Two modified boxsters on the dyno

[The Radium King]

interesting. any corrections entered for drivetrain loss (ie, this is actual wheel hp and not wheel hp adjusted to flywheel hp)?

otherwise, i would not worry about the afr readings - from what i've read, if they did the sniffer up the tailpipe approach the readings are not accurate; here's a quick search result:

tailpipe vs. wideband?

finally, looking at that 5500 rpm dip you have. i am trying to get my head around it. truegearhead had something similar. you see it on occasional dyno results. it may be an effect of scaling, as it shows up on the factory dynos also - ie, it just looks worse on a dyno that has an exaggerated 'y' scale. what is happening at 5500 rpm? the resonance tube closes again (opens at 3000 rpm, closes at 5000 rpm) and the variocam returns timing (advances timing at 1500 rpm, returns at 5500 rpm).

https://www.6speedonline.com/forums/996/205309-how-variocam-variocamplus-works-primer.html

[78F350]

Originally Posted by The Radium King

...finally, looking at that 5500 rpm dip you have. i am trying to get my head around it. truegearhead had something similar. you see it on occasional dyno results. it may be an effect of scaling, as it shows up on the factory dynos also - ie, it just looks worse on a dyno that has an exaggerated 'y' scale. what is happening at 5500 rpm? the resonance tube closes again (opens at 3000 rpm, closes at 5000 rpm) ...

Good points. That dip could just be a sticking/dirty/slow resonance flapper valve. Slight vacuum leak maybe? Electric valve starting to fail?
From an old Porsche archive:

"... Below 3,000 rpm, the cylinders draw air from a “short” path. From 3,000 rpm to about 5,100 rpm – when the resonance flap opens – the cylinders draw from a long intake path, which boosts torque. Above 5,100 rpm, the flap again closes to allow the cylinders to draw intake air from a shorter intake path to boost horsepower at higher engine speeds."

[The Radium King]

Originally Posted by 78F350

Good points. That dip could just be a sticking/dirty/slow resonance flapper valve. Slight vacuum leak maybe? Electric valve starting to fail?
From an old Porsche archive:

so, perhaps i am overthinking, but with engine conversions, and with plenum changes, often the resonance tube has to be rotated/moved for clearance; operation may have been impacted? oil can pool in the resonance tube - if positioned other than oem, it may start to not operate properly. or perhaps they get weak over time and can't return properly when faced with 5000 rpm airflows.

the other thing i am thinking is perhaps the turn-over points are not optimal for modified engines - ie, perhaps the flap should close sooner? not close at all? i presume this is not something you can change with a tune, as jfro's result w softronic tune indicates (he's got the dip too):

Dyno results!!

it would be interesting to dyno with the flap always open, and/or always closed, and see what happens with the dip.

[itsnotanova]

Originally Posted by Ciao

The first file shows the HP (about 250) of a Boxster S without mods.

The first graph is my friend's modified boxster. It has 249 at the wheels which is about 285-295 at the crank

Originally Posted by The Radium King

interesting. any corrections entered for drivetrain loss (ie, this is actual wheel hp and not wheel hp adjusted to flywheel hp)?

otherwise, i would not worry about the afr readings - from what i've read, if they did the sniffer up the tailpipe approach the readings are not accurate; here's a quick search result:

tailpipe vs. wideband?

finally, looking at that 5500 rpm dip you have. i am trying to get my head around it. truegearhead had something similar. you see it on occasional dyno results. it may be an effect of scaling, as it shows up on the factory dynos also - ie, it just looks worse on a dyno that has an exaggerated 'y' scale. what is happening at 5500 rpm? the resonance tube closes again (opens at 3000 rpm, closes at 5000 rpm) and the variocam returns timing (advances timing at 1500 rpm, returns at 5500 rpm).

https://www.6speedonline.com/forums/996/205309-how-variocam-variocamplus-works-primer.html

Originally Posted by The Radium King

so, perhaps i am overthinking, but with engine conversions, and with plenum changes, often the resonance tube has to be rotated/moved for clearance; operation may have been impacted? oil can pool in the resonance tube - if positioned other than oem, it may start to not operate properly. or perhaps they get weak over time and can't return properly when faced with 5000 rpm airflows.

the other thing i am thinking is perhaps the turn-over points are not optimal for modified engines - ie, perhaps the flap should close sooner? not close at all? i presume this is not something you can change with a tune, as jfro's result w softronic tune indicates (he's got the dip too):

Dyno results!!

it would be interesting to dyno with the flap always open, and/or always closed, and see what happens with the dip.

Thanks. I'll look into the flap valve. I'm stuck on the AFR as mine gets leaner as the RPM's get higher and his gets lower. I kind of trust the readings as I've heard of a few 3.4 swaps having that issue. I plan on investigating that closer. As in another way of sampling and then what's causing it. I don't think a vacuum leak as it seems to rise with rpm. That really seems like a fuel delivery problem to me. I believe I changed the filter already. If I get confirmation from another source that I'm running lean then I might replace the fuel pump or jump up on the injectors. I'll have to see what's my best option

[jaykay]

Wood,

3 questions regarding your friends 3.2

Where are the cats in his exhaust system? Does he have fabspeed headers with cats incorporated or are they in the mid pipes?

What is the nature of his DME bench tune?

What is the drivability / throttle response of his car like below 4000 rpm?

Originally Posted by itsnotanova

The first graph is my friend's modified boxster. It has 249 at the wheels which is about 285-295 at the crank



Thanks. I'll look into the flap valve. I'm stuck on the AFR as mine gets leaner as the RPM's get higher and his gets lower. I kind of trust the readings as I've heard of a few 3.4 swaps having that issue. I plan on investigating that closer. As in another way of sampling and then what's causing it. I don't think a vacuum leak as it seems to rise with rpm. That really seems like a fuel delivery problem to me. I believe I changed the filter already. If I get confirmation from another source that I'm running lean then I might replace the fuel pump or jump up on the injectors. I'll have to see what's my best option

[itsnotanova]

Originally Posted by mjannone

It was a Dynojet at Superior Automotive in Placentia (near Anaheim).

What's the diameter of your exhaust system? The the biggest problem with the 986 exhaust system is that it's way too small. That's why I used a 987 muffler. It's the same diameter as the 996

Originally Posted by jaykay

Wood,

3 questions regarding your friends 3.2

Where are the cats in his exhaust system? Does he have fabspeed headers with cats incorporated or are they in the mid pipes?

What is the nature of his DME bench tune?

What is the drivability / throttle response of his car like below 4000 rpm?

JayKay,
He lives in an area with emissions and has the pre-cats but not the secondary cats. He said he had to send his DME off to some place out in Germany but didn't tell me much more. He believes there's a quicker throttle response with the larger 74 mm throttle body.

[mjannone]

[QUOTE=itsnotanova;567122]What's the diameter of your exhaust system? The the biggest problem with the 986 exhaust system is that it's way too small. That's why I used a 987 muffler. It's the same diameter as the 996

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.

[jaykay]

Originally Posted by itsnotanova

What's the diameter of your exhaust system? The the biggest problem with the 986 exhaust system is that it's way too small. That's why I used a 987 muffler. It's the same diameter as the 996


JayKay,
He lives in an area with emissions and has the pre-cats but not the secondary cats. He said he had to send his DME off to some place out in Germany but didn't tell me much more. He believes there's a quicker throttle response with the larger 74 mm throttle body.

Thanks Woody,

I am surprised that the 3.2 is up to 290 with cats in the headers......and stock air box