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Old 06-21-2001, 01:24 PM   #1
MINDGAME
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Question NA vs. Turbo

I really dig my new 2.5, but obviously want to make some adjustments. I got the 2.5 over the WRX because I really liked its low-end torque, and knew that putting a turbo on it at a later date was always an option. So my first inclination was to go turbo, as that offers the most potential for my car. But since this is a daily driver, and its not uncommon for me to drive 200, maybe even 500 miles in a week, I started to consider going all-motor. I saw the combined gains maxing out at an estimated 210hp (intake, full exhaust, cam, ecu). When I was looking at going deeper into the motor by replacing the pistons and doing headwork, a friend warned me that if I was going NA to improve reliability, then I was going in the wrong direction. He told me that internals like this need constant attention, and that such a car would be less reliable than a turbo.

I may take my car to the track once in awhile, but am more interested in driving through curved country roads at 100+. I'd like to see my car in the 230-250hp range, but want to go the route most reliable. Could somebody please give me some personal advice? Or show me some studies/articles to read? Thanks.

(I have also posted this message in the Turbo forum)
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Old 06-21-2001, 01:33 PM   #2
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Get in touch with someone at Cobb Tuning... they have fabulous parts for the N/A Impreza. Cams, heads, exhaust ... etc. great stuff and they've gotten rave reviews by probably everyone that uses their parts.
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Old 06-21-2001, 02:04 PM   #3
Jon Bogert
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So my first inclination was to go turbo, as that offers the most potential for my car. But since this is a daily driver, and its not uncommon for me to drive 200, maybe even 500 miles in a week, I started to consider going all-motor.
I'm not sure you're drawing the right conclusion here. A mild turbo kit is the ultimate in drivability. Off-boost, it behaves exactly as stock. You can torque around using the 2.5s low-end all day never seeing boost if you don't want to. But the minute you tip-in to the throttle, you get instant horsepower. It's completely unlike the low compression 2.0 turbos I've driven.

I'm not saying that a good combination of better NA breathing and sophisticated engine control can't get you to a very fun place. But in terms of bang for the buck and easy drivability, you can't beat a low boost turbo.
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Old 06-21-2001, 02:46 PM   #4
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But in terms of bang for the buck and easy drivability, you can't beat a low boost turbo.
yes yes but a low boost turbo never stays that way does it? somehow that low boost you started off with gets higher, and higher, and higher...
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Old 06-21-2001, 05:38 PM   #5
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so, apart from cost and drivability and under normal driving situations (no regular trips to the drags), which is more reliable in the long run? a low boost turbo or staying NA?
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Old 06-21-2001, 06:46 PM   #6
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vicster, that's a question without an answer. I believe my setup will be reliable, but a bad tank of gas could destroy my motor in a few seconds. Of course, a bad tank of gas wouldn't be too good for a high compression NA motor running a lot of advance, either. Also consider the long-term effects of revving a built NA motor to 8000 RPM all the time.

A friend of mine built a 220HP NA VW Golf for rallying. In the last six months he's thrown a rod, broken valve springs, and had all sorts of other problems, in spite of the fact that he built on a well known platform using proven component.

When I decided to go turbo, I took a look at my bank account, and figured that I could afford to write a check for a new turbo, an engine rebuild or a tranny rebuild. That is always a good question to ask yourself before you bolt on anything more exciting than an air filter or muffler.
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Old 06-22-2001, 12:12 AM   #7
Pete Holt
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Going N/A will be more reliable because your engine was not designed for a turbo. If you get a really weak turbo, then yes, you will probably be safe, but you will still wear the internals of your engine a lot quicker. The other thing to think about is the cost of gas. If you go N/A with new heads and cams you can still run 87 octane. If you go with a turbo you will definitely need 93 octane and if you go with a big turbo you might even need some octane booster. I would think this would be an issue since you drive 500 miles a week.
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Old 06-22-2001, 09:47 AM   #8
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Good point--I do run 93-94 octane all the time.

But, if you were going to the expense of new heads and cams, would you leave horsepower on the table by not raising the compression a bit? I would also bet that mild cams and head porting combined with stock compression and stock redline won't get you past 200HP, much less 220.
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Old 06-22-2001, 12:00 PM   #9
Rich L
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Going N/A will be more reliable because your engine was not designed for a turbo. If you get a really weak turbo, then yes, you will probably be safe, but you will still wear the internals of your engine a lot quicker
Not true. Some experts (Corkey Bell) claim a well tuned turbo kit will only reduce engine lifespan 10%. Of course this is subjective as to if that qualifies as "alot quicker" but you must make an equal comparison.

A NA tuned engine with the same hp output as a turbo (which means a rise in compression and change in timing) would also reduce lifespan of an engine. (and it might need octane boost as well)

The turbo advantage is that its cheaper and not always in boost.
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Old 06-22-2001, 01:10 PM   #10
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If you wanted a turbo with reliability you shoulda got a WRX instead silly
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Old 06-23-2001, 03:06 AM   #11
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WRX! HAHAHAHAHA, you shall immediately go to the Southern California forum and read "More LACR MADNESS":

then you shall come back and try and find some NEW excuse that explains a brand spanking new WRX's (to be completely fair it was an auto wagon) loss to my intake airfilter and exhaust 00RS. Heres my suggestion


Go N/A for now, build up small, pulley, inatake, exhaust (NOTHING EXPENSIVE! NO BPM NO RALLISPEC), then if after a host of small bolt on mods it still feels like its getting you nowhere...turbo. Going full on NA is harder, more expensive, and for the most part not as fast as the turbo equivelent. me im all for the turbo.

As for the WRX, who was saying the turbo makes up for the butt ugly headlights? WELL NOT ANYMORE hahahaha wait until i post the video!!! oh man its not close either its by about a full second!!!!! Automatics dont sapp THAT much power all you newstyle ugly headlamp "At least i have a turbo, look at my WRX, youre just jelous!!!" Rexies. HAHAHAHA SCORE ONE FOR THE OLDSTYLE! RS RS RS RS RS RS RS RS RS!!! (NO im never going to drop this, yes there is some really good reason why it happened but so what blah blah blah. fact is I SMOKED A WRX IN MY RS and that my friends is IRONIC.)
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Old 06-23-2001, 10:50 PM   #12
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I dunno about buying up NA parts and then switching to turbo. For example, the type of exhaust that's best suited for a turbo is 2.5"ID while for NA it's 2.25"ID isn't it? So in the switch you'd have to dump the latter for the former, in turn losing some cash in the process. I think it'd be best to plan what you want to do according to how much you want to spend. Personally, I'd just go for the simple NA mods like intake/exhaust/pulleys/etc because I can't afford to spend thousands and thousands on pricey mods.

But hey, it all comes down to speed costs $$$, how fast do you really wanna go?

P.S. I'm not surprised that an Auto WRX Wagon lost to the MY00 RS since the auto drains some power, isn't geared as optimally as a manual, plus the extra 400 some odd pounds it's got to lug around!

Keep it slideways!
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Old 06-23-2001, 11:20 PM   #13
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Pete Holt - when modding for N/A performance, you'll also need to up the octane. With cams etc, it's recommend to use 91+ octane fuel to realize the maximum ignition timing etc. Otherwise, you're just paying for a mod and only getting 80% performance out of it.

By far, turbo will be cheaper in the long run. By going turbo or higher C/R, you are essentially increasing the thermal efficiency of the engine.

Doing something like a IHI basic turbo kit from JCS would be best of drivability and power. You'll also realize gains in fuel efficiency, when going with turbo, b/c more power is available on hand, you don't need to rev the ***** of of the engine to get the power.
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