Stock honda Vtec-E, AFR=22

Bindegal · Post by **Bindegal** » Thu Dec 27, 2007 4:26 pm

Armed with my nice new LSU 4.9 wideband, the data is clear.... The OBD1 Vtec-E seems very aggressive in controlling the AFR. Shortly after cold-starting, closed looping @ 14.7 - 15.2 is active. Part throttle acceleration is always done at AFR 14.7 , only when you REALLY put your foot down and do WOT it will go to AFR 12.8 - 13.0 . Although the car is intolerably slow, so you donÂ´t really get anywhere anyway! For all closed loop operations, the corrections seem very precise. Not much sloping up/down, it just sits there, rock stable. Lean cruise, Vtec-E active results in a closed loop @ AFR 22. Yep.... AFR 22.0, approx. lambda 1.5 . I guess now I know why I can usually get 18 km/l or 42 mpg out of it.

I will post logs from cold-starts later, as I feel this could be useful inspiration on how to tune this to be as stock-like as possible. I am curious as to how a modern 2007 car runs. I suspect anything leaner than AFR 14.7 is a big NO-NO because of NOX in the exhaust, though

Damn those treehuggers. We canÂ´t even get decent mileage any more. /Allan

HeathN · Post by **HeathN** » Thu Dec 27, 2007 9:35 pm

Nice work on that find. Keep us updated with your findings.

deluded · Post by **deluded** » Fri Dec 28, 2007 1:25 am

at 22:1 doesn't the egt drop enough to avoid nox formation with very light load? highest combustion temps should be at stoich, right? part throttle accel with fairly high load at stoich, on the other hand, seems like a nox making machine! thanks for the info and looking forward to more.

Post by **Gaskleppie** » Fri Dec 28, 2007 2:08 am

I assume you dont have to try this with a normal B16? Otherwise it will be fun to lower your fuel economy. What will be the highest AF a pepped up B16 will drive with? Some one has tested this if I remember correctly. I thought it was something like 16:1 without problems.

JaredKaragen · Post by **JaredKaragen** » Fri Dec 28, 2007 2:49 am

I think the nox doesn't apply because it only goes that lean after its on a long cruise... dyno smogs are pretty short...

sewell94 · Post by **sewell94** » Fri Dec 28, 2007 3:01 am

I had a buddies mild b16 cruising in the mid 17's on shiny(car made 174hp NA). He drove the car about 2 hrs everyday to miami so gas mileage was important to him, he said he averaged between 37-40 mpg, that was cruising between 80-100mph on a b16 trans in an ek hatch.

Bindegal · Post by **Bindegal** » Fri Dec 28, 2007 4:11 am

As I started the car and drove my lazy ass to buy breakfast, I noticed it takes about 30-45 seconds from cold start (5 degrees c) to closed loop, afr 14.7 . You can tell it still has some cold ect compensation going on though, as the \"dips\" (when you change gear) in AFR are bigger when itÂ´s cold. It finds its way back to 14.7 in a split second, though. Those lean lean readings would be hard to do on something other than a Vtec-E motor though. Supposedly it works by swirling the fuel/air mixture just around the tÃp of the spark plug. In fact when you look at the spark plug, thereÂ´s a slight dark color on only one side of the ceramic.IÂ´m guissing it takes some careful timing of the fuel injection as well... I hopie it will be possible for eCtune to control the timing for the fuel injection at some point. My buddy who does EFI systems can ususally fine tune 5-7hp from fiine tuning that. /Allan

xenocron · Post by **xenocron** » Fri Dec 28, 2007 7:54 am

How much does a 5 gas analyzer cost? I need to buy one...

pacman · Post by **pacman** » Fri Dec 28, 2007 8:17 am

1500gbp for my 5gas analyser, which was bought second hand from my old boss when the testing critera changed for the UK MOT's. I think the price new was around the Â£3.5k.

sewell94 · Post by **sewell94** » Fri Dec 28, 2007 1:58 pm

You can pick old 80's-mid 90's sun 5 gas machines for a few hundred bucks on ebay. Buddy of mine was gonna to give me one, but its so big, i didn't have room for it, so he just threw it away. The one he had had a built-in scope, and could test various engine sensors, which would have been real nice to have. It was about the size of a living room entertainment center.

xenocron · Post by **xenocron** » Fri Dec 28, 2007 4:20 pm

I should call up a bunch of dealerships until I find one that is throwing one out or has one shoved in the corner never getting used

sewell94 · Post by **sewell94** » Fri Dec 28, 2007 5:28 pm

most of them will be happy just to get the thing out of the way. Be forewarned, they are crude old school Dos machines(typically) You'll prolly have to find some guy in his late 40's that will actually be able to show you how to use it. I'm sure a case a beer will do the trick for the machine and training time

Funny thing is those machines were like $10k 20 years ago.

CRX2 · Post by **CRX2** » Sat Dec 29, 2007 9:30 pm

Technically VTEC-E is very interesting. It can handle AF ratio's up to 22... VTEC-E OBD1 uses a LAF sensor instead of a lambdasensor. In fact it's a wideband. LAF = Lineair Air Fuel. The VTEC-E OBD2 uses a sensor on the crankshaft to measure fluctuations in the crank speed. And a normal narrowband lamda. OBD2 also kan work with AF 's upto 22. Once in a while the ECU injects one shot fuel to check if the CRANK and lambda are stil working.. AF shoots a bit lower then. I don't think that the OBD1 version does this too? @Bindegal, did you see the AF lower sometimes when cruising at constant speed? In fact: A D15Z6 VTEC-E (obd2) engine is much more technical as a B16A1... 12 valve/16valve, lean mixture, and 115ps...I drove a Civic for a week with D15Z6 and got a millage of 20km/ltr Pretty cool engine

The coolest engine I have seen so far is the one from the Honda Insight. That engine is full of technical stuff what never was used before...

Bindegal · Post by **Bindegal** » Sun Dec 30, 2007 2:55 pm

AFR is pretty constant on my OBD1. Actually it uses the good olÂ´ L1H1 wideband sensor. But they must be controlling it in a special way, because as I recall the L1H1 normally has an appalingly bad resolution in the lean area. Do you have some links to the OBD2 Vtec-E stuff? I always wondered how they could run it so lean on a narrowband sensor. /Allan

Post by **Gaskleppie** » Mon Dec 31, 2007 2:13 am

Once in a while the ECU injects one shot fuel to check if the CRANK and lambda are still working.. AF shoots a bit lower then. I don't think that the OBD1 version does this too?

This is a brilliant way to drive low AF's with a narrow band. Let it drive closed loop and remember what the injection time is at closed loop to run 14.7. When it is possible to drive lean, disable closed loop and lower this injection time by X%. When the driver is changing the revs a bit, just go back to normal closed loop and do it again. This can even be a possible eCtune feature!