Stock Sy only running 3lbs of boost

[datsunguy]

Alright Guys...I have an issue. First, the truck is all stock underneath the hood aside from an electric fan. I had GN Northwest do all of the maintenance and modern upgrade work to include plugs, cap, wires, rotor, vaccum lines, EGR delete, new FPR and all of the tuneup necessities performed.

When I put an aftermarket guage in the truck it only showed 10psi. The truck seemingly ran at full strength but as of late has fallen short in power. I have good oil PSI and from an NA presepctive, the motor is running tip top. From a boost persepctive it sucks. The mystery is this: The truck will run 10psi (per guage) for 2-3 days then only run at 3psi (per guage) the next. This latter is happening more and more as I drive it and I have not been at full power for some time now. I checked all the hoses, connectors etc and nothing seems amiss.

What is the issue? A bad turbo? A bad turbo solenoid? This is very frustrating to say the least. Any thoughts on things I should check and run diagnostics on. I have no engine management software so I am just going off my mechanical skills alone. I can't believe the turbo would be bad as if it were, I wouldn't produce any boost..Please help!

Thanks - P

 

[datsunguy]

Re: Stock Sy only running 3lbs of boost

Finally found a couple of other posts:

Could it be a bad boost solenoid? My wastegate doesn't appear to be stuck becasue I do get the whoosh back to the airbox. Maybe the solenoid is the "tell" for the intermittent boost levels. I highly doubt the turbo has broken fins. The truck has never been abused but who knows.

 

[GM TURBO]

Re: Stock Sy only running 3lbs of boost

Knock

 

[datsunguy]

Re: Stock Sy only running 3lbs of boost

Knock what....On wood? hahaha

I don't hear anything coming form the motor and there is a knock sensor correct? Why would knock restrict boost? Does the ECM compensate somehow so no damage is done? Please elaborate.

 

[powercat6]

Re: Stock Sy only running 3lbs of boost

From http://powertuneplus.com/syclone/howto_stock13s.shtm#part1_tuneup

"Without question, the #1 performance killer of Syclones and Typhoons, is Knock Retard.



This means the engine's computer is detecting potentially engine-damaging detonation and as a safety precaution, it is reducing the total timing advance (just like turning the distributor) by the number of degrees under "Knock Retard". These trucks only operate about 14* total spark advance at WOT in stock form, so if your knock sensor is pulling 8-10* timing from Knock Retard, your truck could be running with a total of only 4 degrees of timing! This will absolutely kill performance.

Yes, tuning these trucks requires the use of a laptop computer. Yes, even a stock truck! Even though it's a 1991, it's still a relatively high tech fuel injected vehicle that simply won't "tell you" what is wrong with it by "seat of the pants" alone. The truck's factory stock "computer" (or E.C.M.) constantly analyzes every main aspect of the engine's operation and will gladly transmit it to a laptop computer while running, and you can review this information at home with software that tells you 10 times more than simply "listening for knock" or "cutting plugs" ever will.


With a chart like this, you can immediately tell how the drivetrain (engine and transmission) are operating, and pinpoint performance bottlenecks. A good way to sum up the majority of performance tuning is simply: by eliminating performance bottlenecks one by one! Solving a crippling problem like a case of severe Knock Retard is like unleashing tons of free horsepower..."

Get Datamaster or TunerPro installed on a laptop.

 

[dgoodhue]

Re: Stock Sy only running 3lbs of boost

It can't be the boost control solenoid. It only has the ability to limit your boost to 8-9 psi if everything else is working properly.

Maybe the flapper is sticking open. Maybe one of your intake clamps isn't fully tighten and leaks sometimes (perhaps dependent on heat)

 

[datsunguy]

Re: Stock Sy only running 3lbs of boost

http://powertuneplus.com/syclone/howto_stock13s.shtm#part1_tuneup

Excellent Article. Now all I need is someone with more expertise than me and datamaster to give me a hand. Without data logging software, I now understand getting to the bottom of the issue would be impossible.

