supraturbo1987

iTrader: (4)

I am starting this thread to document my boost problem with the stock sequential system so that when it is fixed (and I update this thread) it could be a great one stop shop for many others whom I have noticed have such similar problems. First off, the car:

-1994 RX-7
-150k miles chassis
-40k miles reman
-20k miles twin turbos
-30k miles clutch
-BONE STOCK, still all emissions.
-original pre-cat and cat
-vacuum lines done at unknown miles, still very nice and flexible
-brand new fuel filter


The car first off would pass for 40k miles and is truly an 8.5/10 all around. The car starts, runs and drives great, with the exception of the turbos boosting properly. The symptoms since I bought the car 3 weeks ago are as follows:

-Idle vacuum is 16-17mmHg

-When going down a hill in 2nd and no gas, vacuum is 22-23mmHg

-after just cruising in 2nd, 3rd or 4th gear and punching it, boost goes to 12-13psi, then begins to drop off towards 5-6psi...there is no transition at 4500 that brings the boost back up.

-After boosting at 12-13, then changing gear and immediatly punching it again, boost will only go to 3-4psi and stay there till redline.

-When I let off and cruise for just a little bit, then punch it again, its back up to 12-13psi again and it repeats the cycle. Clearly, I don't have anything remotely close to a 10-8-10 pattern.

FAST FORWARD TO TODAY


I just got my 4 new VITON check valves from Dale Clark. I had time to install the 3 closest ones together which is one on the Pressure Chamber and 2 others next to each other both going under the throttle cable to the TB. (see pic below with black arrows pointing to the 3 check valves I replaced)

Keep in mind, before doing any of the check valves, the car boosted in 1st gear up to 13psi and then just bled off from there, never engaging the 2nd turbo. Then, if I shifted and went right into boost, it often times would only see 3-4psi.

I found that the check valve that connects to the Pressure Chamber had separated in half at one time and was being "held together" by electrical tape I replaced it with a new check valve (leaving the two others I eventually changed still stock because I wanted to test the car with just that valve replaced) and drove the car.

The car won't go anything over 3-4psi no matter what and in no matter what gear. I do feel like I am making progress though because I know that check valve was toast. I went on to replace the other two I mentioned above after the quick drive. I still have the last check valve that connects to the back of the Throttle Body to replace.

I am trying to figure out why replacing the 1 broken check valve on the Pressure Chamber caused the boost to go from 12-13 psi to now only hitting 3-4psi for the max boost I can achieve. I know I didn't create a new boost leak during the check valve replacement because I didn't remove a single pipe or hose during the process. So, I am now confused because the system should at least be boosting 6-7psi at the least case scenario, barring no boost leak. I will be installing the 4th check valve and working to figure the problem from there. More to come, and advice appreciated! Also, I checked the Pressure Chamber and it is NOT leaking it appears.

Trev

goalguy02

iTrader: (3)

I'm not sure if you need your emissions equipment but what I would recommend if you don't is:
-Block off as many emissions related things as possible
-Get rid of double throttle
-Get a power fc
-go through vacuum lines and switch to a simplified sequential setup.

Its nice to get rid of any bad solenoids and verify all your vacuum lines are correct. I went this route and now have a perfectly working transition. If the mods aren't feasible then maybe start by redoing all the vacuum lines in the ratsnest. A lot of work if you haven't ever done it but you will learn about the system and hopefully fix whatever is causing it.

Goodluck.

DaleClark

iTrader: (55)

I'm wondering if possibly the turbo control door is open now or something instead of being closed. Also, it's worth checking the coupler off the Y-pipe to make sure it's not split and leaking. That's a VERY common problem and getting in there to do the check valves could have disturbed it.

Dale

adam c

iTrader: (2)

Is it possible that you installed the check valve in the wrong direction?

Ruler_Mark

iTrader: (16)

Check the vacuum tank lines.

NVMYRX-7

iTrader: (24)

TERRIBLE ADVICE, this is what you do when you are too lazy to read or fix an issue. The only GOOD advice was -Get a power fc.

supraturbo1987

iTrader: (4)

RESPONSES:

goalguy02:

Thank you for the input, I will be going with a PFC sooner than later, however, I am making sure to FIX everything properly before moving to more mods. I figure if this car drove perfect with ALL of the emissions before (like when it was new ) I can get it to do that again. Thank you!

Dale:

I know for certain that I didn't touch the Y pipe coupler, however, I will be fully inspecting it in the coming days along with the rest of the IC piping. Thank you!

Adam C:

I thought the same thing and so I went back in right away and triple checked that the one on the Pressure Chamber was arrowed towards the Pressure chamber and the 2 check valves going under the Throttle cable mount are arrowed towards the UIM.

Ruler_Mark: Haven't checked that yet, but will!

Trev

supraturbo1987

iTrader: (4)

So I had time tonight to get into the intake and IC piping. I wasn't super excited because I was hoping to find a crazy, major obvious reason as to why I can only achieve 3-4 psi of boost. Well, the Y pipe coupler, although hardened, was not split or cracked. Everything else checked out with the exception of the TOP IC accordian hose going from the IC to the intake elbow that connects to the TB. I did find it was cracked, however, it is cracked right about where the hose clamp sits on the ENGINE side...however, the crack is overlapping the piping, so I am sure it is somewhat air tight (I mean that the crack isn't over the middle of the pipe or anything, but rather right where the accordian part starts. So I am not sure if it is leaking boost, but it can't help. Refer to the pic below to see what I am talking about...

