Gaining More power from a reflash tuning

Hi Mates,

I have 2 questions

1- So Im curious to know without any mechanical modifications to the car ( inlcuding exhaust and intake ), How does a reflash tuning add more power to the car, taking into consideration that the timing by the manufacturer is already optimal for every car, and that AFR would affect the power of the vehicle over a wide range.

2- How does an intake or exhaust system add more power to the engine ? the VE of the engine will increase ? and even if, wouldnt the short and long fuel trims take care of that withou a tune?

Thanks all in advance

What vehicle, engine, and modifications?

The short answer is, if it's a non turbo small displacement engine you may not have a lot of power or torque to gain. Turbo cars typically can pick up the most with a reflash, because you are using some of the safety margin in the tune to push the turbo harder.

The intake system reduces the pressure drop across the throttle valve (n/a engines) or across the turbo inlet, making the engine and/or turbo work less hard. On the exhaust side changing the system can reduce the backpressure so the engine isn't working so hard, or allow a special pulse tuning by changing runner length.

The short and long term trims can take care of small changes, such as a slight change in the muffler or maybe a change in air filter. Big changes increase the risk of the ECU not being able to measure/calculate the air in the engine correctly which can result in damage.

Hi @Arghx7 and thank you for your input.

My question was any NA engine without any modification nor intake nor any exhaust. How does a reflash tune give more power ? are we playing with the AFR or timing or MAF scaling ? the engine is fully bone stock where can we get the small extra power from?

There is number of horsepower still at table you can extract them by adding spark and adjusting fuel .

This dyno graph for a stock tundra 2007

There is number of horsepower still at table you can extract them by adding spark and adjusting fuel .

This dyno graph for a stock tundra 2007

@chevy1j yes i do understand, but one thing is: isn't the factory ignition timing optimal already for safety and performance?

and regarding the fuel adjustment, we do agree that the performance wouldn't change at all by going from lambda 1 to lambda 0.85 right ?

I'll give you an example of where you can pick up power. If the factory timing maps are set for regular fuel (92 RON/ 87 AKI in the USA), they may be especially conservative. The knock system may also not be very aggressive, so it's not automatically running the engine at the knock limit. In that case you can pick up power and torque by advancing spark.

You can also lean out the AFR. This will heat up the catalyst, but the real world impact is minimal as long as you don't overdo it. That mostly degrades emission performance in lab tests. Another example is variable valve timing. Sometimes there are limits on how much cam phasing is in the stock tune, or some limitation on the operating area of a variable intake system or 2 step lift system. Those limits were put in there to meet emission limits in laboratory tests.

Hi @Argh7 and thanks for your input! Seems fair for the timing and VVT. But how leaning the AFR would give more power? I thought factory ECUs never run crazy lambdas below 0.8 that would affect power!

Factory AFR's under heavy acceleration (WOT) are rich for 3 basic reasons (simplifying here):

1) Intentionally richened up compared to Lambda 1.0 to improve engine output - called power enrichment

2) Intentionally richened up to reduce engine, catalyst, or temperatures - called exhaust temp or hardware protection enrichment

3) Unintentional enrichment due to part variations or some inaccuracies in say a stock VE table or stock MAF curve or some other table in there. I don't want to say it's common or uncommon, but it does happen. Maybe there is a change in the production of the MAF sensor and suddenly the scaling in the ECU isn't so accurate.

It's a case by case basis whether leaning out makes more power. It depends how rich you started. A lot of times a reflash will turn off exhaust temperature protection model for example. That will get more consistent AFR and power but cause degradation of the catalyst over time.