Big turbo tuning with stock manifolds

[mituc]

Unlike that world, we don't have access to injector data in order to make the kind of changes needed to rescale a table the way the domestic world does.

I'm talking 100% versatuner context.

[ZeroDCX]

Unlike that world, we don't have access to injector data in order to make the kind of changes needed to rescale a table the way the domestic world does.

I'm talking 100% versatuner context.

I think CrazyCanadian was referring to my previous post. I do have a touch of experience in the domestic world where tuning software allows us to rescale certain table constants (e.g., tuning the EEC-IV/V). However, I was referring to reducing the MAF g/s values past a certain voltage (e.g., 3V) for AUX tuning to blend in the PI and maintain load-based protections/tuning strategy in my previous post.

I did some more poking around and would like the opinions from someone with more tuning experience. I've recently installed my JMF V2 intake and port injection. However, I'm still running on DI at the moment. With mid-throttle acceleration, my car feels pretty peppy. However, during WOT pulls it feels like something's holding it back. Initially, I believed this was due to the limitations of the stock intake manifold. However, I decided to clean around the engine bay as much as I could (to remove debris) and try a 3rd gear WOT run w/o my air filter. During the pull, the car felt slower than stock. After examining the log, I found my actual AFR dipped in the 9's. However, with the air filter on my AFR tracks my desired AFR within =/- 0.3. I've attached the logs below. Between these two logs, there we no changes in the tune.

I'm thinking the air filter is a restriction and I was tuning around it. Thoughts?

For clarification, I'm providing more details on my intake setup:

• AEM (K&N) dryflow air filter
• HTP 3.5'' recirc intake with a air straightener
• Turbosmart BPV
• Corksport FMIC

[mituc]

In the log without air filter (mentioning "no air filter" just for reference with no direct connection to what I think it happens) the symptoms are of a boost leak. Let's look at the 6000rpm mark:
- with air filter: 322g/s of air at 20PSI of boost and 119F BAT, AFRs on target;
- without the air filter: 359g/s of air (more than 10% over) at 17PSI of boost (like 9% less MAP), at 120F BAT (identical), AFRs in the high 9s.
So you either went too optimistic with the MAF calibration from a tune to the other (there seems to be a small difference or no difference) or you developed a boost leak between these two logs. The air filter plays a role in airflow readings at low air flow values, but at higher flow values (and think 12-15g/s, not 100+) the air straightens itself through the intake. The larger the intake the higher this threshold will be and the higher the air filter quality and design will be up to that threshold, but even on a 4" intake it's well below 20g/s. So with or without filter doesn't matter as long as your filter is not clogged.

[CrazyCanadian]

Yes air filters can be a restriction, but I don't think that's what you are seeing. An air filter is going to effect the path the air takes as it flows into the intake tube and across the MAF sensor. This will effect how much air the sensor is sampling which screws up it's calibration.

[ZeroDCX]

Based on your feedback, I went back and checked for boost leaks with my homemade boost leak tester (using a similar tester to the one described here). Other than a pin-hole leak in the MAF housing to intake tube weld, I didn't find anything obvious using soapy water and pressurizing the system to almost 30 psi. However, I've ordered a proper boost leak tester kit to double-check everything later this week/weekend. I also went out and took four more logs in this order:

• 93 Octane r2 - 3th Gear #6 (with air filter) - 2025-10-05 15.16.42 -> 1st Run: With the air filter
• 93 Octane r2 - 3th Gear #3 (without air filter) - 2025-10-05 15.22.21 -> 2nd Run: Without the air filter
• 93 Octane r2 - 3th Gear #7 (with air filter) - 2025-10-05 15.26.22 -> 3rd Run: With the air filter
• 93 Octane r2 - 3th Gear #4 (without air filter) - 2025-10-05 15.31.25 -> 4th Run: Without the air filter

For verification purposes, no tuning changes we made between runs (i.e., my car is still on the same tune as my last post). They were all taken relatively back-to-back (only stopping to remove and insert the air filter, and giving the car a brief cool down period). The results show similar findings to my last post. With the air filter, the car is relatively close to the desired AFR, etc. Without it, it runs rich often hitting 9.9 or lower AFR during WOT. From what I can see, the MAF g/s vs V readings are way off w/o the air filter on, which causes an overload condition (i.e., my target load is 2.1 from 3k RPM-onward). Then, the ECU mitigates this by reducing WGDC and switches to using the overload timing and AFR tables (and may blend them with normal tables in some cases). After inserting the air filter, my WOT pulls are 'normal'(-ish). At the moment, I've cleaned the air filter and will take another set of logs to test and see if everything remains consistent with my previous logs (with it on), or deviates in any way, and post my findings. I will (more than likely) also look into a larger air filter just in case too.

Appreciate you both for feedback!