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Old 02-06-2018, 11:56 AM   #1
LeedomtoFreedom
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Default Which turbo is best turbo?

So I've got a couple options here. My 15g started leaking oil so I swapped back to the little 13c.

Should I

a. Professionally rebuild the 15g

Or

b. Take this opportunity to put something bigger in.

I have most of the supporting mods to put a bigger turbo in.
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Old 02-06-2018, 11:58 AM   #2
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Goals, budget, etc.

If the 15G will support what you want to do, then do that. If you want mOAr hp's, then you might want to start looking for something bigger.

Each additional HP costs more than the last.
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Old 02-06-2018, 12:14 PM   #3
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How far can you take a 15g?

It'd probably be cheaper and maybe satisfy my needs to use it. But I want a big fat turbo because I'll sooner or later be wanting to
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Old 02-06-2018, 12:24 PM   #4
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As said what are your goals. While you can push a 15g to around 240whp past that it really is at the limit, nevermind to do that you need all of the supporting mods to help a 15g get there.

Once you figure out your goals and budget you can decide on what path you want to take.
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Old 02-06-2018, 12:27 PM   #5
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Big fat turbo without all the supporting mods will not be fun to drive.

And dare I saw it, even with all the supporting mods, a small motor/big turbo isn't really always the most responsive engine to use in daily driving.
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Old 02-06-2018, 12:28 PM   #6
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Something smaller than 13c
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Old 02-06-2018, 12:31 PM   #7
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Interesting. Food for thought.

I don't really see myself going far past 300hp. I don't think my car will do it. Ole Bessie is worn out.

The turbo upgrade was usually the last thing I did, focusing more on peripherals to make sure it was done correctly.
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Old 02-06-2018, 12:37 PM   #8
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Go with 16t slightly better turbo for about the same price
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Old 02-06-2018, 12:39 PM   #9
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RE: "Profesionally" Rebuild 15G - You can "home gamer" this unless you didn't feel like marking the CHRA before disassembly.
https://www.volvoforums.org.uk/showp...50&postcount=1

By all means get it balanced professionally if it helps you sleep better at night.

There's my 0.02.
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Old 02-06-2018, 01:21 PM   #10
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Quote:
Originally Posted by JohnMc View Post
Big fat turbo without all the supporting mods will not be fun to drive.

And dare I saw it, even with all the supporting mods, a small motor/big turbo isn't really always the most responsive engine to use in daily driving.

Here's a big turbo is too big thread.
https://forums.tbforums.com/showthread.php?t=337827
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Old 02-06-2018, 01:22 PM   #11
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Quote:
Originally Posted by Jack View Post
Go with 16t slightly better turbo for about the same price
There is almost zero gain from 15G to 16T. I wouldn't waste money on it.
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Old 02-06-2018, 01:35 PM   #12
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Quote:
Originally Posted by tryingbe View Post
Here's a big turbo is too big thread.
https://forums.tbforums.com/showthread.php?t=337827
It ends up being a light switch. Off boost - no power, On boost *all the powers*!!! Not much in between.

The motor in my wagon really only felt fairly normal once I got variable boost control setup (Megasquirt) - 8 psi base, up to 22 -24, but based on throttle position. That actually feels somewhat normal and progressive. There's still some lag with 400 hp worth of turbo on a 2.3L engine.
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Old 02-06-2018, 01:38 PM   #13
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Best turbo? We might as well decide the best ice cream flavor.......

OP, think "time to torque"..... as the goal.
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Old 02-06-2018, 01:57 PM   #14
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Big turbo is boring...until it isn't mine doesn't even spool fast and I have a header/open exhaust/big cam/advanced timing....spool ain't much to write home about
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Old 02-06-2018, 02:05 PM   #15
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Spool fights between the turbo and the cruise control can be entertaining. I mostly got that with the 16T and the M47.
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Old 02-06-2018, 03:06 PM   #16
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I just look back to that crazy 8 page thread going about spool time in the T3/T4 and I'm trying to think if that's user error to see if I want to try something similar.

