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We went to a place that has a dyno with the Dutch 928 club and did a testrun. 223 horse and 372 nm. Anybody that has a clue what these numbers mean? For me it sounds pretty good, it’s 17 horse less then factory and actually 22 more nm torque! 45 years old car?
Did they give you the actual chart? Does it show which correction factor was used?
Automatic or manual?
Which gear did you use?
Oil / Coolant / trans fluids all up to operating temp?
How many pulls did you do?
Does your 928 have any mods?
Chassis dyno's measure power at the wheels, most folks use 15% for manual, 20% for automatic as the power loss through the drivetrain. Using this formula for a manual would be 204hp. But the correction factor used (SAE, STD, uncorrected etc..) can drastically change the number.
The most important use of such numbers is if you plan on modifying the car and do an after dyno on the same dyno and note the differences.
@belgiumbarry yeah, that i what I was wondering, if some experienced dyno/tuning guys know what the numbers translate to tuning wise. I tuned the car myself (with a lot off help from this lovely forum) and got it to run "good" with a CO meter a while ago. So this might be just a bit too rich, could make sense!
There's some good info across the bottom of that chart, trying to decipher it.
Bottom line is this, you have a absolutely beautiful 928 and just looking at the chart, it's very healthy. The actual numbers are really not all that important unless you plan on making modifications and tracking the changes.
The US cars at least, can pick up some good power with a few more degrees of timing. That's where a dyno is really useful. Strap it down, warm it up, do a couple of pulls - add a degree - do a couple more pulls... rinse / repeat until you find that sweet spot in the power curve.
As I recall, dyno operators in Europe give you "corrected" crank numbers.
DIN correction? "CF Geen" of 1.032? (But "geen" means "no" in Dutch.)
But the "Driveline eff(%)" of 92% is too optimistic? Estimated from roll-down? Should be more like 85%?
Only difference ROW vs. USA, 78-79 is EGR? Cams are the same.
yes, those are crank numbers , and driveline loss is normaly measured during roll-down.
Torque is in NM , not ft-lb. Also the scales used on the chart are so that it is as "visual" presented as possible.
This was my latest run with the C2
same chart but in FT-lb and scales that the cross point is at 5250 rpm ( some prefer this )
last time i went with the 928 , it was way to rich and had no jets to change.... i also mounted foam air filters on the Webers which the engine was eating away !
All changed now , almost ready for a new dyno test
Last edited by belgiumbarry; 04-09-2024 at 04:00 AM.
There's some good info across the bottom of that chart, trying to decipher it.
Bottom line is this, you have a absolutely beautiful 928 and just looking at the chart, it's very healthy. The actual numbers are really not all that important unless you plan on making modifications and tracking the changes.
The US cars at least, can pick up some good power with a few more degrees of timing. That's where a dyno is really useful. Strap it down, warm it up, do a couple of pulls - add a degree - do a couple more pulls... rinse / repeat until you find that sweet spot in the power curve.
Hi, not really any plans…it was a nice thing organized by the Dutch 928 club. The guy from the dyno was impressed. Normally the club groups are bragging upfront and claiming to have the most powerfull cars. This group was very modest but the results were good or even better then expected
I might do some further tuning and keep in mind these numbers and the idea of Barry that it might be a bit rich…but it runs fine and don’t want to mess up things…
Ah, that makes sense. One of the dyno's in town here can do that, I haven't played with it and they typically only do wheel power for customers.
Holy Cow, what did you do to that engine?
this one has a ( 2006/7 ) 540 Merlin engine with the oem Tripower on it. A guy ( RIP ) in Arizona build it that way ( with a 6 gear Richmond gearbox )
I bought that car in Germany , at a dealer who imported it.
Had a lot of work in wrenching and tuning it , but finaly it works fine. ( Engine , coilover suspension, R&P steering etc... )
Here it runned to rich , meanwhile i corrected this and think there is 500 HP.
But as it is our "cruiser" i won't do no more dyno pulls as gearbox and ( oem ) diff can't handle that torque on paper.
It's a monster going on the pedal !
this one has a ( 2006/7 ) 540 Merlin engine with the oem Tripower on it. A guy ( RIP ) in Arizona build it that way ( with a 6 gear Richmond gearbox )
I bought that car in Germany , at a dealer who imported it.
Had a lot of work in wrenching and tuning it , but finaly it works fine. ( Engine , coilover suspension, R&P steering etc... )
Here it runned to rich , meanwhile i corrected this and think there is 500 HP.
But as it is our "cruiser" i won't do no more dyno pulls as gearbox and ( oem ) diff can't handle that torque on paper.
It's a monster going on the pedal
That's badass. I grew up in the Corvette world, good friend has been restoring / racing them since the 70's. When "dyno days" started to become a club thing about 20 years ago, he would always talk the big block owners out of strapping their cars down since they would always be disappointed. As I'm sure you know. a 1967 435hp 427 was "gross" HP and they'd be lucky to see 200-250 on a chassis dyno.
That's badass. I grew up in the Corvette world, good friend has been restoring / racing them since the 70's. When "dyno days" started to become a club thing about 20 years ago, he would always talk the big block owners out of strapping their cars down since they would always be disappointed. As I'm sure you know. a 1967 435hp 427 was "gross" HP and they'd be lucky to see 200-250 on a chassis dyno.
correct , i had a fresh rebuid "350 HP " '70 C3 years ago and on dyno ( on that same dyno ) had exactly 240 HP
That Merlin here now is called a "735 HP " ... probably 500 if tuning perfect .
But OK , i would love to have that HP/torque in my rally 928
04-07-2024, 03:56 PM
‘79 on the dyno results
