stock boost

[Mistascott]

Some people say 15 lbs. from the factory, but I only get 12 at WOT on my gauge. I've been told that is normal since the gauge measures at the intake and not at the compressor, where it is higher. :fragez:

[jmidolo]

Some people say 15 lbs. from the factory, but I only get 12 at WOT on my gauge. I've been told that is normal since the gauge measures at the intake and not at the compressor, where it is higher. :fragez:


Are you using the stock gauge for this reading? If so, it could be 12 or 18...they suck. Wanna say it was 13.7lbs stock or something. Does anyone really run factory boost levels anyways? ;)

[GrndNatnl]

... When your car knocks like crazy on crappy pump gas, yes. Mine spikes to about 17, so I just have it settle at 15 on the street.

I think stock boost level in the 86/87 cars was said to be right around 14 psi. Like 13.7 or 14.2. I've seen all different ratings. Every car is different.

[turbodave]

The truth be told, and all the missinformation aside, the factory boost really was 12#. Irrigardless of what some folks "may have experienced".

[1badTTA]

The truth be told, and all the missinformation aside, the factory boost really was 12#. Irrigardless of what some folks "may have experienced".
Everything I have read said it was 16.5psi...................OOPs, I have a TTA.

Maybe that is why they are quicker...LOL

[Mistascott]

I have an aftermarket gauge. I wouldn't even TRY to watch the knight rider light on the stock gauge. I have read various places that the 86 GN had 14 PSI stock and the 87 had 15 PSI stock, but I only get 12. I am about to do some modding and I want to make sure everything is perfect before doing so. :kopfkratz

[HairDrier]

Is your wastegate adjustable or is it totally stock? Is the rod to the exhaust housing threaded and two piece or one smooth rod?

If it is adjustable, and you have the rod tightened, your actuator is probably shot and you need a new one

[jmidolo]

Turbodave, everything I've ever read I've never heard 12.

Good thing on the aftermarket gauge. With the age of the car, things wear, your wastegate spring could be fatigued and not able to hold the puck closed as tight any longer. Or it could have been changed at one time and the rod is adjusted down a little. Not a huge deal....

[Mistascott]

I have heard of 12, so I don't discredit turbodave. But I have also seen 15 in Car and Driver articles and in the famous Shootout article. I was wondering if we lose boost between the turbo and the intake manifold because I've heard theories that pressure drops going through the IC. I guess a better question to ask is, how much boost can I safely run stock on 93/94 octane? :albert:

Wastegate is stock to my knowledge...I will take a look to be sure. This was originally a California car and maybe the original owner turned down the boost on 91 octane :fragez:

[jmidolo]

Ihow much boost can I safely run stock on 93/94 octane? :albert::

Depends what chip you are running. I have a Jay Carter chip and run 18# with no knock. If you're running an older higher timing chip like a Dynotech, or a Kenne Bell, ATR Pit Bull or something, you'll never run that much cause the timing it too great to turn up the boost.


This was originally a California car and maybe the original owner turned down the boost on 91 octane :fragez:

If it's original, then it's non adjustable, it is possible it was changed and turned down for the reason that it was a CA car. 91 octane..yuk! I feel for them guys!

[Mistascott]

Is your wastegate adjustable or is it totally stock? Is the rod to the exhaust housing threaded and two piece or one smooth rod?

If it is adjustable, and you have the rod tightened, your actuator is probably shot and you need a new one


I have one smooth rod :laugh:

I don't know what I'd do with a threaded two piece :SHOCKED:

[HairDrier]

Sounds like your actuator may be bad. Tell your wife you are going to exchange your smooth rod for a two piece :lickit:

I wouldnt get a heavy duty one because often they wont let the boost stay below 18-19#. Postons has a good adjustable stock replacement.

Take the elbow off and look at the ring around the wastegate hole. It will tell you if your puck is sealing properly. Once you look at it it will make sense. This is a perfect time to port the elbow, it takes about an hour or two. Its a lot easier with a die grinder. Just open the area that meets the turbo and get rid of the "lip". Then smooth the short side radius and you are good to go

[87natty]

The condidtion of the wastegate solenoid has a little to do with it too. And all those 17 year old vacuum hoses.

[Mistascott]

I replaced all my hoses, so I think that ain't it. Either it came with 12 from the factory or my actuator is bad. I will let you all know which it is.

