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Power FC - Can't get boost control working with non-sequential setup.
This was originally posted in the Power FC forum but didn't get any responses. I've closed that thread over there (mods please delete it if needed) and opened it over here since this section gets more traction. Any ideas, please feel free to let me know!
Here's the details:
I completed a "rich man's" non-sequential conversion using my old 93 turbos and have retained the stock wastegate/pre-control solenoids.
In my Power-FC I still have sequential turbo control enabled.
The factory map sensor vacuum hose is hooked up to the intake via the port on the left side (which I believe is the factory routing).
I have the restrictor pill installed in the hose between the turbo and the "left" nipple on the wastegate actuator.
I ran a hose from the "right" nipple on the wastegate actuator to the top port of the wastegate solenoid.
I left the other port of the wastegate solenoid uncapped.
I currently have the connector that is BLUE with a YELLOW stripe connected to th WG solenoid (although I have tried the other connector as well just in case I got them messed up).
In my PFC under boost, I have tried everything from 0.50 to 0.75 kg/cm2 and 24 to 40% duty cycle with no noticeable differences noted.
What I am experiencing is that regardless of what I set the pressure and duty cycle settings to, the car seems to boost to 0.28 regardless. The PFC seems to have zero effect on the boost control. What am I doing wrong here? I have borrowed a picture below (THIS IS NOT MY CAR/SETUP just using that picture to illustrate the hoses in question) to show the hose I have the restrictor pill installed in and the port I am using for the wastegate solenoid.
By the way guys, something that occurred to me while thinking about this issue over the holiday weekend. My Power FC is only showing me hitting a max boost of 0.28 kg/cm2. Converted to PSI that works out to 4. I thought the wastegate spring pressure alone was around 7 PSI. Sooo... "something ain't right here" and I'm not exactly sure what. It could certainly be the Power FC that is reading incorrectly but wouldn't that mean my MAP sensor was faulty? If that were the case, I'd certainly feel it in almost all driving conditions.
I'm stumped here. My next thought is to hookup a manual boost controller and see what happens. Also, for those who haven't followed along with my journey with this car, I am NOT hunting power at the moment. I am simply trying to get the car boosting back at the stock levels so that I can verify all other aspects of the car are functioning in a "relatively" stock condition. I brought the car back from the dead so I have no idea what a "stock" RX7 feels like either unfortunately. A lot working against me here, but I'll get it figured out. Any ideas pop out right off the bat?
That boost is low enough that I would be suspicious of a boost leak. On just spring wastegate pressure you should be able to get 7psi.
Also with the non-sequential the spool without the boost control is going to be SUPER laggy. Probably need to get it over 4 or 5,000 RPM to really see what boost you are hitting. Just going off a throttle stab at low RPM you probably won't build max boost.
That boost is low enough that I would be suspicious of a boost leak. On just spring wastegate pressure you should be able to get 7psi.
Also with the non-sequential the spool without the boost control is going to be SUPER laggy. Probably need to get it over 4 or 5,000 RPM to really see what boost you are hitting. Just going off a throttle stab at low RPM you probably won't build max boost.
Any reason you went non-sequential?
Dale
Hey Dale,
Thanks for the reply sir! I almost replied back again asking what everyone thought about a boost leak as the potential culprit. I have double-checked all the hoses and everything appears to be good to go, but I haven't actually done a proper leak check with a kit. That might be a much better idea then the manual boost controller as a next step. I have already done a lot of the other basic troubleshooting steps such as using the other solenoid (precontrol) in case the wastegate solenoid was bad.
As for the NS conversion, it was a decision made to get the car in a running state. In my build thread I go over all the details, but long story short is the car sat for 8 years and had a seized motor and used to be an automatic. I bought a full 99 spec motor/trans and did the conversion. Along the way I ran into countless problems and hurdles (including an injury) and the goal was to simply get the car running correctly in the simplest form and THEN go back and install some of the more headache inducing things like the sequential system. To that end, I did a full rich man's NS conversion on the 93 turbos with the intent of restoring the sequential system with the 99 spec turbos once I validated the car was running well, could turn, stop, etc. etc. I need to update my build thread as I stopped after posting tons of pics of the NS conversion, but it has since hit the road plenty of times.
