My HP and Torque numbers... people said they're low?

[MustangThief]

For the HP mods I have listed with my long tubes + O/r h-pipe + mufflers when i dynoed it the guy acted like mine was really low for my exhaust mods.... i was confused... i thought it racked up right where i thought it would be?

Mods+numbers are in the sig, dunno, what do you guys think?

 

[SilverGTV8]

Hmmmm.... It seems a little low, I would have expected you to be over 250, like 253ish. Not a ton.....OH I know why.....

GEARS, screw up dyno numbers, The car will make less power with gears. Not really by it doesn't dyno right because you are not at a 1-1 ratio in 4th anymore. You car is probably right on the numbers because of the 4.10s.

I expect to dyno 250ish with my gears instead of upper 250s.

 

[caballo]

Is that really a problem?

I would think that information would be input to the dyno for proper calibration?!

Not sure but....

 

[SilverGTV8]

Yes that is it. The math involved to make the 1-1 ratio would be intese and have to occur at every rpm. The car dyno's much easier because of the gearing. It's not an issue and you are only talking a couple of HP.

Peak numbers aren't important anyways, its the rest of the curve that is. Peak numbers are like buzz words.

I have seen many under power cars by peak numbers trounce cars with 50-60 peak HP more.

The curve is important not the peak number per say.

 

[trinity_gt]

GEARS, screw up dyno numbers, The car will make less power with gears. Not really by it doesn't dyno right because you are not at a 1-1 ratio in 4th anymore. You car is probably right on the numbers because of the 4.10s.

I disagree. The ratio with the factory 3.27s wasn't 1:1 either.

Moving to 4.10s increases hub torque by 25.4% and decreases wheel RPM by the same factor. In the equation for HP at the wheels,

HP = WheelTorque * WheelRPM / 5252

the percent increase in wheel torque is exactly offset by the percent decrease in wheel RPM. This is one reason why trap speeds with gears usually vary little from stock even if ET drops a bit because the car digs out of the hole better.

MustangThief, I did you get air/fuel ratio info with your pull? This was on a Dynojet, right? What were the conditions and the correction factor, if any, that was applied? Can you post a plot? As Silver says, peak numbers only tell part of the story...area under the curve is much more important.

 

[jstreet0204]

Gears will make it read slightly lower, there was a write-up posted a while back that explained why. It had something to do with the way the lower gears spin the drum up faster, while others claimed there is slightly more drive train loss due to lower gears.

Don't get too caught up in dyno numbers. Use it to guage you own progress, but you can't really compare different cars on different dynos on different days when you are talking about 5 to 10 hp differences.

 

[Rocketman]

Wasn't 99 the first year of the PI head and the factory horse power rating wasn't the ususal 260 that we see on the rest of the PI cars. Seems like I remeber the 99 numbers being a little lower?

 

[JonJon]

Wasn't 99 the first year of the PI head and the factory horse power rating wasn't the ususal 260 that we see on the rest of the PI cars. Seems like I remeber the 99 numbers being a little lower?

I don't remember ever hearing that.

 

[mrvax]

The 1:1 thing has nothing to do with dyno "loss". 1:1 I believe means 1 turn of the engine results in 1 turn of the driveshaft. This usually occurs in 4th gear or "DRIVE" for an automatic.

I have also read about a few rwhp being lost with lower gears on a dyno. It ain't much.

MustangThief: You definatly need to post up your air/fuel ratio. This can really affect your results.

 

[Red35th]

If you don't like your numbers, go to a different dyno on a different day.

Dyno numbers are all relative. With the exact same mods I dynoed 10hp higher in Dallas than in Alabama (both corrected on a 248C and with a hot car).

In other words...don't be dissapointed.

 

[SilverGTV8]

The PI(winsor) heads in 99-early 01 had lower compression and didn't make 260 fly Hp but the tranny was more efficent (sp) then the tranny in late 01-04 mustangs. late 01-99 PI(romeo) have higher compression.
A 99 5spd will dyno the same as a 04 5spd because of the tranny drivetrain loss difference.

 

[DBMSTNG]

The PI(winsor) heads in 99-early 01 had lower compression and didn't make 260 fly Hp but the tranny was more efficent (sp) then the tranny in late 01-04 mustangs. late 01-99 PI(romeo) have higher compression.
A 99 5spd will dyno the same as a 04 5spd because of the tranny drivetrain loss difference.

the 99-01 GT's do infact make the advertised 260hp at the flywheel. and they are Windsors not Romeos. the Romeo PI engines 01.5-04 make more than 260hp at the flywheel. Ford just didn't change the hp rating because it wasn't a substantial increase.

 

[twogts4us]

Don't get too caught up in dyno numbers. Use it to guage you own progress, but you can't really compare different cars on different dynos on different days when you are talking about 5 to 10 hp differences.

SO TRUE - words to live by!

 

[modmonster]

These guys are right about peak power is not of too much importance when you have a solid power curve.

 

[CanadaStang]

248hp isn't too shabby with your mods. You may be able to squeek out a bit more depending where your a/f is, but it's still not bad.

 

[Jones331]

[

The curve is important not the peak number per say.[/QUOTE]

Elaborate a little more on this please.......jj

 

[trinity_gt]

Elaborate a little more on this please.......jj

The area under the curve describes how much work the engine do overall much better than a single value in the entire RPM band. On paper, a 240HP Honda S2000 engine and a 260HP 4.6L modular would seem to be comparable if one only looks at the peak HP number but in reality, we know these are quite different engines in terms of their suitability for their intended use.

If the torque curve down low fattened up nicely (say, 15-30 ft-lbs or something) but the power peak stayed relatively constant, that would be a great, great thing on a street car, right? But if you focus only on the peak numbers, you totally miss the valuable gains obtained down low.