When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
At ~100K, I rebuilt my engine core (inner coolant seal failure) with all new OEM parts and kept it stock.
Recently, I was lucky enough to find a new set of the Hitachi HT12-3KAI twins.
My understanding was that these should be plug n play, so my intention was basically an “oem stock upgrade,” but I’m not sure if/what other changes really need to be made.
Turbo seller recommended that I change downpipe, remove cat, and computer/tune. But I’m kind of worried about going down the rabbit hole of upgrades.
What can I do to best utilize the turbos without making major changes (if any)?
What can I do to best utilize the turbos without making major changes (if any)?
sell them
theres no point in using upgraded turbos just to NOT use them for what they are. what would be the point? the suggestions made were to properly utilize them, which you don't seem to want to do. you can simply install them and make no mods at all, it will work just the same. it will just be a waste if you have no intention of modding the car. you can use an A1 or C1 set in that case and let someone else utilize them.
theres no point in using upgraded turbos just to NOT use them for what they are. what would be the point? the suggestions made were to properly utilize them, which you don't seem to want to do. you can simply install them and make no mods at all, it will work just the same. it will just be a waste if you have no intention of modding the car. you can use an A1 or C1 set in that case and let someone else utilize them.
Based on this type of toxic attitude, I’d rather smash them with a sledge hammer than “let someone else utilize them.” Try to come here for legit advice and post in the New Member section only to be chastised for asking questions.
your question was answered. you're asking what you can do to best utilize them (if any) without making major changes. the person you bought the twins from advised you appropriately and you are concerned with following that advice. there's nowhere to go after that besides not using them or using them and not following the advice given to "best utilize" them. mods require mods to make sense. you bought the twins without the willingness to make further changes to the car to properly make use of them. there is no best utilization outcome in this circumstance without making other changes. you have half of the equation and are reluctant or unwilling to execute the other half. you want to be in possession of the cake and also consume it
what kind of answer or advice are you specifically looking for?
At ~100K, I rebuilt my engine core (inner coolant seal failure) with all new OEM parts and kept it stock.
Recently, I was lucky enough to find a new set of the Hitachi HT12-3KAI twins.
My understanding was that these should be plug n play, so my intention was basically an “oem stock upgrade,” but I’m not sure if/what other changes really need to be made.
Turbo seller recommended that I change downpipe, remove cat, and computer/tune. But I’m kind of worried about going down the rabbit hole of upgrades.
What can I do to best utilize the turbos without making major changes (if any)?
Sounds like no other changes have to be made to stock upgrade them. Install them and you have a stock upgrade.
For my rebuild, my intention was to keep it stock/OEM with reliability upgrades (and a catback). Since then, I’ve been looking for new turbos (stock, 99jspec) for years, and as you know they are pretty hard to find now. I’ve even looked for them while in Japan this year.. Finally, I lucked out and bought these 3KAI versions at market price from someone who lived 10 minutes away. Who here wouldn’t have jumped on these?
I’m open to the changes the seller recommended, that’s why I made this post in the first place… but I’m still wondering what it would be like on an otherwise stock setup. Is there risk of overheating the turbo due to poor air flow? There should be some hp gains right, wasteful or not?
I’m concerned about changes that negatively affect the cars value and drivability/reliability.
What I really wanted to avoid are major changes like upgraded fuel rails, porting. Etc.
I don’t need the fastest RX7, but if I can get a modest performance increase while essentially still OEM is that so crazy? If it makes sense for the exhaust/computer changes then so be it… at least they would be reversible right?
Retaining value should never be a consideration. There are very few FDs out there that fall into a category where that actually matters and they are not driven. Attempting to own the car while considering what the next person that owns it will think does no one any good and takes away from your experience.
Reliability and drivability do not come into play at this level. Just do what makes you happy. So long as the stock cat is in place, do what you want and enjoy the car. Sounds like the simplest way forward for you is to do nothing extra and install the turbos.
You're overthinking this. They're going to perform how they perform. They're not going to destroy themselves or anything else because everything around them is stock.
So, slightly more lag on primary turbo and then slightly more power at same boost as stock with slightly leaner Air Fuel Ratios than stock.
Stock ECU runs things pretty rich, so you probably wont blow up from the leaner AFRs- but you wont have the same margin of safety as stock.
