General Questions - Springs, FPR, Wastegate

[Pliskin1]

Geez, I couldn't even think of a catchy name for my thread title. And sorry if this is in the wrong place. My intent is serious.

I have a few random questions. To be clear, I'm not mechanically inclined and have much to learn. Talk to me in laymen terms. I try my best to read and get an education and apply some common sense, but somehow I get the feeling I'm asking dumb questions. Oh well, there's only one way to find out, so here goes:

Fuel Pressure Regulators: Yes I've read threads. I understand that if I replace mine, I need to set it to 43# off vac. Question is why 43#? Wouldn't that result in inadequate fuel pressure at anything above idle (under acceleration) once its back on vac?

Also - and this is to the contrary of my above statement - , if you set it 43#, and I only have 42# injectors, how does/would the pressure exceed the injectors ability of 42#? I suspect that even though I have 42# injectors, that means they are capable of processing at "X #s " while under throttle and boost?

On the subject of the FPR, I have an XP Plus Fuel Pump and Feeder. I'm certainly assuming that's adequate so that when I change the FPR, I can have it set properly (which I know is going to be the 43# mentioned above). But in hindsight, I don't know what the capability of the fuel pump is. Anyone familiar with these?

Valve Springs - My car has stock springs. I believe these were about 80#? The only mods I've done are in my signature. How do I know what springs are acceptable that won't cause any damage? Do I get 80# springs? 100#? I know (think?) lots of guys go with the Comp Cam 980s, but aren't these a rate of 308 #/? What am I missing here?

Wastegate Actuator - Again, I have the original stock one, so its the solid rod. I'm only pushing about 11# of boost under throttle (and I have the separate boost gauge installed so assume its accurate), and therefore on the low side. I'd like to see about 16-17#s for now, which I think is reasonable/safe for my current set up. Maybe its included with the directions when the part shows up, but where do I start with my adjustment on the rod? None at all - and then test drive and make adjustments in small increments? 1/8"? 1/4"? (Its not my exhaust holding back boost, as I've, ahem, temporarily removed the cat for testing purposes).

Go easy, fellas. Thanks.

 

[greeneyegi]

the fuel question,dont confuse boost# and fuel #.
i think the 42 # injectors are per hour or something like that.
the fuel pressure usually drops to about 38# with vacuum,which is the recomended # for our new chips.
if you put pressure on your regulator that makes the pressure go up.1# per pound of boost.
so if your @ 38# at idle and then you ad 20 # of boost .fuel pressure will be 58#.

 

[bison]

You can run any fuel pressure you want but the chip burner will have a recommended base pressure. If you run more or less it will be richer or leaner in open loop and when in closed the ecu will be pulling or adding to reach stoic. Injectors are typically flow rated at 43.5psi. To maintain the flow rating you'd need to increase 1:1 as boost increases (or reduce as vacuum increases) to maintain the same flow rate. Valve spring requirements vary by valvetrain components ramp and rpm. 980 is a god spring to replace stock with but need to be installed at the correct height to work properly

 

[GWHIZZER]

You can run any fuel pressure you want but the chip burner will have a recommended base pressure. If you run more or less it will be richer or leaner in open loop and when in closed the ecu will be pulling or adding to reach stoic. Injectors are typically flow rated at 43.5psi. To maintain the flow rating you'd need to increase 1:1 as boost increases (or reduce as vacuum increases) to maintain the same flow rate. Valve spring requirements vary by valvetrain components ramp and rpm. 980 is a god spring to replace stock with but need to be installed at the correct height to work properly

Ok, the other guys have given you good info, so I'll jump in on the actuator rod.. The stock rod is not adjustable. You'll have to buy an adjustable rod from one of the vendors. When you get it, adjust it out so the end of the rod will slip right on to the pin, without having to pull against the spring. Then one full turn
(shortening the rod) usually equates to one pound of boost. Stock boost was 14.7. Most new chips will allow 16 or so without causing detonation, but you have to be careful. I see in your signature that you have a scanmaster, so just go easy and check for knock (KR). Good luck.

 

[dyermullet]

Fuel pressure is psi pound per square inch. People just refer to it as pound for short. Think of it as the same as air pressure in your tires it is the same units.

Injectors are rated in pound per hour of fuel delivery. That is at a set fixed fuel pressure. If you could out 42 pounds of gas in a bucket as weighed on a scale your injector would flow all of it in an hour.

A functioning fuel pressure regulator will increase your fuel lin pressure 1 psi for every 1psi of manifold pressure. So if you set it with vacuume hose disconnected 43 psi then at 11pound of boost you will have 54psi of duel pressure. It works the opposite when the engine ia drawing a vacuum the regulator will reduce the fuel presure.

Changing the fuel pressure will change the amount of fuel in pounds that the injector will deliver.

