ET predictor programs for da 'puter.....

tomslik · November 03, 2007, 12:13:15 PM

anybody got one?
could i run some numbers by ya and see what it's supposed to be capable of?

kb426 · November 03, 2007, 08:20:02 PM

I may have a version of quarter jr. but I don't remember where it is. If I find it I'll let you know.

C9 · November 05, 2007, 09:05:09 AM

I have a old Moroso drag racing slide rule that's pretty accurate.

Needs:
Car weight.
Horsepower.

or -

MPH or ET from a time slip.

Diff ratio and/or tire diameter wouldn't hurt.

tomslik · November 05, 2007, 10:10:33 AM

Quote from: "C9"I have a old Moroso drag racing slide rule that's pretty accurate.

Needs:
Car weight. rough guess, 3000
Horsepower. at the rear or engine?or - prolly 350 at the crank...MPH or ET from a time slip.

maybe next year...

Diff ratio and/or tire diameter wouldn't hurt.

4.10's in a 9", prolly a 28" tall 9" wide slick with a 3.44 1st gear t-10

chimp koose · November 05, 2007, 11:35:39 AM

Hot rod magazine had an article in the mid 80's called "geared for go " which was well researched and written. you might be able to find it on the net. basically you need to know your horsepower and vehicle weight with driver. I found a car at the strip with roughly the same mods as my engine and about the same weight and used his mph to figure a horsepower number. nowadays you can use desktop dyno or any other program to calculate horsepower.From horsepower and weight you can determine 1/4 mile optimum MPH .(chrysler engineers figured out these formulas in the early 60's and they are what is used in the moroso et calculator slide rule).When you know your probable trap speed ,you can calc. gear and tire size.you are trying to gear the car for an rpm of 108% of the max HP rpm! (yes max hp rpm x 1.08) The article also had a chart that showed low gear vs.rear gear vs tire width needed to obtain required traction (most people a run wider tire than needed).If you play around with the numbers you will be amazed at how small a tire you can hook up with.If you find the narrowest shortest tire that will fit the formulas you are doing good. I ran 12's on a6.9" wide 23" diameter slick (M/T et drag 7x24x13) with 3.70 gears in a 2800 lb car with slapper bars.The smaller the tire the less rotating mass (1lb less rotating mass is equal performance gain to roughly 10 lbs of non rotating mass). the shorter the tire the less gear ratio you need to run .you can probably optimize overall drag performance by picking a tire diameter to suit the gears you run on the street.I will try to find the article,it is well worth the read.

tomslik · November 05, 2007, 11:55:27 AM

chimp, i'm just looking for a ET ballpark guess right now so don't waste a bunch of time looking...

kb426 · November 05, 2007, 01:19:17 PM

Moroso slide rule says 11.42 @114.9 mph. 5650 rpm in the lights.

tomslik · November 05, 2007, 02:46:18 PM

hmmm, mid 12's at this alt.....
not bad for starters..
plan is for a 377 a bit later....

chimp koose · November 08, 2007, 10:59:07 PM

tomslik,try this site.http://wallaceracing.com/Calculators.htm punch in your numbers and let it crunch em for ya! have fun!

C9 · November 10, 2007, 07:46:42 AM

I came up with 11.5 and 115 mph.

About the same as KB426, but he can probably see better than I can.

This takes into account a fairly optimized chassis and gearing etc. suited for drag racing.
In other words, about the best you can do with your combo.

Personal experience shows you'll probably run low 13's and 107 - 110 mph
first times out.
After some dinking around - called tuning by those who know what they're doing - You should dip into the low 12's.

Part of it is learning to drive the car.

Considering the low 3.44 1st gear, 4.10 diff and 28" tall tire you're fairly close to the optimum recommended overall ratio in 1st.

If you have access to a pair of 26" tall slicks it may be worth giving them a try.

How wide is the wheel the slick is on?
That can make a difference.

I just bought a pair of nice Centerline 10" wheel's with 12" slicks and the wheel's are a bit narrow for the tires.
10" slicks at the right height would be better and is the way I'll eventually go.

One of the local drag racers - a retired Ford engineer - runs a Fairlane that cranks off low 11's.
The engine is a built FE of unkown size, but I'll bet it falls into the 427" - 428" category.
I didn't ask and he didn't offer.

