My personal sequential boost thread, from broke to hopefully fixed
 

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

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.

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

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

Check the vacuum tank lines.

TERRIBLE ADVICE:rant:, 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.

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

Update
 

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

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

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?

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.

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?

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

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

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

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

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

Bump for an update!

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.

Small update!
 

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

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).

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

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

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.

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.

I realize you're getting the stock 'y' pipe coupler for cost, but personally I would re-consider getting an efini 'Y'. Mazda realized the engineering mistake and as you've already mentioned, it flows better. How much? Not sure...probably not much. But it's definitely positive and a permanent fix for potential leaks at that coupler. Over the long term maybe even slightly easier on your turbos. It's also OEM so you don't have to worry about fitment or using sub-par quality aftermarket.

It's rare but you might also check for any leaks in your pressure chamber and vacuum chambers.

My .02

Jim,

Great to hear from you and thanks for the input! I really agree with you, and will get an Efini Y pipe soon. That hose coupler was 20-something bucks and quickly available for me, so I went that route. I do have all intentions of replacing it with an Efini.

BTW, your engine bay is looking quite amazing. I am very envious :) See you around this year!

Trev

Another update...
 

Okay, so I started and drove the car for the first time since replacing all OEM hoses associated with the stock intake box and the vac lines also associated with the crv and abv, and also with the new HKS Intercooler hardpipes and new hoses couplers to connect them. This is also the first drive since I installed my car's first mod, the Downpipe and new O2 sensor.

First off, the pre-cat was 150k miles old, as well as the O2 sensor. I must say, the car idled and accelerated MUCH more smoothly. MUCH MORE. I am still experiencing only 4-5 PSI of boost however that begins to drop off between 4000-4500 RPMS. The boost is much smoother feeling, although I still have problems to solve.

I guess from all of my reading, the car SHOULD boost at least 7 with no boost leaks

I have none at all that I can find, although I noticed that the VAC line going from the PURGE CONTROL SOLENOID is VERY loosely connected to its nipple which is under the UIM where it joins the throttle body...the VAC line is too big of an Inner Diameter for the nipple it is supposed to fit on...it slides on and off with no effort, but doesn't disconnect. With the car on and idling I can here a whistle from that line and if I move the vac line in and out on the nipple I can make the whistle non-existent.

So, I am quite confused as to why I can only achieve a max of 4-5 psi in all gears and then have it bleed between 4000 and 4500 rpms...

I am enjoying doing this one thing at a time though so hopefully I can pinpoint the exact cause...

Trev

UPDATE!

I removed my UIM today to inspect the vacuum lines that have already been replaced before I bought the car, and to test the solenoids and the turbo control and WG control solenoids. Well, there was a vac line that connects to the second solenoid from the firewall, Relief 1, that wasn't even connected. Also, after checking all the solenoids, I found solenoid H (on the colored diagram from my first post) the Charge Relief Solenoid to be dead. No clicking, no functioning. I reconnected the hose on the relief 1 solenoid and will now be getting another Charge Relief Solenoid to replace my dead one.

Are any of these two issues a possible cause for my issues? After I replace that solenoid, I will button it back up and check the WG actuators and lines to them under the intake box. I was to make sure there are pills in the lines.

Trev

Glad we could hopefully pin-point a possible cause on both the UN-attached vac hose and the solenoid. Let me know when you want help re-assembling. I always forgot a sensor or vac line when hooking everything back up.

Seda

Thanks man! I already have a new charge relief solenoid on the way (2 for the price of 1 from Fritz Flynn) and I will get some more vacuum hose for that solenoid and also for the oil pedestal line. I think I just want to get this car up and running, so I am not going to send the uim to get polished and run the risk of having to recalibrate the TPS and such.

Trev

A boost leak pressure test may help you find any remaining little stupid leaks. Fighter's Garage used to sell a pressure testing tool for an FD with stock twins. It should just be some PVC type of thing you stick in the turbo inlet pipes, one of which is tapped for an air fitting. This site sells them for the 300zx: www.boostpro.net/prodtester.html

I have not done it on a car with stock twins before but that would be a method to track down any other nagging problems.

It's hard to say what a dead charge relief solenoid would do because we don't know exactly what's going on with your turbo system. The secondary turbo would go into surge briefly without the charge relief valve working, but I think that's the least of your worries, and there is reason to believe that the stock turbos can tolerate some surge. If the charge relief solenoid had been hooked up incorrectly, it is possible that vacuum could have been continuously applied to the charge relief valve, making eseentially a huge boost leak. The charge relief valve is basically a blowoff valve controlled by the ECU through a vacuum solenoid.

