Serious Top end speed needed!

jbbugs · Posted: Tue Dec 06, 2011 7:58 am Post subject: Serious Top end speed needed!

Image may have been reduced in size. Click image to view fullscreen.

Check out the track layout for the 14-Hour ChumpCar roadrace coming up on May 27th!

We're currently running a Stock-geared 3.88 IRS trans in my 73' Super Beatle, and are topping out around 105mph. I'll be stepping up to a .82 4th gear, but it will obviously not be enough on a track this Big.
Should be a blast anyway!
www.chumpcar.com
_________________
Drag bus! http://www.youtube.com/watch?v=s2MOVmKdhX4

58' double-door panel
57'tubeframe dragbug
73' Super Beetle CrapCan roadracer
and an 04'F150 to tow them with
Contrary to popular Samba Folklore, the 010 is Not the sliced bread of VW distributors
www.jbbugs.com

mcmscott · Posted: Tue Dec 06, 2011 8:08 am Post subject:

Run a 3.44 r/p with a .82 fourth, you just better have enough grunt to pull it!

Eaallred · Posted: Tue Dec 06, 2011 8:16 am Post subject:

What rpm are you hitting at 105mph? Are you limited by engine rpm limits, or is that where it runs out of power? If the engine is just out of power at that point, gearing taller will probably just slow you down.
_________________
Eric Allred

10.29 @ 131mph
Utah's fastest and quickest VW.

Aircooled.Net
Blackline Racing (Formerly ACE)

mcmscott · Posted: Tue Dec 06, 2011 8:17 am Post subject:

^^^^ Agreed

Eaallred · Posted: Tue Dec 06, 2011 8:19 am Post subject:

Reason im saying, is I hit just over 130mph in a stock geared trans with a 4:12 ring and pinion. Was doing about 6200rpm on a 26" tire.

I don't see 6200rpm as being too high of an rpm to hit at the track, just wondering if the car is only pulling up to 105. If so, you just need more power, I think you have the gearing to do it (3.88 ring and pinion in there already,right?). That track is not all high speed, there's some 'slow' turns in there as well.
_________________
Eric Allred

10.29 @ 131mph
Utah's fastest and quickest VW.

Aircooled.Net
Blackline Racing (Formerly ACE)

mcmscott · Posted: Tue Dec 06, 2011 8:26 am Post subject:

A "stock" 3.88 trans has the same final drive as a 4.12, r/p times fourth gear, due to the .94 fourth verses the .89, you still should be able to hit higher top speeds tho

markhuebbe · Posted: Tue Dec 06, 2011 9:29 am Post subject: Re: Serious Top end speed needed!

jbbugs · Posted: Tue Dec 06, 2011 9:35 am Post subject:

I'm currently running a 14" Falken Azenis 615K tire with a diameter of 22.75". It's the only size 14" tire they offer. We LOVE the tires, as they stick like glue, and have held up fine during 24, and 14-hour races.
I'm sure a taller tire would help a bunch, but for now I'm stuck with the 14" wheels.(I have a number of them for spares). I've dynoed the motor at 110hp at the wheels running 91 octane w/8.0CR. To keep the fuel costs down, we're having to stay with pump gas, as we burned 130+ gallons during the 24-hour race.....Fuel ain't cheap! Shocked

It also has to LAST for 14-24 hours w/o damaging itself....Keep in mind, this IS Endurance racing
We tend to top out around 5,700 rpm's in 4th gear. We're getting killed on the long straights, but can hold our own against most of the field in the shorter, third gear turns. I expect some of the faster cars to see 140-150mph at Daytona. I'm sure we can't get up to those speeds. We'll have to stay low on the inside and point them by for sure.
I'm considering a 3.44 R&P, but I'm worried it might hurt us in the shorter turns. Anybody got a cheap 3.44?
_________________
Drag bus! http://www.youtube.com/watch?v=s2MOVmKdhX4

58' double-door panel
57'tubeframe dragbug
73' Super Beetle CrapCan roadracer
and an 04'F150 to tow them with
Contrary to popular Samba Folklore, the 010 is Not the sliced bread of VW distributors
www.jbbugs.com

wompninja · Posted: Tue Dec 06, 2011 12:09 pm Post subject:

