I have a 2006 IX MR that is having a weird boost spike any advice / help would be greatly appreciated.

I had the car DynoFlashed (base) and the Forge MBC installed in January while Al was in Northern Virginia. I love the results, but am trying to understand why the boost shoots up to ~21.5 PSI @ 3100 RPM then drops to ~20.5 until ~3800 and then hits again like 22 PSI and then slowly tapers to ~18 PSI at redline.

Why the double spike boost? Is this caused because of a defective MBC? Is the stock exhaust with MIVEC screwing up the system? Other cars seem to hit boost a bit harder and can carry more torque. Thanks in advance for the help.

 

i have the exact same problem, i have a mbc, intake, LICP, and cat back ( no reflash yet) and i have the same problem as you.
I did log the car and found out that the car was pulling timing in that area, which would mean it s knocking and the car need more fuel in that rpm range.

Any tuner here could give us some help it would be great thanks.

 

Man i did somethin else... only mod is a perrin boost tube.... no exhaust or flash yet and when my spikes from around 20-21 back to 16 at redline once in a while it will freakin drop to like 11 or somethin. only happened like twice???

 

urs look like a different problem, urs sounds like a boost leak

for me it happens all the time, i am sure it s the same for cij911

 

Does anyone have an AVC-R? I am wondering if this would solve the problem?

I don't understand why folks settle for the kind of taper that many are reporting. I would think that one would want as little taper as possible. Sounds like the AVC-R can keep your boost at 21 all the way.....

Any Engineers / Engine Builders out there that can help me understand what might be going on???? I am wondering if the MIVEC is screwing with the timing with the sudden spike (based upon the rate of change) and then acepting the slow rise to peak.....If so, maybe a free flow exhaust would help (or am I just dumbbbbbb......)

 

Your prolly right but if it was a boost leak shouldn't it do it mroe often i have had that setup for a while now and haven't touched it since...but i drove it all day today and no problems.. o well i aint gonna worry with it till i put tbe intake and boost controller on.

 

Here is a chart I made of mine....

 

u have a custom reflash so r car probalby get all the fuel it needs between 3400 and 4000.

I just want to know if that weird boost spike can be related to timing/knock

by any chance do u have the AFR graph for ur car thx

 

well based on the log my friend and i did, timing goes to -3 at one point in that area and gos back to normal after 4000rpm. MIVEC kicks in aorund 3500rpm the timing should be around 19 and on the log it was at -3 which indicate knock.

I am just surprised that not that many people with 9's have noticed that weird boost spike yet

 

Yeah, mine is a custom flash. Just wanted to give you any bit of data that you may be able to use. On a side note, my UNOS was clogged up and Al cleaned it. This plot is after the clean and much better looking than before. You could def. tell the difference on the boost curves. Much more stable after the cleaning.

Girlie

 

let me see if I can compile a chart of pre-flashed boost.....

Girlie

 

yeh that would be great, also do u have the AFR chart before/after?

thx

 

Actually, I just went back thru and re-watched the video of the runs. I did not get a shot of the pre-flashed boost curve...sorry. I did notice a couple of things though.....

Before Al cleaned the MBC, I have the exact double spike that you guys are talking about. See pic


After cleaning the UNOS, the boost curve is much flatter, double spike is gone...


Girlie

 

all right great, so now i KNOW its timing/fuel related, thx a lot
i guess i just have to wait till i get my custom reflash thx a lot Girlie

 

Did you make sure that the bleed hole is clean on the UNOS? After watching the video, even after 2 flashes it was still evident. After Al cleaned it, it went away and stayed nice and flat for the remaining pulls. Al even made a comment about after the first pull when he cleaned it. Just want to make sure it's not something that can be easily fixed for ya..

Girlie