Help: Stock boost on 940T (13C), >5 psi?!?!

L8 APEKS · 08-24-2007, 01:50 AM

Hey guys,

I have been trying to troubleshoot my boost lag problem for a while now, but I've only been "bench troubleshooting".

The car is a '95 940T...15G, 3" DP/exhaust, Fredchips, cone, 36# injectors, IPD turbo cam. I swapped my w/g actuator from my stock 13C on to the 15G.

Here's the thing...since the day I installed my 15G, my boost lags like balls. I don't feel a "surge" in power until ~3500rpm. Also, my MBC seemed "unresponsive", as I had to crank it a bunch of turns to net a small increase in boost. So I made a little list of possible culprits, one of which included a bad w/g actuator. I welded it to a new bracket, and I'm wondering if the heat from welding killed the internal diaphragm.

Today, I unhooked my Hallman MBC and ran straight off the W/G actuator. My boost gauge is pegging at just under 5psi. Does this mean my laggy boost is, in fact, being caused by a lazy w/g actuator? The rod is certainly pre-tensioned; I had to pull it out at least 1/4" to get it on to the w/g flap.

More importantly, how can I bench test the actuator? I was thinking of running to Harbor Frieght and rigging a low-psi hand pump and pumping pressure into the w/g nipple. The problem is, I don't know when it should move! 2psi? 7psi? What is it supposed to do if it's working properly? And also, should it hold the pressure constant? IE, if I pump it with 7psi and it leaks down, does that mean it's bad?

Let me know how to test this thing and see if it's bad. I'm pretty sure it's the problem, but I want to know 100%. Thanks in advance!

IceCold4x4 · 08-24-2007, 02:30 AM

how easy is it if you blow on the nipple to move. when i bought my 15g the actuator that came with it out of the box wouldn't hold more than 10 psi even with the line pulled, it just didnt' have enough resistance, (i guess it was for a LPT setup). if you blow onto the nipple and it moves get a new WG actuator

L8 APEKS · 08-24-2007, 02:34 AM

Ok...so if I can blow in it, and the rod moves, it's bad? I don't think it moves that easy, but I'll try it. Still...can it be bad even if I can't get it to move just with mouth pressure?

Lucky the Smiling Pirate · 08-24-2007, 03:02 AM

factory boost was 5-7psi, WG seems a bit low but not obscenely so.

your 15g sounds only slightly slower than mine. I start to get most of my boost in the 2800-3200rpm range and I would say that the car doesn't hit the peak of its pull until 3500.

I'm still using the T cam. you using the ipd cam, its got better top end so you may be feeling the combination of turbo and cam.

IceCold4x4 · 08-24-2007, 03:04 AM

that slow lucky? i was climbing a hill a few minutes ago and got almost 5 psi at 1/4 throttle and 2500 rpms. . . . I'll get 20 psi around 3 at the latest. then again i'm using a SEVERLY ported housing and manifold on a 3 inch DP that's about 6 inches long.

Lucky the Smiling Pirate · 08-24-2007, 03:05 AM

I make boost just fine.

I've got 5psi by 2500. I'm also only running 10psi so that has me boosting later than i would if i were making 20.

he spoke of the 'surge' of power. my car doesn't really come alive until 3-3.5k rpm and then starts falling off again around 4.5-5k

IceCold4x4 · 08-24-2007, 03:14 AM

i don't see how you live at only 10 psi. it's so little boost.

if the bracket isn't bending, and the actuator can't be moved by the mouth easily, then it seems to me that maybe it's binding? check to make sure the nut doesn't catch on the return tube

Lucky the Smiling Pirate · 08-24-2007, 03:17 AM

Quote:

Originally Posted by IceCold4x4

i don't see how you live at only 10 psi. it's so little boost.

its hot outside, I can hear it ping on hard acceleration everyonce in a while when it creeps to 12, I'm still using the stock IC, and only 91 octane gas.

When things cool down I'll make a good attempt to blow it up with 10 or 20 runs with the WG actuator disconnected (heh, boost gauge only goes to 25psi I think?

) so I've got a good reason to put the new motor in/get manifolds made for it

IceCold4x4 · 08-24-2007, 03:18 AM

it prolly won't make more than 25 psi of boost well not at redline at least.

GET A BETTER INTERCOOLER!!!!

it really makes a difference. and BTW move somwhere with good gas your car will thank you.

/ end low boost rant.

Lucky the Smiling Pirate · 08-24-2007, 03:23 AM

Quote:

Originally Posted by IceCold4x4

it prolly won't make more than 25 psi of boost well not at redline at least.

