Got on the Dyno last weekend and noticed my boost was tapering off more than I had expected it too.. Had the MBC set to 21.5 psi, and it spikes to 22 and still falls to just below 19 at/near redline.. This chart look to be off to anyone?

(boost pressure in blue)


Mods:
- TBE
- intake
- Hallman MBC
- Dynoflash

..What is my best plan of action to eliminate the falling boost? Will upgrading the OEM diverter be any help?

 

what do u expect...its going to fall ur not going to hold 21.5 all the way to redline.

 

it s normal, dont worry about it, ur turbo is running more efficiently like that if the boost is lower by redline anyways.

pne more thing...Why does ur AFR goes leaner by redline? that s not very good

 

i really dont liek that AFR graph...did u get a custom flash or was it a mail in? Coz it could be a lot cleaner.

 

I guess I'm best off to deal with the boost taper eh

Nope, thats why a fuel pump is going in very shortly.

 

That was a mail in.. And which is why I put it on the dyno the following week.. I'm waiting to see what Cobb has to offer, and either going with them or AEM.. the flash was just to hold me over

 

Tapering to 19psi is really good ... I wish I could hold that much boost. I'm tapering down in to the 15s :-(

https://www.evolutionm.net/forums/sh...d.php?t=186438

 

wow really? and u have a IX? i have the hallman MBC and it doesnt taper any lower than 19 by redline.
Did u change your BOV? if u did Y?

 

Definately need to get a FP and a custom tune. Your APR graph is not very steady... and a few more ponies is left on the table due to that.

 

Yep, it's a IX. I originally had a Forge UNOS but the boost was wavering all over the place (later identified that a bunch of the UNOS MBCs required cleaning and greasing to work properly). I ordered a Hallman to replace it, but the shop didn't have any in stock so I'm using a TurboSmart loaner in the meantime. It looks like the TurboSmart doesn't hold boost too well (or I have some other problem, not entirely sure yet).

I have the stock BOV ... it has been crushed though as a diagnostic step when the Forge MBC wasn't working correctly. The crushing didn't help with my boost issue, it just made it easier to induce surge . It's definitely not leaking though, Warrtalon and I tested it to 25+ psi with zero leaks.

 

You think it needs a fuel pump?

I have a base Dynoflash. I agree the AFR doesn't look great, but it's a base flash and also a tailpipe sniffer was used as opposed to a bung in the exhaust, so I can't guarantee the accuracy of that data ...


edit: sorry, not sure if you were referring to me or the original poster ... IX fuel pump is stronger than the VIII, so now I'm thinking you were talking to Stew, sorry ...

 

Have you verified this with a MAP sensor that logs your boost through an entire 3rd gear pull? Most people just look at their gauge and make boost claims, but this is actual proof through a MAP sensor. If you have such a log, post it up.

 

I know I'm definitely due for a 255 lph pump.. AFR's were all over the place, but the Dyno graph turned out fairly pleasing for only a few mods:



(sorry for the blurry pic, no scanner in the apartment.)

 

The main 3 things I can think of to help boost from falling off is...

1 Leaks , but you said that you and Warr checked for leaks already , (Iam so proud that you checked 1st)

2 mbc ( soft spring?)

3 pre-loading the WGA

Warr is a pretty knowledgeable guy so iam sure what ever we can come up with he has prob all ready told you to try .

From what ive seen on my car is a 22 peak and droping to 20-21 . This is with a SW gauge and me looking/driving so take it for what its worth.

 

its spose to taper around that..i have the same setup with my boost spike at 21-22 and taper around 19