Two modified boxsters on the dyno

[itsnotanova]

[QUOTE=mjannone;567143]

Originally Posted by itsnotanova

I purchased the NHP headers and mid pipes from Softronic (DME tuner) as part of the 3.4L conversion package. Softronic's website says the headers are 42mm primary piping (vs. 34.5mm for stock) with a 53mm exit pipe (vs. 42.5 for stock), and the mid pipes are 50mm (vs. 40mm for stock). These all appear to be an improvement over stock.


I am using the stock small-diameter U pipes that connect the mid pipes to the Beluga ebay muffler. There clearly is room for improvement here as these stock pieces are 40mm in diameter.


I am curious to know if the more restrictive, but larger diameter 987 muffler you have is a better performer than the less restrictive, but smaller diameter Beluga ebay muffler. I do know the Beluga muffler sounds insane at WOT where it is a full-blown race car soundtrack. Neighbors (and most wives) will object. It has calmed down a bit in the 400 miles I've put on the car since installing it, however there is no mistaking that its a performance car now. When I had the stock 986 muffler on the 3.4L, there was virtually no difference in sound from the 2.5L. It was quiet and unassuming, and obviously down big time on power.

Post 185 of my build thread Woody's build thread, I go into detail about my exhuast system. You'll have to use Google Chrome to see the pictures. I'm thinking your problem is the factory U-pipes. You're only as big as your smallest opening. My whole system is 50mm or larger throughout and has a smoother path than the factory 986 or 996 system. I'm thinking the system I built might be less restrictive than the 996 system as I made more power than a factory 996. That's if the dynojet was correct. That also might explain the lean running condition. More air in and out but no increase in fuel.

[deathsled986]

Originally Posted by itsnotanova

That also might explain the lean running condition. More air in and out but no increase in fuel.

OEM 986/996 injectors are only 230cc/min if I'm not mistaken which IMO are woefully undersized and at the practical limit. At 100% duty cycle and a fuel pressure of 43.5psi 6 230cc injectors are theoretically only good for around 290bhp.

I'm not surprised to hear about modded 3.4 lean issues at all. You should be completely out of injector given the math.

**edit**

I just found that fuel pressure in a 996 is actually 55psi, so that should give a little more headroom, like 6 more bhp.

I'm surprised Porsche put such a small injector in these cars. I've always been under the impression you really don't want to run an injector more than 80% IDC just so you have some additional margin. That would mean you really want an injector around the 290cc mark. That would run a motor comfortably at 300bhp and give you room to grow up to around 370bhp.

[jaykay]

What do folks with 3.2s modified for 3.6 or 3.8 do for injectors....don't ever hear about capacity issues

[seningen]

Originally Posted by deathsled986

OEM 986/996 injectors are only 230cc/min if I'm not mistaken which IMO are woefully undersized and at the practical limit. At 100% duty cycle and a fuel pressure of 43.5psi 6 230cc injectors are theoretically only good for around 290bhp.

I'm not surprised to hear about modded 3.4 lean issues at all. You should be completely out of injector given the math.

**edit**

I just found that fuel pressure in a 996 is actually 55psi, so that should give a little more headroom, like 6 more bhp.

I'm surprised Porsche put such a small injector in these cars. I've always been under the impression you really don't want to run an injector more than 80% IDC just so you have some additional margin. That would mean you really want an injector around the 290cc mark. That would run a motor comfortably at 300bhp and give you room to grow up to around 370bhp.

So the real question then is if Woody's boxster is setup up for 55psi or not.

Mike