I'm trying to pin down why my 1/4 mile times have been so inconsistent, so I got an OT-2 OBD-II datalogger from Innovate. It took me 2 whole minutes to get it up and running last night!

I'm going to the track tomorrow and I'm trying to decide which channels to log since every time you add a channel it decreases the resolution of each channel. Since I've never done this before, I don't know how many channels I can log and still get meaningful data over the course of a 12-sec 1/4mile run.

I'm thinking of starting with IAT, Spark Advance, RPM and AFR. What do y'all think?

The car is stock with the exception of a BWK and a set of drag radials.

 

Do iat and timing from obd if you must choose 2, don't do more than 2 because it will refresh slower with more

 

I don't think you'll get meaningful AFR readings from the stock sensors.

 

Wait, if this is only obd, don't go by an afr reading off an obd.
Just log iat and timing and see if iat getting too high is retarding timing

 

Add Innovate's LM-2 wideband. It can be setup to replace the existing O2 sensors so it provides wideband logging, and a narrow band signal for the factory ECU. No welding or anything else is needed.

I'm currently researching doing this, and I likely will add Innovate's ODB wifi module like you have. Then you can log everything including AFR.

 

I managed to get logging for three runs today.


First run
This run was a 12.03 when the DA was -121ft and the ambient temp was 54 deg.


Second run
This run was a 12.09 when the DA was 170ft and the ambient temp was 58 deg.


Third run
This run was a 12.16 when the DA was 454ft and the ambient temp was 62 deg.


Any thoughts on these graphs? The car was actually quite predictable today. It was fast in the morning, and slower but consistent when the weather warmed up.

 

Your car is pulling major timing since your iats are over 120*

 

Is 120-deg a magic number for the stock tune to pull timing? My IATs were 120-122 before the runs, and would rise almost exactly 40-deg after each run.

Since the car is within spitting distance of running 12.00s when it's cold (in the morning), I need to figure out how to add consistency without adding (much) power. What type of IAT drop would I see by adding an underhood tank and splitting the cooling system?

 

If you start your run already at 120* forget it, Your running and beating on the car for nothing.
Cool the car down before you run, do you have a good pump and heat xchanger?
Stock tune it pulls timing in 3 stages but starting at 120* it's already not good.

Splitting the system and adding a tank will help a lot

 

I have the Bosch -10 pump and a belt wrap kit. Everything else is factory stock. Since I'm already on the verge of breaking into the 11's, but I run in the Sportsman class and can't go faster than 12.00, it sounds like a tank is the best first step. Maybe that will let me run the same times in the afternoon that I currently run in the mornings (12.007, 12.030) and make them more predictable, without going too fast in the cooler weather.

 

You need a heat exchanger before the tank sir

 

this is with circulating ice for about 10 mins to cool then jamming ice in before the run in my 03 cobra resivoir. stock pulley

 

These cars start pulling timing early = 95* IATs. Which is basically as soon as I start the car in Florida.

Here are the numbers I grabbed from a chart posted here some time ago:

IAT/Timing pulled
95*/3.5*
113*/6.3*
149*/9.5*

 

That is usually stock tune, when you get tuned tuners play with that alittle