Fuel econ - Carby 4.1 vs MPEFI OHC 4.0

The MaDDeSTMaN · 21-10-2005, 10:51 AM

Ok, as some of you know, I've got my stock standard (for now) carbied 4.1 XF, and LuvinmyEB has a JMM enhanced (just Dev 1) EB GLi. They're both auto, mine being 3 speed, hers being 4 speed.

Last time her car was run on a dyno, it put out 118rwkw according to the dyno at JMM, and that was BEFORE the extractors were bolted on. I personally have my doubts about that dyno figure, but even 110rwkw would be respectable and well within possible if we assumed a roughly 10% dyno error, which I'm sure it wouldn't be out by that far. Given that it pulled that sort of power, there wouldn't seem to be anything wrong with the engine I'd guess - massive blowby, tuning problems etc would lower the dyno figure, right?

Anyway.

I would have thought the EBs EFI 4.0 would get better fuel econ then the carbied 4.1, particularly with decent extractors, a decent exhaust and a pretty much new high flow cat, but with both cars driven in the same manner, the XF gets an easy 100 to 150kms more to the same amount of fuel. Given that there doesn't seem to be anything wrong with the engine, would it simply be because of the shorter diff ratio (3.23:1 vs my 2.77:1), or could it be something else, like a dying/dead oxy sensor? I doubt it's the 4 speed in the EB too, if anything that holds higher gears longer then mine does and is more reluctant to kick down a gear, even with full throttle.

It's odd, I always thought EFI would be more fuel efficient, particularly with a decent exhaust setup, but that doesn't appear to be the case.

21-10-2005, 10:56 AM

Id say oxy sensor, but diff ratio has a lot to do with it. What do both first gears redline at, and at what RPM do they change at WOT?

The MaDDeSTMaN · 21-10-2005, 11:02 AM

Quote:

Originally Posted by ArgonEF

Id say oxy sensor, but diff ratio has a lot to do with it. What do both first gears redline at, and at what RPM do they change at WOT?

Don't know about the EB (no tacho), but the XF redlines at 4500rpm, but usually changes gears just over 4000rpm at wide open throttle.

Most of the driving of both cars is at light throttle, and generally the XF doesn't go above 2000rpm unless it's on a freeway, and considering the EB is driven in the same mannor, I'd guess it would be about the same, although having the overdriven 4th gear, it would sit at lower revs on the freeway I'd guess, unless the combo of the overdriven 4th plus the shorter diff ratio equal out to the same revs as the old 3 speeder with a 2.77:1 diff... But I doubt it.

rag top · 21-10-2005, 12:01 PM

What is the weight difference between the two??

The MaDDeSTMaN · 21-10-2005, 12:41 PM

Quote:

Originally Posted by '67

What is the weight difference between the two??

Not sure, nothing has been done for weight reduction on either car, other then the Dev1 on the EB and the 15" alloy ROH wheels it's totally stock.

The XF is totally stock, asides froma few tiny things wich wouldn't affect the weight. So if anybody knows the weight of a stock XF GL 4.1 carb auto, and the weight of a stock EB GLi auto, we could work it out.

pauljh74 · 21-10-2005, 01:01 PM

I had an XE Falcon 4.1 carby with 4 speed manual, that used about the same juice around town as my current EL XR6. On the highway, the EL is well ahead. The EB would be 100-150kg heavier than your XF I think. I know XE-EL is 200+ kg. Considering my EL is heavier and has more grunt than the XE, similar consumption isn't a bad result.

With EFI vs carby, at max throttle they'll be equally as efficient. At part throttle, EFI wins. But if the EB is coming up that much shorter per tank, I'd say there might be a small problem.

The MaDDeSTMaN · 21-10-2005, 01:20 PM

Quote:

Originally Posted by pauljh74

I had an XE Falcon 4.1 carby with 4 speed manual, that used about the same juice around town as my current EL XR6. On the highway, the EL is well ahead. The EB would be 100-150kg heavier than your XF I think. I know XE-EL is 200+ kg. Considering my EL is heavier and has more grunt than the XE, similar consumption isn't a bad result.

With EFI vs carby, at max throttle they'll be equally as efficient. At part throttle, EFI wins. But if the EB is coming up that much shorter per tank, I'd say there might be a small problem.

Cool, thanks for that.

Yeah, I suspect there must be something not quite right, the EB isn't lacking power, so whatever is causing the lower fuel consumption doesn't seem to be causing any trouble at WOT, only at part throttle, at least that's what makes sense to me. Extra weight + shorter diff explains it to a point, but I don't think it explains the entire 100-150km to a tank difference.

The fuel consumption on the EB has improved quite a bit since the extractors went on, before that it was lucky to get over 400ks to a tank, now it will get 450-500kms, so it's not like it's too bad compared to some threads I've seen here where people have said they're having trouble getting 300kms to a tank, but I'm still shocked that the XF gets so much further on the same amount of fuel.

