Where is the vacuum line???

[FAST87]

I just bought a 87 GN and want to turn down the FP a little bit, because it runs a little rich. I heard that I should adjust the fuel pressure with the vacuum line off. Where would that be? I am not very familiar with the car yet, since I bought it a couple days ago. Mods on the car are: PTE-44 turbo, CAS V4 intercooler, poston headers,houston down pipe,42.5lb injectors,adj. FP, Walbro 340 Fuel pump, dual stage alcohol system, and some other stuff. It came with the scan master and the O2, is at like 820 with 22lbs of boost. Runs a little rich for me, where would be a good setting? I heard around 760? Also where would be a good place on line to pick up a set of new springs and shocks?
thanks for any info.
chad

 

[chiken]

the vacume line is right on the fuel pressure regulator. its right next to where you adjust the regulator at.

 

[BLACK6PACK]

Well, you can turn down the fuel pressure or turn up the boost. 22lbs is kinda low with alky especially if you are running a 93 octane chip. What kind of chip do you have?

The vacuume hose should be the one plugged right into the fuel pressure regulator. Pull the hose off right next to where the adjustable regulator screw (the one you turn to lower the pressure).

 

[FAST87]

BLACK6PACK: How high would you suggest to run the boost to? I was thinking about going up to about 24lbs maybe, not really sure. Don't want to blow anything up already. I am not sure what chip it is exactly, i got two chips with the car. One is 93 Octane with 20 degress timing, and the other is 110 with 26 degrees timing. If i turn the boost up, i don't need to turn down the FP correct?
thanks
chad

 

[BLACK6PACK]

Either turn up the boost or turn down the FP to bring the 02s into spec. Turning down the alky a little should also bring down the 02s.

If it were me... I would turn the boost up 1 lb at a time and go for a blast. Best bet is to get on the hwy and do a 3rd gear run. that way you have time to look at the readings and 3rd gear is a much higher load on the car, so if it is going to knock it will do it in 3rd. If you ever run it in 4th (racing a porsche!!) pay close attention, because it will have a greater tendancy to knock in 4th than in 3rd. At 24 lbs of boost I would try to tune for zero knock, and if you see over 1-2* of knock, get out of it. Better to be safe than sorry.

 

[FAST87]

Thanks for all the help, but got a couple more questions. I have been playing with the car for the last couple hours and here is what i got now. 24lbs of boost, the most knock was 1.3 but the FP is still high. How high should the FP gauge read? Mine looks to at like 57lbs. If I turn down the FP will the knock get worse?
thanks
chad

 

[azgn]

if your vac off pressure reads 42 (for example) it should go up 1 lb for each lb of boost, so if ya got 24 lbs boost the fuel pressure should read 66lbs


if I were you, I would NOT be fooling around with 24 lbs boost until you have a feel for what you are doing....things will break at those boost levels.....turn it down to under 20 and do your testing there (particularly running pump gas....do not tolerate ANY knock above 20 psi)

 

[ChrisCairns]

Originally posted by azgn

if I were you, I would NOT be fooling around with 24 lbs boost until you have a feel for what you are doing....things will break at those boost levels.....turn it down to under 20 and do your testing there (particularly running pump gas....do not tolerate ANY knock above 20 psi)

That is the BEST advice so far in this thread. I would even go so far as to suggest you turn the boost down further and start to learn about these cars while running stock boost levels. Read everything you can in the tech section of GNTTYPE.ORG and go back and read all the tech on this board. Learn where all the parts and pieces are on your car and what each does and why it does that.

Or you can continue with the high boost and eventually blow a head gasket or worse.... then get pissed and depressed when the local mechanic screws up the rebuild.

These cars are very finicky....and can give an amazing amount of pleasure if you like acceleration....but they are like high strung race horses which must be taken care of wisely.

Chris

 

[JToups386]

Chris is correct too! You said your O2 reading was at 820? If that is at WOT, then why are you trying to lower it? I never want to run less than 790, and am usually very satisfied a little above 800, simply for the peace of mind that I'm not hurting the car. I have popped numerous head gaskets, broken ring lands on pistons, and various other catastrophes over the years; from the mere fact of running too lean. Yes, you don't want it to be slobberingly "fat", but I would not be too concerned with anything in the 790-820 range, as long as the car is not nosing over. Remember, by the time you sense the detonation, it's too late. You will already have damaged or blown something more often than not.
Follow the boost calculation formula listed by AZGN, as it is a long proven working equation. Also remember, whatever you've set your fuel pressure to be, the pump should be able to maintain that pressure all the way through your run. ie if you're set at 66psi WOT, then the pump should stay steady at 66psi, and not fall off until you let off the throttle. BE CAREFUL! or you'll be looking like this -----> Enjoy...

 

[FAST87]

Yeah I really don't know what I am doing with this car yet so I already turned the boost down to 17lbs. 820 on the O2's was at WOT. I was gonna turn it down but it seems to run good where it is. Plus I would rather run a little rich then to pop something. Thanks for all the help. Now i just have to do some tech reading for this car.
later