jim-san

Although I’ve had my FC for over twenty-two years now I’m still new to the FD, so please bear with me if I ask what might be to some people a few obvious questions.

I did a boost test on my FD, not because I suspected that there was a problem, but because I wanted to check it out.

First, some background: my FD has 28k miles on it and is completely stock. As far as I know it’s never had any issues. I’ve driven it 3k of those 28k miles.
Boost is normal (when I do a boost test in 3rd gear, as described in this forum) until 4500 RPM, when it drops to zero boost and stays there until I back off on the accelerator. So it seems that the secondary turbo is not being engaged.

From what I’ve read on this forum and from the troubleshooting page on the autosportracetech site it might just be, to quote the troubleshooting page, that the “Hose from Primary Turbo Compressor to Wastegate and/or Turbo Pre-Control Actuators has popped off”.

So, I tried to trace the hoses to the wastegate and turbo pre-control actuator but it seems that these are very well hidden beneath various other hoses. The Mazda FSM for the FD doesn’t shed much light on how to get at the wastegate and turbo pre-control actuators either.

So, before I start doing anything dumb, could someone please tell me the best way to get at these actuators? I’ve searched the 3rd Gen site and can’t find anything that tells me this.

Thanks for any help you can provide!

gracer7-rx7

iTrader: (16)

Ha. Gotta love sequential troubleshooting. I'm having a similar issue as well.

You usually need to remove whatever is in the way in order to view and troubleshoot. Being a contortionist helps.

Start by removing the intake box and hoses and see if that is enough to see the hoses.

jim-san

Thanks gracer7, I suspected that that's what I would have to do, but I was hoping there might be a short-cut trick I could take!

I noticed that one of the vacuum hoses was starting to come off what I think is the air bypass valve. There was no clamp on it so I used a zip tie to tighten it up. I took a picture – could someone please confirm for me whether this is in fact the air bypass valve?

http://picasaweb.google.com/formerAL...48731819665650
http://picasaweb.google.com/formerAL...48739754297890

Right now the car is in its winter storage location. I might get one or two more days of dry weather to take the car out and do another boost test before winter really sets in, but if today’s rain turns to snow I might have to wait until next spring. One of the many downsides to living in the Great White North!

gracer7-rx7

iTrader: (16)

Yeah, I think that is the ABV which is connected to the primary turbo. The ABV and CRV are basically the same and most people refer to them simply as BOV generically when they can't remember which is which.

If you use some good silicon hose, you might not need the zip tie but it can't hurt.

dgeesaman

iTrader: (7)

The CRV is the one that runs all the way back close to the firewall. The CRV is one of the elements that prespools the secondary and it must be closed completely when you're above 4500 to achieve full boost.

The ABV is the basic blowoff valve that runs a shorter length. I think you've highlighted the ABV. Like the CRV, it must be fully closed to produce boost.

I suggest you look at the thin lines on both of those because the exhaust heat tends to harden them and cause them to crack apart or slip loose.

jim-san

Thanks for the info guys. It looks like I'll have to wait until spring to investigate this problem any further - we're snowed in here in Ottawa, and the RX-7 driving season seems to be over for another four months.

jim-san

It’s over six months later and I’m finally getting back to investigating what seems to be a boost problem on my ’93 FD. Winter slows things down here in the Great White North.

As I mentioned in my first post, my ’93 FD is completely stock, now with 29k miles on it. After doing the first boost test last November I found that the hose to the ABV seemed to be loose, so I put a zip tie on it. I replaced the zip tie with a quick-release clamp on the hose to the ABV when I took the car out of winter storage, thinking that that might be the culprit, and did another test. I made a video of the test and put it on YouTube:

http://www.youtube.com/watch?v=GEV6PF7BtE4

Although I said earlier that boost was normal, you can see from the video that it’s running at about 18 PSI at idle and at cruising speed. At above 4500 rpm it goes to zero or minus 5.

Could it be that I just have a cheap, inaccurate boost gauge? This was the only boost gauge that I could find in my area. It's a mechanical gauge.

Any additional insight that anyone can provide from watching the video of the boost test would be greatly appreciated, before I look into this further!

snivley whiplash

iTrader: (4)

gauge is showing vacuum at idle not boost, i see only 5psi boost in the vid. correct me if I am wrong but you have other issues my friend. A rotary never boosts at idle only under hard throttle

jim-san

It seems I've made a mistake in my reading of the boost gauge! Thanks for correcting me.

I'll fall back on the first statement that I made in my initial post to explain this rookie mistake!

Now, it seems I have some further investigation to do ...

snivley whiplash

iTrader: (4)

keep at it you will find the problem........

R.P.M.

iTrader: (3)

I have a customers FD in the shop right now that ran and drove totally fine but had no sec turbo, primary turbo would boost great then drop right off to 0 on the boost gauge.

He opted to go the Simplifed Seq route so after testing and inspecting all the vacum solinoids and check vavles, it turns out 5 of them either leaked or were stuck, luckily he had a spare Rats nest and I was able to get 4 solinoids that work correctly.
Also replacing all the vacum lines with new vacum hoses and zip-tied to ensure they dont pop off.

I'd be testing alllll the vacum solinoids

gracer7-rx7

iTrader: (16)

what he said


Where does the gauge get it's vacuum source from? Post a pic'

egauges.com is a good source for gauges.

jim-san

After all this time, I think I found the problem is in my right foot, not the car. During my boost test sessions I think I was using LOLA (little old lady acceleration), not WOT.

The last time I went out I was getting boost closer to 10 psi, but didn't have the video camera set up. Also, I was paying more attention to the road than the boost gauge.

I'll post a pic of my set up and a video of my next testing session, in a few days time.

Thanks for everyone's suggestions!

mikemikel

hey guys so the po of my 93 fd i guess tried to do a non sequential swap so he removed the pre turbo actuator, does anyone know where i can get one? i would like to get her running properly, thanks

newtgomez

It most definitely sounds like a vacuum nest issue. Maybe even quite possibly a boost leak and/or CRV problem. I'm going through the same problem with my FD and I'm praying once I get it back together that everything will be more jolly.

Happy holidays and good luck with troubleshooting!