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Discussion Starter · #1 ·
Hello everyone, this is my first forum post as I am very new to the car modding scene.

I am looking for help with building my 2003 Lexus is300. I want about 250-300hp with the possibility of increasing it in the future. Im curious to know what things I need to do to get to my horse power goal. My budget is around 2-3000 maybe more. Should I go for an NA-T build? Any and all information is much appropriated!!
 

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Hello everyone, this is my first forum post as I am very new to the car modding scene.

I am looking for help with building my 2003 Lexus is300. I want about 250-300hp with the possibility of increasing it in the future. Im curious to know what things I need to do to get to my horse power goal. My budget is around 2-3000 maybe more. Should I go for an NA-T build? Any and all information is much appropriated!!
Unfortunately, 2JZ-GE IS300's are all-or-nothing. Basic intake/header/exhaust mods wake up some HP but won't make your HP goal by a long shot.

After that, the stock ECU is hot garbage when it comes to dealing with modifications, so there's no 'easy' or 'just a little more' or 'staged' upgrades.
Stage 1 is a complete turbo kit and a standalone ECU on a split harness to share the stock ECU with the rest of the car, after which it will never again pass an OBD-II scan or engine bay check for an emissions inspection or compliance inspection, and you'll be chasing CEL's and weirdness for a little time or a long time depending on what all you do.

If you roughly double your budget to $5-7k or so, you can piece together a decent quality turbo kit and a good engine management/ECU solution, along with the injectors and fuel pump upgrades required. Supporting mods like a clutch, catback exhaust, built trans, trans coolers, LSD differential, etc are all on top of this $5-6k requirement.

That'll get you to a safe 300-350whp on lower boost levels very easily. From there, getting into the engine is mandatory to install connecting rods that won't fail at 400hp, and also reduce static compression with a stock TT Supra headgasket to avoid detonation on pump gas with moderate boost levels. This inevitably turns into a 'while you're in there' snowball where aftermarket forged rods and pistons and cams and a nice front facing intake manifold and all kinds of shit shows up, and the engine's ready for 800-1000whp, or more if you do billet mains. This can be done for around $3-4k if you do it all just right and your block needs little if any machine work, but it snowballs into a $5-20k process very quickly with things like stroker cranks and billet mains and cams/headwork/billet intake manifold, etc

Then your stock transmission explodes suddenly and violently (W58 or A650E auto) and then you're onto a powertrain solution that'll play nice with the IS300 gearing, which means a $3-5k R154 5-spd setup w/decent twin disc clutch on the cheap(er) end, or a Grannas Magnum T56 conversion with a nice McLeod or Tilton clutch for 7-12k depending on options. Or a PHR 6R80 Ford auto trans swap which runs 5-8k depending on where you source the trans and whether or not you build it, and what kind of shifter setup and trans control you go with - some more expensive standalone ECU's can run this trans, otherwise you're in for a $1000+ trans controller. Gearing gets weird with available IS300 rear differentials as well, so things like a Getrag V160 or Nissan CD009 are poor candidates because you can't easily get a rear diff ratio that matches the trans gearing very well.... and the 6R80 is as well now that I think about it.

And then you realize that you're about $25-40k into this build (not including labor if you haven't done all the wrench-turning yourself) and you haven't touched the wheels, tires, or brakes to match all the horsepower.

Truly, if you really want a turbocharged IS300, I'd strongly recommend saving your money and buying one that's already built. You'll save at least $10-15k vs building the same car yourself.

Just in case you're wondering, 'All motor' isn't viable unless you'd like to spend the same $25k to make your 300hp goal. Another Supraforums member built a non-turbo 2JZ-GE Supra, and while the result is glorious it took a LOT of work to make ~270whp. ITB's, $$$$ Custom header, $$$$ Custom headwork and big cams, etc.

Sorry to be the bearer of bad news, I love those IS300's myself, but they're not an economical car to build at all.
 

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Discussion Starter · #5 ·
Unfortunately, 2JZ-GE IS300's are all-or-nothing. Basic intake/header/exhaust mods wake up some HP but won't make your HP goal by a long shot.

After that, the stock ECU is hot garbage when it comes to dealing with modifications, so there's no 'easy' or 'just a little more' or 'staged' upgrades.
Stage 1 is a complete turbo kit and a standalone ECU on a split harness to share the stock ECU with the rest of the car, after which it will never again pass an OBD-II scan or engine bay check for an emissions inspection or compliance inspection, and you'll be chasing CEL's and weirdness for a little time or a long time depending on what all you do.

