So cap roader and I (father son bonding event) decided to take the 2.7 Liter motor we just completed over the winter and see what it was putting out. Turns out it was doing everything we expected, but it was fun none the less. Couple of pics here followed by some links to videos on youtube.com. Enjoy all.
Dyno Run 1
Dyno Run 2
Dyno Run 3
Tis all for now.
Your numbers look fine for a 2.7 MFI car. Remember you are running on a chassis dyno...not an engine dyno. The HP and Torque numbers we're used to seeing are based on an engine dyno. With a chassis dyno you have to factor in the parasitic loses from the drivetrain. (I'm assuming that your numbers aren't already "corrected" to reflect true engine horsepower...I didn't see anything indicating that on the dyno sheet.) It's generally accepted that you need to apply a correction factor of plus 15-20% to numbers from a chassis dyno to get real engine numbers. Assuming that type of correction factor your true HP numbers are in the 207-216 range; Torque in the 201-210 range. You HP numbers are right in line with factory numbers. Your your torque is significantly up from the factory 2.7RS number of 188. Are you still using E cams? If so that's probably why your torque is a little higher than it would be with S/RS cams. Sounds like it will be a great driving motor.
Caproader here. Also known as "Pops" to Johannes356.
The engine was assembled with 'S' cams and an MFI pump rebuilt to 2.7RS specs. I thought about using E cams but figured that I would make it as close to an original RS motor as possible. That's why the compression ratio is only 8.5/1. However, the donor engine was from a sportomatic 73 E Targa and I didn't have the heart to paint the green engine shroud red.
Thanks for the thoughts on drive train and accessory power losses. I had the same thoughts.
Are there any correction factors for what in aviation is known as a "standard day"? Corrections for humidity, ambiant temp. and altitude above MSL? Or am I making too fine a point of things?
The well bonded capitalist roader
Cool !
Looks like great results ! I'm glad you posted this, I've been wanting to have mine dyno-tested just for my own knowledge.
Looks like a good place too, are the guys there pretty sharp? Are you involved or do they just take your car and go test it ?
Richard
Caproader,
Maybe we can get a real engine expert to chime in...but I don't think additional corrections for humidity, temperature, etc. would make a significant difference in your numbers...unless you were having the car dynoed at high altitude or unless it was a super hot day. High humidity might even help because the air is denser. At Bonneville (which is 4,200' altitude and often very hot) I've seen guys use an instrument for tuning that is used in avation. It takes those factors like altitude, humidity, heat, etc. into account and allows the engine to be adjusted to compensate for those factors...but I doubt in your dyno situation it would make much difference. It's great that you used "S/RS" cams. I saw your green engine shroud and just assumed you left the E cams in. In my experience the S cams are very much the way to go...especially in larger motors like 2.7's. For some reason there is a bunch of "conventional wisdom" around that says "E" cams are more drivable with a broader torque band, etc. I guess if you are driving your old 911 to work every day (doubtful) the E cams that would be true. But it's been my seat of the pants experience that motors with E cams really give up a lot of top end to motors with S cams...and with the added displacement of a 2.7 you don't lose much midrange power with S cams. I'm guessing your numbers would have been noticably lower in total HP and Torque with the E cams. Bottom line...sounds like you've got a great motor...and lot's of good motoring ahead.
R.
I must say that 175 at the wheels for tourque really doesnt leave me itching for E cams with "better low end tourque." I have heard that arguement many times myself, but this seems to be a good choice of a setup. Well done to pops.
As for the shop, pops can chime in with his own review, but we got wind of it because of a local vw group i belong to (got an 04 GTI 1.8t with chip and suspension... nothing major). They posted their dyno day on the website and we headed on over. Seems to be run by a father and his two sons (younger than I even). Kid seems to have a 944 he built up and is now selling and they had a 10 or 12 cylinder BMW engine in there I suspect out of an 8 series that he was planning on dropping in a 3 series
R.
As Wild Bill Hickock said when some one offered to buy him a drink at the saloon: "Sir, you speak the language of my tribe".
My thoughts exactly on the Cam issue. I figure that the extra displacement would give a sufficiently flat torque curve for my needs. It does come alive as the tach. passes through 5000 rpm. My son, Johannes356, and I are off to Putnam Park Indiana with a set of Toyo RA1's over Labor Week end for a DE to enjoy the new engine.
With respect to the humidity/temp correction issue: The more humidity the less effecient the engine becomes as hot and wet air is less dense than cold and dry air. The best day to test would be a cold winter day in Death Valley after a high pressure sysem blew all the moisture out of the air.
John
Hello: You may try a different muffler and check your O2 readings as well. If you tune on it I think you should be able to get a little more power. Play with the timing and fuel enrichment and see what you can get. On a last note there are better cams now than the S grind, that will yield more power and torque. It is fun to put the cars on a dyno though. Thanks Eric
My 73S 2.7 with PMOs put down right around 210 hp at the wheels on a Mustang Dyno.
There are differences on numbers between dynos of different makes but I believe a Mustang dyno usually runs on the lower end.
As Tony and Marco at TLG always say though, compression is the key with these motors.
Cheers,
Steve
Early 911S Registry #791
R Gruppe #404
69 911T Ivory White 2.9 "RGruppe'd" (SOLD)
72 911T Silver RS Replica SOLD
73 911S Silver 2.7 "Flares and Chairs" SOLD
Steve,
What compression ratio did you put into your 2.7 to get 210 hp at the wheels? Did you do any modifications, other than the PMO's, that make your engine different from a stock 73 RS? My 2.7 has the 8.5/1 P/C's.
John
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