Boost Surge, or do I just not know what I'm seeing?
 

Tonight I was driving home and got into it a bit.
Since I have a nice new Defi Boost gauge, I'm paying more attention to things.

I was in 4th and hammered it, the boost spiked at around 26 then dropped down to 19 and then tapered down to 16 or so. (I did this a couple times to make sure it wasn't a fluke)

Is something wrong here? At idle, with no throttle applied, the gauge sits around 20inHg. Is that correct?

thanks

/ancker

what mods do you have?the idle is about right since what you are seeing is vacumm pressure.

I'm bone stock

Is it a BF or D-series?

Defi-D Boost Gauge

Here is a pic at idle:
http://cub.cites.uiuc.edu/~hardenrm/newcar/img_0072.jpg

if he saw 26, then it has to be the D-series...BF is in bar only

I know that stock that you're supposed to get 19 then taper down to like 15 or so, but I have no idea why you'd see it all the way to 26psi (and if you did, I suspect you'd damage your motor really quick due to detonation). Where are you running your gauge line to?

And idle is supposed to be in vacuum. You're not building boost, so no positive manifold pressure. That's perfectly normal. If you're spiking to +26psi in BOOST then I would be worried

I followed this How-To:
http://www.evomoto.com/tech_info.php...3_9&tech_id=14

And yes, I saw it in Boost, 26psi....but it only goes there for like a split second, then drops back down, the car still pulls hard, and drives without any problems.

hmm...that sounds like a faulty gauge to me. There's no reason why it should do that, because you're not seeing 26lbs of boost for that time (trust me, you would know...both by the extreme g's you'd be pulling and the fact that your motor would probably blow up). I would try finding a different vacuum source and testing it, or just getting a different gauge. Something's wrong with the gauge setup though - that's my unprofessional opinion (but I've dealt with this stuff for a long time)

Stock EVOs typically have a boost spike. 26PSI is a little higher than the norm though. If this was at night, the cooler air may have contributed some. Does the gauge sit at zero with the engine off?

factory fuel/boost cut is at 24 so i doubt you boosted to 26, but if you are you need to get that fixed because you will pop your engine quite quickly

Boost Spike
 

I have the same guage and show a 23 to 25 PSI spike when I get on it.
I think its the guage or the installation.

I have the Mods listed below.

Actually the '05's have more boost stock due to the new compressor wheel and 10.5 hotside. It's like 20.5 psi for stock 05's

Doing the conversion on the stock sports meter gauge, this is confirmed 20.5 psi (assuming an accurate Mitsu boost gauge) it only jumps there until about 4k rpms then back to 16psi up to redline

do u have a leak anywhere? check ur vacuum lines. I remember I had a slight leak in my vacuum lines after installing my HKS EVC V and it spiked to 23-24 psi. Check ur T's and hoses for leaks. Pop ur hood and start listening. Or better yet, poor some water or any thick subtance with high viscosity onto the lines u tapped and T'ed or similar and check for bubbles. I am saying u have a leak somewhere.

I checked before I left for work this morning. No Leaks.

I'll do some more experimenting after work today.

Defenitely not compressor surge, that is when the low pressure region grows outside and around the turbine blade, then that cause the whole system to run backwards. (I think I explained that right). Kind of hard to explain it w/o visuals, so that may not make sense, but in other words if u had compressor surge the system would be pumping air out of ur intake filter, and sucking air out of the combustion chamber blah blah blah..... Its bad and if it was happening you (and the ecu) would realize it real quick.