Attn: Mike or JC or any one that can help
01-30-2009, 10:11 AM
#31
VIP Member
Join Date: Jul 2004
Posts: 1,538
Car Info: AKA Sigma Pi (Co-Driver)
yes thats one way to set fuel cut....
OK Boost creep....
ECU is set for 14lbs, Wastegate spring needs to be set to 18psi + vac assist so it's roughly 20-22psi.
Boost hits 14 then 13, 13 then 14, 15, 16, etc....
this situation the problem is Wastegate it's not keeping the flapper door shut.
1. Wastegate is too whimpy
2. Boost Valve/Regulator hit it's 5V max and it can't bypass any more vac from the charge intake side to assist the wastegate due to valve limitation, vac line limitation etc...
3. when the valve hits static it sends a signal to the ECU saying hey i am stressed and need help so it does timing or fuel cut depending how the ECU is programmed.
other situation...
Boost hits 14psi then 13, 15, 12, 18, 13, 20...
every thing listed above with the ecu trying to stabilize and correct.
Ecu is simulating timing cut and fuel at the same time. when it cuts off boost goes down then cuts back on spikes up.... again wastegate is defective or the wastegate regulator is slow to react caused by goop or just normal electronic wear.
now what causes fuel cut?
depends on what type of sensors the car has and any one of them can cause it.
The simplest way to understand in relation to boost creep is this...
Sesnros we are dealing with.
1. Boost pressure regulator valve aka Boost valve aka frequency valve.
2. MAP or MAF sensor or both
3. Knock Sensor
If any one of these sensors hit static 5 volts it will do a cut of something like fule or ignition.
If your over boosting and the frequency valve is static @ 5 and it won't cut off but the MAF is reading 100000g/s when @ 5 volts on the frequency valve = 610g/s it will do a cut.
Knock sensor will also simulate a cut for ignition if it's tied into the system.
Euro cars simulate a 3 stage cut...
Throttle body first, then ignition, then fuel... (it's like this so it feels smooth you will just notice a slight lost of power)
Jpn Cars up to 2006
Fuel then Ignitoin which is very harsh and abrupt.. you hit fuel cut car falls on it's face drivers head hits steering wheel. you hit ignition cut it feels like the motor shut off with rapid fire....
there are more variables involved but this is probably the simplest way to explain it in my head.
OK Boost creep....
ECU is set for 14lbs, Wastegate spring needs to be set to 18psi + vac assist so it's roughly 20-22psi.
Boost hits 14 then 13, 13 then 14, 15, 16, etc....
this situation the problem is Wastegate it's not keeping the flapper door shut.
1. Wastegate is too whimpy
2. Boost Valve/Regulator hit it's 5V max and it can't bypass any more vac from the charge intake side to assist the wastegate due to valve limitation, vac line limitation etc...
3. when the valve hits static it sends a signal to the ECU saying hey i am stressed and need help so it does timing or fuel cut depending how the ECU is programmed.
other situation...
Boost hits 14psi then 13, 15, 12, 18, 13, 20...
every thing listed above with the ecu trying to stabilize and correct.
Ecu is simulating timing cut and fuel at the same time. when it cuts off boost goes down then cuts back on spikes up.... again wastegate is defective or the wastegate regulator is slow to react caused by goop or just normal electronic wear.
now what causes fuel cut?
depends on what type of sensors the car has and any one of them can cause it.
The simplest way to understand in relation to boost creep is this...
Sesnros we are dealing with.
1. Boost pressure regulator valve aka Boost valve aka frequency valve.
2. MAP or MAF sensor or both
3. Knock Sensor
If any one of these sensors hit static 5 volts it will do a cut of something like fule or ignition.
If your over boosting and the frequency valve is static @ 5 and it won't cut off but the MAF is reading 100000g/s when @ 5 volts on the frequency valve = 610g/s it will do a cut.
Knock sensor will also simulate a cut for ignition if it's tied into the system.
Euro cars simulate a 3 stage cut...
Throttle body first, then ignition, then fuel... (it's like this so it feels smooth you will just notice a slight lost of power)
Jpn Cars up to 2006
Fuel then Ignitoin which is very harsh and abrupt.. you hit fuel cut car falls on it's face drivers head hits steering wheel. you hit ignition cut it feels like the motor shut off with rapid fire....
there are more variables involved but this is probably the simplest way to explain it in my head.