Anyhoo, he likes to run a 9" wide slick on 10" wheels.
His theory is you can run a little more air pressure and square up the tread pretty good.
Seems like a viable theory, especially since the car runs pretty good considering the weight.

I do understand you may be giving up a little contact patch since the wrinkle wall slick at a higher pressure would be shorter longitudinally speaking.
Then again, if the outer edges are carrying some weight with the narrower tire that may be a moot point.

BFG with their radial street slick found that some guys were running too low of a pressure and defeating the purpose of the radial slick in that they tended to 'cup' and the middle of the tire wasn't biting all that well.

Regardless of slick style, I'd do some short parking lot burnouts - if you have a place - and read the pattern on the asphalt with differing air pressures.
Black all the way across be good....

tomslik · November 10, 2007, 08:29:25 AM

Quote from: "C9"I came up with 11.5 and 115 mph.

About the same as KB426, but he can probably see better than I can.

This takes into account a fairly optimized chassis and gearing etc. suited for drag racing.
In other words, about the best you can do with your combo.

plan is to run a set of caltracs, but if i end up mini-tubbing...

Personal experience shows you'll probably run low 13's and 107 - 110 mph
first times out.
After some dinking around - called tuning by those who know what they're doing - You should dip into the low 12's.

probably more realistic as the tracks' at 5800 ft

Part of it is learning to drive the car.

yep, there'll be a lot of fine tuning the driver.
it's been a while...

Considering the low 3.44 1st gear, 4.10 diff and 28" tall tire you're fairly close to the optimum recommended overall ratio in 1st.

If you have access to a pair of 26" tall slicks it may be worth giving them a try.

actually, i'll be "optimistic" if a 28" tire will fit. width will be an issue too

How wide is the wheel the slick is on?
That can make a difference.

I just bought a pair of nice Centerline 10" wheel's with 12" slicks and the wheel's are a bit narrow for the tires.
10" slicks at the right height would be better and is the way I'll eventually go.

One of the local drag racers - a retired Ford engineer - runs a Fairlane that cranks off low 11's.
The engine is a built FE of unkown size, but I'll bet it falls into the 427" - 428" category.
I didn't ask and he didn't offer.

Anyhoo, he likes to run a 9" wide slick on 10" wheels.

[i]yeah, that's an old stock class trick, get's you a little more patch and still be legal[/i]
His theory is you can run a little more air pressure and square up the tread pretty good.
Seems like a viable theory, especially since the car runs pretty good considering the weight.

I do understand you may be giving up a little contact patch since the wrinkle wall slick at a higher pressure would be shorter longitudinally speaking.
Then again, if the outer edges are carrying some weight with the narrower tire that may be a moot point.

BFG with their radial street slick found that some guys were running too low of a pressure and defeating the purpose of the radial slick in that they tended to 'cup' and the middle of the tire wasn't biting all that well.

Regardless of slick style, I'd do some short parking lot burnouts - if you have a place - and read the pattern on the asphalt with differing air pressures.

right out in front of my house semms to work well for everybody else so.... Black all the way across be good....

tomslik · November 10, 2007, 08:50:52 AM

http://www.bandimere.com/events/displayevent_detail.php?eventID=256

Crosley.In.AZ · November 10, 2007, 11:58:11 AM

computer numbers are OK.... it will be fun to see what the Rumbler will do on the track... I am watching. LOL

Sometimes a car will fool you on a first hard pass... many of my friends were telling me my 69 Camaro would not break into the 10's with stock front OE suspension.... yada yada.

First full pass I lifted about 3/4 track since I had forgotten to turn on the back-up electric fuel pump. The fuel pressure dropped fast , so I lifted....it ran an 11.0 , some where around 110 mph. The car did run mid 10's that eve... 135 mph. It did not 60 foot too well. Wounded the crank shaft when the dizzy moved.

Do NOT use a cheap dizzy hold down .

chimp koose · November 10, 2007, 10:45:59 PM

the deal with a wider rim than contact patch is also to limit tire growth at top end.a narrower rim will allow more sidewall growth ,a wider rim will actually get you a bit more rpm at top end.I totally agree with the rest of you, get some seat time in the car . If you are bracket racing ,a consistent et with a decent light will usually go more rounds than the odd killer light with an inconsistent car.I have heard great reviews about the cal trac bars ,they seem to work best with a monoleaf setup.