I think you just need more HP!
_________________
Pics of my 1970 Satin Black Type 1 build

Jake Raby · Posted: Tue Dec 06, 2011 12:12 pm Post subject:

Despite gearing you'll need power to overcome the aero wall...
_________________
Jake Raby
Raby Engine Development
www.rabyenginedevelopment.com
"I've never given anyone Hell, I just told them the truth and they thought it was Hell"

jbbugs · Posted: Tue Dec 06, 2011 1:12 pm Post subject:

markhuebbe · Posted: Tue Dec 06, 2011 1:37 pm Post subject:

modok · Posted: Tue Dec 06, 2011 2:01 pm Post subject:

It's not real scientific, but my general belief is it takes at least 120 crank HP to go 120 mph.
The bus forth should work, maybe the 3.44 with a .89?....... any higher and it might be overkill

Is it against the rules for your fenders to "fall off"?
Wink

_________________
Glen Urban

Bill271 · Posted: Tue Dec 06, 2011 7:22 pm Post subject:

Freakin put a bigger arm in it and piss everybody off!

Lo Cash John · Posted: Tue Dec 06, 2011 8:49 pm Post subject:

You need to do less work or make more power or both.

Can you clean up the aerodynamics? Shave the drip rails and door hinges? Flush mount lexan windows? Loose the bumpers if you have any? Maybe a mild chop top if you have time?

If you try and make more power, how would you cool it? Maybe a ram air tube from the front end straight into the fan intake? Water cooled heads? Run it on alky maybe? Costs more, but to exploit that advantage you could just up the compression a lot and not spend another penny on parts. That helps offset the higher fuel cost. Just throwing some dumb ideas at ya'.
_________________
www.LoCashRacing.org
More brains than bucks...Believe it or not!!

My boss told me I need to work on my mutli-tasking. So now when I use the bathroom at work I surf The Samba on my iPhone.

mark tucker · Posted: Tue Dec 06, 2011 10:16 pm Post subject:

I would bump the cr up to atleast 9. with .040" piston to head clearance. I my self would have at least 9.5,I run 10.5 on the street everyday, no problems.how are your heads? is there room for improvement there?what size motor?carbs?exhaust? and higher cr uses less fuel.

jbbugs · Posted: Wed Dec 07, 2011 6:47 am Post subject:

ralf · Samba Member Joined: July 08, 2008 Posts: 792 Location: r4

i think ud gain top end by turning the exhaust down to 37 vs 73mm

hahaha kidding!!!

that track looks like its killer....

wish u guys all the top end luck and hit us back with updates on the game plan and result
_________________
Flow Through a Curved Conduit

Buellistic · Posted: Wed Dec 07, 2011 7:17 am Post subject:

slalombuggy · Posted: Wed Dec 07, 2011 7:33 am Post subject:

I tried a 388/.82 combo in my buggy. The RPM drop from 3 to 4 it STEEP alround 1500 rpm. You'll need more than 110 hp to pull that gear combo. I would look at a 3.44 R/P, I borrowed a tranny with that gear from Team Blackline last year at Bonneville and absolutely loved it. Every gear was noticably longer and with your short tires I think would help a lot. My autocross slicks are 22 inches tall and I'm running a stock box, that combo sucks.

brad
_________________
BB Buggy 121.253mph @ Bonneville 2012
http://www.youtube.com/watch?v=57hMyJmIU10
Raisin cookies that look like chocolate chip cookies are the main reason I have trust issues

>Help >Donate >Buy Shirts >Register >Log in	See all Samba banner ads \| Advertise on TheSamba.com

Serious Top end speed needed!
Goto page 1, 2, 3, 4, 5 Next

Forum Index -> Performance - Engines/Transmissions		Share:
		Print View

	Forum Index -> Performance - Engines/Transmissions	All times are Mountain Standard Time/Pacific Daylight Savings Time Goto page 1, 2, 3, 4, 5 Next
Page 1 of 5