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What IRTB kit would you use on a 1.8L NA?

  • R.S. Aizawa

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I am going to install an IRTB kit to my upcoming Miata project. I will be using a 1994-1997 1.8L Miata engine. Before adding the IRTB setup, I will be shipping the engine to Flyin' Miata for a full overhaul. They will be completly rebuilding the bottom and top end. Stroker kit, 11:1 compression, you name it. This engine will be completly made over, and to top it off I will be using the Flyin' Miata Miata-Link ECU with Knock Sensor.

I have heard much discussion on this forum about the FUJI Racing IRTB kit, but not much else. I know TheBluePotato uses an RS Aizawa IRTB kit. What is everyone using, and why? I want a kit that will offer the most response and performance, while providing as close to trouble-free, dependible functionality. What do you think to be the ultimate option for and IRTB kit?
 

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You're missing a few choices there sport.

http://forum.miata.net/vb/showthread.php?t=170752

There is no right answer here. Each setup has pros and cons. I would focus my energy on finding an appropriate ECU and a tuner who will support what you've got installed. Getting fuel and spark dialed in is going to make the biggest difference in how tractable your setup is. So long as the hardware is reasonably decent it's hard to go wrong. Choosing the right kit for your particular needs will have an effect on the maximum power you'll attain but you can always play with the power delivery later. However you won't be willing to put up with your ITB kit for long if it stalls at every stop light and you only get 10 mpg and fail emissions (which I suspect will be your biggest hurdle living in California).
 

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The reason so many people go with Fuji Racing is because Jimmy is located in the USA, the price is right, and he's willing to provide support for his product. The only way you're going to get some RS Aizawa throttles on your car is if you fly Aizawa-san over to the USA to personally install them at great expense to you.
 

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However you won't be willing to put up with your ITB kit for long if... you only get 10 mpg and fail emissions (which I suspect will be your biggest hurdle living in California).
Hah, I should probably fix that with my setup :lol: Emissions in February HOOOOOO! :|
 
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Well, if the Fuji setup is so readilly servicable, that sounds like incentive enough. I would greatly value the fact that I can more easilly obtain service and support for the setup. What is everyone's experiences with the Fuji setup?
 

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The reason so many people go with Fuji Racing is because Jimmy is located in the USA, the price is right, and he's willing to provide support for his product. The only way you're going to get some RS Aizawa throttles on your car is if you fly Aizawa-san over to the USA to personally install them at great expense to you.
twm is also located in the US ( socal ) and everything, minus casting, is built in shop (including carbon fiber). I think you should be worrying about ems more than who's itb's you should get. the link ecu is nice, but the aem ems is nicer. plus more dyno tuners are familiar with the aem unit.

for what it's worth twm products are used on some of the top competing race cars in the industry. =D>
 
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I understand there is more to the kits than simply performance. There is reliability and convenience to consider as well. From what you are saying Fuji Racing and TWM have US representation, which is invaluable relative to service and support. I am leaning now towards the Fuji Racing kit, just because there are so many Miata owners, especially on this forum, that use the kit. If so many Miata owners use the kit, I would imagine there is a legitimate reason. As far as the ECU is concerned, I am pretty sold on the Miata-Link system. Not to discredit the other units available, but the Miata-Link is a very basic, simple to use system. I don't need an elaborate aray of options and features; I just need an ECU that runs stable and is easy to interact with when necessary. Also, Flyin' Miata is quite a reputiable company in terms of Miata tuning. As far as the kits are concerned, does anyone find one to be more dependible or stable than another, or is it really a toss-up?
 
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Another concern, which I didn't think of until visiting the TWM website, is emissions. With any of these kits, what struggles will I go through getting my car smogged? I don't feel like toying around with my setup each time I need to visit a smog station. I want a kit that will run strong, efficient, dependable and legal. Does this change things? Is one kit easier to pass CA smog than another?
 

