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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 02-17-2011, 08:48 PM   #1
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I didn't see a more appropriate forum to post this, so sorry if it's in the wrong place. I recently purchased a '92 Miata with a partially installed turbo on it. The person I purchased it from received it as payment for a debt incurred, and therefore knew little about it.

What I know: It runs and drives. It actually drives surprisingly well. The turbo is a TD05. And it appears as if it were a "kit" turbo, as opposed to a home-built setup. It is not currently making any real boost. It will not pass a GA Emissions test. The trunk was crammed full of "spare" parts. They appear to be extra parts "just in case" or parts off the original motor. Other than the turbo, the car is almost 100% stock. It has no intercooler. There is a blue "box" that says "Greddy E-manage" stuck in the glove box. It has wires going back into the dash-board. I was told this is the "turbo computer"
The turbo for un-explicable reasons will not go past about 2 PSI on the boost guage, and only than if I rev past 5k rpm. The outlet on the turbo is a thermostat housing, and there are a series of about 5 reducers to connect that to the rest of the intake plumbing. The mass airflow sensor box is connected directly to the turbo, but has no air filter. The down pipe looks to be about 2.25", but the stock cataletic converter is in place as well as the rest of the tiny stock exhaust.

What I want to know: How do I make more than 2 PSI of boost out of this turbo? How can I identify what has been done/changed during the conversion and what needs to be done/changed to complete the transformation. What is up with the Greddy E-manage, and can/how do I adjust it? What might be causing it to fail EVERY aspect of the GA emissions regulations (albiet just barely on all but nOx).

Ultimately, I have all of the parts to return it to NA, but I kinda like the idea of a turbo Miata. If I can't get everything to play nice, it's going back to non-turbo form, but that's a last resort. I paid $1500 for the car, and it's going in to get a leaky water pump replaced on Monday, at a cost of $200. I've decided once I sink $3k total into this car, that's it. If it's not drivable I'm cutting my losses and walking away. I've never really had a "project" car before, I've always kept my vehicles mostly stock. So even though I used to be a mechanic, the idea of radically altering the performance of a vehicle is somewhat new to me.

Sorry for the length, but I need help. Thanks in advance.
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Old 02-17-2011, 09:27 PM   #2
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How do you make more than 2psi?

Strip that AWFUL setup and build a new one. This is precisely why you DON'T buy a modified car. Sounds like the PO built a complete POS, realized what it was and sold it to the next sucker (You).

First of all, stop driving it. That emanage is complete garbage and you don't know what the tune is like. If he really used a thermostat housing a a shitton of reducers, chances are it's not even tuned right. No filter means the guy was cheap; you don't know what he cheaped out on. If you keep driving it like it is it will probably blow up.

Seriously, cut your losses, sell what you can, research and start fresh. Sell what you can, return it to stock, research, THEN turbo it. Trust me, it took me 2 tries to get it all right; you can't research this and learn it in a day, you have to research, research more, and then go do stuff. If you post pictures we can help determine what you're dealing with.

EDIT: Honest to god, post pictures. I really want to see what 5 reducers and a t-stat housing looks like on a turbo...
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Old 02-17-2011, 09:34 PM   #3
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Put it back to NA, it sounds like too many issues to be a very easy fix. If it's a $1500 miata, a lot of money probably wasn't spent on the turbo. The e-manage isn't bad, I wanna say it can be made standalone, but I have no experience with it. Search around on here.

We mega squirt here. They can be solder together by yourself or by some one else on the forum, or your third option which is the pnp, built specifically for the miata. I THINK you could get it for "free" by selling the emange

Your boost issue probably means it's not adding enough fuel. No idea which part is causing this. You'd need a wideband for that, to measure your air fuel ratio.
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Old 02-17-2011, 09:43 PM   #4
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Honestly, If I can't make it road-worthy relatively easily, it's getting sold. I work 7 days a week and don't have time to mess with this vehicle. That's why I'm paying a guy I consider to be an idiot to replace the water pump. I figure the average monkey can do a T-belt/water pump job. I just want a toy that makes me smile on the days I only work until noon, not a project that absorbs my life. I already have one major project in my S-10, I don't need another.
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Old 02-17-2011, 09:57 PM   #5
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Then take it back to N/A. Buy and eBay header to replace the turbo and leave it otherwise stock.
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Old 02-17-2011, 09:57 PM   #6
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hmmm....sell? return to NA? or fix the turbo set-up?

can you post up some pics of the engine bay and general condition of the car? if it isn't too molested and has decent compression, i'd say stick with it. $1k of modification fund can go a long way if you shop wisely.
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Old 02-17-2011, 09:58 PM   #7
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What everyone else said. If you put it back to stock, you can sell your turbo **** and then you have a running roadworthy Miata for less than 1500.
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Old 02-17-2011, 10:37 PM   #8
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I reckon, sell the emanage, buy a MSpnp, get an exhaust shop to plumb up a new downpipe exhaust and intercooler piping with a cheap ebay cooler and go make 160 rwhp?

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Old 02-17-2011, 10:38 PM   #9
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The car's body is in pretty good shape, but needs paint very much badly. My primary concern at this point at this point is to make the Miata a daily driver. I'm thinking that once the water pump is fixed and the cat/con is replaced it should pass emissions. The primary question still stands though, WHY is it not making boost? I've been told that the injectors have been replaced with those from an RX-7 at 550cc. (they've got a red-ish band at the top of them) And I re-connected the wastegate solenoid to manifold vacuum, without signifigant effect.
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Old 02-17-2011, 11:01 PM   #10
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If it's not tuned properly you won't get it to pass emissions, your best (cheapest) bet for that is to hopefully find the factory injectors, header and intake piping in the trunk. Then install that with the air flow meter in it's proper position and remove the emanage.

