Consistency day to day

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bleedcummins

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Dec 29, 2009
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Are you guys running pretty consistent day to day?
Within a given day I'm usually with in .07 seconds from my fastest to my slowest, but from day to day, same setup, I have been varying by as much as .3 seconds.

Today I was running 12.91-12.98, but last saturday I as running 12.60-12.66.
A few weeks ago, before lockup switch, I ran a 12.91-12.98 and following week ran 13.21-13.24. :bang
Help please!
 
Yeah, weather can matter a lot. I dyno'd 540 in the heat of the day, following morning, no other changes, 564.
 
The 12.9 to 12.6 days were pretty close weather as far as sunny and hot, about lower 80's when ran 12.6 and today was mid 90's running 12.9's. These days same setup

The original 12.9 day was cool cloud covered day. Jacket weather. Then 6 days later it was hot, probably 80's, t shirt weather, ran 13.2. These days same setup
 
I tired one night to run as consistent as possible. Never done it since always tweaking stuff! This was fuel only with original turbos and pump.

DSC01200.jpg
 
I have a truck I am working on and can get 13.65-13.66 ever single pass. 20 passes later still the same
 
bleedcummins said:
The 12.9 to 12.6 days were pretty close weather as far as sunny and hot, about lower 80's when ran 12.6 and today was mid 90's running 12.9's. These days same setup

The original 12.9 day was cool cloud covered day. Jacket weather. Then 6 days later it was hot, probably 80's, t shirt weather, ran 13.2. These days same setup
Click to expand...

Your problem is quite common with VP44 powered trucks, they vary tremendously depending on intake air temp, fuel temp, etc. This is one of the reasons I hated my old 99' 5 speed. It had enough power with 499 to the rear tire to roll-on spin the tires in 3rd gear, any street. When it would get a little warm out in Vegas 100+ degrees, it would never have enough power to do the same thing. I finally setup a small course to time my acceleration over distance and found that it was way down on power, like over 50 HP when intake air temp hit a certain threshold.

In speaking with Quadzilla back in the day, we came to the conclusion that the factory tuning pulls back both fuel and timing in hot ambient air temp conditions and it's not a linear incremental thing, it's a major tuning change that results in 50 or more HP difference on a hotrod truck.

Now that I own a 12valve, with identical fueling and timing regardless of outdoor air temp, my trucks are much much more consistent. Does my truck smoke a little more and make a little less power when it's 100F instead of 70F, sure, but it's nothing like the massive power swings (due to tuning) that I used to experience with a vp44 truck.
 
Wow that must be exactly what I'm experiencing. Hot day and under hood probably much hotter. Never knew that about a vp. Thanks for the help big blue.
 
Yep, even with a redline box, my VP truck changes 1-2 1/10ths with weather.


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Big Blue24 said:
Your problem is quite common with VP44 powered trucks, they vary tremendously depending on intake air temp, fuel temp, etc. This is one of the reasons I hated my old 99' 5 speed. It had enough power with 499 to the rear tire to roll-on spin the tires in 3rd gear, any street. When it would get a little warm out in Vegas 100+ degrees, it would never have enough power to do the same thing. I finally setup a small course to time my acceleration over distance and found that it was way down on power, like over 50 HP when intake air temp hit a certain threshold.

In speaking with Quadzilla back in the day, we came to the conclusion that the factory tuning pulls back both fuel and timing in hot ambient air temp conditions and it's not a linear incremental thing, it's a major tuning change that results in 50 or more HP difference on a hotrod truck.

Now that I own a 12valve, with identical fueling and timing regardless of outdoor air temp, my trucks are much much more consistent. Does my truck smoke a little more and make a little less power when it's 100F instead of 70F, sure, but it's nothing like the massive power swings (due to tuning) that I used to experience with a vp44 truck.
Click to expand...

Could you just run a fooler on the iat?

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Yeah, just need to know the resistance for 40° or so air temp and build a wire with a resistor to get the spec.

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Is 40* to cold to where it acts like winter time fueling? Should we shoot for 70-80*? Mopar man has a chart on his website of what different resistors read in his iat. Says a 39k ohm resistor measured 26* and a 7.4k ohm resistor measures 87*

I feel I'm gonna have many more hot track days and I'm just wanting to get my times back to 12.6 and start working on dropping them from there, rather than going backwards like yesterday
 
If next time I go out to a t/t night if it's gonna be 100ish again i may go to the store and buy different resistors and try them out. Maybe it helps, maybe it don't
 
He's just using it to trip the high idle isn't he?

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And to fool computer to thinking its 143* so it fuels and adjusts timing like summer weather for better mileage in winter. He's using a 2.2k resistor
 
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