MR2 Owners Club Forum banner
1 - 16 of 16 Posts

· Registered
Joined
·
6 Posts
Discussion Starter · #1 ·
Hey guys,

I’m not going to lie I’ve been getting lost in the sauce with the old threads and wanted to make a new one to be up to date. Wanting to run a bigger pulley of course to up the boost in my supercharged MR2. I’ve seen people mention the running lean issue and want to know solutions. I’ve seen talks of GruntBox, stand-alone ecu’s, what do you guys recommend?

thanks!
 

· Registered
1988 MR2 S/C
Joined
·
52 Posts
I've been searching for an answer as well and I keep getting mixed answers. Seems like the most popular is the grunt box, but I don't know if you can still buy them new. I've also seen people run no mods at all and claim their car runs fine.
 

· Registered
Joined
·
309 Posts
I'd say that it depends on how big a crank pulley you're running. For example with the smaller diameter HKS pulley or JDM supercharger pulley you can probably get by OK without it. When you step up to a Blitz or Cusco size I'd recommend a Grunt box minimum as you are going to lean out a lot, especially with a bigger exhaust, air filter etc. which improve flow.
The other issue with these mods is heatsoak especially with a stock intercooler in that hot engine bay so if you can improve intercooling it will help a lot. Run a fan under it at least to improve air flow through the core.
If you go big pulley without the extra fuel you'll find throttle response is flat (lean) under 3500rpm until the stock ECU compensates with added fuel above this level.
I'm running a 176mm pulley with 54mm throttle body at 13+ psi and went to a big TMIC with 10" fan to handle the extra heat- it made a huge difference.
 

· Registered
Joined
·
6 Posts
Discussion Starter · #4 ·
I'd say that it depends on how big a crank pulley you're running. For example with the smaller diameter HKS pulley or JDM supercharger pulley you can probably get by OK without it. When you step up to a Blitz or Cusco size I'd recommend a Grunt box minimum as you are going to lean out a lot, especially with a bigger exhaust, air filter etc. which improve flow.
The other issue with these mods is heatsoak especially with a stock intercooler in that hot engine bay so if you can improve intercooling it will help a lot. Run a fan under it at least to improve air flow through the core.
If you go big pulley without the extra fuel you'll find throttle response is flat (lean) under 3500rpm until the stock ECU compensates with added fuel above this level.
I'm running a 176mm pulley with 54mm throttle body at 13+ psi and went to a big TMIC with 10" fan to handle the extra heat- it made a huge difference.
Ok this is super helpful. Because this is what I’m trynna head towards w my rebuild. Just gotta keep researching! Thanks
 

· Registered
Joined
·
6 Posts
Discussion Starter · #5 ·
I've been searching for an answer as well and I keep getting mixed answers. Seems like the most popular is the grunt box, but I don't know if you can still buy them new. I've also seen people run no mods at all and claim their car runs fine.
I mean worse comes to worse I just run it as it is lol. Thanks for the input.
 

· Registered
1988 MR2 S/C
Joined
·
52 Posts
I mean worse comes to worse I just run it as it is lol. Thanks for the input.
I guess you could, but I'd suspect running lean can damage your engine.
I'd say that it depends on how big a crank pulley you're running. For example with the smaller diameter HKS pulley or JDM supercharger pulley you can probably get by OK without it. When you step up to a Blitz or Cusco size I'd recommend a Grunt box minimum as you are going to lean out a lot, especially with a bigger exhaust, air filter etc. which improve flow.
The other issue with these mods is heatsoak especially with a stock intercooler in that hot engine bay so if you can improve intercooling it will help a lot. Run a fan under it at least to improve air flow through the core.
If you go big pulley without the extra fuel you'll find throttle response is flat (lean) under 3500rpm until the stock ECU compensates with added fuel above this level.
I'm running a 176mm pulley with 54mm throttle body at 13+ psi and went to a big TMIC with 10" fan to handle the extra heat- it made a huge difference.
Yeah I have a Cusco pulley which I believe is 175mm. Definitely gonna need a grunt box.
 

