QuestionQUESTION: I actually got 4 question.
1)I have 91 740 turbo s/w. I am not familiar with the turbo gauge in where the range should run or what is bad or good. The gauge is white on right and black on left (with a white border). It runs the max 1/8 in the white and at least 1/2 in black. Normally 1/2 in black and at the top at black and white point very rare in the white.
2)What is this about of a bolt under turbo that could be adjusted and if, how?
3)What is the average gas mileage for that Volvo?
4)The Volvo has two muffler. Does it have to have two mufflers if ever needs to be replace?
ANSWER: Marco, with the vehicle off. It should point straight to the middle. The "turbo guage" is actually a vacuum/pressure guage. It is a "relative" indicator of vacuum/pressure. When it's in the white, you are under vacuum, when in the black you are under turbo boost (pressure).
The "magic" bolt you are referring to is the adjustment for the charge pressure regulator or wastegate in U.S. terminology. It determines the point where excess turbo pressure is bled off into the exhaust system to prevent overboosting that will melt down your pistons if it's too high. This is a mechanical system.
You can splice a calibrated vacuum pressure guage into the system to see actual charge settings. I believe factory is around 7-8 psi. There is an electrical pop-off valve that shuts down injection if it sees the turbo boost go too high to protect the engine. The Speed freaks disable the valve or replace it with a higher psi rated one. They then crank the pressue up above 15 psi. They then have to add a water injection system to keep the pistons from melting down. After market kits are available and even twin turbo setups if you truly have the "need for speed" They will shorten engine and transmission life. Especially automatics. But, you do get a heck of a giddyup before it goes.VBG
Average 15mpg city, up to 20 higway with a light foot.
There are lots of performence exhaust systems manufactured for that. Even stainless if you've got the "cake" Try IPD if you want a drool or two.
HTH Mark
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QUESTION: Back too question 1) That helped cause I did not know that. Thanks. IQ? Will it run in the black most of the time? And when will it go in the while? Or how often & how far in the white it should go? (Like at acceleration in the black, Turbo kick in 1/2 in or 3/4 in black)? Hwy driving steady 65 will it should it stay in black or will it end in the white? When will I see it in the white? What is norm range, will I be able tell if I have a Vacuum leak some where in the engine?
IQ? 2)& 3)Done.
IQ? 4)If I keep the same exhaust system when it's time to replace. Could I just run with one muffler? Cause I see a Catalytic converter and two mufflers, one before the rear and one after. Why two not one?
ANSWER: QUESTION: Back too question 1) That helped cause I did not know that. Thanks. IQ? Will it run in the black most of the time? Should not. And when will it go in the while? (Anytime it is under vacuum which should be most of the time unless you are accelerating.) Or how often & how far in the white it should go? (Like at acceleration in the black, Turbo kick in 1/2 in or 3/4 in black)? Hwy driving steady 65 will it should it stay in black or will it end in the white? (Should be in white.) When will I see it in the white? (Anytime the throttle is held steady and not climbing a hill or towing.) What is norm range, will I be able tell if I have a Vacuum leak some where in the engine? (No.)
)If I keep the same exhaust system when it's time to replace. Could I just run with one muffler? (Yes) Cause I see a Catalytic converter and two mufflers, one before the rear and one after. Why two not one? (Too make it quieter.)
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QUESTION: OK Back on Q? 1) You did informed me more on the gage. Thanks! So I have then a miner problem. The reason I was asking about the turbo range is because when I'm driving the needle normally is in the black area very rare is in the white even at steady speed. The max in the white was about 1/8 but comes out quickly. When it goes in the white it barely goes in it, enough to say it went in the white but not for too long. But! I know I have a vacuum leak some ware with the Ac vent. Cause when accelerating or going up hills (blower still working) the blower stop blowing through the vent until coasting or level road. That is were I'm at. I don't see it going in the white, rare, just a little bit and not for long.
Answer Oh boy. I figured that out and posted a detailed fix @ Ramac.com. It involves installing a check valve to keep the vacuum storage tank from going to zero vacuum. The A/C system runs directly off of the tank. Under long boost times IE climbing hills, the vacuum is exhausted from the tank and the A/C vents all close. The blower doesn't actually stop.
Mark
