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Old 06-15-2008, 07:35 PM   #1
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Default Denooberizing myself.

Greetings everyone! My name is Jim.

I'm really happy to have found and to be joining this great web forum, and I'm looking forward to learning from all those folks who have turbo charged their Miatas. I’m new to both Miatas and turbos, but damn glad to have discovered both this past spring.

Along that line, my son, who just turned 17, and I are planning on installing a BEGi S2 or S3 kit on my wife's essentially stock newly purchased '95 M/T Miata with 66k miles. We chose a ’95 for the tougher rear end and the absence of the OBDII. It came from the previous owner with a Jackson CAI, which I'll sell, and a Borla catback, which I'll keep. Other than that it's a clean slate car in excellent mechanical condition.

We've both read Corky's book "Maximum Boost", and Warner's book "Street Turbocharging". For good measure I also had my boy read "DeskTop Dynos" by Atherton, and "Power Secrets" by Smokey Yunick. Finally, I've printed and bound Braineack's excellent "Things you need to think about before turbocharging your Miata", as well as the compressor efficiency maps for the two turbos I'm considering (GT2554R and GT2560R) off of Garrett's website.

So here's were we're at....

Living in Fairfield California, where Sleeper was recently nabbed and sent to the REF's for running a non-Carb compliant system, any setup has to be CARB approved. This pretty much means BEGi only, though I’m perfectly happy with their offerings. On the other hand, someone recently posted BEGi’s E.O. 349 but that E.O. doesn’t seem to cover the Garrett turbos presently used in Corky’s S2 and S3 systems. If someone knows of a later E.O. for BEGi’s current kits that would be great; otherwise it will be a question I ask Stephanie next week.

We’re also limited to 91 Octane fuel here which means 8-psi boost or less if I want to keep things simple and costs reasonable. With that level of boost I’m guessing around 185 bhp while keeping stock injectors. That’s all fine for now because it means the stock suspension, brakes, clutch, and cooling system should also be adequate, and the fuel consumption penalty should be reasonably small. After I become numb to the financial pain of sending my young mechanic to college next year I’ll look towards the higher hp systems; for now we’re using the wife’s ’95 as a learning tool.

From Garrett’s website I put together a simple Excel spreadsheet which calculates Flow Rate (lbs/minute), Boost Pressure, and Pressure Ratio for a given horsepower. Based on Garrett’s approach 185 bhp requires about 7.9-psi boost, a 1.8 pressure ratio, and 20.4 lbs/minute flow rate. When these values are plotted on Garrett’s compressor efficiency maps for the GT2554R and GT2560R turbos the operating parameters are right in the sweet spot for both turbos. Both turbos also have room to grow (for later), though the 60R can grow a bit more. As for the Area/Radius ratios the smaller turbo has an A/R of 0.80 verses the 60R’s A/R of 0.60 which seems to give a slight advantage (less exhaust restriction) to the smaller 54R.

So much for theory.

I’ve got to choose between one turbo or the other. I’m more of a back road scratcher than an open road blaster and the tighter the corners the better. Practically speaking this means the quality of the power is more important than the quantity, and either system will generate plenty for what I’ve got in mind for now or the near future. My wife will also commute in this car (yawn).

So my question is, will the lower boost threshold of the smaller turbo be too low for normal commuting, or will the higher boost threshold of the larger turbo be too high for back road scratching? You'll notice I've avoided the seemingly stupid, but so practical question, "which is the better turbo", but your practical advice and experience with either system would be much appreciated. Also, is there anyone in the Bay Area who could possibly give me a peek at either of these two turbos?????

Thanks everyone!

Jim

Last edited by Thucydides; 06-15-2008 at 07:46 PM.
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Old 06-15-2008, 10:00 PM   #2
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I think that's the finest "first post" I've ever read. ****, after that, you're not even a NOOB anymore. Well done!!!

Since it looks like you're going to be damn thorough with this thing, I have a suggestions that might help you with your CARB compliance and get you everything you really want out of the car.

When you order your kit, make sure they slap on an extra 02 bung on the downpipe direcly below where the shifter will be... and get yourself an LC1 wideband.

Then do homework into a Megasquirt PnP. Since it's a direct plug-in, there's no cutting of the factory harness. For simplicity, you can even keep the factory MAF in place and not utilize the MAF-delete option... or DO use the MAF delete but leave it installed.

Install the AFPR needed for the CARB sticker but only hook it up on days you go to the SMOG station (one day per year). Beyond that, the only other things you'll need to change on SMOG days are the injectors and swapping back in the factory ECU, and plugging in the MAF connector.

If you wanted to be really slick, you could have 2 different cold-side pipes... one with the AIT sensor in it, and one without... swap them too and you can go from fully CARB compliant to full standalone with ZERO evidence of the latter in about 1/2 hour. (add about 15 minutes to swap the CAT back in for the test-pipe you'll be sure to want as well)

The high-flow fuel pump you'll need with the AFPR will not affect performance or function when you bypass it and run the larger injectors with MS.

