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PostPosted: Tue Sep 23, 2008 10:47 pm 
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Thanks Pf, what turbo did you use?

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PostPosted: Tue Sep 23, 2008 10:56 pm 
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Location: SE MI
06 Subaru WRX stock turbocharger - TD04L-13T is the model number. It is a high response, low lag unit that IMO is one of the best you can get for a Miata engine - even better than the commonly used T25 and Greddy turbochargers. You might even get away with not using an intercooler at low boost, though a turbo without intercooler is somewhat akin to unprotected sex.


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PostPosted: Wed Sep 24, 2008 3:22 pm 
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Oh man,

I started to respond to some of the posts on the thread but realized there is just to many wrong comments.

*disclaimer*

Those reading this thread please do more research on the responses found here :-)

Some funny things I cought:
1. People saying use a t3/t4 turbo. Ummm.. You just quoted the frame size not the turbo itself. Common error. That would be like me saying run a book/+442 motor in your locost and you will have a good motor. You would then say "you just quoted me frame sizes not motors".
2. Water/Meth/alchy. Its good stuff. Please read more on it if interested then what is found in this thread.
3. I ran 13 psi on a 10:1 motor for over 20k and never had a problem. The owner after me is still doing this and I have no idea how many miles the car has now. Its all in the tuning.

Gotta jet. :D

J. R.

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PostPosted: Wed Sep 24, 2008 5:07 pm 
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I dont know if any one menentioned it as I just scanned the thread. That turbo is total junk you posted in the first post. Anything XS, SSAUTOCHROME, Turbo XS Power, etc is not a real turbo. They are paperweights.

With that being said it is possible to get a decent turbo off of ebay for cheap if your looking for rebuilt Garrett units. You just have to know what your looking for and what car the turbo came off stock. I happened to have a monster t3/t4 that was good for like 600hp that I bought for $450 on ebay. It was just that a monster. Worked well on my 2.3l FE DOHC but not well on a smaller engine.

For a miata you could get by with a small mitsu turbo like a 16g or something like that. As for inter cooler, use one off a stock 88-92 MX6 GT its a nice size for cheap. The manifold you post will work but it may crack in the future so you may have to weld it a few time.

As for injectors Percision has really good injectors for cheap although you could try something like a 5th injector setup if you strapped for cash.

Check out http://www.homemadeturbo.com

evo


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PostPosted: Wed Sep 24, 2008 9:28 pm 
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Miatav8,MstrASE,A&P,F wrote:
I guess Chet's question didn't get answered.

If I were going homebrewed, I would use the turbo, turbine housing, exhaust head pipe flange, bov, and waste gate components from a Mitsubishi Eclipse.


You stole my idea :P Look on page 2.


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PostPosted: Wed Sep 24, 2008 10:37 pm 
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Chet, it's little late in the thread but, what kind of budget are you working with?

Moti

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PostPosted: Wed Sep 24, 2008 11:49 pm 
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Blackbird wrote:
Chet, it's little late in the thread but, what kind of budget are you working with?

Moti


I was hoping to get it done for around $1500.

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PostPosted: Thu Sep 25, 2008 1:32 am 
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evo626 wrote:
The manifold you post will work but it may crack in the future so you may have to weld it a few time.


I have heard that these chinese ebay manifolds are prone to cracking, but have never seen a case. I have heard that you can weld some sort of support structure to it to support the turbo and exhaust/intake tubing so that there is not any weight on it, this would be the best idea.

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PostPosted: Thu Sep 25, 2008 7:11 am 
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A good inexpensive turbo that would probably work well for a miata engine would be saab turbo, I think its a t28 or t3 size which would be perfect for the smaller 4 cylinders, and they can usually be had in good condition for about $400. If cash is not too much of a concern I would recommend the "Disco Potato" which is made by garret and is very well reviewed in the tuner world from what I've seen.

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PostPosted: Thu Sep 25, 2008 7:25 am 
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4G63-7 wrote:
Miatav8,MstrASE,A&P,F wrote:
I guess Chet's question didn't get answered.

If I were going homebrewed, I would use the turbo, turbine housing, exhaust head pipe flange, bov, and waste gate components from a Mitsubishi Eclipse.


You stole my idea :P Look on page 2.


I broke the rule of not reading all the previous posts. I actually told myself I wasn't going to comment, since I wasn't into turbocharging anymore. I guess I can't help myself.


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PostPosted: Thu Sep 25, 2008 8:27 am 
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BrianG701 wrote:
A good inexpensive turbo that would probably work well for a miata engine would be saab turbo, I think its a t28 or t3 size which would be perfect for the smaller 4 cylinders, and they can usually be had in good condition for about $400. If cash is not too much of a concern I would recommend the "Disco Potato" which is made by garret and is very well reviewed in the tuner world from what I've seen.


