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|11th September 2008, 05:43||#1|
Senior - BHPian
A Turbo Miata story
So I've received quite a few requests to start a thread about this car, and I'm finally doing it today since I have almost nothing else to do :-D.
Its the story of my homegrown turbo setup and how it came to be. What follows is quite long and boring at times so be warned.
It all started back in January after driving scooby's Subaru STi. The torque and the adrenaline rush was worlds different compared to the relative docility of a stock 1.6 Miata (which BTW feels quite a bit senile than the race-prepped dolphin that's sitting back home in India, no not the blue one in my garage )
So, I thought to myself, why not turbocharge it? Really, for the Miata, there's no power mod with a better price-to-performance ratio. Plus, with the available aftermarket support, anybody with half a brain can throw a kit together. I searched everything available and found nothing within my budget. And that's why I decided to put my MAD INJUNeerING sKILLz to use and do a full custom build.
The only issue was that, at the time, I lived in an apartment with no enclosed parking, so heavy fabrication or welding was out of the question.
For those few people sneering at the crudity of some of the fabrication work sitting in India, consider that there is no chotu available here to work for Rs. 50 + chai-paani a day. All work was performed by one man, me, in my apartment parking lot, sometimes in 5 deg. C weather. If I had my regular chotu guy here imagine what would have been possible.
My initial budget of $500 for the turbo proved to be a little optimistic once I scanned the forums and ebay for parts: its possible only if you're extremely lucky, or if you can live with compromise. I don't have either luxury, so I quickly doubled the budget to $1000. In the grand scheme of things, this is very very cheap because an aftermarket kit of equal performance can cost twice to three times that amount.
I started with a design philosophy. Throttle response and engine flexibility were of paramount importance because this car is meant to fly on the track, not live life quarter mile at a time. Scalability was very important, as I'm fairly human in nature and keep wanting more after a while. I wanted a good streetable setup with excellent performance during autocross too. I could later upgrade it if I felt the need to beat that Corvette on the track (don't laugh, it can and has been done).
With that, I laid out some goals, limited only by my financial capability to replace broken differentials and gearboxes at the time:
200 bhp peak power
Full boost by 2000 rpm
Flat torque curve between 2500 and 5500 rpm for auto-x purposes.
Turbo choice was therefore very important. After a lengthy discussion on MT.net, and my own analysis of different compressor maps, I zeroed in on the TD04-13T turbo from a 02+ Subaru WRX. Although very few people have been known to use this turbo (I can count them on one hand with fingers to spare), my analysis was validated by a couple of dyno charts I saw online. 200 bhp was well within reach at less than 0.7 bar boost. This turbo is really a wonderful piece of modern turbocharger practice, a hybrid-turbo straight from the factory: it is a fast response, low inertia, oil+water cooled, and flows well over 350 CFM of air, i.e. worth 250-300 bhp mated to the right engine.
Shopping started with the turbocharger which I found on a subaru forum for less than $150. Then I found a guy on the local forum who was selling a custom manifold built specifically for this turbo. Imagine the odds!!
With the major components out of the way, I pieced together all the major bits over a 3 month period, scrounging the local forums, ebay and other car forums like a crow :-D. MAN that was intense. This was what I had at the end:
Of course, some parts were not used, like the intercooler and downpipe. I ended up using a Mazda MX6 intercooler and some used miata-specific charge pipes, cause they were available for less than $100 with brand new silicone couplers . The sizing is also perfect for the hp level I intend to run. Here are some pics during the intercooler mounting phase:
This is the final mounting:
The mounting is solid and well-constrained with "give" in the right places so engine vibration wont tear the brackets apart after a couple of events. I also managed to shorten nearly 15" of the original charge pipe routing. This is a very unusual mounting technique, and is not ideal for the track due to lower ground clearance. I hope to change the entire intercooler setup once I can afford something better.
