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PostPosted: September 20, 2008, 12:35 pm 
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OK so I'm planning a turbo buildup for my Locost over the winter. I read lots of good info in the FAQ "turbo" thread.

There's lots of good information there, but not much talk of cost. Since most of us here like to focus on bang for the buck, I thought it would be nice to focus on an inexpensive homebrew setup with cheap Ebay or junkyard parts. Sure anyone can cobble something together that makes boost and melts pistons, but I'd like to reach a consensus (on an internet forum I realize it would be a first) on a cheap, functioning, reliable system.

Since we are doing this on the cheap I think we should first agree on what compromises are worth making.

Would everyone agree that maximum power and performance should not be a goal, but rather something realistic for an inexpensive system.

Fuel management is always a subject of debate, though I think everyone will agree a standalone system that controls fuel, spark, and boost levels is ideal. My question is, "but is it a requirement." It can be had rather cheaply for my Miata mill at $700 for a MS PNP, but can you get by without it.

I remember back ages ago when I drove Neons and read the Neon boards. Lots of people used rising rate fuel pressure regulators and larger injectors etc. to get more fuel. They had problems getting the car to idle, and spent a lot of time doing engine swaps.

How cheap can you go without being reckless to a point it becomes counterproductive and you find yourself spending more money because you are replacing engines on a regular basis?

Here are some cheapo Ebay parts I've had my eye on. If anyone can offer informed opinions on them I would appreciate it. Got any other suggestions for cheap, low-buck setups? Please share them!

Prices below include shipping.
Cheap 1.8 Miata manifold:($135)

Quote:
Full Stainless Turbo Manifold

Brand New Turbo Manifold for Miata 1.8L NA Convert to Turbo Setup
T25/T28 Turbo Flange
This turbo manifold will fit 1.8L (DO NOT FIT 1.6L)
SUS304 STAINLESS STEEL
MANDREL BENT TUBES - NOT CRUSH BENT!
EACH MANIFOLD PORTED AND POLISHED FOR THE MOST POWER

Cheap T25 Turbo: ($230)
Quote:
JDM'S T25/T28 Turbocharger!!
Turbine Turbocharger
Oil cooled and water cooled
Compressor Specs :
1.70" Compressor Inlet
1.685" or 42.81mm inducer
2.362" or 60.00mm Major
Compressor .80 A.R.
M24 T2 Compressor Housing
Turbine Specs :
1.850" Exducer
Turbine .86 A.R.
2.090" or 53.10mm Major
1.820" or 46.25mm Minor
Exhaust Outlet Flange with 5 bolt design
Comes with internal wastegate set around 7psi.
Suggested for 1.6L to 2.0L engine up to 100-275HP

[/quote]


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PostPosted: September 20, 2008, 1:36 pm 
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I liken building up a turbo engine cheaply with wanting to go to the moon for $10,000. There are some things where corners can't be cut.

I mean no disrespect, but for every 100 people who build a turbo engine, it seems that 99 of them end up with a rod through the block. Most people put on turbos way too big for the engine, resulting in nothing happening up to 4000 rpm, then, boom, the horsepower doubles in 1000 rpm, the rear tires spin, and off the road they go, but I digress.

The absolutely non-negotiable requirement is to have the ECU tuned by a professional. Of course that means using an ECU that's tunable, but it makes the difference between a blown up engine and something that'll last. So in my mind, the ECU and tuning should be outside the budget - it's not something that can be cheated on.

That aside, the super-cheap ebay kits very likely use Chinese-made turbos which might last but probably won't.

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PostPosted: September 20, 2008, 2:03 pm 
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KB58 wrote:
I liken building up a turbo engine cheaply with wanting to go to the moon for $10,000. There are some things where corners can't be cut.
If that was true the moon would be a very crowded place because it happens all the time. These setups are in most cases short lived. There are others out there that seem to work well and last. (usually built by someone on his third or fourth try)
Quote:
I mean no disrespect, but for every 100 people who build a turbo engine, it seems that 99 of them end up with a rod through the block. Most people put on turbos way too big for the engine, resulting in nothing happening up to 4000 rpm, then, boom, the horsepower doubles in 1000 rpm, the rear tires spin, and off the road they go, but I digress.
So the fact you mention this tells me you feel I fall within that 99. Thanks for the vote of confidence. :P Regarding the high percentage of failures, couldn't the same be said of people who try to build a car from scratch?
Quote:
The absolutely non-negotiable requirement is to have the ECU tuned by a professional. Of course that means using an ECU that's tunable, but it makes the difference between a blown up engine and something that'll last. So in my mind, the ECU and tuning should be outside the budget - it's not something that can be cheated on.
I think you've spent too much time working with expensive engines. I think I can afford to blow through a few 1.8 shortblocks (cheap and abundant) before I've spent the $$$$ it would cost for a programmable computer and the cost of having it professionally tuned on a steady state dyno.
Quote:
That aside, the super-cheap ebay kits very likely use Chinese-made turbos which might last but probably won't.
I've rebuilt Garrett turbos before (turbo Dodge) and they aren't remarkably complicated pieces of equipment. As long as the rotating assembly is balanced it should work fine. Maybe I'm overly optimistic but I'd bet even the Chinese could get this right. They did a remarkable job on the angle grinder I've used for the past 5 years. (I even got to use the extra motor brushes they included with it) :P

