Head CFM and horsepower

[BobbyB]

I went ahead and ordered the dragy. Got it in on Saturday. Finally had a little time on my lunch to get out on a safe road to do a couple little test pulls on. My launch is terrible. I mean, terrible lol. 60' foot in 2.5-3 seconds. As you can see, some launches were better than others while some 1/4 mile e.t were better. Obviously a driver/shifting issue on my end. Combine the good launch of the second run with the e.t of the third run and I'd get a rough 13.5 e.t. Anything helpful with this info?

First run:
1/4 mile in 14.33s
1/8 mile 9.41s
0-60 mph 6.01s

Second run
1/4 mile 14.50s
1/8 mile 9.23s
0-60 mph 5.71s

Third run
1/4 mile 14.16s
1/8 mile 9.31s
0-60 mph 6.40s

Try measuring the time from say 2000 rpm to 6000 rpm in second or 3rd gear so launch & wheelspin is not a factor. Just program the dragy to record the time from the corresponding vehicle speeds. From there, it’s mostly a matter of improving engine performance or reducing vehicle weight.

You already have enough information to pretty accurately determine your engine power given your 1/8 & 1/4 mile ets ( if you know your vehicle weight).

There is almost no end to the tweaking and testing you can do with what you now have… For example, if you recurve your distributor you can spend many hours finding out how much it improves or hurts your performance. In fact, you can spend most of the rest of your life tweaking & testing with this thing. The general consensus might be that that you need 35 degrees total advance for your set up… but through actual testing you might find 32 degrees total is just as fast or faster.

The downside is… you will probably be spending money to go faster! Enjoy!

[F-BIRD'88]

What was the mph of those tests.. ET does not tell you much... MPH tells you net rwhp.. Power to weight ratio.
You need MPH data. And true truck weight with driver.

[EXCELLENCE AUTO]

As others have mentioned, run that baby across some scales. There used to be a Recycling place down on Howard Ln. just West of I35. You can run across empty and they will tell you your weight. Or a place where you see gravel trucks coming out. Thats where I went when I lived in Marble Falls. Those big scales usually go in 20 pound increments, which is close enough for what you need.
Knock off a few hundred pounds, and move your gas tank and battery towards the back will make a difference too. There is nothing like seeing the front of that truck come up when you hammer down on the loud pedal!

[rfoll]

It's a truck. It likely weighs over 5000 lb. It has the aerodynamics of a slightly rounded brick. I'm sure you have a fun truck to drive and play around with, but it will never be fast without spending a huge amount of money. I see pickups at the track all the time. Very nicely prepared lowered short bed rigs with big blocks in them. Very few have any speed because they weren't made for that purpose. One of the best I've seen was a 71 C20 with a well build 406. On a night with a barometer 30' below sea level and cool dry air, he was ecstatic to crack into the 11s. Truthfully, everyone was happy that night.

[c1500sbc]

What was the mph of those tests.. ET does not tell you much... MPH tells you net rwhp.. Power to weight ratio.
You need MPH data. And true truck weight with driver.

One run was 100.21 mph and another was 97.88...I can't seem to find the third.

How would one go about calculating with the MPH rather than the E.T?

[c1500sbc]

As others have mentioned, run that baby across some scales. There used to be a Recycling place down on Howard Ln. just West of I35. You can run across empty and they will tell you your weight. Or a place where you see gravel trucks coming out. Thats where I went when I lived in Marble Falls. Those big scales usually go in 20 pound increments, which is close enough for what you need.
Knock off a few hundred pounds, and move your gas tank and battery towards the back will make a difference too. There is nothing like seeing the front of that truck come up when you hammer down on the loud pedal!

Hey man! I didnt realize you were on this forum as well! I actually went to that exact one a couple months ago. The one off Howard lane. Truck weighed in right at 4,000lbs with me (165lbs) in it.

[Jeff Lee]

1320 ÷ 100.21 MPH = 13.17 ET. That’s if everything was correct for properly prepared drag vehicle. So basically you have over 1 second hiding there without even opening the hood (much less the engine).

[F-BIRD'88]

Net RWHP = WEIGHT x [ (MPH x .00426)³ ]

Net RWHP = 4100 x. [ (100.21 x .00426)³ ]

Nrwhp = 4100 x .0778

NetRWHP = 318.96

If the weight is more than 4100# power is higher.
If weight is less than 4100# power is lower.
The Power to Weight ratio is .0778

Did you record 1/8th mile MPH from your runs?
The difference between ¼ and ⅛ mi MPH's can show the effect of truck body area wind drag at high speed.

And or show top end power problems (missfire, over rev, excess spark timing excess friction etc ) (strong head wind). ( torque converter problems) ( truck tire friction)

You don't really need to run full ¼ mile tests.

The data from ⅛th mile test runs ET, MPH etc is fine..
You are looking for what tuning changes create better truck performance (increased power to weight ratio).

Ref:. ⅛ mi. MPH. ='s. ¼ mi MPH ÷ 1.23

"Hook Factor". (Car launch & acceleration efficiency)
How good the car is using the engine power to accelerate. is a factor of ET x MPH =

Usually. 1400 ish ± for stock street vehicles.

Good drag cars. 1300-1330 ish. ±

Very good drag cars. 1290 ish ±

A lower Hook Factor is better use of the power.

