losing power after 4000 rpm

iron bird · Jun 4, 2010

i have a 92 gsx 6 bolt and im stumed on what else to try. First im running 9 psi wastegate routed straight to j pipe. the car runs perfect to 4000 rpm then just no more power. i did a boost leak test and fixed my only leak at the throttle body seals. im running 93 octane gas. everything is stock except for maf translator. compression is 160psi in every cylinder. replacing fuel filter tomorrow any other suggestions?

Sam@RRE · Jun 17, 2010

What turbo are you running? If its a 14B, thats normal.

iron bird · Jun 17, 2010

16g its ebay though

im trying to find a 14b so i dont have this junk one

so i think im on to some thing here. i beileive i have 3 bad maf's, first stock one car runs like crap every where, second stock one car runs like crap down low then pulls like it should, lastly my gm maf runs ok but the cars not pulling as it should. also the car is free of all boost leaks. im trying to find a new gm maf tommarrow.

350war · Jun 18, 2010

You might want to check your wireing going to your MAF. Dont mean to harp about it but you need a data logger. It will save money and a lot of headache. How are you tuning your GM MAF without one?

iron bird · Jun 18, 2010

im getting one i knowwww but im trying to fix it with out it before now its just set to stock injector setting now

also the only reason the gm maf is on is because my car runs like crap with the stock maf i have

1gnew · Jun 18, 2010

Sam@RRE said:
What turbo are you running? If its a 14B, thats normal.

so ## saying that all 14bs quit pulling in high rpms ### i am on this thread for near the same reason i just don't get much pull after 5k but my boost stays constant at 9 psi when in boost even in high rpms :confused:

fran_drivertsi · Jun 18, 2010

You need MORE NOS!!!! NOOOOSSSS!!!!!!!!!

Dsm4lyfe12 · Jun 18, 2010

Seems like a reliable problem in dsm's, check fuel relays/pump.

iron bird · Jun 21, 2010

fixed the tps was bad

350war · Jun 21, 2010

Glad you got it figured out. It should run great with all the work you just put in it.

Sam@RRE · Jun 22, 2010

1gnew said:
so ## saying that all 14bs quit pulling in high rpms ### i am on this thread for near the same reason i just don't get much pull after 5k but my boost stays constant at 9 psi when in boost even in high rpms

It's normal for it to drop off at top. It's a small turbo. Its going past its efficiency range and spinning faster than it should and making more heat than actually pushing oxygen.

bmxmk18 · Aug 6, 2012

This thread is pretty old but im having a similar problem. losing power up top around 4500/5k rpm. Ive done a couple BLT and fixed the leaks, im just wondering what it was, i have a known good coil pack and transistior being shipped to me, because i was thinking weak spark. Also if your running a MAFT any boost leaks before the maft shouldnt affect the way the car runs, air/fuel wise.

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