· Registered
Joined
·
798 Posts
The gruntbox is a band-aid from the 90's. It was acceptable for the time but it is badly out of date. It tends to be a little too much for the lower mid RPMs and a little too little for the upper mid RPMs. But over-all better than nothing I guess. I do not know if you can still buy one but you could duplicate its function with an ebay microprocessor less than $20. (but you would have to learn soldering and programming - not that hard but most people don't want to do that)

Unfortunately I am not aware of any plug and play piggyback controllers that could do the job. Not that much money in building piggy back computers for 1980's cars. That leaves replacing your ECU. It could be done for as little as $250 with speeduino but you run into that 'learning' problem again. Or you can work your way up the ECU ladder - the more money you spend, the less you have to learn.
 

· Registered
1989 AW11SC
Joined
·
179 Posts
I'd say that it depends on how big a crank pulley you're running. For example with the smaller diameter HKS pulley or JDM supercharger pulley you can probably get by OK without it. When you step up to a Blitz or Cusco size I'd recommend a Grunt box minimum as you are going to lean out a lot, especially with a bigger exhaust, air filter etc. which improve flow.
The other issue with these mods is heatsoak especially with a stock intercooler in that hot engine bay so if you can improve intercooling it will help a lot. Run a fan under it at least to improve air flow through the core.
If you go big pulley without the extra fuel you'll find throttle response is flat (lean) under 3500rpm until the stock ECU compensates with added fuel above this level.
I'm running a 176mm pulley with 54mm throttle body at 13+ psi and went to a big TMIC with 10" fan to handle the extra heat- it made a huge difference.

I went with the HKS pulley ( +2 lbs. more boost ) when I swapped over from the stock OEM. To make the 4A-GZE properly perform, you have to let it breath. They're way too muzzled in stock trim. Improving air flow truly is the catalyst for improving overall performance.

Camera lens Font Gramophone record Camera accessory Cameras & optics


Azure Font Electric blue Gas Liquid


A proper cold air intake, a decent 4 into one exhaust header with a cat delete, and a quality free flow exhaust when installed all together will make a huge difference in performance without decreasing reliability.

Jaw Font Line Handwriting Illustration

I also went with mild cams (265) and had the head ported and polished.

One of the best performance upgrades for the SC is the intercooler. The stock OEM is puny and weak. Back in the day Spearco, HKS and Trust offered bolt-in IC's that are no longer available and have now become "unobtanium".

Very nice ones have been offered for sale here by a vendor. Here is a really nice IC upgrade that an MR2OC member has, "dan4agze" .



IMHO, it's pricey but well worth it, and will probably be the final performance upgrade I make on my SC later this year.

I have never had any issues with flat spots or running lean under 3500 rpm's. I find that my GZE has plenty of low end grunt when I punch my throttle and see that little green light..... 😎


Minty AW11SC
 

· Registered
Joined
·
309 Posts
I went with the HKS pulley ( +2 lbs. more boost ) when I swapped over from the stock OEM. To make the 4A-GZE properly perform, you have to let it breath. They're way too muzzled in stock trim. Improving air flow truly is the catalyst for improving overall performance.

View attachment 85248

View attachment 85249

A proper cold air intake, a decent 4 into one exhaust header with a cat delete, and a quality free flow exhaust when installed all together will make a huge difference in performance without decreasing reliability.

I also went with mild cams (265) and had the head ported and polished.

One of the best performance upgrades for the SC is the intercooler. The stock OEM is puny and weak. Very nice ones have been offered for sale here by a vendor. Here is a really nice IC upgrade that an MR2OC member has , "dan4agze" .



IMHO, it's pricey but well worth it, and will probably be the final performance upgrade I make on my SC later this year.

I have never had any issues with flat spots or running lean under 3500 rpm's. I find that my GZE has plenty of low end grunt when I punch my throttle and see that little green light..... 😎


Minty AW11SC
Nicely done with the mods.
Yes the restrictions on both the intake and exhaust sides make a big difference to the engines ability to breathe and rev more freely. I found the stock throttle body size hindered the supercharger's ability to inhale especially with the 176mm pulley.
A few ideas to share:
Although the N/A 4AGE 55mm throttle body bolts onto the 4AGZE, I tried it years ago with a remote mounted IACV and wasn't happy with the idle control it provided.
Instead a spare 4AGZE TB was bored out to 54+mm. with a larger throttle plate. (At Maxbore) who specializes in throttle bodies. Using the newly sized T/B as a template its increased diameter was marked on the top of a spare J pipe and a grinding bit removed material to match it. (out of the car)
Some time with a small sanding drum finished the job with a nice smooth taper extending down into the pipe.

