Engine Lagging under boost

[BZY247]

My NGK were bought from an automotive shop, so not sure if they would risk getting fake ones in.

However i found my problem today and now car runs beautiful, fuel reg vacum line was running from a solenoid.... i ran a new line to the throttle boddy and wallah perfect. Looks like that solenoid (Not sure why you would use one for a fuel reg) was dead, as it got so bad that anything over 3000rpm the stutter began.

Id advise you check out the same thing on yours.

 

[captainTeeBag]

My NGK were bought from an automotive shop, so not sure if they would risk getting fake ones in.

However i found my problem today and now car runs beautiful, fuel reg vacum line was running from a solenoid.... i ran a new line to the throttle boddy and wallah perfect. Looks like that solenoid (Not sure why you would use one for a fuel reg) was dead, as it got so bad that anything over 3000rpm the stutter began.

Id advise you check out the same thing on yours.

Isn't that Solonoid boost activated? Would make sense cutting return line off over a certain boost to have pressure in the rail then return fuel under vacuum and idle conditions??? Just a theory

 

[captainTeeBag]

If my theory is right???? By doing what you have done could you be running lean under boost at high rpm??

 

[khubner1]

should be fine i have heard that alot of people remove that solenoid anyway

 

[syco_rvr]

might check that on the gf's one too, where abouts have you run the new line though?

 

[khubner1]

most people just bypess the solenoid and plum it in directly to where it took the ffed from originally. ie take out solenoid plumb fpr to where solenoid goes

 

[4piknup]

Forgive me if i am wrong.
i thought the fpr sees atmospheric pressure at idle and cruise. and when on boost the solonoid opens and allows boost pressure to the fpr. this maintains the rail pressure at (58psi or whatever it is ?) above the pressure in the intake. this ensures that fuel still comes out the injectors properly.

If you bypass the solonoid the fpr will see manifold pressure all the time. So at idle instead of the rail pressure being 58psi (or whatever) it will only be 32psi. as flow is proportional to pressure this will result in a roughly 40% decrease in fuel flow. This will be way lean without tuning the ecu.


But, if you can tune your ecu having manifold referenced fpr will help big injectors idle nicer as there is less flow/pressure for them to control.

 

[BZY247]

car was running perfect. . . until next day.
Purchased a new fuel pump, waiting for it to arrive now.


might change plugs tomorrow also

 

[captainTeeBag]

Okay checked this out on some dsm forums etc. the solenoid is there purely to assist with startup under hot conditions and is apparently controlled via ecu and fuel temp and water temp sensors. So the only problem with bypassing this may be issues with startup.if you were to completely remove the solenoid u may get a cel under these conditions as well apparently so if you bypass it leave it wired in. Also jack the whole idea of a fpr is to control the fuel pressure in the rail. It uses a spring to control pressure and is assisted by vacuum \ boost pressure. Under vacuum and idle the vacuum helps open the fpr to return the unwanted fuel back to the tank or filter. Once boost is achieved the Engines fuel requirements increase and therefore more pressure in the rail helps the injectors achieve this. Boost helps the spring in the fpr reduce the amount of fuel being returned. So intake manifold pressure would be a correct reference for the fpr unless of course the is a vacuum or boost leak somewhere

 

[EVOCPE]

I have never used the solenoid, mine just goes from the FPR to the intake manifold

 

[Gianni]

Non turbo cars don't have a regulator coz it works off pure vac. Turbo cars new to solenoid coz it switches over on positive psi to regulate the fuel flow steadier and more efficiently.
If removing the solenoid fixed the problem I'd think the solenoid was playing up causing fuel issue and the splattering on boost. Removing it may have fixed it but I still don't think you are running your car at optimum performance now. Try a new solenoid and see if that fixes things.

 

[brisvr4]

The FPR solenoid is only there for hot restarts. You don't need it and it won't hurt anything leaving it out.

 

[BZY247]

Just informing everyone that after changing plugs also car now runs beautifully again

Note: yet to install the new fuel pump. (Which is still in the mail)

 

[evo-gsr]

I have never used the solenoid, mine just goes from the FPR to the intake manifold

Same here.