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Sigmafour Sleeper

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This is a fully revised build thread. Back in 2013 there was an effort made to get close to 400whp on stock pistons. It didn’t really work out for a couple of reasons. Mostly the car was tuned for methanol and while that did protect pistons under boost there is no margin when the methanol fails which it used to do, often! A lot has been learned since.

Many things have been done since this thread was first made, all of the pictures were in fact lost when the back end server failed in 2014. I have restored most of them and where there are images missing still I will try and locate them as I can


This build was the first of several as it turned out. I will post some more threads which will tell the whole story. At the start of this thread I was at a nice 333whp/375wtq build which was fairly average for go fast parts bolted on. The car ran great but I went after more! After changing out the BNR HTA68 for a 20G with some additional mods I managed to eek out a bit more power still with stock internals to 403whp and 450wtq (measured on a rather ambitious dynopack, don’t believe these numbers mean all they say!) The car was very drivable and fun. You would never know much had changed unless you put your foot down, this was at the time my daily driver still!

This thread also contains a lot of my interior mods too. I tend to build function over form so it’s not the most pretty car but it still exists today just in another form! For the whole story of what’s happened since 2013 you will have to watch for my next thread. This is an update on where I was and a chance to restore the images and re-tell the story of “then”

April 2023 - After the update all the image links are broken. For the third time I will fix them and I guess I should finish these threads. So much more to the story, car is still around too. How the hell do you insert inline images now?

<img src="https://www.sigmafour.net/lgt/dyno040613.jpg">

Updated Component List:


Built with the guidance and assistance of Alberto at Motive Autoworks

BrenTuned - 403whp/450wtq (Very optimistic dynopack numbers)

AMR cx500 Turbo

Perrin Heatshield

Plugs -1 colder

Spearco TMIC/Custom install

Forge BPV

Perrin Equal Length Headers/Gently wrapped

Perrin Up

Invidia Catted Downpipe

Borla Exhaust

DW60c fuel pump

DW850cc injectors

Agency Power Fuel Rails

TGV Deletes

Wiseco 99.5 Pistons

KillerB Oil Pickup and Baffles

Sti Oil Pump

AEM Sti Intake

AEM Dual location Methanol Injection

Exedy stage 1 clutch

Bilstein HD shocks

AVO Front and Rear Braces

GroupN mounts

Eibach Springs

RalliTEK sways/Cobb endlinks

Upgraded Brake components - nothing much to talk about, not a BBK but definitely working properly!




Custom grill

JDM Double Din

STi Performance Pack Gauges


AEM Methanol Flow Gauge













Bren at work tuning the car back in March 2013...


So I started at 333whp/375wtq - a nice quick reliable car. 740cc injectors and the HTA68 worked well together. I wanted just a little bit more and with E85 not a viable fuel near me, methanol Injection was going to be the way to go... then things got out of hand.




It was January and the tune date was set for the end of March so I had time and I was in no rush. There was a plan ahead I needed gauges to be able to tell what's going on, the wideband needed a bung welded in the down pipe and it seemed like a good day to wrap the up and down pipe too. This turned out not to be as easy as it looked. I am always grateful for Alberto (of Motive Autoworks) who is a patient and experienced engine builder, one of the very best out there and he has been a constant in everything I have done with this car.





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To install the STi gaugepack, I had to move my headunit from the cubby slot so FINALLY purchased the JDM double DIN kit and ripped out the uselessfactory radio. Also added the Perrin dual gauge pod and installed the AEM Wideband gauge.











I have NO idea what this was trying to tell me. if anything it slowed me down trying to work it out, good thing there are pictures!




The methanol kit arrived... but while I was at Alberto's...




... things took a different turn. See there was this Turbo sitting on his shelf... An offer was made I couldn't refuse and then the build plans got more serious.




I knew I needed a bigger intercooler and I wanted to stay top mount. At the time this was well before Grimmspeed made their TMIC and I needed something better than the Process West. Spearco made a limited number of TMICs for the 08+ WRX and this thing was just huge, hard to find but a great intercooler!




Still with the HTA68 in the car - we fitted the Spearco





And you can see how much bigger it is over the stock part, never mind just how DEEP it is...




and I had a plan for the splitter




and finally an idea what to do with this tiny opening too...



Edited by sigmafour
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Time to start installing the methanol kit.






This took a long time to install nicely and safely but you want to do it right when running such a dangerous fuel through the passenger compartment!










