Pelican Parts Forums - I want 225hp, how to get there?

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- - I want 225hp, how to get there? (http://forums.pelicanparts.com/porsche-911-technical-forum/1121231-i-want-225hp-how-get-there.html)

Quote:

Originally Posted by garment (Post 11724500)

I just did a top end on my ‘83SC with stock CIS and SSIs. Worn valve guides, high oil consumption, and not being able to keep up at Ruchlos Rallye last year finally made me pull the trigger.

Went with 3.2 P&Cs from Mahle, 10:1 compression, 964 cams, lightened flywheel, heads redone, new valves all around, cam towers honed and decked, rods re-bushed, everything except splitting the case as mentioned. My wrench pulled a rod, declared the crank good, and sealed what we needed to on the case.

Night and day results, super happy with the power all thru the range. Really felt the results about 700 miles into the break-in, and still getting better about 2,000 miles in. Almost no oil consumption. And plenty of smiles to go around. Plus, no problem keeping up at this year’s Ruchlos.

Good luck with your rebuild.

Curious about 10:1 on single plug with 91 octane. Keep reading that's not ideal, but then see folks keep doing it and seem happy with it. What's the nuance I am missing? Thx

P&Cs came from pelican. Most of the other parts were sourced by my wrench

https://www.pelicanparts.com/More_Info/PS98015.htm?pn=PS98-015-M362&q=ps98

I’m not too far from Summit Point, and the heads and cam towers were redone there. I dropped the engine and brought to my wrench, which he appreciated due to space constraints at his shop. While I had the car at my place I did a couple of things like replacing the worn engine skirt and getting the rear bumper repainted (it was off anyway, right?

PM me and I can share shop names if you’re ok with shipping parts for refurbs.

Quote:

Originally Posted by Hulley (Post 11724801)

Where did you buy the components and did your shop do all the work or send items out for machining?

I see P/Cs Patrick motorsports and LN sells P/C with Nikasil liners.

Any recommendations?

BTW, I've rebuilt a few engines but not an aircooled Porsche engine so there's a bit of a learning curve.

Quote:

Originally Posted by Jonny042 (Post 11724547)

The "at the wheels" number could be disappointing if you aren't prepared to do a little math, And if your dyno guy hasn't set up the correction factor for the atmospheric conditions.

Depending on the dyno and the operator, it could be valid to apply a correction factor to the base reading. SAE standard J1349 specifies the standard conditions for testing to be 77 degrees f, 0% humidity, and 29.23inhg barometric pressure.

I recently had Project Heavy Metal dyno'd and it was 85 f, 38% humidity and 29.1 in hg pressure. This gives a correction factor of 1.033

The 240Hp reading at the wheels on that day corrects to 247.96 standard.

The J1349 standard also allows for 11% drivetrain loss which would give me 275Hp. Generally people use a 15% number instead so that would be 285Hp.

Enough about my car - in your case, depending on the weather the correction could be 5% or more. So it's possible the 170 at the wheels could be as much as 180 and the flywheel Hp number is over 200Hp.

Shouldn't you add the SAE 3.3% correction factor to the 11% SAE drivetrain factor and arrive at a 14.3% correction, and therefore almost the same as the "standard" 15%? 240*1.143=274.32 vs 240*1.15=276 (either of which is damn nice power). It seems that you may have corrected (15%) the corrected (3.3%) number rather than the uncorrected wheel number (240*1.15).

Most dynamometers worth their salt already correct for atmospheric conditions using the SAE J1349 standard. So, unless correction is disabled, no post test factor should be added.
Additionally, never, ever, ever, add driveline loss factors to the result of a test performed on a DynoJet dynamometer. DynoJet has been adding a pseudo driveline loss correction factor to ALL test results since DynoJet built their first dynamometers. Its a total BS result, always reporting inflated numbers, which of course made for very happy customers lol! It's a black-box factor, that DynoJet devised when testing their first motorcycle chassis dynamometer with a Yamaha V-Max. Yamaha advertised 130 HP (approx) at the time for the V-Max, but the original DynoJet reported 90 HP! So Mark Dobeck, founder of DynoJet, came up with a BS factor, that to this day is based on the original testing of the Yamaha V-Max! Crazy.
I worked for a dynamometer manufacturer for 15 years, manufacturing a wide range of engine and chassis dynamometers. Those BS DynoJet reports were the bane of our existence!
The bottom line is, if you want accurate flywheel HP numbers, test on an engine dynamometer.....

My wrench asked about that too. We have 93 octane where I’m at, which I use exclusively. Don’t perceive any issue with this.

Quote:

Originally Posted by thetorch (Post 11724905)

Curious about 10:1 on single plug with 91 octane. Keep reading that's not ideal, but then see folks keep doing it and seem happy with it. What's the nuance I am missing? Thx

Tom
As someone involved with racing series rules and balance of performance to create classes with some parity between models, dynos are of particular interest. My personal experience with my local Dyno-Jet guy is that the sheets I, and my buddies, have gotten are the rear wheel hp/torque figures. The only corrections were "SAE corrected," which I assume were for altitude/barometer (ambient listed on the sheet), and temperature (also listed), and "Cf=1.20" - which I don't understand - coefficient of friction on the drum?)."

Some amateur racing organizations rely on Dynojet figures for BOP purposes. Leaving aside the variables inherent in a drum dyno (like how tight the restraining straps are cranked up), are you saying all Dyno-Jet figures have a built-in drivetrain loss figure?

I always figured that I get to add whatever drive train lose figure I want when trying to compare my engine to engine's whose HP is at the flywheel.