NewCelica.org Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
32 Posts
Discussion Starter #1
Hello everyone. I had a question regarding boost gauge vs map sensor. I have a aem FIC and an electronic boost gauge. Boost Gauge is reading vacuum from the nipple on the engine, and the aem is reading boost from another line. When I hit full boost my gauge reads 8-8.5psi but when I was doing some logging the aem FIC read 11-12PSI... Yikes. I know pushing the limits is 8psi on stock motor, which I have, but 11-12psi just seems to be a ticking time bomb. The motor is tuned and AF ratio when WOT are at a stable 11.2. The turbo is the t28 from turbokits.com if that helps any. Any suggestions as to what to do? obviously lower boost, but I thought tk.com kits came with a 8psi actuator? Sorry for the long post, just want to figure this out. I am surprised nothing has happened to the engine yet...
 

·
Registered
Joined
·
244 Posts
I would trust the gauge as it is taking readings directly from the intake manifold.

Where is the FIC getting its boost source from? If it is directly on the turbo outlet this makes sense, as usually there is some pressure drop in a piping system and the boost pressure will always be higher at the turbo outlet compared to the intake manifold.

You should plumb your waste-gate actuator up to your intake manifold as this is where you want the 8PSI to be at.

Definitely double check if you have a 8PSI wastegate spring in there man.
 

·
Registered
Joined
·
32 Posts
Discussion Starter #3
hey moo,
it is an internal wastegate connected to a piece on the outlet compressor housing so it is all connected on turbo side
(here is a pic)


The FIC is getting it's source from the engine as well. I forget which line it is but it is T'd with BOV. Tomorrow i will take a better look and get back to you. I bought the kit off someone on this site and he said it came stock at 6psi and he didn't mess with the turbo. could be time to replace actuator? maybe I'll run some compressed air and see at what psi the wastegate opens at.
 

·
Registered
Joined
·
32 Posts
Discussion Starter #5
Will do! hopefully sometime this weekend i can find an air compressor from a friend. I'll get back to you on how it turned out. thanks for the help moo!
 

·
Registered
Joined
·
244 Posts
I recommend grabbing a mechanical boost gauge and hooking it up to the nipple on the bottom right of the intake manifold. You'll get a true reading from there. No electronic crap to confuse you. I still would trust the electronic boost gauge over the FIC reading however

What engine are you running? The 2zzge engine came with a MAF sensor, not a MAP.

I recommend trying out blocking off the boost source nipple on the turbo compressor housing and routing a vacuum line all the way from the wastegate actuator to the intake manifold, see if you like how it drives after doing that.

I believe that the wastegate should open at 8PSI in the manifold and not 8psi in the compressor housing. that may be something worth playing around with in the future.

Let me know what PSI the wastegate opens at mate!
Talk soon
 

·
Registered
Joined
·
32 Posts
Discussion Starter #7
Before the electronic boost gauge I had a mechanical boost gauge as a temporary one. Hooked up to the same source, the nipple on the bottom right of the intake manifold, and It still read the same, 8.0-8.5.

Yes it is a 2zzge.

For rerouting the boost source on the actuator, would any place from the intake manifold work? Any recommended sources?

And will do man! Talk to you soon!
 

·
Registered
Joined
·
244 Posts
Get a T connector on the intake manifold nipple. that nipple is pretty much the only good boost/vacuum source available.

Just try re-routing the actuator boost source to this nipple on the intake manifold. See if it makes a difference, if you like it, leave it that way. If you don't, change it back to how it originally was. Don't forget to cap off the newly exposed nipple on the turbo compressor housing when doing this.

Don't forget to test wastegate!!

glad i can be helping you out :)
 

·
Registered
Joined
·
32 Posts
Discussion Starter #9
alright so i switched up some vacuum lines this weekend. I didn't get a chance to run compress air or switch up the line to the wastegate actuator. I did move the line that the aem fic was getting it's source from and now it is reading really close to gauge psi. FIC would say 8.6 and gauge would say 8.4. I'll keep a close eye on it next weekend, plus I turbo is starting to show signs of time to replace. But everything looks good... for now lol. I'm still going to run compressor air asap.
 

·
^^ I'm with stupid ^^
Joined
·
870 Posts
I would look at if your gauge reads absolute pressure or manifold pressure. The FIC reads absolute at it's MAP sensor and takes atmosphere pressure into account. Furthermore a wastegate also mitigates the boost pressure using manifold pressure and not absolute.


I have the same thing going on because my gauge reads manifold pressure and my FIC and Hydra reads absolute.

So my guess is that your Boost gauge reads manifold pressure and directly correlates with your wastegate spring of 8PSI while your FIC is reading absolute.
 
1 - 11 of 11 Posts
Top