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Just purchased 740 turbo and have a few questions

Brickerz

Brickerz

Not your grandpa's Volvo
Joined
Mar 13, 2012
Location
York, PA
Hey guys,

Been browsing the boards now for a couple weeks reading everything I can on volvo's, since I'm a complete nooby to them.. I just picked one up which happens to be Nemesis' old car. I really love the design of the car and everything feels great, but I'm having some performance issues that are completely stumping me.

First of all... the mods from what I was told:

91 740 Turbo

Bigger injectors
IPD turbo cam with adjustable gear set to 5degrees advanced
3" exhaust with high flow cat
Greddy bov
What I believe is a larger stock turbo

After buying the car I brought it home and started doing the normal maintenance. First things was replacing like 20' of vacuum lines to be sure I wouldn't have any vacuum leaks. After that I replaced all the older, work/rusty clamps with new ones. There was low compression in the first cylinder and we thought it might be a head gasket, although there was no smoke. A freshly rebuilt head came with the car when I had bought it so I went ahead and bought the head-up gasket kit and replaced the head with the new fresh one (8v head). Made sure my timing was set right with the crank case mark and having the cam at TDC, put it all back together, put in fresh coolant and did an oil change. At this point I thought the car would be running great, but it still feels like it's realllly lacking power :-( I did notice a small crack on the exhaust manifold, but other than that everything looks fine.

Got it all back together and did some good ol' driveway test launching :-P For some reason it doesn't seem to build boost until extremely late in the power band (4k'ish rpm) and even then it's only about 1/4 of the way into the boost range on the gauge. I can put the pedal all the way to the floor and it doesn't seem to help at all, just feels really sluggish. After I let off the throttle, the car drops REALLY low in rpm's and after it's run for a little and warms up or driven for a longer distance it stalls and I have trouble getting it started again. I have checked the MAF and cleaned it, along with cleaning the throttle body. I believe maybe the O2 sensor is gas soaked or something since it threw the check engine light....

How should the bov line be hooked up? I keep looking at pictures and diagrams and I can't make sense of what should go where since they're all slightly different. The car has a line coming off the turbos wastegate going into a "Y" adapter with the bov going into the other side of the "Y" and then both of those go into the single line that feeds into the intake manifold behind the throttle body, which I'm assuming in manifold vacuum. Could this be causing the issue of the car not building boost and stalling after throttle? I'm new to the whole turbo thing....

I did the whole starting fluid trick to check for any vacuum leaks and I can't find any at all, and I double checked all of my intake/exhaust nuts to be sure they were tight. At this point I'm stumped

Thanks guys for all of the knowledge I've gotten so far from reading. Sorry if some of this has been covered before, but I haven't read it =/ I've been doing nothing but research on this thing for weeks now and I feel lost.

Thanks for all the help in advance!
 
whats the setup on the wastegate? manual boost controler? Did you change those hoses?
If the wastegate is open all the time that'll kill the boost.
or it could be the BOV being open when it shouldnt, letting the boosted air out when the TB is not closed.
on my stock turbo with CBV, the CBV has a line from the intake manifold. Maybe to run a BOV its different but I dont see why it would.
I believe the wastegate should have a line going to the turbo, not the intake manifold. at least thats the way it is on my stock turbo.
 
Liquidx said:
Hey guys,


How should the bov line be hooked up? I keep looking at pictures and diagrams and I can't make sense of what should go where since they're all slightly different. The car has a line coming off the turbos wastegate going into a "Y" adapter with the bov going into the other side of the "Y" and then both of those go into the single line that feeds into the intake manifold behind the throttle body, which I'm assuming in manifold vacuum. Could this be causing the issue of the car not building boost and stalling after throttle? I'm new to the whole turbo thing....

I did the whole starting fluid trick to check for any vacuum leaks and I can't find any at all,


Thanks for all the help in advance!
Click to expand...

Get a boost gauge first.
http://www.davebarton.com/740TurboBoostGauge.html
One of the Dave Barton faces if your dash suits. Or a outboard one.