Also, it doesn't surprise me that installing a downpipe made a noticeable difference. These cats weren't built to last, not by today's standards. Only modern vehicles with the strictest emissions certification have cats meant to last 150k.

Yes, I believe it is the least of my worries, but I would think that it could cause transitionary issues between primary and secondary. Not saying it fixes my issue, because I have only 4-5psi max to redline on the primary, but it may at least be an issue as to why I have no transition. Thanks!

Trev

Just ordered my Black Silcone Vacuum hose kit...doing the whole kit n' kaboodle while checking all of the solenoids. Need to get all of these basics perfectly right so I can really start to dial in and get this issue fixed. More to come...

Trev

Progress update
 

I am diving deeper and deeper into this issue and basically I seem to be on a mission to replace as many things as possible (not always by choice) as I find things either broken or if I break them. I did find that the VAC hose that goes from the TOP nipple of the Pressure Regulator Solenoid (the FIRST solenoid from the firewall in the rat's nest) was completely separated where it connects to the LIM by the fuel rail...I am sure that wasn't helping my cause :)

I have removed so much stuff I feel like I am doing a rebuild. Alternator, oil pedestal, air pump etc, all intake items, ACV, etc. I did notice that the line to the VACUUM chamber is rock hard and slides EASILY on and off the nipple, clearly not sealed. Of course, I accidently broke that VACUUM chamber nipple when removing the pedestal, so I need to remove some more items to remove that and replace it. Here is what I am looking at purchasing now while I have all of this opened up:

-NEW PRESSURE CHAMBER
-NEW VACUUM CHAMBER
-ALL NEW SOLENOIDS IN THE RATS NEST (I just hate having to replace these with other used ones that I don't know how much life is left on them)
-STAINLESS STEEL OMP LINES
-VARIOUS COOLANT LINES

Somehow, one of the two wires on my Altnernator plug (grey square one) broke right at the connector, so I need to find another plug I can solder on.

I am VERY tempted to buy an all new engine wiring harness...

Until next time...

Trev

If the line to the vacuum tank was not fitting well, that very well could be part of the problem. You do need that vacuum tank.

Unless the OMP lines are broken, don't replace them. It is a BITCH to do the OMP lines in the car, they are secured under the water pump housing. I'm also not a fan of the stainless OMP lines - braided stainless is abrasive and can cause other problems. Also, they aren't molded to fit like the stock lines. The stock lines work VERY well and last a VERY long time. Most likely the stainless lines will look like terrible in 100,000 miles.

The alternator connector is available online (Google around) or at a junkyard for free/cheap.

I wouldn't purchase all NEW solenoids, I'd get good low-mileage ones. Or get ones off an FC, they see a lot less heat and are the same exact thing.

Dale

Thanks for the tips Dale. I am going to hold off on the OMP lines considering the old adage, if it ain't broken, don't fix it. Fritz came through for me again with a whole rats nest and all solenoids with only 8k miles on them and low mile pressure and vacuum tanks as well as the alternator connector for a crazy deal. The silicone kit will be here soon and I will be getting things lined up to put everything back together.

Trev

Well I do know about the Efini 'Y' pipe, and its influence can be significant, particularly at higher airflows. According to Mr. Flow Bench, the Efini combination is worth about 15-->16% more flow at a constant pressure -or- a constant airflow at about 32-->35% less pressure. About half the improvement is realized in the Y pipe; the balance in found in the top piece.

To further quantify this, lets say your setup flows 40#/minute of air; this could represent a car of 300 or so RWHP. The test results suggest an additional 6#/min could move through this portion of the tract with no additional pressure required [from the turbos] to push it. This is much more efficient and may represent a noticeable improvement for you guys that already have a low restriction intake tract, IC, plumbing, etc., and who are trying to extract all the potential from your setup. *Note that I am not saying that it will give you 6#/min more flow just by bolting it on.* It will improve your boost/flow potential, however.

And while on the subject of Y pipes, here's a note for those of you who have tried to divide the Y pipe internally: Not a good idea, it will generally result in a loss of flow. I know this because I have built and tested some variants.

And of course the Efini pipe gets rid of that problematic coupler....

^Thanks. A bit better than I would have expected. I know for the cost and relative ease of installation it was one of the better mods I did.

Great info both Speed of Light and Jim. Considering I am basically down to the block, I am sure I will make this upgrade!

