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Whats the scoop on vtec and no primary and secondary O2 sensors. A million honda guys say vtec won't engage, and and equal number say "no 02 only causes a constant openloop mode thus NOT inhibiting vtec." Point is, I'm not getting vtec at ALL. I have emanage vtec set to 3500rpm. Emanage problem or 02? No vtec CELs.

Before you guys say limp mode, I can tell you, the car isn't limping from not having both O2. I am in constant open loop but i'm not running rich either. The air/fuel is perfectly corrected for (14.7AFR @TP45%- under. I can still rev to about 7000 so that throws limp mode out of the question (I think!?)

And before you guys say "just plug it in!"....wait till u guys try it, the throttle response is 10000% better in constant open-loop mode. U'd love it.

I know I have no vtec because I can feel the car plateau in power midrange. My old LX motor pulled WAY harder underboost cuz I had two full intake cams back then. Now I got the 1 cam if i'm off vtec...and thats what it feels like-half *** boost.

 
Rep Power: 811

if the engine light is on, you are in limp mode. doesnt matter what caused this (unless its just the secondary 02 sensor broken). so no vtec for you. its not a good idea to force it either using emanage. best to let the ecu take care of it. conditions depend on more than just rpm.

 
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So you're telling me just cuz you have a cel on, it means you're in limp mode? I don't think so becasue limp mode is a fairly notable condition where a major sensor ie MAP is toast and the car limits the engine to a point where it literally limps to get around to prevent further damage. Isn't the lack/faulty o2 just mean that the ecu will use a really enriched fuel map based off other sensor correction factors? I mean losing an 02 isn't a big deal in the grand scheme of things since it happens to all cars eventually....and you don't use that sensor when you're WOT anyways. It makes no sense to be in limp mode b/c that sensor is lost.

Not that I'm doubting you gearbox, you might be right, I just wanna get it straight cuz i hear a lot of opposing opinions and a lot of poeple are quick to use the term limp mode for everything when in actual fact it isn't.

 
Rep Power: 317

ummm...if you're profile is accurate, then you don't have vtec...sorry!

your profile says that you drive:

Vehicle Year:
2001
Vehicle Make:
Honda
Vehicle Model:
LX
Body Style:
cpe
Vehicle Color:
SSM

ONLY EX HAS VTEC

 
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I swapped motors..... cmon, i'm not that dumb to think an d17a1 motor to have vtec.

 
Rep Power: 811

well just so you know, many things need to occur for vtec to engage, and even then i have never actually been able to feel it. it just happens, and the whole point is to smoothen the torque/hp curve so that power transfer is gradual. it was never meant to be like a turbo boost lol. so, for vtec to engage, meaning the solenoid changes the cam profile to allow all valves to open, these conditions must be met: coolant temp must be hot enough, oil pressure must be hi enough, rpm must be above 4500k, and throttle at 100% (floored gas pedal). only then will a 12v signal be sent to the solenoid to activate it. if the cel is on, you are almost guaranteed never to have vtec engage. depends on what is wrong. alot of times, the engine will not rev past 4k rpms, or it will modify the shift points for an auto. it will never drive the same when the cel is on. believe me i know, and keeping a code reader in the glove box has helped me quite a bit.

 
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Yeah I know about the onset conditions for vtec, and I know our vtec-e doesn't do all that much. I read the codes off my ecu about every week. Thing is, I want to know if my vtec doesn't come on because of the emanage or the lack of an 02 sensor. Some guys with b16s claim that they still have vtec engagement even when they run straight pipes and all sorts of mod causing all sorts of cels. In fact, a lot of tuners do that and still have vtec. And then theres some who say they don't get it under limp.

 
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alright... i didn't know you swapped motors...sorry if i offended ya. you just never know with some people on these forums! haha.

 
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whats limp mode?? so all those boosted guys who have "unplugged" their O2 sensors cuz their boosted is bad?? my tuner told me i would get a better tune if i unplugged my o2 sensor because the car would wanna correct itself all the time.. is this true?? i wanna make sure i keep the care safe?... wats limpmode please tell me someone

 
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the LX coment was hilarious!

 
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its when your ecu limits the cars performance by cutting rpm at lower than redline, or changing the shifting, or something else. you need the primary 02 sensor at least, the secondary one closer to muffler is just for emissions and doesnt affect performance.

 
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You wouldn't necessarily get a better tune by pulling the o2. It just allows you to control your desired fuel trim at all times instead of just cold and WOT conditions(WHEN USING A PIGGY BACK. People always complain about the AFC and emanage being taken over by the stock ECU and their adjustments don't do anything. Well of course, because the ecu ignores all your correction settings and bases its fuel off the voltage from your o2 sensors.

