MS and lousy gas mileage!

[malloy1]

I got my MS finished up a couple of weeks ago, and been checking out the gas mileage, and after a couple of tank fill-ups, the gas mileage came out about 21 miles per gallon (and that's highway mileage (65-75mph)!-I drive 60 miles a day on a fairly flat, good flowing highway). I was hoping for more like 25-30 miles/gal. The car has plenty of power, but the gas mileage is awful.

The setup is:
-'65 122 with a B21F/M41 (stocked, not modified normally aspirated engine)
-LC-1 WBO2
-MS V2.2 running MSnS-extra (24s13) fuel only - tuning with MT2.25b514 and VEXME
-original '79 Bosch iginition setup from a 240
-Bosch 21lbs EFI injectors
-Volvo 850 Bosch TPS
-EGO crossover is set to 2.5v
-AFR is set to 14.7
-K&N air filter

I've checked the error on the odometer at around 3% fast, and the speedometer is around 5% slow. Which I find acceptable for a 40+ year old car.

Should I try and lean out the fuel mixture from 14.7 to 16.5? Do I just change the EGO crossover point to 2.6-2.7v?? Would I need to run it back through VEXME, or do I need to adjust only the VE tables used during normal high speed cruise?

I figured that a 122 weight (122 weight 2400 lbs vs 240 weight 3000 lbs), running EFI, and a WBO2 sensor would produce better fuel economy than the original K-jet setup (B21F with a M46 gets about 25-28 mpg?)

Paul

[Hank Scorpio]

Thats surprizing. Whats your cruise RPM?

I got 25-26mpg running 13.8-14.2AFR's in the 242. Shocked the hell out of me but I checked it a few different times.

You could try adding a bit of timing under cruise conditions, might make the motor run a bit more effiecently.

[volvorod85]

You may want to go over your timing maps. You want more timing in the cruise stage. I get crappy mileage (well ive got a heavy foot and a turbo) but either way, i added 4 degrees of timing from 1500-4000 RPM and from the box under 100KPA to the bottom. Helped a lot with the low end torque and milage on cruise. Ya figure the vacuum advance is at max advance at cruise anyway.....and the vacuum advance is for economy. I would leave the AFR's alone....you dont want to go lean like that, youll end up burning a valve. Really look at your timing map, you want that to be around 15 or more inches of vacuum at cruise (more meaning up towards 20)
Mark

I get 21MPG with A/C on a 90' 765, and 13-14 around town (again ive got a lead foor and now a locker, hehe, im waitin till i pull a kenny and turn my subframe into a twizzler) on the FWY with a turbo, a B230FT and a 5thgear thats way too tall...so im luggin it more than i should be...and ive got a narrow bandsensor doing my feedback, tuned on a wide band, but havent put it back in.

[JohnMc]

Does the wideband show deviations from 14.7? If it stays nicely stationed at 14.7 all the time I'd suspect something is up with it. When cold, before they light off they sent out a steady default 14.7 signal.

[kyle242gt]

16:1 AFR for cruise (75Kpa), 14.7 at 85Kpa, 14.0 at 90Kpa, 13.5 at 100Kpa. Run closed loop AFR with those targets. +/- 5% authority... if you're getting to the end of the adjustment range, use VexME to get the fuel table right. It works excellently.

Timing is your friend. I suggest immediate deployment of spark capabilities. Advance it until it starts to surge and buck at cruise, then back it off. I ran about 58 with a K cam, about 53 with the T.

[linuxman51]

yeah advance the hell out of the timing and lean it out to mid-upper 15's

[The Aspirator]

I've been MS'ed for almost two years now and I'm still trying to get better than 20mpg during normal driving. On all highway I've been getting 25/26, but that's just long distance crusing at 70mph. In town during normal daily driving I've been getting 17-19 consistently.

Advance the timing, and you can probably run way leaner than 14.7 on an N/A engine. I cruise at 15-16.5, and with your engine you don't need richer than 14.7 until you're starting to accelerate quite nicely.... so say 85kpa? I can't remember, been a long while since I've tuned an N/A car. But yeah, crusing constant load can probably be 16-16.5, light decel but with your foot still on the gas can be 17.0. Light accell can be in the 15's, floored should be in the 13's. Enable the decel fuel cut, works like a charm for me. Have it cut all fuel after 1 second when TPS is at 0%. That'll save you some too.

As you can tell I like to tune "by feel" rather than using Vexme all the time, but that's just me.

John

[swedefiend]

Yeah, I found mileage increased with advance. But, I only run 89 octane as a rule (unless I am Honduh huntin') so I am limited in the amount of advance I can run...