This way idle control and all other connections remain stock along with all of the factory vacuum lines making an easy return to original if ever needed.

On the SC exhaust side a spare JDM supercharger outlet pipe was cut and a larger 2.5" diameter exit pipe was welded on. The new pipe now exits horizontally directly into the new TMIC. Cooling is night & day difference. A 2.5" exhaust lets it all exit.


How did the new cams work?
 

Attachments

· Registered
1989 AW11SC
Joined
·
179 Posts
The 265 cams work great and do not create a shaky lumpy engine idle. They give a more aggressive surge of power under hard acceleration.

That is quite the amazing intercooler mod you have there. Wow.....it's huge!!!! Am I correct in assuming you installed it in the back trunk because it wouldn't fit in the engine bay ?

I recognize that green HKS filter on your air intake. I have a brand spanking new one identical to that one that I've never used.


Minty AW11SC
 

· Registered
Joined
·
309 Posts
I went with the trunk mount to remove it from the hot engine bay to assist in cooling. The Yonaka A2A bar & plate core (not counting end tanks) measures 18 x 9 x 2.5" almost doubling the I/C volume with much less restriction.
After a good run the IC inlet pipe is very hot but the exit side is just warm. Vents out the trunk with a 10" fan and a heat shield to block radiant heat from the exhaust.

Your cams sound like they're working nicely. What did you end up with for final cam settings and any dyno by chance?
 

· Registered
1989 AW11SC
Joined
·
179 Posts
Killer intercooler T.C.......amazing...... (y)

I had all of my engine work done at a Toyota dealership by a Red Seal mechanic a very long time ago. HKS made 265 plug and play cams back then but they were really expensive and I was already breaking the bank to begin with. I saved some money by re-grinding the stock OEM cams to 265's at a local specialty shop and they've never given me any grief, only horsepower...... :cool:

All this sort of tinkering activity was very much frowned upon back then by Toyota. I had to be careful because my SC at the time still had factory warranty and I was warned that installing non-factory racing parts would void my warranty........ :rolleyes:

There reached a point in time when I stopped spending money on upgrades on my SC. Life went on and I had bought a house which then became the primary focus of my money spending. The SC found itself safely parked in the garage while quietly and stubbornly appreciating.....:)..... in value.

Here are the spec's from IC that "dan4agze" has installed on his car from the actual vendor/fabricator. He sent them to me last year when I was in contact with him. I want to get one for my SC.

Rectangle Slope Parallel Font Pattern




Back then, I don't recall any of the local speed shops that even had a dyno and even if somebody did, I didn't know of it. Unlike today where they've become ubiquitous. No my SC has never seen a dyno. A conservative estimate would be an honest 200 BHP. In order to break in to 240 BHP range you need to have more aggressive cams, change valves, bearings and pistons.

You then loose the drivability of the motor and it gets really pricey. IMHO, too much emphasis is placed on BHP. You can get massive performance gains from proper suspension tuning/set up and reducing weight. An AW11SC is never going to be a supercar by today's Herculean standards but will always remain a Ninja that is a giant killer, nonetheless.


Minty AW11SC
 

· Registered
Joined
·
309 Posts
Minty Aw11SC I hear you, it's not all about numbers. I'm an old guy now but enjoyed tinkering with the cars way back and learning about them. Love the torque from these little gems which as you know makes them so much fun.
Good chatting with you and keep enjoying the car on nice summer days!
 

· Registered
Joined
·
685 Posts
Hey guys,

I’m not going to lie I’ve been getting lost in the sauce with the old threads and wanted to make a new one to be up to date. Wanting to run a bigger pulley of course to up the boost in my supercharged MR2. I’ve seen people mention the running lean issue and want to know solutions. I’ve seen talks of GruntBox, stand-alone ecu’s, what do you guys recommend?

thanks!
I can ask Mike if he has anymore, lol. He made them. He sold hes sc mr2 to complete his v8 miata.
 
1 - 16 of 16 Posts
Top