boost control problems

[trailinjake]

Hey guys.. new to site and recent purchase of my GN bout 10 monthes ago...
Long story short... bought the car.... blew head gaskets and ring land... rebuilt it and having few problems
After the rebuild, brought it to a mustang dyno to tuneand having a few problems
When I first bought the car, it had 2- 38MM Tial waste gates. 1 off turbo and 1 off cross over pipe down by oil pan. I was told that this set up is "old school" and a single WG would be fine. I took the lower one off, re-plumbed it and got a good base tune up to 4400 rpm and bout 10 psi of boost. starting to tune higher rpm/boost the boost wasnt control-able. stopping and running it on the street it just shoots to the moon....Im letting off at 18-20 psi. I have a green spring (12psi) and a boost controller turner all the way down. I changed the BC and checked the diaphragm for rips...all looks good. when I had both WG installed with the 1st motor, I didnt have this problem. I dont understand the 2 WG thing... never seen it before and everyone I tell looks at me like I have 5 heads!!! This turbo isnt huge...have a 3" DP... I have read guys running stock internal WG having no problems.... What am I missing here??? And what kinda RWHP and 1/4 times should I expect with this set up? How much boost/rpm should I run without launching the crank... I put cremetic head gaskets in...

 

[TurboBob]

post some pics

where are you located, a pair of experienced eyes would probably help.

If you are near Bowling Green, Ky, then next week is your lucky week.....


Bob

 

[trailinjake]

post some pics

where are you located, a pair of experienced eyes would probably help.

If you are near Bowling Green, Ky, then next week is your lucky week.....


Bob

Thanks for the offer Bob but I'm 60 Miles north of NYC... Ill take a picture of my downpipe/wastegate tomorrow and post. Im at the point of re-installing the lower wastegate and trying to adjust the boost. I hate to be that guy....only guy running 2 waste gates!!!

 

[SHADOWII]

WELCOME PILGRIM!!!
You won't be "that guy", there are several set-ups like that, at least there were the last time I was brousing in BG. Do a search on here and you will probably find a thread or two on a discussion of them.
The use of the 12# spring may be the problem. It may be needed to get to 28#s of boost but not controllable at lower levels. You can try a lesser # spring to see if you have better control. You still should be able to get 21-23#s out of it.

 

[turbo96max]

maybe the single 38mm is not up for the job on its own, not venting enough?? maybe time to get a 44mm or larger??

 

[dr_frankenstein]

something doesnt sound right, post up a pic of the exhaust design... i bet theres a bottle neck somewhere.

 

[bison]

Remove the spring from the wastegate and see how much boost it makes at the highest rom you will ever run it at. Report back.

 

[larrym]

boost controller being used is the gate plumbed correctly? I had the lines reversed the first time I hooked up my external gate never had heard detonation before

 

[trailinjake]

Thanks for all the help. I had to make my dyno appt so I re-installed the second waste gate and the boost was controllable. I was told by Cottons that my 3" DP and 38mm WG is too small and I need a 3 1/2 DP with 46 or bigger WG. Everything is plumbed properly. On the dyno, I made 412 RWHP at 17lbs of boost. Have plenty of injector left but pressurizing the motor too much with the higher boost #'s. I never deleted the PCV tubes. created oil leaks at the valve covers and my oil weight was too light.... Tuner said i should run 10-40 or 15-40 oil. I used 5-30 and was smoking a bit pushing her hard. I want to increase the boost to 24lbs or so (depending on injectors) but gotta get oil leaks fixed 1st. I guess I have to search PCV deletes and maybe larger valve cover breathers. Any other tricks or suggestions on this topic??? Really looking for 500 RWHP. Will that get me into the 10's? Where will 420 RWHP get me with drag radials/good launch??

 

[Ttype6]

When I first bought the car, it had 2- 38MM Tial waste gates. 1 off turbo and 1 off cross over pipe down by oil pan. I was told that this set up is "old school" and a single WG would be fine.

Definition of old school-Something that has worked well for a long time.