Soravia

Mod Edit: This was bumped from the grave...

I'm trying to see what kind of stuff people has to go through when RX-8 gets a different engine.
I can see fab on Engine mount, Exhaust down pipe and transmission mating. But I'm interested in ECU wiring to the car, like the tech meter and door sensors and remote door locks.

Thanks
And please don't flame for pulling out the RENESIS. It'll probably go into a Track Only car.

kevinD1226

yea there are a few rx7s out there with piston engines.. i believe the common swap is a LS1 might be wrong thou.. also i read on this forum the other day someone is in the process of swapping a 2jz in an RX8 which id love to see a video of that at a track.. so yes its not uncommon to read about rotaries gettin swapped out for piston engines..

kevinD1226

i should say there are alot of rx7s out there who got a piston engine swapped into it.. just to clarify any confusion..

Soravia

I've seen them as well. But I'm concerned about the electronics inside the RX-8 working with the piston engine's ECU.

This is not going to be a race car but a daily driver with enough torque and gas mileage. (around 130-170 wheel torque @ 3,000-3,500 RPM and 22MPG city). The RENESIS gets 80 Torque at that RPM and 15MPG in city.

I'm considering a rebuilt Nissan KA24DE with small turbo at 5psi boost. The KA24DE is a very simple and cheap engine in both mechnical and eletrical parts.

dmorales

On kind of a side note...if you search the site there is someone who posted their v8 Rx-8. I beleive there were even pictures. But ti was a loooong time ago.
________
Fantasydoll cam

costello

I've encountered a 2nd gen RX-7 with a V8 at Roebling Road. Thought it was my friend in his regular RX-7 until we hit the straight away. It was crazy fast down the straight. I think the V8 would change the balance of the car though.

Soravia

Not if it's a small V8.
This is not going to be V8, it's not about power. It's about Torque/Gas Milage.

I've read someone mention on the forum about having 2 ECU. I suppose I can have the KA24DE ECU running the engine and the RENESIS ECU reading out the engine speed and electrical sensors such as ABS, Door, oil pressure, TEMP, DSC, Headlight etc.
Is that possible? I think the Check Engine light will be on all the time. (I'll be disabling the ABS though. I hate that thing)

BlackRX82006

iTrader: (1)

Man, you're talking about serious money in modifications

kevinD1226

yea with the money of the overal car and then add the money u spend on doin a swap like this u could have bought a used m3 or something..

Soravia

I don't think it'll be too much to pop in a Nissan KA24DE engine. Junk yards sells them for $300. With tranny and ECU the whole deal it should be like $600.

Mounts and Exhaust will need to be fabbed. The KA24DE wiring is exretmely simple so that's no issue either. Time and place can be rented cheap too.

The real issue is to have the KA24DE engine working with the Sensor read outs in the RX-8 gauges and to have the KA24DE engine mate to the RX-8 Manual Transmission. EDIT : Steering rack will need to convert to hydrolyics too.

Estimated total cost of a fully rebuilt stock spec KA24DE (with higher compression and reprogrammed ECU) would set me no more than $1,500.

Correct me if I'm wrong, I believe that on identical cars with identical drivetrain engine with higher torque per liter of air (and by extension also gas) would make better mileage than engine with same liter of air but lower torque.

Here are the Dyno for both engines at the wheel. All Stock.
RENESIS


KA24DE

BlackRX82006

iTrader: (1)

Factor in having to replace things as well. If you want gas mileage, buy an old bug

Rootski

iTrader: (1)

So you're going to spend thousands and work your *** off for slightly better gas mileage and a modest torque increase? You'd achieve your goals much more easily just putting a turbo on the renesis.

BlackRX82006

iTrader: (1)

I'm not bagging on the idea. Althought it's not practical, it seems pretty cool. Even cooler if you would shove a V8 in there.

Soravia

How would a Turbo RENESIS make better mileage than a NA RENESIS?

