frankenstein motors

With the RX8 we can source the car for you. The cost for those cars are inexpensive (under 1000.00 in most cases) so it would be close to the same price including the car

frankenstein motors

OK so after much thought on the subject I decided to delete the ABS brakes from my car. It will make some things much easier in the long run. I sourced a proportioning valve from a 1992 Honda Prelude for 7.00 from a local salvage yard and after some research found it to be a very sound part. It is small easy to mount and should also eliminate the wiring for the ABS making for a very clean install. The ABS light is easy to fix on the gauge cluster as I will have to eliminate the traction control light anyway while I am in there I will do the same for the ABS light. The batt light is an easy fix also I will tap the line directly from the led to the analog signal from the LS PCM and that should fix that one. All that said I will add pictures this weekend as I work through the plumbing of the brakes.

SHARKBITEATTACK

Cool swap. What's a LS RX8 weigh compared to a comparable LS RX7?

frankenstein motors

The RX8 weighs 3,064 to 3,111 lbs. Depending on trim level. With the LS swap done correctly you can maintain the 50/50 ratio and keep the weight the same. By replacing the electric power steering that saves 35+ pounds and removing the wiring that is not needed saves more weight than you would expect. Rotaries, while small still weigh more than you would think (247lbs) add the manual transmission to that and you come in at about 365lbs, an LS1 with a T56 including all manifolds and accessories weighs 497 lbs so with a difference of 132 lbs. up front, you can move the battery to the rear lose the above mentioned wiring and electric power steering and you can see that the car will weigh about the same.


A RX7 FD3S with a well done swap will weigh about 2900 to 3000 lbs, I have seen them as light as 2700 but that was a stripped down car.


The cost and availability of the RX8 makes them a prime candidate for a swap. It is becoming easier to do the swap as more people do them. I will share all the knowledge I gain by doing mine. The wiring is the hardest part.

SHARKBITEATTACK

Good to know. I've always liked the chassis of an RX8, just disappointed they never came with a turbo. LS will fix that!

frankenstein motors

I had a lot of time to work on the car this weekend and I tackled the engine bay cleaning and painting, and a lot of wiring.
I have changed direction slightly with the car due to product availability and lack of customer service from Hinson. I have decided to go with V8 Roadsters mounting hardware and other items. That said I will be removing the electric power steering and I also decided to eliminate the ABS. I had the Non DSC controller and could have kept it but I bought a 1992 Honda Prelude proportioning valve and will install it. It was very easy to remove the ABS system and I am not one for cutting wires so I unpinned the ones not needed and removed the relays and fuses as well. The harness from the Mazda ECU to the Fuse box is done. I am working from the fuse box to the interior harness now. I did remove the harness to make it easier to work on and also to paint the engine bay. By removing the ABS and Electric power steering there really is not much left. All the fan and fuel wiring fuses and relays are gone as well, removing the pedal position sensor wiring and relay also cleaned things up. Mazda potted the wiring harness at the bulkhead so that took some time to strip away but the finished product will be much nicer. I have attached the pinout for the ECU. I will take pictures of the fuse box and wiring harness before I put it in the split loom. Use this PDF as it is updated. More to come soon.

frankenstein motors

Proportioning valve (1993 Honda Prelude Non ABS all wheel disc)


Wilwood clutch master cylinder


reused the stock brake lines


Cleaned and painted the engine bay


Looks pretty good if I do say sop myself


Fuse box prior to installing the wiring harness


A shot of one of the two plugs I had to unpin to do the wire tuck


better view of it


Still another view


Yet another view


The other plug I had to unpin prior to removing the deleted cut plugs


Same just a better shot


Still another shot


Looming the tucked harness


The wire installed in the driver side fender channel


I had to cut the low spot and bend the tab up to get the plugs to fit in the channel


OK so I still have some wiring issues to finish up. Honestly it looks far worse than it is. this is how they looked after pulling the loom through the channel.


After the wire tuck


The two plugs I had to upin

I did a lot of work on the car the last couple of weeks. I installed the brake proportioning valve reusing the brake lines, put the brake and clutch pedal in the car, did a wire tuck and removed the factory ECU altogether. The wiring challenge is working out pretty good and after I get all the grounds hooked up I will install the battery relocation kit and put some power to it to make sure the interior still operates. well enough of that on to the pictures

Michael Yount

iTrader: (1)

Can you tell us more about the Prelude proportioning valve? Seems like the front/rear split for a front wheel drive car (60/40 or 65/35 front/rear weight split) wouldn't be a very good match for the 8.....but that's just off the top of my head. I'm sure there's more to it...

frankenstein motors

OK so the RX8 uses left Right bias on the ABS module and the master cylinder for front rear bias. The Honda proportioning valve I chose does the same. The two I found that are readily available and cheap are the Honda Prelude 1992-1996 non ABS all wheel disk and the Mitsubishi Eclipse with the same options. Also the Mazda MX5 2006-2015 cup car uses a proportioning valve instead of an ABS module, they are available from your local Mazda dealership for about 85.00 I bought the one I got for 7.00 at the local pull a part. The bias numbers are the same for each of the above examples and the stock RX8. Now if you want to keep the ABS function with swap all that is needed is a Non-DSC module. Then you match up the wire colors and add a 12v power supply and there you go. I chose not to use ABS because I want the car to serve double duty as a daily driver and track car.
I hope this was useful.

