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Discussion Starter · #1 ·
For those wanting to use their Autotap to get a rough idea of their engine's hp/tq, here's a little Excel spreadsheet I cooked up to do just that. All you have to do is log the MAF (g/s) and RPM to a .csv file then copy/paste that information into the Excel spreadsheet. It takes that data along with present weather conditions and calculates hp/tq, ve, along with a host of other air density related information.

The curves that the software generates I have found to be pretty accurate. The numbers resemble those generated by a Mustang Chassis Dyno, so they will be lower than you expect. Another thing to consider when looking at these numbers is that they are based solely on Air Flow measurements so timing, a/f ratio and other combustion related events will have no affect on these numbers. You can use this tool to show gains with any modification that affects volumetric efficiency, but that's it. \

There really aren't any instructions aside from reading the headings. Items in green are meant to be modified by you. Yellow items are informational and Red items are meant to draw attention for instruction purposes. The teal colored fields represent calculated values used in determining the graphs.

Let me know what you all think...Btw, the sample data provided is data graphed from my 98 Cobra doing a 4th gear pull so-to-speak.

Thanks,
Tony
 

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The Ubiquitous Jimmy V.
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I think that is amazeing..You can use it like a dyno...Show changes..
 

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Discussion Starter · #4 ·
TopRacer said:
I have to say that this is great...

NOW, how do you convert lbs/min into g/s??
The Autotap will log g/s, but if your asking for purely informational purposes then look at the following:

x lbs * 453.59 = x grams (x is the number of)

x minutes * 60 = x seconds (x is the number of)

Therefore, if x = 1 :

1 lbs * 453.59 = 453.59 grams
--------------------------------------
1 min * 60 = 60 seconds

Or:

453.59 / 60 = ~7.56

So:

(lb / min) * 7.56 will give you grams / 1 second

Tony
 

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How did you get so many readings from you AutoTap?

No offence, but is your car slow?

Maybe its my Palm, but i doubt it... i am running a m515...

I did a 2nd and 3rd gear pull...
Total Time: 10.192sec
Start Eng Speed: 1793 in second
End Eng Speed: 6315 in third
Mass Air Flow: 106.47 to 420.7 = 314.23 diff
Speed: 21MPH to 103MPH

I believe that my eng speed and veh speed where higher once complete... I only got 14 readings... on every 0.784sec consistantly...

I also did a 4th gear pull...
Total Time: 15.68 sec
Start Eng Speed: 1698
End Eng Speed: 5610
Mass Air Flow: 89.42 to 369.26 = 279.84 diff
Speed: 35MPH to 118MPH
slowed down due to 50mph speed limit on back road...

I was able to get 21 readings with the 4th gear pull...again all 0.784seconds apart...

It seems that the 2nd&3rd gear pull netted a higher hp and tq than the 4th gear... I actually saw a drop in hp and tq when i shifted...

I do believe that the tq number is a little low and possibly the hp is high... my final peek in the 2nd&3rd gear pull is 405hp and 336tq... only mod is 9" K&N... stock should pull at least 350tq if the hp is that high... dont get me wrong, im not bashing... just letting you know... i love it

Any help on what to do....?? THANKS!!
 

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Discussion Starter · #7 ·
TopRacer said:
How did you get so many readings from you AutoTap?

No offence, but is your car slow?

Maybe its my Palm, but i doubt it... i am running a m515...

Any help on what to do....?? THANKS!!
You need to log only RPM and MAF Flow (g/s). That will increase sampling rate (dont log anything else). A 4th gear run will give the most accurate results (I know, you will have to do like 130mph)

Secondly, if you consider a naturally aspirated 98 cobra that runs almost 109mph in 1/4 slow, I don't know what to tell ya. I guess it's "slow" then... =P

This thing is basing hp/tq numbers off of air flow only. It doesn't account for combustion, spark timing, etc, so the results are not exact, but the curve it produces should be very accurate. It would also serve as a good baseline for air flow changes. If you did anything to increase VE such as a Kenne Belle blower with the same amount of boost as your running with the Eaton, it will show up on the autotap dyno as an increase because the engine will breath better at any given rpm at the same boost level.

Tony
 

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Thanks for the information...

Im sorry... i dont think that your car is slow... i just thought if you are getting so many samples that it took you a while to get up to speed...

NA 12.83 is AWESOME on 280 rwhp...

There are guys with 360rwhp blown not hitting 12.8s...

I dont know what im running cause i have not been able to get to the track and run 1/4... i have hit the 1/8th in 8.49... doesnt seem that bad for stock, but could be better...


Thanks for the time you put into the excel sheet...
 
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