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Fuel cut? Or something else?

dsmkid

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Joined
Sep 27, 2011
Messages
61
Location
Denver, Co
/ubbthreads/images/graemlins/dunno.gif Im experiencing what seems to me to be fuel cut but im not 100% sure. any gear pull it will cut and pop a bit at full throttle unless I ease into it. The car is reading max boost @ 14.9psi on the aem truboost. Stock pump, and injectors. The car has been fine and now all of a sudden it is doing this. Mabye boost is up from cooler weather? It has been warmer out but now it is low 60s and this problem occurs. Normally the boost is @ 12psi and no problems.(at higher outdoor temps). I even disconnected the truboost solenoid so the boost would just be at wastegate pressure and it still pulls 13.9psi. weird. mods are:
-2g MAF
-fmic w/ piping
-Evo3 16g
-tial bov
-custom intake
-act 2600
-fidanza lightweight flywheel
-Brian Crower 100 272 cams
-3" turbo back exhaust w/ highflow cat
-aeromotive f.p.r.
-aem truboost and eugo wideband
-S-AFC 1
It just doesnt make sense to me that I would be fuel cutting at less than 14psi even with a stock fuel set-up. I even set the S-AFC to +25% across the board at hi-throttle and the issue still occurs. Keep in mind I have not changed or messed with anything since it was running and pulling perfect. The only thing that has changed is cooler temps outside which seems to have increased the boost a few psi. Thanks in advance!
/ubbthreads/images/graemlins/dunno.gif
 

Okayplayer

Well-known member
Joined
Jan 14, 2010
Messages
255
Location
Denver, CO
I would start with a boost leak test. It's always a good place to start when you are having trouble getting the car to boost properly.
 

Brunoboy

Well-known member
Joined
Apr 25, 2008
Messages
2,880
Location
San Bruno,CA Home of SFO
Quoting dsmkid:
/ubbthreads/images/graemlins/dunno.gif Im experiencing what seems to me to be fuel cut but im not 100% sure. any gear pull it will cut and pop a bit at full throttle unless I ease into it. The car is reading max boost @ 14.9psi on the aem truboost. Stock pump, and injectors. The car has been fine and now all of a sudden it is doing this. Mabye boost is up from cooler weather? It has been warmer out but now it is low 60s and this problem occurs. Normally the boost is @ 12psi and no problems.(at higher outdoor temps). I even disconnected the truboost solenoid so the boost would just be at wastegate pressure and it still pulls 13.9psi. weird. mods are:
-2g MAF
-fmic w/ piping
-Evo3 16g
-tial bov
-custom intake
-act 2600
-fidanza lightweight flywheel
-Brian Crower 100 272 cams
-3" turbo back exhaust w/ highflow cat
-aeromotive f.p.r.
-aem truboost and eugo wideband
-S-AFC 1
It just doesnt make sense to me that I would be fuel cutting at less than 14psi even with a stock fuel set-up. I even set the S-AFC to +25% across the board at hi-throttle and the issue still occurs. Keep in mind I have not changed or messed with anything since it was running and pulling perfect. The only thing that has changed is cooler temps outside which seems to have increased the boost a few psi. Thanks in advance!
/ubbthreads/images/graemlins/dunno.gif


sounds about right, your running a substantially bigger turbo with stock with Cams.Also with that Exhaust, i wouldnt be surprised if your boost is creeping.Also your Venting your bov without proper mods and are you tuning with a logger? get that sorted out as well and come back to the board.
-Shane
 

dsmkid

Well-known member
Joined
Sep 27, 2011
Messages
61
Location
Denver, Co
I do not have a logger atm. I guess possibly a small boost leak would make sense. As far as the bov venting I have been running it like this since I bought the car with no problems at all. This problem just cae up out of nowhere. Ill do a boost leak test and let you know what happens. Ill also be doing a pump and injectors in the very near future.
 

Brunoboy

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Joined
Apr 25, 2008
Messages
2,880
Location
San Bruno,CA Home of SFO
Just because you have no I'll effects doesn't mean it's not doing damage. All I'm saying is do it right the first time. Get a logger as well. How are you adjusting an safc without a logger? And if you said boost is higher than normal on the cold it sounds about right that it would creep and hit fuel cut due to a larger flowing turbo and cams.
-Shane
 

Brunoboy

Well-known member
Joined
Apr 25, 2008
Messages
2,880
Location
San Bruno,CA Home of SFO
you use a pocket logger/ Data logger like a palm handheld to do so through the OBD port. OR you Spring for Ecmlink V3 tuning system.
-shane
 

dsmkid

Well-known member
Joined
Sep 27, 2011
Messages
61
Location
Denver, Co
Quoting adowdell:
not to thread jack but the stock GVR4 ECU can't log correct?



It actually has a non-eprom from a 1g in it. There was something wrong with the stock ecu according to the previous owner. have any links on how to use a logger? can I just grab and use any old palm pilot? what all do I need? I have never used a "logger" before, I have always just tuned with a safc and been good. As far as doing it right the first time I just purchased this car like this and am in the process of getting everything straightened out. Thanks for all the replys and help so-far.
 

Brunoboy

Well-known member
Joined
Apr 25, 2008
Messages
2,880
Location
San Bruno,CA Home of SFO
how do you assume youve given enough fuel? Wide band as well? Heres a link to MMCD logging software and making a harness or you can purchase a harness of ebay somewhere. click
-Shane
 

dsmkid

Well-known member
Joined
Sep 27, 2011
Messages
61
Location
Denver, Co
Quoting brunoboy:
how do you assume youve given enough fuel? Wide band as well? Heres a link to MMCD logging software and making a harness or you can purchase a harness of ebay somewhere. click
-Shane



Yes, AEM Wideband. It is in the green the entire time I am wot. Even while its "fuel cutting"..Or what seems to be. I am actually assuming that a pump and injectors is the main issue here. Just picked up a 255 and just need to find some 750s or so now and ill let you all know what happens.
 

