255lph with stock FPR

[BOOSTJUNKIEGSX]

I know that i am overpowering the stock FPR but i want to know if this is the reason im getting 14mpg and having a stuttering problem. Could my gas mileage improve?

>>FP 16g, 550`s, 255, FMIC, ported manifold/o2, Apexi gt spec DP/exhaust, 20psi<<

Stuttering Symptoms -
1-When the car is being driven on the highway and am in 4th gear around 3000 rpms, if i ride the gear out throught the rpm band not flooring it in the upper rpms and holding it , the car will go into a mode where i could give 100% throttle and the car will not go. Feels like it is running on 2 cylinders. ( like a stuttering when throttled)
2-When the car is boosted through 2nd, 3rd gear to 7000 rpms the car will also sometimes ( not always ) go into RETARD mode in 5th gear.

***The only way to get the car back to normal throttle and running normal is to either put the car into Neutral while driving waiting for the rpms to go down, or by pulling over , sometimes having to shut the car off, and then back on??
AFC
2800 -0
3400 -2
4000 -2
4600 -4
5200 -4
5800 -5
6400 -7
7000 -8
7600 -7
Fuel was added to upper rpms to prevent hitting fuel cut.. im sure in the lower rpms i could lean out a little.

Any suggestions would be appreciated!

 

[1991GSXAWD]

Do you have a logger? You need to log a run and than make your necessary adjustments on the AFC to compensate for the 255lph fuel pump. It sounds to me like you are running rich. Did it start doing this after the fuel pump installation?

 

[awdtalontsi1992]

Correct me if I'm wrong but adding fuel is like adding air. Adding the fuel will make you hit fuel cut quicker. Also it is impossible to properly tune your car if your fuel pressure is bouncing around. There is a reason why everybody says to replace it. Obviously you have some nice mods to your car. I would recommend spending the relatively small amount to fix what could turn into an expensive problem.

 

[BOOSTJUNKIEGSX]

Fuel was added to upper rpms to prevent hitting fuel cut.. im sure in the lower rpms i could lean out a little.

When the afc was at leaner settings it would hit fuel cut thats why i added more fuel

 

[oldman]

1. You can't tune out fpr overrun because the change is a non-linear one, it's load based not rpm based, your tune for one run will not be good for the next run. The solution is an AFPR.

2. SAFC adds fuel by adding air, adding air to add fuel will facilitate fuel cut because fuel cut is triggered by air count, nothing to do with running out of fuel.

3. Your fuel cut is most likely caused by boost leaks.

4. You have no business adjusting the safc without logging capacity or at least basic understanding of how piggyback systems work, zero out the safc then fix your boost leaks properly.

 

[BOOSTJUNKIEGSX]

Thanks.. I am in the process of getting a FPR and i just ordered a logger so i could post back on friday when i recieve it...

The car was tuned to the big 16g, 550`s, 255lph and fulll exhaust with 21psi ( stock intercooler/ piping ) Then was totaled and i rebuilt her over the last year .

Here was the AFC tune then :
2800 -0
3400 -2
4000 -3
4600 -4
5200 -6
5800 -9
6400 -11
7000 -12
7600 -11

I added a greddy FMIC/piping, ported manifold and o2 housing. The AFC log in the FIRST post is for my current mods+and is the only way i could get the car to run strong and pull to redline without hitting fuel cut.. I do know i have a exaust leak between the manifold and turo which i am in the process of fixing.

 

[BOOSTJUNKIEGSX]

Well i listened to your advice and i have no boost leaks and just a exhaust leak *Thanks to SEAFOAM* .. I went back to my settings when the car was tuned on a dyno and i cant get above 4500rpms without sputtering and then hitting fuel cut.. I put it back to the settings that i had, when i was told that i had no idea what i was doing, which were the ones where i added fuel to the AFC and now the car pulls to redline. Ill just have to wait for a log for others to better understand.

 

[oldman]

How exactly did you look for boost leaks?

 

[BOOSTJUNKIEGSX]

I have a 2" adapter peice that i made from home-depo. Using that i put my boost to 15lbs and sprayed the vacuum lines ect with soapy water.. I also found a boost leak where the tube meets to my boost gauge and fixed it along with the others. "Q" The screw on the throttlebody that should be capped off seems to leak a small amount but none that i worried about...along with my hallman MBC the small vent hole which air comes out of. (when screwed in doesnt leak).. Thats the process and i also took my intake off and tested that for leaks aswell.. Any hints

 

[97GsXfreak]

Maybe try some new plugs in there and check to see if your plug wires aren't arching....just some suggestions. If you want I could come over with a logger friday and help you out...let me know

 

[oldman]

Would that be 15psi shown on your boost gauge during the leak test or is that what you set the air compressor gauge to? If so, how long did it hold the 15psi before it bled down to zero? In any case, how can you be satified with 15psi when you're boosting 20psi? And no, the BISS o-ring is not a small leak and you probably have more once you're able to reach 20psi so your leak test isn't complete.

Further more, is your mas hacked? There is just no way you should have positive adjustment on the AFC for 550cc, something is wrong.

Lastly,

Stuttering Symptoms -
1-When the car is being driven on the highway and am in 4th gear around 3000 rpms, if i ride the gear out throught the rpm band not flooring it in the upper rpms and holding it , the car will go into a mode where i could give 100% throttle and the car will not go. Feels like it is running on 2 cylinders. ( like a stuttering when throttled)
2-When the car is boosted through 2nd, 3rd gear to 7000 rpms the car will also sometimes ( not always ) go into RETARD mode in 5th gear.

If this is what you mean by fuel cut, you're not hitting fuel cut, sounds more like knock/timing retard.

 

[BOOSTJUNKIEGSX]

No..The sputtering problem is totally different and my mas is stock 2g. Also the gauge was not the compressor. I may be a newbee but i do have some sense. With the sputtering i can boost like it says and with the fuel cut i cannot get above 4500 rpms with my afc set to the tuned method. With the method of adding fuel to the afc like i have done, i can then boost without hitting fuel cut( like hitting a wall)!.The boost seaped out very quickly and now that i fixed the leaks it takes forever to go away and seems to stay at 5lbs for awhile before fully clearing. I do have an bad exhaust leak which may be the culprit (manifold to turbo) and who is to say i dont have a boost leak under a load.? dont know..

 

[oldman]

First, I would re-test to 20psi and fix all leaks no matter how big or small. I can pressurize my intake up to 25psi with a BOV leak at 18psi, it than holds 14psi for a long time, you definitely have alot of room for improvement.

I suspect that you're running rich due to leaks at 15+psi, lack of afpr and wrong compensation for the 550s, hence the bogging then hit fuel cut due to boost leaks after 15psi facilitated by your positive adjustments on the afc. The quicker you get the logger on, the better.

 

[BOOSTJUNKIEGSX]

Thanks for your help, its appreciated.. I will do more boostleak tests tomm at 25psi and post a log on friday of what she looks like. I deff have room for improvement and im sure she will be ready to put out some decent numbers on the 4th. Maybe ill see ya there?

 

[oldman]

Thanks for your help, its appreciated.. I will do more boostleak tests tomm at 25psi and post a log on friday of what she looks like. I deff have room for improvement and im sure she will be ready to put out some decent numbers on the 4th. Maybe ill see ya there?

No problem. As for the 4th, I still have to tie up some loose ends before I do my first ever run , hopefully I will get it ready before then.