The Cal-look Lounge

This is purely bench racing to make my work day go quicker :)

My ultimate aim is to build a real street car, one that is capable of driving anywhere at anytime at sensible speeds and comfort levels (yes I am approaching 40). The car also needs with a healthy dose of nitrous be able to turn a decent lap at the drag strip (1/4 mile only in this country).

Having had a car that ran 12s without the gas on before that was ok to drive to and from the strip I know the things I didn't like and want to do differently. One of them was having to drive at such slow speeds on fast roads for extended periods of time.

The obvious conclusion would be a 5 speed box, but the expense and potential issues with rebuilds/spares etc turns me off.

So sticking with 4 speed is there a decent compromise to be made with gear ratios that would allow me to use it as a 3 speed at the track leaving the .89 4th and a sensible final drive? What sort of driveability issues would I encounter and more importantly what sort of ET increase?

Hi Ant,

I know what you mean buddy, been putting up with sloooooow cruising for years to and from the track in my 12 second street legal bugs. It isn't much fun with other road users constantly on your tail when your sitting at 45-50 mph in 4th with close gearing and I always end up feeling pretty stressed after a road journey like that. I have always typically run with a 1.21 4th and 4.12 R+P on 205/60's. Now have 205 / 70's and it is a little better in terms of higher cruising speed, now between 50-55 mph.

My buddy Alex runs a 1.04 4th with a 3.88 R+P and loves it on the street and he's even brave enough to hit the motorways / freeways !! His is an all steel and glass full interior late bug with 2109 cc motor and runs low to mid 13's regular on radials. So I think that's pretty stout and a good all rounder.

Cheers

Shane.

Good info thanks. I'm not going to be happy with 13s though :)

Engine is 2443cc, FK89 etc

I run 3.88 r/p    3.75   2.08   1.31   .89                   good for low to mid 12's in third gear  and 80+mph  in the 3200 rpm range on the freeway.

Thank Jason, I looked at those rations on John Maher's gear calc

http://johnmaherracing.com/calculators/gear-ratio-calculator/

Shifting gear at 6800 (took a guess basedon your MPH) that drops you down to 3750rpm on your 2nd gear shift, 4300 on your 3rd gear shift, and if you found a bunch of power (more nitrous) your 4th gear would drop you down to 4600rpm.

I'm not sure where the lowest point I could switch the gas on but I would imagine over 4000, I suspect there is a bit more than 7000rpm available too.

I also run the 1.31/.89 third and fourth with a 3.88 ring and pinion. I don't have a ton of horsepower, so I find third a little tall around town. That in turn leads me to dream about the 1.48/1.04 third and fourth. I'm certain I'd love it for most two-lane roads, but then it might be just over the line for freeways.

The .89 with a 3.88 is really great when you get into 70+ mph territory.

I'd be happy to drive at 70mph on the motorway/interstate. I don't do anymore than this in my daily and used to do it in my stock ratio box with a 1914cc.

3.88 and 1.04 4th is what I used to run,one of the reasons the cab never ran reasonable ET N/A was I had it geared for nitrous, but it does make it more usable on the street, the cruising rpm never bothered me, spinning the fan quicker keeps it cool enough

cheers richie 

My chop cruises nicely at 70mph at about 3200+ rpms.  I have a porsche 912 pulley on the alternator so the 2275 motor likes it at that rpm. Cools well and stays nicely in the power band. I have a 3.88 with the .89 4th in mine. Great for road trips.

Rick M

I recently built a gearbox that has me thinking about building a second one identical to it for my street/strip car.  Around where I live its mostly country roads and driving around with my bug's close ratio box sucks (4.25/2.46/1.70/1.31 w/3.885 R&P).  Its perfect (for me) for the quartermile, but crusing, not so much.

So this new gearbox has a 3.78/2.06/1.31/.93 with a 4.125 R&P.  The spread of gears seem decent, and frankly I was really pleased with the way the early 1.31 3rd works and the .93 4th seems spaced well with that 3rd.  The 1.26 3rd more commonly used just zaps the performance out of an engine designed to run high RPMs.  I haven't raced this box, but "spirited" around town driving and highway crusing are really nice.  The 2332 engine makes quick use of the taller gears.  65-70mph highway speeds are a breeze.

if you want good torque multiplication, sensible rpm drops and reasonable rpm at today's mph, I would use 4.37:1, 0.89 4th and no larger than a 25.5" tire.

4.37:1 R/P  0.93 4th gear 195/65-15 Fun on the street and driveable ;D  with 205/70-15 perfect for fast cruising on the freeway and with 195/50-15 faster on the track....

