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...If you want quiet, "civilized" you need to move up to the 911 water cooled series, fully spec'ed out and with a can of spray undercoat in each wheelwell those can be like riding in a Lexus LS400.

And...the GO like....!

Old 10-11-2010, 11:49 AM
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19 mpg (US Gallon) with a stock 930 on the highway driving like an old man.
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Old 10-11-2010, 11:55 AM
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I get about 20 on the highway when being civilized (i.e., 4 gear @ 65mph). 14.2-14.4 AFR.
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Old 10-11-2010, 12:04 PM
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What makes them POP, pop, ...?

I believe EFI dose not do this as much as fuel is more shut off on de-acceleration. CIS on the other hand dose not seem to have any provision to cut fuel.

Is it an AFR and or ignition timing that on overrun is to far off that it can not be ignited fully in the combustion chamber or at all.

Then the unburned fuel hits the hot exhaust and maybe even gets some added oxygen from up the tail pipe and bang.

Dose the de accel valve add air such that a better AFR is achieved or dose it more accurately help keep the metering arm from over-swinging such that it creates an un ignitable lean spot.

Might disconnecting the Vac-Retard at the pot help keep spark advanced with throttle lift such that ignition is not as late for more complete combustion in the combustion chamber and less unburnt fuel making it to the exhaust area?

Never really got my arms around this except that a more quiet exhaust helps cover it up.

I to like the effect most the time.

Sorry, got carried away again.
Old 10-11-2010, 01:34 PM
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Hello friends.
Originally, my friend was helping me find a normally aspirated 911 of the same vintage. He has
one himself so we kinda knew what we were looking for. Then, this 911 Turbo came up. It was in
very good (not mint) condition and honestly, the price point was right. The past owner told me that
gas milege wasn't a concern to him, but I didn't expect 12MPG! If I was getting 15/16 I would have been happier. I don't drive with a leadfoot, but I do like the odd kick to trigger the turbo (It is fun).
I still love the look and performance of this car, but with the gas milege as it is, it's hard to justify it as a daily driver.

So, from what I am gathering from everyone, here's what I need to check with my mechanic:
1) decel valve - reconnect?
2) AFR
3) C0%
4) aftermarket muffler?

Again, Thank you so much for all your advices and welcoming to the 930 club! I look forward to talking to you all in this group!
Old 10-12-2010, 06:28 AM
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Fuel mileage in stop and go traffic in the city with these cars is horrible, even if its properly tuned. I'm lucky to get 400km (240 miles) out of a tank (=12 miles per US gallon) when doing my typical city commuting. On the track its even worse as you get into the boost a lot more frequently.

Out on the highway cruising I get double the mileage that I do around town.

The popping sounds are always there - with a stock muffler you can't hear them but with an aftermarket muffler with no baffling etc. you get to hear all of it

Never heard of a Kool Vue exhaust system - if you need a great system talk to Brian (RarlyL8), and if you want to go back to a stock muffler I might sell mine as I never expect to use it again.
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Old 10-12-2010, 06:52 AM
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Or if your THAT concerned about a daily driver, a turbo isn't a really good choice. These cars have marginal A/C, generally poor gas mileage (compared to modern stuff), tight ergonomics, no real luggage space, fairly high cost of maintenance compared to non-turbo models, etc. They are really toys when you get right down to it. If you are really hung up on 3-4 MPG, maybe you need a prius? or a carrera of the same vinatge if you want an 80's air-cooled Porsche.

Also, the decel valve will not improve mileage much in my experience, just gets rid of a lot of the decel popping. If you want those miles back, you need a bone-stock OEM replacement for your whole exhaust system, and if you have an non-stock turbo, you will need to go back to the original.

Pick up a clean 1st gen miata for a couple grand and use that as a daily driver. Mine used to SIP gas, got 2 weeks or about 300 miles on a tank.

Last edited by Groovie Ghoulie; 10-12-2010 at 06:56 AM..
Old 10-12-2010, 06:53 AM
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Add checking the CIS pressures. System pressure, control pressure, and on boost control pressure.

Ignition timing and function. Mechanical Advance, Vac Retard and boost retard working.

Spark plugs for balance.

The following would be nice to:

Injectors for pattern and opening pressure.

One of the best things you can do to ensure you do not have a lean cylinder or two that you are adjusting around it to do a balance test. This requires checking injector quantities at the injectors in the car with the metering plate manually advanced.

