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Old 07-16-2008, 10:32 AM   #1
fearmywrx
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Default 18g TD05H 7cm^2 or 8cm^2 ?

Just as the title states I am wonder which I should purchace. The 8cm2 is actually like 50 bucks off thats why I posted this thread.

I was going to go with the 7 cm2 cause i thought it would be a little quicker spool. But according to blouch " 8cm2 turbine housing that produces an additional 20 to 30 lb/ft peak torque over the 7 cm2 turbine housing."

I have a 2.0 so what do you guys think? 7 or 8 cm?

Thanks for your guys help.

Kurt
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Old 07-16-2008, 10:52 AM   #2
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been down this road. I decided on the 8cm. You're not going to have a noticeable increase in lag and it is going to net slightly higher gains. If you're a "sissy" about spool, which is fine, then go for the 7cm.

Just remember, even though you're not reaching FULL boost until a few hun' RPM later, you're still IN BOOST and getting pinned to your seat.
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Old 07-16-2008, 11:03 AM   #3
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i think we both particpated in the same thread about this about a month back.
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Old 07-16-2008, 11:12 AM   #4
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Quote:
Originally Posted by fearmywrx View Post
i think we both particpated in the same thread about this about a month back.
yeah, you're right.
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Old 07-16-2008, 11:33 AM   #5
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I think you should talk to your tuner and not us idiots.
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Old 07-16-2008, 11:43 AM   #6
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Quote:
Originally Posted by Unabomber View Post
I think you should talk to your tuner and not us idiots.
that's a good call. Make sure you tell them what you want out of it. If it's more power, 8cm. Quicker spool with a touch less top-end, 7cm.
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Old 07-16-2008, 11:54 AM   #7
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Quote:
Originally Posted by smurfwrx View Post
that's a good call. Make sure you tell them what you want out of it. If it's more power, 8cm. Quicker spool with a touch less top-end, 7cm.
+1

i guess i am a lag sissy.... i just got a 7cm
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Old 07-16-2008, 01:27 PM   #8
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i wonder why the 7cm^2 is more expensive than the 8cm^2. does anyone know why that would be?
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Old 10-14-2008, 03:39 PM   #9
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Can someone tell me how much of a difference in spool we're talking about between a 7cm and 8cm? Also how much of a power & torque difference are we taking about?

My goal is about 320 whp and like 290 torque.... I wanna be able to take or be as fast as cam'd stage2 evo's and stage2 sti's
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Old 10-14-2008, 04:29 PM   #10
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7cm for quicker spool..however if you have 93octane gas than go for 8cm..an 8cm on 93 will perform the same on a 7cm wit 91 from what ive been told and if you port and polish the 8cm turbo than it should be the same as an unpolised 7cm..unless you want super quick spool then 7cm PnP..it would be nice to know what your goals are..auto-x? quarter mile?
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Old 10-14-2008, 04:35 PM   #11
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I have 93 octane gas and I'm looking at the Greddy 18G 8cm specifically. My goal if anything is quarter mile and to be able to keep up with stage2 camd evos, and stage2 STi's....

So how much of a difference in rpm and power & torque is there between the two?
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Old 10-14-2008, 06:16 PM   #12
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anyone?
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Old 10-14-2008, 06:37 PM   #13
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The difference in sool is not worth the extra few hp in MY opinion. But even with the 8cm, if you think you'll keep up with Stage2 cammed Evos, you're dreaming. Stage 2 STi, that would be a good race. I think the best would be the TD05 with EWG, TGV deletes, and methanol. Or at LEAST the meth if you want to keep up with the Evo and be faster than the Stage2 STi. For what it's worth, my EvoIII on pump gas keeps up with Cobb Stage2 STis easily, and some pro-tuned Stage 2 STis, but a buddy of mine with a Stage2 cammed Evo9 walked away from about 50mph on up. In the 1/4 he ran an 11.8 to my 12.6, that's a healthy margin.
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Old 10-14-2008, 07:16 PM   #14
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So in other words if I want to have a chance at the cammed stage2 evo I need to go 8cm 18G with meth? Yet you say the 8cm isn't worht the extra hp?
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Old 10-14-2008, 07:50 PM   #15
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Quote:
Originally Posted by Unabomber View Post
I think you should talk to your tuner and not us idiots.



Do you EVER have any good advice?

He asked US and NOT his tuner because he wanted USER FEEDBACK.

A tuner will tell you all day long what HE thinks is best, but until he hears it from PEOPLE THAT HAVE THE SETUP, he isnt going to come to a conclusion.

ITS CALLED RESEARCH. Hes RESEARCHING thoughts and opinions of MANY people not just ONE tuner.

go write some stupid faq that nobody reads.
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Old 10-14-2008, 09:39 PM   #16
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Quote:
Originally Posted by PinnacleChronos View Post
So in other words if I want to have a chance at the cammed stage2 evo I need to go 8cm 18G with meth? Yet you say the 8cm isn't worht the extra hp?

