North American Turbocoupe Organization



What boost pressure
Scott Mabe Offline
Member
#1
The factory boost gauge on my 87 hasn't worked since I bought the car. Yesterday I bought a vacuum/boost gauge that I temporally installed before work this morning. I done a pull and boost gets up to about 16lbs in every gear. I was trying to see what other 87's were doing. As far as I know the only mods are a k&n and turbo muffler duel exhaust.
1987 Turbo Coupe
1988 Thunderbird parts car/ possibly street/strip car
1990 F-250HD 460ci
2001 Pontiac Montana (wife's ride)

-PLEASE FORGIVE TYPOS, I USE SWYPE ON MY PHONE-
Reply

Pete D Offline
Administrator
#2
A stock 87 would, in theory, deliver 15 psi in 1st and 2nd and less in the upper 3 gears. A stock 88 is suppose to give 15 psi in all gears but there are some qualifiers in that.

One way around all the limitations is an aftermarket boost valve such as the Gillis valve. There are many brands and a few types.

If your 87 is yielding 16 in all gears, it probably has an aftermarket boost control device of some sort. Have you seen any evidence of that?
Pete Dunham


Reply

Scott Mabe Offline
Member
#3
It does have a small valve on the line going to the wastegate actuator. The way it is set up is to bleed off some pressure to atmosphere when opened, but I have always kept it closed because until now I had no idea what boost I was making.
Everything else is stock boost controller. I even tried flipping the fuel switch and it didn't change the amount of boost.
1987 Turbo Coupe
1988 Thunderbird parts car/ possibly street/strip car
1990 F-250HD 460ci
2001 Pontiac Montana (wife's ride)

-PLEASE FORGIVE TYPOS, I USE SWYPE ON MY PHONE-
Reply

Scott Mabe Offline
Member
#4
After work I was going to open the valve to bleed off some pressure and noticed the hose going to factory boost control was off of the compressor side of the turbo. I hooked it back up and now only 10 psi until about 4000. From what I saw boost never went above 16 with it disconnected. I always run 93 octane, and I've never heard any detonation. Any thoughts on just disconnecting wastegate?
1987 Turbo Coupe
1988 Thunderbird parts car/ possibly street/strip car
1990 F-250HD 460ci
2001 Pontiac Montana (wife's ride)

-PLEASE FORGIVE TYPOS, I USE SWYPE ON MY PHONE-
Reply

Pete D Offline
Administrator
#5
"Any thoughts on just disconnecting wastegate?"

Short story made shorter: Don't.

Uncontrolled, turbos will continue to build boost until something stops it, like a blown head gasket or a broken ring land or a cracked piston or a chipped valve or a bent crank. The waste gate is your control.
Pete Dunham


Reply

Scott Mabe Offline
Member
#6
I guess I have to pop the hood again to see whats going on. Last time the hose come off the compressor outlet the boost would hit 16 psi and wouldnt go any further. Today is the first time I've drove the bird since we got 20+ inches of snow.
On the way home the last time I drove it the snow had just gotten bad. There's a slight hill right before my house that I barely made it up. 4th gear feathering the throttle all the way up. It did hit the rev limiter once but I didn't think anything of it.
Now this morning I was on the interstate and noticed the turbo kicking in earlier than normal. So just checking I gave it full throttle for a second and boost shot up to about 20 psi setting off the over boost alarm.
Last time the the hose came off for the wastegate it would stop at 16 psi every time, any ideas what could make it build more boost now? I haven't had a chance to look under the hood yet so I don't know if it is the same hose or not but my first break im going to go look.
1987 Turbo Coupe
1988 Thunderbird parts car/ possibly street/strip car
1990 F-250HD 460ci
2001 Pontiac Montana (wife's ride)

-PLEASE FORGIVE TYPOS, I USE SWYPE ON MY PHONE-
Reply

Scott Mabe Offline
Member
#7
Ok so I checked and the same hose came off again, the hoses are starting to deteriorate so I guess I will replace them. I am still puzzled why last time 16 psi was all it would make with the hose off and this time it's easily hitting 20 psi. I haven't changed anything since the last time it happened so why the change.
1987 Turbo Coupe
1988 Thunderbird parts car/ possibly street/strip car
1990 F-250HD 460ci
2001 Pontiac Montana (wife's ride)

-PLEASE FORGIVE TYPOS, I USE SWYPE ON MY PHONE-
Reply





Users browsing this thread:
1 Guest(s)



Theme © iAndrew 2018 - Software MyBB