The intercooler as seen from the outside of the car, yeah I know, you can't see it :
Next up was drilling and tapping the oil pan. This is a delicate and complex process, specially when lying under a car while holding a hand drill with an oversized bit in it. You have to be real careful not to hit the oil pickup tube which is placed right where you break through the metal. If you do, the oil pressure drops to 0 psi and the engine has to be taken out for it to be replaced.
But I simply used some PTFE lubricant, and drilled a pilot hole, VOILA done in 15 minutes:
I sanded and painted the manifold with BBQ spray paint. Quite a useless chore as I have found it flaking after barely 500 miles of use:
I mocked up the downpipe and tacked it with the help of a local forum member. I tuned his ECU so in exchange got him to tack weld my downpipe. In the parking lot. With a 50 ft. extension cord from my apartment :-D. Yeah, I've been called crazy hardcore a couple times before.
It is a 2.25" standard flanged, mild-steel downpipe:
The DP is designed for two things: easy upgradability to a divorced style dump tube, and serviceability. The lower section of the downpipe has a flex section in it and goes straight to the catback (no cat). It is just fastened with a slip-on style clamp. There's no need to remove even the turbo or jack up the car to remove the downpipe, it can be pulled out straight from under the hood. And its very easy to mill the flange later for a dump tube.
I bought a used ebay exhaust for $100. Its a 2.25" SS and quite nice for the money:
Finished it off nicely with a used $20 boost gauge. The stereo plug on the blankoff plate is the RS232 port for the standalone ECU, talk about stealth:
Engine bay after install:
Last edited by Rehaan : 15th September 2008 at 23:17. Reason: 2 smileys per post max.
|11th September 2008, 06:01||#2|
Senior - BHPian
So, at the end of 6 months and about $1000 poorer, I was done. I spent the first 500 miles doing datalogging and tuning the mixture and timing close to perfection.
The results? What can I say. The car was a BLAST to drive even with the ~6 psi it developed at the time. The spool was just terrific, positive pressure by 1500 rpm, and at wastegate opening pressure by 2700 rpm. There was a little bit of creep, upto +1.5 psi at redline. The creep was happening either because of my retarded spark map (pun intended) or the restrictive exhaust. The first one has since been solved. The exhaust will be taken care of later.
But then, I started to get greedy after the first 1000 miles, and since my ECU is capable of closed-loop boost control, installed a solenoid in the wastegate line to up the boost to 10 psi.
After a whole lot of tuning and dialing in the system, I am finally at the point where the car is scary fast, IF I can get the clutch to hook up. Unfortunately I am the only one who can get it to do this, every other person who has driven the car cannot get the clutch to hook up for some reason. ScoobySTI, your comments please
Within reason, it is completely irrelevant in what gear and RPM you are. The car responds instantly and squats hard on the stock suspension any time you mash your right pedal into its friend the carpet. The whoosh of the compressor can be heard through the filter, and the kick in the pants that follows is just phenomenal. Whats notable is the sound. The sound changes distinctly when the boost goes past 5 psi. It changes from a faint wind noise to a very aggressive whoosh until the wastegate opens at 10 psi. Of course, you are busy trying to gauge how much distance you have before you make friends with the rear axle of that semi in front of you.
When I pull up at a stop light, heel'n'toe' ing my way in, people think ok the guy drives a chic car with a fart can exhaust, how more gay can one get? I can literally read that off of the smirk. Once the light turns green though, the smirk is wiped off quite fast. Same thing happened to the guy with the Mustang GT, Subaru WRX, 08 Civic SI, and several "tuned" JAy-dEE-eM cars. The reactions I've gotten at the following stop light range from "nice car, dude" to "my clutch was slippin" to a solid . So that's my turbo miata story.
|11th September 2008, 06:22||#3|
Senior - BHPian
of course, this is just the beginning. The car will be campaigned in the 2009 NASA TT championship if things pan out the way I hope they should. The things planned out for this winter are:
Replace clutch and uprate differential to a LSD.
The present engine is past 154k miles. Thats 250,000 km for the uninitiated. I need to look into replacing the engine with another or re-build this one.
