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modified turbo car vs modified n/a car - fuel economy?
Topic Started: Feb 7 2010, 11:55 PM (1,900 Views)
Dallas


assuming the same mods:
fresh bored block, N/A compression ratio
economy cam, +10 gear
upgraded exhaust

which should I expect to get better economy in stock-like form? with multiport fuel and a better intake manifold with a different ecu, I'm not sure what would work the best. obviously the turbo ecu isnt technically meant to run the high comp motor, it has been done (by myself too) without any detonation effects. it probably all comes down to the ignition timing map, which I intend to push as far as possible (stock block has knock sensor)

what are your thoughts? may come up with a turbo car for stupid cheap that needs the work I want to do anyways, done to it. so I will probably impulsively jump on it to build the MPG car.... but on a turbo ecu?

assuming I never hit 0.1psi once over the course of a full tank, and driven in the same manner, do you think I have an upper or lower hand?
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Cobb
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You should run preminum with the turbo.

Having said that, there is a guy who added a turbo to his insight and it depends on driving style how it effects fuel economy. If I remember correctly he gets better fuel economy on grades than before the turbo and lower on flat out driving. Its only a few mpg, so well worth the upgrade.
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Dallas


I sold a bunch of t3 stuff to a guy who wanted to do pretty much this. I forget his name... hmm, hope he chimes in on his results, this was a year ago..... he was the guy who put the taller springs in his mk4
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rmcelwee
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People always say that adding a turbo to a Miata will get you better mileage. Mine drops to around 10-15 MPG when I turbo it for obvious reasons <G>.

I've always speculated that a turbo Miata (we are talking a small turbo like a T25 or something like that) is dropping the rich from the factory fuel mixture down and that is where the added MPGs come from. I have no way to confirm this.
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starscream5000
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Got 70 MPG?

Yeah, most people who install a turbo will not see a MPG gain just for the reason that most of them like the feel/sound of the turbo spooling and the BOV venting ;)
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chads4dr


Quote:
 
starscream5000
Yeah, most people who install a turbo will not see a MPG gain just for the reason that most of them like the feel/sound of the turbo spooling and the BOV venting



:lol Like Me? :D
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mwebb
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FOG

my Audi A4 5speed 1.8 with stock turbo gets 34mpg on the highway at 65 with AC on low
my VW passat with v6 2.8 4sp automatic non turbo gets about 32mpg on the highway at 55 to 60 with AC on low

both in the summer , both with top tier premium fuel , both cars are "fast" and accelerate quickly if needed .

both have multiple knock sensors both weigh about the same and have similar CD s on the body
the Audi is a quattro

my daughter has a fwd toyota matrix with 1.8 na and automatic
it gets around 25 to 28 mpg commuting at 55 to 65 mph , which also weighs about the same as the others .
a school administrator with 2 toddlers , she does not really pay much attention to fuel economy .

so
in my limited experience
a smaller engine with a turbo in the same weight car with similar CD will provide better fuel economy


Edited by mwebb, Feb 9 2010, 10:56 AM.
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Dallas


starscream5000
Feb 9 2010, 08:37 AM
Yeah, most people who install a turbo will not see a MPG gain just for the reason that most of them like the feel/sound of the turbo spooling and the BOV venting ;)
which is why my swift could get 10-14mpg city, or 25 (my absolute best, driving it off boost the whole time)

:p

I just got home with a 91 t3, im thinking about keeping it turbod and not converting it, but im still torn as for maximum economy. the t3 manifold looks very restrictive, even my ported one on the shelf. and sure, it needs to have a small enough opening to make use of velocity to spool, but I almost think if driven the same and modded the same, the n/a one might have an advantage. especially if the compression is left low
Edited by Dallas, Feb 9 2010, 11:52 AM.
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Cobb
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My tacoma was blown, but the fuel was at 15-1, it really leaned out. Seems this is a know issue, however the super charger gives more power for HP and TQ.

No matter how I drove it, lazy like or lead foot it got 18mpg. Towing a vw fox wagon I got 16mpg.

Having watched cars on the dyno one day, those that made power smoked like a mutha and were pushing 12 to 1 fuel ratios.

The hybrid owner I am referring to is using like 4psi and keeps it in the max tq rpm for accelerating. As long as you limit your boosting, I dont see any problems or much decrease in fuel economy.

Maybe mwebb can fill in here or the z24 guy. Someone said something that the mroe fuel you run, the less need for octane vs advance is needed. So, if you run it rich, you can crank the timming and burn lower octane fuel vs running it lean with high advance you need high octane fuel.
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rmcelwee
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Cobb
Feb 9 2010, 11:46 PM
Having watched cars on the dyno one day, those that made power smoked like a mutha and were pushing 12 to 1 fuel ratios.

Someone said something that the mroe fuel you run, the less need for octane vs advance is needed. So, if you run it rich, you can crank the timming and burn lower octane fuel vs running it lean with high advance you need high octane fuel.
The high HP cars were running rich but that isn't a requirement for high HP. If you drop the fuel and use water injection to get the temps down you can run safely and more efficiently. They were using the extra fuel to cool the combustion chamber to reduce detonation. They could have achieved more HP with the water injection but it is an extra expense that most people do not want.
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starscream5000
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Got 70 MPG?

rmcelwee
Feb 10 2010, 02:13 AM
Cobb
Feb 9 2010, 11:46 PM
Having watched cars on the dyno one day, those that made power smoked like a mutha and were pushing 12 to 1 fuel ratios.

Someone said something that the mroe fuel you run, the less need for octane vs advance is needed. So, if you run it rich, you can crank the timming and burn lower octane fuel vs running it lean with high advance you need high octane fuel.
The high HP cars were running rich but that isn't a requirement for high HP. If you drop the fuel and use water injection to get the temps down you can run safely and more efficiently. They were using the extra fuel to cool the combustion chamber to reduce detonation. They could have achieved more HP with the water injection but it is an extra expense that most people do not want.
You'll also see people using Methanol as well, otherwise known as windsheild washer fluid :thumb
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Cobb
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You guys think I can run 4psi or less of boost for a turbo for my insight? Its a 1.3l sohc dsi engine, 2 plugs per cylinder without preminum fuel using water or wiper fluid?

Id love a few extra HP and having a turbo hybrid, but I hated buying preminum fuel.
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starscream5000
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Got 70 MPG?

Not worth it IMHO if you're wanting to skimp out on higher octane. You'll have to have some way for a computer to spray the Meth into the motor once it see's positive pressure.

Snow makes meth kits that can do this, but I do believe that they're costly and in the end you may be better off just using a conservative tune with maybe 89 octane.
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Cobb
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Whats a conservative tune? Isnt 4psi conservative? I seriously need like 15hp. I know I might be able to squeeze 5 out of a kn filter and axle back.
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starscream5000
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Got 70 MPG?

What I mean by conservative is in regards to your Air/Fuel Ratio's. The Methanol has a very high octane rating (over 100 if memory serves me correctly), this is used to keep from detonating while boosting.

How would you plan on boosting a 4psi? Most wastegates are preset to 6-7 at the lowest...
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