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k@rlos
Samba Member
Joined: October 04, 2012
Posts: 485
Location: Suffolk, England
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 Posted: Tue Jul 20, 2021 9:58 am Post subject: Launch rpm |
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| Bit of a random question I know but what kind of rpms are people launching with using a 2 step at the drag strip? |
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Mattatat
Samba Member
Joined: October 29, 2010
Posts: 41
Location: 303
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| Posted: Tue Jul 20, 2021 10:18 am Post subject: Re: Launch rpm |
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| I go about 6800 or so. |
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King_vw61
Samba Member
Joined: February 03, 2018
Posts: 1383
Location: Southern California
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| Posted: Tue Jul 20, 2021 11:44 am Post subject: Re: Launch rpm |
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2300 pound car and I leave at 6600 on a 8” drag radials
On the street I drop it to 5500. Same tires
_________________
1961 Ragtop, Autocraft 2783cc for street/strip 10k miles and counting...230.84 HP to the wheels thru Muffler 13.4 to 1 on E85
https://www.instagram.com/king_vw61/?hl=en |
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k@rlos
Samba Member
Joined: October 04, 2012
Posts: 485
Location: Suffolk, England
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| Posted: Tue Jul 20, 2021 1:19 pm Post subject: Re: Launch rpm |
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| Thanks, this weekend will be the first time I launch using the 2 step. I’ll start at 5500 and see how I go |
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NJ John
Samba Member
Joined: September 21, 2007
Posts: 2222
Location: HdG, MD & NJ
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| Posted: Tue Jul 20, 2021 1:22 pm Post subject: Re: Launch rpm |
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When I had my 1400 drag buggy with a gusseted case rancho and a spool. 8000 rpm on the launch with a two step. That’s was suggested Sam at rancho at the time. That was a 2180 with a welded pinned roller crank. Still have it.
I’m putting that same msd in a street turbo bug and have no idea what I’ll be launching at.
_________________
1973 standard, yellow, lowered, 3” narrowed front, 1600 blo-thru turbo w/single dell 15.4@86, so far
11.41 et buggy. Long gone
Let’s go O’s! Let’s go O’s!
https://www.youtube.com/@AirSpooledGarage |
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jpaull
Samba Member
Joined: February 22, 2005
Posts: 3462
Location: Paradise, Ca
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| Posted: Tue Jul 20, 2021 1:59 pm Post subject: Re: Launch rpm |
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| is this in a bug? and what type of tires are you running? |
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k@rlos
Samba Member
Joined: October 04, 2012
Posts: 485
Location: Suffolk, England
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| Posted: Tue Jul 20, 2021 2:31 pm Post subject: Re: Launch rpm |
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| jpaull wrote: |
| is this in a bug? and what type of tires are you running? |
Bay Bus with regular road tyres |
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babysnakes
Samba Member
Joined: August 19, 2008
Posts: 7106
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jpaull
Samba Member
Joined: February 22, 2005
Posts: 3462
Location: Paradise, Ca
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| Posted: Tue Jul 20, 2021 4:23 pm Post subject: Re: Launch rpm |
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| k@rlos wrote: |
| jpaull wrote: |
| is this in a bug? and what type of tires are you running? |
Bay Bus with regular road tyres |
You might not get any high rpm launches on standard tires, 2 step or not. Playing the traction game on street tires is best done with letting the clutxh out at 3500 and roll on the gas if fully hooked
_________________
[email protected] MPH 1/4 Mile & 8.1 @ 83.7MPH in 1/8 Mile with Mild Type 1 VW Mag Case 2234cc commuter engine in stock weight bug w/only .491 total lift(CB2292 Cam), 42x37 heads, 48idf's, Street tires, Belt on, Mufflers, Pump gas, video of the run here: https://youtu.be/M3SPqMOKAOg
Transmission by MCMScott:
Rhino case, Klinkenberg 4.12, Superdiff, 002 mainshaft with 091 first idler. Weddle 1.48 Third & 1.14 Fourth. |
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[email protected]
Samba Member
Joined: May 17, 2003
Posts: 4863
Location: Harmony, PA
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| Posted: Tue Jul 20, 2021 6:05 pm Post subject: Re: Launch rpm |
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| jpaull wrote: |
| k@rlos wrote: |
| jpaull wrote: |
| is this in a bug? and what type of tires are you running? |
Bay Bus with regular road tyres |
You might not get any high rpm launches on standard tires, 2 step or not. Playing the traction game on street tires is best done with letting the clutxh out at 3500 and roll on the gas if fully hooked |
^^^^^this^^^^^
Before everyone started suggesting 6600-8000 rpm launches, a little description of what driveline mods were done to accomplish this to their vehicles, and questioning what the op has to start with would be better.
A stock 70 002 “3 rib” is going to go about 5 feet with a 6k launch before it cleans off the teeth of the 3.80 first gear, the 5.38 ring & pinion, the spider gears, or all of thee above. If you have few modifications to your transaxle, don’t “launch” at all. Let the clutch out slow like grandma, then ease into it once moving.
k@rlos, what do you have for a transaxle? At bare minimum you would need a 3.78 1st, a 5.42 r&p, and a four spider diff. Better yet, an 091 with the four spider diff.