If you roughly double your budget to $5-7k or so, you can piece together a decent quality turbo kit and a good engine management/ECU solution, along with the injectors and fuel pump upgrades required. Supporting mods like a clutch, catback exhaust, built trans, trans coolers, LSD differential, etc are all on top of this $5-6k requirement.

That'll get you to a safe 300-350whp on lower boost levels very easily. From there, getting into the engine is mandatory to install connecting rods that won't fail at 400hp, and also reduce static compression with a stock TT Supra headgasket to avoid detonation on pump gas with moderate boost levels. This inevitably turns into a 'while you're in there' snowball where aftermarket forged rods and pistons and cams and a nice front facing intake manifold and all kinds of shit shows up, and the engine's ready for 800-1000whp, or more if you do billet mains. This can be done for around $3-4k if you do it all just right and your block needs little if any machine work, but it snowballs into a $5-20k process very quickly with things like stroker cranks and billet mains and cams/headwork/billet intake manifold, etc

Then your stock transmission explodes suddenly and violently (W58 or A650E auto) and then you're onto a powertrain solution that'll play nice with the IS300 gearing, which means a $3-5k R154 5-spd setup w/decent twin disc clutch on the cheap(er) end, or a Grannas Magnum T56 conversion with a nice McLeod or Tilton clutch for 7-12k depending on options. Or a PHR 6R80 Ford auto trans swap which runs 5-8k depending on where you source the trans and whether or not you build it, and what kind of shifter setup and trans control you go with - some more expensive standalone ECU's can run this trans, otherwise you're in for a $1000+ trans controller. Gearing gets weird with available IS300 rear differentials as well, so things like a Getrag V160 or Nissan CD009 are poor candidates because you can't easily get a rear diff ratio that matches the trans gearing very well.... and the 6R80 is as well now that I think about it.

And then you realize that you're about $25-40k into this build (not including labor if you haven't done all the wrench-turning yourself) and you haven't touched the wheels, tires, or brakes to match all the horsepower.

Truly, if you really want a turbocharged IS300, I'd strongly recommend saving your money and buying one that's already built. You'll save at least $10-15k vs building the same car yourself.

Just in case you're wondering, 'All motor' isn't viable unless you'd like to spend the same $25k to make your 300hp goal. Another Supraforums member built a non-turbo 2JZ-GE Supra, and while the result is glorious it took a LOT of work to make ~270whp. ITB's, $$$$ Custom header, $$$$ Custom headwork and big cams, etc.

Sorry to be the bearer of bad news, I love those IS300's myself, but they're not an economical car to build at all.
Wow this is a lot of stuff to take in lol. But thank you. Looks like I have some decision making to do.
 

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Discussion Starter · #6 ·
Wow this is a lot of stuff to take in lol. But thank you. Looks like I have some decision making to do.
Unfortunately, 2JZ-GE IS300's are all-or-nothing. Basic intake/header/exhaust mods wake up some HP but won't make your HP goal by a long shot.

After that, the stock ECU is hot garbage when it comes to dealing with modifications, so there's no 'easy' or 'just a little more' or 'staged' upgrades.
Stage 1 is a complete turbo kit and a standalone ECU on a split harness to share the stock ECU with the rest of the car, after which it will never again pass an OBD-II scan or engine bay check for an emissions inspection or compliance inspection, and you'll be chasing CEL's and weirdness for a little time or a long time depending on what all you do.

If you roughly double your budget to $5-7k or so, you can piece together a decent quality turbo kit and a good engine management/ECU solution, along with the injectors and fuel pump upgrades required. Supporting mods like a clutch, catback exhaust, built trans, trans coolers, LSD differential, etc are all on top of this $5-6k requirement.

That'll get you to a safe 300-350whp on lower boost levels very easily. From there, getting into the engine is mandatory to install connecting rods that won't fail at 400hp, and also reduce static compression with a stock TT Supra headgasket to avoid detonation on pump gas with moderate boost levels. This inevitably turns into a 'while you're in there' snowball where aftermarket forged rods and pistons and cams and a nice front facing intake manifold and all kinds of shit shows up, and the engine's ready for 800-1000whp, or more if you do billet mains. This can be done for around $3-4k if you do it all just right and your block needs little if any machine work, but it snowballs into a $5-20k process very quickly with things like stroker cranks and billet mains and cams/headwork/billet intake manifold, etc

