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RX-7 2nd Gen Specific (1986-92) RX-7 1986-92 Discussion including performance modifications and technical support sections.

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Old 03-14-2008, 11:50 AM   #1
wvumtnbkr
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Default What should I do to protect my new engine?

Good Day!

I am doing a turbo swap on my NA (series 4). I need a new exhaust, but I am afraid of blowing the motor with excessive boost.

My understanding is that the only way these cars regulate boost is through the internal wastegate. Is the wastegate big enough? Is it necessary to port it right from the start? What are the drawbacks to this?

Second, is an FCD a good idea? Do I need to upgrade the fuel system as well? (already planning on a Walbro fuel pump).

If I upgrade my injectors, will the computer recognize the larger injectors and lower the duty cycle (through the 02 sensor loop)? <-- I doubt this!

Anybody have any good ideas on how to make the turbo system reliable?

Thanks!

Rob

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Old 03-14-2008, 12:05 PM   #2
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What series Turbo are you using? A S4? If you are putting any decent exhaust on a S4 turbo, you need to port the wastgate which is actually pretty easy. S5s are btter when it comes to the wastegate functioning properly, it still may need ported. While the wastegate technically limits boost, the real limit on boost is the stock exhaust restriction. On a mildly ported S4 wastegate and a 3" Intake and Exhaust my car has boost crept as high as 16.5psi with about 10-12psi being normal in 3-5th gear. I have since opened the port up all the way so will have to see how it works out

I would recommend the pump upgrade definently.

As far as injectors, it will not recognize them and will run poorly in my experience. If you want bigger injectors, have your ECU upgraded by Rtek.
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Quote:
Originally Posted by Wesley Carlock aka RotoriousRX7
"Rotarys come with built-in traction control, its called no torque"
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Old 03-14-2008, 12:16 PM   #3
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I don't "want" bigger injectors, I am just wondering about increased safety in case of boost creep.

I have been looking at the RTEK 1.5. Is this a good way to protect the engine? It retards timing by 1 deg for every 1 psi over 9.

Also, it gives the injectors an extra 5 % max duty cycle. <-- does this mean that if you do encounter boost creep, it will help you run safely to say 10 psi?

What is the max guage pressure that I should be concerned with? Basically at what psig should I be getting out of the throttle?

Thanks!
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Old 03-14-2008, 12:37 PM   #4
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Upgrading the injectors isn't a bad idea.

I have a 89' vert running on the stock turbo with a FMIC and 3" TB exhaust system.

I installed mustang 5.0 fuel injectors and after warm-up, the car runs wonderfully. Running 12lbs of boost on the stock turbo, I've never had any problem with boost creep or overboosting.

Max boost your looking at on the stock turbo is about 12-15lbs. Anymore than that and its more than likely that your going to break something....

Last edited by g14novak; 03-14-2008 at 12:41 PM..
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Old 03-14-2008, 01:45 PM   #5
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Quote:
Originally Posted by g14novak View Post
I installed mustang 5.0 fuel injectors and after warm-up, the car runs wonderfully. Running 12lbs of boost on the stock turbo, I've never had any problem with boost creep or overboosting.
This doesn't make any sense...
Stock V8 injectors are like 30 lbs. / second?
Even upgrade ones are only like 35 lbs. / second.
Stock FC turbo fuel injectors are 550 cc / minute, which is actually slightly higher than 50 lbs. / second.

30 lbs. / second = ~ 300 cc / minute
35 lbs. / second = ~ 350 cc / minute

Even stock FC non-turbo fuel injectors flow at 460 cc / minute, which is higher than stock Ford 5.0 fuel injectors.


-Ted
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Old 03-14-2008, 12:42 PM   #6
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I can't those specifics because even though I ran that much boost on stock injectors, I had some helpers such as 45psi of fuel pressure(more pressure means more fuel through the same injector opening period), a standalone, and water/meth injection. The Rtek would be a good idea though. The thing is with a FCD, once you reach the factory boost cut limit( I believe its 8 psi), the FCD just keeps telling the ECU that you only have 8psi of boost regardless of actual boost which mean its not compensating with more fuel and retarded timing. If you are going to say only 10psi, you will probably be fine. but any higher and you are starting to get risky.
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Quote:
Originally Posted by Wesley Carlock aka RotoriousRX7
"Rotarys come with built-in traction control, its called no torque"
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Old 03-14-2008, 01:40 PM   #7
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Quote:
Originally Posted by 85rx-7gsl-se View Post
The thing is with a FCD, once you reach the factory boost cut limit( I believe its 8 psi), the FCD just keeps telling the ECU that you only have 8psi of boost regardless of actual boost which mean its not compensating with more fuel and retarded timing.
Once the boost gets into +, the boost sensor has nothing to do with fuel delivery; it is all ignition timing retard.
Thus, FCD does not affect fuel delivery at all.

