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Old 07-25-2001, 01:01 PM   #1
Skunkeye
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Default Less power?

A simple question: if one were going on a long highway trip, would it be possible to set a boost controller for less than stock boost (say, 7 psi) and improve gas mileage? I know this would reduce power, but for highway cruising at sane (80-90 mph) speeds, not much power is needed anyway. Any ideas?
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Old 07-25-2001, 02:04 PM   #2
IMPREZIV
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The only way I know of adjusting boost is with the use of a boost controller. I can't speak for all of them, but as far as the HKS EVC-4, it won't let you lower the boost to anything less than stock.
Pete
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Old 07-25-2001, 02:26 PM   #3
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No... wouldn't do you a bit of good...

At cruise you are not boosting anyways....


Jorge (RiftsWRX)
www.ProjectWRX.com
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Old 07-25-2001, 02:31 PM   #4
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Default no boost?

Is there really no boost developing at 90mph? I'm sure it is not full boost but in my old Saab 900 turbo (which came stock with a boost guage - shame on you SOA), there was a moderate amount of boost at anywhere above 60 mph or so.
My guess is that reducing max boost might help if you were driving alternating between 60-90 but not at all if you were able to maintain a constant speed.
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Old 07-25-2001, 03:15 PM   #5
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I would bet that at a constaint speed around 80mph you meaby made five PSI of boost.
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Old 07-25-2001, 03:29 PM   #6
JaMa
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Default Turn it Off

You could always just turn the BC off and the let spring pressure of 6 psi or so control boost.

JaMa
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Old 07-25-2001, 03:45 PM   #7
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RiftsWRX is right. Your not boosting at speed, so dont wast your time.

Skunkeye, not to sound like a jerk.... but...
dont cruise at 90mph if you want to save gas...
it aint gonna happen!

55mph will save you gas (plus you can still mess around with Mustangs if you leave your boost alone!)

A Rule to remember....
never mod your car to be slower!
Ever!

You got it!?????
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Old 07-25-2001, 07:56 PM   #8
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Yeah, I know, slow down = save gas. It's just that I'm coming from a BMW that got 30+ mpg at 80-90 mpg, and the WRX is only giving me 22-23 at that speed... Just trying to find a nice compromise between actually getting where I'm going in a reasonable amount of time and wasting gas...
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Old 07-26-2001, 10:53 AM   #9
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Wink Less power

Keeping it out of the boost while getting to 80 MPH is what'll save your gas mileage.
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Old 07-26-2001, 11:22 AM   #10
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22-23 MPG seem a little low, even at 80-90MPH. A lot of us are getting 28-29 MPG on the freeway, at about 70-75.

I just installed my boost gauge a few days ago, but I can tell you that cruising at 80-90, you won't be boosting at all. Might be even running vacuum. Be gentle on your "go" pedal and you should get decent mileage.

-Ray
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Old 07-26-2001, 12:10 PM   #11
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rkkwan:

Thats pretty suprising since at 80 your doing 3200rpm roughly. And at 90 you're probably over the 3500 point so I'm pretty sure some boost would be there even with the light load of 5th gear.
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Old 07-26-2001, 12:21 PM   #12
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This depends a whole lot on engine load, and how far your foot is in the gas. You can actually be in vac even at 7000 rpms. At 90mph you can be in boost very quickly if you like, but your going to be cruising in vac.


-Nathan
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Old 07-26-2001, 12:46 PM   #13
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Yup Nat is right.
Easy on the acceleration and you`ll stay out of the boost for the most part.
I think my mpg is pretty good for the amount of hp I have. If I wanted great mpg I`d have bought a honduh.

I like the fact I can get mid to upper twentys mpg and still be able to smoke Cobra Mustangs and drive year round.

Bill
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Old 07-27-2001, 11:21 AM   #14
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Did a little experiment this morning. 80mph, 5th gear, with cruise control, flat road, I read between -.01 and -.02 MPA. So, it is running at vacuum at that speed.

The cruise won't go up to 90mph, but I tried as smooth as possible on the gas, and it runs about 0 to -.01MPA.