Maybe I am just not flooring it hard enough :burnout:

[jmidolo]

How many miles on the car? Are you still running the stock chip?

[Mistascott]

100K and stock chip.

[jmidolo]

100K and stock chip.

Yea, chaulk it up to fatigue and get that shit mod'd...you'll be amazed how bad the stock chip sux.. :)

[Mistascott]

Yeah, I am getting an adj. wastegate anyway.

[HYBRID-T]

"Boost pressure is regulated by an electronic wastegate, where a pulse width modulated solenoid is used to vary the boost rate and maintain maximum tolerable boost pressure based on continuously varying engine and environmental conditions. Boost peaks at 15psi and pulls back to 13psi after 2 seconds"

HOT ROD MAY '86

don't know if that's a reputable enough source, but it is obvious you need to make some changes in both chip and actuator to get better control of that 'BEAST' of a motor.

ADAM

[Mistascott]

Thanks, Adam. Mine is peaking at 12 and then going down to 10 after two seconds. I can't believe I've been missing 3 lbs. of boost and 30 hp!! I feel deprived!

I was thinking of three possible scenarios:

1 -- chip is bad
2 -- fuel pump is getting tired and so ECM is adjusting boost to the lower fuel psi?
3 -- bad actuator

[ozzy]

we have a 25,000 mile car out in the shop that is fully stock.I put a direct scan in it to
see what the boost level was on this car. I got 14.7 on the ds at wot.

Hope this helps,

Pudd'n :fragez:

This one does have new boost lines and a new wastegate soloniod.Did'nt see the boost drop any but I did not record so I was paying attn to my driving!!!!

[HairDrier]

Dont forget to change the valve springs and timing chain. Yours are both shot for sure

[Mistascott]

Is your wastegate adjustable or is it totally stock? Is the rod to the exhaust housing threaded and two piece or one smooth rod?

If it is adjustable, and you have the rod tightened, your actuator is probably shot and you need a new one


I spoke too soon without checking it in daylight. IT IS ADJUSTABLE :rock:

It is threaded on the end. When I checked the first time I just groped the rod in the dark :lickit: So, I think the California owner decided to turn down the boost on the low octane gas -- smart. So now I just have to turn it up gradually and watch for knock.

[mgmshar]

This is a difficult question to answer. According to the Buick Service Manual...

Under the "Wastegate/Boost Pressure Test" Procedure section, it says that you should hook-up a pressure gauge to the boost actuator and use a vacuum/pressure pump to apply pressure to the actuator. At 13-1/2 psi, the actuator should move .015 inches. So, how much boost is that in the intake manifold?

Under the next section (Road Test Procedure), here's what it says...

1. Tee compound gage (a.k.a. pressure gage) into tubing between compressor housing and boost gage or MAP sensor switch with sufficient length of hose to place gage in passenger compartment.
2. Disconnect hose at wastegate solenoid and plug.
3. Conditions and speed limits permitting, perform a zero to 40 or 50 mph wide open throttle acceleration.
-Boost pressure as measured by the compound gage during road testing should reach 13-14 psi.
-If this does not occur, replace the actator assembly and test for proper calibration.

There are two problems with this. First, you are disconnecting and plugging the hose to the wastegate solenoid, which increases boost. Secondly, there is no tubing between the compressor housing and boost gage/MAP sensor. There is tubing that goes from the intake manifold to the MAP sensor (for the dash boost gage), and there is tubing that goes from the compressor to the actuator. Which one are they talking about?

I guess GM didn't want to give away what boost pressure in the intake manifold should really be...

:fragez: :fragez: :fragez: :fragez: :fragez:

Well, at the least, you have a procedure for checking your actuator...

[LikeMy6]

12#'s is correct on the factory setting. Some people experienced some boost creep and might have seen higher.

[copp]

12#'s is correct on the factory setting. Some people experienced some boost creep and might have seen higher.
Bought 2 new turbo ts in 87. Both would spike to about 15 than drop to about 13. One felt a lot faster than the other but both would boost about the same. Completely stock at that time.Not boost creep.

[HairDrier]

I dont see the significance of what the stock boost is. Who runs stock boost? The point is to run as much as possible without knock

[jmidolo]

You took the words outta my mouth Bob. I don't know anyone running less than 16-17 anyways. Get a good chip, tune it, and crank up the boost.