Rework the suspension. Tuning the suspension is going to be a tough task but I'm hoping my new job will teach me everything I need to know.
Get new tires on some wider wheels. Right now I am running a set of MR2 wheels because I got them for cheap. I need to go to 15x7 or even 15x9 and a set of 245's to be competitive.
Uprate the cooling system. Up here in Michigan on the street there are no cooling problems, but on some of the tracks down south I might have a problem.
Install a roll cage and race seat.
Install EGT gauge and replace the intercooler with something better.
Lose some weight, both from my body as well as the car's.
Suspension development will be done this fall. I am working on getting the requisite knowledge and tools. After it gets too cold to drive, the rest of the work will be done.
Last edited by ananthkamath : 11th September 2008 at 06:25.
|11th September 2008, 06:37||#4|
Join Date: Jul 2006
Thanked: 21,061 Times
Excellent writeup. loved reading it and followed with great pictures. Must be a great feeling to do every little bit by yourself and see the fruits of your labour.
Just wanted to ask if the brakes sufficient? I don't see any brakes upgrade in your to-do list or did I miss that out.
|11th September 2008, 09:03||#5|
Join Date: Jul 2005
Location: Bangalore (the city of modded cars) !!
Thanked: 35 Times
Infractions: 0/1 (10)
Thats an excellent write-up Ananth. I am sure it must be mighty satisfying to see the results, specially after doing a DIY.
AdvancedJDMParts.com - Performance Parts and Accessories - TURBOCHARGER
The turbos are available for quite cheap here. But I am not sure if they are worth the money or perform as good as the original garrett's for eg.
Everything else looks neat. And thats a pretty comprehensive set of pictures depicting every stage of the installation. Good luck with the future updates and events. Do keep us posted on the developments. And yes, congrats.
|11th September 2008, 09:57||#6|
Join Date: Mar 2005
Thanked: 60 Times
Brilliant writeup , and an amazing info for "do it yourself" turbo freaks. The denso intercooler wasnt used?
|11th September 2008, 10:29||#7|
Senior - BHPian
Join Date: May 2005
Thanked: 862 Times
Great post Ananth. Your'e a helluva DIY guy. Congrats on your Miata turbo success. The rear wheel turbo feel is something else.
I noticed one thing though, you have sacrificed the left a/c vent to plonk in a boost meter. Im sure you must have disconected the a/c ducting leading to that vent, just curious if it creates/will create any problem blowing the rear of your meter with cold air everytime you hit the a/c switch.
The job is clean and delicious. Not to mention, 10psi of boost must be catapulting the roadster to almost supercar territory. Stock internals? Which ECU?
|11th September 2008, 10:59||#8|
Join Date: Oct 2007
Thanked: 3 Times
great write-up Ananth. Congrats for your successful Upgrade. Would love to see some videos if you could post them here.
|11th September 2008, 11:10||#9|
Join Date: Mar 2006
Thanked: 3 Times
Hey congrats on your build Ananth, 200 Bhp on that car will be pretty good. Nice write-up too.
|11th September 2008, 11:32||#11|
Join Date: Feb 2006
Thanked: 354 Times
Even if it is a very long read, enjoyed every bit of it.
Surprise is that you were able to complete the project with just $1000 though i hear people charging more than $2000 for a turbo job.
|11th September 2008, 11:34||#12|
Join Date: Mar 2008
Location: Minneapolis, MN/Hyderabad
Thanked: 2 Times
Good stuff. Putting together a complete setup for $1000 is nearly impossible, nice work. What car did the intercooler you actually used come off of? Volvo? Boost is addicting, welcome to the darkside.
Last edited by HPP : 11th September 2008 at 11:37.
|11th September 2008, 13:10||#15|
Distinguished - BHPian
Join Date: Jul 2007
Thanked: 3,526 Times
inspirational and scary. Among doing all this DIY and suchlike, where did you get the time to put 154k miles?
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