Cut-out only good for 4 HP
08-07-2005, 08:17 AM
#1
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Cut-out only good for 4 HP Dynoed the car last weekend and thought I would post some cutout info.My exhaust setup is tts long tubes,a kinda crappy ORY pipe, a 3 inch x 18 inch bullet, a QTP cutout, and a Dynomax ultraflow welded mullfer.
DISREGARD NUMBERS, dyno was quite low or my bad knock sensor was killing it.I did one pull 320 closed cutout and two pulls open.On both open runs I only picked up 4 hp.I can't find the dyno sheet right now so don't remember torque. The bullet can't be very restrictive so the muffler most be decent flowing to only get 4hp bypassing it. It doesnt bother me to much, bought it mostly for sound anyways.
For the record
dynoed 313, different dyno before Longtubes,pullies,ported tb,and cutout.
Just thought I would share some info.Probably why it doesn't feel faster and runs the same times at track open or closed.
Jay
DISREGARD NUMBERS, dyno was quite low or my bad knock sensor was killing it.I did one pull 320 closed cutout and two pulls open.On both open runs I only picked up 4 hp.I can't find the dyno sheet right now so don't remember torque. The bullet can't be very restrictive so the muffler most be decent flowing to only get 4hp bypassing it. It doesnt bother me to much, bought it mostly for sound anyways.
For the record
dynoed 313, different dyno before Longtubes,pullies,ported tb,and cutout.
Just thought I would share some info.Probably why it doesn't feel faster and runs the same times at track open or closed.
Jay
You might want to figure out what the problem is first before you set in stone that 4 rwhp gain from the cutout. 
08-07-2005, 05:30 PM
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No haven't tuned it ever.The headers have been on for 3 years now.I do have a po327, bad knock sensor light, so maybe that is killing the numbers.I don't really care about the 320 numbers,I know they are wrong but was curious to see what the cutout did.Heads and cam are going on in sept followed be a dyno tune.New knock sensor going in at same time.If I knew the wieght of my car I would use the calculator to guesstimate hp.
Jay
Jay
08-07-2005, 05:58 PM
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How much a cutout is going to gain you depends on how restrictive the normal exhaust is and also the power level you're at. I've got the SLP dual/dual and am bolt-on only now, and there is really a neglibile power difference between open vs. closed cutout. But once I put my cam in I expect there to be a power difference.
08-07-2005, 10:50 PM
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That knock sensor code needs to be fixed. It's a common problem with 98s and it's causing your car to run a maximum of 15* of timing, at least it did on my car. Pull the intake off, pop the knock sensor plugs off and i bet you'll see corrossion around the rear most knock sensor. I replaced both knock sensors and wiring harness with 02 stuff and the problem was fixed.
It's costing you power, but on the upside you can run 87-89 octane instead of 93 if you don't fix it. lol
It's costing you power, but on the upside you can run 87-89 octane instead of 93 if you don't fix it. lol
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08-08-2005, 03:32 PM
#11
The amount of power you gain with a cutout depends on where the choke point is in the exhaust and what kind of cam you're running.
With stock exhaust manifolds and cats, my car dynoed 411 rwhp through the SLP dual dual and closed cutout. When we opened the cutout, we lost 1 rwhp. This is because the manifolds were the choke point of the exhaust and not the cutout.
Next, we added Kooks headers and catted y-pipe. Made 431 through the Dual Dual and 433 through the cutout. Why? Because the Thunder Racing CheaTR cam is very insensitive to exhaust selection.
Finally, we replaced the CheaTR cam and added a cam with some overlap (231/234 112LSA). Made 444 through the Dual Dual and 455 with the cutout open. The additional overlap of the TRak cam made the motor more sensitive to back pressure.
With stock exhaust manifolds and cats, my car dynoed 411 rwhp through the SLP dual dual and closed cutout. When we opened the cutout, we lost 1 rwhp. This is because the manifolds were the choke point of the exhaust and not the cutout.
Next, we added Kooks headers and catted y-pipe. Made 431 through the Dual Dual and 433 through the cutout. Why? Because the Thunder Racing CheaTR cam is very insensitive to exhaust selection.
Finally, we replaced the CheaTR cam and added a cam with some overlap (231/234 112LSA). Made 444 through the Dual Dual and 455 with the cutout open. The additional overlap of the TRak cam made the motor more sensitive to back pressure.
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2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
