A 3" Cat-Back For Maximum Power Gains! Thermal R&D Bronco 2.7 Exhaust

[mrjking2000]

i'm sure you'll sell a ton of these but modified exhaust on anything less than a V8 just sounds like a fart can all the ricers run around town with waking you up at 2 AM. not for me.

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[Maharba]

I'm ignorant on how to read the dyno charts, so somebody learned correct me if I'm wrong. I see the information, but actually analyzing it properly is guess work for me.
Is that chart showing that it shifts base power up 500 RPM from 1500 to ~ 2000 RPM and then has a higher peak at ~3700 RPM? So essentially tighter power curve at loss of power at lower RPMs?

 

[nolimits]

I'm ignorant on how to read the dyno charts, so somebody learned correct me if I'm wrong. I see the information, but actually analyzing it properly is guess work for me.
Is that chart showing that it shifts base power up 500 RPM from 1500 to ~ 2000 RPM and then has a higher peak at ~3700 RPM? So essentially tighter power curve at loss of power at lower RPMs?

Red lines represent “baseline” HP and torque curves. Blue lines represent modified HP and torque curves.

The lower curves show the HP comparison. The vertical axis shows amount of power (HP or torque, depending which exact curve you look at), whereas the horizontal axis shows at what RPM the power is being made. Although not labeled we know the lower curve represents HP because in the upper left corner the dyno result shows 261hp baseline and 282hp modified which correlates with the peak curves of the lower set.

The upper curve is the same, except for torque.

While the results do technically show a 20hp gain, that doesn’t happen until about 3700ish RPM’s when the blue line crosses over on top. In lower RPM’s the red line (baseline) is actually making more HP & torque so adding this exhaust hurts your low end power but shifts the gains to the high end. So if you hammer down and are full throttle then you should see benefit. Most people don’t drive that way though under normal circumstance.

The result is somewhat skewed though because the baseline isn’t a stock unmodified vehicle. It has Roush components which may/should have increased power & torque. Those parts may benefit more greatly from the additional flow than stock parts so the 20hp gain is likely less. And since we don’t see those gains until 3,700ish RPM I would then question if you are taking a bigger hit on the low end below 3,700rpm.

Short version, you give up low end for some top end gains. It’s probably less than 20hp and sound is subjective. I loved my 392 Hemi but a turbo 6 cylinder doesn’t really get me all revved up.

 

[HarmCityHammer]

Not a fan of that dip in HP / TQ below 3.7k, which is interesting to me. I understand that with NA cars you want some back pressure to help with cylinder scavenging, but I was always under the impression that with forced induction less back pressure is always better. Can anyone explain why a freer flowing exhaust would reduce low end power in this application?

It’s almost like it wasn’t in the same gear. The run starts at different RPM.

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