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major power loss boosting PLZ HELP!!

ninety7gst

Proven Member
101
0
Jul 30, 2003
KansasUS
Well guys, I know that this topic has been beaten to death, but no matter how much I search these threads, I just can't find the answer to my problem.

I bought the car and I didn't give it a good test run (stupid idea) because I was thinking that since the car has a 1G motor in it with a 75k mi warranty then I'm set... Well boy was I wrong.

My mods are as follows, turbo extreme downpipe w/ 02 eliminator, test pipe (no cat), apexi n1 catbact, precesion 50 trim turbo, apexi twin chamber bov, Turbo XS h.p.m.b.c. MBC, walbro 255 lph fuel pump, Jasper bored 6 bolt engine, also it's a '97 GS-T

I decide to gun it on the highway it starts to kick in about 10 or so psi then runs strong to 15... well i changed my mbc to run 20psi, so the boost doesn't kick in till about 10 still and runs strong to 20 then u get a few kicks and such, well I was fine for awhile then I notice that the boost doesn't really kick in till 15 now, then goes to 20 and kicks, once you start to boost at 15 it'll boost all the way till to then surge fast from 10 to 20 while it is kicking. So I pull the - battery cable - off and put it back on, (mistake) because now I floor it and if i get up to about 10 PSI it'll shit out on me, backfire and you hear a whizzing noise in the engine bay. Normal driving, (less than 1/2 throttle, no boost) it's fine. However, when you lay into the throttle is where it starts becoming bad. My gas mileage is crap (~17MPG) which makes me believe I'm running rich. I changed my sparkplugs (NGK) and my fuel filter. I'm going to change the blow-off valve to a GReddy whenever I get the new UPIC pipes in from Dejon Tool. Although I don't believe that is where my problem is...

Thanks for checkin' out my thread and help me please if you have any suggestions...

Oh, and I checked for a boost leak, and I don't have one.
 

ninety7gst

Proven Member
101
0
Jul 30, 2003
KansasUS
I think that maybe my 255 pump is killing my mileage and running the car very rich, so I ordered some 650cc injectors and ECU+ from MachV.com to finetune the fuel maps. (I know, an AFC would have been cheaper for my objective, but I plan to do more than just fuel tuning.) The parts should be in by the end of the month, (ECU+ is on backorder) but I'll keep you posted yet.

If anyone would still have some suggestions, feel free to take a stab at it, even if ur not sure it's right... :cool:
 

suicidal2af

Proven Member
866
18
Jul 31, 2004
Bel Air, Maryland
Bigger injectors are going to make you run richer, until you do some tuning.

If I had to venture a guess, I would probably say that the Walbro 255lph pump is overrunning the stock FPR.

I'd also build a pressure tester and test for boost leaks.
 

SUPERECLIPSE757

Probationary Member
7
0
Jun 14, 2004
Yorktown, Virginia
Yea My Boy Has The Same Problem But He Has A Stock Fuel Pump All He Does When He Goes On Half Throttle Is Make A Backfire Poping Noise Exspecially In 1st Gear But He Went And Got A Standalone Fuel Management System For His Car And It Should Be Here On Friday Hopefully That Fixes His Problem Good Luck With Yours Try Putting Your Stock Fuel Pump Back On And See What Kind Of Affects You Get Try Running Real Low Boost And Also Try Adjusting You Bov Watch The Compresser When You Rev Idle For Boost Leak If It Stays Open To Long Your Leaking
 

ninety7gst

Proven Member
101
0
Jul 30, 2003
KansasUS
Well, I don't have the stock fuel pump so that's not an option, and I have checked for boost leaks by making the boost leak checker, there are none. I talked to the guys at Slowboy Racing and MachV and they said that I wouldn't need an upgraded FPR, because that's what I was initially going to get. They just recommended an AFC...So naturally, I got a piggyback ECU. :p Thanks for the replies though guys, I appreciate it...I'll continue to keep everyone posted incase this same problem is happening to others... :dsm:
 

ninety7gst

Proven Member
101
0
Jul 30, 2003
KansasUS
the parts still haven't been shipped to me... :thumbdown

I got off my cheap ass and went to wally world and got a OBD-II scan tool and hooked her up and pulled PO125 & two counts of PO170. I'm guessing one for the front O2 and one for the rear (my catalytic convertor is removed.) So, I'm going to napa and buying a coolant temp sensor, and if they have the DENSO O2 sensor then I'll buy it from them, if not then I'll just add it to my order on MachV that I'm still waiting for. :cry:

Anywho, maybe this will stop my shyt-poor 17 MPG...LOL
 

ninety7gst

Proven Member
101
0
Jul 30, 2003
KansasUS
This is kinda off topic since my topic was on loosing power, but I checked out my thermostat and ECT sensor to see which was bad from the P0125 code...and I don't even have a thermostat installed...LOL So I'm going back to NAPA and buying a thermostat right after I get off here...maybe that'll fix my warm-up problem. :dsm:
 

ninety7gst

Proven Member
101
0
Jul 30, 2003
KansasUS
solved (for the most part) - when I was getting fuel cut and running rich, I thought that maybe it was the turbo and the fuel pump that made everything go wrong. well turns out the only thing that was wrong w/ it was o2 sensor and it needed big injectors (when above 15 psi...what happened to change me not boosting and whooshing above 10psi was a loose connection on the lower ic pipe...(which I pressurized the intake before and no leaks) so I messed around w/ the piping and I put the clamp back on wrong. I pressurized the system again and found that leak, reapplied the clamp, tightened it and it runs strong. hope this helps everyone out. btw I was POSITIVE that I had no boost leak since I checked it before and found none. but there was one...so always double or triple check, thats the lesson I learned. :dsm:
 
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