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937DYTBOI
03-19-2006, 07:31 PM
hey im lookin to get this 87 buick grand national off this guy but the turbo only boost up to 9lbs he says. The engine is not stock i dont know if its another buick 3.8 fuel injected engine or some other engine and it has a bigger turbo than the stock one. I believe it has the original computer with a chip installed. I was thinking the problem may be just to uninstall the chip and see what it does or if the engine doesnt have the proper compression for the turbo itself, i really want the car but want to decifer what could cause this problem before i give this guy this money and be stuck in a a big hole to fix the car. If anybody has any info let me kno;)

pd298
03-19-2006, 07:33 PM
Wheres marley when you need him. He owns a GN. He will be able to help you with whatever you need..

dalucifer
03-19-2006, 07:33 PM
what is the boost supposed to be at?

937DYTBOI
03-19-2006, 07:33 PM
i actually PM him first but i guess hes not online but i was checkin to see if anyone else has any info

937DYTBOI
03-19-2006, 07:35 PM
im not sure to tell u the truth im bout to do a google search

phantom240
03-19-2006, 07:36 PM
9lbs sounds about right for most cars that come from the factory with a turbo.... :dunno:

dalucifer
03-19-2006, 07:40 PM
9lbs sounds about right for most cars that come from the factory with a turbo.... :dunno:

thats what i was thinkin, but he said it was chipped.

937DYTBOI
03-19-2006, 07:42 PM
But its a aftermarket turbo with bigger injectors i forgot to say.

kuijo
03-19-2006, 07:42 PM
don't the wrx evo srt-4 all come with around 15psi stock? or closer to 1 bar

Lunchbocks
03-19-2006, 07:47 PM
what type of boost control does the car have? manual, electronic, is there a control solenoid? gotta find that first, if its an electronically controlled unit (either aftermarket system or factory solenoid valves or something along those lines) then its possible that the aftermarket chip controls the operation of this unit and sets a limit to 9psi

also, determine if the turbo is externally or internally gated, because it could also be boost dependant solely on a interchangeable wastegate spring

937DYTBOI
03-19-2006, 08:10 PM
ok i will check on the boost control. Sorry but im turbo illiterate but im going to learn i know the parts but not really on everything i know whats involved. Whats a good aftermarket intercooler?

937DYTBOI
03-19-2006, 08:21 PM
Well this is what i found off a website on the 87's


Maximum boost was set at 15 psi and the turbo used an electric wastegate. The turbo also incorporated special low drag, dynamic turbine shaft seals, and a built in contamination trap.

RandyJ
03-19-2006, 09:03 PM
Then the turbo he put on probably is internally gated at 9psi. But there are certain things you need to look into. You may not want to up the boost. A PR of 1.61 may be the in peak efficiency island with the turbo selected, as well as providing power is the desired band. Upping the boost may cause problems with flow. Try to find out what turbo it is and we can get you some maps and flow numbers.

And you need to knwoo what you're flowing before you go and buy an aftermarket IC,it would **** to end up losing 4PSI because you chose the wrong IC when you didn't know your numbers, ya know.

pd298
03-19-2006, 09:05 PM
9psi is not that much. SRT-4 come from the factory pushing 13psi...

RandyJ
03-19-2006, 09:06 PM
9psi is not that much. SRT-4 come from the factory pushing 13psi...


The turbo installed on this motor and the turbo on an SRT-4 may be very, very different.

RandyJ
03-19-2006, 09:09 PM
Example being this, a little drastic, but still holds truth to what I said.

T3 45trim @ 9psi
http://turboneticsinc.com/images/compmaps/compmapslarge/T345.gif

Max flow is around 15lb/min

T76 @ 9PSI
http://turboneticsinc.com/images/compmaps/compmapslarge/T76.gif

Max flow is around ~70lb.min.

BIGGG ol' difference.

kuijo
03-19-2006, 10:45 PM
Example being this, a little drastic, but still holds truth to what I said.

T3 45trim @ 9psi
http://turboneticsinc.com/images/compmaps/compmapslarge/T345.gif

Max flow is around 15lb/min

T76 @ 9PSI
http://turboneticsinc.com/images/compmaps/compmapslarge/T76.gif

Max flow is around ~70lb.min.

BIGGG ol' difference.


psi is psi. The guy was asking around how much he thought the engine took stock and we were replying with how much some stock vehicles were running so he could get an idea. And obviously we were close in are assumptions since a stock GN as stated above boosts at 15psi.

marleyskater420
03-19-2006, 10:47 PM
9psi is not that much. SRT-4 come from the factory pushing 13psi...

I run 30psi on stock internals... Its the flow that matters, not the psi.

With that said, his boost should be anywhere from 12-22psi.


Then the turbo he put on probably is internally gated at 9psi. But there are certain things you need to look into. You may not want to up the boost. A PR of 1.61 may be the in peak efficiency island with the turbo selected, as well as providing power is the desired band. Upping the boost may cause problems with flow. Try to find out what turbo it is and we can get you some maps and flow numbers.