Correct, that's exactly what I'm saying.
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Old 10-14-2008, 11:46 PM   #17
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To run consistant high 11's (read keep up with cammed Evos) on the stock block internals 205 you really need 2 things. #1 the right setup, I mean every trick you can get your hands on, PnP work, EWG, Meth or C16, A great tune, reducing unsprung mass, Etc. #2 A GOOD driver.

Remember bigger isnt alway better for a turbo when it comes to consistancy in the 1/4mile. I recently saw a thread where a guy put a green on his 2.0L and made like 370Hp... BUT his spool was at 5000 rpm. So thats a 2000rpm powerband. Lets compare that to my measly 310HP 18G that spools at 3700rpm- a 3300rpm powerband. The area under the curve makes the car more driveable.
Both cars netted a 12.5 in the 1/4. Now I know this will peev some people who will say a greend car will own an 18Gd car but all I need to point out is this,....
The stock block stock internals 2.0L record holder is Coolrex who ran an 18G setup. He ran 11.7
Anyone?
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Old 10-15-2008, 12:22 AM   #18
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Quote:
Originally Posted by jmlaser View Post
The stock block stock internals 2.0L record holder is Coolrex who ran an 18G setup. He ran 11.7
Anyone?

And 16gs have gone 11.8 with the right setup and the right driver, just like you mentioned.
But I will say, driver's being equal, you'll need the 18g with every bolt-on available and a perfect tune, under the best circumstances, to be near competitive with that Evo, with meth/race gas or both to run him down. The STi not so much, an 18g on pump with a good tune will hang right with it. Hell, I run 12.6 with simple bolt-ons with an EvoIII on pump, and that's not bad for a Stage2 STi.
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Old 10-15-2008, 12:41 AM   #19
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Cool so back to my original question, I should basically get the 8cm 18G instead of 7cm to run against STi's, and add meth later on if I wanna start running the with the cammed evos'...

Also how much of a rpm & hp difference are we talking about between 7cm vs 8cm (assuming same turbo no portnpolish work).

Just to note, I'm running a smaller type FMIC currently on the TD04 and I notice no increase in lag with my custom tune.
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Old 10-15-2008, 12:50 AM   #20
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Quote:
Originally Posted by PinnacleChronos View Post
Cool so back to my original question, I should basically get the 8cm 18G instead of 7cm to run against STi's, and add meth later on if I wanna start running the with the cammed evos'...

Also how much of a rpm & hp difference are we talking about between 7cm vs 8cm (assuming same turbo no portnpolish work).

Just to note, I'm running a smaller type FMIC currently on the TD04 and I notice no increase in lag with my custom tune.

Stick with the 7cm. It's lopsided with the 8cm, the compressor side isn't big enough to make good use of the larger hotside. The extra power isn't worth the extra wait. With EWG/headers/TGV deletes, among other bolt-ons, you'll easily outpull the STi. You will need that and then some to take the Evo.

A 20G-8cm is barely worth it, the 18G-8cm isn't.

Last edited by Audiosavvy; 10-15-2008 at 01:02 AM.
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Old 10-15-2008, 02:19 AM   #21
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Cool, thanks for all the help.

BTW does anyone know the actual spool rpm & hp/tq difference between 7cm and 8cm?
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Old 10-15-2008, 09:26 AM   #22
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I've been back and forth on this. In july, when this thread was started, I was sure I wanted the 8cm. Then I thought I'd better go with the 7cm.

Either way, I personally am going with "the works" aside from built internals. meth, EWG, PnP everything, TGV deletes, etc., etc. Not short-cutting anything.

I think what will make me finally decide is whether or not I go FMIC. If so, I'll probably stay with the 7cm to account for some delay in throttle response and if I stay TMIC, I may just go for the 8cm, not sure yet.
A great guy to talk to about the subject (seeing as how he's switched turbo's like underwear) is Davenow. he's got some real insight on the subject.
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Old 10-15-2008, 05:20 PM   #23
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When can I expect full boost in the 7cm and 8cm for 93 octane, small FMIC?
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Old 10-15-2008, 05:27 PM   #24
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Quote:
Originally Posted by PinnacleChronos View Post
When can I expect full boost in the 7cm and 8cm for 93 octane, small FMIC?


Depends on the tune and a few other things. 3500ish-4000ish
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Old 10-16-2008, 02:15 AM   #25
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I have been thinking of trying the 8cm housing for a while now. I just cant seem to pull the trigger because it may net me next to nothing in power for the $300 spent. I know an external gate would net some good gains for sure. I have been pondering this because I can get surge fairly easily in the upper gears, and I suffer from a bit of boost creep above 6,000 rpms. It seems that this would be more reliable and less complex/ less expensive than going to an external gate setup. And I did port the turbine housing on my 7cm and it still creeps, not as bad as it did before but it still does some.
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