If you swapped the 2 turbo's you're considering into the same car and did back-to-back runs at the same low boost level you're talking about (8-10psi), I think you'd see abuot 100rpm quicker spool response from the 2554r, and virtually identical power plots. When you're up in the 15psi range, the better efficiency of the 2560 will definitely show it's advantage, but it's just not enough under 200whp to justify the extra cost IMHO.

OH, and 185whp does not mean the stock clutch. You are a prime candidate for an ACT HD w/street disc. The stock clutch will not hold the kind of power you're talking about.
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Old 06-15-2008, 10:04 PM   #3
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Quote:
Originally Posted by Thucydides View Post
Greetings everyone! My name is Jim.

I'm really happy to have found and to be joining this great web forum, and I'm looking forward to learning from all those folks who have turbo charged their Miatas. Iím new to both Miatas and turbos, but damn glad to have discovered both this past spring.

Along that line, my son, who just turned 17, and I are planning on installing a BEGi S2 or S3 kit on my wife's essentially stock newly purchased '95 M/T Miata with 66k miles. We chose a í95 for the tougher rear end and the absence of the OBDII. It came from the previous owner with a Jackson CAI, which I'll sell, and a Borla catback, which I'll keep. Other than that it's a clean slate car in excellent mechanical condition.

We've both read Corky's book "Maximum Boost", and Warner's book "Street Turbocharging". For good measure I also had my boy read "DeskTop Dynos" by Atherton, and "Power Secrets" by Smokey Yunick. Finally, I've printed and bound Braineack's excellent "Things you need to think about before turbocharging your Miata", as well as the compressor efficiency maps for the two turbos I'm considering (GT2554R and GT2560R) off of Garrett's website.

So here's were we're at....

Living in Fairfield California, where Sleeper was recently nabbed and sent to the REF's for running a non-Carb compliant system, any setup has to be CARB approved. This pretty much means BEGi only, though Iím perfectly happy with their offerings. On the other hand, someone recently posted BEGiís E.O. 349 but that E.O. doesnít seem to cover the Garrett turbos presently used in Corkyís S2 and S3 systems. If someone knows of a later E.O. for BEGiís current kits that would be great; otherwise it will be a question I ask Stephanie next week.

Weíre also limited to 91 Octane fuel here which means 8-psi boost or less if I want to keep things simple and costs reasonable. With that level of boost Iím guessing around 185 bhp while keeping stock injectors. Thatís all fine for now because it means the stock suspension, brakes, clutch, and cooling system should also be adequate, and the fuel consumption penalty should be reasonably small. After I become numb to the financial pain of sending my young mechanic to college next year Iíll look towards the higher hp systems; for now weíre using the wifeís í95 as a learning tool.

From Garrettís website I put together a simple Excel spreadsheet which calculates Flow Rate (lbs/minute), Boost Pressure, and Pressure Ratio for a given horsepower. Based on Garrettís approach 185 bhp requires about 7.9-psi boost, a 1.8 pressure ratio, and 20.4 lbs/minute flow rate. When these values are plotted on Garrettís compressor efficiency maps for the GT2554R and GT2560R turbos the operating parameters are right in the sweet spot for both turbos. Both turbos also have room to grow (for later), though the 60R can grow a bit more. As for the Area/Radius ratios the smaller turbo has an A/R of 0.80 verses the 60Rís A/R of 0.60 which seems to give a slight advantage (less exhaust restriction) to the smaller 54R.

So much for theory.

Iíve got to choose between one turbo or the other. Iím more of a back road scratcher than an open road blaster and the tighter the corners the better. Practically speaking this means the quality of the power is more important than the quantity, and either system will generate plenty for what Iíve got in mind for now or the near future. My wife will also commute in this car (yawn).

So my question is, will the lower boost threshold of the smaller turbo be too low for normal commuting, or will the higher boost threshold of the larger turbo be too high for back road scratching? You'll notice I've avoided the seemingly stupid, but so practical question, "which is the better turbo", but your practical advice and experience with either system would be much appreciated. Also, is there anyone in the Bay Area who could possibly give me a peek at either of these two turbos?????

Thanks everyone!

Jim
Hello Jim. I must say I'm impressed by your presentation. It shows you've really done your homework.

I'll leave the technical questions regarding which of the 2 turbos to pick to those more knowledgeable but I'll make a suggestion: change the car's suspension if you really want to enjoy the back roads!

I'm also blown away by the fact that you plan on doing those mods to your wife's Miata! My wife won't even drive mine!

Thanks for the info on those books. I'll check some of them myself (I already read "Maximum Boost").

Welcome and enjoy your stay.

Now, pics or ban!
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Old 06-16-2008, 12:25 PM   #4
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Hey, thanks Samnavy and Rafa.

Yep, I'm pretty sure a Megasquirt PNP and larger injectors lie in my future; if not sooner than definately later. And Samnavy, a second bung comes with that pretty divorced SS downpipe from BEGi, but I'll check the location before I finalize things. I have planned on the Innovate G3 gauge and LC-1 at the same time I get the turbo, and even though it's full capacity won't be realized until I have a stand alone ECU it should really help monitor what's going on with the fuel system.