And you need to knwoo what you're flowing before you go and buy an aftermarket IC,it would **** to end up losing 4PSI because you chose the wrong IC when you didn't know your numbers, ya know.

If the owner has the gate at 9psi, then he should be slapped. I'd go check it myself and move the puck to make sure it wasn't a retarded owners fault. Then check the vaccum lines to the boost controller, and to the turbo, making sure the boost controller is properly setup. Then check the puck placement on the DP.

IA2
03-20-2006, 01:04 PM
**** u MarleySkater, I was about to chime in with my opinion, but you beat me to it.....lol. It definitely sounds like the problem lies within the vaccum lines/boost controller/wastegate actuator. He could have a 9 lb actuator, and the boost controller may be allowing the actuator to see a full 9 lbs.....which would make the actuator open and the turbo wouldnt build anything more than 9 lbs. If you dont understand what I am saying, do some research on boost controllers to understand how they operate.

heyman421
03-20-2006, 01:12 PM
Boost's just an easier way to read airflow. Someone said boost is boost, which is 1/2 right. 28psi is twice as much flow as 14 psi ON THE SAME ENGINE. 14 psi on a grand national might be 2x as much flow as 14psi on an srt-4. And 14 psi is out of a t4 is the same as 14 psi out of a gt28r but the 14psi out of the t4 might be cooler, but later in the power curve. Comparing different cars, or even the same car with different turbos is difficult. The only way to figure out what's going on with your car is to actually have it looked at.

Spearco intercoolers are great quality, and one with pre-welded endtanks can be had on ebay for under $300. Aren't there people who run their nationals hot, as well? Never understood oldschool tuning.

Anyways, i'd do a compression and leakdown test before anything, just to make sure the headgasket and rings are in good shape before you start adding boost. Shouldn't cost much at a shop, an hour of labor tops, or free if you can find someone with the equipment.


Good luck!

RandyJ
03-20-2006, 04:50 PM
psi is psi. The guy was asking around how much he thought the engine took stock and we were replying with how much some stock vehicles were running so he could get an idea. And obviously we were close in are assumptions since a stock GN as stated above boosts at 15psi.


Sure, the outlet PSI being the same on each turbo means, the outlet PSI is the same, but you cannot rightfully say that 9psi at the outlet of a RHB25 and 9psi at the outlet of a turbonetics Thumper is going to yield the same result, can you?



If the owner has the gate at 9psi, then he should be slapped. I'd go check it myself and move the puck to make sure it wasn't a retarded owners fault. Then check the vaccum lines to the boost controller, and to the turbo, making sure the boost controller is properly setup. Then check the puck placement on the DP.

Are you saying that regardless of the turbo, he should not have it gated at 9psi? Or the stock turbo should not be at 9psi.

spudracer326
03-20-2006, 04:53 PM
don't the wrx evo srt-4 all come with around 15psi stock? or closer to 1 bar


they are 19pounds till 6500rpm then taper to 16 to redline for the evo...i beleave the wrx sti is about the same....the standard 2006 wrx only runs around six with the new 2.5litre motor

spudracer326
03-20-2006, 04:56 PM
with a larger turbo you dont neccesarly need to be running higher boost...but nine doe sound low??

marleyskater420
03-20-2006, 09:19 PM
Boost's just an easier way to read airflow. Someone said boost is boost, which is 1/2 right. 28psi is twice as much flow as 14 psi ON THE SAME ENGINE. 14 psi on a grand national might be 2x as much flow as 14psi on an srt-4. And 14 psi is out of a t4 is the same as 14 psi out of a gt28r but the 14psi out of the t4 might be cooler, but later in the power curve. Comparing different cars, or even the same car with different turbos is difficult. The only way to figure out what's going on with your car is to actually have it looked at.

Spearco intercoolers are great quality, and one with pre-welded endtanks can be had on ebay for under $300. Aren't there people who run their nationals hot, as well? Never understood oldschool tuning.

Anyways, i'd do a compression and leakdown test before anything, just to make sure the headgasket and rings are in good shape before you start adding boost. Shouldn't cost much at a shop, an hour of labor tops, or free if you can find someone with the equipment.


Good luck!

Most GN's are cold air. Duttweiller started with us, and then moved to LS1's..most people don't realize that.

Anyway... most of the DIY LS1'ers and GN guys are starting to use OBX ebay IC's because they work halfway decent, and are cheap...and I think there should be a kit out now for piping as well.

It should take him one pull of the finger to know if the boost is set at 9lbs. Once he does that, then we can start eliminating everything else.


Nooblet- Yes. No GN turbo runs well that low. Most turbos work from 23-40psi, all because of our head restrictions.The stock turbo is set to 13.5psi, and the GNX is 15.

dbhittin
03-20-2006, 10:15 PM
my car is 12psi stock and im runnin 16 now and 20 when i get my fuel pump next week.. and yea it depends on the turbo... 15psi on a T3 *example* will give me more airflow and power than my stock 14b at 15psi.. also depends on your comp ratio.. mine is 8.7:1