Trev

Lots of parts arriving. I got a new pressure and vacuum chamber (slightly used) and another rats nest with all solenoids that have only 8k proven miles on them! Also, new drive belts, all new metal gaskets, FC thermoswitch, new oem thermostat and a few other maintenance items.
Will be getting things put back together this week.

Trev

Good work, hopefully all that sorts your problem.
Iv just finished a mission into the rats nest myself this past weekend.
I had quite a few hoses that had gone hard and didnt really grip the solenoid properly.
I also had a worm drive hose clamp on the intercooler piping that was broken and could only be done up so tight, which wasent tight enough - resulting in a boost leak.
Car is more responsive and faster than ever! hurahh!
I was also getting idle problems, car was idling low at about 500rpm.
Idle is solid and up to just over 1k rpm now.
Before my hose job i was going to adjust my idle speed up, now ill adjust it down.
Hopefully its not a vacuum leak :nod: Either way car is alot faster!
EDIT: ah and i used to get alot of backfiring when changing gears, havent had a single backfire since the hose job.

Thanks for sharing the success story! It's a great inspiration to make it happen and keep rolling.

Trev

Progress report
 

Okay, I am on the mend here, getting everything put back together. First off, I really can't even understand how my car ran as well as it did with as many completely broken off solenoid nipples and broken in half vacuum lines I have found!! The rats nest has new lines and is back in the car along with the ACV, FC thermoswitch, new vacuum chamber and new (8k miles on them) solenoids. I am getting excited to get it wrapped up and take it for a drive. More to come as I get further. I am 110% sure this vacuum line job WILL fix my issues...

Trev

As a buddy of mine used to say, "That may not be the problem, but it sure as hell wasn't helping things".

Hopefully you'll have some good updates soon!

Dale

Read this, and test accordingly:

http://www.autosportracetech.com/RX-...leshooting.htm
http://rx7.voodoobox.net/howto/solen...oid_check.html

:-) neil

New thermostat installed, everything else all dOne basically. Only thing left is to install new WG and PC lines with pills (got new ones...mine were missing...again, not helping the situation). I will do this tonight! Update tomorrow as it is raining and the street is wet!

Trev

WE HAVE BOOST!! Just too much...
 

Okay, we'll the surgery was a success. The car fired right up and idled/drove very nicely. Keep in mind the car only has IC hard pipes and a DP. The only thing that I am dealing with now Is the boost pattern. It was easiest to really measure a second gear pull tonight, and it was a 14-6-10. I did replace all vacuum lines including new OEM WG and turbo pre control lines with new boost pills built in. I guess I am excited that the secondary is 10, but I need to scale back the primary and bring that transition up. Right now, an 8 psi swing from primary to transition doesn't feel nice and smooth :)

So, I am pleased to say that after the vacuum line job and newer solenoids, I am finally in the ball park here. I will continue to update this thread as I resolve the primary and transition issue.

Trev

Knock sensor
 

So, I took a look at the vac lines going to the turbo actuator under the turbos and sure enough I forgot to replace both of those lines and one was popped off. I replaced both lines and went for a drive. It seems smoother, but I am still getting 14-15 on primary, then 6-7 transition then 10-11 on secondary (this time that holds, no bleed off). However, I must have gotten too spirited because I tripped the knock sensor during boost and got a code 05 and it went limp all the way home. I reset the ecu to get rid of the code, but I am still stuck with my primary boosting too high and my transition being too low and something causing my KS to trip...

Trev

Trev,
It appears you've made some good progress! Even the most perfect of rx7s always seem to have hidden issues. I picked up my 93 touring with 38k on it. Upon installation of my boost gauge I discovered I was only hitting 5 psi in first and a every-now-and-then transition in second. Third had a slow transition. As I was tearing into my engine bay to replace my vacuum lines and install Azeknightz solenoid rack, I ended up replacing a lot of things! I wish I could have seen your thread a few days ago and I would have suggested testing your omp nozzles while you were there. Both of mine had failed check valves. After buttoning up including the installation of a nice 3" Pettit downpipe, I got full boost an transition in all gears. I do however now have a 13-8-10 boost pattern. I attribute the spike to the 3" downpipe. My plan to quell that spike is the dual MBC set up as suggested by I believe it was Damien. You can find the link in the FAQ. I believe dual MBCs will trump a single ebc in terms of full control over transition. I'm a set it and forget it kind of guy :).

Good luck to you!