OTS vs. custom tune

[unsurety]

Everybody's car is different. With just bolt-ons (N/A) it shouldn't matter much though, right?

After discussing it with a friend, I found that he ran a Cobb AP with an OTS tune on his 04 STi. But when he get it custom tuned at GST, the car pulled even harder, and all the way to redline where it felt like it ran out of steam up top on the OTS.

We're probably talking only about a few whp difference on our cars, if anything. Has anyone gotten an off-the-shelf tune, then later got it dyno tuned and noticed a big difference?

[Shiv@Openflash]

Originally Posted by unsurety

Everybody's car is different. With just bolt-ons (N/A) it shouldn't matter much though, right?

After discussing it with a friend, I found that he ran a Cobb AP with an OTS tune on his 04 STi. But when he get it custom tuned at GST, the car pulled even harder, and all the way to redline where it felt like it ran out of steam up top on the OTS.

We're probably talking only about a few whp difference on our cars, if anything. Has anyone gotten an off-the-shelf tune, then later got it dyno tuned and noticed a big difference?

With a turbo car, the difference between an OTS tune and a custom tune is often very significant since OTS maps, by nature, have to err on the side of conservatism. On a turbo engine, being conservative can reduce power by 5-10%. On an NA car, were the effects of less timing and lower AFR target are far less significant, you may only compromise power to the tune of 2-5%. And 2-5% on a 200whp FA20 (as opposed to 5-10% a 350whp STI) is pretty small. But there is no doubt that custom tuning does help. But it's important to be realistic about the additional gains just so one isn't disappointed

Cheers,
Shiv

[unsurety]

Perfect, Shiv!

I'd rather err on the side of caution anyway. I also like the idea that an OTS map will be proven to work with many, many cars. I didn't want to name drop, but hint-hint, nudge-nudge, I like the idea of being able to just reflash for free, essentially, if I add something later.

[Xero-Limit]

We see all kinds of MAF scaling corrections needed with intakes/filters, VE changes that need tweaking from different header types, and tons of other things that end up needing unique maps for each customer. For that reason we don't offer OTS maps, and every tune is a custom tune. It does take a bit more effort and costs a bit more, but when something works 75% of the time, it really stinks to be the 25% for whom that doesn't. I can't see the sense in spending thousands on mods to then short change the one part that probably has the biggest impact on reliability and performance.

[Circuit Motorsports]

I think an important point of focus here is not necessarily the power output difference of an OTS tune vs. a Custom tune on an FA20 N/A application, but to focus on the issues of where the OTS tune misses the mark due to differences from one car to the next.

Intake tract differences need to be tuned for, even a drop-in filter changes things and can cause incorrect AFRs and/or high fuel trims. Different header configurations change engine VE and necessitates tune changes to maximize your modifications. These items can lead to knock and/or reduced output if not tuned for.

Your local fuel quality and octane affect what ignition advance you can run without knock. Yes, the ECU can adjust within a certain range, but your motor would have to experience knock in order to make adjustments, such as lowering of the Advance Multiplier, or Knock Corrections being applied.

It can get really complicated when you look at all of the possible combinations of modifications such as adding the Crawford power blocks (CPBs) and say an EL header. Major changes to engine VE that require a different tune. Now, that tune would be different for the CPBs and an UEL header. Different again for the CPBs with a stock header. You get the idea.

Relying on ECU trims and adjustments to correct issues caused by these differences is just not a good idea, especially when trying to increase the engine output over stock form.

There are compromises made in an OTS tune. A custom tune will always outperform an OTS tune, in more ways than just peak HP and TQ.

Having said that, I think there is a place for OTS tunes, and a conservative OTS tune can be close to an ideal calibration, but be aware that you are leaving some power on the table, and it is likely that your OTS tune needs some adjustments for your specific car and its modifications. That applies even if your car is stock. You should data log to determine what adjustments are needed, and then either make those adjustments yourself or find a tuner to do so.

- Bob

[Turdinator]

@moto-mike @Circuit Motorsports can you optimise a tune for a set of headers via e-tune? I was under the impression that it was difficult to get the optimal cam timing when not on a dyno?

[steve99]

Originally Posted by Circuit Motorsports

I think an important point of focus here is not necessarily the power output difference of an OTS tune vs. a Custom tune on an FA20 N/A application, but to focus on the issues of where the OTS tune misses the mark due to differences from one car to the next.

Intake tract differences need to be tuned for, even a drop-in filter changes things and can cause incorrect AFRs and/or high fuel trims. Different header configurations change engine VE and necessitates tune changes to maximize your modifications. These items can lead to knock and/or reduced output if not tuned for.

Your local fuel quality and octane affect what ignition advance you can run without knock. Yes, the ECU can adjust within a certain range, but your motor would have to experience knock in order to make adjustments, such as lowering of the Advance Multiplier, or Knock Corrections being applied.

It can get really complicated when you look at all of the possible combinations of modifications such as adding the Crawford power blocks (CPBs) and say an EL header. Major changes to engine VE that require a different tune. Now, that tune would be different for the CPBs and an UEL header. Different again for the CPBs with a stock header. You get the idea.

Relying on ECU trims and adjustments to correct issues caused by these differences is just not a good idea, especially when trying to increase the engine output over stock form.

There are compromises made in an OTS tune. A custom tune will always outperform an OTS tune, in more ways than just peak HP and TQ.