So would the most likely suspect be oxy sensor?

rag top · 21-10-2005, 01:32 PM

Oxy sensor, injectors, any buildup in the fuel system, fuel and air filters, incorrect trip meter...

pauljh74 · 21-10-2005, 01:42 PM

For around town, 450-500 is good. I would struggle to get 400km out of a tank just around town in typical stop/go traffic. Increasing the percentage of steady throttle highway/freeway driving and it improves markedly. While the EB has a shorter diff, the top gear is similar/taller in terms of km/h per 1000RPM. But the EB's motor has a different powerband. The XF (also my XE) would happily pull from 1200-1500 RPM and cruise at 2000RPM, where it was just starting to move into a big fat torque reserve. I know my XR6 is happier once it passes 2000RPM, this is where it really only starts, but 1500 RPM is where I'd consider it to produce sufficient torque for accelerating in higher gears like 3rd/4th. The XE/XF would run out of puff at 4000RPM, the 4.0MPFI motor would go to 5000RPM before running out of puff - and would redline at around 5500RPM. Yet it still uses similar fuel, despite revving harder and the car weighing more.

DanXR6T · 21-10-2005, 01:47 PM

Unless you know the a/f ratio at the relevant throttle percentage then you can only assume that one is running rich/lean, etc.

You can test the oxy sensor with a multimeter if you want.

So basically you are saying the EB gets 450-500kms and the XF is getting 600kms/tank? 450-500kms in city is very common for an eseries, 600kms in city is basically in the driving to church on sunday grandpa league of fuel econ. Perhaps the XF is running very lean?

The EB under the same throttle percentage will be faster than the XF.

Dan.

Biggoggs · 21-10-2005, 01:58 PM

Taken from http://www.geocities.com/falconfacts/

XF;
4.1L Alloy Head 6 cyl
Power: 103kW at 3750rpm
Torque: 316Nm at 2400rpm
Pushrod overhead valve, 2 valves per cylinder
Compression ratio: 9.35:1
Fuel consumption: AS2877 City/Highway per 100km: 11.5L/8L (Falcon GL 4.1, 5 speed) - No auto stats

EB;
4.0L 6 cyl (Series II)
Power: 148kW at 4500rpm
Torque: 348Nm at 3750rpm
Overhead camshaft, 2 valves per cylinder
Compression ratio: 8.8:1
Fuel consumption: AS2877 City/Highway per 100km: 12.5L/8L (Falcon GL 3.9 m/p auto) - A 4.0 ED w/ 4spd auto gets 13.8L/100km

The MaDDeSTMaN · 21-10-2005, 03:08 PM

Quote:

Originally Posted by Axeman82

Unless you know the a/f ratio at the relevant throttle percentage then you can only assume that one is running rich/lean, etc.

You can test the oxy sensor with a multimeter if you want.

So basically you are saying the EB gets 450-500kms and the XF is getting 600kms/tank? 450-500kms in city is very common for an eseries, 600kms in city is basically in the driving to church on sunday grandpa league of fuel econ. Perhaps the XF is running very lean?

That's a good point, I hadn't thought of that, thanks! Is there any way I could check that, or would that be something best left to someone with an exhaust analyser?

Yes, I do drive like a grandpa on his way to church on sunday, there's no reward for driving the XF hard, and considering the EB isn't my car "you bend, you spend", I also don't drive it hard either - in fact, I probably drive the XF slightly harder then the EB, seeing as it's my car. The XF will get between 550 to 600kms to a tank, occasionally slightly more then that if I really want to push my luck with the petrol gauge flashing one red bar at me. Both of those are mixed city/freeway driving, with most of it being city driving. If anything, the EB spends more time at 100-110km/h then the XF, because it's the car we usually take up to Sunbury to visit family up there, whereas the XF is the daily runabout.

Quote:

Originally Posted by Axeman82

The EB under the same throttle percentage will be faster than the XF.

Dan.

No doubt about that! Even if the EB and the XF had the same engine and transmission, and there was no weight difference, the EB would still be faster under the same throttle percentage thanks to the shorter diff ratio, but then throw in an engine making a lot more power, and even the weight difference isn't going to be anywhere near enough to even it out, not by a long way. Although from very low in the revs, the XF does seem to have more torque, at say 1000rpm, but once both engines hit 2000rpm, it's obvious which engine has the more power, and it's not mine

Quote:

Originally Posted by pauljh74

For around town, 450-500 is good. I would struggle to get 400km out of a tank just around town in typical stop/go traffic. Increasing the percentage of steady throttle highway/freeway driving and it improves markedly. While the EB has a shorter diff, the top gear is similar/taller in terms of km/h per 1000RPM. But the EB's motor has a different powerband. The XF (also my XE) would happily pull from 1200-1500 RPM and cruise at 2000RPM, where it was just starting to move into a big fat torque reserve. I know my XR6 is happier once it passes 2000RPM, this is where it really only starts, but 1500 RPM is where I'd consider it to produce sufficient torque for accelerating in higher gears like 3rd/4th. The XE/XF would run out of puff at 4000RPM, the 4.0MPFI motor would go to 5000RPM before running out of puff - and would redline at around 5500RPM. Yet it still uses similar fuel, despite revving harder and the car weighing more.

