Boost Cut Engaged Below Parameters

[jgauth4468]

Greetings All,

I've attached the tune on the s300 ECU and the Datalog.

Issue: During full throttle acceleration, boost cut engages at ~4800-5000rpm (approximately same time vTEC engages), resulting in a sadness. I know I can go partial throttle, but full-throttle is an always results in the boost cut. The datalog shows peak MAP reading of 8.8-9.0 psi, which matches the digital gauge (signal of separate sensor on intake manifold). I've combed through the parameters, and have my boost cut set well above 9psi (set to 14 psi). This occurs regardless if in 2nd or 3rd gear. Only been doing rolling start pulls, so haven't tested 1st.

I'm sure more information will be needed / requested to assist with this. Let me know what additional info you need to guide through this issue.

The current setup is running on wastegate ONLY, no boost-control solenoid, and wastegate looks like a 8psi spring (ish).

Thanks

Josh

[jgauth4468]

Update, I am going to alter the vTEC engagement RPM setting to see if it alters the Boost Cut, and also try without vTEC too. My opinion, these two steps will see if the issue is related to vTEC.

Still will be open to advise, recommendations and things to look at.

[Spunkster]

It sounds like it could be a grounding problem and it is grounding through the VTEC solenoid. Check the grounds in the engine bay and make sure that the thermostat housing grounded is connected correctly.

[jgauth4468]

Spunkster & Others,

I will take a look later today / tomorrow, and get the multi-meter out to verify the VTEC solenoid is grounded.

I did three 2nd gear test pulls, and the issues is associated directly to vTEC engagement.
Test 1: vtec set at 4750rpm
Test 2: vtex set at 5250rpm
Test 3: No VTEC

Results: registered a Boost cut at the VTEC set RPM in Test #1 & #2. Test #3 was able to keep pulling (stopped at ~6k rpm). I say "Boost Cut" as that display indicator lights up when the VTEC rpm is reached and the engine loses power (ignition and fuel are pulled). I do have oil pressure logged in the datalogs on one of the Analog inputs (for some reason I think it's recording in bar, not psi, so math would need to be done, but the pressure is healthy).

I have attached the datalogs and tunes for reference.

I appreciate the guidance.

[jgauth4468]

logs and tunes used (not sure why it didn't load the first try)

Forgot to put the details in the initial post.

Hondata SManager 2.7.5.0 Build 1435
Vehicle: 94 Del Sol
Engine: built d16y8
P28 hondata chipped ECU
Mods: Bored Y8 block with deck plate, YCP Pistons (+0.5mm), SCAT rods, Crower Turbo Cam, Springs Retainers, AEM Cam Gear, Skunk2 Intake and Throttle Body (deleted IAC valve and Fast idle), MSD 6AL (plus coil, cap and rotor), Bullseye T04e Turbo, 4bar Hondata MAP, 440 injectors (forget which ones), walboro fuel pump, -8AN fuel feed with high flow filter, rail and regulator. Driveline is built to support, but shouldn't be a contributor to this issue. Turbo is oil cooled / lubed, and fed via -4AN using a filter sandwich adaptor (same location the ECU is measuring oil pressure too).

[Spunkster]

Post pictures showing your engine bay grounds.

[jgauth4468]

Hello Spunkster,

Attached are the Engine, Trans and Thermostat Ground pics. I have verified that all grounds are grounded via multi-meter and visually (no paint, rust or grease adding resistance). I did ground both the valve cover and the cylinder head (never understood why Honda put the ground on the valve cover, since it's pretty isolated with the cover gasket, spark plug tube rubber seals, and valve cover bolt rubber seals).

Checked the vtec solenoid housing to ground and got 0.1-0.3 ohms. Haven't used the Hondata to test the solenoid actuation yet, nor have I checked the pressure sensor voltage signal from the ECU... other things popped up that got me busy for a couple days.

Question: For a "boost cut" condition, is Hondata monitoring more than just MAP pressure (example, A/F, timing, duty cycle, etc.)? Meaning, if the MAP is OK, but another parameter is not, "boost cut". Also, what's the frequency that hondata is check MAP v datalogging? Is there a potential that a "micro-creep" occurred (MAP signal above boost cut threshold for 3ms) the hondata says "cut", but that blip is not registering on the datalog?

[Spunkster]

The ground on the valve cover is not on the correct position. It must be on the valve cover studs as the valve cover is rubber isolated.