I put the controller here on a long length of wire so it could be bought up onto the dash during tuning and adjusting. It fit nice in this space and I used velcro to line the space and on the back of the controller. It's very easy to get to and push the test button if needed and it's simpler to install here rather than extending all the cables and vac line over to the glovebox where I see a lot of these end up.



Also prepped the new EL headers - very lightly wrapped with 1/4 overlaps to allow some heat to escape. It is not recommended to wrap these types of headers. No warranty this way, Perrin makes this very clear.





The picture above shows one of my first of many mistakes. It said quite clearly on the package for the titanium wrap NOT to spray it down with Hi Temp silicone coating. I did and the result was fairly rapid disintegration! Don't spray the titanium header wraps!



Now it was time to do some of the major changes for this build. Fuel rails, TGV deletes and whatever. This was a very long day of work and without Alberto's help I couldn't have made it. Alberto is extremely knowledgeable on how these cars are put together and so with his guidance we got everything done and installed the lager 20g turbo and updated with a base map for the larger fuel injectors at some point in the wee hours of the night!









Edited by sigmafour
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You should never underestimate how much time these things take to work on! What starts as one task turns into many not withstanding the time you spend dealing with issues like fuel leaks or playing the game of where did that bolt go?


Alberto often says to me people do get upset with the labor time on some jobs and working on a custom car adds hours of effort to get things right. Working on just the gauges myself and seeing an entire weekend vanish doing the wiring properly which is exactly how Alberto does it, I completely understand. You can throw things in a car and it looks exactly like you did but to do it right is time and effort and a lot of these things have to be done right or you will end up with a serious fire. We didn't finish all of the above until 1am and we started at 10am - some lunch and whatever time passed as we were high on fumes but my appreciation for Alberto's work is so much more understood.


The last part of this was to finish a few things... Wiring up the Meth lines, finish the controller, install the failsafe gauge and to carry out my plan for the splitter.












And now...



I may be ready for the dyno

Edited by sigmafour
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I follow Bren on instagram and just yesterday asked him about your car. I had a question about using the spearco intercooler with a sti style turbo. I was looking into getting into that but wasn't sure. I currently run Process West but would like the bigger setup.

Sleeper setup. wont even know what hit them.

How you like that AMR Turbo on the street?

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@gordata - The Spearco was a direct fit for the car because we share the same engine/TMIC setup as the 08+ WRX - If you are going with an STi Turbo do you mean it will be rotated or direct fit? Pretty sure with patience and ingenuity you can make anything work!


Here's what this was really about - Can you really have FMIC performance with a TMIC and the answer is definitely yes!! This is a huge intercooler - heatsoak issues be damned, we're moving almost all of the time and unless drag racing is your thing heatsoak is just not an argument worth making. This core doesn't heatsoak badly either, not over any short red light stops it's just too big to really warm up over the well insulated Turbo! It cools quickly and efficiently when moving and the hood scoop which I will cover in some later pictures can be made to work perfectly.


AMR on the street - it's great. Yes, a little more lag than the HTA68 but Bren tuned most of that away because he's a genius with the timing. I really have no complaints. I am going FAST at lower boosts before the Meth and upper boost really build up! 9psi or so I start spraying but all the fun stuff happens before then so I am thrilled with how easy this daily driver is behaving.

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@gordata - The Spearco was a direct fit for the car because we share the same engine/TMIC setup as the 08+ WRX - If you are going with an STi Turbo do you mean it will be rotated or direct fit? Pretty sure with patience and ingenuity you can make anything work!



Unfortunately no tmic will work with an sti turbo. You must run a fmic for that setup since the turbo faces a different way. There might be some kind of crazy way to do it but it isn't worth the hassle.

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^^^^ This. You would end up trying to use the Spearco TMIC for the STi but who knows on clearance issues all over the rest of the engine bay plus you would need the Sti intake and figure out where you would bolt the TMIC to. The TMIC I used is also much larger than those types with the Y pipe underneath which sort of really does block a chunk of the flow... IMHO
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Imagine how much MOAR POWAH you could be making if you'd done all this on a 5th Gen?!!! :lol:


Kidding, of course... you know I have the utmost respect/admiration for the time and effort you (and Alberto, and Bren, and others) have put into this car/build. Truly inspiring! Can't wait to see where it goes from here!

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not really sure you can apply "sleeper" to a LGT. its built to be quick so people already expect it to be quick. now maybe if you had a stealth FMIC and 2.5i hood maybe.

useless signature line where i cant mention my sponsors

"First Bagged BL5!"


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