So I think the Mustang Dyno was reading high.

Please have a look at my two almost identical 1/4 mile runs today. I was in the left lane both runs

13.839 @ 101.61 in Sport mode WITH traction control @ 84 degrees F

13.876 @ 100.43 in Sport mode withOUT traction @ 86 degrees F

Both runs relative humidity 6, Absolute Barometer 29.84 and 29.94

Gross vehicle weight GOOGLE says is 3924 + little ol me 140= 4064 lbs

Is 3924 lbs curb weight correct??
The online HP calculators Horsepower Calculator say that my flywheel HP would therefore be exactly 370,

370 at the flywheel, exactly what is claimed from the factory.....EXACTLY what is claimed from the factory...

I had no traction issues, the car launched without wheel spin the same with and without traction control. Without I aggressively rolled into the throttle as much as I feel I could have, so I can't say any time was lost because of traction (it was a sticky track)

So, these #s are as close as possible to the stock 370 at the flywheel....yes?

Since these two runs were almost exactly the same, and I had no traction issues and the car felt strong (though faded a bit at the end of the 1/4, probably from heat build up), I consider them a solid baseline to start from.

Let the floodgates of debate now open

What do you all have to say?

 

Be happy that a 10 year old car with 54K on it has still got the same number of horses as when it left the factory?

 

HP depends on the calculator it seems.

If I use this one:
Calculate HP with HP Correction - Wallace Racing

1st run:
Your HP is 320 from your ET
Your HP is 342 from your MPH
Your HP Correction Factor is 1.03
Your Grains of water is 10
Your DA (Density Altitude) is 1,667 feet
Your Altitude Density Index is 95.2 percent

2nd Run:
Your HP is 325 from your ET
Your HP is 358 from your MPH
Your HP Correction Factor is 1.03
Your Grains of water is 11
Your DA (Density Altitude) is 1,796 feet
Your Altitude Density Index is 94.9 percent

I used the 4203 value you used before you edited the post (and 40 feet eleveation for just in case).

 

I'm not sure what the actual weight is for stock curb weight. Anyone know?

The elevation was 60 feet, so pretty close to sea level.

Anyway, the point being is that I think this shows the actual HP numbers are closer to the stock 370 than the dyno showed, which I now think was quite high. AVOS, if you use the edited weight, I think your numbers would jive better with the stock HP and 1/4 mile times given from the factory. You may want to re-do those calculations to remove my weight error. Then tell us what you get.

I think the stock 1/4 mile is 13.7, so my 13.8 is ballpark given my slowww reaction times.

Can we all agree (as if) now that the HP figures are somewhere close to the stock 370 claims?

 

It depends on the calculator you use (and what sort of drivetrain loss, but most use 17% from what I have seen). If you put in a lower weight, your hp will go down of course, just follow the link and try it out.

I would now confront your dyno shop with these figures, and ask them to get to the bottom of why their figures where so much off (or did they show a calculated engine HP? That would be closer). If they work on it you have a good dyno shop, otherwise look for another one.

 

Agreed

I also have to say actually running the 1/4 mile is fun!

 

I compared your 13.876 run against mine 13.604 one:



60ft -0.08
330ft -0.03
660ft +0.05
1320ft +0.27

So, I had more traction problems ( slippery track ) but a bit more power to get 3.8MPH higher end speed ( 101.61 vs 105.41 ). My car makes just 345hp from the flywheel at 5200-5400rpm, but power and torque comes up at low rpm because of bigger lower pulley and some other modifications. When everything will be ok, I think power and ET should be quite a much better.

 

With bigger lower pulley and other mods, don't you mean 345 rear wheel HP?

 

I meant 345hp from the flywheel. That was already at 5200rpm most probably because current air intake/filter or additional ECU tune do not work perfectly with the other modifications. Maybe at bit more when run up to rev limiter next time. Flywheel torque 409ft/lbs at 3470rpm.

