Hey guys I’m having this really weird problem on my fd rx7 . It started the other day when I pulled it out for a drive after sitting for about a month , when going into boost the first turbo spools up like nothing but when going up to 4.5 rpm you can hear the second turbo spool but getting no power . When letting off the gas it makes a weird bov sound almost like if someone it trying to make a bov sound with the mouth . Sounds kinda funny but the problem only happens after driving for a little while . I also noticed at night time when it’s cooler the turbo spools and I get power with no weird bov sound.

started looking into it and found a big crack on the charge relief valve hose so I changed it but no change. Anyone got any tips on where to start looking ? The vehicle is almost stock with nothing but apexi intake, hks bov and a catback exhaust .

 

If you found one cracked hose, you may have more.

Does your car still have the original rubber hoses in the turbo control system (rat's nest)?

After the original hoses become hard, they can leak intermittently, like only after they get really warm. This can lead to lots of difficult to diagnose things like the car working perfectly through the first drive of the day, and then having problems after being parked for a while (heat soak).

Your particular problem could be another cracked hose in the turbo control valve that is leaking intermittently.

 

Year of car and whether RHD or LHD, please.

If you have a S6, sound you hear sounds like if the big rubber collar between the y-pipe and the cross-over pipe is loose or damaged.

 

Sounds like secondary charge valve is sticking or the control lines/solenoid are damaged.

 

Check you apexi air filters to make sure none of the element has been sucked into your turbo.

 

It is a 93 lhd

 

I have all the stock rubber lines and hoses that came from the car with the original rats nest . Should I do a smoke test to see if I can find more vacuum leaks ?

 

I checked the filters when I took them off to change the line from the charge valve and they looked perfectly fine . I have only put about 7k miles since they have been put on

 

Smoke test would help. You might see some leakage from throttle body axles/turbo actuators.

 

Someone with more experience than me can comment on how to test the vacuum line system. (There are check valves, etc. that I think would make a smoke test difficult.)
The problem you may run into is that in going in to fix one hose, you may damage a different hose that's become brittle, which can lead to multiple dances with rat's nest. This is why it's recommended to proactively replace all of the rubber hoses with silicone replacements.

 

The act of changing the hoses may result in broken nipples on solenoids, which will then need to be replaced.

It the rats nest is original, old and very brittle, you will liikely end up refurbishing it all.

Otherwise, you will be dealing with a litany of breakdowns

Budget for:

1.. New vacuum hoses (factory replacements $750)
2. replacing solenoids: US$750
3. Replacing "Emissions Harness": US$1000.

 

one thing I don’t get is why it only starts having trouble during the middle of the day when it’s warmer then when at night when it’s cooler . At night time when the temp is around 60-70 degrees it runs perfectly with no hiccups or stutters compared to midday around 80-90 degrees . Could I just be holding in a lot of hot air in the bay ? It has a stock hood and I know this car generates a good amount of heat in the engine bay . Would a vented hood help with temp ?

also another question what modifications can I do on the stock ecu ? Can I change out the radiator and Intercooler ? Or wait till I get an ecu ?

 

Temperature affects the hoses.

So you can have a hose with a split in it that only opens when the hose has warmed up and flexes, and then closes again when it cools down (or visa versa). The hottest temperatures most of the hoses experience is when the car is parked after a drive in the middle of the day, when hot air from the turbos and cats rises to the top of the engine bay instead of being swept away by aerodynamics and fans ("heat soak").

The stock ECU should have no problem with an upgraded radiator and intercooler on an otherwise stock car.

 

I’ve seen people swap the radiator fans and motor from the rx8 , would this help keep temps in the bay down ? Temp gauge is reading fine but it’s getting to the point after a drive I open the hood and can barely even touch the prop. With these temps I’m sure more lines and hoses are going to start hardening soon enough even when if I were to swap them out .

 

Upgrading the radiator and, especially, installing a down-pipe will reduce underhood temps after the car is parked.

These are primary reliability mods.

If you haven't already, check out the 3rd gen FAQ sticky at:

http://www.rx7club.com/3rd-generatio...l-links-68640/

To see what updating the rat's nest involves, check out:

www.rx7.org/Robinette/hoses.htm

 

thank everyone for the help ! I’ll get around to checking all the vacuum lines and rats nest and also doing some reliability mods like radiator and all that . I’ll update you guys to see if I can find out what the problem is with the turbos !

 

I have a big costco box fan in the carport that I partk the car in front of, with the hood open, when I come home from a summer drive.

You could hook up a coolant temperature gauge to one of the spare bungs in the coolant filling neck and observe the heat soak with the engine off.

The ecu considers UIM intake air temperatures. The sensor is on the underside of the UIM. It might be about $100 to replace it, if you suspect the ecu is getting the wrong info.

The fuel pressure regulator is controlled by a solenoid. The ecu has a program were it causes the solenoid to close the FPR and thereby increase the fuel pressure to the injectors, when hot start needs assistance.

If there is a problem with the solenodi, or the vacuum hose to the FPR is leaking, the FPR will close prematurely thereby increasing the fuel pressure to the injectors contrary to what the ecu may be expecting.

If you don't have a second oil cooler from factory, there is room to add one on the right side opposite the LHS cooler. Might cost about $1000 to hook one up. Used piping and coolers can be found on-line. Or an aftermarket set-up may be better.

 

hey guys got around to start taking stuff off to start looking for leaks and I may have found the problem . Not sure how I didn’t see this before like when I changed the charge valve hose but I found a HUGE open crack in the stock intake coupling . Going to replace this and see if that fixes the issue .

 

Intake side hose crack shouldn't affect boost significantly unless it was blocking the intake. I'd keep looking for some other issue.

 

will do . Still checking to find anymore leaks or lines that may be cracked

 

These couplers can look ok on the car but still have a split in the middle that will open up under boost, and heat makes it worse. You may need to remove it and examine it carefully by hand to find out if it has a split.

 

Your air filter elements seem kinda dirty.

 

I am sure someone mentioned already but check the coupler that comes off the top of the turbos. Start there

then look around and examine all the couplers and hoses. Can always do a smoke test but start by looking around

 

I agree with Razer. You need to do a complete silicone vacuum hose replacement on the rats nest. The actuators rely on both the vacuum and the pressure side of the system for the twins to transition properly. Just take your time and use a razor to cut off the old hoses rather than pulling them off to prevent damaging any of the solenoid nipples which can be brittle. Label everything as you remove and once you can lift the rats nest out, simply replace each hose as you take one off to prevent getting mixed up. The silicone hoses remain pliable even in high heat. I did this years ago and my twins have been working great ever since. While I was in there replacing hoses, I also tested each of the solenoids with a Mityvac and a 12 volt power source just to make sure they were working properly. I think a standard 9 volt battery will work too for testing. If you find a bad one, you can get one at a lower cost here on the forum as opposed to buying solenoids from Mazda new.

 

Also, when doing a silicone hose job, be aware that some of the OEM hoses contain restrictor pills to control flow through them. Those should be salvaged and inserted into the silicone replacement.