Then your stock transmission explodes suddenly and violently (W58 or A650E auto) and then you're onto a powertrain solution that'll play nice with the IS300 gearing, which means a $3-5k R154 5-spd setup w/decent twin disc clutch on the cheap(er) end, or a Grannas Magnum T56 conversion with a nice McLeod or Tilton clutch for 7-12k depending on options. Or a PHR 6R80 Ford auto trans swap which runs 5-8k depending on where you source the trans and whether or not you build it, and what kind of shifter setup and trans control you go with - some more expensive standalone ECU's can run this trans, otherwise you're in for a $1000+ trans controller. Gearing gets weird with available IS300 rear differentials as well, so things like a Getrag V160 or Nissan CD009 are poor candidates because you can't easily get a rear diff ratio that matches the trans gearing very well.... and the 6R80 is as well now that I think about it.

And then you realize that you're about $25-40k into this build (not including labor if you haven't done all the wrench-turning yourself) and you haven't touched the wheels, tires, or brakes to match all the horsepower.

Truly, if you really want a turbocharged IS300, I'd strongly recommend saving your money and buying one that's already built. You'll save at least $10-15k vs building the same car yourself.

Just in case you're wondering, 'All motor' isn't viable unless you'd like to spend the same $25k to make your 300hp goal. Another Supraforums member built a non-turbo 2JZ-GE Supra, and while the result is glorious it took a LOT of work to make ~270whp. ITB's, $$$$ Custom header, $$$$ Custom headwork and big cams, etc.

Sorry to be the bearer of bad news, I love those IS300's myself, but they're not an economical car to build at all.
You are a legend for typing all this out for me. If you could put the mods I need to reach 300-400hp safely and reliably, I will love you forever.

Also what would be my best option to keep the car passing emissions so it can be street legal?
 

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You are a legend for typing all this out for me. If you could put the mods I need to reach 300-400hp safely and reliably, I will love you forever.

Also what would be my best option to keep the car passing emissions so it can be street legal?

You're welcome! Glad it was helpful. 🍺
The first two paragraphs cover it, really. You'll need a decent quality turbo kit, ideally with ~61mm or smaller turbo, along with a matching intercooler and exhaust setup.
A drop in fuel pump like a Walbro and a set of ~550-750cc injectors that fit the stock fuel rail, and a quality standalone ECU that is available with a PnP harness for an IS300 that retains the stock ECU to run all the Canbus stuff the IS300 needs like gauges. You'll also need the associated sensors, wideband O2, and a professional tune.

~350whp is about the safe limit for the stock VVTi 2JZ-GE block and rods, as well as the safe-ish limit for the stock auto trans or W58. Spend some money on a big trans cooler if you've got an automatic and get an upgraded clutch if you're on a W58. Enjoy the HP, but don't beat on it like a teenager with a new Mustang GT or you will break something.

Passing emissions will depend on where you are. Some states/cities let almost anything on the pavement, others freak out about a cold air intake. But if a visual inspection of emissions equipment or an OBD-II ECU scan are involved in your locale, a turbo kit will never pass.
 

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Discussion Starter · #8 ·
You're welcome! Glad it was helpful. 🍺
The first two paragraphs cover it, really. You'll need a decent quality turbo kit, ideally with ~61mm or smaller turbo, along with a matching intercooler and exhaust setup.
A drop in fuel pump like a Walbro and a set of ~550-750cc injectors that fit the stock fuel rail, and a quality standalone ECU that is available with a PnP harness for an IS300 that retains the stock ECU to run all the Canbus stuff the IS300 needs like gauges. You'll also need the associated sensors, wideband O2, and a professional tune.

~350whp is about the safe limit for the stock VVTi 2JZ-GE block and rods, as well as the safe-ish limit for the stock auto trans or W58. Spend some money on a big trans cooler if you've got an automatic and get an upgraded clutch if you're on a W58. Enjoy the HP, but don't beat on it like a teenager with a new Mustang GT or you will break something.

Passing emissions will depend on where you are. Some states/cities let almost anything on the pavement, others freak out about a cold air intake. But if a visual inspection of emissions equipment or an OBD-II ECU scan are involved in your locale, a turbo kit will never pass.
Well I won’t have to worry about passing emissions with a turbo until I have the money to buy one. I live in Missouri but I've never registered a car before so I’ll hopefully there’s no strict rules. It’s being inspected by a shop that specializes in JDM/imports so I’m hoping they’re a bit less hard on testing for emissions. Again, thanks for the info you are a blessing.
 
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