Ben and I took the 245 to the Nantahala recently with two kayaks on the roof and the car slap loaded with other crap and we got about 22 MPG on the way back (and my engine has 65% or more leakdown :) )

[Hank Scorpio]

let us not mention our around town milage... :lol:

btw the T5R only ever got at BEST 20mpg round town, most of the time is was 12-16 ;-)

[kyle242gt]

re: in town mileage-
That's been my Holy Grrrail and excuse to my wife for all the MSnS tomfoolery. I was disappointed to get 15-17 regularly with the K and a light foot on what I thought was an excellent tune. Swapping in a T and a lead foot and an even better tune fetched me 18+ mpg. That's mixed city/hwy, lots of stop and go (and GO!).

And while I too want to get 20 in mixed use, I have to be honest with myself. Our old 744Ti (stock) got 17-18 regularly. Our 855T5 gets about 19 (per trip computer). How much better do I really think I can do?

I've changed my tune a little bit, I think: MSnS is not the be all end all for economy. It's an easy, entertaining, educational, and enlightening way to run more boost than LH will allow. And it's a good choice for NA Kjetters looking to go boosted.

[swedefiend]

BTW, someone wanna loan me 500 bones till I get my student loan money???

I gotta get this heap out of the car before she blows :rofl:

We're gonna throw it on the dyno after I get the other engine built and find the real upper limit of timing for a b21. If she croaks, the oh well - If she makes it, I think we will retire her to a foster home in a 760T that needs a little umph :)

[Hank Scorpio]

re: in town mileage-
That's been my Holy Grrrail and excuse to my wife for all the MSnS tomfoolery. I was disappointed to get 15-17 regularly with the K and a light foot on what I thought was an excellent tune. Swapping in a T and a lead foot and an even better tune fetched me 18+ mpg. That's mixed city/hwy, lots of stop and go (and GO!).

And while I too want to get 20 in mixed use, I have to be honest with myself. Our old 744Ti (stock) got 17-18 regularly. Our 855T5 gets about 19 (per trip computer). How much better do I really think I can do?

I've changed my tune a little bit, I think: MSnS is not the be all end all for economy. It's an easy, entertaining, educational, and enlightening way to run more boost than LH will allow. And it's a good choice for NA Kjetters looking to go boosted.

True, but isn't there a point where no matter how much you tune it, its only going to get so good for milage? Seems to me the only way to improve it any more would be a lighter/more aerodynamic car. Let us not forget what we are driving :rofl: so seems to me MS, haltech, LH they are all going to be about the same when tuned to their fullest potential (milage wise atleast).

[kyle242gt]

...seems to me MS, haltech, LH they are all going to be about the same when tuned to their fullest potential (milage wise atleast).

I'd agree with a caveat: Sequential (yea though I may preach against it) probably could net small improvements, and I wouldn't be surprised if a MAF-based setup could do better than MAP. Just a WAG.

[PetesDustyVolvo]

Wow, I'm a bit surprised how "rich" you all are running.

My car cruises on the highway at 17.5 AFR :omg: Sometimes the wideband even reads 18+ and I basically just gave up on tuning with vexme.... I do have tons of fuel where the power is... and it IS there just ask Neil Peart =p

I'm thinking I have some oxygen leaks

But I'm with the majority here: add more timing before you fiddle with the fuel too much. Perhaps you should look into the IAT retard because my car actually runs BETTER with less timing when its hot.

Other things to look at:
suspension/steering/alignment
does your car have a "belly pan?" under the radiator?

[kyle242gt]

My car cruises on the highway at 17.5 AFR :omg:
Perhaps you should look into the IAT retard because my car actually runs BETTER with less timing when its hot.
:omg:x2 somthing's not right... nobody in their right mind can run that lean. Even the lean burn Hondas, direct injection VWs, etc, are arount 16-16.5 IIRC.
re: the timing, that may be because you're on the ragged edge of being too lean. Lean=hot=prone to misfires. Retarded timing=cooler=less likely to misfire.

I stopped using the IAT retard when I installed the NPR.

[The Aspirator]

Different cars will have a different limit to how lean/advanced you can go during cruise, it'll start to buck when you go too far.

[malloy1]

16:1 AFR for cruise (75Kpa), 14.7 at 85Kpa, 14.0 at 90Kpa, 13.5 at 100Kpa. Run closed loop AFR with those targets. +/- 5% authority... if you're getting to the end of the adjustment range, use VexME to get the fuel table right. It works excellently.

Timing is your friend. I suggest immediate deployment of spark capabilities. Advance it until it starts to surge and buck at cruise, then back it off. I ran about 58 with a K cam, about 53 with the T.


Kyle-

You’re saying I need to figure out MAP for cruise (16:1)/acceleration (14.7:1)/Wide open throttle (13.5:1), change the ARF target table in VEXME to match what you suggested, and then do a couple of datalogging runs.

The authority is set +/- 20% right now, so I give the +/-5% a shot. It's running in close loop except when WOT or at idle.

I’m only running MSnS-e with fuel only, the timing is set to factory settings of 15 degrees BTDC.

Paul

BTW- Decel fuel cut is enabled.

[The Aspirator]

Time for teh spark!