Thanks, but in this thread K. Tanner says it doesn't work well on a Miata engine. After some Ebaying, it looks like the stock WRX turbo may be the way to go.

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PostPosted: Thu Sep 25, 2008 10:16 am 
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Strictly "as cheap as you can get" speaking:
Last I looked the KKK K03 turbo's were pretty cheap. You'd have to create your own manifold for it tho. Kinda small even for the miata 1.8L. But if you were going to stay low boost (I think not much more than 5-6psi). These are the stock turbos on some Audi/VW's (A4 and Passat) and usually cast aside by the power hungry for larger units. I havent looked in a while.


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 Post subject: Supercharge!
PostPosted: Thu Sep 25, 2008 10:20 am 
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Ok, this may be off topic and not the direction you want to go but I'll give it a shot. I have a Fastforward supercharger in my 2002 Miata. I love it. I will be supercharging my Locost with the same. (Project scheduled to start next year.) The kit is complete and is truely plug and play. There are several options for their kits, hotside, coldside yours would have to be a hotside I think because of the space limits on your intake side. Fuel management is with PC Pros. Prewired to plug right into your ECU. No intercooler needed because these use a fifth injector to cool the charge air and add fuel. Most importantly is the customer support is beyond any company out there. 24/7 guranteed. www.fastforwardsuperchargers.com

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PostPosted: Thu Sep 25, 2008 10:36 am 
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I'd choose a turbo that has a flange that other miata friendly turbos exist in.
Try to keep an upgrade path in mind, because I'll bet my shorts that the first turbo you're going to put on it won't be the last :wink: ...

Moti

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PostPosted: Thu Sep 25, 2008 3:08 pm 
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KKK K03 is a bad-bad choice for the miata, even if it is the cheapest (but not by much). It is undersized and the scroll/impeller geometry is inferior to the Subaru turbos. For the non-believers, my setup, posted earlier in this thread, was designed in consultation with a powertrain engineer who works for Holset. Here's a basic analysis we did to match the turbo to the engine (quoted from my post in Miataturbo forums):

Quote:
First, I plotted this airflow vs. RPM curve for the Miata 1.6 engine at a pressure ratio of 1.8 (desired hp/original hp or 175 whp/95 whp). I had to make many assumptions to get this curve, but I think its fairly accurate for an autocross/street situation:

Image

So in the 2500 to 5800 rpm range, the compressor needs to flow between 5 and 20 lbs/min of air. The compressor is assumed to spool up to 12 psi (i.e. 1.8 pressure ratio) by 3100 rpm at which point its flowing 8 lbs/min.

Then I made this chart and overlaid it on a few compressor maps.

Image

That yields a compressor efficiency vs. RPM chart as below:

Image

An efficiency of 0% means that surge or choke limits have been reached for that combo of airflow and pressure ratio.

K03-2072 (black line) is the turbo commonly referred to as K03-Sport in the VW/Audi community. You guys know all the others.

From this analysis, it looks like the 13G (red line) is the best, but the K03 and 15G (green line) come close. You can see why Greddy chose the 15G for their kit. The GT2554R (blue line) seems to be the poorest choice of all.


Quote:

I did some research today and also came up with a third choice over the 15G and 13G: the TD04-13T found in the 02-06 WRX. This is a comparison of the three turbos:

Image

I think the 13T is evenly matched in the mid-range, but its efficient even past 7000 rpm @ 12psi. Even on the turbine side it has to be flowing much better than the 13G and 15G cause it supports like 230 hp stock.



Why compressor efficiency? Because more efficiency means a lower charge air temperature, which in turn means a smaller core of intercooler can be used. A smaller core in general also means less packaging headaches (specially in a locost) and lower pressure loss across the core (when designed properly). A lower charge air temperature also means the air is much denser and you can stuff more air into the engine, in simple terms. Another added advantage is you can run much more timing with dense, cool air, and in turn that means you achieve the max. amount of power for a given size of turbo.

Granted this is not the cheapest that you can turbo a miata for, but the extra cash is well spent. Plus it is a highly original setup that only a few people have attempted.

Someone mentioned the "upgrade path", even that was kept in mind while designing my system. You can start with the stock TD04L-13T that comes in the 02+ WRX, then port the same turbo in the wastegate area for improved peak power. Once you get bored, all you need to do is throw it away, and simply bolt-on a VF39 from a stock 04+ STi. This will flow enough for 400+ wheel hp on a miata engine. I am sure people here will agree that this is enough power for a 1200 lb locost.


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