Having said that, I think there is a place for OTS tunes, and a conservative OTS tune can be close to an ideal calibration, but be aware that you are leaving some power on the table, and it is likely that your OTS tune needs some adjustments for your specific car and its modifications. That applies even if your car is stock. You should data log to determine what adjustments are needed, and then either make those adjustments yourself or find a tuner to do so.

- Bob

Well said Bob,

Having the OTS OFT tune and a device to flash modifications myself has enabled me to learn the basics and make some minor adjustments to these tunes to better suit the fuel in my country as well as MAF adjustments.

I'm certainly no tuner, but its been an enjoyable experience learning and making minor adjustments which has enabled the correction of knock and MAF scaling and minor fueling adjustment needed for different fuels and minor intake mods.

I agree that the custom tunes done on a dyno by an experienced tuner are better, but for NA guys wanting to learn the basics and make a few tweaks I am very happy with my choice.

I like that their are no locks on the tunes and I can see what the tuner has changed compared to stock, and you can see the changes made for the different mods by comparing the tunes.

Its another option that was not their previously.

It not for everyone but I think many are glad it exists.

Its good to see you have an open minded sensible viewpoint, their will always be a place for custom tunes and tuners.

I'm sure you guys will pick up some work from some OFT OTS guys wanting to maximize power and clean up and minor issues or wanting to run mods not catered for by the OTS tunes.

[Wepeel]

I do wonder about the robustness of custom tunes. The custom tune is done on a dyno in a few hours, under certain environmental conditions, with a certain quality of fuel, with a certain state of health of the engine/sensors. I know the ECU compensates for weather/temps etc, but those compensations are set to be compatible with the stock tune.

Fuel quality varies from station to station, probably even week to week at any given station. Ethanol content, fuel blends/quality, not to mention summer/winter blends. Sensor accuracy drifts over time, filter performance changes.

Wouldn't all of these affect a custom tune? Is a custom tune recommended for summer/winter?

[Circuit Motorsports]

Originally Posted by Turdinator

@moto-mike @Circuit Motorsports can you optimise a tune for a set of headers via e-tune? I was under the impression that it was difficult to get the optimal cam timing when not on a dyno?

Good question!

Short answer is yes, you can optimize a tune for headers via e-tune.

Is it a challenge...yes! Is it perfect...no. Is it better than what can be done on a dyno...no. Can it be close to optimal...yes, very close!

Let me say this first. My tunes, and I'm not alone here, are based on thousands of hours of tune R&D and refinement, performed on development cars on a dyno and on the street, and refinement over time via the experience of tuning many, many cars. I learn something new every day, and apply that knowledge to every tune I perform.

For every tune I perform, whether it is an e-tune or dyno tune, I am starting with a base tune that has all of that R&D and experience behind it. So for a particular header, or other part or combinations of parts, I am starting with a calibration that is going to be in the ballpark of optimal.

I have developed many software tools for tuning (I was a software developer in a previous life and still dabble) to aid in the tuning process. E-tuning presents additional challenges over and above dyno tuning, but careful analysis of data logs can provide the information needed to optimize a tune for headers, along with other parts as well.

When dyno tuning, I still rely heavily on data logs to guide the tuning. Yes, of course the information the dyno provides and the much more scientific dyno environment makes the process more precise, but the data in the logs are most important. One last note and I'll end my rambling here, I always street test and log a car I tune on the dyno. More often than not, I find a few adjustments that are needed after the dyno session.

Please excuse the rambling....think I had too much coffee this morning.


- Bob

[Circuit Motorsports]

Originally Posted by Wepeel

I do wonder about the robustness of custom tunes. The custom tune is done on a dyno in a few hours, under certain environmental conditions, with a certain quality of fuel, with a certain state of health of the engine/sensors. I know the ECU compensates for weather/temps etc, but those compensations are set to be compatible with the stock tune.

Fuel quality varies from station to station, probably even week to week at any given station. Ethanol content, fuel blends/quality, not to mention summer/winter blends. Sensor accuracy drifts over time, filter performance changes.

Wouldn't all of these affect a custom tune? Is a custom tune recommended for summer/winter?

Great topic! It's not so much about the robustness of the tune itself, but the robustness of the ECU in the car and the abilities of the tuner to deal with all of the things you bring up.

See my post above regarding what goes into a professional, custom tune. The variables you mention are definitely factored into the equation.

All of items you bring up affect a custom tune, the factory tune, an OTS tune, EVERY tune.

For variable weather conditions and normal differences in fuel , the ECU and factory software/tune has compensations built in to deal with those conditions within a certain range, and a custom tune changes the calibration so that these compensations now work with the custom tune.

Sensor accuracy, dirty/clogged filters also affect EVERY kind of tune. Again, the ECU/tune will try to compensate within a given range and will generate error codes (DTC) and light the check engine light when it reaches the limits of its compensation abilities and the condition/issue still exists.

The factory tune, and a proper custom tune, will handle summer and winter just fine.

- Bob

[Blu-by-U]

Back in the days of timing lights, feeler gauges and 1/4 degree hammers, every car was different when it came to tuning for the best performance. I may have been out of it for a while (kids can be more fun), but what I'm observing is that the only thing that has really changed, is how we tweek our cars to get the best performance. Yes, there are new features (VVT) that make the engines more efficient, but the engine still needs individual tweeking in order to achieve maximum safe output. Still studying, lots to learn.