hesitates bad at 8-12 psi

casperfast · 05-09-2008, 08:21 PM

ok, i just did my fuel pump rewire and i went from 12.9 to 13.88 V+ at the pump. i took it for a drive to test it out. with my boost controller knob swrewed all the way in (max boost) it would hit over 20 quickly, i could control it to say 15-17 with the foot though so i did, ran awsome. i turned my boost down......and it would max at 15 psi but it would hesitate bad at 8-12 psi and spool verry slow. i turned it back up no problem, just too high of boost. i wasnt getting fuel cut at 20 even.

mods:
-pump rewire...duh
- fmic
- 14b turbo
- manual boost controller (cheapy brass w/ red knob & bleeder hole on side)
- 2.5 in stainless intercooler piping
- 1st gen crushed BOV

whats going on?

booostedGSX · 05-09-2008, 08:25 PM

Try a boost leak test.

dsm-onster · 05-09-2008, 08:29 PM

Acan I geta AMEN!

casperfast · 05-09-2008, 08:30 PM

can a boost leak actually cause it to take a $shit when tirned down but not up? it will pull any gear HARD(REALLY HARD) at 20 psi but when i have my sontroller turned down it dumps at 8-10 i dont get it. i dont have a boost leak tester, im making one this weekend. but i checked all my fittings and coupplers. the first thing i thought was a boost leak. until i turned it up

Splitpi · 05-09-2008, 08:32 PM

boost leak test.

booostedGSX · 05-09-2008, 08:34 PM

Boost leaks are mysterious. Try that first, then go from there, I would say.

casperfast · 05-09-2008, 08:41 PM

ok, no problem, ill do a boost leak test on monday

redhotridur · 05-10-2008, 06:43 AM

Your car is probably running way richer after the rewire, which would explain why it runs good at 20psi but not at 12. (A wideband would be really helpful here.) It doesn't sound like a boost leak if it "hits over 20psi quickly," but it never hurts to double check. I recently rewired my fuel pump and was surprised at how much of a difference it made; about 28% more fuel at WOT.

casperfast · 05-10-2008, 09:19 PM

ok, one question i had about a wide band, can the factory ecu read off it? i know it doesnt bounce rich lean rich lean rich rich rich lean lean lean like a normal o2 the wideband says actual air/ fuel ratio. can the stock ecu read and understand it? would my car behave this was only until i complete a full drive cycle say a week or 2 or could it do this if i made a mistake (fu(ked up) and used a fuel additive that killed my cat and o2?

haioku-rocket · 05-11-2008, 02:51 AM

boost leak check and get a logger, best way to go.

haioku-rocket · 05-11-2008, 02:55 AM

Quote:

Originally Posted by casperfast

ok, one question i had about a wide band, can the factory ecu read off it? i know it doesnt bounce rich lean rich lean rich rich rich lean lean lean like a normal o2 the wideband says actual air/ fuel ratio. can the stock ecu read and understand it? would my car behave this was only until i complete a full drive cycle say a week or 2 or could it do this if i made a mistake (fu(ked up) and used a fuel additive that killed my cat and o2?

Stock ECU only reads a 0-1 volt narrowband o2 sensor signal. Widebands make a 0-5 volt signal. Basically your answer is no, stock ecu will not read a wideband. Also generally fuel additives will not kill either a narrow band or a wideband o2 sensor (especially not just one bottle). Its lead that is found in race gas that will kill o2 sensors. Most fuel additives do not contain lead.

tbonitz301 · 05-11-2008, 05:47 AM

The only thing that is 5v on our cars is the TPS sensor.I would consider a ball&spring mbc. After upgrading from the bleeder i think they are junk.+1 on the BLT

casperfast · 05-11-2008, 09:38 AM

well my mbc is a ball and spring, with a hole on the side. and the addative i used said "for off road use only, for vehicles not equipped with oxygen sensors or catalyst exhast, contains mmt" the main ingreidient in the stuff is toluene. ive been looking for some toluene to try out but this octane boost seemed to work great.

tbonitz301 · 05-11-2008, 11:32 AM

Quote:

Originally Posted by casperfast

well my mbc is a ball and spring, with a hole on the side. and the addative i used said "for off road use only, for vehicles not equipped with oxygen sensors or catalyst exhast, contains mmt" the main ingreidient in the stuff is toluene. ive been looking for some toluene to try out but this octane boost seemed to work great.

I didnt know they made them like that. If it has a hole in the side it has to be bleeding some air.

casperfast · 05-11-2008, 01:20 PM

yea, it is bleeding some ait. it has a knob, a spring, and a platic check ball in it, with a small hole on the side. i thought about covering the hole

dsm-onster · 05-12-2008, 09:24 AM

Don't cover the hole. That is supposed to be there. ALL ball and spring MBCs have/need this hole to control boost. Otherwise, once the spring/ball valve vibrates a few seconds, the boost in the line ater the valve (wastegate actuator) will equal the pressure before the valve (manifold presure). If the pressures are the same, then there is no boost control and you're running at wastegate pressure/stock boost at best.

Making the hole large curbs boost spike (not creep) when you turn in the MBC a bit tighter. A small hole causes the boost response to go up, but at the cost of some spike.