The thermostat housing ground does not look clean and even bolt appears to be corroded.

The other ground I cannot see where it goes from there.

[jgauth4468]

Spunkster,

Just updating you. Small setback. My MSD 6AL crapped out, so, bigger issue to address (need to pull the box).

The cylinder head is fully grounded via woven ground strap to directly to the head. I have verified it's grounded via DVOM. I've also confirmed that the VTEC solenoid is fully grounded too. I will run standard Honda Service inspection diagnostics on it once I get the MSD sorted out.

The Trans ground goes directly to the strut tower battery ground location. Connection is good. Confirmed via DVOM (and had to address a starter issue after the trans rebuild and painting the case).

I cleaned up the thermostat ground screw and wire ends as recommended, and also used a little dielectric after assembly to help protect that area from moisture & corrosion. It was after that cleanup, that I went out for a test drive, and lost the MSD (made it 1/4 mile from the house; ugh).

Ah, toys are fun.

Will update once I get the time to replace / rebuild the 18 year old MSD 6AL... decision... update to the digital 6AL, or have MSD rebuild the old unit?

[jgauth4468]

Spunkster

Got the new MSD in, back up and testing with cleaned up grounds. Still get the "boost cut" at VTEc cross-over.

I did check the solenoid resistance. It passed. I also checked the pressure signal circuit from the ECU, it shows 12v at key-on.

I know that I can use s300 to test ECU outputs. If I back probe the VTEC solenoid with my oscilloscope, can I test the VTEC output on the ECU with the Engine off? Of course, this would be after verifying the circuit line resistance shows no issue. This would enable to verify is the ECU is sending a signal. If no signal... sad time, need an ECU.

Please let me know if I can test the VTEC output with the Engine Off.

Thanks

[Spunkster]

You can test all the outputs listed when you go to the online menu and click test outputs.

[jgauth4468]

Spunkster,

Seems that all signs are pointing to ECU being NOK. I verified line resistance from A4 ECU connector to VTEC solenoid and get 0.3-0.5 ohm (passed). With Key-On/Engine-Off, I Test Outputs, and see no alteration in that line voltage, nor is there any audible "click" of the solenoid. Based on this, I assume a NEW ECU is required.

Looking for confirmation on new ECU, or some other test.

Thanks for the assistance, and brainstorming, on the issue.

-J

[Spunkster]

I would recommend you try the ECU on a known working vehicle to see if the problem persists.

[stephancrxboosted1]

hey did you fix the problem?? because i think i have maybe the same issue...

[jgauth4468]

Status update 10-MAR-2022:

Snow is gone and temps are finally warming up to the 40’s, so can continue diagnosing. Fixed a small coolant and fuel leak, now to focus on VTEC.

I resolved the IAT code. “Someone” (cough, me... idiot), had the wrong connector on the sensor. Thank you Honda for not having a poke-yoke on the connectors.

I get a IAC code 14 now (IAC)… no surprise, I got rid of it when I did the skunk2 intake and throttle body (deleted IAC, along with FITV, EVAP, etc.).

Can an IAC or other Code impact VTEC actuation?

I can use the test inputs function, and while holding 3,000+ rpm can command on vTEC. Therefore, I know two important things: 1) the entire electric circuit and ECU function and work, 2) the ECU has control of the solenoid. During the test outputs function, it generates code 21 VTS VTEC Spool.

Is Code 21 normal during a test output actuation of VTEC?

I have to FULLY test / pin-out the VTEC pressure switch side of the system. I am "assuming" the switch is OK, as the entire VTEC assembly is new, from when I did the engine rebuild. I have confirmed battery voltage multiple times on the ECU signal wire to the pressure sensor. I'll update on this testing in the next day or two. Unfortunately, All Data service site does not show where Ground G100 is within the engine bay... Diagram simply states G100 (Right side of Engine).

Unfortunately, I'm a lone tuner in SE Michigan. I don't have access to a known working car that I can swap the ECU with S300 into and test. The ECU is from a respectable source in the "Honda Acura Motorsport" world, so I'd like to believe that it's functioning 100%

It's my opinion that the ECU is looking at a sensor or parameter as part of the VTEC logic, and because the input requirement isn't being met, it's prohibiting VTEC actuation, and treating it like a boost cut.

I'm open for suggestions and recommendations as I work through this.

Josh