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PostPosted: September 20, 2008, 2:25 pm 
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I'm on forums where a ton of people have done the exact same thing and blown up their engines. Everyone who's learned the hard way says the same thing about tuning, but if rebuilding or replacing engines is a solution, okay. I really was trying to help but it sounds like you've already made up your mind.

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PostPosted: September 20, 2008, 2:31 pm 
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The reality is that tons of people have done this with Miatas. I would suggest asking the same question on miata.net Heck, they have a forced induction forum, and every solution under the sun has probably been investigated/done.


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PostPosted: September 20, 2008, 2:48 pm 
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KB58 wrote:
I'm on forums where a ton of people have done the exact same thing and blown up their engines. Everyone who's learned the hard way says the same thing about tuning, but if rebuilding or replacing engines is a solution, okay. I really was trying to help but it sounds like you've already made up your mind.


I appreciate your input Kurt but maybe I wasn't clear with what advice I was asking for. I've read books, and countless threads all over the internet on the topic so I think I have a firm grasp on how to do it right. Sadly I can't afford to do it right, so I have as you stated made up my mind to do it wrong. It will be a learning experience and maybe in the end I'll have spent what it would have cost to outright buy a FM2 setup but that doesn't bother me. I'm also not afraid to fail, so if it it makes it easier to watch just call it R&D at someone else's expense. :) A lesson learned the hard way seems to stick with me best anyway.

So look at it from another perspective. "If you had some idiot who disregarded all good advice given to him by those more knowledgable than he, who inisted on trying to build a cheap turbo system what would you suggest?" Other than "don't do it." Of course. :twisted:

Thanks for the advice GTIVR4, I'll probably do that. I just thought I'd try my luck here first. For some reason I'd rather be told I'm an idiot by internet characters I am familiar with. :wink:

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PostPosted: September 20, 2008, 2:50 pm 
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Chet -

Since the miata motor is basically a turbo motor minus the turbo, you should have no problem re-turboing it.

I have been away from the miata community for some time now so I cannot recall exact details, but it has been done about a billion times already with miatas so you'll find more info about turbocharging the BP than you can read in one lifetime.

The magic triangle seems to be - power, reliability, low cost - you can only choose two.
Since you already specifed low cost, it's either reliability or power that you must sacrifice, but I think you'll still be able to make some power and keep it reliable.

There are two things that you want to pay attention to -
Cooling and tuning.

You'll need to modify your cooling system.
Cooling re-route is a must, bigger or second rad, good rad fan and just about any other cooling mod possible.
This may be a bit of a challenge as there isn't a whole lot of room in the nose, especially after you add an intercooler and piping.

Tuning means either getting a new ECU or one of the other proven electic gizmos that you can learn on at miata.net or clubroadster.net .
I had the FM MiataLink on mine and even with the baseline tuning that it came with from FM it and the minimum boost which was about 5 PSI the miata was a good bit faster.
That is of course before any tuning... after basic tuning and 12 PSI of boost I got to 211 RWHP which I presume will feel like rocket on the far lighter locost.
With a bunch of tuning I got eventually to 254 RWHP and 231 RWTQ and it was fast.

Moti

EDIT - the manifold in the pic may be a bit of a problem, I don't know if it clears the frame.
It will also place the turbo pretty high which you may not want to do sice it's a chunk of heavy metal.
I'd presonally opt for a log manifold for reliability purposes and quicker spool while sacrificing some top end.

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PostPosted: September 20, 2008, 3:09 pm 
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I picked up the turbo, manifold, oil pan, downpipe, and some other misc parts off of a '04 Mazdaspeed Miata for around $500 (This is what Flyin' Miata is using on their Westfield). I will likely be using this on my locost. If you can find one, it is a good cheap alternative.

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PostPosted: September 20, 2008, 3:23 pm 
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Chinachargers!

First and foremost, figure out the power level you want. Get the car dyno'd now so you have a baseline. From there you can build as cheaply as is prudent. You dont necessarily need a new ECU but it is the only way to get everything you can out of your setup. A low power/boost setup (~5-6 psi) you can probably get by with the an auxilary fuel pressure regulator and a static timing pull. Will this give you more power at a pretty same level.

