Thread: Finding the TP?

I was reading this writeup (ECU Tuning) trying to soak in some info from it. There is one section in particular that stumped me though. This passage:

"First is the equation for TP: (VQ x K Value / CAS Value) / Number of Cylinders


VQ is the value taken from the VQ Table. CAS is the rpm / 50 x 256.


Here is an example:


On stock injectors at a light throttle and 2500rpms, the MAF is sending back a 2.56v signal (example only). That voltage falls on the 32nd block of the VQ Table. That value is 1B39hex or 6969dec. So our equation will look like this:


[ 6969 x 288 / (2500rpms x 50 / 256) / 6 cylinders = TP ]


So 2007072 / 12800 = 156.8 - and since this is the total amount of fuel needed for the whole engine, we divide it by the number of cylinders (156.8 / 6cyl). That gives us our TP Value of 26dec (or 1Ahex) . How significant is this??? If we know the MAF voltage and the rpm we can calculate the TP and find the exact points being accessed on our Timing and Fuel Maps! So lining up the TP value of 26dec (1Ahex) and the rpm of 2500 we can find the corresponding block (or block of 4 points if it does not fall exactly on 1 point) on the maps under those engine conditions. With a data logger like a Conzult we can quickly find and adjust or fix points on the maps. Even without data logging we can still find points using a good voltage tester and remembering rpms."

I kept trying this equation to suit my B13 ECU, but I kept getting astronomical figures due to the B13 K value (31,xxx). Here's one example I tried, following the above formula:

Using an E60 MAF, at a reading of 2.24 Volts, the MAF value is: 5426

The K value is: 36000

(The first formula given for finding CAS is correct (CAS is the rpm / 50 x 256), the second time it is shown wrong (2500rpms x 50 / 256)
My CAS is: 3,200 rpm / 50 x 256 = 16384

So, that gives me:

(5426 x 36000) / (3200 / 50 x 256) / 4

-or-

195336000 / 16384 / 4 = 2981 (rounded)

A TP of 2981??? Is there something more to this, or is this equation wrong? I have a feeling maybe the CAS may not quite apply to a B13?

Any reason for manually calculating TP?

This guide should help .

I think the "dec" might stand for something. You are probably doing the conversion incorrectly because of that.

Sent from my VM670 using Tapatalk

It stands for decimal, as apposed to hexadecimal. I don't think that's the problem.
You K value seems really high. Is that right?
Also, I think the Z cars were using a different formula for TP than the newer SR20 cars in the ECU.

K value for B13's is 5 digits, while K value for B14's is 3 digits.

Not really, but just something interesting to know. I don't have RT, so I thought it might be of some use to help find spots that need adjustment.




The DEC values are just what the HEX values translate to. If I remember right, DEC is short for DECimal values, wich is based on values of a set of 10. The system we normally use. HEX is based on sets of 16.



I thought that too, as far as different calculations for the different ecu. Just figured it would be something useful to know.



Right. The equation works for the smaller K values, like the B14. But the high K value of the B13 throws it off. I was just trying to figure out what was needed to make it work for a B13. I even tried moving the decimal, like making the K value 3600, or 360, as opposed to 36000.

I understand. But how are you getting that data? Consult? It's possible to get your chip reburned with TP loging enabled. It just saves a huge headache of conversions .

As for K value, I was under the impression that K value stays similar on all OBD1 cars. Now it gets bigger/smaller depending on MAF, injectors, etc.

Great, thanks, now I'm going to start having TP nightmares every night again....

Last time I was testing tunes, I was watching the MAF voltage on my SAFC2, and checked the rpm's. Rpm's were about 3,200. This was just one instance I remember. I just use the SAFC2 for monitoring. I should have paid the extra $$ and bought the consult cable, it would have saved me a lot of time, and I'm sure is a lot more helpful.

Consult cable is much cheaper then a SAFC 2