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Discussion Starter #1
I know the general public really dislikes the 7cm on 2.5 liters.

But would a tdo5 18g with a 7cm still be better a vf-series turbo? I mean holding both turbos in my hand the 7cm housing (well actually it was a vf39 but they should be very similar in size. The 7cm housing is larger than a vf-series exhaust housing.


Comments? Opinions?
 

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2004 Subaru FXT MT
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I've seen conflicting numbers on the A/R's on the VF's. Some say .6, some say .9. :shrug:

Now that is out of the way, my opinion and what I believe the general concensus is that for the price used, its hard to beat a VF. Just looking at the compressor map though, a VF series turbo of any sort, except a 22, is still too small for a 2.5L.

An 18g compressor is a bit better. A GT3071 compressor and a S200 compressor is just right:)

As for exhaust, a 7cm is better than a 6cm on a 2.5L. So if you have a lead on a 18g 7cm, go for it. But for the ~$100 more you will have to pay to get a 8cm, you will have less backpressure resulting in more power.
 

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the 22 is too small also, but @ least has the p20 exhaust housing. the 18g regardless of hotside will crap on any vf turbo in everyway as long as you run some boost, if you are going to be conservative dont waste your money. the added cost just isnt worth it, ie: injectors, extra cost of 18g turbo, larger than sti tmic, etc...

what are your power goals for the car?
 

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Discussion Starter #4
hahah dont really know.. originally I wanted like 340-350whp. But I don't think that's a safe goal given our tranny/motors.

soo probably like 300-320whp.
 

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id say think about that some more b4 you make a descision. also are you only going to be using pump gas or meth or e85?

depending on dyno 3-320whp might be obtainable w/ a vf, but you will be pushing the limits to get those numbers.

the hta68 is a good choice to consider as well.
 

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hahah dont really know.. originally I wanted like 340-350whp. But I don't think that's a safe goal given our tranny/motors.

soo probably like 300-320whp.
You need to nail down your goals before you pick a turbo It will dictate what turbo and what hotside you get.

If you're goal is 300whp, pickup a good used VF and support it.

If you want a new turbo and 300whp, pick up a 16g with 7cm or 8cm.

If you want more than that, an 18g8cm is a good option. But that won't get you to 340-350whp. You are going to have to go 20g or bigger to get in that territory...
 

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I'm a pretty big advocate of the VF39/43/xxx as an intial stepping stone. You can put one on with minimal other supporting mod's and it puts the car in a good fast state.

If you want to push further than a VF39 allows, you'll looking at doing injectors, inlet, MAF, possibly more exhaust to really push the system as a whole.
 
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