Max HP and Max Boost on Stock Turbos
 

I did all my research on the forum, did all the searches and read all old threads but nothing too specific.

Currently my FD is making 315HP to the wheels at 15psi with an a/f of 10.9 (pretty rich eh)? My injector duty cycle is at 73% so I have a lot of fuel left to deliver.

I know a lot of people say 15psi is the most to go on the stock turbos to stay reliable. My question is say I boost to 16psi or 17psi, keep in mind I never street race or race at digs or redlights, no tracking, no autocrossing, no dragging, etc. The only time I may actually boost the car to 16-17psi is when I'm on the freeway and it would be at most 1-2 times on a drive. Also, my FD is not a daily driver (taken out only 2-3 days a week if the weather is good). So with a very conservative driver will it be bad to keep the bost at 16-17psi, and 95% of the driving will be boosting at less than 10-11psi?

People say anything over 15psi you are decreasing the lifespan of the turbos. When people say this are they thinking that the driver of that car will continously boost the car or frequently see over 15psi and race all the time?

Any guys out there over 15psi with stock turbos having problems?

Also, I read up that the max hp that can be extracted out of a stock twin is around 374hp to the wheels. I'm aiming for 340-350hp is that asking too much?

BTW, my mechanical mods are:
1. Greddy 2 Row FMIC
2. Apexi PFC
3. 1300cc secondary injectors
4. Apexi Air Intake
5. Lightened Flywheel
6. Heavy duty pressure plate
7. Exedy Extreme Clutch
8. Platinum Spark Plugs
9. Down Pipe
10. Mid Pipe
11. JIC Catback
12. New Vacuum Hoses
13. Fluidyne Aluminum Racing Radiator
14. Greddy Boost Controller
15. DEFI Gauges

Thanks for the help in advance.

Thanks for the thread. I guess nobody really knows, its all subjective.

Yep, it's all in the tuning. ;)

What gets me is that the non believers all say it'll blow up in a few weeks or 6 months. Are they thinking these drivers boost the car to 17-18 psi every drive? What if the driver only boost the car to those levels 2-3 times a week only, and probably only lasts 10 secs per extreme driving.

Than there is a believer that says they've been doing it for 2-3 years with 0 problems.

I'm guessing that if you are a cautious driver and not the pedal to the metal guy than you won't run into problems.

Problems probably would occur if you plan to street race every weekend, drag, track, etc.

You have to remember, that most people on car forums repeat what they "hear/read" not what they have experienced.

Here are my thoughts: Will it kill your turbos? Not really. It will most likely shorten their lifespan but that's with anything you run higher/harder than they were intended to be used.

Keep in mind, the stock map sensor is limited to around 17.5 PSI, so anything over that you'll need the GM 3Bar Sensor.

I don't plan on going over 17psi. I would upgrade to '99 spec twins by than. The thread is great reading, hearing from both sides.

I do agree with you that a lot of members repeat what they heard.

with the set up you have i do not think you will have any problems... yes u may put some more stress on the turbos... most likely if they r original they have inter nal cracks already. how many miles on the turbos? this is from my experience not hear say...

I only have 20k on the engine and turbos. Since I've owned it I've only put very easy miles on the car, only briefly diving it fast maybe 1-2 times a week.

So far I've done more research and it looks like atleast 4 FD owners have made well over 350hp with 0 problems so far.

And another (local to me):

I saw 2 FDs made 380 hp on stock twins.

turbotuner.com, do you have any boost creep while running the MP?

Between 13 to 15psi did you even see any power gains ? Ive had my car tuned a few times and going above 13psi we didnt really gain as much power because even that was a ways out of the stock twins' efficiency rating. I did gain a small amount of power going beyond their efficiency but mostly torque.

I look at it like this a car 93 rx7 is now 10-11 years old..so the stock turbos even if they havent gone past 10psi are OLD....
so if you get say some low milage ones and run them 17psi (or whatever thier peak is) yeah theyre gonna las..not 10-11 years but shit you may get a season or 2 out of them...

Your not fast unless your breaking stuff. .. :)

The boost increase from 13-15psi is pretty substantial for me.

Here are my dyno graphs.


http://www.turbotuner.com/dyno/002.jpg
This was dynoed at 13 psi if I remember correctly.

http://www.turbotuner.com/dyno/003.jpg
This is a comparison dyno, 15psi not tuned well. Than 15psi tuned well with an a/f of 10.9 only! Goes to show you can 17hp just by having a good tune without increasing psi.

Well from my understanding once you go over 15psi your way off the effiency range of the stock twins.