If it was me and I was going turbo on a budget. I'd get a megasquirt NOW. Learn it and make sure you understand how to tweak it. Then the turbo and plumbing. Most of the cheap manifolds are cheap for a reason. They WILL fail. This isnt a jab at you or your ability. Those manifolds often skip things the more expensive ones do... for that exact reason. It costs money. The most common is relief cuts in the manifold flange between runners. Between MiataTurbo and miata.net, I think you'll be fine.


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PostPosted: September 20, 2008, 3:56 pm 
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Thanks for the advice guys, including yours Kurt.
I definitely need to study up on the Miata boards but I found all of your comments very encouraging. I was sort of on the fence on whether or not to drop the $700 on the MS PNP but I think I'll do it. After Kurt raking me over the coals and me defiantly refusing to admit I need a tunable ECU, it does look like the smart thing to do. It doesn't cost as much as a "real" standalone so we'll call it a compromise. I really like what Fandango said about learning to tune before hooking up a turbo system. That makes a TON of sense to me.
I'm also leaning toward the meth/water injection in leu of an intercooler. I think the MS PNP has provisions to control an extra injector for just this sort of thing.

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PostPosted: September 20, 2008, 4:16 pm 
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Homebrew turbo setups can work if you pay attention to the details...
LOWER THE COMPRESSION RATIO!!! 10:1 compression is too high
unless you are running methonol. You can play around with maybe 5-7Psi
but any more and you are asking for trouble. Might as well get a set of low compression pistons for a few hundred bucks it will save more in the long run. A rising rate pressure regulator is a must. A friend blew holes in pistons once or three times by not lowering the compression( alfa motor). Detonation is a real problem with increased boost. You really need intercoolers and shaping the combustion chamber to eliminate hot spots.

It can be done on the cheap.. but it will cost you in the long run.
do it right once. Not cheap three times.

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PostPosted: September 20, 2008, 5:31 pm 
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bremms wrote:
... LOWER THE COMPRESSION RATIO!!! 10:1 compression is too high...

Alot depends on the engine and ECU. The "Honda kids" boost 10:1 engines all the time... of course they also blow them up, though the two aren't necessarily related. Everyone agrees though, it's all in the tune.

Of course I have to temper this with boost level. If you're staying at 7psi or less that causes far fewer issues than 10-15...

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PostPosted: September 20, 2008, 6:23 pm 
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I think my engine is 9:1.

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PostPosted: September 20, 2008, 10:19 pm 
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On water injection:
I agree. Given the confines of the car and packaging, I think it is a great way to go. My friend bought a kit for his M45 supercharger (now has a MP62). Exactly what he needed. Altho, he did feel like he spent alot of money for not much in the kit. If you are smart and piecemeal you can get all the parts you need pretty cheaply. Just make sure to have an BRIGHT low water light. You'd be surprised at how fast you can go thru it.

Miata B series engines (excludes MX5 2.0L MZR) are directly decedent from a factory turbo engine. Heck until ~95 the block still has an oil port on the the exhaust side of the engine for a turbo. *The passage is still there on later blocks. Mazda just did not machine it. It takes boost like a champ.

On the ECU. The reason I have a LINK on the silver car in my avatar is because I didn't want to break in my brand new built engine with turbo while getting the thru the learning curve. Chet, your wiring was from a 90 correct? I think FM still has a few LINKs running around. I'm pretty sure they are out of 90-93 ones but you might be able to change some wires to run one of the later ones. I saw FM's "Deal of the Day" had a 94-95 LINK for 750 earlier this month. Thats the most mature/installed ECU for the miata at the price of a megasquirt. I know you'll need a 1.8 throttle body. FYI- I have a spare sitting around your welcome to if you need it. ;p

On doing anything to the engine. As long as your desired power is under what ~12 psi will give you, skip doing anything fancy. I speak from experience. I still do not have enough miles on my built 1.8L to properly trash her...at least in my mind.


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PostPosted: September 20, 2008, 11:04 pm 
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chetcpo wrote:
I think my engine is 9:1.

You think that it's 9:1, but in reality it is 8.8:1 and you don't even need to open the motor to do jack sh1t before turbocharging, unless your motor needs to be rebuilt (most likely it doesn't, these things last for a long time).
The BP takes 12 PSI like a champ with decent tuning.

Regarding water injection, I'd recommend against it.
Water is heavy, it moves around and if you forgot to fill it up you can kill the motor.
There's no reason to use water inj if you want to stay within normal power limit, there's enough space for an intercooler...

BTW, you're going to need a better clutch, my stock one died pretty quickly after installing the turbo and a few good launches.
The ACT clutch that replaced it practically lives forever...

Moti

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Last edited by Blackbird on September 20, 2008, 11:17 pm, edited 1 time in total.

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