RX7 FD boost issues

[SuperVM]

I've got a 1993 FD RX7 with boost issues. The car has been remapped and is running a Power FC. The primary turbo is generating about 10 PSI of boost, but this falls to around 5 at 4.5k RPM and then 0 by 5k RPM. I suspect a "rats' nest" issue and have already replaced one split hose (the blue one in the picture). While digging around I've found another two connections that look to be missing and also this:



It appears to me that this is what is left of a check valve. Before I go ripping the inlet manifold off and ordering a bunch of hose and check valves (£30 a piece from Mazda), is it possible this has been done with the sequential turbo vacuum simplification modification in mind or is this always an essential connection? Also, does anyone know of a better source of replacement valves? I've seen some people get them from a chap in the US, but I'd rather not wait tht long should I need them.

Thanks to anyone who can provide a bit of help.

[SuperVM]

fesuvious said:

what were the symptoms that you cured by replacing that pipe?

None, it isn't any better with the pipe replaced. I've taken the pressure box off and found the other half of the check valve is there and connected to its line, though it's difficult to see how it is possible for the valve to come apart. I've also confirmed that my car is running the simplified rats' nest and all the diagrams I've seen for this configuration suggest that this line should still be connected with the check valve in place. So, I've ordered another valve and hope it will do the trick, if not then I'll have a look at your suggestion. Here's how it looks under the pressure box:

[BrettMRC]

In these situations you are generally best off replacing all the age/heat hardened elements of the rats nest, do it all in one hit and replace anything that looks suspect.

An awful lot of FD's have boost issues caused by age related wear in the turbo control system.

[SuperVM]

BrettMRC said:

In these situations you are generally best off replacing all the age/heat hardened elements of the rats nest, do it all in one hit and replace anything that looks suspect.

An awful lot of FD's have boost issues caused by age related wear in the turbo control system.

I am beginning to think that might be best, especially as when I turned one of the hoses to have a look at it, it snapped.

[SuperVM]

fesuvious said:

How difficult is manifold removal etc etc.

I have all the vac tubing I could ever need already.....therefore I'm very keen to get into the 'rats nest' and replace them all.

This far though I have only had a cursory glance over that area whilst I was stripping the cooler and intake to make sure everything was ticketty boo in that area.

There are a few guides available that even include pictures. The second post in this thread has a few links:

http://www.rx7club.com/showthread.php?t=831971

[GT Kodiak]

Got a long list of things to do on my Rex but for the cost of silicone tubing you could replace all your tubing and have some peace of mind if they're mostly stock pipes at the moment.

Admittedly on a turbo'd rex that still an expensive job due to the ammount of hoses but... hey ho...

[SuperVM]

GT Kodiak said:

Got a long list of things to do on my Rex but for the cost of silicone tubing you could replace all your tubing and have some peace of mind if they're mostly stock pipes at the moment.

Admittedly on a turbo'd rex that still an expensive job due to the ammount of hoses but... hey ho...

I actually have loads left over from a previous project, so it won't cost me too much. :-) I'm also running the simplified sequential setup, so there's not as much hose to replace. I'll probably do it at some point, but I've hardly had the car any length of time and just want to drive it.

[SuperVM]

I've replaced the check valve with one from Pets at Home for an aquarium air pump and the second turbo is now spooling. :-)

[probedb]

SuperVM said:

I've replaced the check valve with one from Pets at Home for an aquarium air pump and the second turbo is now spooling. :-)

Good times. Now remember to put your foot down (when allowed obviously ), someone on fd:uk had a curious case of never having gone past about 5500K!!

[SuperVM]

probedb said:

Good times. Now remember to put your foot down (when allowed obviously ), someone on fd:uk had a curious case of never having gone past about 5500K!!

I've hit the limiter a couple of times, though it seems to be coming in a bit early. It would help if the previous owner had installed a steering wheel that allowed me to actually see the gauges. That's the next thing I'll be doing, though I can't believe the RX7 doesn't have an adjustable steering column.

[probedb]

SuperVM said:

I've hit the limiter a couple of times, though it seems to be coming in a bit early. It would help if the previous owner had installed a steering wheel that allowed me to actually see the gauges. That's the next thing I'll be doing, though I can't believe the RX7 doesn't have an adjustable steering column.

Did anything but really expensive cars have them in 1992?

[SuperVM]

probedb said:

Did anything but really expensive cars have them in 1992?

I don't think they were particularly cheap anyway. Perhaps you're right, but given the lack of seat adjustability, it seems ridiculous.

[ezakimak]

Re the steering wheel issue

having just test driven one i noticed this issue as well.

im wondering if it would be possible to space the steering column up a little bit on its mounts where it bolts to the cross car beam under the dash.

need to go and have another look to see if there is enough space to get something in there and get some movement.

Ryan

[SuperVM]

A lot of people say that a 350mm steering wheel should be large enough to allow the driver to see all the instrumentation. This may well be true if the wheel is flat, but mine is dished and I still can't see the top of the speedo or rev counter unless I virtually lie down while driving the car. I've got my car in a few bits at the moment while I'm adding some gauges to the centre console, so I can have a look at spacing the steering column up a bit for you.

[probedb]

It all depends on your height and seating position. A 330mm for me was the same as your current wheel is for you, a 350mm flat wheel is great but I can't see my indicator lights