Need your input - stock twins, why did yours fail and what did you do?
 

Hey guys -

I'm taking a magazine writing article this semester and I'm doing one on troubleshooting and diagnosing problems with the stock twins.

I'm looking for some input in the article. Here's what I'd like to know -

- If your turbo or turbos died, do you know why they died? How did they die?

- What did you do about it - get another used set, get a rebuild, go single?

Again, I'm JUST wanting to know about the stock twin turbos, not singles or anything else. It doesn't matter if you're sequential or non-sequential.

Thanks in advance!

Dale

Mine were getting overspun by mystery boost leaks when i first got the car. They started using more oil and had some shaft play. I'm not sure how bad they were but i sold them off when i rebuilt my engine and put a t64 on. Much much better all around

I recently changed mine out, but when I bought the car the guy gave me two extra sets of turbos. So I just pulled the best two out and ported the wastegate before I changed them out. I am planning on going to single turbo sometime in the future tho.

I swapped mine out at 59,000 miles for a low mileage set. The previous owner must have really stomped on it a lot because the primary turbo was rebuilt, unfortunately it was never done right and it blew again. The new set works great!

I bought my 7 six years ago for cheap and was completely green about FD's which I didn't even know they were called FD's at the time. It probably didn't even make 2 psi of boost at the time, but I was SO naive at the time I didn't even realize it. Later, after much education and reading, I caught on to what was going on with my car and realized something must be done. So being naive as I was I bought used twins off of Ebay, and swapped them out in my garage. This was the 1st time I had ever worked on an RX7 BTW. The new ones, to me, worked, but it was semi-awesome after that. It made the full 10lbs of boost all the way to 4,500 rpm, but after 4,500 it fell flat on its face and made zero boost. I drove it around like that for awhile, but then I had enough of this annoyance. Especially when a Firebird egged me on, on the highway and there was nothing I could do about it but push it in 5th gear and look stupid.

I took it to the local Mazda dealership to see if they could fix the boosting problem and surprisingly they did! One simple check valve was the culprit of enjoyment. It was magnificent to drive this FD around they way the Japanese had intended it to be.

But all good things come to end, so they say, and one morning after working 3rd shift I left work flying down the highway at the top of 3rd gear, when pshhhthudcracklebangbllllugggg. "Oh crap, must be the boost signal vacuum line." However when I opened the hood that was not to be the problem, but something far more serious. So I floored it in 5th gear all the way home only attaining 60mph at tops. A blown apex seal and my lead foot was to blame for this mishap. SO...I ordered a street ported rotary motor from Atkins rotary to remedy the situation. I got it all swapped out to the new motor, still twin turbos, of course. One thing I think I did wrong was to change the fuel pump while the motor was out. Because when the new motor went in it never worked the way it should have; the way it used to. So for the last 3 or so years my 7 has not worked the way it should have. Stumbling around, falling flat on its face, not making boost, and just being plain irritating! I never knew what the problem was up until tonight, when I found that the fuel pump I had put in had a bad O ring and was leaking fuel right back into the tank.

During the time of irritation I decided to go single turbo, thinking this would solve many vacuum and solenoid problems. Many different times I checked the vacuum diagrams and looked over everything to make sure that I had the vacuum hoses and solenoids hooked up right. I always came to the conclusion I did. I checked all the solenoids to see if they were working and they were.I have consistently scratched my head to the problems with this car over the years.

I am not one of these purists who think that I should keep my Mazda the way that it came from the factory, but I do like and respect the twin setup. It is nice to have the power right there when you stomp on the pedal and the 10-8-10 transition is not that bad, IMO. However, there is a cap to the stocks ability to create Hp and go beyond. So I decided to go with a single setup for a few reasons. Simplicity, potentially more HP, if an issue arises the diagnoses should be reduced and hey, it looks cool under the hood :)

Which this brings me up today. So there is my abbreviated personal RX7 ownership history and my life with twin turbos. Twins are good if you want the instant acceleration, plan to just drive and enjoy the stock capabilities of an FD RX7 or with slight mods, and if you truly like what Mazda engineers created with a complex rats nest of vacuum lines and solenoids.

It's like shitting blood
 

These are probably the originals. The engine was rebuilt by the previous owner but I think the turbos are originals.

Time between first sign and actual decision to swap to 99 spec turbos: < 1 year

It started with a puddle of oil in the intercooler. Sopped up and ignored.

<5k miles later (or within 4 months)...

The y pipe started to accumulate a coating of oil on the lower portion of the primary. The vacuum hoses piped to the primary inlet would be coated in oil and dirt. The PS/WG actuators started getting dirty every couple of weeks. Full boost by 2500, still boosting to 10PSI perfectly. No oil on the floor.

A few thousand miles later...

The back of the secondary compressor side housing was coated in dirt and grime from oil. Still boosting perfectly.

Small drops of oil on the garage floor. There would always be a drop of oil hanging off the secondary compressor housing whenever I get under the car. The subframe would be gently coated in oil (this could also be attributed to an oil pan leak but I have not verified that yet since I have just now only completed the turbo swap)

Probably a couple hundred more miles...

