With the p300, the factory diff ratios are 4.10. we offer 4.44 differentials that offset the change from 32 to 35 inch tires. Basically makes it feel as stock again. For the p400, the stock ratio is 3.54. we offer 3.73 when going to 35s. The tuning is required for the transmission ECU to be happy with the ratio change, but also we make adjustments to the 8hp to provide better performance. A very direct seat of the pants performance feel. Better shifting. Hds gears longer. Rev match on decel. We can also do the tuning for stock ratio.

 

I may need a better real-world scenario/proof. In a worse case scenario where I had a catastrophic engine failure while under warranty, wouldn't the dealership cross check to confirm the vehicle was sold as a P300 or P400 spec, whether changes are detectable as the ECU level or not?

 

You can just remove the piggyback before taking it in. It's like using an aftermarket charger with your iPhone that causes an issue and then taking the phone to the apple store WITHOUT the charger. They won't be able to tell it was due to the aftermarket charger.

 

Like I said, it is a factory tune, so it wouldn't affect the warranty since it is running on factory specs. the chances of having a catastrophic issue related to running the P400 map is damn near impossible. The dealer wouldn't know that your car is running the P400 map unless they go dig into the CCF files, which is highly unlikely. If you had an engine failure, they would find out what the problem is and replace the faulty part and/or the entire engine or the Powertrain Control Module. If the PCM was replaced, it would be coded to your VIN, so it would run the P300 map by default unless you go back to change the CCF files.

@sarek, @GarrettSD and @markjlr would be the ones to talk to for an expert opinion on this subject. I'm pretty confident that all three of them would have a similar opinion on this.

 

Thanks for the detailed response. I do understand how unlikely it would be that a dealer detected the map change and then as well could pinpoint that as the failure point. Essentially it would be as if they declined to warranty a similar failure on a P400 spec which wouldn’t make much sense legally. Given the relatively nominal cost to make this change with someone reputable like you mentioned above, I’m trying poke holes before getting further committed 😎

 

I recently spoke with a guy in my local LR owner's club who put the Burger tune on his P300 110.

He said that you really notice the extra power in the midrange, but other than that it he said it isn't a huge difference compared to stock.