To put this in perspective, in 1999 for the high power 280hp spec Mazda made the turbos slightly smaller than the earlier 255hp stock turbos, but increased boost from 10psi to 12psi. This privided less lag AND more power.
99 spec turbos would be what you want for an actual upgrade while running stock power.
All variants of the twin turbos can make about 400rwp, the stock fuel system can only do ~340rwhp, the stock ECU can only do ~300rwhp (boost cut ~10psi).
Your car with catback is probably ~250-260rwhp if everything is running right.
This thread with dynos of progressive mods will give you a good idea of potential.
I just wish they had plotted the AFRs getting leaner and leaner on the stock ECU while adding mods.
Ok, here’s a wrinkle. Someone offered to trade me straight up for new 99 J-spec twins.
First of all, is it fair trade?
If I can run the 3KAI’s safely with the stock ecu, get a performance increase, and still have the option to mod in the future then this seems the best option to me.
On the other hand if the 3KAI’s risk to run lean is too high, and I never modify anything then the 99 J-specs are probably a better call.
Is your car 100% stock? You mention your intention is stock with reliability mods and catback.
For me, reliability mods are Downpipe and Intercooler. Both are reversible, but move a significant amount of heat away.
The twins you have are a nice upgrade over stock. Not only is the wastegate area larger(for better boost control), but from what I remember they flow about 12% more air over stock. To Blue TII point, there is a decent rich margin of error with stock ECU, but if you are investing in a new motor and those turbos, I personally would not want to take a risk like that.
I would at minimum do a downpipe, stock mount intercooler and a Plug and Play harness with a power FC. Can have someone local to you tune the car or simply use FC tweak and tune it yourself.
All can be completely reversible, but I would hate for you to rely on the stock ECU and get a nice 60* day and pop your new motor because these turbos flow more than stock.
Is your car 100% stock? You mention your intention is stock with reliability mods and catback.
For me, reliability mods are Downpipe and Intercooler. Both are reversible, but move a significant amount of heat away.
The twins you have are a nice upgrade over stock. Not only is the wastegate area larger(for better boost control), but from what I remember they flow about 12% more air over stock. To Blue TII point, there is a decent rich margin of error with stock ECU, but if you are investing in a new motor and those turbos, I personally would not want to take a risk like that.
I would at minimum do a downpipe, stock mount intercooler and a Plug and Play harness with a power FC. Can have someone local to you tune the car or simply use FC tweak and tune it yourself.
All can be completely reversible, but I would hate for you to rely on the stock ECU and get a nice 60* day and pop your new motor because these turbos flow more than stock.
Eric
Solid advice, this seems to be the consensus.
My choices:
1) Install 3KAI’s and modify car.
2) Install 99 J-spec and keep everything else stock.
So, slightly more lag on primary turbo and then slightly more power at same boost as stock with slightly leaner Air Fuel Ratios than stock.
Stock ECU runs things pretty rich, so you probably wont blow up from the leaner AFRs- but you wont have the same margin of safety as stock.
To put this in perspective, in 1999 for the high power 280hp spec Mazda made the turbos slightly smaller than the earlier 255hp stock turbos, but increased boost from 10psi to 12psi. This privided less lag AND more power.
99 spec turbos would be what you want for an actual upgrade while running stock power.
All variants of the twin turbos can make about 400rwp, the stock fuel system can only do ~340rwhp, the stock ECU can only do ~300rwhp (boost cut ~10psi).
Your car with catback is probably ~250-260rwhp if everything is running right.
This thread with dynos of progressive mods will give you a good idea of potential.
I just wish they had plotted the AFRs getting leaner and leaner on the stock ECU while adding mods.
And thanks for taking the time to post that informative thread.
Do you have any recollection of how much leaner the AFRs were in the stock ECU with all the mods vs stock (just downpipe)?
I have tuned many cars since that thread. But I found this on post #36, so this car had an upgraded pump since the very beginning.
Originally Posted by Banzai-Racing
The AFR's with the Intake, DP & Catback with the stock ECU remained safe in the low 11's. I should mention that we had installed a Walbro 255 back when we were doing the initial repairs and DP install earlier this year. I can't say that the stock pump would yield the same results.