When I had the 15g in, it spooled mucho quick. Should I sacrifice spool time for some HP gains ? If I chose the turbo well, getting one not much larger than the 15g, could the spool time be acceptable for the overall flow. What have people typically done before.
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Old 02-06-2018, 03:11 PM   #17
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15G spools fast because it has a tiny hotside. So you get boost sooner, earlier, more often, less lag. Which is better for a general daily driver. The main issue with a tiny hotside is that it limits peak flow. At high rpm WOT, the engine can only force so much air out past the hotside, even with the wastegate open. So less peak HP (usually found at high RPM's) but more usable, easily accessible power down lower in the rev range.

A big turbo won't choke the air flow on the top end, but then the engine can't spool it very easily You get more lag, you have to wait longer as the revs climb, and even then, off throttle to on throttle there's more time. You do get a higher peak HP, but it's not all win-win, you lose low rpm power and throttle response.

Some big turbos can do things to help spool earlier. Divided scroll helps, ball bearings help, exotic lightweight materials in the spinny parts of the turbo can help. As well as having a cam suited for the RPM ranges the turbo will work best at. A high revving cam isn't a great match for a small insta-spool turbo, nor is a T (for Tractor) cam a great match for a big turbo aiming for high RPM dyno queen peak HP glory.
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Old 02-06-2018, 03:13 PM   #18
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Mine doesn't reach full boost till 3200+ slow off the line but hang on when it hits
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Old 02-06-2018, 03:16 PM   #19
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So this is what I'm understanding

a. either keep the 15g and be happy with quick spools

b. get a larger turbo and suffer from turbo lag

c. get a larger turbo but spend more time on making it spool quicker? eg. exhaust, intake, bearings, blah, blah
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Old 02-06-2018, 03:30 PM   #20
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Not boost lag.

Boost threshold.

https://www.youtube.com/watch?v=cKvOEZ7JCJc
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Old 02-06-2018, 03:37 PM   #21
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Quote:
Originally Posted by LeedomtoFreedom View Post
So this is what I'm understanding

a. either keep the 15g and be happy with quick spools

b. get a larger turbo and suffer from turbo lag

c. get a larger turbo but spend more time on making it spool quicker? eg. exhaust, intake, bearings, blah, blah
A big one won't spool as fast as a smaller one trust me. I have supporting stuff and it its still not as fast as a smaller mitsu. It''s not a daily so I don't care but if it was....it wouldn't be very fun.
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Old 02-06-2018, 03:42 PM   #22
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Both really. Higher RPM to get spooled, and even above that RPM, more time between off throttle and on-throttle with full boost. But the threshold is the one people tend to notice far more.

It just means that a bigger turbo is not always better. It depends on your goals, and your goals as expressed through how you plan on using the car.

A small motor with a big turbo with big peak HP is *usually* going to be less fun to deal with in daily driving. It's like driving a 90 hp turd of a slow car most of the time, interspersed with occasional brief moments of HOLYCRAPHANGON. There's not a whole lot of in between. The motor is either off boost and not making much HP, or it's spooled up and making 'too much'.

After living with miine for a long while I'm going V8 turbo. More instant normally aspirated HP off boost, less added turbo power on top.
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Old 02-06-2018, 05:03 PM   #23
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Look at t3 flanged gt28s or tial vbanded gt28s. Gotta pay to play, but holyfuk do they just feel good. A buddy ran mitsus for years on his Saab, most recent was a td04hl-16t (Volvo) with an angled flange off a diy t3 log manifold. Spool was great, but in 4th at 1800-2000, you’d stomp on the throttle and get a good 3 count before 18psi was reached. Swapped to a gt2871rs, with a t3>3” vband hot side and now it just feels like it’s loaded with crazy na power. I can get a 1 out before 18psi, sometimes a 2 count.
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Old 02-06-2018, 05:23 PM   #24
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Rebuild the 15g yourself. It will cost not even 50 bucks

Mark the position of the compressor wheel relative to the turbine wheel before disassembly.
Assemble it in the same position.

(not sure if this is totally necessary, as I believe TD04's are component balanced, but it is a good precaution).

I have done this multiple times with great results. Fvck "professional rebuilds".
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Old 02-07-2018, 12:26 AM   #25
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Quote:
What is a boy to do
I'll check the prices for a 15g rebuild kit for now and if I chose to later, maybe get a bigger blower. That sounds like the best option

I've heard of people rebuilding kits on their own but not entirely sure if it was safe to do.
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