Berg9987
08-18-2007, 06:41 AM
Quick history: Started as a 1987 MR2. One of the weird ones. Has the brake upgrade over previous MR2, no rear swaybar but all the mounts for one. Two owners prior to me did a 4A-GZE engine swap. When I got it, as it was my first forced induction car, so naturally I put a boost gauge in the car. It was an Autometer Pro Comp (silver face). It had a max boost reading of 30psi. With this gauge I was able to read 8pse max, which is what I've been told is what it should be.
Later I took out that boost gauge and put in one with a black face and a scale that read to a max of 20psi. I was hoping that I could get a more accurate reading with that. Unfortunately that gauge broke/wore out (would not settle on zero when car is off and gave a max boost reading of 3psi).
I replaced it with one of a similar model today. Zeros just fine and seems more responsive. I replaced the line from the manifold to the gauge with a new nylon/plastic one when I installed the gauge. Drove the car and got a max reading of 4psi, half of expected. I checked the intake track for boost leaks and tightenned all clamps. I then modified the vacuum lines to the ABV as per http://www.mr2sc.com/websites/tech/abvlines.htm. Managed to squeeze another psi out. So now it reads 5psi. I then did another mod I found on the same sight and removed the ACV http://www.mr2sc.com/websites/tech/air_control_valve.htm. This brought max boost up another 0.5 psi for a total of 5.5psi. Theoretically I should be running 9.5 at this point.
So my question is: Have I lost boost or am I getting an incorrect reading? How could I tell? If the car has lost boost it must have been gradually over time because there was no sudden change in performance (at least not that I noticed). I do expect a little bit of a drop in pressure throught the line from the manifold to where the gauge is mounted (steering column), but three psi sounds exessive to me. Besides, it was working with that first gauge (gauge is gone, so no chance of hooking that back up to check). Any thoughts? Things I should try/look for? Thanks in advance.
Cheers,
Berg.
Later I took out that boost gauge and put in one with a black face and a scale that read to a max of 20psi. I was hoping that I could get a more accurate reading with that. Unfortunately that gauge broke/wore out (would not settle on zero when car is off and gave a max boost reading of 3psi).
I replaced it with one of a similar model today. Zeros just fine and seems more responsive. I replaced the line from the manifold to the gauge with a new nylon/plastic one when I installed the gauge. Drove the car and got a max reading of 4psi, half of expected. I checked the intake track for boost leaks and tightenned all clamps. I then modified the vacuum lines to the ABV as per http://www.mr2sc.com/websites/tech/abvlines.htm. Managed to squeeze another psi out. So now it reads 5psi. I then did another mod I found on the same sight and removed the ACV http://www.mr2sc.com/websites/tech/air_control_valve.htm. This brought max boost up another 0.5 psi for a total of 5.5psi. Theoretically I should be running 9.5 at this point.
So my question is: Have I lost boost or am I getting an incorrect reading? How could I tell? If the car has lost boost it must have been gradually over time because there was no sudden change in performance (at least not that I noticed). I do expect a little bit of a drop in pressure throught the line from the manifold to where the gauge is mounted (steering column), but three psi sounds exessive to me. Besides, it was working with that first gauge (gauge is gone, so no chance of hooking that back up to check). Any thoughts? Things I should try/look for? Thanks in advance.
Cheers,
Berg.