[Kthen]

Hi all! Just seeking some advice for an issue which has been unsolved in the last week.

Setup is a stock block K24A3 with a PRB 4Piston 156v2 head, supertech valve train and DC3.2 cams. Kprov4, 725cc Bosch EV14, Walbro 725cc, OEM returnless fuel system.

Now the issue is that the car is not interested in crossing over into VTEC without bogging down.

Verified good fuel pressure at crossover, constant 50-52psi.

We have already tried the following:

Mechanically:

New coils, new map sensor, new spark plugs (brk7e), new terminals on grounding cables on valve cover. Checked fuel pressure in VTEC.

Electronically:

Engaged at varying points, 5k up to 7k with 500rpm increments.

Engaged at varying cam angles, 0, 10, 20 and 30deg.

Engaged at varying AFR ratios, 11s, 12s, 13s and even in 14s.

Cam angles are as commanded (some times off by target by 1degree if that matters?)

Knock control turned off as we're tuning on our Dynapack chassis dyno with proper knock detection.

Low cam maps (low cam, 0, 10, 20 and 30deg) tuned out mint. MBT: 24deg low/mid load, mid rpm, 32deg up low mid/load, mid/high rpm, 25deg WOT with a 1-3deg variance between the angles.

Low cam AFRs within 1-2%.

Still to no avail.. Would like to point out that the vehicle was running on prior to head swap. VTEC was working fine without any issues.

We're in the midst of installing oil pressure sensor for the Kpro, will log oil pressure and keep posted.






FIXED 23/01/2023 - Was faulty VCT cam gear which has been replaced with a known good one. Issue is gone!

 

[Lotus]

do you get a VTP signal from sufficient oil pressure? Without it won’t even engage the high cam, throw a code and runs into the low cam rev limiter. This is unless you disable VTP.

 

[Kthen]

Yes, I have VTP logged and the status is always at (1).

High cam is engaging, it just doesn't like it 😭

 

[LotusElise]

I would be interested in logs and calibration to see more.

 

[Lotus]

may sound odd, but maybe these spark plugs are unsuitable, e.g. too large of a gap.
This could blow out the spark right after hitting the high cam.
As a temp measure you might increase dwell time a tad or gap them smaller.

 

[Kthen]

I forgot to add to the list - dwell was bumped up whilst on the dyno with no luck. However, we have yet to try new spark plugs!

What would you recommend for this setup? We were thinking BKR7EIX gapped to 0.6mm?

 

[LotusElise]

We were thinking BKR7EIX gapped to 0.6mm?

These are my favorites, reliable, efficient and durable in harsh environments (tuning under knock situation, lean operation under tuning situations) for the NA-K-series engines. Your suggested gap size is ok to start with on a 10.5:1 CR.

 

[Lotus]

COPs are easily saturated as they are so small. Could be that the factory settings are already "charging" them about as high as it gets.

 

[LotusElise]

COPs are easily saturated as they are so small. Could be that the factory settings are already "charging" them about as high as it gets.

Yeap. There is a table available were the charging time is set over engine speed. What I saw, there are two types of Inductivity available, the old type of around 2.3-2.6 mH and the other type around 4.3-4.6 mH. Both are from DENSO and under the same part number, just different years. Switching forth and back makes a difference if you don't adapt the table.

 

[Kthen]

Will give this a crack this weekend and report my findings

 

[Kthen]

Problem solved: Was a faulty VCT cam gear after many incorrect diagnoses.