Thats why I did it. I also found that my throttle response was much better. But gearbox MAY be right, I might have lost my vtec in doing so.
Apparenly limp mode is not the real term that honda uses. Its "Fail Safe" mode, which pretty much limits your car from reving past a certain point and it runs rich to prevent detonation. Anyone in fail safe mode will certainly notice the boggin and rev limiting.

I just want to know if I am technically in that mode (no vtec) or is it something else which is causing me to lose vtec.

 
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id guess something else

what, i dohno

 
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just because a CEL is on does NOT mean you are in limp mode. also, just because you don't "feel" vtec doesn't mean it's not engaging. it's a vtec-e system, it wasnt meant for performance.

 
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I'm with you on that about the cel and limp. But I'm pretty sure vtec doesnt come on for me cuz the car levels out in power compared to my A1. Nor is there any change in the valving sound. Feels like i'm at 120HP peak @ 4000rpm set at 7psi. Sure, I got boost coming into the IM, but chokes up at the cam and the lack of flow is causing my power loss. I was doing at least 175HP on my A1 same boost, same AFR.

Still, anyone with the definite VTEC and no o2 answer? Does No o2 = limp? If yes > Does limp = no vtec?
If no, why don't I have vtec?! Hell, I don't even want vtec, I just want 2 full intake valves. GRrrr.

 
Rep Power: 258

1st: On a single cam, there will be no noticeable change in the sound of the valves when vtec engages. That profound sound is only common on DOHC motors.

2nd: No primary 02 sensor will cause limp mode (im pretty sure). Limp mode probably ='s no vtec, however you wouldnt be able to notice it anyway.

 
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EDIT: Disregard the following paragraph, I was misinformed.
The D17 runs on 3 valves when not in VTEC. When you go above 4500, it only opens an exhuast valve, so you're actually always running on both intake valves. This is why it's called VTEC-E (E=Exhaust).

I wish I could offer a suggestion to your issue, but I thought I'd throw that in . The only suggest I can think of is to put the primary o2 back in and see if you have VTEC. If you do, then it's that, if not then it's something else most likely.

 
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what you mean it opens an extra exhaust valve? it opens another intake valve not exhaust.... it runs in 12 valve mode until vtec where it opens another intake valve in each cylinder at a slight offset to create a swirl in the chamber. http://asia.vtec.net/spfeature/vtecimpl/vtec1.html go down the list a little ways it has a good explanation. as far as i know none of the sohc engines alter the exhaust valves during vtec

 
Rep Power: 243

I have my o2 sensor unplugged and my vtec kicks in for sureee cuz the car pulls hard straight till 6800

 
Rep Power: 253

civic-driver: our d17 sohc vtec is not your run in the mill vtec its vtec-e (which i dont think stands for exhaust it stands for economy). prior to vtec-e in a d17 the engine runs on 3 valves to preserve fuel. when vtec-e "hits" the engine runs like a normal 16valve engine. so vtec-e is rather a waste of our time in the d17. i think of it as we might as well not even have a vtec in our cars, i would think that a non-vtec d17 would be better so to say. IMO.

 
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emjay: you have vtec w/o o2? See, thats what I wanted to know. Anyone else have any solid facts?

 
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ummm i didnt say our car was a run of the mill vtec? that is the vtec -e description. the link shows the vtec-e a little farther down. and yes it runs like a normal 16 valve during the vtec engagement and a 12 valve mode while on the lower camshaft lobe. it runs on three valves , two exhaust and one intake. thus creating the economy swirl until vtec where the inactive rocker arm is activated to open the intake valve that has not been opening to help get the normal power from the engine in more "demanding" circumstances. sorry that i wasnt clear in the last post it was really .

and drifteR i had a thought. if you wanted the care to have both intake valves open the whole time would it be possible to make it bypass the ecu and just send it your own 12v signal from somewhere else? this would engage the pin so that you would be in 16 valve mode at all times kinda like the A1 head you used to have. im not sure if it works in practice but it was a random thought. hope you get this figured out

for the record i agree that the a1 is a better because of the lack of vtec-e and the constant 16 valve mode. better for mods not mpg when treated properly.

 
Rep Power: 248

isn't the a1 a lower compression motor?

 
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bakertime called the E in VTEC-E is for Exhaust lmao lmao wow the misinformation that occurs on this site....

 
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Sorry guys, I had it described to me that way. My bad.

 
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the compression difference is 9.5:1 for the A1 compared to 9.9:1 on the a2 . im not sure if the compression comes from a different piston or if it is something else in the head. they have the same stroke and bore. the a2 bore is a little smaller if i remember correctly but dont hold me to that one. it is not a huge difference.

 
Rep Power: 330

^it's just a different piston. i think bore is the same.