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Somehow I thin your opinion is biased :lol:

I do love their setups though. Nice and clean. :)
just a little biased :wink: , but for what it's worth, I think it's great what jimmy @ fuji has done for itb's in the miata community.
 

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Another concern, which I didn't think of until visiting the TWM website, is emissions. With any of these kits, what struggles will I go through getting my car smogged? I don't feel like toying around with my setup each time I need to visit a smog station. I want a kit that will run strong, efficient, dependable and legal. Does this change things? Is one kit easier to pass CA smog than another?
You're 19 and you're having your motor worked on by FM? I must've been saving up since 2. :p

Don't even THINK about passing smog. You mind as well register the car out-of-state. All it takes is two seconds for the ref to say, "Ummmm...no". It's not so much the emmisions that'll fail, it's the visual inspection.

Luckily, I smogged my car this year, so I have 2 years to play with the IRTBs before I have to smog it again. When that happens, I plan on taking the motor out and getting it rebuilt. (150k+ miles).
 

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As much as I would love to plug my Aizawa ITB - I would have to default to Fuji or Maruha as their kits have parts that are easy to obtain as well as local support. Not to say that the Aizawa is the sweetest kit in the world \:D/ The Aizawa kit is 1) custom made just for the miata/engine spec 2) looks like a piece of artwork and 3) very expensive due to the CNC work, etc. and 4) very much adjustable in the details (adjustable A/C control, throttle linkage design, etc). It is a great kit and I love it and if money is no option, then this would be my recommendation.

With that being said, an ITB system really comes down to a couple important factors that one really needs to consider....

1) The additional ECU is the heart of any ITB setup - without the proper ECU, your ITBs can be the best selling or the coolest looking units on the planet, but it will do you no good if your system is not properly running correctly - like solid idle, fuel mixture, base maps, temp or altitude compensation.

2) Emissions - Any ITB system (I believe) can be set up for a smog (re sniff) test - but not the visual (if very strict) - unless you can temporarily modify your ITB's to pass the visual. In GA I can pass emissions all day long due to the HKS F-con programming - as it allows me to set up maps that will adjust fuel mixture levels so that I can meet the minimum levels on a pre-OBD vehicle. Because the HKS is so tunable, I am running now at safe CO/HC levels on a daily basis - if I go to the track, I simply dial in a high performance map - for instance, in GA you will have for all pre-ODB vehicles:

All 1995 and older model year vehicles will receive a four-part inspection:

a) A visual inspection of the catalytic converter to check for tampering or removal.

b) ASM2 or Accelerated Simulation Mode Test - A dual-mode test including a 25/25 test = 25 pounds of load at 25 MPH and a 50/15 test = 50 pounds of load at 15 MPH.

c) A tailpipe exhaust emission test.

d) A fuel cap inspection to check for adequate seal.

e) An inspector can reject a vehicle for testing if it is considered unsafe to test. If the test has already begun when the safety problem is detected, the inspector may charge the full price of the test.

3) ECU and tuning - you obviously need an ECU that will not only give you lots of room to program but an ECU that will be programmable by you or a tuner. Tuning is so key - I need to say that again - TUNING is so key in setting up an ITB system. I think again her Fuji wins (by a hair) as Jimmy has set up different ECU options that can be tuned by the user or a professional (recommended). Sure, my Aizawa kit can use a Freedom ECU, TEC II or III, etc....but piggy backs like the Link, AEM, etc is very limited on what it can do with a ITB system, be emissions friendly, run on proper octane, A/C control - all the things you need for solid a reliable daily driving conditions. Note that the HKS F-Con is a licensed ECU and software and can only be programmed by authorized HKS tuners (which is growing each year across the USA).

So which is the best? They are all great - you just need to find one that is proven and usable for your OWN situation. There are many people on CR.net that is ITB enfused now....and its great that you can get excellent feedback and a base of people who you can ask real questions and get real answers.
 

