Turbo_Sol93

I have an issue with my 93 del Sol. Here is the setup...

LS Vtec built @ 9:1 Compression (b16 head)
RamHorn Exhaust Mani
Precision 5431 Journal Bearing Turbo
3" Turboback exhaust
Stock b16 Intake Mani and Throttlebody
Electronic boost controller
Tial MV-R Wastegate
Precision 1000cc injectors
Walbro 255 Fuel Pump

Here's the issue, I had a problem running a -4 oil line to the turbo and was only boosting 10psi max. I called precision and they said to replace with a -3 oil line. After doing so, the turbo spooled almost instantly and hit 15 psi with no problem. It holds for a few seconds then hits the boost kill. On the dyno the shop was hitting 15 psi and started dropping all the way to 6psi as the rpms went from 6000 to 8000rpms. The shop has no idea what is wrong with this picture, they have built cars with the same setup which held 15 psi and beyond. The shop factored out the electronic boost controller and the car still does the same thing. I had an issue with the Tial MV-R wastegate when Tial had a defect in my serial number. It has been fixed but I still think that this maybe the issue.

Has anybody had an issue like this? Any recommendations as to why this is happening? PLEASE HELP!

Turbo_Sol93

Anyone have any idea? Could this be a fuel pressure problem? I have just replaced the FPR with an adjustable Blox one (but only set it to where the old adjustable one was set, no fuel pressure gauge was used...) and the car runs rich when cold and at 1700-2000 rpms. It is intermittent in the idle and when car hits vtec when warm the rpms drop to 200 and shoot up to 1000. Sometimes the car completely dies.

Muckman

iTrader: (2)

Are you claiming too much oil pressure was restricting your turbo before to 10psi? Ive never heard that before... It makes me wonder if the turbo CHRA is damaged already, causing your current issues.

A couple points - are you running a static duty cycle on the boost controller through out the run? Boost taper on smaller turbos is common. 9psi taper is extreme however. Ive also seen restrictive air filters and intercoolers cause large boost drops at high rpm.

Turbo_Sol93

Muckman: The -4 was putting too much oil into the turbo according to precision. This is a brand new turbo and the -4 was ran for break in of motor for about 1000 miles. During this time Vtec was only hit maybe twice. There is no air filter on it however the intercooler is small... It is an ebay intercooler from my last turbo kit. The thing that really gets me is that in March the built motor blew due to improper build. When the motor blew, it was at 305hp at the wheels. Since then I have not only had the shop rebuild the motor but also put a 3" exhaust vs the 2.25" exhaust that was used then the motor blew in March. Now the car is putting maybe 265hp to the wheels with no sign of going up... I want to be sure that the intercooler is the problem before purchasing a bigger one. The shop also thought that the precision turbo is the issue however there is no shaft play (other than the little bit from the factory. Any other ideas? I appreciate the help.

Turbo_Sol93

Dimensions of the intercooler currently on the car is 27"x7"x2.5". Think this could be the problem?

Muckman

iTrader: (2)

Yeah the large feed is allowing too much oil pressure. Check for oil in the charge pipe immediately downstream of the compressor outlet. That will tell you if the turbo oil seals are blown or not. And inspect the intercooler for blockage. Pressure testing the intercooler/piping system for leaks would be smart too.

Turbo_Sol93

No Oil in the Hot Side of the Intercooler piping. The intercooler is a bit dirty from my previous setup. I remember the shop saying that the intercooler gets hot quickly because of its small size. Do think that overall this could be the problem, the intercooler size? How should I clean the intercooler? Brakeclean? I can pick up a fairly larger intercooler for under $100 on ebay. 31x12x3" would be the right size to go with?

Muckman

iTrader: (2)

Yes heat can cause boost pressure to drop - although I didnt think it would be that much. What are your peak IATs during a pull on the dyno? Yes you can clean it however you want just make sure its dry after. That sounds like a small size intercooler but probably adequate for your power. The problem with ebay intercoolers is their fins are **** and they dont flow well internally.

Turbo_Sol93

I just talked to a buddy and he said to check out the BOV. I have a cheap ebay one and he has seen this kind of boost loss with even an HKS BOV. He recommended a TiAL Q 50 BOV to use with my setup. Any thoughts on this being an issue as well?

Motionek55

If you have access to a smoke machine first thing you should do is rule out any type of boost leak weather its a bad hose somewhere or just something is not come undone. Second i know someone of having kind of the same issue, his transmission speed sensor was faulty and put the vehicle into fail safe, found that the tran speed sensor starting backing out and vehicle was in fail safe bc it could not read.

Turbo_Sol93

Yea the shop checked for boost leaks and there was nothing. Im going to get a new intercooler as well as a new BOV. I checked the trans sensor and that was ok as well. Thanks for the feedback. If anyone else has thoughts please help! Thanks!