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Discussion Starter #1
So this issue of mine has been going on for about a week and a half now. Ill describe it has best as I can.

When I am full throttle or part throttle accelerating and I pass the lower VTC point (4800) the VTEC initiates....ONCE I SHIFT AND THE RPMS DROP BACK OUT OF VTEC and I rengage the throttle, there is a bogging/lag...almost like a fuel cut until rpms reach the same vtec point again and then everything acts normal. If I go far enough into vtec that when I shift I DO NOT drop back out of vtec, the car acts fine. The occurrence only happens when I go into vtec, shift, rpms drop out of vtec, and i try to reaccelerate. It feels like the low cam is not being re-engaged for those couple hundred rpms that im not in vtec OR there is a fuel issue at that point

The problem happened out of nowhere one day. I have been running my dyno tuned map up until now with no issues. I am making 230whp, I have an rsx type s and my mods are cai, 4-2-1 header, 3" thermal r&Dexhaust, kpro, rdx 410 cc injectors, rbc, golden eagle fuel rail, drag cartel drop in cams. Very straight forward. Ive updated kpro, reuploaded the original dyno tune map several times so i dont thing its an ecu issue. I think it could possibly be my vtec solenoid not disengaging correctly, so its not switching back over to low cam once i drop below the vtc point. Could be a fueling issue but everywhere else in the power band the car acts just fine.....thoughts suggestions?

I got with an etuner and we have been making a new map from scratch...the strange behavior has become noticeably smoother but its still there. Map sensor reads normal as well as the tps sensor....this issue happened one day out of nowhere right after i filled up (only use 93 octane)...that gas station ran out of 93 the night before so if i sucked up some bad gas idk how that would translate to this issue...but i have since then cycled that potentially bad gas out and the problem is still prevelent
 

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Arouse the DAMPFHAMMER!
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When I am full throttle or part throttle accelerating and I pass the lower VTC point (4800) the VTEC initiates....ONCE I SHIFT AND THE RPMS DROP BACK OUT OF VTEC and I rengage the throttle, there is a bogging/lag...almost like a fuel cut until rpms reach the same vtec point again and then everything acts normal...
Hi maverick_dc5, to think loud:
  • ECU needs MAP and engine speed to know where the engine operates for fuel control
  • in addition, it must know if VTEC is engaged or not
  • in addition, it must know where VTC is
  • ...and so on
It could be that when you accelerate with WOT, go through non-VTEC into VTEC that the engine knows ok, there is a switch point. Once engine speed fall below VTEC engage rpm, propably the ECU don't know about operating in non-VTEC area and feed too much fuel into it because of high speed cam fueling...you maybe would see it at the spark plugs (black colored electrodes). But of course you can see it also in the datalog, just check for the parameters VTP (VTEC pressure switch) and VTS (VTEC spool valve) both are directly active when VTEC pin is locked to high speed cam (value = 1 of both). Both values get zero once engine speed drops below VTEC engagement engine speed.

If you have problems to check it, let me know it via PM, I would check your datalog.

Markus
 

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Discussion Starter #3
Hi maverick_dc5, to think loud:
  • ECU needs MAP and engine speed to know where the engine operates for fuel control
  • in addition, it must know if VTEC is engaged or not
  • in addition, it must know where VTC is
  • ...and so on
It could be that when you accelerate with WOT, go through non-VTEC into VTEC that the engine knows ok, there is a switch point. Once engine speed fall below VTEC engage rpm, propably the ECU don't know about operating in non-VTEC area and feed too much fuel into it because of high speed cam fueling...you maybe would see it at the spark plugs (black colored electrodes). But of course you can see it also in the datalog, just check for the parameters VTP (VTEC pressure switch) and VTS (VTEC spool valve) both are directly active when VTEC pin is locked to high speed cam (value = 1 of both). Both values get zero once engine speed drops below VTEC engagement engine speed.

If you have problems to check it, let me know it via PM, I would check your datalog.

Markus
thanks man..i have a datalog of the phenomenon already that i can send you ill pm you
 

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Discussion Starter #5
hey marcus sorry i have been busy with the military....problem is still ongoing...i checked my datalog and yes like u predicted the vtp is on when it shouldnt be...below the vtec point....what would suddenly cause this? possibly throttle being stuck open?
 

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Arouse the DAMPFHAMMER!
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...i checked my datalog and yes like u predicted the vtp is on when it shouldnt be...below the vtec point....what would suddenly cause this? possibly throttle being stuck open?
First the configuration of ECU (Parameters and Tables, e.g. some use it for AC switch as Hondata offers that option) has to be checked to confirm everything is right choosen and does not cause the issue...

...second VTEC need both, engine speed and MAP. If the VTEC pressure switch doesn't go into non-VTEC-modus, when VTEC already did a hardware check is necessary.

Feel free to send me the calibration and log (didn't see any of yours up to now).

Markus
 

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Resurrecting this from the dead but wanted to see if there was any solution since I'm having the exact same problem. Mainly seems to happen when I don't take it all the way to redline, aka hit vtec then shift up at 5800 rpm. Pulled head back apart and inspected rocker assemblies and everything looked good. Also tried a new VTEC solenoid assembly with the same results.
 

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Arouse the DAMPFHAMMER!
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Resurrecting this from the dead but wanted to see if there was any solution since I'm having the exact same problem. Mainly seems to happen when I don't take it all the way to redline, aka hit vtec then shift up at 5800 rpm. Pulled head back apart and inspected rocker assemblies and everything looked good. Also tried a new VTEC solenoid assembly with the same results.
What is the exact code you got from the MIL?
 

