adamrs80

iTrader: (7)

My car is stock other than a drop in K&N and an HKS downpipe. Recently I've been seeing 11.5-12 psi on the VDO mechanical boost gauge in 4th or 5th gear. Speed is between 70 and 90 MPH so no real high RPMs. I don't think there is enough time in 2nd or 3rd to build boost above 10 or there is not enough engine load at that point to push it above 10. I am just guessing though. I always run 93 octane and I have an AEM water injection system so I think I'm still safe from detonation, however I am still a bit concerned. I know the stock ECU is safe up to maybe 11 max, but better at 10psi to be safe. I have not made any changes to my car so it is almost as if it just started boosting higher by itself. The weather here in San Antonio, TX is still in the high 80s if that makes any difference. I don't drive the car when it's over 90 or below 50.

What is the best way to solve this? It there some sort of bypass that can be set to bleed boost once a set PSI is reached? I wish I knew why it has been boosting higher recently but not in the past.

96fd3s

not enough time in 2nd or 3rd to build 10psi boot?
i will get 10psi boost almost instantly from 2k rpm + all the way to redline in 2nd or 3rd gear..

adamrs80

iTrader: (7)

Yes, I guess not enough time in 2nd or 3rd to build boost. I'm going to go for a spin Saturday morning so I'll check out the boost in 2nd and 3rd again but I was pretty sure it was only in 4th and 5th. Either way it's making too much and I don't understand why it's changed. I was rock solid 10-8-10 for months after installing the K&N and HKS DP. I felt like with the stock exhaust and cat (all stock besides DP) that the boost would not get that high. I certainly want to protect my good original engine and keep it safe.

Turbo8

iTrader: (17)

It's not that you don't have enough time to build boost, it's that in the higher gear you are generating more engine load which spools the turbos differently, and your wastegate can not flow enough to compensate for the addition in load. What you are experiencing is wastegate creep.

But with your water/meth injection, I wouldn't worry too much. I've been boosting 12.5psi or so on the stock ECU with 350cc/min of progressive water/meth injection for a couple months now. Of course, your situation might be different, and I wouldn't recommend it.

To fix the creep you either port the wastegate (easy to do, but requires removal the twins), or buy a boost controller. A simply $30 ball & spring manual type will do the trick, but an electronic boost controller will allow for greater flexibility and tuning.

arghx

iTrader: (3)

I doubt the wastegate is being overwhelmed mechanically with the stock cat and downpipe. The factory boost control system is mapped for the factory intake and downpipe. In colder weather more boost is being achieved at higher gears, but you haven't hit fuel cut or anything. I'd just keep driving it.



You can see the "boost zone" allows higher pressures from about 3000-5000 rpm, which is probably where you are experiencing it.

adamrs80

iTrader: (7)

That chart was hard for me to understand but I see the "overboost" point from about 3k to 5k that you're referring to.

I just drove the car. All the runs I did in 4th and 5th were from 55 to 80. Temperature outside is 70° F
It will repeatedly boost to 12 in 4th or 5th but it basically hits 12 for 1 second max, and then drops to 11 or 11.5.

It will briefly boost to 12 in 3rd gear but only if I shift into 3rd from 2nd early and start pulling from 2500 or so. If I downshift into 3rd going 60 or 70 there is not enough load to push it to 12. So I only hit 12 in 3rd when I start at low rpm and only for a second.

It's running smooth and perfect, no noises that would indicate deto, but I have heard so many times that 10 psi is safe, 11 is possible trouble that I'm concerned.

Is there anything I need to do or should I just not worry about it?

Mahjik

iTrader: (1)

Add an electronic boost controller and you'll be fine. It's just a boost spike due to the cooler weather. However, it could get a little higher as the weather gets cooler.

arghx

iTrader: (3)

It'd be nice to have a wideband on there to make sure it isn't running lean, even though it's probably fine. You could drill out the restricter pill for the wastegate if you're really worried about the boost. Aftermarket controller would be one solution, but it's not like those don't vary with the weather still.

IRPerformance

iTrader: (41)

Get a proper electronic boost controler, or don't floor floor the car when in higher gears and low rpm.

adamrs80

iTrader: (7)

Can any of you recommend a good simple elec. boost controller? I might end up getting a wideband too but i really wanted to keep my car stock and uncluttered.

adam c

iTrader: (2)

The limitation for the stock ecu is volume, not boost. The stock ecu can supply "X" amount of fuel, regardless of boost. You could run 20 psi of boost at low rpm (read low volume) and be safe. I don't think there is anything wrong with your car, or anything that needs attention. It should boost higher with the mods you have done. If you never hit fuel cut, you should be fine.

Mahjik

iTrader: (1)

http://www.rx7store.net/product_p/profecspec2.htm

adamrs80

iTrader: (7)

Thanks to all of you for the advice. What a great resource.

I'm going to look into drilling out the restrictor pill. Are there any disadvantages or negative side effects? I'm assuming that would allow more boost to be vented by the wastegate. I just want to do it right the first time and protect my engine. I don't have any current plans to raise the boost or do any modifications that would raise the boost so maybe drilling the pill would be the best solution. A powerFC is about the only thing I've got my eye on.

adamrs80

iTrader: (7)

What about going this route?

https://www.rx7club.com/3rd-gen-archives-73/my-boost-control-setup-perfect-10-8-10-pattern-178136/

Turbo8

iTrader: (17)

There are no ill effects of drilling the w/g pill, it will just result in lower boost. The actuators are 7psi actuators, so the purpose of the pill to restrict the pressure signal sees and allow it run slightly more boost. You can remove the pill altogether and you should run between 7-9psi.

