VersaTune User Forum

I recently tuned my MAF for my intake. I noticed previously my car actual/desired lamba were off consistently, but after the MAF tune, it seems to consistently have equal or very close desired/actual. Another side effect, was my car, when using virtual dyno, logged 264whp, compared to a previous 286whp. I then decided I wanted to go for more horsepower. In my tune, I was targeting a max 2.015 load, but at WOT was usually seeing a load around 1.9. When increasing requested load, I wasn't seeming to see any power gains. Comparing my tune to your +100 base tune, I forgot I was not uping BCS DC, as it seemed on your tune my load targets were similar, but my BCS DC was quite different. My understanding is if you increase load target, you must increase BCS DS so you build more boost. My fueling and timing seem to be fine for now, I seem to need to want to make more boost. So I have two tunes, v6 and v7. If you look at my logs, I increase the BCS DC, and I see around a 0.7 psi increase in boost, but saw a drop in horsepower. Is this within margin of error (meaning really no real change in boost happened)? Why would my horsepower decrease? These two runs were on the same stretch of road within 20 minutes of each other. Below are screenshots of the applicable charts for each tune, and attached to this post are my tune files, and my full logs. I understand I'm pretty much asking someone to review my logs, if be willing to compensate for time taking a look. Any help appreciated

Something I noticed while reviewing, between 4500-5000 rpm, my BCS DC is set to increase by a decent chunk, but on my logs, when BCS DC is increasing, so boost should be as well, my waste gate is actively decreasing duty cycle, which is releasing pressure. Doesn't my BCS DC table tell the car to make more boost, so why would my wastegate be doing the opposite and releasing all its pressure (bringing my boost down to 15psi)?

Would you mind posting the log with the 286bhp run?

Ok, no need, found your problem: Absolute Limits -> Overboost protection throttle reduction > set those limits to like 230kpa at least (depends on how far you are willing to go and what is the condition of your engine and turbo, what flow mods you have, and so on), and the fuel cut limits 5kpa more (or 1.5-2PSI higher if you're editing in PSI).

mituc wrote:Ok, no need, found your problem: Absolute Limits -> Overboost protection throttle reduction > set those limits to like 230kpa at least (depends on how far you are willing to go and what is the condition of your engine and turbo, what flow mods you have, and so on), and the fuel cut limits 5kpa more (or 1.5-2PSI higher if you're editing in PSI).

Thank you very much for the advice. After thinking today, I thought it was certainly a matter of me hitting some sort of limit. Those tables were indeed set to low in comparison to the Versatune +100 hp. I missed those limits when comparing what was different.

So with that in mind, I upped those limits base off the +100 tune, so I could at least expect to see some sort of change in power. I increased those limits, and lowered my BCS DC in case of more boost than expected, and did a pull. I logged 267hp exactly (power v12). I thought this was good news as it was lower BCS DC than the tune before but the same HP. I then simply upped the BCS DC even more (power v13), but I got unexpected results... 249whp.


I only adjusted the BCS DC. Runs within 20 minutes, again same stretch of road. I was certainly expecting more power, maybe even significantly more power. Im a bit confused here of how I can increase BCS DC by a decent amount along with those other values and see a significant drop in power. Maybe I took it too far and hit another limit?

You mention you weren't sure of my flow mods; my mod list is in my signature. Do you think I maybe should be increasing my load targets? I bought this car from an auction and fixed it up, I knew the previous owner had an access-port, and several cobb mods, reading online almost everything with this setup said to use a HPFP so I assumed I had one. I read the stock one tends to tail off around 1600psi. My car when logging was peaking at 2100psi and was maintaining 1800-1900+psi. My friend has a Speed3 I know has a stock one, I logged his, and the thing always stayed at 1600psi. The distinct difference in fuel pressure seemed to tell me mine was not stock, and so I think I could push higher load targets if needed.

Attached are full tunes and logs. If you have the time to take a look at those logs, I seriously appreciate the input on the tune. My goal is 300+ whp, also know its winter time and very cold so my BATs are very low.

Another question; why is the MAP pressure tables so high? The car only ever sees like 18psi max, so why are the tables in the 30s for psi? Is there some sort of scaling I'm not understanding? Same with the MAX MAP before throttle reduction. Even the Stock limits are 30.75psi. How do I relate this to real boost pressure I'll see?

It's because the manifold pressure is absolute, it takes into account the atmospheric pressure. So for instance, in my area the atmospheric pressure is 14.5 PSI, so if I want to target 20 PSI I would need to put 34.5 PSI in the table. I'd also highly advise you to get an e-tune so you don't blow your motor.

Polish_Eagle wrote:It's because the manifold pressure is absolute, it takes into account the atmospheric pressure. So for instance, in my area the atmospheric pressure is 14.5 PSI, so if I want to target 20 PSI I would need to put 34.5 PSI in the table. I'd also highly advise you to get an e-tune so you don't blow your motor.

Okay, I understand now, thank you. Im not too concerned about blowing the motor. I want to learn how to tune and I closely monitor knock retard/load/boost. If everyone took that approach, we wouldn't have any tuners.

With that in mind, those tables are currently limiting me to around 18-19psi which shouldn't be limiting me making more power anymore.

suchamoneypit wrote:With that in mind, those tables are currently limiting me to around 18-19psi which shouldn't be limiting me making more power anymore.

Mind that once you get past a certain load (which means air flow, not necessarily boost) the timing tables are very very conservative. Once you're happy with the boost you're getting you should look into tuning the timing advance accordingly to the fuel you're using usually in your car.

mituc wrote:

suchamoneypit wrote:With that in mind, those tables are currently limiting me to around 18-19psi which shouldn't be limiting me making more power anymore.

Mind that once you get past a certain load (which means air flow, not necessarily boost) the timing tables are very very conservative. Once you're happy with the boost you're getting you should look into tuning the timing advance accordingly to the fuel you're using usually in your car.

Ok so I think part of my problem is tuning for my intake has thrown off my load. I'm hitting 1.9 load but not making near the power I want or was getting before pre-maf tune. The car is making much less boost than I want (and less than it ran for months before the MAF tune). So I should be increasing my load targets to make that target power/boost ? Doesn't explain why I saw 18hp less by increasing bcs DC. I suppose nothing to bad will happen as I'll either make a bit more power as I want , or nothing will happen as some other table is restricting my power if I increased requested load a bit.

Unrelated but I do have a Cobb EBCS coming to help with better boost control, I figured that would give me better results with tuning (I know I'll need to readjust my BCS DC table).