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Arouse the DAMPFHAMMER!
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No MIL unless it goes on too long and I get a misfire warning.
You have KPro or similar? If not make sure vehicle speed, gear, MAP and VTEC pressure signals are valid and well connected to the ECU. Normally, if those aren't available for the ECU it throws a code. If not a by the ECU non-observed mechanical issue like oil pressure after VTEC valve (VTEC and VTC valve filter check!) can cause also a similar issue. If you have logging possibilities, log it and share it please. Otherwise there is too less information available for me to condense it more down.
 

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Arouse the DAMPFHAMMER!
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Thanks for the files. The KTuner SW is restricted only to KTuner hardware users, which is pretty much anoying, therefore thanks for the *.csv.

Observations and recognitions:
  • If TB has no blocker at 81 % the TPS definitely need an calibration process or better you buy a new one. If this is a cable wire TB, ECU signal to position signal has a very strange behavior or your feet is faster then a lightening strike 😉
  • low speed VTC map makes no sense to me from around 3700 rpm till VTEC switch point at roughly 4700 rpm. No engine would like this at low speed cam, after seeing low speed peak VE at around 2270 rpm. You likely loose massive torque before VTEC switch point!
  • I saw many work from other tuners, but this is one of the worse (not to say worsest) tuned fuel maps: WOT AFR's from 13.1 down to 10.8, leading to engine speed drops of up to 64 rpm (!!!)during WOT acceleration! I never saw such a mapping, you even see the drop in AFR there, from a wideband which has a 60 ms T60 time...this really need work to do:
    • Tip in lambda goes lean to 16:1 in AFR
    • WOT lambda is way to rich in general, on a precise tune or your specific engine it should have around 12.9:1 to 13.2:1, depending on application you run it, but WOT lambda has a precision of maximum +-2 hundreds (lambda, around max. 3/10 of AFR at maximum), here precision is up to +-11/10 AFR's, more then 3 times of it! If a tuner want to risk an engine, it should looks like this quality of fuel tuning! If a race engine need an endurance setup like for an 24 h race, even then I would applicate the same WOT lambda for all engine speed points. There is no any ever fu...cking reason to fill up the engine with almost 30 % of unused fuel just to cool down an I4 NA engine of that BMEP!
Sorry for my emotional critismn on that tune, but whenever I see such a work, I feel the pain of the engine which it must go through every day. I really recommend you to go to a proper tuner to revise it. I can't revise it, as KTuner SW need an around 400 USD hardware dongle to get it run for remote tuning. I do remote tuning for race engines all over the world since years, but not for KTuner customers. We have to few around the world to get the 400 USD amortized.
 

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TPS max of 81% is actually normal to this application according to Ktuner, not really sure why though. Looked in the csv and I see what you're talking about with change in TPS% happening immediate (30% change from one datapoint to the next). Don't know if that's normal or not, the datalog in Ktuner doesn't look bad when plotting it.

I appreciate the critiquing. I'm actually the one trying (struggling) to tune it. Not really understanding some of the decisions the ECU is making though. In another log I can see a big step change in fueling but based on the fuel maps + corrections there shouldn't have been almost any change. The VTEC issue completely baffles me though, I couldn't imagine a poor fuel map to cause it but I can't seem to find any other culprit either. The lack of help/support for Ktuner has me highly considering switching over to Kpro and its stronger userbase.
 

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Arouse the DAMPFHAMMER!
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Is there any plausible explanation why the TPS is limited to 81 % and considered to be normal? Just curious :)...but I still would focus it's proper function and measure the voltage output of it at closed and fully open TB. Just for confirmation of the extrem values.

Oh, if you need help and switch to KPro or Doctronic (way better value for the price) I can support you if you have struggles get it tuned. Tuning work is reading with attention and patience, with a bit of knowhow and much passion for doing the setup quality right.
 

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Arouse the DAMPFHAMMER!
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Maybe you should make a DIY thread on how to tune the K series ;)
Not intentionally 😋.

I have always wanted to mess with mine but don't feel like spending $500 for someone to tune it.
Understood. Tuning isn't that difficult, even I can do it :D! Did you start to tune your engine yet?

I see alot of tuning stuff and training courses around here and there. Is there a need to do a write up here? Getting into the stuff is, for my perspective, very easy. Just do it!
 

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No I haven't messed with it at all. Done tons of research but don't want to spend money for a dyno so I plan on street tuning a little. Just haven't had the motivation to do anything yet.
 

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Arouse the DAMPFHAMMER!
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For moderate setups there are often basic calibrations available to get it started. Street tunning can be suffcient (not a must), but needs experience and specific knowledge about engine communication and engine needs (similar to handling a GF or wife :D).
  1. The easiest part is fuel tuning. Basic concept of mine here is: tune all VTC angles complete and to a tolerance of +-0.02 points in lambda. This is a necessity for the next step.
  2. The challenging part is the VTC map, if the fuel maps are done right, a first order assumption can be made out of the VE or injector duration. It has a high likelyness that when VE is higher on e.g. 50° VTC comp. to 40° VTC that the torque does it also.
  3. The most challenging part because the highest effort needs done on ignition timing. At WOT it is easier, the engine speed rate wins. On part load it is more difficult, but can be seen out of the mpg (~ injector duration / engine speed) on each point
That's all what you need to do. Just do it!
 
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