certainly a waste of time to continue with the same pump.


then:
start the car.

idle should be 35psi. Removing the vacuum line to the OEM FPR should shoot it up. Turn the top screw to tune for 50-55psi when you remove the vacuum line. (make sure to kink the line when you pull it to prevent a vacuum leak)
then:
determine the amount of ful pressure you need to run. Use the math in my DIY FAQ, or go to: http://www.rceng.com/technical.htm
finally:
Now for the fun part....you must have about 4' a fuel line to your gauge. Stick the gauge under your wiper blade and go for a drive. See what your fuel pressure reaches when you boost. You'll turn the small bleeder valve to turn the max fuel pressure.
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Old 03-02-2007, 06:42 PM   #3
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Thank you for your help . At first, i will look for a fuel pressure gauge, then I will try it.
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Old 03-03-2007, 01:06 PM   #4
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Youll need an extra off 6 psi fp /psi of boost pressure.
Say boost is 4psi:

4x6psi =24psi

OEM pressure (40-45 psi)
so 42(average)+24 =66psi

6psi off boost: 42+36=78psi (max oem good fuelpump, if your lucky)
This is why the greddy max out....
Get an walbro 190 hp fuelpump to boost to 8 psi.
Get some sort of timing controller, or at least, turn the ign to 6 degrees....

If you are going to use a boost controller to get less boost pressure it will not work.
The boost pressure is 8psi on those turbo sets and wastgate controlled.
To adjust the boost down you must lenghten the wastegate arm.
Normally there is a bold on it to keep it secure, loosen it ,then release the clip from the wastegate and remove it from the lever. Make it longer skrewing the arm loose.
Adjust to 6psi...
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Old 03-03-2007, 02:44 PM   #5
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The BEGI 4.2 had a Walbro fuel pump as part of the kit. It shouldn't be a problem to get enough fuel pressure, at least for 8 psi.

The limiting factor for that kit was the stock fuel injectors and timing controls. The basic kit had an MSD unit for timing control. Upgrading to a Bipes or J&S is a possibility for better timing control and bigger injectors (even just going to injectors from a 1.8l) will allow more fuel.
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Old 03-03-2007, 03:24 PM   #6
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Quote:
Originally Posted by Braineack View Post
do this:

then:
determine the amount of ful pressure you need to run. Use the math in my DIY FAQ, or go to: http://www.rceng.com/technical.htm
Sorry, but i donīt understand the calculation for the fuel Pressure. Can anyone help me please? My Miata is al od 91 with the 1.6 engine, the stock injectors and the Walbro fuel pump. I want to drive my Turbo Kit with 8 PSI. Are there any experience? Can you help me with the calculation please? Which Fuel pressure to i need? I donīt have any AFR (lamda) or so. At this reason, the exactl fuel pressure is the only way, to run my engine correctly.

Last edited by jonny; 03-03-2007 at 05:06 PM.
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Old 03-04-2007, 12:46 AM   #7
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Quote:
Originally Posted by greddymx5 View Post
Youll need an extra off 6 psi fp /psi of boost pressure.
Say boost is 4psi:

4x6psi =24psi

OEM pressure (40-45 psi)
so 42(average)+24 =66psi

6psi off boost: 42+36=78psi (max oem good fuelpump, if your lucky)
As greddymx5 said, a rule of thumb is to add 6psi of fuel pressure for each psi of boost pressure. Measure your fuel pressure at idle and then add 6psi (fuel pressure) x 8psi (boost) or 48 psi. If your base pressure is 45, you'll be at 93psi at full boost. This is only a rule of thumb and is not necessarily correct for your car. The only way to tell for sure is to have an air-to-fuel ratio meter.

One thing Braineack didn't mention above, the original kit included a fuel pressure gauge and a "T" fitting to go in the fuel line between the fuel rail and the AFPR. The gauge was to be installed temporarily for tuning. There was also a length of high-pressure fuel hose (approximately 1 meter) that went between the "T" and the gauge so you could read the gauge while under boost. The simplest way to see the gauge while driving is to duct tape it to the outside of the windshield while you are doing tuning runs. Once you have the AFPR set correctly, you can either remove the hose and gauge or just stow it in the space where the windshield wiper motor is mounted.
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Old 03-04-2007, 03:25 PM   #8
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Thank you, i will try it!
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Old 03-04-2007, 08:35 PM   #9
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The pump cannot diliver the 93psi...
Get the boost a little bit down...

Ps Try not to move the arm of the wastegate. You can damage the aquator.
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Old 03-04-2007, 10:17 PM   #10
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Actually, BEGI's current instructions, while they recommend tuning with an air-fuel ratio gauge, say to match 8psi boost with 100psi fuel pressure so I'm guessing the pump will make 93psi fuel pressure too.

( http://www.bellengineering.net/PDF/1...System.wpd.pdf)

By the way, Jonny, if you haven't done so already, you can email BEGI for a copy of the full set of directions for your kit. [email protected]
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Old 03-05-2007, 06:43 AM   #11
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The stock pump maxes out on 80 psi....I am sure...
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Old 03-05-2007, 10:32 AM   #12
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braineack explanation FTW!
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Old 03-05-2007, 10:53 AM   #13
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Quote:
Originally Posted by greddymx5 View Post
The stock pump maxes out on 80 psi....I am sure...
I agree but his kit includes an inline Walbro fuel pump to increase the available fuel pressure so that the kit can be run safely at 8psi boost. Actually, sometimes a tired stock pump won't even hold 80 psi.
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Old 03-05-2007, 11:23 AM   #14
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if you tell me what size injectors you are using and what PSI you will be running I can tell you exactly what to set the max fuel pressure to be.
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Old 03-06-2007, 10:32 AM   #15
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Quote:
Originally Posted by cwisenheimer View Post
I agree but his kit includes an inline Walbro fuel pump to increase the available fuel pressure so that the kit can be run safely at 8psi boost. Actually, sometimes a tired stock pump won't even hold 80 psi.
Correction (of my own post): the BEGI 4.2 had a Pierburg inline pump, not a Walbro, which are typically in-tank for Miata applications.
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Old 05-13-2007, 08:02 PM   #16
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I've got a old cast cartech afpr with 1.8 injectors running on 1.6 with 8-8.5lbs of boost. I'm still running the stock fuel pump. So do I need to upgrade to walbro 190 fuel pump to set the fuel pressure right on this car? Also I'm using a fuel hose for the turbo return line does that have anything to do with low oil pressure? Anybody in here using factory radiator running 8-8.5lbs of boost? It starts overheat a little since the temp outside is about 80+. Probably try the redline water wetter first before replacing radiator.

Last edited by supra441979; 05-13-2007 at 08:41 PM.
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