cutout= loss of low end torque
11-13-2007, 12:28 PM
#43
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I picked up 6 more hp and 5 more torque on a dynojet. So i know that my duel cut outs help. Others have said similar numbers as well. Oh By the way my increase with he cutouts open was done on a car that already had a really free flowing exhaust
11-13-2007, 12:29 PM
#44
sorry dmoney06...close but no cigar. humans and engines vary in one very key way, our lungs can only ever work in one "direction," if you will, at once. we can only breathe in OR breathe out, never both at the same time. engines, on the other hand, can have both the intake and exhaust valves open at the same time, allowing air that should stay in the cylinder to escape thru the open exhaust valve due to lack of adequate back pressure keeping it in there until the valve closes. it is this lack of back pressure and subsequently escaping fuel air charge that causes the lack of daily drivable (low rpm) torque.
but at higher rpms, the lack of back pressure has the opposite affect; allowing more air into the cylinder due to lack of exhaust gas pressure trying to push the charge back thru the intake valve and into the manifold runers.
the overall net affect? with tuning, the power band will grow very slightly and move farther up the rpm range.
but at higher rpms, the lack of back pressure has the opposite affect; allowing more air into the cylinder due to lack of exhaust gas pressure trying to push the charge back thru the intake valve and into the manifold runers.
the overall net affect? with tuning, the power band will grow very slightly and move farther up the rpm range.
11-14-2007, 12:33 PM
#45
Tech Resident
That's the only argument here, thanks.
11-14-2007, 12:34 PM
#46
Tech Resident
Now that I have headers and 3.42's, the cutout will probably do a lot less damage or maybe even help me over the Corsa catback alone at the track. My argument is on a stock manifolds, aftermarket catback, 2.73 geared car. Now that my whole exhaust setup and gearing is totally different, I'm sure the story will be totally different. I need a tune badly, now, though.
I'm still very confident the cutout is costing me some grunt off idle around town, though. But I like the noise...
I'm still very confident the cutout is costing me some grunt off idle around town, though. But I like the noise...
11-14-2007, 12:38 PM
#47
Tech Resident
This thread is called "cutout = loss of low end torque," not "cutout = loss of peak torque." This is what I've been screaming but no one reads
11-14-2007, 05:55 PM
#49
((((((Administrator))))))
You're not understanding something. It doesn't matter if you picked up peak numbers. The fact is, the open cutout pushes the torque curve up in RPM's. Yes, you'll gain torque up high (which results in a gain in hp since hp is just a calculation of torque x RPM), but you'll lose it down low. Peak numbers mean nothing. Tell me your torque numbers at 1200 rpm's. I bet your dyno sheet doesn't show them.
This thread is called "cutout = loss of low end torque," not "cutout = loss of peak torque." This is what I've been screaming but no one reads
This thread is called "cutout = loss of low end torque," not "cutout = loss of peak torque." This is what I've been screaming but no one reads
Now I understand if you have a really free-flowing exhaust cat-back then sure a cut-out may not help out that much.
Peace,
Craig.
11-14-2007, 05:57 PM
#50
Tech Resident
How can you say that? You have nothing to compare it to. You can't say "zero loss of torque" if you have nothing to use as a benchmark. Give us a dyno of the car wit the cutout closed on the exact same day on the exact same dyno, and let's see it start from idle, not from 2000+ rpm's. Then we'll make a judgment.
