kosoku

with aftermarket exhaust, I'm aware that mp should be installed AFTER power fc or it'll boost spike like crazy and possibly blow the engine.
is it okay to install dp and mp on stock exhaust if I keep the boost at 10psi?
I was doing the dp install and found out that it doesn't bolt right up to the stock cat.

quicksilver_rx7

installing the DP is okay. installing the MP is dangerous on the stock ECM even if boost levels are kept stock because you have to worry about boost creep and boost spike because the WG is too small and can't bleed off the excess pressure from the turbo, and the stock ECM can't supply the fuel. You're better off to spend the $1500 for the PowerFC and play it safe, than to risk having to install a new motor.

John Magnuson

A PowerFC won't cure boost creep. It may allow you to run enough fuel to not blow your engine when the boost does creep to high levels but it won't fix the problem. You need to either port your wastegate or get an aftermarket turbo and wastegate.

If your car is stock keep the cat on. You're just looking for problems with an MP.

BigBoosting

You can do downpipe and midpipe on stock ECU and stock exhaust (or even aftermarket exhaust) if you just take out the 2 restrictor pills. Your wastegate will open sooner...but then you'll only be able to run 7psi. But you'll be safe at least. Then once you can get the Power FC or other management, put the pills back in and you should be fine. But if you're that boost crazy and must have 10psi, just keep the whole thing stock until you can get the Power FC.

quicksilver_rx7

John is right. I wasn't suggesting that the PowerFC would fix boost creep, but the fuel will be there to aid, until your injectors or stock fuel pump run out !! Also, do as John says and leave the stock cat on until you get an ECU and port the wastegate, or get a single turbo. You're looking for trouble if you don't.

It is my humble opinion that the first mod should be an ECU

Montego

iTrader: (1)

He stated keeping the boost at 10 psi. That means no spike, no creep at least to me that is.

Currently, I am running a M2 CAI, DP, and MP on a mild street port. With a stock muffler. I maintain my boost at 10 psi via profec B spec II. No problems what so ever.

Yes you will be fine as long as you do not boost past 10 psi. Get a an electronic boost controller that shows boost in real time and a boost gauge so you know for sure that you are safe. Don't get the MP unless you have a means of controlling boost.

kosoku

this ebay downpipe came with the midpipe. downpipe doesn't bolt right up to the stock cat. I think I'll pay a muffler shop to install the dp to the stock cat.

one thing I liked about my old supra was that you can do full exhaust with no cat on a stock ecu. (12 psi stock, it creeps to 13-14psi with no cat) On top of that, you RAISE the boost to 18 psi safely and you now have a 400rwhp BPU Supra. just easy bolt-on that costs $1000.
stock ECU(except you add a greddy boost cut controller for $60), stock intercooler, stock radiator, stock fuel,etc supports over 500hp.

kosoku

I just read your post and I think I changed my mind. I'm going to try to run dp+mp and set the boost to 10 psi.

Stix37867

iTrader: (1)

I actually am running a dp and mp with the stock exhaust and ecu. I'm not having any problems except for blowing a small hole in my exhaust from shooting flames. Replacing my exhaust with catback soon though so it doesn't matter for me. My boost only has spiked to 13, maybe 14 psi. I'd say that you should just keep an eye on your boost to see what it does, and go from there.

kosoku

Does it spike to 13-14 psi all the time? that's dangerous!

Stix37867

iTrader: (1)

No. It usually only spikes in first gear when i launch. All other times my boost is at 11-12.

John Magnuson

Get your FD out of the snow!

Stix37867

iTrader: (1)

The weather people suck here. That snow came overnight out of no where. It was out about two days later.

legal-z

it's unlikely that your actually getting 11-12 psi with your stock ecu or you'd be hitting fuel cut, especially in higher gears. if you haven't calibrated your boost gauge or you're running a cheap one (something like an autometer), your reading is likely incorrect. my autometer reads 1-2 psi high and 3+ in/hg low consistantly. if by some chance you are running that boost level, i would start saving for a rebuild in the near future.

rx7girlTK

how about dp and catback with stock cat on stock ecu? i have a avcr i am going to set at 10.

quicksilver_rx7

Fuel cut occurs at 12.1 psi (0.851 kg/cm²) (0.8345 bar) on the stock ECU. If you wanna blow the motor, keep running with the stock ECU. A boost controller controls boost, "IF" the wastegate is sufficient, which it isn't. It does not control the boost creep that occurs at high RPM related to the small and insufficient wastegate on the stock turbos. You can put on a "Pop-off" valve to help control boost creep, but this is just a band-aid.

ADVICE: Get a PowerFC

Montego

iTrader: (1)

The boost controller does control the spike that is one of the main reasons that we purchase them. But it does not do jack **** for the creep though.

legal-z

i don't believe that's correct. fuel cut occurs at different psi's depending on what rpms you are at. there is a table on this board that shows what psi fuel cut occurs at when you're running certain rpms. i'll look for the thread now. as for the advice, i agree. or at least get an upgraded ecu.

edit,
i got it wrong the first time, but here is the table.

http://www.scuderiaciriani.com/rx7/fuel_cut_info.html

quicksilver_rx7

I know there are several different opinions on when fuel cut occurs. Mine is based on the information that Mazda provided in the Sevice Highlights Manual provided to dealers. I'm just trying to give the guy some idea that he needs an aftermarket ECU.