It is getting late now, so I put cloths in all openings and will resume another day. After examining the vac lines, everything is properly routed and secured. I was really hoping for some super obvious boost leak (and maybe I found one) but I am not sure. I am going to install my DP since everything is pulled off the car intake wise and I have a shot at it.

I will be replacing the Y pipe coupler and the other one just like it (can't remember off hand where it is, but there are two) and the hose from the CRV to the intake as well as it cracked when pulling it off, and of course this upper accordian hose.

Trev

adam c

iTrader: (2)

Might be a good time to get an efini y pipe.

goalguy02

iTrader: (3)

Not sure how simplifying the rats nest and replacing vacuum lines is bad advice? In my opinion I would want to ensure I'm starting with a good base and move from there. Especially if he doesn't know what condition his solenoids are in.

Where was your advice posted?

goalguy02

iTrader: (3)

If the car was boosting perfectly before than no I would not remove emissions related items. I didn't see in your original post where you said the car boosted and transitioned properly. I only read that you had the car for a short time and it would never transition, only bleed off boost.

cr-rex

iTrader: (114)

on/off topic kind of, but...

the simplified sequential set up.... whats the difference performance wise with that set up as apposed to the stock set up?

supraturbo1987

iTrader: (4)

ADAM C:

I have strongly considered this as it would be a much better connection, allbeit the extra flow characteristics are minimal. I really think I can save myself $100.00 and buy a new coupler at my dealership considering it worked for so many years the first round. I will still consider it, so thank you!


GOALGUY02:

Thanks again for the input. I haven't had anything close to a perfect, or ideal stock boost pattern, so I will continue to try and work with the OEM setup. The further I tear into this, the less I want to put all of this stuff back together however

Trev

supraturbo1987

iTrader: (4)

Also, would anyone argue that the crack in the upper IC accordian hose in the pic wouldn't cause a boost leak because the area where it is cracked since it is overlapping the intake elbow?

Trev

DaleClark

iTrader: (55)

Boost will find a way, if you find ANY splits like that, fix it. You'd be surprised where boost can find a way out.

If the Y-pipe coupler is rock-hard I'd probably replace it as well, it WILL fail at some point. You can either replace it with a short section of silicone or a new OEM coupler. Or get the '96+ JDM Y-pipe.

Another common problem is the 3/4" or so hoses going to the charge relief valve and blow-off valve. They get super hard and don't seal well.

Dale

supraturbo1987

iTrader: (4)

I am ordering a new upper IC pipe today. I love OEM parts for cost

Definitely ordering a new one today as well as the same coupler that is on the other side of that cross over pipe.

I will replace that hose too. The longer one on the other side of the CRV was hard and took the jaws of life to remove...it broke in process

I figure if I can get all of these hoses replaced and verify it is all up to par, then I will be able to eliminate boost leaks as the problem and focus on the solenoids and actuators.

Trev

supraturbo1987

iTrader: (4)

Well, I ordered 7 new hoses ranging from the broken accordion to couplers to other misc parts. 300 bucks cost. Brutal.

Curtisc63

iTrader: (1)

Bump for an update!

dblboinger

iTrader: (3)

I'm learning myself that the best way to learn about the turbo control system is to have a problem. The good thing is one you start reading about it, it doesn't seem all that complicated. Just a lot happening, particularly at 4500 rpm.

supraturbo1987

iTrader: (4)

I have been very busy, so I apologize for taking time before posting this. I have installed the Downpipe and New O2 sensor, and also have installed all my new OEM hoses (y pipe coupler, CRV/ABV hoses, intake hoses). I also just got my HKS IC hardpipes the other day as well (I decided to go this route instead of new OEM IC accordian upper and lower pipes because those would have been about 350.00 *YIKES* and I got these pipes for 105.00 shipped. I was about to install them and the couplers that I bought online were 2.5" that got sent to me, not 2.75" like I need. As soon as those couplers arrive (should be today or tomorrow via USPS) I will be driving the car on Saturday night to test boost. The changes that will have been made are:

Downpipe
New O2 Sensor
New Y pipe coupler (couldn't FIND any cracks, but was rock solid hard and I am sure not well sealed)
IC hard pipes to replace the ones that I DID find a big chunk out of

I really think that the IC pipes and Y pipe coupler is going to help quite a bit. I still have the stock Catback and Intake with a new filter element.

More to come...

Trev

txfdr2

iTrader: (5)

I sent a pm, but will add to it here...

There are multiple vacuum lines around the y-pipe, turbos, etc... And 3 or 4 going in the turbo side of the LIM... Replace those, I bet they are bad.

If necessary, disable the turbo control solenoids, to see if you get a 8-6-8 pattern (or 7-5-7ish).

Flat_Boostin'

iTrader: (3)

I'm having a similar problem. Do you mean the twin control solenoids? Or the control solenoid tucked right underneath the UIM?

indio84

iTrader: (7)

Would be interesting to see if you fix the problem. a friend of mine has the same problem.

Mrmatt3465

iTrader: (10)

The wastegate and precontrol solenoids are the ones he speaks of. The two green ones on the front side of your UIM. With those electrically unplugged you should get a 7-5-7 pattern.

txfdr2

iTrader: (5)

the 2 that bolt to the UIM.

But i'd focus on a -complete- hose job first. Replace all of it. You will likely find that whoever did it missed some of them and possibly routed some of them wrong.