[rfoll]

As others have mentioned, run that baby across some scales. There used to be a Recycling place down on Howard Ln. just West of I35. You can run across empty and they will tell you your weight. Or a place where you see gravel trucks coming out. Thats where I went when I lived in Marble Falls. Those big scales usually go in 20 pound increments, which is close enough for what you need.
Knock off a few hundred pounds, and move your gas tank and battery towards the back will make a difference too. There is nothing like seeing the front of that truck come up when you hammer down on the loud pedal!

Hey man! I didnt realize you were on this forum as well! I actually went to that exact one a couple months ago. The one off Howard lane. Truck weighed in right at 4,000lbs with me (165lbs) in it.

I'm really surprised the truck is that light. When Gm down sized the large B body cars in 1977, they started out at 4200 and went up from there. A friend had a 77 Monte Carlo that weighed 4600.

[F-BIRD'88]

Does the Dragy software allow yiu to test for acceleration from Speed A to Speed B (time to speed) other than standing start 0 mph to speed?
EG:. time from 25 mph to 80 mph..
Or test for accelleration between Distance A to Distance B (time to distance) other than from 0. standing start.
EG: time or speed from 200 feet to 800 feet.

In this test you still start from a stand still but the test acceleration (time or speed) is from a window of speed A to speed B. or distance A to distance B.
My old Vericom allows these types of windowed tests.
And the handy simple Radar gun verifies Speeds.
The old vericom never errors optimisticly, when it does error.
Thru testing you learn what test conditions tend to create test errors with this unit.

These test parameters avoid the varing effect of initial launch.. ( tire spin etc etc).
No info of any of this on the Dragy site.
Not much support info on the software for this.
But the Dragy device is interesting.
With bluetooth connectivity and separate software on a phone/tablet/laptop app there is not much limitation on analysis and diagnostic software upgrades.
Allows for different 3rd party apps too.
Affordable price. U tube users report good accuracy VS track data.

Question? Is the internal rechargeable battery in the Dragy device removable or hard wired in?

[BobbyB]

Does the Dragy software allow yiu to test for acceleration from Speed A to Speed B (time to speed) other than standing start 0 mph to speed?
EG:. time from 25 mph to 80 mph..
Or test for accelleration between Distance A to Distance B (time to distance) other than from 0. standing start.
EG: time or speed from 200 feet to 800 feet.

In this test you still start from a stand still but the test acceleration (time or speed) is from a window of speed A to speed B. or distance A to distance B.
My old Vericom allows these types of windowed tests.
And the handy simple Radar gun verifies Speeds.
The old vericom never errors optimisticly, when it does error.
Thru testing you learn what test conditions tend to create test errors with this unit.

These test parameters avoid the varing effect of initial launch.. ( tire spin etc etc).
No info of any of this on the Dragy site.
Not much support info on the software for this.
But the Dragy device is interesting.
With bluetooth connectivity and separate software on a phone/tablet/laptop app there is not much limitation on analysis and diagnostic software upgrades.
Allows for different 3rd party apps too.
Affordable price. U tube users report good accuracy VS track data.

Question? Is the internal rechargeable battery in the Dragy device removable or hard wired in?

Yes. Speed a to speed b. Even does 0 to 60 actual time plus 0 to 60 with 1 foot rollout.

The battery is rechargeable with a USB port if I remember correctly…I just leave mine plugged into the cigarette lighter outlet in my hot rod so it is always ready to go.

You can even video in real time with your cell phone & do poor mans data logging. I watched fuel pressure, afr & shift rpm on video and learned a little bit.

The thing is not perfect, but I think it is very much worth the money. The biggest pain is that you can end up with Too Much Data…. For example, if you record 5 to 60 mph. You might test a couple times then go for an hour long joy ride and unintentionally record 5 to 60 mph 20 times that you did not want to record and must delete from your history.

If nothing else, it showed me how untrustworthy my buttdyno is.

[F-BIRD'88]

For any that are interested you can download and use
"REAL CALC" advanced calculator app on your phone to allow you to do the math for power/weight =mph (¼mi).
It does cubic root and X³ functions and ¹/x conviently.

[vortecpro]

A crappy torque converter can eat a lot of hp.. was the converter locked up during the dyno pulls?

This is actually a 5 speed (AR5) manual transmission. To clarify a little further on the dyno pull, it was in 3rd gear (1.49) instead of fourth (1:1) so I know that can affect numbers as well.

Where are you in Tx? Little river for me Friday night with my C-10 no more high altitude for me!

[EXCELLENCE AUTO]

[quote
I'm really surprised the truck is that light. When Gm down sized the large B body cars in 1977, they started out at 4200 and went up from there. A friend had a 77 Monte Carlo that weighed 4600.
[/quote]

Yes, I have trimmed alot of fat so far.
Calvert Leaf Springs saved alot. Extra bumper brackets, spare tire, all are gone.
Front Fender Liners have been replaced with thin plastic from a Ram 1500. I think I started at about 4400. I have a fiberglass front bumper, but it needs alot of work to make it look nice so the heavy steel is still on there. Aluminum heads, and calipers helped quite a bit too... I would love to put a Fiberglass hood on, but I cant find one with the stock appearance...

[EXCELLENCE AUTO]

[/quote]

Where are you in Tx? Little river for me Friday night with my C-10 no more high altitude for me!
[/quote]

I wish I was in Texas still, I would meet you there! My auto mechanics teacher in high school had a Super Gas Pinto and I've been going ever since 1986!!