-Ray
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Old 07-27-2001, 05:45 PM   #15
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28-29!!!!!! What kind of tail wind are you guys driving in? Is there any relation between gas mileage and humidity? It's 90% down here and I use 93 octane fuel. The best mileage I ever got was just over 25 running about 75-80 most of the time and no racing. I filled up in Texas and drove to Louisiana without stopping for gas or restroom. My usual mileage is about 18-19. Yes, it's completely stock w/7000 miles on it.
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Old 07-27-2001, 05:53 PM   #16
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I agree, at best I get 24mpg between 75 and 80. Are you sure your speedo doesn't read in Km's?
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Old 07-27-2001, 06:03 PM   #17
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Quote:
Originally posted by metoo
28-29!!!!!! What kind of tail wind are you guys driving in? Is there any relation between gas mileage and humidity? It's 90% down here and I use 93 octane fuel. The best mileage I ever got was just over 25 running about 75-80 most of the time and no racing. I filled up in Texas and drove to Louisiana without stopping for gas or restroom. My usual mileage is about 18-19. Yes, it's completely stock w/7000 miles on it.

I dont even want to think about what MPG i am getting. I have my foot in it too much now that the exhaust system is on.

-Nathan
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Old 07-27-2001, 09:58 PM   #18
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Well, I did observe 28+ mpg on a couple of trips from Rhode Island to Canada, at about 75 mph. And I've read here on some "gas mileage" post about getting 29 mpg.

I drive my car very aggressively usually, and in mixed highway/local, I'm getting 21 mpg pretty consistently. Note that I seldom use A/C up here, so 18-19 for you guys are not too far off.

BTW, I'm still the low MPG champ. 9 mpg on a race track. Still haven't seen any numbers lower than that.

-Ray
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Old 07-27-2001, 11:12 PM   #19
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Quote:
Originally posted by gossamer_monster
I like the fact I can get mid to upper twentys mpg and still be able to smoke Cobra Mustangs and drive year round.
Wow! What mods do you have to be able to smoke a cobra?
Doug
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Old 07-28-2001, 12:19 AM   #20
BrownKiler
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A stock Cobra is not all that powerful compared to a modified WRX (Car and Driver times, except Imprezer):

Cobra: 320 HP, 0-60 in 4.8, et 13.5 @ 105
Cobra R: 385 HP, 0-60 in 4.7, et 13.2 @ 110 ($55K limited edition)
Sti 22B: ~300 HP, 0-60 in 4.8, et 13.5 @ 101
Imprezer's WRX: ~340 HP, 0-60 in 4.4, et 12.8 @ 104

You should be really impressed if someone says they can smoke a Z06 Corvette or Viper. Both of those cars run in the mid 12's stock!

--Jason
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Old 07-28-2001, 06:38 AM   #21
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BrownKiler

Would you happen to know the 1/4 time for a late 98-99ish Mustang Cobra SVT?

I beat one running high-13s and was curious if it was car or bad driving.

FYI: stock vs stock... no way a WRX can smoke a Cobra!
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Old 07-28-2001, 03:41 PM   #22
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the 99 Cobra was the one with the HP problem

Many of those owners reported dyno numbers that were really, REALLY low...

98s were the 305hp model...

anyhow, for MPG I get about 23-24, but its virtually all city driving. Or put it this way... in my C5 (and currently, in my girlfriend's 325i) there was a average MPH trip computer... the average speed is about 35-40mph... Its the same route I use in the WRX...

its pretty sad when you think about it... traffic sucks that bad (I am out at off peak hours -- before rush hour and also during lunch)...
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Old 07-29-2001, 02:04 AM   #23
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Hmm...see what a lot of you guys dont understand is that a car like a Z06 or Cobra won't put out those numbers consistently. My friend has a Camaro SS and the car is very hard to launch due to the huge amount of torque it puts to two wheels. I can consistently take 2 car lengths on him right off the line (he catches me shortly after) in my stock Rex. Another important thing to remember is that once you know your WRX, it becomes very easy to get a good launch. And with a few mods and the better launch your Rex should not have a problem with nearly every car on the road. And if all else fails....race them in the rain.

Look at it this way: A Z06 = 13.0 is a great 1/4 mile....with an average driver lets say its a 13.3.

Now you have you're WRX, with lets say TB system, boost set a 16, and air filter. Now you could be running as low as 13.5 if its set up right and you can drive.

Figure it this way...on any given day any car can win.
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Old 07-29-2001, 03:17 PM   #24
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I think gas mileage has a directly related to your driving personality and mood.
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Old 07-30-2001, 07:38 PM   #25
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I'd say my personality is pretty stable, and mood the same as any other time I am in traffic -- irritated, lol!



Quote:
Originally posted by Imprezd
I think gas mileage has a directly related to your driving personality and mood.
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