^that sums it up right there...

you want to know if vtec is engaging? hook up a digital multimeter and find out. hook up the red probe to the vtec solenoid output at the ECU and ground the black probe and go drive it. if you see battery voltage come on at any point while driving, guess what? you just hit vtec.

edit: and another thing, why the hell are you people unplugging your o2 sensors in substitution of good engine management? wtf is wrong with you? I ran my car with an emanage at 8 psi for well over a year and was able to pass emissions at any time without sacrificing any performance. and now that im running a hondata, I STILL use an o2. as a matter of fact, i use 3. these cars run great in their 'speed density' format, but they require some very important signals: engine speed, manifold pressure, throttle position and exhaust o2 level. whats the point of investing so much money into your motor when it's gonna run like **** anyways?

/rant

 
Rep Power: 243

yah i have my o2 sensor unplugged and i ggot tuned without it. and vtec kicks in

 
Rep Power: 227

I installed an eManage blue using Dezod's jumper settings, 4-8-E on the rotaries, and used the eManage FAQ v1.8 from mohdparts.com (its all over the place though). Im running v1.49/v1.49 software/firmware.

I had the EXACT same problem after wiring up the VTEC I/O and VTC input wires. All airflow adjust/shiftpoint rotaries were zeroed out, all maps were set to stock in the software. The support tool program recognized the eManage when I went power on. Car started up great, all my indications on the laptop looked great, pulled up the graphs for all parameters and went for a drive.

After a few nervous minutes of hoping my motor wouldnt explode, I decided everything was running safely and started to roll on the throttle. Thats when I noticed a significantly less amount of power from 4k-6k. On the interstate, the damn car would barely make it into 4th gear, almost like it was choking or something...

I thought VTEC was working, because the eManage AUX output signal was indicating HIGH every time I hit the VTEC enable rpm threshold. Either something was seriously wrong with everything else, or VTEC was not engaging, even though the solenoid was getting power.

System oil pressure was ~50+ psi at these times, which I believe is adequate for VTEC engagement; also, coolant temp never dropped below 180F. I even pulled the strainer (it was clean) to see if the passages were clogged.

I wrote Dezod about this, and someone in sales told me that the eManage is not compatible with the VTEC system on our cars (2005 Civic EX AT D17a2).

At this point, I wanted to claw my eyes out. So, I just disconnected the VTEC control input/output and VTC wires, hooked the VTEC solenoid power wire and oil pressure signal wire back up to the stock ECU, and tried it that way.

After doing the 10min idle air control valve relearn sit&wait, VTEC engaged immediately at 4k. It was a night and day difference. I can see why the P&P job on our heads would make such a big difference...these heads must flow like total crap as stock.

If anyone DOES know how to make this thing work with VTEC (and has actually done some testing), please let me know. On that note, if anyone out there can find some concrete evidence of exactly what flavor of VTEC the A2 has, please post. I have heard it is VTEC-E on the D17A6 (leanburn), straight up SOHC VTEC on the D17A2 (from honda's 2005 trim comparison datasheet). I've also heard both the A6 and A2 use VTEC-E. To make it more complicated, ive heard of different kinds of VTEC-E, one with 2 stages, another with 3-stages (low lift single valve, low lift dual valve, high-life&duration dual valve)... If someone can find this out and post a reference it would be fanTastic, cause I dont know what to believe.

.......so anyways...this is what I know:
1) If you try to follow the Greddy wiring diagram, your RPM indication will look like a Formula 1 motor...use the FAQ wiring (use NEP not CKP for rpm).
2) If you hook up VTEC according to the FAQ (with Dezod's jumper settings and 4-8-E rotary), VTEC doesnt work AT ALL, even if the support tool is saying it SHOULD be engaging.
3) Piggyback engine management is frustrating enough when the manuals are correct. But apparently, no one on this planet really knows whats going on inside the eManage, including Greddy If a standalone didnt cost a g-plus, i'd be all about the k-pro, AEM or Motec.
4) If your secondary heated o2 sensor (the narrowband sensor aft of the CAT) is disconnected, I dont think this would cause a serious problem, other than a CEL and inability to clear all I/M statuses...eg should have nothing to do with VTEC engagement.
5) Try hooking the VTEC wiring back up to the ECU and leaving the eManage out of the VTEC circuit. The eManage will flash Mr. Error Code #14 at you all the time, but you will feel VTEC working.
5) The primary heated o2 sensor / "honda air/fuel ratio sensor" (wideband o2 sensor...according to Hondata's website) is pretty important. If rewiring the ECU back to the VTEC circuit w/o the eManage doesnt solve the problem, try reattaching the stock wideband & doing the IACV relearn sit&wait. If everything works, then I guess the WBo2 is part of the VTEC engage prereqs. Blah. I really wish we could just get some simple flowcharts and engineering drawings from honda. It would make life a lot less expensive.

 
Rep Power: 330

only the 03-05's have factory wideband, the 01-02's were narroband primaries. except the HX it has a wideband and 2 narrow band for all model years.