boost falls off in 1st every other gear fine WHY?
09-20-04, 07:20 AM
#1
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boost falls off in 1st every other gear fine WHY?
I was hoping it would never come to this. I have a boost problem and was unable to successfully figure it out on my own.
I bought this car 800 miles ago and have had this problem ever since.
94 fd only 11200 miles on the whole car.
KN filter and downpipe and catback exhaust.
If I floor it in first I get good 10 PSI then it transitions 8 back to 10 then falls on its face only making 3-4 from 5K to redline. When I shift to 2nd I get good 10 psi every other gear but first appears to make good boost with a good transition.
I tried a few tests.
if I rev it in first till 6K the boost falls off like every time so then I let off and get back into it still only get about 3 psi. My hope was if there was a faulty check valve the cannister would recharge quickly and boost would recover. to rule out the low load on the engine therefore no boost I punched it and held the brakes.
I checked 4 of the check valves on top of the engine (the ones I could easily get to) they were all fine. I looked for any loose hoses or splits or anything like that.
with suck low mileage on teh car nothing under the hood is dried out and craching like my last high mileage car. the check valves and all the vac lines look like new and all the turbo couplers are still soft and new looking.
I ruled out most of the high mileage stuff that age and wear contribute to.
What conditions exist in first gear that every other gear would not have with regards to boost?
I bought this car 800 miles ago and have had this problem ever since.
94 fd only 11200 miles on the whole car.
KN filter and downpipe and catback exhaust.
If I floor it in first I get good 10 PSI then it transitions 8 back to 10 then falls on its face only making 3-4 from 5K to redline. When I shift to 2nd I get good 10 psi every other gear but first appears to make good boost with a good transition.
I tried a few tests.
if I rev it in first till 6K the boost falls off like every time so then I let off and get back into it still only get about 3 psi. My hope was if there was a faulty check valve the cannister would recharge quickly and boost would recover. to rule out the low load on the engine therefore no boost I punched it and held the brakes.
I checked 4 of the check valves on top of the engine (the ones I could easily get to) they were all fine. I looked for any loose hoses or splits or anything like that.
with suck low mileage on teh car nothing under the hood is dried out and craching like my last high mileage car. the check valves and all the vac lines look like new and all the turbo couplers are still soft and new looking.
I ruled out most of the high mileage stuff that age and wear contribute to.
What conditions exist in first gear that every other gear would not have with regards to boost?
09-21-04, 01:30 PM
#3
apeiron
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Dont worry about it. My car has the same symptoms, I cant make full boost in first but everything else is fine. I dont even get up to 10 psi flooring it in first, I dont care though because I dont drag the car and for auto-x'ing I dont need massive amounts of power in first gear.
09-21-04, 01:38 PM
#4
Banned
How is the idle on the car? I just want to know since my GZ91Rx7 is having the same problem right now. And maybe the fix for this will fix his too. He can only boost 6 psi in 1st.
09-21-04, 03:02 PM
#6
Originally Posted by spoolage
1st gear never makes complete boost. Dont know why, just what I've been told. There is nothing wrong Im pretty sure
Ah no. 1st has always gotten full boost for me. I'm pretty sure it's the same across the board.
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09-21-04, 03:21 PM
#9
I'm a CF and poop smith
boost isnt exactly the same in every gear and i think its a relativly common problem, what kind of exhaust (size of piping and brand as well as do you have the stock cat still?)/intake (is it the cone type or a stocker replacement)/intercooler (and piping) as well as fuel system do you have?
09-21-04, 05:09 PM
#10
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Originally Posted by spoolage
Dont worry about it. My car has the same symptoms, I cant make full boost in first but everything else is fine. I dont even get up to 10 psi flooring it in first, I dont care though because I dont drag the car and for auto-x'ing I dont need massive amounts of power in first gear.
09-21-04, 05:13 PM
#11
Typically its one of the Turbo Control solenoids that causes the strange boost problems only in 1st and/or 2nd gears:
http://www.autosportracetech.com/RX-...leshooting.htm
I would start there.
http://www.autosportracetech.com/RX-...leshooting.htm
The Turbo Control Solenoid / Actuator is one of the more complicated actuators as it requires both vacuum and pressure to operate properly. This actuator is controlled by two solenoids, (both are wired together to the one ECU output) one solenoid applies pressure to one side of the actuator and the other applies vacuum to the other side of the actuator. With pressure on one side and a vacuum on the other side of the actuator, the speed of the actuator is improved. A typical problem is loss of Secondary boost in 1st or 2nd gear at 4,500 RPM, but reliable operation in other gears. This points to one side of the Turbo Control Actuator not getting it's pressure/vacuum, so it will still operate but not quickly enough.
09-21-04, 06:13 PM
#12
Oji San
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Yeah what magic said. I was having the same problem in first gear. I had an additional symptom that if I would wind out any gear I would have no boost in the next gear. I swapped out my turbo control solenoid and the problem went away,
09-28-04, 12:33 PM
#14
Bzzzzz
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Just some more quick observations:
I have my stock blow off Valve vented to the atmosphere on my 3rd gen. Every gear is the same except for 1st. On all the higher gears, rev, rev, boost 10-8-10 and woooosh !! BOV.
If you run any gear at all on half throttle, a percentage of the air comes out the blow off valve. You hear a longer air leak sound, not the full wooosh of the BOV. This is normal, cuz when I go from half throttle to full the valve closes up holds all boost in and hits the 10 psi as it should.
ps: my car is stock.
Now,
But on first gear, sometimes revs, boosts and then at the end of boost comes the wooosh, just like the others !!
But sometimes.......... on wide open throttle, I get rev, booost and then half throttle boost leak noise as some air is spilling through a semi closed BOV as if I were on half open throttle, but really I am WOT in first gear.
Hope it helps !!!
I have my stock blow off Valve vented to the atmosphere on my 3rd gen. Every gear is the same except for 1st. On all the higher gears, rev, rev, boost 10-8-10 and woooosh !! BOV.
If you run any gear at all on half throttle, a percentage of the air comes out the blow off valve. You hear a longer air leak sound, not the full wooosh of the BOV. This is normal, cuz when I go from half throttle to full the valve closes up holds all boost in and hits the 10 psi as it should.
ps: my car is stock.
Now,
But on first gear, sometimes revs, boosts and then at the end of boost comes the wooosh, just like the others !!
But sometimes.......... on wide open throttle, I get rev, booost and then half throttle boost leak noise as some air is spilling through a semi closed BOV as if I were on half open throttle, but really I am WOT in first gear.
Hope it helps !!!
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