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Old 06-02-2004, 07:51 PM   #1
kenlee
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Default what has more top end, pe1820,or 1825?

I'm considering going the twin scroll route for good low end pull, but does anyone know if the 1820 (vf22), or the 1825 (vf37) has more top end? I'd assume the 1820 would but I thought I'd try to get a better answer. I have the pe parts book and it rates the 1820 @ 335whp on a 2.0 and the 1825 @ 365 on a 2.0

I've considered the green, but it sounds like it's lacking in the low end and I'd have to run it at 22+psi for the sweet spot and I don't think I want to put my daily driver through that.
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Old 06-07-2004, 01:11 AM   #2
ImprezaRSfan!
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1825 would have more top end since its twinscroll and i think its rated for more power too
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Old 06-07-2004, 01:41 AM   #3
kenlee
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What are most people seeing full boost at, (say 22-25psi) on the 2.5 usdm? I raced a 04 cobra and had him through 1st, 2nd, by third we were even, but he was pulling hard, and forth it was over he was pulling cars. My sti is stock as is the cobra I raced. I'd like to keep about the same spool, but will sacrifice some to replace it with more top end.
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Old 06-07-2004, 11:19 AM   #4
staticx313
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with a twin scroll setup you will not be sacrificing spool up... spool up on twin scrolls is rediculously fast. Even the fp greens were hitting like 2X psi at 3k rpms... being a twin scroll im sure you'll have nearly full boost around 3 or so. Mauromotorsports can surely help you out since they have a twin scroll setup.

Robert~
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Old 06-07-2004, 11:57 AM   #5
dug-e-fresh
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I hit 15 psi @ ~2500 rpms. 20-22 psi by ~3000 rpms. (4th or 5th gear pulls).

I fixed my manifold leak and now can actually build so much boost downlow that I get a knock flash... my tune previously was based around slower spool because of my exhaust leak.

Even with a pretty bad leak, I spooled up on par with a VF30, if not a little better.

Boost begins building @ around 1000 rpms... very little (ie- 1-2 psi), but it starts.

I am running the twinscroll VF36 off the Version 8 Spec C.

def
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Old 06-07-2004, 12:47 PM   #6
happasaiyan
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hey dug-e you running the 257?
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Old 06-07-2004, 12:59 PM   #7
dug-e-fresh
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Nope, EJ207, sorry for the confusion, if any. Just felt I had value to add even if this is the 2.5 forum

def
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Old 06-07-2004, 01:14 PM   #8
happasaiyan
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definately adds value...just was wondering why your spoolup times were so low (twin scrolls with the 257 have over a bar of boost before 2k )

still a sick setup you have there dug-e
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Old 06-07-2004, 02:17 PM   #9
MauroMotorsports
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After tuning a VF37 on a 2.5 should have at least 14psi of boost at around 2000-2500rpm. I am actually getting 16psi at 2500rpm right now with just an HKS EVC EZ II on my STi. However, boost will NOT hold more then 14psi to redline. Which means the internal wastegate actuator is doing its job. By installing a PE1825 or having a VF 36 or 37 rebuilt to be identical to a PE1825 (much cheaper route), you will be able to build boost slightly quicker then the PE1820, make more top-end then the 1820, and hold boost about the same as an 1820.

In my opinion one of the larger purposes of the twin scroll setup is not just spool-up. It's exhaust flow, which leads to greater throttle response......wait I take that back....rediculous throttle response

Anthony
www.mauromotorsports.com
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Old 06-07-2004, 03:14 PM   #10
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Twinscrolling does one thing that happens to affect a few other things.

It isolates opposing exhaust pulses from one another.

By doing this, it eliminates "fighting among the pulses".

(think about the "fighting" in terms of a rowing team, when in sync and everyone digging in at once, efficiency is improved... if the rowing is out of sync, it throws things outta whack).

This reduces lag and improves VE 2 fold:

1- less "fighting" going on and

2- greatly reduces inversion, which is the phenomenon where exhaust gas is sucked back into the cylinder as its taking in charge air... occurs when both the exhaust and intake valves are open.

def
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Old 06-07-2004, 03:48 PM   #11
kenlee
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Thanks for the info guys.
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Old 06-08-2004, 01:10 PM   #12
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shoulda got the motor with zerospots twinscroll turbo... same price

I bought hyper rev edition #84 on ebay. Its 100% about the impreza GD.

It shows twinscroll turbos from FLATT RACING DIV., PWR PE1825F, and ZEROSPORTS with the turbo name in japanese.

dug-e-fresh do u think i should order a zerosports twinscroll 3" downpipe from japan for like a G prolly, or do what u did and modify a regular downpipe?
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Old 06-08-2004, 01:50 PM   #13
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Quote:
Originally posted by ImprezaRSfan!
shoulda got the motor with zerospots twinscroll turbo... same price

I bought hyper rev edition #84 on ebay. Its 100% about the impreza GD.

It shows twinscroll turbos from FLATT RACING DIV., PWR PE1825F, and ZEROSPORTS with the turbo name in japanese.

dug-e-fresh do u think i should order a zerosports twinscroll 3" downpipe from japan for like a G prolly, or do what u did and modify a regular downpipe?
Definitely mod a regular pipe... theres no sense in spending that much on something so basic, ya know?

Take whatever money leftover after modding a stocker dp, and get the VF37/36 modded to be an 1825

... or sell the STi intercooler and use that funds together to get a topmount or even a frontmount...

.... or ditch the factory boost controller for an SBC iD... I love that thing!

I'd like to check out that magazine... eBay, here I come!

def
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Old 06-08-2004, 09:14 PM   #14
euglow
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Default Modding VF36/37 to 1825

How do you mod a VF36/37 to a 1825 ?

From what I understand you can change the compressor side wheel to 18G but how you intend to get the exhaust side to 25?
Porting?
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Old 06-09-2004, 12:10 AM   #15
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the more i hear of twin-scroll turbos - not to mention the critically exclaimed, impreza type25 (litchfield) - the more i feel this is the route i will go when modifying my car... i have done some research on twin-scrolls and my main feeling is that not only is there an extremely noticeable increase in low end power/spool-up, but also an increase in top end...

am i correct in thinking this?... and if so would the top end power increase as dramatically as low end?
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Old 06-09-2004, 12:34 AM   #16
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Quote:
Originally posted by kenlee

I've considered the green, but it sounds like it's lacking in the low end
you're nuts
A green spools like a stock VF39. plenty of low end!!
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