 

Wow, so there must be something seriously wrong. Stock HP is about 370 + 30-40 for the lower pulley +what other mods

So your motor is 50 or so HP down from stock even with your mods?

Are you running a hot air intake? Where did you get this tune? What other mods do you have?

 

Well being a 1/4 mile guy and as such I know you NEVER use ET as a number to try and figure out horsepower, MPH is king and always should be used. Way to many factors come into play with ET. I can show you a timeslips from my 99 camaro tht I built a Z06 427 LS7 for making round 550 rwhp and on one I ran 11.8 at 126.5 and one where I ran 10.6 at 127 thts a pretty big gap between and still had the same MPH. Now if you use this calc here Horsepower Calculator, calculate hp from et, trap speed, calculate tire diameter, mph and rear end ratio. and put in my raceweight of 3980 and put in my mph you get almost an identical dyno confirmed 553 but you put in my 11.8 run you get 397 but put in my 10.6 run and its right at 547 so theres way to much crap to deal with when it comes to ET

Either way glad you had a good time and thats all that matters, at least unlike some you go out and show what you can can do. I too love to take my car to the track and race otherwise whats the point of upgrading these cars?? Cus yeah it may be cool to have alot of power but if you never use it really no point. If your street racing you are not only a fool but have a complete disrespect for people on the road, their familys, and public safety, so cant use it there. If your a dyno queen well then once again whats the point thts like marrying a playmate model but never banging the hell out of her. So congrats on the run and glad to see the racing bug bite ya woot woot im going after i get back from the fields nxt time

 

I think he means rwhp hes from finland and maybe not understanding only way to get an exact flywheel number is on an engine stand. Once again too many factors come into play 17% is a guesstimate all these guys tht are out there with their (*** flywheel) number in their sigs are morons and are guessing at these numbers cus you have so much tht is sucked up by trans, tire friction, rearend friction, an the list goes on. The only way to know what the engine is making is put it on an engine dyno run the sucker with all assessories and then record numbers install the motor in the car and run it on a good reliable dyno and get that number and subtract and you will have more of a realistic number, but your still plagued by the car dyno having to many factors to get a truely accurate number. So in the end track is where you gunna show what your car can do. But the stock car for its time, hell even for now a days, is a quick car low 5 second sec 0-60 mid 13 1/4 mile all with decent mileage and a heavy car very impressive already.

They only want to put those numbers there in their sigs to inflate their own egos. Why i dont know especially if your not out there racing and flogging the car to show what it can do and enjoying the power you worked so hard for. If the plan is to work so hard an spend so much tine and money making an already quick car even quicker shouldnt the plan also involve racing an showing what all that hard work an money went for?? if not I say just leave it b maintain it nice and drive it as if came lol.

 

Copy from the dyno paper: Max power to shaft: 257.6kW - you are right, not from flywheel

 

OK, so you are making more power than stock, that was what I was hoping.

Yes, then when you get traction (buy some "cheater" slicks tires) your times will be significantly faster.

Later, when I have more power, I will need to upgrade my tires. I'm most probably going to run Toyo R888 265 35 18s in the rear. These are fabulous summer grip tires.


and XJR-0220, yes, everyone at the track says it is the MPH that tells the story, not the ET

 

Most of the ET calculators are probably tailored for drag racers who use slicks or drag radials and assume you're getting good 60' times. If we were to use sticky tires, then the ET hp calculators would be more inline with the correct horsepower. Therefore, as been said plenty of times, the trap speed is the better indicator.

 

I was waiting for about 430-440BHP and low 13s ET + 107MPH ( street tires and + irfiled track ) before my dyno and 1/4mile, but real data was showing that something has to fix before get these numbers. Arden made 422BHP/595Nm with additional ECU, cats and catback ( new car 11 years ago ). I have a bit more mods but 106K miles engine.

 

Maybe I missed it somewhere but it might help to indicate exactly what model/year car you have.

Doug

 

its a 2002 jaguar XJR

 

I think, he meant put it in your signatures...

 

Now wheres the fun in that