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Guest Message by DevFuse
 

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Took a test drive in a Forester XT this morning.


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72 replies to this topic

#1 LameRandomName

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Posted 18 September 2003 - 04:18 PM

The check engine light was flashing rapidly and the salesman said that the car hadn't been through some sort of preparation process yet. I dunno about all that.

But I'll tell you this...

The power increase was noticable, especially at highway speeds, and the cruise control wasn't practically useless the way it is in my 2000 Forester, but that ain't no 13.8 second 1/4 mile car.

I doubt it's even in the 15's.

#2 Guest_lothar34_*

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Posted 18 September 2003 - 04:30 PM

Was it an auto or manual?

#3 wrxsubaru

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Posted 18 September 2003 - 05:01 PM

My dad test drove one, a maunule. I was with him. The forester was fast, faster than my friends supra, thats running 12 psi, probley around 300 horse and 320 + pounds of tork.

#4 LameRandomName

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Posted 18 September 2003 - 08:21 PM

Originally posted by lothar34
Was it an auto or manual?



Auto.

But, taking a guess at what you may be getting at, it wasn't slow because of the auto.

#5 crash613

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Posted 18 September 2003 - 09:32 PM

I test drove a XT Turbo when the Toledo dealer first got them. All they had was automatic, and i had told the dealer i would never buy an auto. But we were both so excited that they were finally in, that i went in and took one for a spin.

The first thing i noticed, after the dealer told me that there "was no turbo lag like the WRX auto," was that there was turbo lag. I had never driven a turbo before, but i could surely recognize it. I think that would drive me crazy. I was empressed with the speed and pickup.

I ended up buying a XS PREM because of the whole No moonroof with manual on the XT. Pure bullcrap. marketing blunder if there ever was one.

I would like to get back there one day and drive a manual XT. maybe someday, but since i have my XS now i dont think that will happen anytime soon.

Mike

#6 wrxsubaru

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Posted 18 September 2003 - 11:11 PM

Autos really seem to make turno lag alot more pronounced, there seemed to be almost none, with the 5spd. My dad test drove a auto wrx, and a manule, the auto seemed to have huge amounts of turbo lag, while the maunle had some.

#7 Guest_lothar34_*

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Posted 19 September 2003 - 12:57 AM

Auto.

But, taking a guess at what you may be getting at, it wasn't slow because of the auto.



Are you sure? The 5-speed has a really low 1st gear. That's part of the reason it's so quick from a standstill.

#8 duane b

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Posted 19 September 2003 - 12:06 PM

Originally posted by wrxsubaru
My dad test drove one, a maunule. I was with him. The forester was fast, faster than my friends supra, thats running 12 psi, probley around 300 horse and 320 + pounds of tork.



Dude, is there an emoticon for "Blowing smoke up my arse"???

#9 LameRandomName

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Posted 19 September 2003 - 02:53 PM

Originally posted by lothar34
Are you sure?



Yes.

And actually, a turbocharged motor should be FASTER with an auto.

#10 Guest_lothar34_*

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Posted 19 September 2003 - 04:46 PM

Yes.
And actually, a turbocharged motor should be FASTER with an auto.



Really? Where'd you hear that?

#11 99obw

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Posted 19 September 2003 - 05:31 PM

Originally posted by LameRandomName
Yes.

And actually, a turbocharged motor should be FASTER with an auto.



First off let me say that I don't know one way or the other. It does make sense to me though. You can really hold your foot to the floor, so the boost should be good.

#12 LameRandomName

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Posted 19 September 2003 - 06:43 PM

Originally posted by lothar34
Really? Where'd you hear that?




I'm trying to decide how I want to answer this question.

You do know how a turbocharger works, right?

#13 LameRandomName

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Posted 19 September 2003 - 06:48 PM

99 -

The salesman was trying to tell me that the car might not be as fast as it should be because it hasn't been tuned yet.

Honestly, I don't know.

The only thing I'm certain of is that the XT that I drove would probably run in the 16's.

#14 99obw

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Posted 19 September 2003 - 07:28 PM

Tuned? Huh? Sounds like BS.

#15 wrxsubaru

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Posted 19 September 2003 - 08:20 PM

duane b, what do you mean.

#16 Guest_lothar34_*

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Posted 19 September 2003 - 08:22 PM

Originally posted by LameRandomName
I'm trying to decide how I want to answer this question.

You do know how a turbocharger works, right?



Yes. And transmissions and torque converters and clutches and all that good stuff.

When you say "FASTER" do you mean faster from a standstill or faster like top speed?

http://www.cars101.c...rester2004.html

#17 LameRandomName

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Posted 19 September 2003 - 09:03 PM

OK, quicker.

A turbocharged engine should be quicker with an auto than with a stick.

#18 Guest_lothar34_*

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Posted 19 September 2003 - 10:12 PM

Originally posted by LameRandomName
OK, quicker.

A turbocharged engine should be quicker with an auto than with a stick.



I don't wanna get in a pissing contest here, but I've never read or seen anything that makes me think that an auto is quicker than a manual.

You can't rev up an auto into the fat part of the powerband before you launch it without really hurting the torque converter. And if you don't rev it like that, the converter is still sucking some of the power until it locks up.

