New 4 inch exhaust. awesome, except for fuel cut. LOL

ArmandoP

Supramania Contributor
Nov 4, 2006
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Indianoplace
ok, I reran the car just now, and now that I got rid of the stock 3000 pipe it actually hits fuel cut at 10psi. The problem is now worse. ugh. Is it possilbe Ive just increased efficiency too much?
I know the wastegate is opening because I can hear it come fully open at 6psi (BIC DDP)
 

rumptis

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Aug 16, 2005
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North Vernon, IN
If your piping has all been replaced then maybe its your IC, I have seem them burst on the edges. Matt had 3 boost leaks on his car...very hard to track down sometimes, the last one we found was in the Intercooler. Best way to test it all is to pressurize the entire system if you have the means to do so. If you don't I'm sure John does and I have access to all things needed.

Good Luck.
 

Boost Lee

Bee Doo Bee Doo Bee Doo
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Sep 13, 2006
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^Don't we all? ;)

I'll say again - Probably one of the best sounding MKIII's I've ever heard.

Best sounding makes reference to sound/tone/power gain. It is amazing.
If it says anything, my beloved RS-R ExMag...I'll be putting up for sale shortly. ;)

Armando - It's VERY likely that it's your intercooler. But the only thing that doesn't add up is that you're already at positive boost by 2500rpms...and boost leaks usually set you back a bit further in your powerband.

Hmm...:dunno:
 

ArmandoP

Supramania Contributor
Nov 4, 2006
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Indianoplace
torque may win races, but you should see my old dyno graph. That torque wasnt winning much of anything. At 3000 rpm it would peak then quickly fall off. Im willing to bet if I can keep it from hitting fuel cut on the dyno it picked up atleast 20lb ft and the same in hp at te wheels. But Itll be on the dyno again soon enough.
 

Adjuster

Supramania Contributor
Ok, have you tried this.

1)You need more air "leaked" around the AFM sensor. (There is a stock port in the lower passage, with a bolt in there. That bolt is tuned/turned to give you FC at about 12 to 13 psi of boost based on air flow through the stock AFM.)

By opening up that port, you "leak" or bypass more air around the Karmann wave signal meter, and that allows you to "lean" out the engine some while also allowing more boost pressure/air flow before your computer does FC.

It is simple.
Remove the AFM.
Remove the sensor. (Three screws.) Do not touch the sensor tube, and lay it off in a safe place where it will not get damaged.)
Now, drill out the plug cap over the screw in the small air passage.
Do not damage the honeycomb screen in any way. Be careful with this, it's expensive to replace it.
Ok, when you have a hole in the plug, often you can pry it off/out with a small screwdriver. If not, just drill it out completely.
Now, with a larger common screw driver, back out the stock air screw plug till you can not see it blocking the lower air port.

Put back in the sensor, and see if your FC is now higher.

If you want more, you can put a small K&N style filter on a un-used port of the accordian hose. (If you have an un-used one.) That will leak even more air, and raise FC even higher.

If your car is running super rich, this might cure it. I'd try the screw mod first, then do the filter if you think you are still rich, but testing with a wideband is much safer when you start doing mods like this.

Good luck.
 

MDCmotorsports

Offical SM Expert: Turbochargers
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Mar 31, 2005
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2543arvin said:
Well. then Im waiting for someone from MDC to PM me a price then.....:naughty:


You won't like it. Neither has any one else. Tiz the reason why this is a one off just for Armondo.

Adjuster:

You make a good point. Im just not sure that doing all this would create his car to run THIS rich. Im talking it litterally looks like a diesel when you pull up to a light. You can see steam ship style black soot pooooouring out the exhaust....
 

ArmandoP

Supramania Contributor
Nov 4, 2006
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Indianoplace
Adjuster, I think I will play with that option next. When my PCV hose came off of the accordian hose it was still hitting fuel cut, but its worth a shot. Im not going to let it run higher than 12-13psi and it will be done on the dyno with a wideband up the tailpipe so Im not too worried about any problems, as I AM well aware of the effects of running lean on too much boost.
Thanks for the info!!!

As for the rich issue, I have never seen it do what Jon is talking about above. I even had a buddy drive it while I followed. When it comes to a stop after a hard run it will let out some oil smoke, which I imagine is from the turbo seals going out. It also goes rich when the turbo spools and then when it blows off it does the fireball bit, but only if you dont get right on it again. Far from what I see come out of a diesel. But either way, it does run rich.
 

rumptis

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Aug 16, 2005
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I'm just shocked you are 12-13 psi without any shimming or turning the boost up. I wonder if you wastegate isn't having problems, the diaphragm could be leaking or something could binding up and its not opening up enough. Something just isn't right here.
 

suprra_girl

7M POWAH! ;)
Mar 30, 2005
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my car would run 11psi all day everyday with no complaints for ages, but i was sick of over running the starter coz i couldn't hear if the damn car was going or not (too quiet) lol.
I had a pod filter, boost tap, some crappy intercooler piping, not stock but not super duper stuff either and a stock exhaust.

i went up and got a 3" exhaust made (still had the stock elbow tho) went to accelerate like i normally do and got somewhere about 8psi and hit fuel cut.
I spend days finding these "boost leaks" and never did. I took off the boost controller and just ran the wastegate and would still hit fuel cut at about 8ish.
Fuel cut sucks so i bought a hks fcd (moves, doesn't eliminate) and put that on and omg i got past 8psi lol
Full boost with that setup was about 9 psi and i cranked 250rwhp with a very unhappy turbo.
Then replaced with a 46 trim ct and just by changing the turbo i got 280rwhp

And my fuel cut lived happily ever after!
(till my head gasket blew, and a dumbass that doens't know how to build engines put my thrust washers in backwards and just lots of bad luck, but she'll be going in the next few weeks :D hehe)
 

ArmandoP

Supramania Contributor
Nov 4, 2006
313
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Indianoplace
rumptis said:
I'm just shocked you are 12-13 psi without any shimming or turning the boost up. I wonder if you wastegate isn't having problems, the diaphragm could be leaking or something could binding up and its not opening up enough. Something just isn't right here.

Well, before the exhaust I could go to 12.5 or so, but it would fall off rapidly.
according to the dyno:
3200rpm -12.5psi
3500rpm - 12psi
4000rpm - 11psi
4500rpm - 10psi
5000 rpm - 8psi
5500rpm - 7psi
and so forth
without the boost controller it did 6psi rock solid from 2600rpm - 5200rpm where it fell off to 5psi.
This was with a boost controller. Since that dyno pull, the only thing I changed was the exhaust. (aside from the 3000pipe yesterday which worsened the fuel cut issue, but thats nothing)

Like I said man, the only thing that has changed is the exhaust. The day before the exhaust it would not hit fuel cut with the mbc set to 11psi. After the exhaust it hits fuel cut anywhere from 10-11psi with no boost controller and it is doing it at a lower rpm which tells me its alot more efficient now. Also, look at the pictures, this exhaust has all of two bends, each of which is about 10 degrees, doesnt get much closer to running a straight 4 inch pipe than that.

Just goes to show how restrictive the stock exhaust can be. Im sure it didnt help that mine was actually some cobbled together mufflershop special complete with crush bends.
Im gonna talkt to Jon about getting down to his shop this week and maybe running a leak tester on it youre welcome to come with me and inspect/take it for a spin yourself. I would be grateful if you you DID find something wrong with it.