I've always wondered the how much more fuel our motors use when v-tec is engaged. For you people who track race and keep the car in v-tec for prolonged periods of time have you ever figured out your mpg's?

 

ITR's get 11-13 mpg on track.

I dont think i do any better (B18A1 no vtec)

 

40mpg highway/32mpg city/15mpg track and as low as 8mpg autocrossing. my car is sohc vtec.

nate

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by solo-x &raquo;</TD></TR><TR><TD CLASS="quote">40mpg highway/32mpg city/15mpg track and as low as 8mpg autocrossing. my car is sohc vtec.

nate</TD></TR></TABLE>

Lucky. My RX-7 got 15-20mpg on the street and 6-8mpg on track. My truck gets 16mpg with 100% highway driving and 13mpg all suburban driving.

 

I get ~12 mpg when I flog the hell out of my car on track.

 

~9-10mpg on the track. I don't have VTEC either.


"Mah M4d 3rD g34R V4N0s k!Ck3d iN 4Nd i w4S g0N3 sUcK4!"

 

ITR:

track
9-10mpg before vafc
11-12mpg after vafc

street
22-25mpg

highway
29-31mpg

 

30-37 MPG with highway and city. ~15 on track. This is with my SOHC VTEC.

 

2000 Civic Si: 30-35 Hwy, 25-30 in-town, 10-12 on track. Stays in V-tec almost all the time on track.

1988 CRX Si: 35 Hwy, 35 in-town, 15 on track, no V-tec.

1999 Chevy Tahoe: 20 Hwy, 15 in-town, 12-15 towing, no V-tec.

 

i read somewhere that when vtec kicks in, the ratio of gas to air is 1 to 1, while 1 to 16 otherwise. so do the math of how inefficience it gets if vtec is on all the time!
but then, i might be wrong.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by zk11 &raquo;</TD></TR><TR><TD CLASS="quote">i read somewhere that when vtec kicks in, the ratio of gas to air is 1 to 1</TD></TR></TABLE>

Haha... then you'd be spouting out so much black smoke out the tail pipe your folowers windsheild's would be coated

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">, while 1 to 16 otherwise. so do the math of how inefficience it gets if vtec is on all the time! </TD></TR></TABLE>

stoich ratio is 14.7:1, the ecu will try to achieve that in open loop

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">but then, i might be wrong.</TD></TR></TABLE>

yup!

 

good to know the truth

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">stoich ratio is 14.7:1, the ecu will try to achieve that in open loop
</TD></TR></TABLE>

Now it is j00 who is wrong (sort of)! Most cars aim a tad richer than stoich because fuel rarely atomizes perfectly.

 

d'uh........

i was sticking to basics here

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">d'uh........

i was sticking to basics here </TD></TR></TABLE>

And another thing, you have described "closed loop" not open, since we're nitpicking.

 

bah! on all of j00!!!!!!!

I was studying for a genetics exam last night. Makes the brain fuzzy. That and getting about 4 hrs of sleep a night.

I was so tired i was talking to myself and referring to mutant genes as "busted"

"well the lac operon wont function because the lacZ gene is busted"

 

I noticed the peaky R6 engine I'm tuning likes to run pretty damned rich at low rpm's and get closer to stoch higher up. Probably due to valve overlap since there's no VTEC cams or anything. That's the sort of thing VTEC eliminates.

 

do further display my lack of knowledge in ecu tuning, at WOT, doesn't the ecu aim for something around 12.5-12.8 air/fuel ratio? maybe i'm thinking of carb'ed v8's....

nate

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by solo-x &raquo;</TD></TR><TR><TD CLASS="quote">do further display my lack of knowledge in ecu tuning, at WOT, doesn't the ecu aim for something around 12.5-12.8 air/fuel ratio? maybe i'm thinking of carb'ed v8's....

nate</TD></TR></TABLE>

at WOT the ecu relies totally on the fuel map and long term correction map
and disregards the oxygen sensor. carbs are even less intelligent since they
have no real "brain"

 

I dunno exact #'s on my Si, but when I did an HPDE at Lime Rock, I was astounded by how much fuel the car burned!!! You could almost watch the needle drop!

 

My B18C1 burns about 1/4 of a tank in a 30 minute session.

 

Quote, originally posted by solo-x »
do further display my lack of knowledge in ecu tuning, at WOT, doesn't the ecu aim for something around 12.5-12.8 air/fuel ratio? maybe i'm thinking of carb'ed v8's....
nate

YUP your right, when hte ecu is in open circuit mode, relying on precalculated maps for fuel delivery, it bases fuel delivery on what it sees from tps, map, and a few other things, but basically if ur feathering the throttle it gives a bit leaner, but as soon as u jump on the throttle it does the same thing as a carburettor and gives a pretty big jump of fuel, and then keeps it nice and rich!

 

So the consensus is about 10-13 mpg? I quess thats not really bad considering the rpm's and its at wot. I would've thought it would be in single digits. At least in my car v-tec runs pretty rich and I only drag race but I drive 40 mins. there and 40 mins. back and use more fuel at the track then I do driving.

 

in the gsr and si I got about the same - 23 city driving/ 12-14 autox/30 highway

turbo II with monster fuel pump overflowing stock FPR - 12 city/16 highway/6-7 track lol

 

How can you guys track efficiency at an auto-x event? You're not running more than what, 3 miles at a time!