355C Dyno?

306 hp at the wheels is a bit low on a dyno jet, especially for a Challenge car with 2.7 Motronic.

It is no mystery that that stock 355 2.7 cars show 340 to 350 hp (at the crank) on a dyno jet and
5.2 cars 320 to 330 hp.

 

This is a dyno sheet from my F355 (5.2 Motronic):
The red curve shows the performance with the Dual-Exhaust-System from Capristo (329hp at the wheels)
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Heres one from Aircon in Oz. 240kW is around 340 Hp.

http://www.pless.com.au/355dyno.jpg

 

240 KW = 326 PS
240 KW = 321 HP

at the wheels ?

 

When I dyno'ed my Cobra on the same dyno you used I also remember getting a bumpy torque curve. I suspect it has a lot to do with their pick-up.

I think NASA uses a smoothing factor of 4, at least for the GTS class. If you need to submit the dyno run you might need to reprint it changing the factor. If MER gave you the file you can download the dyno software off the web, change the factor, and reprint. I have the software loaded on the PC at the Villa if that helps.

 

I am surprised no-one has said this - don't compare results from different dynos.

That said, the bumps for the torque are an artifact in the readout - if the torque was really doing what the graph says, you'd hear it, feel it, and the HP graph would follow the same bumps, as HP is TQ x RPM.

The best way to determine what is the cause of any power deficiency (if indeed there is one) is to have an exhaust analyzer running during the dyno run.

I suspect that all is well unless the mixture is out OR the cam timing is out. A common problem....

 

I can't resist.... As you may or may not know, we (Ricambi) have some pretty sexy pistons and liner sets for the 355. One of our customers has these in his car and hopes to have it dyno'ed in the next day or 2. There will hopefully be 2 cars done at the same time. Both are 95 2.7s, one recently rebuilt using all OEM parts and the other rebuilt using the Ricambi/Sharpe-Roberts pistons, rings, liners and valves. Both engines were rebuilt by the same engineer and meticulous records have been kept of what has been done to each engine. The seat-of-the-pants dyno indicates a very significant difference. We are itching to get the numbers though...... The customer will be publishing the dyno results here for all to see.

Dave

 

exactly! same car, different dyno, different numbers.

 

321.84hp

yes. at the wheels.

 

The top right corner of the printout says 'SAE Smoothing: 5'. Changing that factor changes the algorithm used to create the dyno graph. I think it determines how data is interpolated from the reading. A greater level of smoothing will flatten out hp peaks and such. I do know for GTS they told us the specific smoothing factor to use so we are all consistent.

Oops .. I just looked at the dyno run I submitted and I am also at a '5'. I have to redo my own!

 

Very true, but I will say that I have dyno'ed two cars on the same dyno in question here and got readings exactly where I thought they would be. Given the lower than expected numbers on the pull, getting an understanding of where it 'should' be is a good place to start before trouble shooting.

 

fair enough...makes perfect sense.

 

intersting thread....
I'm especially interested in LAB DATA on the pair of stock and hot modded motors....
When delivering these cars when new, it was disclosed to us by an FNA representative that the '96 cars had to be re-geared as the power loss from the 2.7 '95 version cars made this be required to keep accelleration close....true story
We noticed immediately the "loss" of 1 of the air mass meters. We didn't even yet have the workbook supplements to differentiate the 5.2 Motronic versions!
Power is down-period.

A wide band pumping cell would help as to stochiometrics at play-remmber that 5.2 is a "nonadjustable" eeprom, so mixture is not likely at issue unless running too fat from a leaking pressure regulator on the fuel rail(dummy light should be on regardless of model and version)Whilst the 2.7 utilizes 32 pin motorola eproms-which are frequently "re-blasted."
One must always consider the possibility of poor cylinder sealing as a result of blown out intake valve guides. I've done guides as soon as 9100 miles, and as late as 51,000...and everywhere in between.
A Leak down while hot is required-forget compression tests on Ferraris, any real information will come from a differential pressure leak down-just like aviation...a compression tells you only that there is a heart, not the true health of the heart's beating.
Lastly, it must remembered that cam timing is a real problem in this era...I've had severak LATE version F-40s who had 350-400ish on dynos, and when the cam timing was corrected(it is always the same mis-timed camshaft!) it was nearly 100HP and an owner who honestly wanted to know if the motor had been rebuilt...honestly, it makes that much difference.

 

I agree cam timing is critical to these motors performing properly and so many of them out there are timed incorrectly or have just had the asembly marks lined up by shops or technicians cutting corners or attempting to undercut the competition. We found 30 HP at the wheels on a 430 Challenge with a new engine installed into it. Making small camshaft timing correction really woke the motor up.