The NS system isn't bad honestly, when testing I routinely rev it out to over 5k to check for max boost pressure and it definitely feels like it is hitting the tiny peak of 4 PSI at 3800 or below. Although 4 PSI is nothing to compare to soooo : ) I love how simple the system is like this, but my ultimate goal is to restore the car to a simplified sequential setup utilizing the 99 spec turbos. I do not not intend to do that until making the NS system work at factory boost though so I can check on all other fueling requirements, injector duty cycles, AFRs, etc. etc.
I'll look into the steps to do a proper boost leak check on the car and report back what I find!
Dumb question but youre putting the engine under decent load when trying to spool the turbos right.
Correct, I usually wind it out to 7k on a slight incline to test. I have a strong suspicion the aftermarket (knock off) Greddy Type-S BOV is what is causing the problem at this point. I intend to swap it out with the factory valve when I get home this evening and retest. If it makes no difference, I found a nice $50 boost leak testing kit on Amazon and will purchase that and pressurize the system to check for leaks.
No, that is not my setup, I used that picture to illustrate the lines I was speaking of. Here's a few pictures of the setup from my car as it sits right now for testing:
I got home last night and swapped the knock off BOV back with the stock ABV valve and retested. It made no difference at all unfortunately. My plan at the moment is to purchase this boost leak tester to check for leaks:
. I plan to hook it up to the compression tube and slowly pressurize the system while using soapy water to check for any leaks. If that passes, I'll have to give a manual boost controller a try. One thing at a time I suppose.
That boost is really low. Is your WG door attached to the actuator rod and is it pre-tensioned closed?
Hmm, I think you might have solved this! As mentioned above, I did a NS conversion and had to take the WG off to do all that. Too big of a coincidence for that not to have something to do with it I would imagine. Here's a bunch of pics and stuff: https://www.rx7club.com/build-thread...1095009/page3/. I honestly can't remember at this point if I tensioned it enough when reinstalling. How would I know for sure? Is there a specific measurement of force or is this just one of those things you kind of feel out. I will check the tension tonight and make sure it is all still connected properly. Thanks!
With the door closed, the hole on the wastegate rod should cover half of the "peg" on the door arm. So, you have to pull the rod out just like 1/4" to get it on the peg.
One of the arms (can't remember which) is adjustable but many times you can't adjust it since it's rusted solid. With a vice, heat, a wire brush, and PB Blaster you may be able to get it to move. You can also use washers or something like that to shim the actuator out a little bit.
I noticed in the pictures a few things -
- The Y-pipe coupler is a stock coupler. Many times those are baked hard or torn, #1 cause for a boost leak. It also has the stock hose clamps on it which may be stripped out or not tightening down fully. You can replace it with a 2.75" ID silicone coupler, those are commonly available.
- The throttle body elbow has a rubber cap on the large nipple pointing at the firewall, this is from removing the AWS system (or, if a JDM car, it's capped since it never had it). That rubber cap doesn't look like it has a hose clamp. It may not be leaking now but if you make some boost that sucker will be coming off.
- The vacuum line and cap on the compressor outlet don't have a clamp, they need some sort of clamp, even a zip tie, to make sure they stay on good. Also, many vacuum caps won't take the heat - this is true of most caps you get at the local parts store. EPDM rubber caps from McMaster-Carr is a good way to go, I've been using them for years and they can take the heat and come in a variety of sizes.
With non-sequential you should be able to get 7psi of boost with just a line going from the compressor nipple to the wastegate. You're at the most basic setup possible at that point, if you're not getting there you either have a boost leak, exhaust restriction, major problem with the turbos (like chewed up turbine wheels), or the engine isn't running right (old spark plugs, plug wires hooked up wrong, etc.).
With the door closed, the hole on the wastegate rod should cover half of the "peg" on the door arm. So, you have to pull the rod out just like 1/4" to get it on the peg.
One of the arms (can't remember which) is adjustable but many times you can't adjust it since it's rusted solid. With a vice, heat, a wire brush, and PB Blaster you may be able to get it to move. You can also use washers or something like that to shim the actuator out a little bit.
