All these mods and only 1 HP gain?

[JANNETTYRACING]

Originally Posted by musclecargirl

First, some background:

Two years ago, had my STOCK car (L99) dyno-ed.
Temp was in low 80s, humidity was 4%.

Two weeks ago, had my modified car TUNED (engine and transmision) and dyno-ed. Dyno shows I gained 1 HP and 15 ft. lbs torque.
Mods include:
- After market intake.
- Shorty headers.
- Highflow Cats.
- Catback exhaust.
Temp was low 90s and humidity was approx. 40%.

Real happy about the increase in torque. A little surprised by the HP results.

The shop attributed the lack of HP gains on the dyno to the temp and humidity. They suggested I bring the car back when the temps are lower and the humidity is lower for another dyno (which I plan to do).

I'm sharing this for a couple of reasons:
- I don't have the knowledge to either agree or disagree with the explanation provided for the HP dyno results. I'll know for sure when I take it back in about 2 months.
- Let others who might be considering mods/tune know to be careful about setting realistic expectations of what those mods/tune will get you (if you're expecting HP gains).

I'm happy with the mods and the tune. The car finally sounds like I want it to and the AFM is gone! Haven't driven it enough yet to know if there's any noticable impact on gas mileage.

If you've had a similar or different experience, I'd be interested to hear about it.

Depending on Brands of Products, unsure on the Aftermarket intake.
Could gain or lose power.
The shorty headers do Nothing except look Pretty
The high flow cats are worth about 10-12 RWHP
The Cat Back again depending exact set up can do From nothing to hurting HP and torque.

This also is consistent with what we see, GM did not leave much on the table as far as HP is concerned ,these car make pretty close to all the Dyno Horsepower they can with the stock tune. but feels completely different on the street plus all the other benefits of custom tune.

The Humidity and Temp definitely affect ACTUAL HP and Torque produced.

If you were on the same dyno the Correction factors should take the Weather out of the equation.

[honeybucket99]

Noticed ur in Fayetteville. Hey neighbor:updown: Who did u go to to tune/dyno?

[fielderLS3]

Temperatures and humidity probably affected it.

Also, compare the entire graph, not just the peaks. Often tunes and mods like yours will give you the biggest gains off peak at lower and mid-range RPMs.

[musclecargirl]

Originally Posted by honeybucket99

Noticed ur in Fayetteville. Hey neighbor:updown: Who did u go to to tune/dyno?

Went for the tune because I couldn't take the ADM any more. I disliked the AFM from the day I brought the car home. It was very noticeable to me even with the stock exhaust. I primarily drive in the city so was hearing the AFM constantly on/off.

Now that the AFM is gone, I realize even more how bad it was.

I thought about trading for a manual but, I'm attached to this one (I know, sounds silly).

[Shu71]

Dyno's, good ones, should have a correction factor that is figured based on temp, barometric pressure, humidity, etc. SAE and STD are two different methods of measuring power. That is the cause for the similar results after many upgrades, most likely. Did the shop give you the dyno file, not just the printout? If you have the actual dyno logged file you can download their software and change the SAE STD and get a better apples to apples comparison. IIRC SAE is typically around 2.6% less. Some tuners or shops selling parts that are quite as honest as they should be may show you a before using SAE and then an after showing STD to show larger gains on paper to make the customer think they got more. OR watch to make sure they do not override the weather inputs. ALWAYS demand the actual run files so you can use the dyno manufacturers software to analyize your real results.

[Tampa Tuning]

The high flow cats probably did more than the shorty headers.

These manifolds flow pretty good. I cant say it enough, Dont skimp on your headers.

Everything you do between the two headers are dependant on the headers to get the air out of the motor. it becomes more and more evident the more you do to the motor.

[musclecargirl]

Originally Posted by Tampa Tuning

The high flow cats probably did more than the shorty headers.

These manifolds flow pretty good. I cant say it enough, Dont skimp on your headers.

Everything you do between the two headers are dependant on the headers to get the air out of the motor. it becomes more and more evident the more you do to the motor.

Going for long tubes next.

[musclecargirl]

Originally Posted by Shu71

Dyno's, good ones, should have a correction factor that is figured based on temp, barometric pressure, humidity, etc. SAE and STD are two different methods of measuring power. That is the cause for the similar results after many upgrades, most likely. Did the shop give you the dyno file, not just the printout? If you have the actual dyno logged file you can download their software and change the SAE STD and get a better apples to apples comparison. IIRC SAE is typically around 2.6% less. Some tuners or shops selling parts that are quite as honest as they should be may show you a before using SAE and then an after showing STD to show larger gains on paper to make the customer think they got more. OR watch to make sure they do not override the weather inputs. ALWAYS demand the actual run files so you can use the dyno manufacturers software to analyize your real results.

Good info. Thanks for sharing. I will be much more knowledgeable next time.

[Scott@Bjorn3D]

89 degrees 336.72 HP 336.98 TRQ

Only modes VMAX, TB and CAI Intake. Shorties are really only for sound. Vengance told me add long tubes and tune I would be in the 360-370 range. I am going to save up for longtubes, cam and LS3 conversion. They said that would get me to the 420 to 440 range at the wheels.

[Anthony@RWHP]

Originally Posted by musclecargirl

Hope I got this right. First dyno was STD second was SAE.

Like SHU said. Theres an additional 2-4% correction with STD over SAE regardless of weather correction. (they're both weather corrected) Your car "dynod good" the first time because they used STD. Your numbers were probably 10-15 hp lower than the sheet they gave you. Your first "347" dyno was really 335 ish. Your new 348 number is a correct number. Torque was probably off 10 fl/lbs too. In reality, you probably gained more like 13hp and 25 ft/lbs which sounds a little more realistic.

The stock L99's that I dyno here are closer to 320hp/335 ft/lbs. Typically with just tuning and a cai we see 345hp/355 ft/lbs. We've found little to no gains with a catback (besides noise) and shorty headers have made little improvement. We've see 10-15 with the long tubes we've installed here.

We just recommend a CAI and a tune. It yields the best hp/$$$ we've found.

[SGOS252382]

[QUOTE=musclecargirl;3726092]Hope I got this right. First dyno was STD second was SAE.

For the numbers to be accurate the same corrrection factor would need to be used.

STD numbers are corrected to 60 degrees, 29.92 pressure, 0 humidity
SAE numbes are corrected to 77 degrees, 29.23 pressure, 0 humidity

For this reason, SAE numbers are lower than STD numbers.

[Jason 98 TA]

I have tested "high flow cats" & shorties with very little gains. I expect best case from that combo is 5rwhp. The cold air on the other hand should work for you.