Max ignition timing is around 17 or 18 degrees total advance, so even with premium octane, running up to 15psi is no problem.


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Old 03-14-2008, 01:42 PM   #8
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Quote:
Originally Posted by RETed View Post
Once the boost gets into +, the boost sensor has nothing to do with fuel delivery; it is all ignition timing retard.
Thus, FCD does not affect fuel delivery at all.

Max ignition timing is around 17 or 18 degrees total advance, so even with premium octane, running up to 15psi is no problem.


-Ted

My bad Ted. I never really messed with a FCD. Bought one through RB, then went Microtech instead so never used it.
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Quote:
Originally Posted by Wesley Carlock aka RotoriousRX7
"Rotarys come with built-in traction control, its called no torque"
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Old 03-14-2008, 01:47 PM   #9
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Quote:
Originally Posted by 85rx-7gsl-se View Post
My bad Ted. I never really messed with a FCD. Bought one through RB, then went Microtech instead so never used it.
No problem.
It's a common misconception.
We figured it out when we bench tested the stock ECU.
We used to argue till we were blue in the face trying to convince people this was the case.
When the RTEK guys cracked the stock ECU code, they just confirmed what we had found years earlier.


-Ted
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Old 03-14-2008, 01:37 PM   #10
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Quote:
Originally Posted by wvumtnbkr View Post
My understanding is that the only way these cars regulate boost is through the internal wastegate. Is the wastegate big enough? Is it necessary to port it right from the start? What are the drawbacks to this?
Porting the stock wastegate can only help and not hurt.
Even if you do "over port" the wastegate, a boost controller can bring the boost levels up again.

Basically, if you're going to run a freer flowing exhaust, porting the stock wastegate is highly recommended.

Drawbacks?
It's labor intensive...
If you port too much, boost levels will decrease (but see above comment to fix this).

Quote:
Second, is an FCD a good idea?
It's required if you're running a stock ECU.


Quote:
Do I need to upgrade the fuel system as well? (already planning on a Walbro fuel pump).
Upgrade fuel pump is highly recommended...
The stock 4 x 550's max out at around 240hp at the wheels.
If you're shooting for more power, you'll need larger fuel injectors and some way to control them.


Quote:
If I upgrade my injectors, will the computer recognize the larger injectors and lower the duty cycle (through the 02 sensor loop)? <-- I doubt this!
Only in closed-loop...
At cranking, idle, and WOT, the stock ECU has no clue...


Quote:
Anybody have any good ideas on how to make the turbo system reliable?
Don't actually understand what this question means...
How to keep the turbocharger from blowing up?


-Ted
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Old 03-14-2008, 01:53 PM   #11
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^Glad to have someone on here with your knowledge and experience... I myself am I a relative noob to rotarys, but I like to get my hands dirty
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Originally Posted by Wesley Carlock aka RotoriousRX7
"Rotarys come with built-in traction control, its called no torque"
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Old 03-14-2008, 03:06 PM   #12
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Quote:
Originally Posted by 85rx-7gsl-se View Post
^Glad to have someone on here with your knowledge and experience... I myself am I a relative noob to rotarys, but I like to get my hands dirty
Not meaning to hijack a thread but my thoughts exactly. I'm glad you're around and have always been grateful for your site man.

Another thing is proper cool down after extreme driving for the turbo. Either by letting it idle for a few mins or a cool down lap driving home so to speak.
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Last edited by Turbo II; 03-14-2008 at 03:48 PM..
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Old 03-14-2008, 04:04 PM   #13
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Default Rtek 1.5

I am feeling the RTEK 1.5 would be the way to go. It eliminates the code in the computer that would require an FCD.

The main question I have is: If the system boosts over stock levels, let's say to 10psig, will the RTEK recognize that there is actually 10 psig and retard timing? Or will it just see a max of 9 psig and that is it?

What I am trying to get at is what is the max guage pressure that the computer can recognize with the RTEK 1.5? 9 psig, 12 psig, 15 psig?

If the RTEK equiped computer can see 15 psig, what will it do? (add fuel, retard timing, etc...?)

Thanks!

Rob
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Old 03-15-2008, 09:13 AM   #14
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A good friend of mine ran this setup:
S4TII
S5 turbo
Full RB exhaust (no cats)
Banzai TID
Rtek 1.5
RC 720cc secondary injetors

He ran 12psi all day long with no issues (and the stock TMIC). The Rtek was great, did what it was supposed to do, no fiddling with settings all the time.
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