1983 mazda rx7 engine swap ideas
04-27-15, 08:55 AM
#26
carb whisperer
Before I accuse you of being blinded by prejudice, or brand loyalty, or a few good experiences that were mostly just luck with the first thing you ever tried, I must resort to facts about the above.
200 HP is as much a tool, a point of reference, as a rating. 200 HP isn't much for a 3.8L V6, but with fully twice the HP of the rotary this car was built with, and EPA-rated at 25% better MPG despite higher speed limits now and a bigger, heavier car, and triple the displacement, this is obviously far more efficient than the rotary. It's 300,000-mile reliable, with nothing more than 3 sets of spark plugs, and regular oil / filter changes. Plus on top of all that, it meets Ultra Low Emissions standards. And if there ever is any problem, every mechanic and every auto parts store can help immediately.
Potential? a guy who goes by FieroX has his GM 3800-II V6 running 9s in the 1/4 mile, turbocharged, still averaging over 30 MPG, with not one breakdown in the last 4 years of daily driving plus trips to the dragstrip. No junkyard rotary can ever claim any such thing. Oh, and FieroX can also pass emissions for '96.
Mine is a MPG build. 35 is known fact easily repeatable. The goal is to occasionally spike near 50, mostly due to less aero drag and trying ever less RPM at cruise.
With a GM LSx piston V8, consider the common and cheap 4.8L truck version, available in any salvage yard for around $300 complete, yet proven capable of surviving 1200 HP of twin T76 turbos, with porting, injectors, a cam, and a tune. Stock pistons, rods, crank, et cetera. With the right cam, and putting the turbos after the right cats, this will still pass Ultra Low Emissions standards, and still be capable of averaging over 30 MPG, geared appropriately. I've read enough threads to know that 25 MPG is widely considered good MPG for a 1.3L rotary. I had a carbureted 5.7L V8 in an older Camaro do 25.1 MPG at 65 MPH with the distributor's centrifugal advance not working. So noone can claim a rotary is efficient.
It has no potential, it gets no MPG, it burns oil, so it can't meet Ultra Low Emissions standards, and it's as heavy as an aluminum-block LSx V8. Where's the advantage? It also, as icing on the cake, makes no off-idle torque, which is what makes big V8s fun. It revs? So what? Ever heard a 4.8L at 7500 RPM? No,you haven't, but I have, and it's better than any rotary at 9000, which I've also heard. It just means taller gearing, which it has the torque to pull. You can't have your cake and eat it too with a rotary. Checkmate.
200 HP is as much a tool, a point of reference, as a rating. 200 HP isn't much for a 3.8L V6, but with fully twice the HP of the rotary this car was built with, and EPA-rated at 25% better MPG despite higher speed limits now and a bigger, heavier car, and triple the displacement, this is obviously far more efficient than the rotary. It's 300,000-mile reliable, with nothing more than 3 sets of spark plugs, and regular oil / filter changes. Plus on top of all that, it meets Ultra Low Emissions standards. And if there ever is any problem, every mechanic and every auto parts store can help immediately.
Potential? a guy who goes by FieroX has his GM 3800-II V6 running 9s in the 1/4 mile, turbocharged, still averaging over 30 MPG, with not one breakdown in the last 4 years of daily driving plus trips to the dragstrip. No junkyard rotary can ever claim any such thing. Oh, and FieroX can also pass emissions for '96.
Mine is a MPG build. 35 is known fact easily repeatable. The goal is to occasionally spike near 50, mostly due to less aero drag and trying ever less RPM at cruise.
With a GM LSx piston V8, consider the common and cheap 4.8L truck version, available in any salvage yard for around $300 complete, yet proven capable of surviving 1200 HP of twin T76 turbos, with porting, injectors, a cam, and a tune. Stock pistons, rods, crank, et cetera. With the right cam, and putting the turbos after the right cats, this will still pass Ultra Low Emissions standards, and still be capable of averaging over 30 MPG, geared appropriately. I've read enough threads to know that 25 MPG is widely considered good MPG for a 1.3L rotary. I had a carbureted 5.7L V8 in an older Camaro do 25.1 MPG at 65 MPH with the distributor's centrifugal advance not working. So noone can claim a rotary is efficient.
It has no potential, it gets no MPG, it burns oil, so it can't meet Ultra Low Emissions standards, and it's as heavy as an aluminum-block LSx V8. Where's the advantage? It also, as icing on the cake, makes no off-idle torque, which is what makes big V8s fun. It revs? So what? Ever heard a 4.8L at 7500 RPM? No,you haven't, but I have, and it's better than any rotary at 9000, which I've also heard. It just means taller gearing, which it has the torque to pull. You can't have your cake and eat it too with a rotary. Checkmate.
No checkmate, simply preference. One could argue ford engines are more efficient than rotary too. Or Fiat, or Toyota. Who cares? My twin draw through 429 boat engine might be more reliable than the GM 3.8, and makes tons more power. It can be worked on by any shade tree mechanic too, since at its core it's a 50 year old ford engine. Am I scrambling to swap it in my FB? Nope. Is it better though? Arguably.
Wouldn't be worth the work or finances to do it. The engine that's in there has given me decades of good service, and until I decide to pull it to go through it, it will continue.
Makes perfect sense to spend less money on what I know works. Before you argue with my logic, realize that's what you've done exactly by using the GM 3.8 you're familiar with.
Most of the guys here on the rotary forum have a lot of experience with them. Suggesting that all the experience here isnt accurate or "brand loyalty" and not expect in resistance is akin to walking into a Mopar event to announce that none of them know what's good since they don't drive GM.
Thread
Thread Starter
Forum
Replies
Last Post
thecody59
1st Generation Specific (1979-1985)
14
01-23-16 11:52 AM