Greetz: Dirk

Richie, what speed with which RPMs were you running with this set up?

Regards Edgar

If you can do without drag race starts and 60 foot times...
A long first gear and then close ratio 2,3 and a near stock 4th might be fun around town and on the freeway.
Poor mans 5 speed, a 4 speed geared for roll ons from 25 mph to 125 mph.
Long 1st gear is common for road race gearboxes.

Hi Eddie

it would turn about 3700rpm at 70mph,I used a 205/65/15 rear tyre on the road,best mph with that combo with nitrous was around 125mph at the track at about 6700rpm

cheers richie 

Hi Richie,

Drove to SCC this year with 3 days of 600 km highway driving. some 8 hour drives with a few stops.
But I can tell you the high RPM s troubled me sometimes, there is no sound deafening in my car + the box is just a AO box that was laying around, It is terrible wining in 4... I noticed during this trip.
It is on 195/65/15 rear tyres. the front tyres are 165/65/15 so don t know if speed gauge is accurate.
I need a new box so I think I am going for 0.82 4 gear.
So I am reading here what suites best.

(http://www.keversite.nl/fotoalbum/fotos/121625.jpg)
Temp staid all day at around 90 Celsius only type 4 cooler no extra cooler.
so maybe those RPM s are good for cooling.

and at a stop in Sweden near the Norway border  ;D
(http://www.keversite.nl/fotoalbum/fotos/121626.jpg)

Regards Eddie

I'm Considering this exact gearing now, I would love to have a 5 speed and would buy one tomorrow however I just refuse to play the " put your 1000 bollars down and wait for eternity game..... Heck the Bergs current Samba ad says kits will be avalable in August 2011, so what does that tell you LOL.........
Jason how tall is your rear tire?  Cheers.

P.S is anyone has a line on a 5 speed or kit drop me a line.  ;)

Darren

There is one for sale in Norway.. Not mine. Guess the shipping would kill the price tag  ::)

Cant say anything about specific nitrous gearing but here's my story:

After a lot of consideration, calculations and even driving simulations i went for the following setup:

Full weight bug
1776cc typ1 setup to be 'got torque without being a tractor'


3.44 ring and pinion (weddle) 3.78 | 2.06 | 1.44 | 1.04 | rear wheels 215/65/15 or 225/65/15 for finetuning.

this gave me very acceptable 'cruise' rpm at different speedzones, right in the torque curve (and power surplus) so i can stomp it without shifting back.
Or even when i would lug it around its one shift down and there you go  ;)

30 km/h  1st gear  3100 rpm
50 km/h  2nd gear 2900 rpm
80 km/h  3rd gear  3200 rpm
100 km/h 4th gear 2900 rpm
120 km/h 4th gear 3450 rpm


Its all looking in a crystal ball but i hope to integrate first gear into the equation this way and make it a true 4 speed and not 1 + 3 speed.
The closer ratio 2nd to 3rd provides the right rpm drop for a quick blast if i shift at 5500 rpm: 1660 revs down.

I decided to turbo it just recently (GT2560R BB) after the gears were ordered, ran it all through the number crunchers and its 'in the ballbark' boost wise between gears.
Might consider a drop to .93 on fourth if the turbo is too much fun, luckily these gears are common and i would still have the closer ratio 2nd to 3rd.
The big downside of a 3.44 RP is you can't use a LSD as the pinion is quite large compared to a stocker (according to Weddle), don't know about ZF LSD's.

There are great programs out there to calculate with and even an excel sheet is enough to do the math for ya  :D

On Track 215 65 15 M&H DOT's which are 26"      on street 205 65 15 which are 25 1/2"

so you use a slightly lower tyre on the street then?
i tought it was beter to use a higher tyre on the street to win some topspeed.

henk!!!

On my old car I went from 195/60's to 205/70's, a huge 3" difference in height. The rpm's only dropped by 300 at 75mph.

Tire height does not make that big of a difference in gearing.

Hello Zach,

195/60-15 =187cm per turn
205/70-15 =203.1cm per turn

8.6% more. I think it is a big difference!
A example: 3000rpm =92km/h with 195/60-15 means 100km/h with 205/70-15.

If you are runing a 3.875 R/P and a 0.82 4th gear with 205/70-15 maybe the fan will not spend enough air for cooling the engine.....

my 2 cent Dirk

Henk,

True but I'm not concerened with it really I could comfortably cruise between 75 and 85 at any time and I'm sure it would do 130 plus if I braved it which is fast enough on the freeways of so. cal.   Also a 25 1/2" tire is plenty tall.