You need a wide band O2 sensor to tune it properly, even then it can be a pain to pass emissions and it sounds like you don't want that right now.
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Old 02-17-2011, 11:06 PM   #11
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With an unknown car, and with an unknown tune, making boost is the last thing you should be concerned with. It is possible that you're going to get into detonation past 5/6psi, and then you're going to have a MUCH bigger project than you thought you had. I'll humor you though.

1. Turbo CHRA (the spinny part) is broken - if there's no air filter, the likely cause is debris entering and destroying the compressor blades. Other potential failures are turbine blades, and failed bearings.

2. Wastegate - at no boost, it should have a preload which holds it closed with some decent amount of force. If you can find a sports ball hand pump and connect the vacuum line to it, you may be able move it back and forth to prove it's correct operation. If it's an adjustable spring wastegate, it may be set with an extremely weak spring.

3. Intake plumbing. If any of the joints from the compressor outlet to the throttle body are loose/torn/etc, you'll blow pressure out.

4. Bypass/blowoff valve. If this is hooked up incorrectly/not functionig properly/weak springed, it will leak off all your boost.

5. Boost gauge. If your boost gauge is fucked up, its possible that you're running 86psi and don't even know it.

Let me say this again though - if you "fix" your weak boost, you may very well destroy your engine if your fueling/ignition systems are imsufficiently set-up. It's possible that the PPO knew he had gotten too far over his head after he did a simple hardware install and it sat for several months before he gave it to someone. If he had to use the car as payment for services rendered, he likely didn't have very much money wrapped up into getting it set up right.
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Old 02-18-2011, 12:02 AM   #12
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+1 Above

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Old 02-18-2011, 01:36 AM   #13
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You're fucked and I would not trust an average monkey to do my timing belt and water pump. No way. AFter a shop that works on maitas day in and day out fucked up my timing belt job 3 times in a row I decided that if anyone was going to **** it up, it would be me.


Your car is so far from daily driver status that it is a pathetic joke. I think it would be best if you crashed it into a wall and had insurance pay out on it because you're just fucked.

Just get rid of it and buy a nicer non-turboed miata and drive it and have fun. Unturbo'd miatas are great gobs of fun and you can ***** on them so hard and they will last forever. If you are still interested in turboing do a lot of reading because the learning curve is expensive and steep.
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Old 02-18-2011, 01:42 AM   #14
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good 'ol fae thure is thuch a thweetheart
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Old 02-18-2011, 05:38 AM   #15
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I'm fairly certain that the boost guage is correct. It sweeps through the vacuum side like it should, and when I do actuate the blow-off valve, it sounds very weak. And as it's one of those silver and purple monstrosities that are designed to be as loud and annoying as possible I'm very certain it's not building pressure. I took all the intake piping off and grasped the compressor wheel on the turbo and it seems fine, having no detectable play. I looked at it closely and saw no apparant damage. My primary suspect right now is the wastegate or actuator for same. It does not seem like it is moving at all. It is also my assumption that the reason that it won't pass emissions is that it is not building boost, but is getting enough fuel for the boost it should be making, therefore running rich. It ust be a fairly recent problem, as it has a current emissions status from the last owner (though under GA law it still must be re-tested by each new owner)


Some other things that might be pertinant. The clutch has been "upgraded" to a higher pressure unit. The turbo is mounted above the manifold, not below as many pictures I've seen around here seem to show. Tonight I'm going to be re-routing the piping somewhat and trying to get an air filter in place. I'm also going to remove the wastegate actuator and try moving the wastegate by hand to make sure it will actually move.

Many thanks for the responses so far.

Last edited by Paramedic; 02-18-2011 at 06:03 AM.
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Old 02-18-2011, 10:25 AM   #16
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Every single correct fueling option should be adding fuel based on how much air/pressure is in your intake manifold (or flowing through it). In practice, if you add 30% more boost, your fueling system is going to add 30% more fuel. There shouldn't be a way for your car to calculate how much boost you're "supposed" to be making, only how much boost you actually "are" making. You have a picture or three of the engine bay? Is your car running the stock AFM and a BOV? If so, you'll need to switch to a bypass valve setup - your valve should be reintroducing the spent air pressure into the intake system between the AFM and the turbo.

Might want to check to be sure your greddy e-manage is actually connected to something on the other end. Find the original injectors in the trunk and stick them on and you may very well pass emissions.
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Old 02-18-2011, 07:08 PM   #17
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Well, the boost issue is (temporarily) resolved. I don't know why I didn't see it sooner. Even though there was no air filter per-se, the previous owner had taken some window screen and...felt?...and fabricated something like an air filter over the mass airflow sensor. It was nearly completely occluded. I took it off and I am just running the sensor wide open now. Sure enough, it's boosting up to 6 lbs at 5500 rpm. I know the engine can rev past that, but with a badly leaking waterpump I didn't want to beat on it too badly.

It runs super smoothly now and has decent power. As time permits I'm going to completely re-plumb the intake and integrate an Isuzu NPR intercooler I have lying around along with an air filter. I also need to open up the exhaust from the Cat back. I have a couple of maintnance fixes, cosmetic parts to be replaced, minor noises to track down, lubricate the power windows, and figure out why every time I hit the slightest bump the car nearly flys off the road. But I'm confident it will pass emissions now that it can breathe so it can be a drivable project car rather than a lawn ornament.

Again, thanks for the help.
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