I live in Seattle...Any local yokels with a love for beer and pizza avaialble?

 

[neildemo]

Re: Stock Sy only running 3lbs of boost

I had Similar Problems, Try running better Fuel. I run 20 percent e85/80 percent 93. Truck runs great also changed boost solenoid. You either have severe knock or bad Solenoid. I also added a boostvalve on my truck and run 19psi.

 

[Chest Rockwell]

Re: Stock Sy only running 3lbs of boost

http://powertuneplus.com/syclone/howto_stock13s.shtm#part1_tuneup

Excellent Article. Now all I need is someone with more expertise than me and datamaster to give me a hand. Without data logging software, I now understand getting to the bottom of the issue would be impossible.

I live in Seattle...Any local yokels with a love for beer and pizza avaialble?

I'm a cheap date, Paul. I've got datamaster and tunerpro on my laptop. Doesn't seem to be a whole lot of local interest in the BOP show at Bremerton Zav posted about a while back. Got any plans this weekend?

 

[datsunguy]

Re: Stock Sy only running 3lbs of boost

I'm a cheap date, Paul. I've got datamaster and tunerpro on my laptop. Doesn't seem to be a whole lot of local interest in the BOP show at Bremerton Zav posted about a while back. Got any plans this weekend?

I am leaving Sunday for a business trip but can meet up with you Saturday to diagnose a few things and drink some brew. I don't believe it is a severe knock issue but am sure there is some...Software will tell the tale...Give me a shout 206.617.0649 and we can coordinate times.

 

[0966Sy]

Re: Stock Sy only running 3lbs of boost

I highly doubt the turbo has broken fins. The truck has never been abused but who knows.

Doubting and assuming wont diagnose anything, Turbo makes the boost, so the engine runs well. So you shouldnt have any problems spooling the turbo. So inspecting the turbo and air intake sounds like a good place to start. Check for broken or damaged fins or excessive play. Check the wastegate vacuum lines, use a pressure tester to check your wastegate on the truck, check for what psi it begins to open and if it holds pressure. Diagnostic software is not going to fix your problem for you.

 

[cat-vi]

Re: Stock Sy only running 3lbs of boost

I'm a cheap date, Paul. I've got datamaster and tunerpro on my laptop. Doesn't seem to be a whole lot of local interest in the BOP show at Bremerton Zav posted about a while back. Got any plans this weekend?

I wish you lived in my area:tup:

 

[datsunguy]

Re: Stock Sy only running 3lbs of boost

Doubting and assuming wont diagnose anything, Turbo makes the boost, so the engine runs well. So you shouldnt have any problems spooling the turbo. So inspecting the turbo and air intake sounds like a good place to start. Check for broken or damaged fins or excessive play. Check the wastegate vacuum lines, use a pressure tester to check your wastegate on the truck, check for what psi it begins to open and if it holds pressure. Diagnostic software is not going to fix your problem for you.

I have plans to check the turbo and as stated in my original post, all the vaccumm lines and rubber hoses are brand new and I just inspected them again last night. The manual part is not in question, it is tuning the truck and having the proper software to aid in the process. All software does is help pinpoint issues and once issues are uncovered you still need to turn a wrench. The one thing I have never done on the truck is dissasemble the turbo but it looks pretty self explanatory but I must ask...any special tricks or techniques recommended?

I took another listen to the truck while running and I have to tell you..I can't hear a damn knock anywhere and I used my stethescope. I was underneath it, in it, practically laying on the damn engine and it runs almose as quiet as my cars. I ran it up to 3k+ and nothing. If it is a knock or a detonation issue....it is a real subtle one. That's the part that has my scratching my head.

 

[dgoodhue]

Re: Stock Sy only running 3lbs of boost

I took another listen to the truck while running and I have to tell you..I can't hear a damn knock anywhere and I used my stethescope. I was underneath it, in it, practically laying on the damn engine and it runs almose as quiet as my cars. I ran it up to 3k+ and nothing. If it is a knock or a detonation issue....it is a real subtle one. That's the part that has my scratching my head.

