Engine Troubles

[AJ]

Originally posted by DSMChick@Jan 21 2004, 09:53 PM
Yeah, if you are venting to the atmosphere, that could be causing your car to die when it's cold out. Venting to the atmosphere isn't recommended under any circumstance and usually makes your car run like crap.

Venting isn't good for his setup, but common on more in depth applications.

[Halon]

with a stock MAS setup, venting will cause problems. If you are using a VPC or a gm maf setup, then you will be able to vent just fine.

[JiN]

i got the word "cure" from a DSM faq.

[Halon]

im sticking with my original responce

for your setup...
bigger fuel pump = no more fuel cut

bigger injectors and some form of fuel control would be a good idea since you are using a larger turbo now, but not 100% necessary if you don't run high psi.
and now im off to bed

[Shane@DBPerformance]

Fuel cut has nothing to do with fuel flow.

You could put in a 1000lph fuel pump and rewire it and it's won't affect fuel cut at all. Putting in bigger injectors or raising the fuel pressure with also not fix fuel cut on their own.

Fuel cut is based purely on the ECU reading to much air flow, it doesn't give a crap about fuel, it has no way to even know if it's running lean at WOT. The ECU is basically just programmed that if it sees over X amount of airflow at X RPM it does fuel cut because it thinks the wastegate has failed. You have to make the ECU see less airflow to keep it from fuel cutting. You can do that by lowering the boost, hacking the MAS, or using an electronic fuel controller to lower the airflow signal Hz getting to the ECU.

[JiN]

See I thought it was all ECU.

I know I know!!!!!! SELL IT!!!! :stick:

[JiN]

Originally posted by Miranda@Jan 22 2004, 03:00 AM
I know I know!!!!!! SELL IT!!!! :stick:

:blink: H8tR! :razz2:

[slowbubblecar]

Originally posted by ecoli@Jan 22 2004, 01:26 AM
Fuel cut has nothing to do with fuel flow.

You could put in a 1000lph fuel pump and rewire it and it's won't affect fuel cut at all. Putting in bigger injectors or raising the fuel pressure with also not fix fuel cut on their own.

Fuel cut is based purely on the ECU reading to much air flow, it doesn't give a crap about fuel, it has no way to even know if it's running lean at WOT. The ECU is basically just programmed that if it sees over X amount of airflow at X RPM it does fuel cut because it thinks the wastegate has failed. You have to make the ECU see less airflow to keep it from fuel cutting. You can do that by lowering the boost, hacking the MAS, or using an electronic fuel controller to lower the airflow signal Hz getting to the ECU.

Finally some correct info! I don't buy into the gm maft stuff much just because of Peter's eperiences. Having to turn boost down to 13 psi (with the gm maft) so I don't hit fuel cut is pointless IMO.

Get 550's and a SAFC to help with fuel cut. If you don't have much money you can hack the mas a bit. You will need a fuel pump in your setup but it will NOT do shit for fuel cut.

If you get larger injectors, you can remove some of the reading from the MAS with teh SAFC. That is how you get away from fuel cut. I am not sure of the exact number on a 2g mas but you would hit fuel cut if you exceeded the mas' rating of 2100 (guessed on #). If your car is overrunning the mas (say getting 2200) you will get fuel cut. That is why a pump will not help you. You need to take away part of the airflow reading with a SAFC or by hacking the mas.

[A//// Guy]

Kid what are you talking about, "buying into the gmaft and 13 psi?" Whats pointless about turning it down so I dont get fuel cut???

Only when its 40 degrees or below CURRENTLY with my 450s and pump gas I cannot go past 12-13 psi becuase I will overrun the injectors. Therefore I will fuel cut.

I have been stating that airflow is what causes the ecu to fuel cut... Not always will the bigger injectors or a bigger pump CURE it. It will help it though, or raise the psi it will cut at.

I run richer with pump gas, I have a safc and I dont like to lean it out too much becuase of knock... Summertime is all candy when it comes to fuel cut cuz its warm out and the air is less dense.

