just wondering at what psi the waistgate on the Turbo II opens at. Or simply what is stock boost for a Turbo II, sorry for the noob question but i need to know if my boost control is necessarry or not for my n/a to turbo conversion, or if it boosts enough without it. thanks

 

Stock max boost is 6.6psi for S4 and 8.3psi for S5. Neither will hold this all the way to redline though. Both turbos have the same wastegate actuator but the S5 used electronic boost control for faster and higher boost.

 

the s4 and s5 turbos also have a different (better) wastegate design, so you don't have so high boost spikes like the s4 ones (unported wastegates)

 

so in order to run 8 psi on a s4 turbo i will need a boost control correct?

 

No, pretty much any intake and exhaust mods will see boost rise due to the S4's tiny wastegate. Once you start increasing airflow the challenge is keeping boost down, not raising it up. Wastegate porting is essential.

 

I thought the s5 wastegate was set to ~5.5 psi and it uses an electronic boost controller to get the rest?

 

stock boost on an S4 is 5.5 and on an S5 7.5, on paper at least, in real world applications this might be different.


speed monkey: yeah, there is a boost control valve (that's not it's real name I don't think) mounted to the soloniod rack / oil filler neck that increases the boost.


CptnObviousFC: I would get an electronic boost controller, I don't recommend using the limeted waste gate to control your boost, that's sketchy. plus electronic boost controllers allow boost to raise faster and give you more control.

 

I have the Profec 2, a ported wastegate, t4 hybrid. Just plugging it in and having it off I hit 12psi. Anyone have luck with these profecs? Recomendations?

 

You're both wrong. The max boost numbers are as I posted above, both taken straight from the FSM. I have corrected this misinformation dozens of times, but the same mythical numbers keep getting reposted.

And like I just said, they have the same wastegate actuator. The S5's higher boost is from the stock electronic boost control.

 

Zackery! I got my Profec B2 to work great last night. A consistent 11psi and it spools way faster.

 

NZConvertible-so when u say the waistgates will not hold untill redline do you mean boost will creep or decline?

 

will spike at late midrange rpm and fall down on high rpm levels... (tested it today on the freway... spikes @ 0,7bar, falls down to 0,55bar on an S4 turboII)

 

will spike at late midrange rpm and fall down on high rpm levels... (tested it today on the freway... spikes @ 0,7bar, falls down to 0,55bar on an S4 turboII... happened in 4th and 5th gear, first - 3th is fine...)

 

The turbo runs out of breath at high rpm's and the boost drops off.

 

Since I saw this elsewhere Ill ask, how much boost can the stock injectors handle?

 

Well, that answers my question of how much boost a stock turbo will handle

 

^^ they cant handle 14-15psi. i found that our the hard way. my HKS ebc iv is currently set to .7bar. im gona try for 1 bar with 50 psi of fuel pressure. gona build boost slowly 91 0.5 bar at a time with the controller and keep and eye on the a/f ratios and fuel pressure and ajdust accordingly until i see it begin to lean out then back the boost off a bit till its running safe.

 

So 10psi. Safe or unsafe?

 

Unsafe, you can run up to 9psi if you have a fuel cut defender on the stock ecu/fuel system.

Anything above that is asking for the engine to blow.

10 psi can be done with an rtek ecu upgrade, 720cc secondaries, and upgraded fuel pump.

After 10 psi the stock tmic isn't cooling as efficiently , and after 12 psi the stock Turbo isnt efficient.

 

Ok so i need more fuel in order to run up to 10psi boost. And i know jack and **** about injectors. Fuel pumps i can bumble through. And is tmic the intercooler? Or what is it?

 

Yea tmic is top mount, Ive seen ppl run 12 psi on them but say intake temps start getting really hot.

Fuel pump you can get an fd fuel pump, or walbro. The ecu u can get the rtek chip upgrade for around 150. Injectors you can get many places.

You'll need to determine if your car runs low or high impedance injectors. The earlier 87 models did and 88s didn't.

 

Ok i was thinking about installing a larger inter cooler behind the front clip and replacing the stock radiator with a larger one maybe aux electric cooling fans would that improve the ability to boost? And is the fuel pump in the tank or on a body rail or something? I dont own an rx7 yet just planing out my mods for the future. Im looking at 2

 

STOP! get the thing running 100%(or at least as close as possible) before you go throwing money at it. this forum/google is your friend, i see you did search to revive a 7 year old thread so keep it up and do some reading so you know how/where to start modding. these cars can be alot of fun, but also a PITA once you start tinkering.

 

The 2 im looking at are on here just waiting to hear back on the posts. When i get 15 posts ill be posting a want add if i havent bought one yet. The 2 im looking at 1 in il has engine out of it plus extra stuff and 1 in Kentucky that needs a rebuild for a bad seal. Eather of these seem like a winner?

 

Are they both Turbo? If they're NA then don't bother if you want a Turbo car, and if you're thinking you can buy an NA and swap to a Turbo setup its still a bad idea. A Turbo swap will cost you a ton of money and is alot of work.

Find a car that's complete, if its blown then you're looking at roughly $1500-2000 just for an engine rebuild.

No matter how you look at it, unless you get lucky and get a car with a good engine for a good price you're looking at dropping a few grand into getting the engine rebuilt and doing all the proper maintenance needed for it to run reliably.

The more boost/power you're wanting initially will drastically increase the cost of running it reliably (tuning/supporting mods are crucial), which is why most people recommend starting small before going big.