Most trucks aren't going to have detonation (knock) at idle or reving the engine in neutral. It will be in boost under load..

 

[datsunguy]

Re: Stock Sy only running 3lbs of boost

Good Point....I didn't think of that.

 

[GM TURBO]

Re: Stock Sy only running 3lbs of boost

The reason I went with knock is because it changes. But, I do agree with Dave that it's something basic. Turbo to IC hose or IC to TB hose.

 

[datsunguy]

Re: Stock Sy only running 3lbs of boost

If you had GN Northwest do the basic maintenance work, why aren't THEY doing this troubleshooting as well? If you don't feel confident to change your own plugs and wires, you're in over your head trying to figure this one out, it seems. Which is backed-up by some of your comments in this thread.

They did more than basic maintenance work, they replaced seals, half shafts etc. When I first bought the truck I wanted someone with experience to tune it since I did not have the supporting software. Also, I travel quite a bit and time at home is not spent underneath vehicles anymore although I still like to dink around. I don't think these trucks are overly complicated. As long as I listen to input, research and read, it's just a matter of diving in. This is why I am asking questions to help pin point issues.

 

[datsunguy]

Re: Stock Sy only running 3lbs of boost

I still think you need outside help, but I had a couple of thoughts after re-reading your initial post. Something is affecting the ability of the turbo to "pump air". Either on the inlet, or the outlet. 3 psi is very low and below the minimum base-point. Something basic is wrong.

Does this truck still have a cat converter? If so, pull it off and test drive it.
Does this truck have non-stock inlet air ducting that may be collapsing under boost? "Cobra" elbows are notorious for this.

Ok, great advice. I will take a closer look at the plumbing.
Yes, the truck has its CAT in place, no muffler, 3" straight pipe.
I will take a closer look at the ducting tonight to make sure it is not collapsing.

Thanks for the help and guidance fella's.

 

[RMcCourt]

Re: Stock Sy only running 3lbs of boost

"Without question, the #1 performance killer of Syclones and Typhoons, is Knock Retard.



.

Whenever I read this, it always strikes me that maybe tooky put the comma in the wrong place. "Without question, the #1 performance killer of Syclones and Typhoons is Knock, Retard." Fixed.

 

[datsunguy]

Re: Stock Sy only running 3lbs of boost

UPDATE:

I triple checked all of the vaccuum lines and plumbing. Everything looks great - it is brand new. All of the ducting and lines in and out of the turbo are clean and routed correctly. All fittings are tight and there are no leaks up top.

I had Chest Rockwell pop over last weekend to give me a hand as he has the DM software. We hooked it up and gave her a spin. The software showed 6.7 PSI with minimal to no knock at WOT. We now had our base metrics to begin troubleshooting. To start we swapped the Boost Relay and Boost Solenoid out of his Ty into my Sy to eliminate the simple things. We drove it after and there was an immediate improvement. Gauge went from ~3-5 to ~10. The datamaster showed minimal knock and my boost via DM was 12.6. This proves my guage is a bit off but is the least of my worries. I purchased a new relay first and saw no improvement. This of course pointed directly to the solenoid. I got a OEM AC Delco solenoid off Amazon for $29.95. I installed it yesterday and voila, back to what says 10 on the gauge but is really 12-13. We did not check anything else as the ignition system parts are all new and correctly installed.


However, the truck still seems to hesitate before it gets to optimum boost. Is this the typical turbo lag? I drove another members TY and the power seemed to be a bit more immediate. I was following another post here recently and will probably yank the cat to see if that is the culprit to the lost 3 PSI. In my mind I doubt it but it is easy to take on and off so it is better to elimiate that as a cause.

The waste gate opens and closes as deisgned but may need adjustment...I just don't know seeing I am very new to these rigs. This weekend I am going to fix my small oil leak, hotwire the IC and maybe even yank the bed off to see if I am running a stock FP. I am going to be ordering the WALBRO and I already have a brand new adjustable FPR.

Anything else I may have missed guys? Thanks for the continued support!