The ratios and the number of gears favor the manual too. Every gear in the 5-speed is shorter than the 4-speed. Even OD.

#19 Hodaka Rider

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Posted 19 September 2003 - 11:25 PM

Interesting thread.
BTW, all road tests that I have seen in recent times have showed manual turbo'd cars to be quicker than the same car with an auto.

#20 LameRandomName

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Posted 20 September 2003 - 09:27 AM

A turbocharger works on exhaust back-pressure, not exhaust flow.

The smaller a turbo is, the faster backpressure builds up enough to spin the impeller. The bigger the turbo, the higher the engine has to rev before it if pushing out enough exhaust to create backpressure.

When I use the word "spinning" in this context, I don't mean any spinning, I mean spinning fast enough to create pressure in the intake that is higher than normal atmospheric pressure.


Once a turbo begins spinning it creates it creates pressure in the intake tract.
If the exhaust pressure suddenly drops, as during shifts with a manual transmission, the intake pressure acts as a brake on the impeller, dragging it's speed down very rapidly.

With an automatic transmission the exhaust backpressure is preserved and you don't create "mini-lags" with each shift.

Now, you could abuse your car by shifting without using the clutch, but unless you have a race type tranny with dog teeth, you're likely to start breaking things very quickly, and you're not even guaranteed that you will be able to get it into the next gear without an appreciable delay.

Since a human being cannot shift as fast as a manual transmission (although many people are incorrectly convinced they can), than all things being equal, a turbocharged car with an auto tranny should always accellerate more rapidly than one with a standard.


Of course, in the real world, things are never really equal.

HOWEVER...

An automatic transmission won't add 2.5 seconds to your quarter mile time.
It won't even add 2.5 tenths.
Auto transmissions, even power hogs like a THM400, simply don't eat that much horsepower.

And as far as a standard tranny being able to get into the so called "fat spot", automatic transmission ALWAYS make for better, more controlled launch.

With an auto, you rev the engine against the brakes until you reach the stall point, then you "flash" it to a higher RPM by slamming down the gas pedal an instant before you release the brake pedal.

That means that the entire powetrain and chassis is already pre-loaded, which is what gives you a better, more controlled launch.

#21 wrxsubaru

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Posted 20 September 2003 - 11:59 AM

auto matics till have a bov, and even if they kept presure while shifting the extra power lost throught the auto, would slow the car more than the (mini lag).

#22 Hodaka Rider

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Posted 20 September 2003 - 02:50 PM

Turbochargers work by the expansion of exhaust gases coming out of the cylinder (in other words, exhaust flow). Backpressure cuts down on power in a turbocharged engine. If it were true that turbos ran on backpressure, then maybe stick a big cork in the end of a turbo car's exhaust and see how much power it makes.

#23 LameRandomName

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Posted 20 September 2003 - 03:41 PM

Originally posted by wrxsubaru
auto matics till have a bov, and even if they kept presure while shifting the extra power lost throught the auto, would slow the car more than the (mini lag).




Let me try to rephrase this so that you can better understand what I'm saying:

Assuming you had two turbocharged cars, one with a stick and one with an auto, and all the gears in the transmission AND the rear end were the same, then the car with an automatic would acellerate faster than the car with the stick., because the car with the automatic would conserve manifold pressure while the car with the stick would not AND the extra torque multiplication of the automatic would make up for the pumping losses.

#24 LameRandomName

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Posted 20 September 2003 - 03:50 PM

Originally posted by Hodaka Rider
Turbochargers work by the expansion of exhaust gases coming out of the cylinder (in other words, exhaust flow). Backpressure cuts down on power in a turbocharged engine. If it were true that turbos ran on backpressure, then maybe stick a big cork in the end of a turbo car's exhaust and see how much power it makes.




You're confusing manifold back-pressure with exhaust back-pressure.

When the exhaust leaves the head and enters the manifold, it travels to the face of the exhaust side impeller.
If the pressure inside that area isn't high enough it will just flow through the face of the impeller without imparting any meaningful energy to it.
Once the back-pressure in the exhaust manifold has built up high enough, it will overcome the inertia of the impeller and make it start to spin.

On the other side of the turbo, the other impeller is trying to compress the air in the intake manifold.

Now, while you can play with impeller sizes, there is still no such thing as a free lunch, and the higher you want the intake manifold pressure to be, the higher the back pressure in the exhaust manifold has to be.

If we did as you suggested and stuck a cork in the tailpipe, the engine wouldn't run because while the turbo is driven by pressure, not flow, the gasses still have to go somewhere after they pass through the exhaust impeller.

#25 Hodaka Rider

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Posted 20 September 2003 - 04:16 PM

OK. you're getting closer. The exhaust flow is what causes the impeller to spin. The manifold "back-pressure" you are referring to is the resistence to initial flow caused by the obstuction in the mainfold that the impeller creates by it's presence there as well as the need to overcome the static inertia on the compressor end of the shaft. This is overcome with higher exhaust flow. Back-pressure is resistance to flow. What you are referring to is different.
This breaks it down pretty simple: ."How turbos work
to quote: "Having a turbine in the exhaust flow increases the restriction in the exhaust. This means that on the exhaust stroke, the engine has to push against a higher back-pressure. This subtracts a little bit of power from the cylinders that are firing at the same time"




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