I have been having some boost issues with my single turbo rx7 when I boost above .8kg. When I have my car boosting around .9-1.0 kg I see the boost go all the way to .9 or 1.0 but then at higher rpm's (around 6000-7000) I see the boost start to go back down to .8 or .85. The turbo seems to not want to hold the boost at higher boost levels. This boost issue only happens when I boost more than .8 kg, can someone tell me what kind of issues I might be having? I'm using the Apex'i RX6 turbo kit with the Greddy profec B boost controller. Anyone have any similar issues or know what's up?

 

Check settings in the Profec-B make sure that your gains and warnings are set correctly check physical small boost leaks that allow boost to bleed off and such. My first guess, settings on the boost controller, but it could be many things.

 

Not using the T-66 anymore?

 

I went round and round with a similiar problem with My TD06-20g kit. I had several problems one of which was the gasket between the Turbo and the turbo manifold was leaking and ended up eating part of the gasket away...to my amazement...if you have a leak look for black exhaust dust...you may need to clean everything well but you'll find the leak pretty quickly, unless you are leaking somewhere on the intake track...then its a different story

Make sure all your gaskets are in good shape and that everthing is torqued down properly...also eliminate the boost controller from the equation and run off the wastegate spring. Connect pressure source right after the turbo but before the intercooler to the bottom nipple, leave the top nipple unplugged(normally the same pressure source would go through the solenoid to the top nipple) Make some runs you to get a baseline of where your boost is just running off the spring. I think the rule of thumb for adjustability is 150% of the spring pressure so if your running 10lbs of the spring you should be able to use a boost controller to run up to 15lbs.

If you have adjustable wastegate spring start cranking the spring in...my greddy type r wastegate is adjustable not sure about the apexi kit...if it's not adjustable get the next higher spring up..probably a 12 or 14lb spring. You should run the closest spring to what ever boost you you want...although you should easily be able to run 1 bar with that turbo. I've drivin my freinds car and it was rock solid at 16lbs and he has a sweet setup...funny thing is, it's neck and neck when we run even when I'm @ 12lbs :-)

To this day I still can't get more than about 12lbs of boost out my little TD06-20g turbo I'm pretty convinced that Its just run out of breath for my setup...trapped 118mph 12lbs of boost on a rolling start 1/4 mile so I know I'm making in the 375hp range since I previously ran 118, 11.9 after dynoed 380hp331tq on the non seq setup 7 years ago....still can't find somebody to compare power with for that weeny turbo....o well...I'm going to try the next spring up for kicks but I don't think thats it...going to have it modded to a 25G probablly. O also check the bolts holding your wastegate together and make sure they are snug.

Be curious to see your progress maybe you'll find something I missed...but gees it just can't be that hard...you would think.

 

hmmm, sorry i cant help you too much but im having a slightly different prob with my rx6 kit. just had the hitman do some street tuning on it and with the profec-b set at 14lbs it would hold it to about 7K in third but then it would begin to creep up to 16lbs by 8K. im going to try and fiddle with both the settings on the profec and on the wastegate itself and try to see if i can stable it out... im thinking the apexi wastegate may be a lil too small for my application, guess we'll see and ill let ya know

 

Anyone know if changing to a better boost controller like the SBCID would help?

 

I would try and avoid the added cost by checking some of the suggestions made above but the SBCID is a fantastic controller especially when mounted with the power meter.

 

why not get just a mbc, i use one and i swear by it... its almost impossible for it to fail.

hell able iberra uses one on his rx7..

a turboxs hpdsbc to be exact

 

but yeah i would check everything else before buying parts.

its stupid to throw money at cars when it dosent fix the problem.

 

i had a similiar problem with my profec b... i switch to the apex boost control kit for the power fc and no more problem.

 

Profec B's are definitely not my first choice.

 

what's your first choice then?

 

SBCID if going electronic. Otherwise a well made manual works well you just can't brag about it being all fancy.