Alright let me first say that I have a 1987 Mazda Rx-7 Turbo II with 88k miles. Next spring I will be installing my parts that I have been waiting to put on. Sadly my brother owns the garage for the winter. Anyway the parts I will be installing that are engine based are:

Rebuilt S5 Turbo (Wastegate ported)
New S5 Cast Manifold
HKS Intake
Corksport Radiator Panel
2.5" Corksport Downpipe
2.5" Mid-Pipe
Apexi Gt Spec (Single)
Emmisions Delete W/ a dual alt pulley
FD Fuel Pump

Everything else is is essentially stock.

I would just like to know how much pounds of boost my Rx-7 can handle with these modifications. Can I up the boost a little without hurting anything or would it be more wise to leave it at stock levels. Thanks people

 

first off i sent those pics lmk if you got em, and the rule of thumb is the turbo maxes out its efficiency at 11 lbs(thats stock), and i belive the stock topmount is only good to 12 so 10 is probably maxxed out without supporting mods. with a decent fmic maybe 12 depending on how the turbo was modified but anything past 10 id imagine you would want to start thinking about a new turbo anyway. dont forget too if you add more boost you need more fuel.

 

I only got 1 picture with the Nardi on the car, I received no others. And to the thread, so if I cranked up the boost using a boost controller to say around 10psi do you think I'd have any problems with fuel delivery? I've heard the rx7's biggest issue is the fuel pump but I have an FD one waiting to be put in. I just don't know what this fuel system can max at safely without damaging the engine for the time being. Later on I plan on doing a v-mount intercooler and maybe doing a Stock/hybrid turbo. Almost like a BNR stage 3. Let me know what you think.

 

fuel cut is at approximately 8.6psi, so about 8.5ish...

 

You need to increase your secondaries to handle the raised boost. 750 will do for that range. You'll also need an ECU mod to handle the larger injectors. Rtek 1.7 or will do nicely.

You should really figure out what your future plans are, and shoot for that instead. That way you don't buy upgrades twice... like myself....

 

Pretty soon I'll be building a Microsquirt ECU. My brother built his for his 86 corolla so he's going to help me put it together and tune. But essentially for the time being all I wanted to know what I could set my boost to safely. If anyone else could back up what Karack has stated that would be great. Thanks guys

(P.s. - it's not because I don't trust what you say, I would just like someone else to also verify)

 

you can go with the Rtek as mentioned to eliminate fuel cut and upgrade the secondaries, which might get you to 12psi safely, i use the term safely loosely(simple upgrades like intercooler and exhaust might push it beyond the safe level).

 

Get the rtek (megasquirt would be even better)1.7 or a fcd 720 cc injectors so you don't max the duty cycle on your 540's a fd pump should be fine a aftermarket fpr with a gauge and a fd filter also wouldn't hurt and should hold around 12-14with psi without trouble. But replace that intercooler along with all this.

 

Also on a side note 10-12 is a more reliable boost level and will surprise you with just how peppy your car will get with just those few extra pounds of boost. Stock though without a fcd of some sort your car will retard fuel an turning up the boost will just be pointless.

 

opposite, it lowers the load figure that the ECU interprets and advances the timing... and an intercooler upgrade without an actual way of reading and adjusting the fuel is a horribly bad idea beyond about 9 psi.

 

So with the mods that I currently have I can only run 8.5Psi of boost because I will hit fuel cut correct? I'm not wasting my time with RTek this is just for the time being till I decide to do my big upgrades. Hmm I wonder what kind of Hp I'll get out of this.

Probably next winter I'll be doing a V-mount, Fuel mods, an ECU, and a hybrid turbo to possibly try and hit the 350hp mark or somewhere near there. Kind of irrelevant but yea.

 

yes, the stock ECU cuts fuel to the rear rotor at 8.6 on the series 5 turbo cars. it's 7.5 psi on the series 4. the cars ran a little less than 1 psi below fuel cut from the factory, it's there to protect the engine in case the wastegate fails closed or your exhaust falls off. fuel cut defensers are a poor alternative for the reason posted in my last post, they also give a false sense of security as people crank up the boost unknowingly because the car seems to run fine, which it will until that split second where the fuel ignites at totally the wrong time and you limp home with 1 rotor chugging along.

 

So I can go to 7.5 Psi of boost since I have a series 4 Ecu, but an S5 turbo? Lame

 

Yes, and he is correct about the fcd being the least desirable option but budget wise it would be a option.

 

Another quick question that is somewhat related; I have decided to buy a stand alone ecu. Most likely the Microsquirt. Anyway, with the stock 550cc injectors and the fuel cut that has now been eradicated, what can the stock injectors handle boost wise? Keep in mind I do have an Fd fuel pump. From previously reading my guess lies around 10-12 psi. Thanks very much.

 

most people don't understand that boost is rather irrelevant once you start modifying the airflow, pressure drops and turbo efficiency by opening everything up so that it can breathe better. the stock 550X4 are good for about 250 to the wheels.

 

I would still upgrade to 750 secondaries. No reason to risk maxing out the duty cycle on 550's.

And buy a wideband.

 

I have an Innovate Wideband I forgot to mention. I'd just like to know the max boost I can go on this for the time being till I decide to go for my 350hp goal. Safely though.

 

First off, you cant upgrade to larger secondaries without a way to CONTROL them...

I would slap an FCD on it and shoot for the moon (literally... thats where your apex seals will end up)..

 

if you up boost and get a FCD, you will need some way to tune the iginition.

If you want to do it right until you are ready for the build you want next winter it would be better to get a Rtek 1.7 ecu, 720 injectors and a safc to tune the fuel. The Rtek will retard timing 1 degree for every psi above 9psi.

you can run a stock ECU with 720 secondaries and a SAFC to tune for fuel but the risk you are running with the stock ECU is that the SAFC tricks the ecu into thinking there is less airflow so less fuel, BUT the stock ecu thinking theres less airflow WILL advance the timing which will lead to a blown engine.
I ran the stock TMIC, stock turbo pushing 12 psi with 720x4 and a Rtek 1.8 for almost a year, fastest I ran on avg street tires was 14.3 secs, would be in the 13s if I had Drag slick, or even MT ET street tires.

Or you can forget about everything and just run stock for now until next winter for the major upgrades.

 

I'm probably just going to wait to get an Ecu and do some other major mods with it. I'm just reading up right now on Rtek 2.1, Apexi Power FC, and Microsquirt.