The efini Y-pipe would be lightly coated with oil within 2 weeks. The car will always produce a nice trail of oil in the garage...enough to creep out near the side of the car. I checked the return line for leaks: none. The feed line: none.

The last sign before I decided to fix:

Sluggish at 10PSI. Boosted fine. It just had a different tone. I can't even describe it. It wasn't metal grinding or watery sounding boost. It just felt "grouchy" at full boost- it wasn't as responsive either. It wasn't an "oh shit" moment. Everything worked okay. Transition still good. One notable thing was that the primary K&N intakes started to get darker faster than expected.

Summary:

Basically it's like if you start shitting blood. At first you're like "well, let's wait and see if tomorrow I still shit blood- it's only 2 drops." Then when you still see more blood, you think..."maybe it's nothing. I feel fine. Must've been something I ate. Let's still wait and see. I'll only eat rice cakes tomorrow." Then finally when the toilet is filled with blood and it hurts to shit, you say "Perhaps I should go see the doctor now."

FANTASTIC stuff, guys! Keep 'em coming!

Dale

My original turbos seemed to be working fine when the coolant seals went bad on my original motor at 62K. I dropped the car off at the rotary specialty shop (230 miles away) for a rebuild. When they pulled out the engine, they checked the turbos. They had some significant cracks, and were going to need replacement before too much longer. I opted for 99 j-spec twins. They seem to run just a little stronger at low rpm.

When I went back to pick up the car, there were so many little things that were done badly, that I forgot to ask to check out my old turbos. I never did get to see what they looked like.

Bought my new project 7 over the Summer.

Reman allegedly has 15k on it, the twins had 28k

Car was BONE stock when I purchased it in Ft. Worth and driven back to Austin... since I did not know the history of the car I was very careful not to get on it and drive it as tamely as possible until I was on my own home turf where, if the car decided to break down, I could fix it.

I get back to Austin and find that the car was not boosting the same as I remembered from my first FD that was still sequential. (While this was five years ago, I still remembered that great low end power they produced and this was not right)

The main problem I was experiencing (keep in mind I did not yet have a boost gauge, it was still being shipped) was that the car was not transitioning over to the secondary turbo --- I did not know this at the time because I had forgotten what the transition felt like.

I do a few hard pulls on the highway to see if possibly it was carbon build up / a clogged cat (this worked in the past for me). I did a total of 5 hard pulls.

-Pull 1: 3rd gear from 45mph to 100mph car boosted poorly, my butt dyno was telling me something was up

-Pull 2: Same thing but this time the car seemed to start boosting, in and out

-Pull 3: Same thing and again, the powerband was very flat

-Pull 4: The car took off like a bat out of hell, caught me by surprise (hmmm)

-Pull 5: Very flat powerband again, what the heck is going on...

The next day I dig into the engine bay and begin checking all the vacuum lines that could be culprits, all of the vac lines and solenoids are fine... I am scratching my head here.

I decide, what the hell and pulled out the OEM intake box, and the 1" hard lines that run to the PRV and the CRV. I had found my problem low and behold, the 1" line that runs to the CRV I believe ( I cant remember, but it was the 1" line that runs from the middle of the Y pipe), had a significant crack on it where it met up with the Y-pipe nipple. I could not see this from above or below the car because the metal clamp was covering the crack ( you would never know until you removed the hose ).

-In a nut shell, since this hose was leaking pressure, the primary would kick in fine but then when the system was supposed to pressurize and the actuator engage the secondary, the primary was essentially being shut off (for the transition) and then the pressure was not high enough to engage the secondary so I was basically driving N/A (its a terrible feeling). My hypothesis on why it would work intermittently in 4th or 5th is that the car is under a greater load, more internal pressure and sometimes the secondary would engage and when it did, it was FAST - this is probably due to the fact that the car was over boosting (dangerous) because it was trying to pressurize the system to spec. while pressure was leaking out, so when the secondary DID engage, it was way over 10psi. Anyways..

I go to Autozone, pick up some hose and make a temporary and take it for a test drive, my butt dyno was alive again!!! I was loosing traction in first gear and it was glorious!

All was going amazing for a week after fixing it and then the car started to feel sluggish at low RPMS and I noticed my vacuum was a bit off at idle. Generally it would pull 19-20 inches of vacuum and now it was between 17-18 inches ( I had installed a boost gauge by this time and I knew something was up ) I was still getting my 10-8-10 but the boost was building slower than the ass and boost gauge recalled... time to dig into the engine bay again and time for an exam...

Ill be back in two hours I have plenty more to this story

the reasons turbos get changed vary.

when i was at the dealership, and these were under warranty, we used to change em for no reason at all!

now the cars are old, and the owners are young. the turbos get changed due to oil use, or cracks.

i have seen a broken shaft, but its very rare

So I am going over the engine once more to figure out why my turbos are giving me trouble. This time it was vacuum related and again, had I not tried to physically remove anything I would have never known it was broken.

The culprit this time was a check valve that ran from the front of the UIM, it looked fine to the eye but the second I touched it, the valve separated. It was not cracked, it literally just separated!!!