OMFGeofffff

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Joined
May 5, 2006
Messages
867
Location
Burnsville, MN
Definitely need to get a logger before you start messing with your safc. For all you know you could be getting retarded amounts of knock and it's affecting your timing in the upper rpm range. New pump and injectors should help with fuel cut but also check for boost leaks because that will also cause sputtering.

If it was me I would baby it until I had a logger and at least an upgraded fuel pump but I see you have that covered already. IMO tuning and logging are one of my top priority engine related items I purchase on any car I plan to upgrade.
 

dsmkid

Well-known member
Joined
Sep 27, 2011
Messages
61
Location
Denver, Co
Quoting OMFGeofffff:
Definitely need to get a logger before you start messing with your safc. For all you know you could be getting retarded amounts of knock and it's affecting your timing in the upper rpm range. New pump and injectors should help with fuel cut but also check for boost leaks because that will also cause sputtering.

If it was me I would baby it until I had a logger and at least an upgraded fuel pump but I see you have that covered already. IMO tuning and logging are one of my top priority engine related items I purchase on any car I plan to upgrade.



Yes your absolutly right, tuning is a TOP priority. But im still not up to date on logging. What is it exactly and what do I need to do and all the info? Like stated before I have always just tuned with afc's and been good.
 

dsmkid

Well-known member
Joined
Sep 27, 2011
Messages
61
Location
Denver, Co
Quoting OMFGeofffff:
Definitely need to get a logger before you start messing with your safc. For all you know you could be getting retarded amounts of knock and it's affecting your timing in the upper rpm range. New pump and injectors should help with fuel cut but also check for boost leaks because that will also cause sputtering.

If it was me I would baby it until I had a logger and at least an upgraded fuel pump but I see you have that covered already. IMO tuning and logging are one of my top priority engine related items I purchase on any car I plan to upgrade.



Yes your absolutly right, tuning is a TOP priority. But im still not up to date on logging. What is it exactly and what do I need to do and all the info? Like stated before I have always just tuned with afc's and been good.
 

turbowop

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Joined
Apr 29, 2001
Messages
11,971
Location
Yakima, WA
Quoting dsmkid:
I even set the S-AFC to +25% across the board at hi-throttle and the issue still occurs.



Right there is a big problem. Adding that much fuel via an SAFC actually means you're adding 25% airflow to what the ECU sees. Once the ECU sees more airflow than it wants to with the factory eprom, BAM! fuel cut.

I don't think you fully understand exactly what an SAFC does.
 
Last edited:

dsmkid

Well-known member
Joined
Sep 27, 2011
Messages
61
Location
Denver, Co
I was just following vfaq and other forums on what to do with a 2g maf on a 1g car. it is running on a 1g non-eprom ecu atm.
 

turbowop

Well-known member
Joined
Apr 29, 2001
Messages
11,971
Location
Yakima, WA
You have a lot of airflow mods on that car, so even at 14psi it's flowing a LOT more than a stock turbo at 11psi. Adding airflow via the SAFC to trick the ECU into dumping more fuel makes it see even MORE airflow, which is why you're seeing fuelcut. As the ambient airtemps get cooler, you'll start to see fuelcut earlier on the boost gauge.

I get fuelcut on 503 as well since the ECU still has the stock eprom, albeit at a higher boost level since I don't have such a big exhaust.

One way to play around with it is to bump up your base fuel pressure a smidge, then adjust your SAFC accordingly. You won't have to add as much airflow signal on the SAFC, but you'll have to adjust the whole range down to compensate for the higher base fuel pressure.
 
Last edited:

Diego

Well-known member
Joined
Dec 9, 2007
Messages
2,132
Location
In a van down by the river, Iowa
Quoting dsmkid:
Quoting OMFGeofffff:
Definitely need to get a logger before you start messing with your safc. For all you know you could be getting retarded amounts of knock and it's affecting your timing in the upper rpm range. New pump and injectors should help with fuel cut but also check for boost leaks because that will also cause sputtering.

If it was me I would baby it until I had a logger and at least an upgraded fuel pump but I see you have that covered already. IMO tuning and logging are one of my top priority engine related items I purchase on any car I plan to upgrade.



Yes your absolutly right, tuning is a TOP priority. But im still not up to date on logging. What is it exactly and what do I need to do and all the info? Like stated before I have always just tuned with afc's and been good.



Datalogging is just that, logging data that the ECU see's.
You can use ALMOST ANY Palm Pilot, I use a Palm IIIc. I misplaced my hotsync cable so I just ordered a new one but am sure my logs are lost as well as MMCD.

I will reload and redue the parameters to my tuning, but my friend its really simple, you can buy the kit, which comes with a cable to run your Palm and that has squeeze clip that goes right into your ECU (mines not attached to the ECU previous owner did a custom route job thingy). Literally a plug and play device that allows you to see EVERYTHING (within your spec'd parameters THAT YOU CAN SET UP) up to 32 Channels of logging is available, so you can watch and record your O2 and Water Temp, and RPMs and Knock and A/F etc etc etc etc... blah blah blah.

Seems long and complex but really in the end, two words.

It's simple.

Diego
 
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