ptuomov

Ignoring standing start, this is basically the answer:

https://rennlist.com/forums/928-foru...no-graphs.html

Compute the average hp for the rpm range [x, 1.5x], picking the x that gives the highest average hp for that range. 1.5 is a round number that is not too far from the gear ratios.

Eyeballing: Your operating range (x that maximizes) is [4267,6400]. The average over this range is about 400 hp. Murphy's operating range is 4400-6600. The average over this range is something like 440 hp maybe. I am saying therefore that after the first gear shift, Murphy has a 10% advantage.

tveltman

For the record, note that excel (or at least older versions) is horrible at any sort of non-linear regression. Always check your equation by typing it into a cell next to the real values and look at the actual and calculated numbers side-by-side. If they don't look the same, don't be surprised. Excel is weaksauce. I've heard that the new excel has fixed this deficiency, and the one time I have seen it used for a polynomial, it did work, so YMMV.

Also excel can do the trapezoidal integration as mentioned above, it just takes a little formula work.

smith 928

They are not an apple to apple test Olsons is running 9.5 psi and Tim,s is running I think it was 15.6 psi .. Needs to be done at the same psi

tveltman

Not true. Lots of things differ from setup-to-setup, and the ability to run higher boost is dependent on compressor type and intercooler efficiency, etc. As long as both systems are the same level (i.e. stage III or best-available, or even, same price range), then it doesn't matter how they differ except where it counts -- in performance and associated metrics.

smith 928

I disagree. That is like saying a lambo is just like a corvette

tveltman

It depends on how you define it. If you are talking performance, then a lambo IS (approximately) a corvette. If you are talking overall power-to-dollar ratio, then a lambo is a POS compared to the corvette. If you are talking power-to-***-getting ratio, then the corvette is a POS compared to the lambo. Here, we are talking straight performance, and as I see it, that means the performance of the two systems compared side-to-side. We know empirically that they are similar, since the two installs perform similarly, and the question is mainly how does one predict and quantify this using published data.

IcemanG17

in a true apples to apples comparo both would be limited to the same PSI..but given the way each supercharger makes power...that is not feasible.... when both SC's are making the same boost, 9.5psi at about 4700rpm...they make nearly identical power-torque with an extremely small edge to the centrifugal blower.....which also makes sense since it is slightly more efficient...

auzivision

I think it is apples to apples in that both are trying to make max boost. Neither one is 'limited'. The anti-surge (centrifugal) or bypass (twin-screw) valve is there to aid with throttle off conditions. The twin screw design generates more boost at low RPM but can’t be geared up and spun like a centrifugal which creates more boost at high RPM.

ptuomov

Since everyone gets to define their own rules, everyone can be a winner!

Most hp out of stock long block? Win.
Most hp/$? Fail.

;-)

hacker-pschorr

You really need a new shtick, this one is getting old. You have more screen names in this place than I have posts.

How about Shane's 86.5 - same dyno @ correction factor
473hp/403tq @ 11.22psi

How about Jim Robert's GT (without an IC) - same dyno & correction factor
513hp/433tq @ 12.00psi

Maybe there is more to the tune in Tim's automatic than you realize or are able to comprehend.
Shane's car made more power on that day, it was dialed back before the final pull (shown above), without changing the boost.

Newsflash Mark - there is more to the HP/TQ numbers than boost. Maybe someday you'll realize this. You might want to figure this out before you start tuning your newly megasquirted car.


Here is the chart to refresh your memory:

-

Cosmo Kramer

Imre (Imo000) and I have a similar scenario. Our cars have similar performance (actually Imre has a bit of an advantage) and his car dyno'ed 48 hp less then mine, but he has a lot flatter HP curve and 25 lb/ft more torque. This coupled with an auto vs his 5 speed, my extra hp has no real advantage in the real world. I am now toying with maxing out my S/C impeller speed and adding a boost limiter valve set at 7 - 8 psi to aim for 400 rwhp from 5000 - 6500 with some added low end grunt.

ptuomov

This thread has all the ingredients for a big, heavy weight fight!

We've got it all! Tune. Boost levels. Knock counts. Dynojets. Torque vs. hp.

And the main event: Centrifugal, twin screw, turbo.

Laaaadies and Geeeeentlemen, aa-rr-ee yy-oo-uu rr-ee-aa-dd-yy?!

hacker-pschorr

Meh.....at the end of the day the fastest 928 is in the hands of Mark Anderson

AO

Wow! Cool discussion.

Had to start paying the bills right after I posted this.

What I was really trying to understand was whether peak, avg, or area was a "more" accurate way to compare engines.

All the points are generally excellent points (except for Turbo Mark - wasn't he banned?), and I guess it really does come down to how you define the parameters. Sorry my bad for not defining those more clearly.

As for the suspect equations, I didn't set the intercept at zero becasue you can't dyno the car from 0 RPM.

I'm still at work and need to go home and get some sleep, I'll revisit the thread tomorrow if I have time, or Friday when I will for sure.

IcemanG17

Really dyno's don't mean a damm thing.....its just a number guys can bench race with...... the only way to determine whose car is faster is to RACE.....the winner "might" have the faster car....or just is a better driver...

But whats funny is ALL of these 928's would loose a drag race against Anderson's racer...even Todd's mighty 675whp can't touch Andersons 500+whp in only 2600lbs... 5-1 power to weight is pretty good....