There's really no reason to bring the rpm's up to launch. The converter will flash to the same rpm either way. Stab it off of or slightly higher than idle. No need to stall it all the way to 2500 or whatever the converter will hold. Sounds like you need a vacuum accumulator though, raising idle won't do anything if you're seeing this happen at 2K.
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Originally posted by DarkSS View PostThere's really no reason to bring the rpm's up to launch. The converter will flash to the same rpm either way. Stab it off of or slightly higher than idle. No need to stall it all the way to 2500 or whatever the converter will hold. Sounds like you need a vacuum accumulator though, raising idle won't do anything if you're seeing this happen at 2K.
And the reason you raise idle is because that's when the brake is applied. The reason he's pulling through the brakes is because of no vacuum down low then revving up to even less vaccuum. On cammed cars sometimes if you bump idle up it will produce more vaccum.
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Before the cam and after we installed the stall, I was getting my best times at 2200 or above. Tried launching at an idle and the times were not as good by tenths. I now creep forward at about 1800.
Jim
Sent from my iPhone using TapatalkL99 to LS3 Conversion, Speed Inc Comp Cam, SLP LT Headers, Corsa Exhaust, Roto Fab CAI, FAST 102 Manifold, Nick Williams 102 TB, FAST Fuel Rails, Yank 3400, 3.91 Gear and TrueTrac, BMR Suspension, Foose Wheels, Heritage Grill
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I launch at 1500. Any higher and I was worried about doing a burnout because of the street tires.'13 Camaro SS/RS Blue Ray Metallic w/silver stripes, Auto, Rear Vision Package w/camera, Embroidered Console, Blade Spoiler, sunroof.
Mods: Dyno Tuned by Nickey, Nickey Comp Cam, Fast 102 Intake manifold w/ported TB, Yank 3200 Stall, CNC Ported Heads by Nickey, Kooks Headers, Borla S-type axleback, Nickey Noweeds diverters, 3:91 gear with 1000HP axles, CAI air intake, Foose Legend wheels.
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Originally posted by SYCK SS View PostNot all torque converters will flash the same. Plus stabbing it off idle could shock the tires too much. We see this with the jeeps I build big time. Pending converter style and setup, it's better to get the fluids flowing on a taller stall then to leave it empty. Sure on a stock stall or lower one I'd agree. But in Jims case it would benefit him to be able to bring RPM up at launch
And the reason you raise idle is because that's when the brake is applied. The reason he's pulling through the brakes is because of no vacuum down low then revving up to even less vaccuum. On cammed cars sometimes if you bump idle up it will produce more vaccum.
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Originally posted by SCOTCH MAN View PostBefore the cam and after we installed the stall, I was getting my best times at 2200 or above. Tried launching at an idle and the times were not as good by tenths. I now creep forward at about 1800.
Jim
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The Yank is a 3400 Poweradder not an SS
Jim
Sent from my iPhone using TapatalkL99 to LS3 Conversion, Speed Inc Comp Cam, SLP LT Headers, Corsa Exhaust, Roto Fab CAI, FAST 102 Manifold, Nick Williams 102 TB, FAST Fuel Rails, Yank 3400, 3.91 Gear and TrueTrac, BMR Suspension, Foose Wheels, Heritage Grill
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Originally posted by DarkSS View PostJust reading his mod list as a "Yank 3400" I am assuming it's an SS model like John runs and what I had. These are tighter converters made to be more street friendly. At his power level I would assume the shock to the tires wouldn't be that extreme.
If the vacuum is bleeding off at 2K, raising the idle won't do much. Like it was previously stated, a vac canister is the best bet. I would first look for a vacuum leak anywhere. I have seen a lot of LS' run some huge cams like the Trex and MS3 and never have a vacuum issues since the vac is pulled from the back of the intake.
And his vacuum isn't bleeding off at 2000rpm. He doesn't have vacuum at the time when the pedal is depressed. Naturally when opening the throttle plate more the vacuum drops regardless of cam.
The issue again is jim is depressing the pedal at IDLE. Where vacuum is reduced.
Raising idle on a lopey cam and playing with timing adjustments can increase vacuum. If you only add 100 - 150rpm and reduce the "lope" vacuum is produced easier. But as jim says he's like the lope as does anyone else.
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Originally posted by DarkSS View PostThat's a nice concept expect that the vacuum is taken from the back of the intake on a LS, not a the TB.
Scotchman, just look for a vacuum leak. It's not going to hurt anything and it won't cost you a penny.
Plus the MAP sensor is just behind the throttle body and I have the logs from the track. His vacuum is reading "normal" for a low idle, cammed car.
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Arguing with you is like pissing in wind. LS1tech would benefit greatly from your knowledge.
I'm suggesting looking for a vacuum leak first because countless of LS cars have installed donkey dick cams and never had a vacuum issue. Up the idle then get back to me. I guarantee you it won't do a damn thing.
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Originally posted by DarkSS View PostArguing with you is like pissing in wind. LS1tech would benefit greatly from your knowledge.
I'm suggesting looking for a vacuum leak first because countless of LS cars have installed donkey dick cams and never had a vacuum issue. Up the idle then get back to me. I guarantee you it won't do a damn thing.
So the fact your information is based purely on "forums" says alot.
His vacuum at idle is between 13-16inhg. Pending operating temp, ambient temp, etc.
His idle is very low which amplifies the "lope" that Jim likes. Not having a smooth idle with a cam like Jims will produce low vacuum.
It was much more pronounced on old school small blocks and big blocks because too. Vacuum pumps were very common back in the day to compensate for weak vacuum due to these issues.
If you read back I said raise idle and adjust tune. It's not just bring the RPM, but play with timing to reduce the lope. That will increase vacuum.
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Originally posted by SYCK SS View PostThere is no vacuum leak. It's been looked over by a shop on here.
So the fact your information is based purely on "forums" says alot.
His vacuum at idle is between 13-16inhg. Pending operating temp, ambient temp, etc.
His idle is very low which amplifies the "lope" that Jim likes. Not having a smooth idle with a cam like Jims will produce low vacuum.
It was much more pronounced on old school small blocks and big blocks because too. Vacuum pumps were very common back in the day to compensate for weak vacuum due to these issues.
If you read back I said raise idle and adjust tune. It's not just bring the RPM, but play with timing to reduce the lope. That will increase vacuum.
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Jeremy
I did a quick test. Stopped the car, put it in neutral, ran the RPMs up, put the brake on to the floor, put it in drive , ran the RPMs up to 3000 and NO MOVEMENT. I want to do this a couple of more times but this is progress.
Proves your thinking on idle and vacuum.L99 to LS3 Conversion, Speed Inc Comp Cam, SLP LT Headers, Corsa Exhaust, Roto Fab CAI, FAST 102 Manifold, Nick Williams 102 TB, FAST Fuel Rails, Yank 3400, 3.91 Gear and TrueTrac, BMR Suspension, Foose Wheels, Heritage Grill
Paint by Countryside Customs
Built and Tuned By Speed Inc.
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