Anyway, thanks for the great advice, particularly about the setup and swaps for smog check day. I won't have to re-smog for almost two years, but if you live here it's in the back of your mind a lot.

Cheers.
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Old 06-16-2008, 12:39 PM   #5
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the 2554 will turn on fast, but if your aren't expecting to make over 200rwhp with it, it simply makes the car feel like a larger displacement motor. the 2560 is a great all around turbo, it still spools fairly quickly and has a higher power range to boot. it's ultimately what you want out of the turbo.
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Old 06-16-2008, 02:06 PM   #6
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Quote:
Originally Posted by Thucydides View Post
Hey, thanks Samnavy and Rafa.

Yep, I'm pretty sure a Megasquirt PNP and larger injectors lie in my future; if not sooner than definately later. And Samnavy, a second bung comes with that pretty divorced SS downpipe from BEGi, but I'll check the location before I finalize things. I have planned on the Innovate G3 gauge and LC-1 at the same time I get the turbo, and even though it's full capacity won't be realized until I have a stand alone ECU it should really help monitor what's going on with the fuel system.

Anyway, thanks for the great advice, particularly about the setup and swaps for smog check day. I won't have to re-smog for almost two years, but if you live here it's in the back of your mind a lot.

Cheers.
If I were you I'd go with the AEM Uego for a WB; easier to set up and it includes a gauge.
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Old 06-16-2008, 04:34 PM   #7
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woops....screwed up....

Last edited by Thucydides; 06-16-2008 at 04:41 PM. Reason: Actually, screwed up multiple times....
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Old 06-16-2008, 04:37 PM   #8
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I'll make a suggestion: change the car's suspension if you really want to enjoy the back roads!
You see, Rafa, this is how it works when you've been married a few years....

H: Hon, wouldn't it be great fun if your Miata had a few more HP?

W: Sure, that sounds very nice. It won't cost much, will it? Ok, let's do it.

Some months later after turbo install....

W: Holy hell, this thing is scaring the crap out of me. It doesn't stop any more and it won't turn either. Can you do something about this before I kill myself?

H: Sure, no problem. Only need to spend a few bucks, dear, that's all.

Some months later after big brakes, shocks, springs, adjustable mounts, sway bars, etc., etc., etc....

W: Dear, I know the Miata's running just like it's supposed to, but you know it doesn't feel as fast as it used to.

H: Yeah, I know what you mean. Don't worry, I've got a plan. Just need to spend a few bucks, that's all.

Some months later after methanol injection, COP, huge injectors, much larger twin turbos, three intercoolers, 4" dual exhaust, afterburner, JATO, etc,, etc., etc.,....

W: HOLY MOTHER OF GOD. How the hell am I supposed to drive this thing?!? The body twist's up everytime I merge on the freeway, my neck always hurts from being snapped back, and it's so freeking loud you say you can't hear me when I scream at you to slow down. Can you do something about this, this, this, HELL, I don't know what this thing is any more!

H: No worries dear, I've got some ideas. Just need to spend a few bucks, that's all.
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Old 06-16-2008, 05:52 PM   #9
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^ lol!

Wait till you get to 30 years married!
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Old 06-16-2008, 07:37 PM   #10
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I dunno Rafa. After 22 years she's beginning to beef up the life insurace policy on me. I hope the car doesn't fall off the jackstands while I'm working under there; it would be nice to drive it at least once with the turbo in it before I go.
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Old 06-16-2008, 08:50 PM   #11
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Welcome and goodluck with the project.
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Old 06-17-2008, 06:40 PM   #12
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Welcome, major props on great intro, you will be very well accapted.
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Old 06-17-2008, 10:25 PM   #13
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Awesome intro bud!

A bit of personal experience that may or may not help you. I went with a T3/T4 setup, and from time to time I wish I had gone a bit smaller with the turbo. You've done your research well, but I think that you may be nitpicking the turbo choice a bit. Both the turbo's that BEGI offers you will be fun and have a great powerband, but I think that if more power is in your future, you might as well go with the larger unit now rather than later. Most times I am satisfied with the power delivery of my much larger turbo, but if I were to switch out to something I think would be nearly perfectly responsive with plrenty of HP potential, the 60 would quite possibly be my choice
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Old 06-17-2008, 11:50 PM   #14
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Thanks cjernigan, Zabac, and airbrush1. It's great to have a place like this to ask questions and get meaningful answers.

Jim
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Old 06-18-2008, 12:23 PM   #15
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i have to agree with everyone this is the best intro post i've ever seen on any forum. congrats on that.

I just got done installing my gt2560 and i love it, the 2554 would spooled up a little quicker but this feels amazing. I'm at only 6psi right now and it feels like i could take on anything, i can't wiat till i turn it up to like 12-15psi.....basically go with the 2560 because it'll still spool quickly and give you room to grow....hell paul is making 300whp on the 2560 so it can't be that bad
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