A Bay Bus is going to be a challenge to leave cleanly. I would start low rpms, around 2000, and work up. My street tire 2180lb Superbeetle with 114hp at the wheels worked well around 3800. It’s been as low as 3200, and as high as 4400 dependent on traction compound, and temperatures. When you find the happy medium, a couple hundred rpm up/down will ruin it. |
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k@rlos
Samba Member
Joined: October 04, 2012
Posts: 485
Location: Suffolk, England
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| Posted: Tue Jul 20, 2021 11:10 pm Post subject: Re: Launch rpm |
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It’s a built 091 with all weddle internals and a super diff and a mid mount that I fabricated as earlys only that the engine bar and front gearbox mount as you well know. I’ve not run the bus on the track for a long time and do have slicks but they are in poor shape from standing. Not looking to break records, just too have fun really. And like I say first time using the 2 step function on the Mallory ignition.
Sorry fella’s, I should have added a bit more info really  |
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[email protected]
Samba Member
Joined: May 17, 2003
Posts: 4863
Location: Harmony, PA
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| Posted: Wed Jul 21, 2021 6:10 am Post subject: Re: Launch rpm |
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| k@rlos wrote: |
It’s a built 091 with all weddle internals and a super diff and a mid mount that I fabricated as earlys only that the engine bar and front gearbox mount as you well know. I’ve not run the bus on the track for a long time and do have slicks but they are in poor shape from standing. Not looking to break records, just too have fun really. And like I say first time using the 2 step function on the Mallory ignition.
Sorry fella’s, I should have added a bit more info really |
It sounds as if you have things covered.
I’ve cleaned up too many foolish monkey see, monkey do instances of carnage to give out advice without getting a little more info.
It’s going to come down to what jpaull mentioned. Getting a 2700+lb Bus going from a stand still with a street tire is definitely going to take some track time. A common thing to do is to lower tire pressure to maybe 18-20psi to increase the contact patch, but with the height/mass of the Bus, this may make it unstable going down the track at speed.
Other things to think about are the spring plate bushings, and axles. Type 1 vehicles have a tendency to move the spring plates fore/aft in the stock rubber torsion grommets under hard acceleration. Does anyone make urethane, or bronze bushed spring plate covers for Bay Buses? Since you have considerably upgraded the internals of your transaxle, the half shafts May now become the weakest link. Having separate grease, and a dry, assembled half shaft as a spare may get you home in a pinch.
While I’m not one to really condone stuff on the street from witnessing too many idiots run out of talent, a back road test, or two on dry unprepped pavement may get you closer to your target rpm for the first time down the track. |
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NJ John
Samba Member
Joined: September 21, 2007
Posts: 2222
Location: HdG, MD & NJ
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| Posted: Wed Jul 21, 2021 9:12 am Post subject: Re: Launch rpm |
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Yeah, ignore all info that I provided. Lol
_________________
1973 standard, yellow, lowered, 3” narrowed front, 1600 blo-thru turbo w/single dell 15.4@86, so far
11.41 et buggy. Long gone
Let’s go O’s! Let’s go O’s!
https://www.youtube.com/@AirSpooledGarage |
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k@rlos
Samba Member
Joined: October 04, 2012
Posts: 485
Location: Suffolk, England
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| Posted: Wed Jul 21, 2021 10:33 am Post subject: Re: Launch rpm |
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| [email protected] wrote: |
| k@rlos wrote: |
It’s a built 091 with all weddle internals and a super diff and a mid mount that I fabricated as earlys only that the engine bar and front gearbox mount as you well know. I’ve not run the bus on the track for a long time and do have slicks but they are in poor shape from standing. Not looking to break records, just too have fun really. And like I say first time using the 2 step function on the Mallory ignition.
Sorry fella’s, I should have added a bit more info really |
It sounds as if you have things covered.
I’ve cleaned up too many foolish monkey see, monkey do instances of carnage to give out advice without getting a little more info.
It’s going to come down to what jpaull mentioned. Getting a 2700+lb Bus going from a stand still with a street tire is definitely going to take some track time. A common thing to do is to lower tire pressure to maybe 18-20psi to increase the contact patch, but with the height/mass of the Bus, this may make it unstable going down the track at speed.
Other things to think about are the spring plate bushings, and axles. Type 1 vehicles have a tendency to move the spring plates fore/aft in the stock rubber torsion grommets under hard acceleration. Does anyone make urethane, or bronze bushed spring plate covers for Bay Buses? Since you have considerably upgraded the internals of your transaxle, the half shafts May now become the weakest link. Having separate grease, and a dry, assembled half shaft as a spare may get you home in a pinch.
While I’m not one to really condone stuff on the street from witnessing too many idiots run out of talent, a back road test, or two on dry unprepped pavement may get you closer to your target rpm for the first time down the track. |
Thankfully where I live in the U.K. there is an abandoned US air base and runway about 2 miles from my workshop which I’ve often played about on in various vehicles.
Thanks for your input, greatly appreciated |
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stealth67vw
Samba Member
Joined: January 22, 2004
Posts: 1852
Location: Grass Pants, Orygun
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| Posted: Thu Jul 22, 2021 8:12 pm Post subject: Re: Launch rpm |
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Usually around 6,000-7,000 rpm on 2 step. M&H 215/65 DOT slicks, built type 1 4.12 gearbox with 3.78 1st/091 idler still rubber mounted. 1.64 60 foot at 16psi tire pressure. The car is 2,000lbs with me.
_________________
John Bates
JB Machining Services
1967 street Bug 2276 w/ 48 IDAs, 2020lbs with driver
7.76 @ 89.55mph 1/8 mile
12.34 and 108.10 mph 1/4 mile |
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