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The reason so many people go with Fuji Racing is because Jimmy is located in the USA, the price is right, and he's willing to provide support for his product. The only way you're going to get some RS Aizawa throttles on your car is if you fly Aizawa-san over to the USA to personally install them at great expense to you.
Just a clarification - any ITB system can be worked on or installed by anyone who has the basic automotive skills - in fact installing a well made ITB system is very easy to install (Foo, you can chime in here) - installing my Aizawa system was about two hour total for the system (not ECU and sensors). Because I like the bling, I added aero-quip connectors as well as took my time in hiding as much wiring as I could. So you do not need Aizawa here to install their system - much like needing Jenvy here to install their UK system.



I think what the point here is that the ECU I use is by HKS and can only be tuned by an authorized HKS dealer (i.e. Aizawa did my tuning in conjunction with Dyno Labs of Marietta, GA). And the Aizawa system does come with instructions on how to install (yes, it is in Japanese) and I have the Maruha instructions as well - both are very easy to understand with pics, etc. Concerning the HKS ECU - If you need to see how this ECU is becoming more poular in the US, one only need to check out supraforums.com. There are a few guys there that tune the HKS units and do so at many Supra events - who are licensed to do so.

Keep in mind when my ITBs were initially installed, it started up and drove it around the streest with no issues and no programming...alive and breathing but needs tuning for protecting the engine and maximum POWAH!
 

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Thanks for the clarification Peter. I was under the impression that RS Aizawa would only sell their ITB kit if they installed it themselves to protect their reputation from ham fisted mechanics screwing up the job and blaming them for it as the tuning is so vital for good results. I now stand corrected. Is your F-con in Japanese or English? A friend I know has an R34 Skyline and his F-con is all in Kanji. The 1st HKS dealer he took it to was useless because not only did they not understand Japanese they didn't have the proper hardware key to interface with the ECU. Fortunately someone recommended SP Engineering who is capable of tuning his particular version.
 

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Save the shipping to an fro FM. They farm-out (as opposed to sub-contract which implies quality) their machine work which isn't up to snuff.
Chris
 

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Do you have any non-anecdotal evidence to suggest FM engine machine or assembly quality is not credible? Specific claims or allegations supported by fact would be helpful. Thank you.
 

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I think as Peter says it really comes down to your budget and what application you will be puting your car to ...

the R S Aizawa kit is beautifully made but at face value can cost up to twice the price of say the Fuji kit plus ECU

the fuji 1600 kit offers further benefits for those on a tight budget by including the subcon piggyback ECU that although far from perfect at least allows the IRTB setup to be run while you save up for a more versatile independant ECU.

a slightli cheaper way to get into the more exotic R S Aizawa hardware is to source a set of Toyota AE101 IRTB's and use the R S Aizawa manifold and fuel rail setup, alternatively there are several other manufacturers that produce manifold/fuel rail kits to convert AE101's to NA6 or NA8 ...

it must also be considered that on their own, without any internal engine modifications IRTB's are not going to produce much in the way of additional horsepower ... they will however provide you with greatly increased throttle response and an amazing sound when set up
 

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When I get the specs on the bottom end they built I'll post them.

It was an over-overbore~ the pistons could be moved around the cylinders wth one finger.

This information is from a reputable engine builder in Atl., highly recommended by some top shelf Miata guys, that is re building a motor using the bits purchased from FM and a boneyard block.

It's all about the tolerences of the bore.

I *was* going to ship the motor to FM but was advised to use a Spec Miata shop instead and they found the problem.

FM built a great reputation on quality and customer service- it is a shame to see someone else threaten it.

Honestly I am not sure of what is an acceptable tolerance for the bore of a motor. I will save the old block, have everything measured (independently) and let you know.

Chris
 

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I assume from your original question that budget is not really an issue with your engine being shippe off to FM for internal work ... if this is the case I would advise having your head polished and ported to take advantage of the increased flow rate provided by the IRTB's, more aggressive cams and adjustable cam wheels withh also allow for fine tuning with your ECU to enable you to extract the optimum power from your setup
 
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