The wastgate should be hooked up to the turbos compressor. With a MBC possibly between

The Original CBV on these goes straight to the Inlet manifold so I would hook the BOV there first. No Y connectors needed.
 
yeh the wastegate line going to the intake manifold isnt right. It shouldnt Y into the same line as the BOV.
Look for a nipple on the trubo's compressor and hook the wastegate line to that...
and delete the Y, and run 1 line from the intake to the BOV.
Your low boost could be the wastegate being fully open if its not hooked up right.

as i recall the wastegate opens once the vacuum in the line that goes to it raises over a certain #psi. with most its like 1-3 psi before the wastegate actuator starte to open the wastegate. since the vacuum in the intake manifold would be much higher, it must be opening your wastegate all of the time.
 
ghost civic said:
yeh the wastegate line going to the intake manifold isnt right.
Click to expand...

It's fine as long as the compressor nipple is plugged and it has its own dedicated line. This is actually my preferred method of giving the wastegate its signal..

ghost civic said:
since the vacuum in the intake manifold would be much higher, it must be opening your wastegate all of the time.
Click to expand...

Vacuum won't open the wastegate.
 
944Turbo said:
It's fine as long as the compressor nipple is plugged and it has its own dedicated line. This is actually my preferred method of giving the wastegate its signal..



Vacuum won't open the wastegate.[/QUOTE]

you are right, dont know what i was thinking.

It definatly sounds like his car either has the wastegate open all the time, or the BOV set wrong as either of those things can cause boost not to build.

the OP may just need to double check all the lines he replaced. maybe one got missed, or plugged into the wrong spot.
Click to expand...
 
Not vacuum, but pressure. Boost "pushes" on the waste gate diaphragm which in turn opens the flapper valve in the turbine housing, controlling how fast the turbo spins and therefore boost.

And yeah, its possible he has an important vacuum line disconnected or a hole in an intercooler coupling, or even loose end tanks on the intercooler.

Edit: oops, didn't read your post before I replied. I was replying based on the email notification which said you were confused. ;)

:cheers:
 
Check the turbo hoses. The one on the intake of cold side likes to crack and melt on the bottom where you cant see it.

Build a $10 leek down tester and presurize the system to 12 PSI listen for leeks.

I posted this next bit a while back.

meeki007 said:
So you will need a pipe cap 2 inch.
stainlesssteel-fitting-cap.jpg
and a threaded pipe rod end
stainlesssteel-fitting-nipple.jpg


Now i had the 1/8 in drill and tap so i did not need to buy this and i had some brass fittings laying around. The filler valve and the regulator was 10 bucks. put them in my taped threads. and you'll get this minus the duct tape.

31299_1386362351614_1608712812_867024_5847672_n.jpg


now i have so much tape because it was made to fit volvo spec hose and i needed to make it fit on the end of my 3 inch custom intake hose not the 2 and 1/2 inch standard volvo.

Make sure you put 2 wraps of duct tape on the pipe first then at the far end of the pipe put two wraps of some wire around the end to create a lip.
31299_1386370751824_1608712812_867030_1995357_n.jpg

Tape now until it just fits with some rubbing in the hose. Make sure to create the lip on the end of the pipe with wire. If you do not do this the sucker will blow off the end of the hose with some good force as you create some psi in the system.

with some 2 inch pvc hose cuppelers you can even use it to test an inter cooler.

<object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/xk30gxcyocY&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/xk30gxcyocY&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>

<object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/fSIEhRN4FgI&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/fSIEhRN4FgI&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>
Click to expand...

Other Ideas have been posted.
Waste gate
BOV/CBV
 
Thanks for all the replies so far!

I went out and took some pictures and edited them in paint to help show you how everything is set up. Here's what the lines look like now. The manual boost controller knob also seems to have no affect on anything at all... turn it all the way up or down, doesn't seem to change anything

Image1.jpg


Image2.jpg
 
OK, so your car still has the stock CBV (compressor bypass valve on circled in yellow in last pic) and an aftermarket BOV..

Run a vacuum hose from both the BOV and the CBV to the intake manifold. T them if you want/need.

For simplicity I'd eliminate the MBC for now and just run a line from the compressor housing nipple to the wastegate. This should put you back to "base" boost for the time being so you can figure out what's going on..

Have you thoroughly checked ALL the rubber intercooler pipe couplings? ie remove them from the car and check them over completely. Also check the intake hose to the turbo (between the MAF and compressor inlet) because as mentioned, they can crack (most often on the bottom or where the PCV hose connects to it) and throw off your AFRs.
 
944Turbo said:
OK, so your car still has the stock CBV (compressor bypass valve on circled in yellow in last pic) and an aftermarket BOV..

Run a vacuum hose from both the BOV and the CBV to the intake manifold. T them if you want/need.

