Suzmo

with the standard ECU... if a 3" downpipe is added, can this make or has anyone heard that it can decrease compression in the secondary rotor housing ?

(Edit for sig violations...check your PMs)

Mr. Gadget

Myth - the apex seals close of the exhaust port during the compression stroke. If they did not, you wouild not make any compression.

Nice car, I like the lines of white turbo models...

NZConvertible

I think what he's getting at is a 3" exhaust causing overboost, causing lean mixtures, causing detonation, causing a broken apex seal (often in the rear rotor), causing a lack of compression.

So no, a 3" exhaust does not directly cause a decrease in compression in the secondary rotor housing, BUT if you don't have supporting mods it can cause engine failure.

Suzmo

yeah thats what i was getting at NZConvertible... and what exactly are the supporting mods?

NZConvertible

Fuel basically. A big exhaust will cause boost control problems, so porting the wastegate will be necessary to let you keep boost down to where the stock turbo, intercooler and injectors are all still happy (10-11psi).You need a fuel cut defenser to get over 8.6psi (you'll probably hit that with the exhaust), and that's when you should upgrade the fuel pump.

Suzmo

well im going to test if im running a higher psi level then what my boost gauge reads.:

my knightsports FCD is connected, right. and there is a plug connected into the MAP sensor also... does this mean if i disconnect the FCD, im still good to go with the map sensor?

ive checked each plug, nothing else will go into the map sensor with whats connected into the map sensor.

once ive disconnected the FCD properly, and if i go into boost cut mode.. ill know if my boost gauge is incorrect, true?

bryanfc

evren have a read of www.fc3spro.com , theres plenty of good info about modding.

btw, your still a goose

Suzmo

ok ill check Bryan...

i still dont know what noise a goose makes tho.

bigdv519

iTrader: (3)

I would agree, only to add some type of electronic fuel control, to compensate for the leaning of the fuel maps, that MOST FCD's cause when they "lies" to the stock ECU about intake pressure. A full EMS would be optimal, but a bandaid like the S-AFC would work.

DriftingB26RX7

iTrader: (4)

ok say u put on a 3'' d/p no cats, 3'' piping and a big exhaust. what do u need to do next ??

Impreza2RX7

He said 3" Downpipe, not Turboback. You'll be fine with a 3" DP and no other mods. When it's cooler outside, you may need a FCD, I would hit about 8-9 PSI when I had just a 3" DP and MP, and Cone filter.

If you do a Turboback, it would be a good idea to get a Walbro at least, and depending on your budget, bigger injectors and a way to tune the car. If you're planning on extensively upgrading, it's a good time for a Standalone.

Suzmo

well my car has a 3" turboback exhaust system, all the way to the muffler, 4" muffler, with high flow cat, standard turbo, top mount standard computer with knights sport FCD.

i disconnected my FCD, and there was no cutting when i boosted... the aftermarket boost gauge reading .5 BAR (7 PSI) when the FCD was connected and disconnected there was no difference.

what about a fuel regulator, they can rich up the engine can the not?

NZConvertible

Furl cut is at 8.6psi, so if you're only running 7psi the FCD is not needed and will not do anything.

Bumping up fuel pressure will make the engine richer all the time, which you do not want to do. Do you even know if you need more fuel? (i.e. dyno) With your mods at such low boost I'd say you don't.

andyfc3s

tonite I have been poking around on this site and I see the same thing over and over again . That people with the same mods as me are pushing half the boost, I get 1 bar consistantly with no spike and all I have done is an intake, safcII, fcd, 3" dp back no cat exhaust, blow off valve. Did I get lucky and get the golden child of S5's. I really hope someone can tell me. Oh and a tune up. car has 87,000 on it. Sorry for the post steal but I am really wondering about all this.

NZConvertible

1 bar boost on those mods is not "lucky", it's engine and turbo killing...

andyfc3s

I've had a few shops check it out they said that everything seems great. I just don't beat on it often.

bigdv519

iTrader: (3)

You get 1 bar consistently, thats 14.7 psi. And all you have done is an intake, safcII, fcd, 3" dp, and a bov.

Ok, lets ask the first stupid question.

1. Do you have a boost gauge?
2. Did you install it?
3. Is it mechanical or electronic?
4. Where is your source of boost pressure?
5. Have you had it calibrated?

Even if you are pushing 14.7 psi, you engien wont last too much longer, much less the turbo. And you no longer have an intercoller, you have an INTER-HEATER.

andyfc3s

I ment that I have a 3" dp BACK exhaust, My boodt guage Is a defi boost vsd and the source is the bov. I agree that it wont last but that is why I don't beat on it. One of the shops I deal with installed it, and A-SPEC put on and calibrated the safc II and bov. The car runs purfect no sputtering or smoking. I wasn't trying to brag or anything I just wanted opinions on why I was pushing more boost than others that I have seen with the same mods. Any input is greatly appreciated. OH and my turbo sounds normal. Thanks everyone.

Suzmo

yeah thats right man, give it a few weeks, and you will crack a seal fo sure gangta. or damge the turbo :P

andyfc3s

ok gangsta its been like this for about a year. I don't beat on the car.

Suzmo

ah for sure, well thats prolly why brus. =)

SureShot

How can anyone resist the temptation to feel the acceleration of boost?

I even put a switch on the console to hold down boost, but It keeps getting turned on.
I'm not sure how it happens, but I look down and oops, it's on again..