So do I, but I believe DJ numbers tend to be much closer (although somewhat short) to actual bhp (not whp), and with good statistical reasoning.


I disagree. I can't vouch for the consistency/accuracy of one lone Dodge, but I can for many, many EVOs:

Factory rating for an EVO 8 is 271bhp.
A Dynojet shows ~235 whp = 13.3% loss
A Dyno Dynamics shows ~210 whp = 22.5% loss

- I believe the actual figure to be somwhere between these, but these percentage loss figures are for a stock EVO, and will diminish as power increases.


For my EVO in TME trim, the most statistically accurate average hp calculation method for my specific power range (determined by trap speed + mass) appears to be the Hale method, found here:

http://www.stealth316.com/2-calc-hp-et-mph.htm

The calculated bhp figure of 419bhp for my TME equipped EVO on 93 octane + methanol at that time seems reasonable, and is within 5% of a typical DJ figure (400+whp). That leaves a drivetrain loss of ~17% for the very low reading Dyno Dynamics , and a few percent less (i.e. 12-14%) for a typical Mustang at that power level. As for which dyno reports whp closest to the actual figures, my money is on a typical Mustang, which tends to be a bit higher than a DD, but significantly less than a DJ.

When I go back to the track and apply the same methodology, the percentage of drivetrain losses will be less still.

 

Hi, for the EVO ratings to my understand the 271HP is a manufacturer's advertised horsepower rating? IMO the manufacturer's rating is often influenced by advertising needs as well as political ones. Mitsubishi has been far from consistent between advertised HP numbers and actual power numbers. I think the only other "Japanese" company that is less consistent would be Mazda which frequently has to restate numbers. A more consistent company, such as Nissan, has a G35 Coupe (6-speed) and 350Z (6-speed). Although advertised at 7HP apart (I own both) they have virtually identical engines, mapping, transmission etc. and both torque and horsepower are almost identical at 210whp. From what I am told (unfortunately we do not own an engine dyno) the EVO is a bit under rated pushing over the rated 280HP. This would make a 210whp -> 280HP exactly that of 25%. That said, even at 271HP you must remember that at higher horsepower the drivetrain loss is not linear, and I still think in the 400-600HP for an AWD car, a 25% drivetrain loss is fairly normal. I in fact feel that a 25% calculation for those power levels to be a bit on the conservative side.

But nevertheless you are correct, the trap speed of a similar weight vehicle is a better determination of horsepower than just dyno numbers.

Gary
Gruppe-S

 

Oh I also wanted to add, some shops with the Mustangdyne AWD are running temperature corrections (weather station). Given say 20 degrees temperature difference you can see horsepower ratings differ by over 10% in certain instances. We leave the temperature correction off - it doesn't even come close to being able to simulate temperature differences and its effect on horsepower in the modern ECU car. I'm not sure what difference this makes at altitude, but we're pretty close to sea level.

Gary
Gruppe-S

 

Running the drivetrain faster through the gears in free space (plus tire friction) takes far lesser increase in power than pushing the vehicle to a 5-10mph faster trap speed. Due to this obvious fact, drivetrain loss is not a linear, fixed percentage of power, and constitutes a lesser percentage of power to turn that same drivetrain as engine power increases.


That implies it would require 800bhp to get 600whp worth of performance, and all it takes is a look at a compressor map and fuel injector capacity to see why this cannot be the case.

If it were, then the EVO that I saw delivering 440whp on a Dyno Dynamics with an ATP GT35R kit at 27 psi and 680cc/min injectors on race gas would never have been able to do it without running out of injector (and it didn't). By your estimation of drivetrain losses, that works out to 600bhp, but a 680cc/min injector running at a BSFC of a lean (for a turbo car) 0.50lb/hp/hr will reach their limit ~520bhp. Do you really believe this car was somehow making 600bhp?

My rough calculations using my own data as a statistical basis show actual bhp to be closer to 515bhp, which of course is far more believable given the flow rate of his injectors and the expectations of this turbo kit at 27 psi.


Which is why I cringe when someone pops in here and informs us how his turbo is making far more bhp than the compressor or injectors allow, all as a result of unrealistic drivetrain loss assumptions.

 

This would be a problem on non-loading dynos and not exhibited on loading dynos, the only major factors being either improper load formula and drag-coefficient.

Agreed there's no way any 4G63 will be able to do 440whp on 680cc injectors on our dyno regardless of fuel pressure. This would lead me to believe improper dyno calibration. To make 440whp on our dyno with C16 race gas on anywhere near normal fuel pressure levels you're looking at 880cc injectors. Full weight STI's which make 460whp on our dyno trap 128mph. According to the calculator you linked me (assuming driver weight), the HP is in excess of 630HP, which is right on the money for greater than 25% drivetrain loss. I guess each dyno is different (I have the video if you want)

Cheers,

Gary
Gruppe-S

 

i believe i have the exact setup you are looking for.
2.3 stroker
20g-9-5
revolver cams
alky
and all te bells and whistles.

on buschur's mustang dyno i put down 359whp and 408tor on 93 w/alky, at 26.5 psi. i originally was going to get the ex. manifold ported, but there was a mix up and it wasn't done. i put down around 400tor at approx. 3500rpms.

there is also still room in my tune to play around with.

check out the link for the dyno sheet.
http://buschurforums.com/forum/showthread.php?t=16606

 

so you are say you will never be able to make 440 whp on 680 injectors?

 

Here's the video of the STI:

http://video.google.com/videoplay?do...ru+impreza+sti

Please forgive the "advertisement" feel of the video. The dyno pull is legitimate, the last pull before going to the track, the graph is legitimate, and obviously the run speaks for itself. This is a full weight STI, minus the passenger and rear seats. No additional weight reduction was performed, assuming a 200lbs driver, I would say the car weighs no less than 3400lbs.

Cheers,

Gary
Gruppe-S

 

No, not saying this, just saying it will be virtually impossible to do so on our dyno while keeping fuel pressure normal. One of our customers is making 510whp with smallish (880cc) injectors... His solution was to bump his fuel pressure through the roof and run full steel braided lines. But without lines, it will be next to impossible to make 440whp with 680's.

Cheers,

Gary
Gruppe-S

 

Nice torque curve, that must be fun to drive.

Gary
Gruppe-S

 

ok not to jack this. I would like to know I have 680 injectors should l go bigger with my 20g 9 5?

 

Fletcher Jones Motor Cars.....used to here thier adds on the radio when I lived in Cali.....
here's what I'd do with an alky kit and tune:
https://secure.buschurracing.com/cat...82bc9623f419ce

 

Personally I'd run maybe 720cc's for the added head room if you're planning on running a lot of boost on the 20G, but I don't see the 20G making more than needing 680cc injectors on pump, and maybe some 720cc's in high boost applcations. We do have Helix 720cc instock though.

Gary
Gruppe-S

 

I suppose you wouldn't know one way or another unless you had seen it on your own dyno. As far as dyno calibration, while there is nothing to imply that his is calibrated any better or worse than yours, I do have enough experience with the performance of cars tuned with that dyno (which is tuned identically to Shiv's) to know that it certainly is no small feat to achieve 440whp.


With which engine management system?

The Fox formula (most accurate at those power levels) shows 585-595bhp. Given the relatively lesser performance of the STI vs. EVO, perhaps 21-23% loss for an STI at that power level is possible. I'm not nearly as familiar with STIs as I am with EVOs. Nevertheless, this doesn't rule out the possibility that your dyno may not be spot on.

 

Are we talking race gas or methanol injection?

Which engine management?