Just purchased my first Rx-7! Its a 1989 TII. The guy I bought it from did a few mods like a HKS short ram, magnecor wires, and removed the air pump and hollowed out the cats. A few bugs I need to work out, It does smoke on start up and backfires maybe twice before finally clearing up after a mile or so. What causes this? Also, from the mods, the boost level has increased dramatically and is causing fuel cut on the rear rotor. Is there a way to turn down the boost without making a purchase? I already bought a new guage, and BOV. It now reads at about 14-15 psi! Can I turn it down using anything already on the car to prevent fuel cut? Or do I have to buy a boost contoller or/and FCD? Im not trying to gain any more power out of the motor in it, Im just trying to prolong its life. Any help would be appreciated. Thanks. -Brandon

 

Get a Fuel cut defencer, a boost controller and port your wastegate! If you look down the threads on the main page there is a thread about porting your wastegate this will prevent boost creep!

 

Ok, if I don't want to buy that stuff is there a way to turn the boost down?

 

port the wastegate

 

porting the wastegate is the only way to keep the boost down with the mods you've done. I've popped a seal once due to overboost. it aint fun....

 

Fuel cut occurs at 8.6psi, so either you aren't experiencing fuel cut or you aren't making 14-15psi boost. Which is it?

If you really are boosting that high, you need to check to see if the wastegate actuator hoses are split or disconnected. Also check the hoses to and from the boost control solenoid clipped to the oil filler neck. With your very mild mods you shouldn't be boosting anywhere near that high unless there's a leak in the boost control hoses somewhere. Look in the FSM Fuel chapter (page F2-7) for a pictorial of the hoses.

If you don't have the FSM yet, click here and download FSM in PDF format for free. This is your RX-7 bible. Most of the technical questions you can think of are answered in there.

This is really bad advice. Both of these items allow boost to be raised, and neither can lower it. How are they going to help?

 

would it help if u got a 2.5" downpipe instead of 3"?

 

I dunno for sure, The exhaust is shot anyways, holes...tips rusted off, etc. So my plan was gonna be a set of headers, presilencer, and whatever mufflers I decide to put on it. I'll probably port the wastegate too. What I don't understand is, does a boost controller allow you to adjust the boost down? I 've seen some manual ones with an electronic switch that allows you to select from 2 different settings. So, If I set one to 5 and the other to 10, I can adjust it down to 5 and leave it there for as long as I like, right? Then get the FCD and be able to go up to the higher level without fuel cut? Thanks for all the help.

 

The term "headers" generally refer to a tubular exhaust manifold on NA engine, not a turbo'd one. This type of manifold is not required for a stock turbo, only a much larger aftermarket one. Unless you're planning a full turbo upgrade, cross headers off your list.

No, a boost controller can only raise boost, never lower it below what it would be without a boost controller. It's not physically possible.

You can raise boost to two different selectable levels. You still can't lower it.

First you need to clarify whether you're hitting fuel cut OR boosting to 14-15psi like you said. It can't be both. I don't recommend getting a FCD until you've ported the wastegate and upgraded the fuel pump.

 

One blown TII, coming up!

 

I was going to refrain from saying that xD

 

Haha. Well, not quite yet...I talked to a buddy of mine who owns a 3rd gen. and has dealt with plenty of turbo rotories. He suggested I remove a hose going from the wastegate to the factory boost control solenoid. Saying it would only allow it to spool at its lowest setting. So I did, and it lowered the boost down to 5lbs. No more fuel cut. Are there any consequences of doing this? It finally drove how it should've to begin with. I lost the "wow" factor but, longevity is my main concern.

 

you should really just port it. theirs tons of write ups.

 

Yeah, Im gonna. Thanks to everyone for all the help.

 

Porting it is the only way to go if your wanting to stay stock. If you wanted to keep the higher amount of boost but keep it safe I would recommend porting the wastegate and getting the FCD. I highly doubt the stock turbo can do over ~10 psi without a boost controller and the exhaust you have. You need to check the boost gauge you got to make sure its reading correctly.

 

I thought the same thing, but, the gauge the guy had on it when i bought it only read up to 10, and I was pegging it out...so I got one that went up to 20 and it read 14-15, then my buddy bought a brand new one for his car and installed it in mine first just to check to see if it was reading accuratly, then we plugged the 2 hose extensions from the boost control solenoid to the wastegate with vaccum nipples and his gauge read 5lbs. and it stopped the fuel cut I had been experiencing. So 3 different gauges and they all read differently but what seemed to be accuratly for the probs I was experiencing. I also heard that the factory boost setting on my car is around 8, which made me wonder seeing how after hooking up the second gauge, I didn't notice the fuel cut until after 10lbs. I have the owners manual, haynes, chilton, and the mazda workshop manual. Is the factory setting and/or the fuel cut level setting in any of these books? I plan on getting a boost controller and FCD anyways because I want to keep it at around 10lbs full time.

 

I don't think it actually says in those books since those books are how to repair the car not really the technical information about the engine and turbo. I believe the turbo was supposed to be running at 7psi. The stock turbo/intercooler max out at 15psi which is why I'm concerned and you should also be concerned about that as well.

 

6.6psi for S4 and 8.3psi for S5 (which he has).

More like 12psi. 15psi is way to much for both.

 

Cool, thanks again to all for helping someone brand new to the scene.

 

my stock s4 turbo with not enough porting in the wastegate boost to 15 no problem with the wastegate opening at 6.6. Ive verified it. Now high rpm it may drop off im not about to find out but it will def do it. Just wanted to say that for all the people who say it wont do it. Now ive got to port more. I will put a thermocouple on the TB elbow and prove the effective range of the s4 stocker but im not quite there yet.

 

Nobody ever said it won't do it. Plenty of people have run that much boost on a stock turbo, but the point is nobody does it for long because it considerablt shortens the turbo's life.

 

or if u have 500 dollars i think...order that HVC that SMP has...I use that to control the boost...im capable safely to boost 10psi but i like staying around the stockish 7-8psi

 

A boost controller can't lower boost, if that's what you're implying...

 

Ok, so...after getting my boost under control, I put a simple ball and spring controller on it, and tweaked it back up to around 7lbs...Car still smokes when it's cold, I think I need a turbo rebuild, anyone know where to get a factory turbo rebuild kit for a decent price?

Also..when I'm really gettin' on it, The car hiccups, or ticks and I feel hesitation. It's the same problem I started this thread on, At first I thought it was fuel cut. But my experienced rx7 friend said it was detonation. Sooo....Now what am I to do? Anyone who has any ideas please help! Id preshiate it!