Please explain. I already know that the cost of a Turbo RENESIS is RX-8 Cost + $5,000 range.

As I mentioned before, the cost will be covered by selling the RENESIS.
The mileage cost between the RENESIS and KA24DE is $100 a month (30 miles a day) and $1,200 a year. $1,200 a year is the cost of one year insurance for RX-8 (varies by driver). That is IF the gas prices stay at $3.0 per gallon.

(I'm also planning out an E85 but they are hard to get in Florida)

BlackRX82006

iTrader: (1)

I see where you're coming from. But how many mpg are you going to gain? 2-3?

Rootski

iTrader: (1)

I think you're being inredibly optimistic about what this engine swap is going to cost. The turbo alone for that nissan engine is going to be more than $1200. When its all said and done you'll blow more money and have more headaches than you'll make back at the pump. If torque is your concern, turbo the renesis. If gas mileage is, drive conservatively. If its both, buy a different car and save yourself a lot of trouble.

Soravia

My S-13 240SX with KA24DE makes 25-30MPG after removing emissions. (21-26MPG stock)

RX-8 I drove for a month made 15MPG on the same route to work and back.

The weight difference between Stock RX-8 and Stock S13 is exactly 300LB. Swapping the KA would make extra 70 or so on the weight but I'm expecting a reduction in weight by using lighter custom intake and exhaust manifold and moving the battery to keep near 50/50 weight.

The reason for the mod is not just the torque nor the milage. I just want the RX-8 chassis. Lighter than 350Z with same suspension setup, rear seats that I don't have to get out of driver seat to use, huge trunk space and great accident impact rating.

I'll be driving a Miata before I do the swap. Right now I'm driving a 240sx. Great handling car with torque for mileage, but poor interior and absolutely no insurance value.

Miata is just too small for accidents and I hate converts.

J8635621

iTrader: (10)

The Renesis doesn't make 80 tq at 3-3.5k rpm, just look at the dyno chart. And would just an engine swap really make that much of a difference in mpg with the same gearing?

dothackRAVE

Get a Corolla. Seriously. No one buys an RX-8 expecting good gas mileage. If someone did, that someone is a ******* idiot.

I get 11mpg mostly, and I still lulz at the gas prices. Gotta pay to play.

Soravia

Any idea to make better mileage on the RENESIS? I think that part has laready been explored many times.

I don't think I can get any more info from the forum. I'll just go look on my own. At worst I'll endup with gauge pod infront of the OEM gauges.

nelsonrx8

im going to tell u like this leave the 8 as a show car and get a project car

the 8 will never be a really fast car and for gas miles wait till spring and see what pops up

this is a drunk man telling you this muahahahahahaha

Rootski

iTrader: (1)

Shift before 3,000 rpm to keep the secondary injectors offline.

Part of the great RX-8 chassis comes from the size and placement of the engine. Throw in something else, and you'll diminish that. No telling how much, but it won't be the same.

Soravia

I'm also lookig forward to the new engine as well. If it runs great for Torque/Mileage, I might end up getting that X16 engine.

Which is why I'm getting a Miata for now and leaving the 240SX in the garage for track use.

I thought the second injectors starts at 4,750 rpm???? No?

I shift the RX-8 at 3,000-,3500 RPM. On the 240SX I shift 2,500-3,000 RPM.

Many people are either "Get a V8 or Get a Civic" I don't want a V8 and I don't like Civic (any FWD). I like the RX-8 Body and I want it for that. I don't care what engine is running inside. Just trying to keep the gas cost down as I will be driving it daily. I don't see a reason to keep a great car in the garage and drive a beat up car every day. (unless it costs $100K)

Rootski

iTrader: (1)

It's called 16X and won't be around until 2010.

And you may be right about 4,750 rpm, I wasn't sure. 3000 is where I shift when I want mileage.

nelsonrx8

240 sr20det is the ticket

why did mine get stolin