Michael Yount

iTrader: (1)

My point was that the proportioning split (pressure cut) a valve designed for a fwd or awd car uses is likely not optimal for a rwd car. Result being that you likely won't get all the braking out of the rear tires that you could. Certainly in the safe direction - fwd valve (65/35)on a rear wheel drive car (50/50 is your target) will lock the front tires first, I'd guess it won't lock the rears at all. Given all the changes to the car, an adjustable valve would be appropriate, especially for a track car if track means road course. Fwiw...

frankenstein motors

Ok not to sound like an @ss but if you really want the technical data here you go. The Delta "P" between the front and rear wheels in a braking situation differ from a static situation of, lets say a 50/50 weight biased car than a 60/40 weights biased car. In a dynamic (car in motion) situation the weight transfer is far different and there are many variables to consider, fluid dynamics, heat, and contact patch being just a few. When the car is in motion the weight transfer along the axis of motion is expediential to its static weight, thus braking is also expediential. The RX8 uses the master cylinder for front and rear brake bias not the proportioning valve, the proportioning valve is used to correct the left right weight bias during cornering or hard braking. Since I removed the ABS unit from my car the wheels will lock up under hard braking, however the question as to which wheel will lock up first is dependent on many things. The aforementioned items being just a small portion of that. The valves I researched have the same bias numbers as the MX5 cup car non ABS unit. The master cylinder for the RX8 uses a 48/52 bias split (hard to see when looking at it as compared to a domestic car with disk front and drum rear brakes) Now the weight of a swapped RX8 remains close to the original weight with a similar weight distribution fore and aft. My concern when removing the ABS unit was not so much the fore and aft calculations as it was the left right bias numbers and the battery placement in the trunk. To get a balanced feel in the car not only static corner weights had to be considered but dynamic ones as well. Speed is a big part of the equation, as it changes the dynamics throughout the braking spectrum. So with all that said I did not just go to the junk yard and pick a small valve because it would fit, the numbers had to match also. The numbers for the previously mentioned valves do just that. I do not have a skid pad to prove my research but I will get as much data when the car is on the road to update this topic. I hope this was helpful. It is nice to see that people are really concerned with the details of a build. Thanks for the questions. I am very OCD when it comes to the details of the build and will spend a lot of time on just one aspect to make my build stand out from the rest. The wire tuck aspect being one of them, most people would just use a nice loom and be done with it. Yes I like the pain . Thanks Again.

Michael Yount

iTrader: (1)

Thanks for the extra detail - I understand better now. It was "track day" that garnered my attention. More than a couple seasons of racing (and a couple of regional championships) under my belt. All too familiar with changing dynamics vs brake bias - burning off fuel load, wet vs dry, topography ( braking downhill vs uphill), tire wear and driver preference also play big roles. That's what always steers me towards something that's adjustable, preferably on the fly.

frankenstein motors

OK so the wire tuck and removal of unnecessary circuits is done and I put a battery to the fuse panel and everything inside the car worked. Windows, locks, lights, gauge panel (lights only) everything. I could not have been happier. Next up is the fuel system and battery relocation. For the battery I went to the local Airgas supply and bought 30' of 1/0 fine strand cable. I already have a new battery box so I will run the positive lead to the fuse box ground the negative in the back of the car and that should be that. When the LS is put in place all I have to do is run a 1/0 to the alternator and from there to the starter. Pretty simple stuff there. I am going to remove the gas tank for the fuel system change for no other reason than to remove all the Mazda fuel system parts and to clean the area. I will take plenty of pictures of that. I do have the gauge cluster out of the car and I am working on the tach, speedo, oil and water pin out. I am also removing non-required LEDs from the warning panel. That part will be a bit of a challenge but I have time. Any help with the tach and speedo would be greatly appreciated.


As far as I can tell the oil and water gauges are not really gauges at all. They use an on-off logic and reference RPM for sweep. I will make them work but add aftermarket gauges to keep an eye on what is really going on.
Well that all for now.

casias

iTrader: (1)

When I did my Dakota, I used welding wire to relocate the battery under the bed behind the right rear wheel. 5 years, no problems.

As for the dash, the Dakota had the same thing. They are kind of dummy guages that run on a bus system. After removing all of the extra idiot lights and unused things, the gauge cluster didn't justify the drivetrain.

I made them work, but them pulled them out and put autometer.

frankenstein motors

got a lot done this weekend. I finished up the wiring and battery relocation. After powering up the car I ran all the systems and switches that are still in it and everything worked except the brake lights. I will have to track that down but it should not be too difficult. I also made a tool to remove the fuel pump housing and after a couple of busted knuckles and choice words out it came. I am cleaning the housing up and will route the new lines and install the pump then put all that back together.


On to the gauges. With my trusty multi meter in hand I shot the wires for the gauge cluster to find out it makes absolutely no sense. I can get all the lights to work and the fuel gauge to work but the oil and water temp will be a problem. Now since I am putting American muscle in this car I decided to go with the Dakota Digital universal gauge cluster. It has a similar footprint to the stock gauge cluster and will just work. It cost about 800. and has some extra features that will be nice. It will solve all the interior problems and with it wiring will be a breeze. I am currently modifying my stock gauge mount so the Dakota piece recesses and looks like it came that way.


I am in the market for a GTO pullout with T56 trans if anyone knows of one available. From this point on it is a matter of just spending money. It is just plug and play now.


More updates as work is done.

RxV8

Hey I'm starting an lsx swap into a rx8, I just got the car last night. Would it be ok if I picked your brain a bit or pm'd you a list of questions?

frankenstein motors

I am selling my project because I am building a shop/house. It is listed on craigs list for 2500.00 there are more pictures of the car there but you can see all the work done to the car here. I still have most of the rotary parts and nothing is cut everything is done correctly as you can see. It has a clean title and no issues. Thanks