I noticed in the pictures a few things -
- The Y-pipe coupler is a stock coupler. Many times those are baked hard or torn, #1 cause for a boost leak. It also has the stock hose clamps on it which may be stripped out or not tightening down fully. You can replace it with a 2.75" ID silicone coupler, those are commonly available.
- The throttle body elbow has a rubber cap on the large nipple pointing at the firewall, this is from removing the AWS system (or, if a JDM car, it's capped since it never had it). That rubber cap doesn't look like it has a hose clamp. It may not be leaking now but if you make some boost that sucker will be coming off.
- The vacuum line and cap on the compressor outlet don't have a clamp, they need some sort of clamp, even a zip tie, to make sure they stay on good. Also, many vacuum caps won't take the heat - this is true of most caps you get at the local parts store. EPDM rubber caps from McMaster-Carr is a good way to go, I've been using them for years and they can take the heat and come in a variety of sizes.
With non-sequential you should be able to get 7psi of boost with just a line going from the compressor nipple to the wastegate. You're at the most basic setup possible at that point, if you're not getting there you either have a boost leak, exhaust restriction, major problem with the turbos (like chewed up turbine wheels), or the engine isn't running right (old spark plugs, plug wires hooked up wrong, etc.).
Dale
This is awesome and I have multiple things to look at now/fix. I will get all this stuff checked out/resolved and report back what I find. Thanks so much guys!
Charge relief valve still there or is it capped off? Don't see it in your pictures.
CRV is gone as part of the NS conversion. I'll be heading home in a minute and should be able to work my way down some of the list of items to look at. I think the wastegate door is definitely not tensioned enough as Alex & Dale mentioned. That certainly sounds like something dumb I'd do : ) Keep the ideas coming though guys and thanks again for your help, this has been driving me nuts!
Bringing this guy back up from the dead to report the results of investigating the wastegate actuator arm. Unfortunately, it appears as though that was definitely tensioned correctly (door was tensioned completely shut) so my boost problem is not related to that from what I can tell. Dave has given me some great tips on common things to check for and I'm sure one of those is in fact the culprit. I've got the Efini Y pipe I can use off my 99 turbos, but I'm thinking I'd like to do a proper boost leak test first to really narrow down which issue mentioned is happening here.
Question... What size boost leak tester should I buy to perform a proper test and at what point in the intake/turbo system should I be hooking this up? From my previous research, this is what I was originally going to go with:
Thoughts? Thanks again for the assistance guys, it is slow going with all the other stuff going on in my life, but progress continues to move forward bit by bit.
The way I usually do a boost test is to get some thick plastic bags and double or triple them up by folding them over and clamp them over the 2 spots where the intake is - either by removing the cone intake or on the elbow to each turbo. Then, find a vacuum nipple on the upper intake manifold and hook a hose from that to a "blow off" gun going to your air compressor. Dial the air compressor down to 15 psi or so and start pressurizing. Look, listen, and feel for air leaks. The bags on the turbos should "inflate" but not leak and if the bag is thick enough it won't rupture.
Thought you all might appreciate an update on this since I hate searching for threads that have my exact same problem and then the OP never tells what did or didn't fix the problem after people made suggestions. First off, this car has been being SLOWLY built over the course of the past 5 years, so nothing ever seems to go quickly (life happens a lot and takes priority). Anyway, I had decided to purchase a new intercooler since the OEM one was simply not going to cut it. I also decided to buy a Greddy compression tube so I could ditch the stocker with its giant rubber vacuum cap as well. After I had the OEM intercooler removed and it was sitting on the garage floor, I happened to look at the bottom intercooler hose and noticed this:
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Well, that explains where all my boost was going.... I couldn't see it since it was on the underside of the lower intercooler hose. A boost test would have surely revealed it but I had already decided this stock IC needed to go so no worries there. I replaced it with this:
So for those keeping score, Dale was pretty much right in all his suggestions : D I was able to install the new intercooler and, with a bit of modifying, keep the Apexi intakes as well.
PS: Yes, I know I need a duct. I just bought, modified, and installed this intercooler though so I will have to worry about fabbing up a duct next time. Car is barely driven though so no worries at the moment. Thanks for the help everyone!
05-28-19, 12:03 PM
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