For simplicity I'd eliminate the MBC for now and just run a line from the compressor housing nipple to the wastegate. This should put you back to "base" boost for the time being so you can figure out what's going on..

Have you thoroughly checked ALL the rubber intercooler pipe couplings? ie remove them from the car and check them over completely. Also check the intake hose to the turbo (between the MAF and compressor inlet) because as mentioned, they can crack (most often on the bottom or where the PCV hose connects to it) and throw off your AFRs.
Click to expand...

Ok so then it's set-up the way it should according to what you stated. I'll go out and try eliminating the manual boost controller and go over my piping again under some really bright lights. How would I adjust my wastegate, or should I need to?
 
From the looks of it also you have green top injectors which I believe are stock because thats what my 740 has. That turbo as well doesn't looks much larger, you would have to look at it but it looks about the same size as factory.

As far as finding a solution it sounds like you have a couple problems. Have you checked to make sure you have a c clip on your wastgate actuator and the actuator rod is hooked up to the wastgate underneath the turbo. When I got mine it was completely off so the factory boost gauge thing would go to just before the yellow and flutter because it wasn't building any boost. I would probably try to run all your vacuum lines factory as previously recommended for now until you get it sorted out.
 
g3mccotter said:
From the looks of it also you have green top injectors which I believe are stock because thats what my 740 has. That turbo as well doesn't looks much larger, you would have to look at it but it looks about the same size as factory.

As far as finding a solution it sounds like you have a couple problems. Have you checked to make sure you have a c clip on your wastgate actuator and the actuator rod is hooked up to the wastgate underneath the turbo. When I got mine it was completely off so the factory boost gauge thing would go to just before the yellow and flutter because it wasn't building any boost. I would probably try to run all your vacuum lines factory as previously recommended for now until you get it sorted out.
Click to expand...

Just went out and checked the wastegate for that arm rod and c-clip. Turns out my dad and friend had noticed the rod wasn't attached and put it back up on it the other day and said something about a clothes hanger down there wrapped around a hose... So I noticed the hose was meant to take place of the c-clip and put it on the end of the actuator rod where the c-clip was meant to go. I also pulled out the O2 sensor and found this....

O2sensor.jpg


As you can see, the black wire looks like it's had surgery done to it before... and it's hanging on by a thread. I have a feeling this may be causing the drastic throttle cut and stalls after you release throttle when the motor is under a load.... Hopefully..

My dad also made a tool to test out the inter-cooler piping which just seals to the end of the pipe and compresses air inside, then you just look/listen for leaks. I'll test all of my piping further once I get a fresh O2 sensor on there.

Thanks again guys for all the help! This really is a great and very helpful community :)
 
meeki007 said:
Check the turbo hoses. The one on the intake of cold side likes to crack and melt on the bottom where you cant see it.

Build a $10 leek down tester and presurize the system to 12 PSI listen for leeks.

I posted this next bit a while back.



Other Ideas have been posted.
Waste gate
BOV/CBV
Click to expand...

Hey thanks for the idea!! I looked today for a psi gauge that would work at my local Harbor Freight tools. Couldn't find any gauges that only went to 60psi... Lowest one went to 160, and it'd be kind of hard to pressurize and read the gauge to be precise. I'll be looking out to make this though. For now my dad has come up with something that just pressurizes the piping without the gauge, which I'll have to be careful with.
 
Looks like you are sorting this out.

You really don't need the CBV and the BOV.
I would blank off the BOV, people have reported rich spikes with this type of setup.
See if your CBV not leaking, you can just blow and suck on the hose to it.
 
^^ What he said. If everything else seems to check out (obviously you'll want to replace that 02 sensor, that thing's rough looking), it's very possible your BOV or even CBV is leaking. BOVs can be pretty finicky if they aren't setup correctly.
 
ive not seen a setup using a CBV and BOV....seems redundant to me. I would also suggest removing the "T" and running the vacuum line directly to the CBV and block off the BOV for now.

also, on your MBC pic....
where is the MBC itself?
all I see is a "Y" fitting between the turbo and wastegate actuator. where does that line go???
A MBC should have a line from the turbo going to it....and then a line leaving the MBC and that goes to the wastegate actuator.
 
Just had an idea... Has the car never boosted correctly since you've owned it?

Have you messed with the vacuum lines on the BOV at all? I'm wondering if you've got it connected wrong and it's holding open the BOV?
 
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