Timing help
05-31-11, 05:05 PM
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Timing help
Hey all I'm new to turboing rx7 my question is do you need to advance the timing of the leading and trailing? If so can someone give me an idea of how and how much. Here is my setup
Stock ported 12a
Carb prepped for boost by rotaryshak
Holly blue pressure regulator
Mallory 3 port boot refrence regulator
Walboro 255
My boost controller is set to 15 pounds and I'm running a t25 turbo out of an eclipse. Any help would be appreciated.
Stock ported 12a
Carb prepped for boost by rotaryshak
Holly blue pressure regulator
Mallory 3 port boot refrence regulator
Walboro 255
My boost controller is set to 15 pounds and I'm running a t25 turbo out of an eclipse. Any help would be appreciated.
06-02-11, 07:15 AM
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yes i had too because the walboro was pushing out too much pessue fo my boost reference regulatory to handle and we had a holly blue regulatory lying around the shop so that brought it down to 12 and then the mallory 3port has it down to 5 at idle which is fine but when i get into boost it only brings it up to about 8 or so
06-02-11, 10:20 AM
#6
The mallory regulator. Is enough for the set up. U have it set up wrong. The pressure coming in to the regulator should be high like the fuel injection pump and the regulator has to have the right spring so u can adjusted to either 7-9 psi The rest of the pressure it bypasses the regulator and is returned back to the tank.
06-02-11, 10:25 AM
#7
Well there's not a whole lot you can do besides lock the distributor or switching to an electronic spark advance/EFI system. Locking the distributor means eliminating vacuum and centrifugal advance so timing is fixed--like a lawn mower or something. That's not exactly ideal for a street car although it is done often enough. On the FC and later engines the timing is completely controlled by a computer instead of by actual vacuum or centrifugal weights. Therefore it works much better on a boosted application because the basic timing calculation is based on rpm & measured airflow (FC) or rpm & manifold pressure (FD).
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06-02-11, 02:10 PM
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The mallory regulator. Is enough for the set up. U have it set up wrong. The pressure coming in to the regulator should be high like the fuel injection pump and the regulator has to have the right spring so u can adjusted to either 7-9 psi The rest of the pressure it bypasses the regulator and is returned back to
the tank.
the tank.
06-03-11, 01:56 AM
#9
U just need the Mallory , the fuel pressure set to the carb u are running. 5-9 psi. , as u build boost the regulator will send the extra fuel pressure , let's say u are running 15 psi of boost and u have your carb set up to 5 psi. The regulator will be sending 20 psi to your carb at full boost. Make sure u are running a return fuel line. And a hose hooked to the port on the regulator and connected to a boost source . Plus u should run a gauge where u can actually see your fuel pressure rising as your boost goes up
06-03-11, 02:55 AM
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Base fuel pressure for a Nikki carb should be 3-4 PSI. So at 15 PSI boost pressure, you'd be at 18-19 PSI fuel pressure. If you're having trouble keeping your idle fuel pressure down, you may need a larger return line. Don't use a second regulator.
As for the timing, I have my distributor locked at 10 degrees with a 10 degree split. Hardly ideal, but it works alright.
As for the timing, I have my distributor locked at 10 degrees with a 10 degree split. Hardly ideal, but it works alright.
06-03-11, 07:20 AM
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Base fuel pressure for a Nikki carb should be 3-4 PSI. So at 15 PSI boost pressure, you'd be at 18-19 PSI fuel pressure. If you're having trouble keeping your idle fuel pressure down, you may need a larger return line. Don't use a second regulator.
As for the timing, I have my distributor locked at 10 degrees with a 10 degree split. Hardly ideal, but it works alright.
As for the timing, I have my distributor locked at 10 degrees with a 10 degree split. Hardly ideal, but it works alright.
06-03-11, 01:44 PM
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I used a 5/16" return line from a GSL-SE which reduces to 1/4" to go back into the tank. The rollover check valve thing has been removed. With this setup, I can reduce my MSD fuel pump to as low as 1 PSI. I do not know if the stock return line would be big enough as I never tried it. Nor do I know whether my setup would be good enough for the higher-flowing Walbro pump.
06-05-11, 04:33 PM
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So I ran a bigger return line which helped immensely and I an now running only my Mallory regulator. We were having problems getting it to idle so I advanced my timing and it does idle but y new problem is when you get into boost it feels like it is bogging and not accepting boost. Too much fuel or is my timing off?
06-06-11, 07:25 AM
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i wasnt sure what to bump the timing to so i moved the leading up about two degrees and left the trailing the same. i haven't played with timing so i didn't do alot.
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