Boost problems

[hplar]

Ok this is going to be a long one but I need help. I bought an 87 GN from my uncle who added parts with no rhyme or reason. The problem I have been chasing for a year is when you punch the car the boost goes to 20lbs and almost immediately drops to 10. It slowly builds back up and then drops..... then builds and stays. It feels like its going to pull like a frieght train and then fags out. It pulls like hell up top but the fluctuation in the middle is terrible. Here is what the car has on it.

Stage 3a turbo from atr
33 lb injectors
cold air intake..atr
7th injector
pitbull chip..atr
3" down pipe..atr (does the turbo need to be ported to match)????
2400 stall converter
2 1/2 stainless exaust with free flow cat
upgraded plenum plate
Double pumper gas pump..atr
Like I said I have been haunted with this for a long time. I replaced gaskets, changed vaccum lines, ect. ANY help would be greatly apprreciated!!!

R

[Keller]

Sounds like he just got out his wallet and went crazy in the ATR catalog...in the mid '90s.

- Not sure what the "Stage 3a turbo' really is, but someone else may know. Depending on age, it may be a TA48/TA49 equivalent.

- The 7th is likely not necessary if you had decent capacity injectors. i.e. ~36 lbs. Old technology.

- Pitbull chip is not modern technology

- Does the downpipe have an external wastegate on the pipe? Is it purple? If so, this is likely your entire problem. Again, a dated piece.

- The ATR double pumper was overkill for a normal car. I've seen cars belch black smoke from having too much fuel from those things.

The boost problem may be due to a stuck or leaking wastegate. As for the rest of the combo, I think it probably just needs updating. This looks like a case where removing parts, plus replacing one or two with better modern ones, and good tuning (with a scan tool!) would help the car and make it perform better.

[hplar]

Keller,
Thanks for replying. According to ATR the Stage 3A is an 800 CFM turbo. ] ATR says I should have 36lb injectors with that turbo and then have the chip re programed. The wastegate is on the turbo with the rod going to the puck. So whats the deal with the Chip? Should I get a new one or what? Again any help would be great.

[Keller]

- See http://www.gnttype.org/techarea/pict...de/turbos.html 800 cfm = TA49. Just remember that is what your turbo probably should be called.

- The 7th is definitely not necessary. Remove and put a regular vacuum block in its place.

- Get a set of 36 lbs. injectors to replace the 33's. Which may not flow 33 lbs/hr.

- Pitbull chip can probably be replaced be something else. i.e. Red Amrstrong, Jay Carter, TurboTweak, etc. Or use an updated Pitbull if you wish, matched to the new injectors.

- The downpipe wastegate or actuator may be sticking. Or the system which activates it may have a problem. You may need some help with this one.

- The ATR double pumper could probably be replaced with one more modern pump. i.e. Walbro 340 or Red Armstrong XP. Less power usage and switching, and better fuel control.

That is my opinion. For what it's worth, my car has basically the combination I am describing. A very classic setup.

[hplar]

Thank you for taking the time. I will definitly use the info.

[edv2]

I had the same problem with my car, ended up being the Atr external wastegate was both stuck closed and had a hole in the diaphram! Good Luck!

Ed V.

[hplar]

That is great because I have a new one on order. I laughed because they are all on back order so it must be a common problem!!

[hplar]

I put a new wastegate on the car and it made a big difference. It dosent drop as far down and is much quicker to build back up. Is it normal to see some fluxuation in boost in relationship to RPM or shifting?? I am much happier but still would like to see it pin at 18-20 and stay there until I take my foot out of it. Any help would be great

[Keller]

Shifts likely have some effect. "How much" is the question. And how you have it plumbed will effect it, too. See http://www.gnttype.org/techarea/images/wstgate.gif for a suggestion. Good hoses need to be used, too. Silicone is probably best.

[hplar]

I took it to the local strip the other night and it only ran in the 14's with all the parts I listed on the thread. The air was terrible but needless to say I was very disappointed. So....I'm taking your advise and buying the 36 lb injectors and taking off the 7th injector. ATR will reprogram the chip for only 30 bucks for the new injectors. Will it make a difference to them if I have a 2500 rpm converter in the car? Should I tell them that for when they program the chip? The car would go halfway down the strip and loose boost and then build it back and pull like hell up top. I want to cry. Hahahaha. It is so frustrating. Any little bit of info helps. I need reassurance im on the right track. Thanks.