Evo fuel pressure at fuel rail...
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Evo fuel pressure at fuel rail...
What is our evo's system fuel pressure at the fuel rail? I'm trying to plug in all the values in this cool Injector size worksheet:
http://www.rceng.com/technical.htm#WORKSHEET
http://www.rceng.com/technical.htm#WORKSHEET
Last edited by Smogrunner; May 27, 2005 at 10:34 PM.
Base pressure is 43.5psi (no vac applied to the regulator). Actual idle pressure will vary depending on the ammount of vacuum your motor produces.
To figure your fuel pressure under boosted conditions add your boost pressure to the base fuel pressure. That is assuming your fuel system is operating propperly and you have a 1:1 increase in fuel pressure compared to boost.
To figure your fuel pressure under boosted conditions add your boost pressure to the base fuel pressure. That is assuming your fuel system is operating propperly and you have a 1:1 increase in fuel pressure compared to boost.
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Could someone with a fuel pressure gauge confirm this? At 20psi we should see around 63psi of fuel pressure, right. I have seen conflicting information on this. On Socalevo, it was said that the fuel pressure remains constant at about 43psi.
then that's one messed up car 
The car has a 1:1 RRFPR - it's base pressure at idle with the vacuum line connected is in the 33-36 ish range as I recall. With the vacuum line off its 43 ish. From there, it rises 1 psi for every psi of positive manifold pressure (boost) it sees. So at 20 psi, its 63, and 30 psi its 73, etc/ Now, throw a fuel pump into the mix without an adjustable fpr, and this can skew things somewhat, as your base pressure can rise - however on an Evo, it does not tend to go through the roof, so things stay pretty much consistent. This rise is due to the stock fpr not being able to bypass all the extra fuel its not seeing from the bigger flowing pump. So if your base pressure rises to, say, 46 psi, then at 20 psi, fpr should be 66 psi, and so on
The car has a 1:1 RRFPR - it's base pressure at idle with the vacuum line connected is in the 33-36 ish range as I recall. With the vacuum line off its 43 ish. From there, it rises 1 psi for every psi of positive manifold pressure (boost) it sees. So at 20 psi, its 63, and 30 psi its 73, etc/ Now, throw a fuel pump into the mix without an adjustable fpr, and this can skew things somewhat, as your base pressure can rise - however on an Evo, it does not tend to go through the roof, so things stay pretty much consistent. This rise is due to the stock fpr not being able to bypass all the extra fuel its not seeing from the bigger flowing pump. So if your base pressure rises to, say, 46 psi, then at 20 psi, fpr should be 66 psi, and so on
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From: Inland Empire, CA
Originally Posted by Z1 Performance
then that's one messed up car
The car has a 1:1 RRFPR - it's base pressure at idle with the vacuum line connected is in the 33-36 ish range as I recall. With the vacuum line off its 43 ish. From there, it rises 1 psi for every psi of positive manifold pressure (boost) it sees. So at 20 psi, its 63, and 30 psi its 73, etc/ Now, throw a fuel pump into the mix without an adjustable fpr, and this can skew things somewhat, as your base pressure can rise - however on an Evo, it does not tend to go through the roof, so things stay pretty much consistent. This rise is due to the stock fpr not being able to bypass all the extra fuel its not seeing from the bigger flowing pump. So if your base pressure rises to, say, 46 psi, then at 20 psi, fpr should be 66 psi, and so on
The car has a 1:1 RRFPR - it's base pressure at idle with the vacuum line connected is in the 33-36 ish range as I recall. With the vacuum line off its 43 ish. From there, it rises 1 psi for every psi of positive manifold pressure (boost) it sees. So at 20 psi, its 63, and 30 psi its 73, etc/ Now, throw a fuel pump into the mix without an adjustable fpr, and this can skew things somewhat, as your base pressure can rise - however on an Evo, it does not tend to go through the roof, so things stay pretty much consistent. This rise is due to the stock fpr not being able to bypass all the extra fuel its not seeing from the bigger flowing pump. So if your base pressure rises to, say, 46 psi, then at 20 psi, fpr should be 66 psi, and so on
Thanks Adam, you rock.
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For that worksheet:
Crank HP is going to be close to what one expect to see recorded as whp on a Dynojet dyno + maybe 10% or less.
Brake Specific Fuel Consumption will be around 0.55
Most injectors are rated at 85-90% duty cycle, so 0.9 is a safe number.
System Fuel Pressure is 43psi + expected boost pressure (as Adam illustrated).
This will get you reasonable figures.
Crank HP is going to be close to what one expect to see recorded as whp on a Dynojet dyno + maybe 10% or less.
Brake Specific Fuel Consumption will be around 0.55
Most injectors are rated at 85-90% duty cycle, so 0.9 is a safe number.
System Fuel Pressure is 43psi + expected boost pressure (as Adam illustrated).
This will get you reasonable figures.
Originally Posted by Smogrunner
Dang Ted, I owe you a beer too. I'm thinking 880's for my setup will be perfect. Now, which 880s?
Originally Posted by Smogrunner
Could someone with a fuel pressure gauge confirm this? At 20psi we should see around 63psi of fuel pressure, right. I have seen conflicting information on this. On Socalevo, it was said that the fuel pressure remains constant at about 43psi.
The value you need to plug into the injector size program is the base pressure with no vacuum/boost signal.
Keith
