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vwracerdave Samba Member
Joined: November 11, 2004 Posts: 15278 Location: Deep in the 405
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Posted: Thu Jul 23, 2015 10:06 pm Post subject: Exhaust experment |
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I have a 78X90.5 = 2007cc, CB 40X35.5 044 Magnum heads with home porting, W-120 W/1.25 rockers, 8.6 CR, 44 IDF's with 34mm venturies, and 1 5/8" exhaust. I bracket raced this engine last week in my 1345 Lb. dunebuggy and ran 14.10's shifting at 6400 RPM. I am going to switch to a 1 1/2" header with no other changes and race the Buggy this weekend.
Any guesses if it will run slower or faster? what do you think? _________________ 2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Featured in Dec. 2001 HOT VW's Magazine page 63
Watch my racing video's http://www.youtube.com/user/okvwracer/videos |
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GTV Samba Member
Joined: March 27, 2004 Posts: 2084 Location: Si'ahl
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Posted: Thu Jul 23, 2015 10:09 pm Post subject: |
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I think slightly slower ET but driveability will be slightly improved.
It would be interesting to test 36mm venturies as well.
It runs out of breath by 6400?? _________________ EMPI Power Rules! |
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jpaull Samba Member
Joined: February 22, 2005 Posts: 3456 Location: Paradise, Ca
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Posted: Thu Jul 23, 2015 10:13 pm Post subject: |
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My guess is that there will be a different variable that will dictate a change in your ET. Air density with slight change of weather, or traction for that particular run, etc.
Jeff _________________ [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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mark tucker Samba Member
Joined: April 08, 2009 Posts: 23937 Location: SHALIMAR ,FLORIDA
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Posted: Thu Jul 23, 2015 10:38 pm Post subject: |
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quicker but with possiably lower mph. but home porting can be many things, from mild to wild so...let us know how it does. I would think the low cr would like the smaller tubes. |
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FreeBug Samba Member
Joined: March 12, 2012 Posts: 4278 Location: deepest, darkest Switzerland
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Posted: Fri Jul 24, 2015 2:08 am Post subject: |
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It should shift the torque curve max down a few RPM, probably flatten it out with a little less at the top, but as to how that would translate into your ETs and trap times, I have no clue.
Please share the results of this experiment, enquiring minds want to know. |
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Mikedrevguy Samba Member
Joined: October 15, 2008 Posts: 2233 Location: Medford, OR
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Posted: Fri Jul 24, 2015 7:01 am Post subject: |
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Where are your 60' times?
With my 2007 DRD L-5 heads CNC ported- DRD 298 cam w/1.25s (equivalent to the fk8) 44's with 36 vents. In full bodied 74 super(2100lbs)
1.5 header w/stinger I've run 1.9sec 60' with 14.59 ET @ 93mph shifting at 6000
Last weekend swapped to the 1 5/8 still managed 93 mph, but had a tough time hooking up and 60' suffered. (Street radials)
Are you looking to lower your shift point? _________________ 74 1303 (RevBug): plan for German Look
76 914 with 2260
79 VW Iltis
69 Bwajaja
"The wise speak because they have something to say; while the foolish speak because they have to say something." Plato
Illigitimi non-Carborundum!! |
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vwracerdave Samba Member
Joined: November 11, 2004 Posts: 15278 Location: Deep in the 405
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Posted: Fri Jul 24, 2015 5:56 pm Post subject: |
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GTV wrote: |
It would be interesting to test 36mm venturies as well. |
Already tested. It runs faster with the 34mm venturies. _________________ 2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Featured in Dec. 2001 HOT VW's Magazine page 63
Watch my racing video's http://www.youtube.com/user/okvwracer/videos |
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Mikedrevguy Samba Member
Joined: October 15, 2008 Posts: 2233 Location: Medford, OR
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Posted: Fri Jul 24, 2015 7:00 pm Post subject: |
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What's your jetting at, Dave? _________________ 74 1303 (RevBug): plan for German Look
76 914 with 2260
79 VW Iltis
69 Bwajaja
"The wise speak because they have something to say; while the foolish speak because they have to say something." Plato
Illigitimi non-Carborundum!! |
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MURZI Samba Member
Joined: August 25, 2005 Posts: 5063 Location: Madisonville, La
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Posted: Fri Jul 24, 2015 8:17 pm Post subject: |
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Have you ever shoved a wideband on that engine? _________________ 62 vert
2276
Tim’s welded heads
45 Dells
A1 sidewinder
Fk44 cam |
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fivelugshortaxle Samba Member
Joined: May 13, 2011 Posts: 4254 Location: Aumsville, Oregon
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Posted: Fri Jul 24, 2015 10:33 pm Post subject: |
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Just watched your videos, Dave. That Ghia sounds bad ass _________________ Good things come to those who wait.
2332 with lots of goodies....
Rotating assembly balanced by Brothers VW
4340 84mm crank
AA 94mm p&c' s
Total seal 2nd ring, rest are Grants
5.5 h beams
Magnum straight cuts
Steve Long XR310 on a 106
CB 1.4 rockers
CB Magnaspark 2 distributor
NGK D7ea plugs
A1 lowdown 1 3/4 with single muffler
Dellorto 48's with 40 venturies
Kennedy Stage 2 with Daiken disc |
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mark tucker Samba Member
Joined: April 08, 2009 Posts: 23937 Location: SHALIMAR ,FLORIDA
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Posted: Sat Jul 25, 2015 10:25 pm Post subject: |
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well????????and did it change the jetting requirements? |
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vwracerdave Samba Member
Joined: November 11, 2004 Posts: 15278 Location: Deep in the 405
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Posted: Sun Jul 26, 2015 8:37 am Post subject: |
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Made it to 3rd round and got my ass kicked on the tree.
Engine with 1 1/2" header ran .20-.25 slower ET and 1-1.5 less MPH. That was pretty much what I expected to happen. 60' were the same. All I did was change exhaust no other tuning. Weather was close to the same both weeks. Maybe I might get another 1/10th out of it if I rejetted and tuned, but this is my spare engine and coming out and replaced with the 2165.
_________________ 2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Featured in Dec. 2001 HOT VW's Magazine page 63
Watch my racing video's http://www.youtube.com/user/okvwracer/videos |
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mark tucker Samba Member
Joined: April 08, 2009 Posts: 23937 Location: SHALIMAR ,FLORIDA
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Posted: Sun Jul 26, 2015 9:21 am Post subject: |
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might need to be shifted sooner. but it was a good test if all else was the same. how about weather? 2 or 3 cheezzee burgers before running I expected the lower mph,but not realy the lower et. although it is quite different than driving on the street/road corse. were they both the same header just diferent size?
on another note....3rd round is better than 2nd round loss wiytch is better than a 1st round loss witch is always better then loading up a crashed/broken car. a good day at the races is driving back on to the trailer. a great day is with a trophy.awesome day has a check/cash in your hand good work mr dave. |
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maui Samba Member
Joined: May 16, 2004 Posts: 438
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Posted: Mon Aug 24, 2015 1:27 pm Post subject: |
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I say jus put 36 vents and jets only and it will be better times and for regular driving you just adjust your driving habits. Not a big deal. |
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