The important thing with a force induxion engine is that the fuel pressure rises 1 psi for every 1psi of manifold presure. Leta imagine you forgot to reconnect the vacuum line to your regulator. Then when you have 11 psi in your intake and 43 psi in the fuel rail the effective pressure at your injector would onky be 32 psi. With the manifold reference signal to the regulator it maintains the 43 psi differential.

The regulator has a diaphragm inside that the pressure or vacuum act against which is how the regulator controls. It restricts the extra fuel from returning to the gas tank to raise pressure or it opens and allows extra fuel to return to lower fuel pressure.

 

[Pliskin1]

the fuel question,dont confuse boost# and fuel #.
i think the 42 # injectors are per hour or something like that.
the fuel pressure usually drops to about 38# with vacuum,which is the recomended # for our new chips.
if you put pressure on your regulator that makes the pressure go up.1# per pound of boost.
so if your @ 38# at idle and then you ad 20 # of boost .fuel pressure will be 58#.

OK, that seems to make sense. I certainly wasn't trying to confuse boost # and fuel pressure # (other than I addressed it as 2 different items).

So that means even though I only have 42# injectors, they are capable of sustaining say 58# of fuel pressure (using your example above). And this is on the assumption that my fuel pump can keep up with that, which I believe it can.

 

[Pliskin1]

Ok, the other guys have given you good info, so I'll jump in on the actuator rod.. The stock rod is not adjustable. You'll have to buy an adjustable rod from one of the vendors. When you get it, adjust it out so the end of the rod will slip right on to the pin, without having to pull against the spring. Then one full turn
(shortening the rod) usually equates to one pound of boost. Stock boost was 14.7. Most new chips will allow 16 or so without causing detonation, but you have to be careful. I see in your signature that you have a scanmaster, so just go easy and check for knock (KR). Good luck.

Thanks - very helpful. I do keep an eye on my scanmaster. I'm too cheap to blow up my engine.

I'm actually replacing the whole wastegate actuator, not just the rod (if I follow what your saying). I'm sure that as an original, its possible mine has some minor holes or just can't hold the higher boost levels. When I had the car tuned, I was told that 16-17#s should be OK, but to be concerned over that. So I'd really like to get to that 15-16 mark. Considering I'm at 11 to 12 (on a good day), that's 25+% more boost I could be seeing. And that's 25% more fun I could be having. And 25% quicker I'll be going through tires. And 25% more.... Sorry. Boost makes me giddy.

 

[GWHIZZER]

Thanks - very helpful. I do keep an eye on my scanmaster. I'm too cheap to blow up my engine.

I'm actually replacing the whole wastegate actuator, not just the rod (if I follow what your saying). I'm sure that as an original, its possible mine has some minor holes or just can't hold the higher boost levels. When I had the car tuned, I was told that 16-17#s should be OK, but to be concerned over that. So I'd really like to get to that 15-16 mark. Considering I'm at 11 to 12 (on a good day), that's 25+% more boost I could be seeing. And that's 25% more fun I could be having. And 25% quicker I'll be going through tires. And 25% more.... Sorry. Boost makes me giddy.

I'm sorry to not make that clear- yeah , you have to replace the whole wastegate actuator with one that has an adjustable rod.

 

[Raeban]

Valve Springs - My car has stock springs. I believe these were about 80#? The only mods I've done are in my signature. How do I know what springs are acceptable that won't cause any damage? Do I get 80# springs? 100#? I know (think?) lots of guys go with the Comp Cam 980s, but aren't these a rate of 308 #/? What am I missing here?

And to add a little clarification to the springs, when someone says 80# springs they are referring to the pressure when the valve is closed, otherwise known as the installed height, or seat pressure. This measurement as well as the pressure at max lift are commonly used when selecting the right spring for the application. The rate of 308 is a measurement of how quickly the spring increases pressure in relation to the compression of the spring. As bison mentioned above comp 980s are a good spring but they have to be setup at the correct installed height or they can be as bad as the stock spring when the valve is closed.

 

[Pliskin1]

Thanks again for the help and clarification guys. I really appreciate it.

 

[aminga]

I'm sorry to not make that clear- yeah , you have to replace the whole wastegate actuator with one that has an adjustable rod.

Actually you don't, You can cut the stock rod and thread it with a barrel nut and make it adjustable.

 

[Pliskin1]

Actually you don't, You can cut the stock rod and thread it with a barrel nut and make it adjustable.

Makes sense. I will probably replace my stock one on the basis of "its old", and its not a very expensive part.

For future knowledge, is there a way to test if your wastegate actuator is going bad or losing pressure? Is it simply trial and error of adjusting it then running the vehicle?

 

[Raeban]

Factory test procedure FWIW:

 

[GWHIZZER]

Actually you don't, You can cut the stock rod and thread it with a barrel nut and make it adjustable.

You're right- it's been so long I forgot about that!