I got an old school Hks single kit I wanted to put on. How hard is it to take off the stock twins? To go single I would imagine we have to disconnect a bunch of vacuum lines and solenoids etc?
do we have to modify the wiring harness at all?

i have a stock power fc map now with an almost stock car.

 

Umm. Maybe try searching, and do your homework before you start.

 

Depending on what’s in that “kit” and almost positive I’m missing things….

Fuel pump
Rewiring for that FP
FPR
Ignition upgrades
Probably new fuel lines
Appropriate fuel filter
oil feed/return lines
Appropriate larger injectors
fuel rail for those injectors
turbo manifold
down pipe
intake
intercooler plumbing
intercooler
Associated modifications for the IC and plumbing
Getting that PFC TUNED for the single

Taking off the stock twins with the engine in the car is probably the easy part, even with the inevitable broken studs.
The fact that you even asked suggests you probably shouldn’t do it.

 

Glad to see I'm not the only one with this mentality. There are some questions that that indicate the person asking shouldn't dive into the thing they're asking questions about.

I agree, it would be advised to abstain from any such activity.

 

Even if one had the technical knowledge required, I'm not sure why you would want to remove functional sequential twins for an "old school HKS single".

If you really need to mod one of the ~500 or so good condition stock body stock sequential twins USDM FDs remaining, you should do bolt-ons, IMO. You already have a PFC, that plus basic breather mods makes for a fun and responsive setup for the street. The beauty of the sequential twins is near full boost by 1,800 rpms plus the insane addicting powerband with the 4,500-rpm changeover and 8,000-rpm redline.

 

It is time consuming. Best recommendation that I can give is to download the FSM and go through that section for removal of the twins.
Then check the FAQ or search for threads on single turbo conversion. Should be plenty of reading material.

 

However much time and money you think this is going to take (even being generous), triple your current estimate.

 

True statement.

The more research you do before hand the easier it is during the process. Anyone can remove stuff with tools, the question is can you put it back together properly so everything works.

 

It's not that difficult and the more times you do it the less times it takes. I used the FSM and the search feature for guidance. This thread was helpful:

Twin Turbo Removal - RX7Club.com - Mazda RX7 Forum

I removed the turbos with the engine still in the car. Use PB blaster. A LOT OF PB BLASTER. Replace studs and nuts.

 

wow there’s only 500 or so good running usdm fd w stock twins in the states??

 

thank you for the link you posted! 🙏 will read up as much as I can. I do search but some of these search functions don’t pull up the best related results 🙂

one main reason to go single is there is a lil leak from the second turbo that I can’t get to….
also there are some exhaust leaks I think coming from the manifold area (not downpipe I checked)

and I thought simplifying the vacuum line set up and making things more simple and reliable. As well as upgrade.

but yes seems like there will be a ton more stuff needed even after just the single conversion

 

A small leak from the secondary turbo in my opinion, isn't worth the significant hours and cost involved in doing a single setup. The exhaust leaks, while problematic if coming from the manifold itself, is annoying but can be fixed by installing a manifold in better condition if you are able to find one.

Simplifying the vacuum line setup, etc, is also not a simple job to do by any means, and if you aren't fully versed into what you are about to undertake you may very well find yourself well into more of an intricate job than you anticipated.

You're also talking about an old HKS kit here, based on your description. You'd be giving away a significant portion of your powerband if I had to guess. Even with a new EFR turbo you are still compromising somewhat (though the degree of which and if its worth it is largely up to the person doing the conversion).

My advice, fix the twin setup and get them working properly, even then, make sure you know what you are doing and do as much research before hand as possible.

 

For cars in what I would consider good condition, there are probably less than 500 original LHD USDM examples remaining. I'm talking about cars with stock body, nice interior, and working sequential twins. The latest registration numbers showed ~4,500, and 9/10 of those are in rough condition with falling apart interiors and/or heavily modified.

Even if you never sell, swapping to a single devalues the car and makes it more likely to end up in a junkyard or parted out since it has less collector value. I'm not sure what you paid, but a stock 50k-mile red R1 is a $60-70k car on BaT all day long, and there aren't many left.

 

thank you for those numbers! Yes mine is a usdm 93 r1 with 56k miles. Stock interior and stock body. basic mods (Hks intakes, dp, exhaust, radiator, pineapple idler pulley, pfc and H&R short shifter)