If you are getting a fair amount of lag between shifts I would also check the Compressor Bypass Valve operation. I believe they are supposed to be open at cruse reducing turbo drag and exhaust back pressure but I could be wrong.
Old 10-12-2010, 07:28 AM
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My '89 930 does pretty well on the highway-from Arizona to Laguna Seca and back got 22 at 85 cruise.
Old 10-12-2010, 09:29 AM
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I'll find out how my EFI 930 does this weekend. I would say easily over 20mpg on the highway
Old 10-12-2010, 09:40 AM
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Yeah, mine is also EFI.
Old 10-12-2010, 09:55 AM
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I've never cracked 12mpg and that is using the 8 buck 101. I drive mine in the boost let me think, all the time. Always wondered if I took it on a trip what it would get.
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Old 10-12-2010, 10:04 AM
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ive done three trips to north carolina from west palm beach 20 22 mpg until some idiot in a mustang or ricer wants to show the old guy in the old car what a real car he thinks he has
Old 10-12-2010, 01:16 PM
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I'm late to the show but can add that I agree with what others are suggesting.
A fuel tuned 930 can achieve 15mpg city/21+mpg highway. I do this mod all the time.
Popping on decel is enhanced by a non-functioning decel valve. Push in the clutch and it instantly goes away. Same for light throttle.
Loud mufflers have no baring on fuel mileage and expose all the noises hidden by the stock unit.
Never heard of a Kool Vue but that's what you get when the decel valve is disabled and fire shoots out your tailpipe!
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Old 10-12-2010, 01:45 PM
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Quote:
Originally Posted by RarlyL8 View Post
I'm late to the show but can add that I agree with what others are suggesting.
A fuel tuned 930 can achieve 15mpg city/21+mpg highway. I do this mod all the time.
Popping on decel is enhanced by a non-functioning decel valve. Push in the clutch and it instantly goes away. Same for light throttle.
Loud mufflers have no baring on fuel mileage and expose all the noises hidden by the stock unit.
Never heard of a Kool Vue but that's what you get when the decel valve is disabled and fire shoots out your tailpipe!
Ok I am hearing that my stock muffler is what is preventing me from hearing that wonderful whine the turbo puts out? ..................
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Old 10-12-2010, 03:31 PM
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Well, yes and no. Turbo whine sound level is dependent on a few things. One is the type of turbo you have and another is the type of muffler. Generally speaking an early boosting turbo such as the K27S will have a more audible whine than the 3LDZ when driving around town off boost with a free flowing muffler. My street muffler pretty much muffles whine while the non-packed Hooligan version lets it all out. Zork tubes of course hold back no noise at all. It really adds to the driving experience to hear those sounds, gets your blood pumpin'. I get complemented all the time that folks love hearing the car drive up or away.
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Old 10-12-2010, 03:57 PM
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Well kids I don't know, being old and deaf....particularly in the higher frequencies from too many years of not taking care of my hearing. I can't hear my damn turbo for the life of me, it gets buried in the "whine" of the cooling fan, the roar of the muffler, all the other glorious air cooled sounds emminating from behind. The funny thing, though, is that I can usually hear it in the various YouTube videos. Go figure.....I guess I don't need audible confirmation that the thing is going round and round; the feel of several G's tells me all I need to know.

But I can say this: At 36 degrees this morning, all that dense air, man does she run strong!!! Too busy holding on to think of listening for what I know is going on back there.
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Old 10-12-2010, 05:07 PM
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I do love that video and love the whine of a turbo used to hear it all the time when I had a thunderbird turbo coupe maybe when I can run a little bit more boost later it will become more apparent I also may get a zork and valence so I can get the full experience but I have a few other items to take care of first.
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Old 10-12-2010, 06:10 PM
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Quote:
Originally Posted by gsmith660 View Post
I do love that video and love the whine of a turbo used to hear it all the time when I had a thunderbird turbo coupe maybe when I can run a little bit more boost later it will become more apparent I also may get a zork and valence so I can get the full experience but I have a few other items to take care of first.
In your T-bird the whine was being created front of your ears, your were "traveling" toward it.

Early morning dense atmosphere might result in a more open wastegate, non-muffled wastegate, and that night be the "extra" noise source. Also, a denser atmosphere will of course carry sound a bit better.

And of course a video camera's microphone, behind the source, will pick up those sounds moreso than the actual driver will hear.
Old 10-13-2010, 06:44 AM
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not sure how this post got on this subject but the new smaller exhaust housing on my car makes a higher pitch whistle compared to the bigger housing.

Old 10-13-2010, 08:09 AM
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