That would be a great way to control your boost. You need two manual boost controllers. He used higher-end Hallman Pro RX boost controllers, but you can use cheaper $30 ball & spring manual valves and you'll be fine.

arghx

iTrader: (3)

Dual manual boost controllers are one option if you're ok with spending the time adjusting them.

the reason why I like the factory dual solenoid design is because it keeps the wastegate completely shut before transition, and it keeps the precontrol completely open after transition.



In the above diagram the 95% duty means the actuator is shut, while 5% means the actuator is fully open. Mazda designed the precontrol and wastegate solenoids to work together with the sequential turbo system. You can't really do that with aftermarket systems. The only boost control system that can do this properly is the Power FC itself, because it mimics the factory control system.

I don't see what the big deal is with swapping or modifying a restricter pill in this situation. You know Rx-7's aren't the only turbo cars with restricter pills right? The Evo X has one turbo, 3 restricter pills, and two solenoids from the factory and that car runs 23psi peak from the factory.

adamrs80

iTrader: (7)

All I want to do is get back to 10-8-10. If drilling or replacing the restrictor pill is the best way I am all for it. I prefer to keep things as Mazda intended and use the stock turbo control system because I think it works pretty well. I don't drive my car much, usually less than 1000 miles a year. I'd like to keep it simple, OEM.

Do I have to remove the turbos to get to the restrictor pill? Is there a specific thread in the FAQ that I should be looking for? I am hoping to avoid having to try different combinations of pills. Just looking for the simplest solution, but I always want to do it right the first time.

Montego

iTrader: (1)

since you dont want a cluttered interior my suggestion is to run a boost controller and ditch the boost gauge. Given that most controllers display boost in real time it doesnt make much sense to have both.

IRPerformance

iTrader: (41)

Spec 2 is a piece of garbage in my opinion. The spec S is simpler and works better in my experience. Don't mess witht he pills. That's opening a can of worms.

MrNizzles

iTrader: (5)

I wouldnt mess around with drilling the pills (pita trying to find a measurment that hits 10-8-10 on the money)... they are easy to get to though if you want to remove them and test what the boost is like.

I would just get an ebc unit. easy to setup and will be most reliable for holding at 10psi. porting the wastegate would be good too!

any cooling or fuel reliability mods? radiator? alum ast? vac lines? fuel filter? fpd? fc thermoswitch?

arghx

iTrader: (3)

Beyond old internet forum rules of thumb, I'm not convinced there is a problem with him briefly hitting 12psi but only in his current mildly modified configuration. I'm sure the mixture is rich enough, but he can verify with a wideband. He's got AI on there already. The JDM cars had a precatless downpipe from the factory anyway. Clearly Mazda expected boost to climb a little bit right after transition, or why else would they have raised the fuel cut so high?

I know several "oldschool" owners who used to run downpipe and catback back in the day on stock ECU (which is riskier than the OP's setup) and never had any problems despite small boost spikes occasionally. One guy I know got 110k out of his original motor in that configuration. Remember, one mistake with an aftermarket manual or electronic boost controller and you can get crazy overboost.

If it were my car I'd just keep driving it and stay on top of the maintainence (fuel filter etc). There's no need to be a hypochondriac about it. Mods blow engines, and this car is basically stock.

adamrs80

iTrader: (7)

I have an aluminum AST, new mazda fuel filter a few months ago, and a pettit fan switch. I think my car still as the fan recall fix. I also have an extra OEM foglight switch on the center console in between my fog lights and defroster switch that will turn the fans on whenever but the pettit fan switch seems to override the fan recall because the fans run for some time after shutdown regardless if I've switched the fan switch on for 2 minutes before shutdown or not. Fans come on low at 180 and it never gets above 190 for me. I have all the hose and dale clark check valves for a full vac job but I've been putting it off because the car runs so good.

adamrs80

iTrader: (7)

I thought about getting the AEM Tureboost setup. It could replace my VDO poost gauge and it's the controller too. I tried real hard to find gauges that match the car though. I might just go to the trouble of porting the wastegate and see if that fixes it.

Is the general consensus that porting the wastegate will solve this boost creep?

adamrs80

iTrader: (7)

After doing some reading I have come to the conclusion that I am overboosting and boost creep is not my problem. I did not understand the difference earlier when I started this thread. I am assuming that since I still have the stock main cat, stock cat-back, and stock airbox that my higher boost levels are not creep but due to cooler TX weather, K&N filter, and downpipe. Some kind of electronic boost controller should be installed and I can lose the boostgauge and put something else in it's place. It sounds like a Power FC would not solve the problem but it could be tuned for the higher boost.

Am I wrong on anything I stated? Should I port the wastegate anyways?

arghx

iTrader: (3)

Agreed.

You can adjust the boost control duty cycles of the factory solenoids using the Power FC. So yes, it could address the problem without needing anything else, as long as it's set up properly. But as I've been trying to explain, you are trading one set of hassles for another. The Power FC will run ok in your configuration but there are a number of idle and throttle response problems that can come up which are not normally an issue with the factory computer. And this is coming from a guy who wrote a Power FC guide. You can't beat the factory computer for overall driveability and reliability as long as you don't try to use it on a setup that has too many modifications.

Pull the turbos out and risk messing something else up in the process? Heck no. If it ain't broke, don't fix it. I personally think your car ain't broke. Have you ever pulled the turbos on an FD with all the plumbing still there??? Do you have any idea how many things can go wrong???

You've got a bigger chance of screwing something up by messing with the car than by leaving it alone, and I'll stand by that.