TinyFC87

i recently picked up a 90 TII with 40kms on rebuild and was wondering what is the stock boost on it, i did some searching and couldnt find anyhting. i thought it was like 5 or 6 psi or somthing. i was also wondering what was the most boost you could get on stock turbo and be somewhat safe or not too risky.

dont want to go too crazy jus a little more power till i get front mount and bigger turbo.

scathcart

7.5 psi is stock boost.
12 psi or so is where I limit the stock turbo's usable efficency.

NZConvertible

As per the FSM, stock max boost for the S5 is 8.25psi, dropping to 7.5psi at redline.

TinyFC87

so is there much more of a risk running 10-12 puonds on stock turbo? i mean i know higher boost wares engine more but by how much. and since you say the stock boost is7.5 and can be safely ran daily with 12 why did mazda set it to 7.5 and not 10? just some thoughts i had today while at work.

BlaCkPlaGUE

They ran it at 7 becuase they wanted to prove to the market that rotarys are reliable, they didn't want to take any chances running more and having it fail.
The rotary handles boost really really well, but it doesn't handle detonation well at all. As long as you have a FCD and an SAFC at the least, you should be able to run 12psi. Im not sure about the stock injectors though, what they're capable of, someone else here can input that information.
If I was going to run 12 I'd convert the TMIC to a front mount as well.

TinyFC87

how hard is it to convert the TMIC to FMIC? just till i can get bigger FMIC

fstrnyou

Kids, don't try this at home!!!!

I've been running 18+psi on my stock turbo and TMIC for over a year now, with the only major problem being the accelerated wearing of the turbo bushings.

RotaryEvolution

iTrader: (30)

i don't think the stock turbo can efficiently provide flow past 14PSI, anything over that and you are just killing the poor thing...

fstrnyou

well, once i get my ECU in and have an effective boost contolling wastegate, i'll be messing around with different pressures and see what kind of interesting information i can come up with. I never said 20psi was ok. it's just with the 850 secondaries, have to run more than 17psi to keep from flooding the motor.

88t2romad

after 14 psi the turbo is just blowing hot air, which is past the efficiency range of the tmic, and the turbo. And the fuel system is probably at its peak.

fstrnyou

for a long time, i ran 18+ on the stock injectors but with a 255lph pump. granted, it was getting very very lean. actually, when i ran that psi in 5th, i got a lean sputter when the revs were over about 5.5k because the injectors just couldn't spray anymore.

TinyFC87

so say if i were to get a MBC and just boost it to 10 pounds, would i need anyhting like bigger injectors or fuel pump. or would i be good for about a month or so till i get FMIC and fuel pump and injectors?

dr.jones63

Assuming you have a totally stock car, and you want to make some totally safe HP, no emissions testing.

1. DP
2. Straight pipe to replace the cat
3. Those mods alone will raise your boost way past "safe" so you wont need a boost controller you will need the oposite. You will need to port your waste gate
4. Higher than stock boost will hit boost cut and the ECU will cut fuel to the rear rotor so you will need FCD (https://www.rx7club.com/showthread.p...creeping+death) or a Rteck
5. FD fuel pump, 20% higher flow than stock totally plug and play with no poor fuel economy like some people get with a walbro.


You can find some really good deals by doing a search in the classified section. You should be able to do all that for about $350. Way cheaper than a rebuilt motor - $2500

TinyFC87

ok i already have DP and not cat. and i was hitting fuel cut so we are getting the FCD in the next day or so. then you suggest getting a bigger Fuel pump and porting the wastegate before boosting it a little more? this will be the best and most effective way you say.

dr.jones63

Yes, I got a FD fuel pump for $40 delivered to my door by doing a search in the FD parts for sale section. You also need a after market boost gauge to know what boost your really running if you dont already have one. Be sure and run premium gas, 10 psi boost all day. If you don't port your waste gate you can/will blow your motor. I'm doing 10 psi with a FD fuel pump in my 87 T2 daily driver and I got 22 mpg on my last tank.

TinyFC87

so to get the wastegate ported is that a do it yourself thing or should i get it done by proffesionals? or can i get a pre ported one or new one?

uRizen

iTrader: (2)

Wow, that beats my GXL's measly 17mpg average (I can't keep my foot off the gas though).

dr.jones63

Its very easy. The hardest part is taking it out the first time with all the heat shields. The main thing is be carefull with the gaskets because they cost more than the saw drill bit so you want to re-use them if you can.

http://fc3spro.com/TECH/HOWTO/KWG/kwg.html

http://www.teamfc3s.org/forum/showth...?threadid=8341

NZConvertible

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/serious-s4-wastegate-porting%85-343788/

dr.jones63

Also be carefull with the banjo bolt that connects the steel vaccum line to your twin scroll actuator valve. I broke mine and it's a pita to replace. Welcome to the RX-7. Working on your car is almost as much fun as driving it.

TinyFC87

lol thanks ill start with all this upgrades and stuff here in the next week.