GET A BETTER INTERCOOLER!!!!

it really makes a difference. and BTW move somwhere with good gas your car will thank you.

/ end low boost rant.

we've got 100octane at a few pumps here. I run it when im at the track. I can peg the needle on my boost gauge when the actuator hose pops off

if the gauge is perfectly linear past the 25psi marker, its got room to draw hash marks up to 30psi. I dont think it makes much of a noticable power difference from 20-30psi but its been a while so i could be mistaken

also, ive got a better IC, i just havent installed it. ebay 24x12x3 core. I've got some ideas for going bigger but I think I should use what i've got for now

L8 APEKS · 08-24-2007, 01:02 PM

Thanks guys...it seems that maybe my actuator is OK after all, and it's just the 15G + IPD cam on an auto car. :(

Really suxx0rz though. I will look at getting a cam gear, and porting out the manifold and turbo. Hopefully that will bring the powerband down a little.

Also good to know that I'm not the only one suffering from "stock IC syndrome" and "crappy 91 octane piss water" syndrome.

Lucky, are you in CA as well?

I was planning on getting an "ebay special" IC as well. Lucky, have you glanced at how this might fit? I was afraid to buy one because I wanted to keep my A/C and I wasn't sure if that would fit without a good deal of hacking (light hacking should be expected I think, no big deal). Maybe if I go to a slim electric fan?

Lucky the Smiling Pirate · 08-24-2007, 01:16 PM

you're driving a 940 already so you should have the 'good' e-fan already.

You're gonna have to move the radiator back just a teenie bit to get the ebay IC in between the condensor and radiator, but I KNOW that there is room for a 4inch in between there so it shouldn't be an issue to fit in the 3inch one.

I am not in cali anymore. I live in AZ atm.

L8 APEKS · 08-24-2007, 01:32 PM

Oh, it would go in front of the condensor. Not behind.

IceCold4x4 · 08-24-2007, 11:02 PM

^ that's what i like to hear, just get rid of the condensor you really don't need a/c i mean i live in alabama the armpit of hell and get along just fine.

08-24-2007, 01:50 AM	#1
L8 APEKS Yayayaya, hohohooo!!! Join Date: May 2006 Location: Orange County, CA	Help: Stock boost on 940T (13C), >5 psi?!?! Hey guys, I have been trying to troubleshoot my boost lag problem for a while now, but I've only been "bench troubleshooting". The car is a '95 940T...15G, 3" DP/exhaust, Fredchips, cone, 36# injectors, IPD turbo cam. I swapped my w/g actuator from my stock 13C on to the 15G. Here's the thing...since the day I installed my 15G, my boost lags like balls. I don't feel a "surge" in power until ~3500rpm. Also, my MBC seemed "unresponsive", as I had to crank it a bunch of turns to net a small increase in boost. So I made a little list of possible culprits, one of which included a bad w/g actuator. I welded it to a new bracket, and I'm wondering if the heat from welding killed the internal diaphragm. Today, I unhooked my Hallman MBC and ran straight off the W/G actuator. My boost gauge is pegging at just under 5psi. Does this mean my laggy boost is, in fact, being caused by a lazy w/g actuator? The rod is certainly pre-tensioned; I had to pull it out at least 1/4" to get it on to the w/g flap. More importantly, how can I bench test the actuator? I was thinking of running to Harbor Frieght and rigging a low-psi hand pump and pumping pressure into the w/g nipple. The problem is, I don't know when it should move! 2psi? 7psi? What is it supposed to do if it's working properly? And also, should it hold the pressure constant? IE, if I pump it with 7psi and it leaks down, does that mean it's bad? Let me know how to test this thing and see if it's bad. I'm pretty sure it's the problem, but I want to know 100%. Thanks in advance! __________________ Sean Williams '94 850 Turbo Wagon (daily) :: 14.0 @ 98.5 B5234\|AW50\|TLAO tune\|3" exhaust\|NA cams\|65mm tb\|38mm BOV\|E40 blend '75 244GL (project) :: 8.4 @ 85.6 B230FT\|AW71\|1031\|gutted\|TLAO chips\|welded 3.73\|19T\|3" exhaust\|IPD cam\|E62 blend\|55 lb inj. (@ 4 bar) CLICK HERE for the 244 BUILD THREAD! *BRAND NEW Mitsubishi 18T and 19T turbo conversions for sale...from $450...CLICK HERE or PM for details!*

08-24-2007, 02:30 AM	#2
IceCold4x4 Board Member Join Date: Feb 2006 Location: Birmingham, Alabama	how easy is it if you blow on the nipple to move. when i bought my 15g the actuator that came with it out of the box wouldn't hold more than 10 psi even with the line pulled, it just didnt' have enough resistance, (i guess it was for a LPT setup). if you blow onto the nipple and it moves get a new WG actuator __________________ 1992 Volvo 940 Turbo - Being parted out 2006 S60R - Electric Silver / Nordcap - A Stocker Deluxe with Cheese (dreamed about this car for 6 years now I own one YEA!) 2006 XC90 V8 AWD - Triple Black - The gun mobile.

