I just installed the Defi white racer boost gauge. Everything went great and I noticed on a few WOT runs it seemed to spike (rapidly) close to 25-27psi then quickly drop down to under 20 where it tapers back down to where its supposed to by redline. I have a UIP installed with no tune. Can I attribute this to the UIP? Or is it possible my gauge is malfunctioning (not likely). Or is this perfectly normal? Didn't have much luck when searching for this.

Thanks in advance

 

In what gear are you seeing this? Make sure there are no kinks in any of the vacuum lines you tapped into including the gauge line itself. A tune would also help, if you are seeing over 25psi you should be setting over boost codes (1235) or similar limp mode. If you aren't hitting any boost cuts/ etc then I would look into the actual gauge itself.

Test this too: Start car, look at gauge. Turn car off then see where the needle lays at rest. Should be at 0. If the needles sits higher or lower then the gauge is defective.

 

I don't think the gauge is malfunctioning.

If you get tuned you can make that spike go away. Untuned and with some mods I had a huge spike that then tapered. Then I got a tune and he was able to straighten out my boost in an almost straight line.

 

Mine does the exact same thing on my Defi and you can see my mods in my sig. Mine does the spike to 27 psi and then quickly down to 20 psi and holds there until I let off the throttle. My guess is because it is untuned. No codes and car runs great, so all is well, nothing to worry about and your gauge is fine.

 

It looks like it may have not been reading as high as I originally thought. It may have spiked near 25 but seems to be at most 24, usually 23. So I'm assuming everything is working the way it should.

 

mine does the same thing and its tune.

 

That's one reason I installed my boost gauge as a first mod before anything else. Uphill on the highway in 5th gear at 3-4k RPM I think I saw the stock boost spike to 25 then settle to 23-24 with a pretty good taper down to 15 psi as you reached redline. This was before the updated flash which also seems to effect the boost curves slightly as well. My particular gauge has always read about 1 PSI higher than expected, it starts between 1 and 2 psi when the car is off and even a really high pressure system can't account for that. When I got my car dynoed we also datalogged boost and it also showed the gauge was reading high as well.