billymild

Every single RX-7 I see for sale has an "engine rebuild within the last 1000 miles or less". That is concerning to me. Lots of them are not built engines either. They are stock rebuilds. That is kind of interesting to me. They either are lieing, or these things after being rebuilt people stop driving them. Thoughts, concerns?

Narfle

iTrader: (16)

It's a common circumstance when people dump a lot of money into their FD, need a rebuild, and cash out their car at it's highest resale potential (mechanically pristine). If you have some concern about the engine health and are serious about the sale, ask for a compression test.

bajaman

It's due to the general public's perception of the 13BREW as being a "time bomb", so peoples' nerves get calmed somewhat when they see a recent rebuild.


I see parallels in the boating world all the time; you'll constantly see things like, "only 200 hours on rebuilt engines". Boat engines are stupid expensive to rebuild or refresh, about 4 times more expensive than a car. So it's that same "warm and fuzzy feeling", the sense of, "Oh! I should get years of use before anything major goes wrong...", that FD purchasers share, too.

BLUE TII

iTrader: (9)

Honestly, I think it is because when FDs lose their engines people decide they don't want them anymore, but most can't handle selling it as a roller for $5-8k when it would be worth so much more running.

They get it rebuilt and sell it for $15-20k.

Maybe they spend $5k-10K on the rebuild/labor at a shop but just feel better selling it for more money.

Maybe they spend $1-3k on a rebuild and do the labor themselves and make more money on the sale.

At best, the reason it is for sale with very low miles is they decided to sell it once they lost the engine.

At worst, the reason it is for sale with very low miles is they decided they wanted to keep it when it lost the engine, but the rebuild was bodged or put a strain on their relationship and now they want to get rid of it after all.

Then, there is sometimes the guy that loves FDs, knows how to work on them and wants to make a bit of money so he buys non-running FDs to rebuild them and sell them at a premium while enjoying them for the time they are running and for sale.

arghx

iTrader: (3)

A lot of people can get the engine in there but can't get a good tune on it. They dont want to try ot themselves and wont pay for the comprehensive tuning it needs for thr street. Few cars are stock enough to run on a stock ECU now, so tuning becomes more important.

A poorly tuned FD, coupled with things like A/C and power steering removal, make it a chore to drive. So they try to cash out before they blow something up, or before winter comes and the market cools off.

GoodfellaFD3S

iTrader: (213)

I think it's just you, I've recently looked online at over a hundred FDs for sale nationally on many different websites and was just thinking that the majority of them actually *didn't* have freshly rebuilt engines.

Build them right, mod them right, be a conscientious owner (read:non-idiot) and that clears up a lot of the issues and really helps kick Murphy square in the nuts

7_rocket

iTrader: (6)

So much to learn young lad

H_M

iTrader: (7)

I've seen this happen a couple of times in the last while. Someone buys an RX7, blows the engine, gets tired of the car and wants to get rid it, rebuilds it themselves on the cheap (cutting many corners), and then sells the car so some unsuspecting buyer. In both cases the cheaply rebuilt engine blew within months and both cars are back up for sale by the new owners, both with blown engines.

Natey

iTrader: (19)

Like Narfle said. Compression test and receipts are what I'd ask for when they claim rebuilt engine.

"Oh yeah, me and my dad rebuilt it in my backyard with used ebay parts. Only took us three years. Dad worked at a Goodyear tire store in the 70's so he definitely knows his way around an engine."

Moe Greene

iTrader: (2)

I would be so concerned is someone was selling a RX7 with an "engine rebuild within the last 1000 miles or less"

From my understanding proper break-in is 1500 miles, so either this person is full of it or did not do a proper break-in. If they don't let you redline the car don't buy it, if they let you redline the car then they be prepared to have issues like low compression since a proper break-in was not done.

wstrohm

My understanding is that break-in is 500 - 1000 miles. But I read conflicting accounts of what is required during the break-in period. We have about 100 miles on our new engine/turbosystem. I'm using TC-W3 premix at a concentration of about 8 oz per tankful, and car is being driven on short trips in town between 2K and 3K rpm, staying off turbos as much as possible. This corresponds to Yoshiya's recommendations. The 2-stroke oil is in addition to the OMP-supplied engine oil injection.

Question: How long should this procedure last? I'm planning on continuing the premixing indefinitely, but rpm restriction and light-foot operation is both stressful and boring. Seems there should be some sort of "curve" rather than these strict rules for the entire period. At the rate this car is driven, it will take about a year before passing the 1000 mile mark!

arghx

iTrader: (3)

Remember, when this car was new, at least one person went WOT on it with basically no mileage. It was either somebody at the plant or somebody at the dealer. So it's not going to permanently have some kind of problem if you boost it. Engines also get hot tested, where they randomly selected a few at the plant and put them through their paces right after being built.

the reason you break in an engine is to get the friction in the engine down. I've got a lot of experience with this on piston engines in my day job. Usually you slowly ramp up speed and load over about 20 hours of operation (this is in an engine dyno lab). As you put hours on it the fuel economy improves, the power improves, and the idle stabilizes as the airflow requirements change.

wstrohm

Perhaps for a new car, but how about for a crate, short-block engine? Isn't it possible that the engine was built, inspected, and shipped without such initial treatment?

Is there a generally-agreed upon break-in routine for a rotary engine? Mazda's recommendation in our 1994 Owner's Manual is attached below. Comments?

Edit: For some reason, choosing an attachment for upload dead-ends without uploading it. So, I quote from page 3-5 of our RX-7 1994 Owner's Manual under "Break-In Period:"

arghx

iTrader: (3)

I don't disagree with the owner's manual at all: vary the engine speed and don't go WOT isn't a bad policy. 600 miles is probably about 15 hours. I'm looking at the break in procedure I use at work (engine dyno, general procedure for piston engines of varying cylinder count and displacement). It has a cycle that ramps up speed and load. First WOT point is about 2 hours run time in, hitting WOT and going to 75% of red line, with peak power rpm first reached at 7 hours in.

As for the way Mazda builds them... video is here:


I don't know how Mazda is building these crate engines. Is it like the video above? do they use the same tooling to make housings and eshafts that they did 15 years ago when these engines were still in production? Do they have the same fixtures and assembly methods like in the video above? You can see that this is more sophisticated than a home or shop stacking parts on an engine stand for assembly.

Or maybe they are doing it like a low volume kind of deal, like a rebuild shop would do except with all new parts. They don't have enough volume to run a full 8 hour assembly line shift every day like they would have when the Rx-8 was in production. I'm guessing they build a few hundred a year.

With low volume it's less likely they have a hot test rig like a fully operational engine plant does, where every say 20 or 50 gets fired and run up to WOT a couple times. Then again, maybe they do; you can probably still get new Rx-8 engines, so maybe they have one facility that builds both, and hot tests for quality control.

wstrohm

Thanks very much for your response, arghx, I bookmarked the YouTube version of that video.