08-24-2007, 03:02 AM	#4
Lucky the Smiling Pirate roadkill Join Date: Aug 2005 Location: Phoenix, AZ, USA	factory boost was 5-7psi, WG seems a bit low but not obscenely so. your 15g sounds only slightly slower than mine. I start to get most of my boost in the 2800-3200rpm range and I would say that the car doesn't hit the peak of its pull until 3500. I'm still using the T cam. you using the ipd cam, its got better top end so you may be feeling the combination of turbo and cam. __________________

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08-24-2007, 02:34 AM	#3
L8 APEKS Yayayaya, hohohooo!!! Join Date: May 2006 Location: Orange County, CA	Ok...so if I can blow in it, and the rod moves, it's bad? I don't think it moves that easy, but I'll try it. Still...can it be bad even if I can't get it to move just with mouth pressure?

08-24-2007, 03:04 AM	#5
IceCold4x4 Board Member Join Date: Feb 2006 Location: Birmingham, Alabama	that slow lucky? i was climbing a hill a few minutes ago and got almost 5 psi at 1/4 throttle and 2500 rpms. . . . I'll get 20 psi around 3 at the latest. then again i'm using a SEVERLY ported housing and manifold on a 3 inch DP that's about 6 inches long.

08-24-2007, 03:05 AM	#6
Lucky the Smiling Pirate roadkill Join Date: Aug 2005 Location: Phoenix, AZ, USA	I make boost just fine. I've got 5psi by 2500. I'm also only running 10psi so that has me boosting later than i would if i were making 20. he spoke of the 'surge' of power. my car doesn't really come alive until 3-3.5k rpm and then starts falling off again around 4.5-5k

08-24-2007, 03:14 AM	#7
IceCold4x4 Board Member Join Date: Feb 2006 Location: Birmingham, Alabama	i don't see how you live at only 10 psi. it's so little boost. if the bracket isn't bending, and the actuator can't be moved by the mouth easily, then it seems to me that maybe it's binding? check to make sure the nut doesn't catch on the return tube

08-24-2007, 03:18 AM	#9
IceCold4x4 Board Member Join Date: Feb 2006 Location: Birmingham, Alabama	it prolly won't make more than 25 psi of boost well not at redline at least. GET A BETTER INTERCOOLER!!!! it really makes a difference. and BTW move somwhere with good gas your car will thank you. / end low boost rant.

08-24-2007, 01:02 PM	#11
L8 APEKS Yayayaya, hohohooo!!! Join Date: May 2006 Location: Orange County, CA	Thanks guys...it seems that maybe my actuator is OK after all, and it's just the 15G + IPD cam on an auto car. :( Really suxx0rz though. I will look at getting a cam gear, and porting out the manifold and turbo. Hopefully that will bring the powerband down a little. Also good to know that I'm not the only one suffering from "stock IC syndrome" and "crappy 91 octane piss water" syndrome. Lucky, are you in CA as well? I was planning on getting an "ebay special" IC as well. Lucky, have you glanced at how this might fit? I was afraid to buy one because I wanted to keep my A/C and I wasn't sure if that would fit without a good deal of hacking (light hacking should be expected I think, no big deal). Maybe if I go to a slim electric fan?

08-24-2007, 01:16 PM	#12
Lucky the Smiling Pirate roadkill Join Date: Aug 2005 Location: Phoenix, AZ, USA	you're driving a 940 already so you should have the 'good' e-fan already. You're gonna have to move the radiator back just a teenie bit to get the ebay IC in between the condensor and radiator, but I KNOW that there is room for a 4inch in between there so it shouldn't be an issue to fit in the 3inch one. I am not in cali anymore. I live in AZ atm.

08-24-2007, 01:32 PM	#13
L8 APEKS Yayayaya, hohohooo!!! Join Date: May 2006 Location: Orange County, CA	Oh, it would go in front of the condensor. Not behind.

08-24-2007, 11:02 PM	#14
IceCold4x4 Board Member Join Date: Feb 2006 Location: Birmingham, Alabama	^ that's what i like to hear, just get rid of the condensor you really don't need a/c i mean i live in alabama the armpit of hell and get along just fine.