On the highway today, cruising in 5th I smoothly worked the Evo up to WOT. Boost climbed and held steady at 19lbs, higher than I am used to seeing in 5th at WOT but it was pretty chilly here (35 F). After coasting back down to about 65, I downshifted to forth and went to WOT, boost climbed to 19 lbs and then wildly fluctuated from 19 to 15 lbs and back. I retried 5th gear (19 lbs steady) and then retried 4th (19-15 fluctuating).

Is this normal? My two possible thoughts were a leaky BOV (stock) or the wastegate activation.

I have a Defi D-series gauge that has never acted up before, and I am tapped into the vac line running between the intake manifold and the FPR.

any ideas?

thanks

 

im also thinking the cold weather made your boost spike... you didnt mention if you had stock or aftermarket boost controller.....

 

engine wise the car is stock

stock BC, stock BOV, stock intake, stock exhaust

 

You beat me to the post for the very same question! Mine does the same thing. I spike to 22 then fall back to 20 then 17.5. Sometimes it wiggles between 15 and 17, sometimes it is rock solid. I just installed the 42 Draft gauge kit with boost, Oil PSI and Oil Temp.

BTW: Do you get 19 on the vaccuum side for idle?

 

i do occasionally get 19 on the vac side, but usually its 16-17 inHg

 

if its stock the evo boosts up to 19.5 and drops back to 16. if its constantly boosting 19 and staying there, consider yourself lucky!

 

yes i feel lucky.

But here is the thing about boost fluctuation. It's there so the car wont lean out too much, I think.

If you know how to modulate the accelerator just right, then the boost will stay at 19.5psi until the redline.

Trust me, I do this all the time without MR BOV or Boost controller.

 

get a MBC it'll feel even betta!!

 

Yeah, mine will do the same if you hold the gas pedal half way. If you floor it, it spikes then pulls back.