01-30-2009, 10:16 AM
#32
VIP Member
Join Date: Jul 2004
Posts: 1,538
Car Info: AKA Sigma Pi (Co-Driver)
Internal Wastegate
1. Turbo is too small and why the hell are you over boosting it way above the trubo's efficeincy range....
2. Waste gate port is too small some noobs actually port this thing out wasting money to prevent the creep RETARDS!!! that don't work
External Wastegate:
1. Your pipe is too small and your wastegate is too small.
BTW bypass valves, blow off vavles, and hybrid valves cause boost creep... so that can also be a problem and should be the first thing to check.
01-30-2009, 10:19 AM
#33
VIP Member
Join Date: Jul 2004
Posts: 1,538
Car Info: AKA Sigma Pi (Co-Driver)
Yes a fully open WG in theory can still generate enough engine pressure to cause boost to rise or at least hold....
it's very very hard to simulate... you have to calculate the speed of air entering vs the speed of air exiting. also the speed and ratio of both the cold side and hot side wheel. because depending on how agressive the wheel can be on the cold side and how fast it needs to spin to make 1 charge pressure can cause a boosting situation with an open WG.
OK i am done with this topic...
Lawson Install the exhaust dp and
if something happens u gots my number
01-30-2009, 11:28 AM
#37
good lord that is a lot of info. thanks JC hehe
i ran with no tune on my prodrive dp and a STI uppipe for like forever (until i gave it to you lawson). it threw a CEL but that was about it.
i ran with no tune on my prodrive dp and a STI uppipe for like forever (until i gave it to you lawson). it threw a CEL but that was about it.
01-30-2009, 09:47 PM
#38
VIP Member
Join Date: Aug 2003
Location: running track
Posts: 3,018
Car Info: 2004 Wagon
Lawson ok this is what i can tell you from all the BS years i had with installing and testing exhaust kits, with or with out cats, down pipes, divorced etc...
Blah blah bs...
You don't need an ECU reflash thats total BS!! and it's a money gimmick i have used it in the past but the fact is your going to gain what you will.
If you do an ECU reflash the exhaust will help you get more power because it will complement the timing advance, added boost, and other changes made to the ecu. Just by adding an exhaust you will gain 3-5% overall hp.
With that said... Eff the ECU reflash...
Get that exhaust toss it in the car and check for changes... you will notice the following things...
1. Less back pressure (you will feel like the car has less kick down low)
2. Free reving motor up top mid to up top.
3. Turbo spool will be louder and recovers boost much quicker on shifts.
4. i hope it's lighter than stock
5. Devorced wastegate helps reduce turbulance in the exhaust which is good for 1% of power gains if any.
People say that an exhaust helps the turbo spool up faster thats 50% BS! on a stand still an open exhaust will not do squat for you because there is no pressure, or air velocity in the system the trubo relies on the exhaust gast to get the blades spinning then it's starts to generate velocity in the exhaust side. So from a stand still YOUR TURBO WILL NOT SPOOK ANY FASTER! it will spool faster during shifts going into preboost then boost, thats one of the biggest benefits of the system.
Boost creep.... no such thing!!! unless your wastegate is sooo clogged with carbon that the flapper door does not shut in time. You will not get or notice any boost creep but if your doing 20+ lbs of boost and the stock wastegate is only rated for 8lbs spring tension 14lbs spring + Vac then you will have boost creep. in your case YOU WON'T and if you do it's simple to fix.
Blah blah bs...
You don't need an ECU reflash thats total BS!! and it's a money gimmick i have used it in the past but the fact is your going to gain what you will.
If you do an ECU reflash the exhaust will help you get more power because it will complement the timing advance, added boost, and other changes made to the ecu. Just by adding an exhaust you will gain 3-5% overall hp.
With that said... Eff the ECU reflash...
Get that exhaust toss it in the car and check for changes... you will notice the following things...
1. Less back pressure (you will feel like the car has less kick down low)
2. Free reving motor up top mid to up top.
3. Turbo spool will be louder and recovers boost much quicker on shifts.
4. i hope it's lighter than stock
5. Devorced wastegate helps reduce turbulance in the exhaust which is good for 1% of power gains if any.
People say that an exhaust helps the turbo spool up faster thats 50% BS! on a stand still an open exhaust will not do squat for you because there is no pressure, or air velocity in the system the trubo relies on the exhaust gast to get the blades spinning then it's starts to generate velocity in the exhaust side. So from a stand still YOUR TURBO WILL NOT SPOOK ANY FASTER! it will spool faster during shifts going into preboost then boost, thats one of the biggest benefits of the system.
Boost creep.... no such thing!!! unless your wastegate is sooo clogged with carbon that the flapper door does not shut in time. You will not get or notice any boost creep but if your doing 20+ lbs of boost and the stock wastegate is only rated for 8lbs spring tension 14lbs spring + Vac then you will have boost creep. in your case YOU WON'T and if you do it's simple to fix.
