FDjunkie

My new (about a month old now) Defi mechanical boost/vacuum gauge almost always seems to indicate a high boost reading when accelerating at maybe 1/2 throttle and w/RPM’s sometimes passing up in to turbo transition range; readings regularly indicate 12-15 PSI. But I’ve NEVER seen do this at WOT (10-8-10), so I didn't think I was seeing an actual boost spike.

Engine, turbos, IC, exhaust, etc. all (boringly) stock. Gauge’s rubber hose is connected to normal UIM connector, goes through the firewall just above the throttle cable, and follows steering column up to my column mount.

I’m just wondering if the internal mechanism is somehow designed to indicate high boost during quick transitions in an effort to prevent under-shoot. Anyone else ever notice this kind of behavior, or can/does the 3rd gens turbo control system cause boost spikes to really occur at 1/2 throttle while not at WOT?

Rx-7$4$me

I have had the defi boost gauge for about a year now, and while it does tend to read a teany bit high, I have never seen this overboost display that you are speaking of, somthing could be wrong with your gauge.

rynberg

Are you running a soft rubber hose through the firewall? It may be getting pinched. You should use some hard tubing to reinforce the vacuum line. This is how my boost controller hose is run.

RecKleSs

Which Defi series boost gauge are you using?

FDjunkie

Thanks for the feedback guys.

RecKleSs - The gauge is a brand new black-faced D-gauge installed using the heavy rubber tubing supplied in the box. I've got it mounted in a steering column mount with the light wire tapped in to the radio wiring.

rynberg - I don't think the line is pinched where it goes through the firewall because I drilled a hole that provided extra clearance, then used black RTV to seal the hole and stop any movement or chaffing. However, one of the tie-wraps though could be too tight. I guess a pinched line might make a boost gauge slow to respond, but it doesn't seem slow to me. Its movement seems to quickly match engine/throttle changes.

Rx-7$4$me - I'm along way from seeing something like a slight calibration error when the guage is displaying 12-15 PSI spikes, and a 10-8-10 under WOT suggests its not a gauge error.

I guess I'm really left with a possible boost spike situation that only occurs under light loading. I need to search the forum some more to see if anyone ever mentions this kind of behavor.

rookie7

I seem to be getting the same problem lately. Under 1/2 to 3/4 throttle I get spiking between 13 to 15 psi before the transition point. If I do a wot run I get 11-8-11psi pattern. If I give partial throttle then let off and then throttle again I can get it to spike also. I've checked for leaks and didn't find anything, I've checked the PC and WG solenoids and they're ok. My next check will be the pill in the PC line to see if it is clogged. Other than that I'm stumped, it seems like a strange problem. My car is stock and I am also using a defi boost gage. I never noticed this problem before and I've had my boost gage for a while, I think this is a recent development. If anyone has some adive I would appreciate it. thanks

rookie7

i meant to say advice

n/arotary

iTrader: (1)

FDjunkie,

Did you ever solve your boost spike problem? I just installed an Autometer Boost gauge, and I am getting the same spiking issue.