How to make the CX7 quicker off the line.

[Sassimac]

Hello All...

Considering the CX7 is a heavy car, and in my case an auto AWD, a 0-100kmh time of 7.12 seconds is pretty good. The one aspect I would like to fix up, is the traditional pause off the line. Leaving the car in "Drive" and slamming the foot to the floor results in a pause before the car pulls away. If this pause is minimised, the car will easily be a 6 second sleeper!

Is there anything I can tune in, that will help? Remember, I have no clutch..!!!

Thanks..!!!

[Steve @ VersaTune]

A small brake torque to spool the turbo will make a big difference.

[Sassimac]

A small brake torque to spool the turbo will make a big difference.

Sorry,, I don't understand what you mean. Do you mean loading the torque converter by raising rpm with the foot on the brake?

Is there any area in the tune I can alter to help off the line performance?

Thanks..!!!

[skiptownmcat]

Raise the loads at 2250-3500, eat salads!!

[Steve @ VersaTune]

Timing is usually heavily retarded at high load below 3000. You can bump up the timing to wake it up, but "caveat emptor". Your rods may not love you for it.

Loading it up against the converter to spool the turbo w/ an auto is the same as revving and feathering the clutch in a manual.

[mituc]

I'd say to focus on making your car quicker on the road, not on the drag strip. There are a few reasons why people are throwing rods:
- raising the load too much below 3000 (in the 2200-2800 area where the turbo is spooling up and can make full boost);
- throwing too much timing and detonating at WOT;
- leaning the mixture too much (WOT AFR's of 11.5-11.8 or higher above 4k rpm is bad in these engines, shit is cooking up and eventually cracking and flying to the skies through your hood later at low RPM's/PT/mid or high load);
- a combination of two or more of the above, or hardware mods that can lead to that (incorrectly tuned WG tables for DP/TMIC, demanding too much fuel from a stock fuel pump, and so on).

You have a great tune so far, tuned for fuel economy and also for better acceleration, I think past this point you will have to split the fuel economy and the performance because you can't really combine the high timing and lean mixture that give you this awesome mileage with high load targets which actually need the opposite of the settings you have for fuel economy.

[Sassimac]

Thanks for the replies everyone.

I read with interest your thoughts Mituc on targets for load and fueling. The increases I have been working with are:
- Approximately 10% increase in load targets up to a maximimum of 1.8. This keeps boost in the 16-17PSI max range.
- WOT fueling is 11:1 or 0.748 Lambda.
- Last night I did a run, and only logged a couple of 0.7 and 1.4 knocks only at WOT. Mind you it was 32C outside..!!

In the end, I honestly figure that trying to make the car quicker than 7 seconds is starting to stretch the friendship. Afterall, it is a daily driver..!!!

[mituc]

In this case you can try enriching the mixture a bit in the areas where you've seen WOT kr (and above) and see what happens. If it doesn't work revert to the previous lambda values but pull 1 degree of timing. WOT KR should not exist, it's bad for the car and it's bad for performance. Why have 1.4 degrees of timing retard when you can pull half a degree or a full degree of timing and still run 0.5-1 degrees more advanced timing? Or even the same timing if enriching the mixture a bit will help?!

My car is pretty different than yours but I've learned a lot from you and I thank you for that. My aim is to have an as economical (and safe/ >0.75deg KR free) as possible tune below 3000-3100rpm, and past 3200rpm after my big turbo will be able to fully spool I'm going to create a big mess in all the tarmac layers.

[Sassimac]

Mituc...

Thanks for the reply, you have given me an idea I must admit I did not think of..!!! I'll add a little fuel at WOT, and see how that affects the advance. How much extra fuel would you add..?? Currently I target 11:1 at WOT.

Regarding low load/RPM advance.....
I have actually left most of the CL normal table stock, only adding a little advance in the mid rpm range to perk it up. What I did do was add a stack of advance (5 degrees) to the CL Max table instead. As I understand it, the ECU starts at the normal table and works its way towards the max table value. The idea I am working with, is to allow the ECU to pick as much timing as it can and retard if it hits knock. This has certainly helped me get much higher fuel economy figures than I have ever seen.

[skiptownmcat]

Interesting method, seems logical. Maybe the oracle will give us his thoughts.