924srr27l

Hit me with your Rhythm Stick...........!


R

V2Rocket

I think it was misunderstood what we were saying...
The AFM works well, and the Motronic is a good system. Hits the power targets Porsche etc had, and is reliable.

It's just that in the 30+ years since L-Jet and the AFM came out, there are better options available that unlock more power out of the box and support making even more with other modifications.

With your mods listed above I'll give you 153 at the wheels or about 180 @ crank. Your larger bore and worked cylinder head are the main things on that list, along with the exhaust depending on how it is designed.

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..
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Soon I will be installing the MAP-based VEMS ECU on my 944...and just for comparison sake I will run back to back runs with a given tune, with the sole change being the inclusion of the AFM in the intake system. It will be "dead" (not plugged in) but the flapper will still actuate as originally intended. No tune changes, just doing some dyno runs with the AFM in the inlet tract, and then some more with the AFM removed, to compare the differences.

That should put to rest any debate about restriction, or not! Stay tuned for the coming weeks.

odonnell

I'd guess 160 whp tops. It's clear you have made up your mind regarding air metering, so: would you at least be open to the idea of running a larger bore AFM? Airflow is going to be the limiting factor.

Tuning it will also impact the power. A stock 2.5 pegs open the AFM door at ~4500 rpm, with a 2.7 on the stock AFM it will be even less. Remember, after the door is fully open, the AFM isn't sending a load or flow signal... only air temperature. The stock DME doesn't have a way to measure MAP or TPS, so the upper 1/3 of your powerband is going to basically be a rough blanket estimate of how much fuel and timing advance the engine needs based pretty much on RPM only. Too much timing and the motor will ping, too little and power is being left on the table.

924srr27l

Ok thanks....................Crank then.......

R

924srr27l

hhhhhhhhhhhhhhhhh

R

V2Rocket

The WebCam will certainly help get that goal.

Don't know the "round side" dimensions, but the "square inlet side"...

2.5 NA is 50x50mm (2500 mm^2)
2.5S/2.5T/3.0S2 is 50x60mm (3000 mm^2)

So 20% more cross section/flow area.
Don't know if the stock 944 DME will understand the airflow of the larger AFM though.

Ish_944

EDIT: done

So you said in the other thread that you're looking for +35 ps. Here's my take, nothing more, nothing less.

You started with a 924S 2.5l with ~152 ps if it was made before 86.

Stock 2.7l was 165 ps, so +13 ps.

- 3.0 S2 Block (Honed to 105mm)
- 2707cc Capacity
Stock: 2681 cc
That's a 0.97% increase so +1.6 ps.

- 2.5 951 Crank (Knifed Less 6.6Lbs)
- 968 3.0 Conrods (Balanced)
- Wossner Forged Pistons (Balanced)
- CR 10:9:1
+0 ps because that CR was stock in the 2.7l.

- 2.5 L 8 valve Cylinder head (Stage II Lindsey Racing Inlet Port + 28%CFM)
- New Valve springs
- Extrude Hone Inlet manifold + 15% CFM
- Standard Injectors
- Standard ECU, AFM, Coil & Dizzy
- SPEC Aluminium Flywheel (6lbs)
+0 ps because I think the AFM is limiting airflow more than the head or intake.

- Web Camshaft 274
+10 ps (like the Augment road race cam but that's actually dyno proven and I reckon cheaper).

- 951 Exhaust manifold
- 2" Thinwall Stainless exhaust system (1 Box)
+15 ps because the stock 2.7l had a cat.

Sum: 13+1.6+10+15=39.6 ps.
So from 152 ps to 191.6 ps (all flywheel).

On top of this removing the AFM would yield +10%, so 19 ps.
The webcam is good value in the $/ps sense. The rest is stupid expensive compared to going to MAF/MAP. I'm saying this, because you critisised it for exactly this reason. But you never realised that you spent more money for less gains...

Like I said, this is just my opinion. I'm sure you disagree. Good luck with your build and I hope you'll enjoy your car soon.

924srr27l

Ok, don't know about interchangeability ?



R

924srr27l

with the removal of the dreaded AFM ? That would be 4410 bhp?


R

V2Rocket

lighter crank and balanced pistons/rods don't make any more power...they just make the engine run smoother/rev faster, which still improves acceleration, but not actual power production.

924srr27l

Ok, but the actual gains must be to achieve this?

R

Ish_944

I never said they have no effect but you asked only for bhp estimate and that's what I did. Now you're complaining.

V2 is correct but you were not interested in such improvements when they were coming from newer electronics... So you're contradicting yourself.

odonnell

The math you did with the 951 AFM isn't apple to apples... on an NA car, you have engine vacuum on one side of the AFM and atmospheric pressure on the other. On a 951 you have a much larger pressure differential acting across the AFM opening due to the turbo cold side drawing through it. I also believe the spring is much stiffer to compensate for the larger flow volume when in boost.

Arominus

You should have just put a 968 motor in the car, you would have got a hot wire MAF with it and we could have avoided all of this. You also would be making 200hp at the rear wheels with no motor work @ sea level and for significantly less money.

good luck.

924srr27l

[QUOTE=Ish_944;12984002]EDIT: done

S
So either way 1900 will do me.........

R