I've noticed exactly what you said about the different powerbands. You've seen our house, so you'd know that when we're leaving here, we have to use a bit of throttle to get up to the 70km/h limit going for a gap in traffic during peak hour. In the XF, it's as simple as taking my foot off the brake and applying light throttle pressure, then a little more, and taking advantage of the low down torque. In the EB, I actually need to give it more throttle until the revs pick up a bit, it doesn't seem to have as much torque low down in the revs, but of course, once the revs pick up a bit, it's got more torque then the XF. Also yes, the XF quickly drops off power once it hits about 3750rpm or so, whereas the EB doesn't feel like it loses any power before it shifts gears, and I'd be very suprised if it doesn't hit at least 4000rpm before shifting with WOT.

Quote:

Originally Posted by '67

Oxy sensor, injectors, any buildup in the fuel system, fuel and air filters, incorrect trip meter...

Asides from the oxy sensor, wouldn't those other things affect the power and therefore it would do worse on the dyno? I know the air-filter is filthy, but asides from that, I don't know, Brendan Mock said the injectors were in good condition. If the trip meter is reading incorrectly, wouldn't that mean that the odometer would also be reading incorrectly, as well as the speedo?

The MaDDeSTMaN · 21-10-2005, 03:11 PM

PS how would we check the oxy sensor with a multimeter?

Steffo · 21-10-2005, 05:23 PM

Quote:

Originally Posted by The MaDDeSTMaN

Not sure, nothing has been done for weight reduction on either car, other then the Dev1 on the EB and the 15" alloy ROH wheels it's totally stock.

The XF is totally stock, asides froma few tiny things wich wouldn't affect the weight. So if anybody knows the weight of a stock XF GL 4.1 carb auto, and the weight of a stock EB GLi auto, we could work it out.

XF's were 1333kg. EB's were 1445kg. 112kg difference between the two.

DanXR6T · 21-10-2005, 05:58 PM

Quote:

Originally Posted by The MaDDeSTMaN

PS how would we check the oxy sensor with a multimeter?

http://www.fordforums.com.au/photos/...cat=500&page=1

check that pic out, its under my gallery too.

That is a faithful reproduction of a fine book called the Haynes Ford Falcon/Fairlane manual - greatest wad of toilet paper to be binded into a handy carry with you tear out bundle of anus accessory.

Dan..

The MaDDeSTMaN · 21-10-2005, 06:15 PM

Quote:

Originally Posted by Axeman82

http://www.fordforums.com.au/photos/...cat=500&page=1

check that pic out, its under my gallery too.

That is a faithful reproduction of a fine book called the Haynes Ford Falcon/Fairlane manual - greatest wad of toilet paper to be binded into a handy carry with you tear out bundle of anus accessory.

Dan..

Beautiful, thanks for that!

Anybody got any idea how I could check to see if the XF is actually running too lean?

rag top · 22-10-2005, 07:41 AM

Quote:

Originally Posted by The MaDDeSTMaN

Anybody got any idea how I could check to see if the XF is actually running too lean?

i thought you could tell by the colour of the spark plugs

rag top · 22-10-2005, 07:45 AM

By the way The MaDDeSTMaN, are both cars driven by the same driver in the same traffic conditions to get those results???
I get better economy around town than the wife in our AU by more than 100kms a tank, but that was mainly driving to work with no traffic, and bugger all lights. A benefit of shift work.

rag top · 22-10-2005, 07:51 AM

Quote:

Originally Posted by '67

i thought you could tell by the colour of the spark plugs

Have a look at the following site under "DETONATION"
http://www.gnttype.org/techarea/engine/plugs.html

also read:
http://www.carcraft.com/techarticles/64378/

XHII V8S · 22-10-2005, 09:26 AM

Hmm while we're on the subject of fuel economy, is it normal for me to get 300kms per tank city driving from my XH 5.0L?

The MaDDeSTMaN · 22-10-2005, 10:41 AM

Quote:

Originally Posted by '67

By the way The MaDDeSTMaN, are both cars driven by the same driver in the same traffic conditions to get those results???
I get better economy around town than the wife in our AU by more than 100kms a tank, but that was mainly driving to work with no traffic, and bugger all lights. A benefit of shift work.

Yup, same driver (me), same traffic conditions for the most part, if anything the EB gets the easier run with it being the car of choice for runs up to Sunbury and back to see family, which should see it getting better fuel econ sitting on the freeway doing 100km/h, then 110km/h once we leave suburbia and the speed limit goes up to 110.

The MaDDeSTMaN · 22-10-2005, 10:44 AM

Quote:

Originally Posted by '67

Have a look at the following site under "DETONATION"
http://www.gnttype.org/techarea/engine/plugs.html

also read:
http://www.carcraft.com/techarticles/64378/

Beautiful, I'll pull one out and have a look. I changed them just after getting the car, and the old ones looked like the picture under "Normal", and the only thing I've done since then is replace the spark plugs, give it some fresh oil and new filters, I havn't fiddled with the carby (if it isn't broke, don't fit it), so we'll see.