I recently installed my spec I profec b on my 15g greddy setup. In 3rd gear, I have it pretty well dialed in to boost 11psi and then it settles to about 10psi. I was happy with that unitl a few minutes later I did a 2nd gear pull and it hit 11psi and dropped to 8psi. I then tried 3rd gear again and it worked like before. What could the problem be? Since it's hitting 11psi, i turned my dipswictches to the overboost mode. I know the Profec A has a boost drop setting, does the profec b? TIA

 

helllllllppp

 

try raising the gain.

 

its the spec I, it has a balance and I DID play with that. The spec II has the gain, but I dont believe this one does. Does anybody know of a boost drop function?TIA

 

oh sorry i've only messed with the spec 2

 

its okay, thanks for trying Ill just consider it a bump

 

up

 

bump?

 

My old profec B (1gen) would definately spike if the gain was turned (let me think back) anywhere over half. Anywhere under half on the gain seemed to make things more stable, and I never really noticed that the gain did anything else (but **** with the overboosting)

Oh, I miss that thing. low setting for daytime, and high setting for night. The temp. outside seemed to change the amount of boost more than anything.

 

I would say there is not enough load in 2nd gear to hold the boost you are looking for. have you tried doing a 4th gear pull? I bet it will stay at 11 no problem.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Butcher &raquo;</TD></TR><TR><TD CLASS="quote">I would say there is not enough load in 2nd gear to hold the boost you are looking for. have you tried doing a 4th gear pull? I bet it will stay at 11 no problem.</TD></TR></TABLE>

Agreed.


With low load, your RPMs will be rising quickly and the massflow the turbo has to put out increases quicker at the same pressure. Look at the speed lines on a compressor map and you'll see that when you run the **** out of a small turbo(like you are doing), the compressor can slowly accelerate in the low/midrange, then as you start running the poor bastard off the edge of the map the speed has to increase really rapidly to keep the pressure up for the massflow the engine is wanting to consume at that pressure ratio and RPM. In 2nd gear your engine is accelerating so quickly that the turbo just can't physically accelerate the compressor wheel fast enough to keep the pressure up.

It's actually pretty common on small turbos, you just don't hear about it on these boards much because everybody thinks a compressor the size of a small child is "moderate." hah

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Def &raquo;</TD></TR><TR><TD CLASS="quote">Agreed.


With low load, your RPMs will be rising quickly and the massflow the turbo has to put out increases quicker at the same pressure. Look at the speed lines on a compressor map and you'll see that when you run the **** out of a small turbo(like you are doing), the compressor can slowly accelerate in the low/midrange, then as you start running the poor bastard off the edge of the map the speed has to increase really rapidly to keep the pressure up for the massflow the engine is wanting to consume at that pressure ratio and RPM. In 2nd gear your engine is accelerating so quickly that the turbo just can't physically accelerate the compressor wheel fast enough to keep the pressure up.

It's actually pretty common on small turbos, you just don't hear about it on these boards much because everybody thinks a compressor the size of a small child is "moderate." hah</TD></TR></TABLE>
This is probably the problem i have with my tiny *** wrx turbo not being able to hold boost. It shoots up to where i want it to be and then drops back down to 9psi . Whats strange though is that it used to hold 10psi great with the old internal wastegate, but it didn't work right so i wouldn't hit full boost until after 5k rpms. Now it spools instantly with my tial

 

well that makes sense as to why it's doing it, but is there anyway to fix it?3rd gear holds pretty well in my opinion and 1 psi isn't something to get excited about. I thought about making my low boost setting a little higher so that i could have 10psi in 2nd gear and then hit the high boost switch to have 10psi in 3rd as well. and no I haven't done a 4th gear pull yet. I noticed on the profec a on greddy's website that if you move the dip switches to a particular setting it helps with boost drop, does this have any such features?

 

If your wastegate is pretty much closed in 2nd gear when it's dropping off boost, then sorry, that's just what the turbo does.

I push my T25 way farther than I probably should - about 14.5 psi in the midrange and it drops off in any gear to about 11 psi at redline. The turbo just can't flow more up top. But in lower gears it'll build like 8 psi in 1st and actually drop off quick towards redline because the engine is outrunning the turbo. 2nd gear it kind of does the same thing, up to about 12 psi then falls off to around 10 psi.

 

i tried helping him with this and i know it sucks but i think of it as a gear dependent boost controller

so i got it to hold good in 3rd gear as i figured when racing his 3rd gear will be most used on the track along with 4th so id rather see those gears hold steady then 1st or 2nd

 

Now that it's cold out...it sometimes goes 11psi steady, jumps to 13 then back to 11. Does any of this have to do with leaks somewhere or is it most likely the shitty greddy wastegate? would adjusting the wastegate itself help at all?

 

Sounds like another inefficient turbo thread. Your running the turbo beyond its range. Does not sound like you have a leak just that the turbo can't keep up with the demands. A large indicator of that is boost falling off.

 

I'm having that same problem but I'm using a Turbo XS standard boost controller. It goes from 10 down to 6 or 7, then back up to 10 then down to 6 or 7. Mind you this is only happening in 3rd and 4th gear, 5th I'm not sure because I don't usually go into full boost in 5th. I'm currently using a Deltagate II and my friends suggested that it was the wastegate that's causing this problem because it can't hold boost. So if you have a friend with a Tial try borrowing his/her wastegate and see if that corrects the problem. As for me, I'm still saving to get a Tial. Good luck!

 

i realize this turbo isnt for high boost applications, but i had been under the impression they dont run out of efficiency until 15psi. Or did u mean that the turbo has too small tokeep up with the motor in the higher rpm's? It's an internal wastegate so tial is out of the question without a lot of modification. Turning boost up from the wastegate most likely wouldnt fix this then?worth a shot?

 

I believe not in this situation. You will just be throwing more money into "trying to fix the problem" and not "fixing the problem". The turbo needs to be matched with the output of your head and the gear ratios, much more in a turbo application as to what psi it will push before running out of air. In lehman terms ...your intake is sucking more air than your turbo is putting out. This is why u are losing pressure.

 

guess ill just have to deal with it...i dont wanna doa different setup because i like the a/c compatability of this one. thanks for the help