For some reason in the last few days, my boost is tempermental. Under normal operation, the boost is normal, even when driving spiritedly...however...after driving it hard, once in a while there will be no boost produced.

I can't figure it out...all the hoses are intact and tight. It's odd that I 'll be driving along enjoying the ride, then all of a sudden I feel like I'm driving a yugo, then a couple minutes later, the boost comes back on.

Needless to say that when I bring it to my mechanic (who knows rotaries very well and owns three RX7's) the problem doesn't arise.

Very frustrating. If anyone has any ideas, it would be much appreciated.

TIA

By the way, my turbos are sequential

 

I have the same exact problem....except for when I get on the gas under WOT it will only make 5psi or so, and then when I let off the gas it makes a weird "whoo-er" sound, unexplainable! and then sometimes it will boost just fine....=O(

 

I forgot to mention the sound after I let off the gas! It's so weird, it sounds like a a low pitched whistle or something, right?

Really weird

 

yup!! hopefully someone can help us figure out this problem....It only recently started happening to me, it's quite annoying. =O(

 

Are you running stock boost? If so, maybe a bad TC solenoid. If you are running more than 10 psi, I will look further into my post of boost problem, and there is a fix, my car boost fine now. GOod luck

 

do a full boost run... then when boost isn't built correctly - momentarily come off the throttle before going WOT again - if it builds normally it means the vacuum tank isn't holding vacuum due to the check valve.

it pretty much has to be a switching part/system, as all the mechanical parts would have that problem constantly.

 

sounds like for some reason the secondary turbo is not comming online, when you go wide open with this problem the whirring sound you are hearing when you lift off is the pressure from the primary turbo spinning the secondary backwards....not good...try not to do it till you fix the problem...look at the turbo control actuator, lines and according solenoids, also a leak in either the boost or vacumn chamber can cause this.

 

OK, I'm a little confused....i looked into rotarypolo's boost problem post...is what sereneseven is saying essentially the same problem, or a totally different hypothesis?

Also, the fix that was done for rotarypolo's problem, could someone please try & explain it a little clearer? If I put the regulator on and set it to 10 psi, please explain how it "tricks" the turbo system. Is it possible to overboost by putting that on, potentially damaging the engine?

 

The soleniods are spring loaded - too much pressure or vacuum and it will prevent the spring from opening/closing them. As well, age and dust can weaken or damage them. Even new solenoids have trouble switching at 14-15psi.

The pressure loaded into the pressure chamber easily exceeds 12psi in a stock car, and of course goes higher for higher boosted cars. This will lock the turbo control solenoid and slow the secondary response, unless you install a pressure regulator to keep the tank around 10psi. (It only needs about 8psi to work reliably).

I'll bet that your solenoids are going bad when hot or some other annoying problem.

Dave

 

No, it's just REGULATES the airflow to 10psi, that's what the stock system was made to operate at. You wont overboost, has nothing to do with that.

 

Could I just change out the old solenoids for new ones? Is that an expensive process?

 

+1.....

 

3GRX7, PM Saxyman - he recently held a GB on replacement solenoids with all new check valves, basically all new parts for turbo control. It also relocates the solenoids and makes them easier to work on. He may still be able to make you up a kit, although im nto sure.

 

4 important solenoids at $60/ea. Def. do the check valves too.

Worthwhile, IMO.

Dave

 

$60 each for solenoids?

that'll be awhile before I get to that.

 

Used ones are $10-20/ea, and with a Mityvac you can test and sort out the good ones.

I do think it's worthwhile to buy new turbo control solenoids - they all eventually go bad, and for $120 it's well spent.

Dave

 

I think I'll be going the used route

....$240 for 4 solenoids at $60/ea just isn't looking good in my book, i'd rather ride around and stay out of boost before I spend that much on new solenoids....

 

Are there a total of four solenoids? Do all four need to be replaced...aren't some not really necessary?

 

There are about 10 in the area of the rats nest. There are two that fail first - the turbo control solenoids. Then there are two more that are turbo-related which are a pain to change if they fail - the charge control and charge relief solenoids.

The last two turbo-related solenoids is the green wastegate/precontrol pair, which is not cheap to buy new but very easy to access. And plenty of used ones out there. They don't tend to fail that often IME.

There are even more solenoids that I have not mentioned because they aren't for turbo control. So really, 2-4 is a very economical solution to the problem.

Dave

 

thanks!

 

I tried this several times, and it doesn't build boost correctly....also I think it has to be the turbo control solenoids (the 4 solenoids the other guy was speaking of) that som, or one of them has failed completely now, because it won't build boost properly anymore at all.....won't even work sometimes anymore.


Also I heard that I might have a boost leak, my car is suppose to build boost when I rev itup at idle? It doesn't boost any at all now.....but before it use to build 2psi or so...

I think I'm going to go ahead and replace all of the turbo control solenoids / check valves......& hope that that is my only problem currently preventing me to boost correctly.

 

Can you keep this thread informed of your progress Mate, I have the same problem after having larger injectors, HKS RS Induction kit and a boost controller fitted. From cold the car will boost fine, its only when it gets warmer that I have the problems where you accelrate hard past 5000rpm then let off and accelerate again only to get 0.5 and then the weird noise.

Driving me mad now !!!
Cheers,
Gareth

 

TrevorC....any progress with our issue yet?

 

yes, updates please. my car seems to be having the exact same issue. all my selonoids, hoses, and check valves are all new. its pissing me off.

 

unfortunately I don't have $200 right now to spend untill I get paid the next friday after this week......and unfortunately I don't have alot of time to work on my car as I work alot.

since then I've followed up on some threads such as:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/rx7-poor-accelaration-497716/page2/

but I haven't got around to checking that out yet to see if my solenoids are good, also I've PM'd "saxyman990" about a solenoid / check valve package / group buy he is doing for pricing (dunno the price yet) if it does tun out my solenoids / check valves are gone bad.