I have a 1988 10th ae rx-7. The only mods is a Racing beat turbo back exhaust but the downpipe is not installed now (the cats are there for emmisions). I am planning on putting on the downpipe soon and would like to turn up my boost to about 9 psi. I am concerned that this will lean out my engine though. Could I install a Rtek 1.5 so enough fuel would go to the engine? Also, how am I to change the boost at exactly 9 psi? Thanks for your time.

 

With the RB turboback you will be boosting more than 9psi for sure unless you port the wastegate. You will have problems keeping your boost down.

 

I am not going to be able to port the wastegate. What other setup could I run that would allow me to increase boost without blowing my moter? Also, how can I regulate how much boost I put in it?

 

i have heard the stock injectors are goot to 230 to 240hp. so unless you plan to pull power out of no where then you should be ok at 9psi.

you will need a FCD for $50-$100 (search), and it would be a good idea to get a walbro 255lph fuel pump. you can buy new walbros on ebay for right about $100.

odds are with just adding a DP and still runing stock catback you might see 9psi... might creep to 10 on 4th gear pulls...

lowering boost bepends on your waste gate. What ever it goes to with no boost controller is always going to be the "low setting". With a boost controller you can raise the boost from this "low setting".

 

ok so your running the turbo back soon.. or keeping the cats? i just re read your post... but my answer still stands.

 

from what ive read the rtek doesnt add fuel above the fcd range.. just retards timing and makes the secondary kick in range lower. (someone correct me if im wrong).

 

The Rtek removes the FCD feature which stops you from using the stock maps. So you do get to use the maps higher up and in addition they add retarding.

An Rtek will just make buying a FCD useless.

I would buy that and then buy a Walbro Fuel pump.

With that you will be set to boost like a crazy *** and not worry.

 

I own a 10 Anniv too. I have RB exhuast, Open Air intake(ducted to the outside), Walbro Fuel Pump, the Rtek 1.5, and a manual boost controller just to help at the low end. You will be ok if you just have the exhaust and the Rtek 1.5, and you will like the results. I ran with Full RB Exhaust and FCD for several years with no troubles.

 

I don't think you understand. Because of the very small wastegate, if you install the rest of the exhaust you will have too much boost, far more than the 9psi you say you want. If you don't want to port the wastegate, then you will not be ably to safely run the engine with the rest of the exhaust installed.
With a properly sized wastegate...

A boost controller can only raise boost, it cannot lower it. Until you can properly control boost, you should not fit one.

 

I talked to some people at Racing beat and they said there was no way that I could get boost creep to 15 psi or anything like that. I think it would assist me if I knew the exact way it works:

As RPM's rise, more exhaust is "made" and that spins the turbo which then forces air into the engine. Now, the wastegate lets out pressure at a specific PSI to not spool turbo beyond a specific level. Now, how does the wastegate know what PSI that is? Also, placing in the fuel cut controller elliminates fuel cut to the back rotor past 8.6 psi. So how does the computer know to increase fuel for the increase in boost pressure? Also, if I add the downpipe in, how does this affect the boost pressure/wastegate initiation? Finally, if porting the wastegate is what I need to do, how do I go about this and is it difficult (time taken)? Thank you for your time.

 

the waste gate doesn't "know" it simply was designed to let a certain amount of exhaust not go through the turbine so it won't boost too much. Once you start freeing up the flow then more exhast witll go into the turbo and spool it more thus more boost. If you port the waste gate you solve the problem, unless your running more than a ported wastegate can handle

 

Still confused: at what levels is the wastegate "designed to let a certain amount of exhaust not go through the turbine so it won't boost too much"?

 

I'm not really sure but i think it was just like mazda made the waste gate big enough to give them as much bosst as they wanted but this was all working with stock parts. Once you start to modifie then you nedd a larger waste gate port to keep the boost low. I'm no expert tho hopefully someone who knows more will post soon

 

It is really common sense. The stock size of the intake and exhaust are made so the car can only flow enough exhaust gas thru the turbo to make 8psi or whatever the stock setting is. Now when you increase your exhaust diameter, it allows your engine to flow more exhaust gas through the turbo, which will make it spin faster, thus raising the boost. The wastegate is a little door on the side of the turbo held shut with a spring, and when the boost reaches a enough power to push that spring open, it bleeds off the excess pressure. The problem is, when you have a tiny tiny hole, and a lot more boost, it can't efficiently bleed off all the excess pressure, so it still makes it past the turbine, which is bad, because you will be boosting too high. By drilling the wastegate hole and making it bigger, it allows your turbo to bleed off the excess pressure easily.

Hope that helps. Im no expert, but thats just how I have always understood it.

 

Couldn't have explained it better myself, people continue to say that they will just keep their boost low when they get a boost controlle, but the LOWEST a boost controller will hold you to is whatever your boosting right now without one.

 

Thank you guys, I understand. I am now toying with the idea of doing it, however there is a drawback.....I have a 10th AE rx-7 with 130,000 on it and 50,000 on the new engine. The enigne has low compression (about 90-95 psi). If I drill the port out a bit, and therefore increase my boost with the downpipe, am I doing more dammage than good. I mean, the car is old and has a lot of miles on it. I just don't want to complete this for one summer of fun and boom, there goes my rotary rocket. What do you think? Keep the car with the racing beat exahust and NO downpipe or put the downpipe on there with a drilled wastegate considering my situation? Thank you for your time and input.

 

I would port the wastegate no matter what the situation. It is one of the best things you can do to save the life of your engine.

 

I don't think you need to port the wastegate at all. If you put in the downpipe, install the Rtek 1.5 chip and leave the stock air intake in place, you won't have too much boost. The chip is a much better choice than theFCD, since the ECU then gets the "true" boost signal. Make sure you have a good aftermarket boost gauge. I also added a air/fuel ratio meter to my setup. With my setup, I was getting about 12psi max and not leaning out. I added the Walbro Fuel pump later just to be certain I did not get lean, and prepare for future increases in boost.