Went to autozone and picked up a new 1 way check valve.


I need to walk my dog so I am going to cut to the end of the story --- my car was going great, driving amazing and pulling like an ox. I had the car tuned to 14 psi and was making roughly 310 - 315 hp.

Car is quick, responsive, drives like a dream... the higher levels of boost was causing a higher degree of pressure to build up inside the vacuum lines. This increase in pressure was popping all the lines off that became pressurized ( my fault for not zip tying them down )so the night before I am leaving to drive 1000 miles to colorado, at 1 in the morning, I am going through my engine bay zip tying all the hoses that could be problematic under boost

Fixed that.. good

The place where my turbos (and I still have not figured out if it is my turbos or my engines oil control o-ring) crap out on me is in Boulder, CO at an elevation for 5,400 feet - basically a mile in the sky.

After making it all the way here, I notice my car is making an impressive amount of smoke. I do not get smoking at WOT but instead just after WOT when I get back on the gas after decel (PLUMES OF SMOKE) --- I pull the intake elbow off and the inside of the throttle body, just in front of the butterflys is pooled with oil.

All my intercooler piping is drenched with oil, I pull my intercooler and gobs of oil come dripping out.

I am still stumped as to what happened, and I am hoping to god it really is my turbo oil seals but I am still not 100% sure but I had HUGE amounts of oil in places that it should not have been and it all occured over the 1000 mile drive from sea level to 1 mile elevation.

Pictures included as well as a link from my experienced problems:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/oil-leak-related-my-omp-lines-784734/

I picked up my FD back in 2000 with a new motor in it. The turbos went out and dumped lots of oil into the intake about a week later. I think they were off balance from an apex seal going through when the motor was blown.

I put on a set that looked very good but had 110k miles on it. They lasted me another 60k boosting at 14psi when I replaced them because I thought they were making rattling sounding noises. Turns out they were perfectly fine and my noise was from an exhaust leak. Any way, now for the last couple years I am running a used but almost brand new set and all is well with the world.

Turbos were on the car when an Apex seal went (@45k, before I owned the car), metal chipped the fan blades and slightly bent the shaft. But the fun didnt stop there.

Replaced the turbos with BNR stage 3's (and a new engine) at 58K miles due to an engine coolant line going and pouring my coolant all over the road leading to an epic overheat and a cracked housing on the secondary that dumped a bunch of oil all over the engine bay.

swapped for a low mileage set at around 40,000 miles. secondary was starting to burn oil and shaft play was starting.

I ended up going full non sequential on a new rebuild w/ my original stock twins. They ran 10 psi for 50k, 12 psi for 10k and blew the rear oil seal at 15 psi after another 9k. Thats 69k total for those. Put on a low mileage and have 6k @ 15psi so far but I am starting to see signs of seal failure again (light smoke on start up and a bit of smoke on decel after WOT. Still pull hard though. I will run these till they smog out. G

Apex Seal Ingestion

Staying sequential (because that is how the car is meant to be driven)

Going BNR Stage 3's

massive nasty screeching sound as the secondary began to spool. parked it until i found a good set. ended up with one good turbo from a friends set. a little canibalism later and all was good

My twins decided to leak all my oil and I spun the front bearing and needed a rebuild.

Just replaced mine last weekend at 107k miles with a lower mileage set I got for my birthday :). Old ones leaked oil out the primary inlet. Pattern was 7-5-7, never burnt oil. New set is on and it is so nice to drive the car with the power that it was meant to have. Now I just have to solve my boost spiking issue on the primary. One problem for another I guess :)

Sorry, no contribution here... 98K miles on original engine/turbos, no problems. ('94, orig. owner)

My stock twins survived two rebuilds (one for coolant seal and one for apex seals). I decided to replace them with new J-spec '99 twins after the last rebuild because they had about 120K on them.

According to the engine installer, the old twins are still good and they're currently sitting in my garage. I'm planning on sending them to BNR eventually to get upgraded so that I have a backup set of twins.

Just replaced my original set. They had 80k on them. I talked with Dave at KDR Rotary in PA, and he suggested to the PO to replace the turbos when he rebuilt the engine at 70k. The PO refused due to lack of funds.

I replaced them because they were pooling oil in the intake tract and causing a huge billowing smoke screen on startup.

I replaced them with a low mileage used set. I wish I could have afforded BNR's, but not right now.

By the way, I talked with Majestic Turbos in TX and they told me they are no longer rebuilding the OEM turbos due to the high failure rate of the rebuilds. FYI.

My stockers had ~130,000 miles on them and were still boosting fine @ 13 psi on a daily basis. They were replaced by BNR 3's when the engine was replaced (coolant seal). Some shaft play was evident in the set that was removed, esp. on the primary side.

I heard BNR's last longer than most motor rebuilds... unless you're boosting 18-20 psi on the track every weekend. Might want to use/save those funds instead for the next rebuild.

i plan on getting BNR's with the rob bailey solenoids full seq at 17psi!! 400whp.. ohh baby!!