[Shane@DBPerformance]

Originally posted by EclipseTurbo@Jan 22 2004, 11:14 AM
Not always will the bigger injectors or a bigger pump CURE it. It will help it though, or raise the psi it will cut at.

No, it won't help at all, unless you remove airflow signal with a fuel controller. Putting in a bigger fuel pump will not change where it fuel cuts at. The reason why you fuel cut when its colder out is because 14psi when its 75 degrees out is not the same as 14psi when its 30 degrees out. Colder air is denser so when its cold out the ECU sees more airflow at the same boost level than it does when its hot out. Which causes its fuel cut routines to kick in earlier because they are based off airflow not boost psi or running lean.

As far as the MAFT, it uses the same tricks that an AFC does. It is no better nor worse than using an AFC to get around fuel cut, so you need to use larger injectors in conjunction with it for it help fuel cut at all.

[JiN]

How exactly do you hack the MAS?

[Enes]

Originally posted by JiNMaXimus@Jan 22 2004, 01:16 PM
How exactly do you hack the MAS?

definetely not thru ssh

[A//// Guy]

I dont know, differnt threads say differnt things, FAQ says differnt things and when I have posted in the past about fuel cut why did you guys tell me to get 550s? Oh well.

So does the Mas read fuel DC based on airflow or is it real dead time for the injectors? If DC has nothing to do with fuel cut then why when you get up past 100 or so it will fuel cut?

Im confused.

[Shane@DBPerformance]

Originally posted by EclipseTurbo@Jan 22 2004, 12:41 PM
I dont know, differnt threads say differnt things, FAQ says differnt things and when I have posted in the past about fuel cut why did you guys tell me to get 550s? Oh well.

So does the Mas read fuel DC based on airflow or is it real dead time for the injectors? If DC has nothing to do with fuel cut then why when you get up past 100 or so it will fuel cut?

Im confused.

Well, even if it is tied to pulse width (duty cycle is just a logger calculated value from pulse width, rpm, and dead time), pulse width is directly tied to airflow. If you put in a bigger fuel pump, you ECU won't change its duty cycle/pulse width to compensate for more fuel because if has no way of knowing that there is more fueling available.

Here is some info on the fuel cut routine in the ECU's code from a post by Keydiver.

On my flight out to LA
last week, I spent some time looking at the disassembly, and noticed
what I'm pretty sure is the correction being put into the raw
airflow, a 16-bit value, to make the corrected airflow value L0057
for the fuelcut check. The routine takes the raw airflow, multiplies
it times one address, divides it by 128, multiplies it times another
address, and divides by 128 again. I'll bet anything that the one
address is the barometric pressure, where 1 bar (sea level) is 128,
and the other is the intake temperature. I don't have my notes in
front of me now, but it looked very simple.

[AJ]

Originally posted by JiNMaXimus@Jan 22 2004, 12:16 PM
How exactly do you hack the MAS?

honeycombs. No not the cereal.

[Shane@DBPerformance]

Originally posted by JiNMaXimus@Jan 22 2004, 12:16 PM
How exactly do you hack the MAS?

People don't hack the 2G MAS very often. They can handle 3000hz and 450whp stock. You have to start hacking the 1G MAS pretty early on if you want to continue to use it and make any power. It likes to start overrunning when you get close to 2000hz. On a 1G MAS, the first steps are to remove the lower honeycomb and back out the calibration screw. If that isn't enough then you can start removing some of the lower half of the MAS with a dremel. People often at that point also solder a resistor or potientiometer into the intake air temp sensor line to fool the ECU into thinking it's colder outside and adding more fuel to compensate for the added airflow that it won't be reporting to the ECU. You don't want to hack the MAS more than you currently need because you can run into timing/knock problems and it gets hard to tune the more it is hacked. You also never want to remove the main honeycomb, without the main honeycomb it won't meter the air worth a crap.

[JiN]

Personally, im not so sure if it's fuel cut anymore. I think it has to do with my BOV venting to the atmosphere.

[A//// Guy]

Fuel cut feels like the car basicall hits a wall for a second. Your face should almost eat the steering wheel.

I know! Downpayment for a house! :P