Getting atrocious mileage?

[1turbofocus]

Update:

 

Replaced the o2 and here is the latest data.

 

City low RPM cruising 12.7 miles .493 gallons. ~25mpg

All highway ~70mph average in 6spd 30 miles 1.481 gallons ~ 21mpg

 

Average ~21mpg

 

I think I'm in the right ballpark now?

 

Your in the right direction yes , Fuel psi is to high , Unhook the Vac to your regulator and see what the psi is engine running at idle ( proper way to check psi ) adjust psi to 39-41psi by lowering your fuel psi you could throw off your WOT A/F so watch that , your target WOT A/F is 12.8 and anything over 13.2 after 3500 LET OFF your lean

 

Now we need to see what your stft1 is reading , this reading is your short turm fuel trim ( Info from your new o2 to the PCM to control fueling ) and if it is way off you could loose 1-3 MPG with very steady throttle at idle or cruise ideally you want it to read between .97 to 1.03 always switching up and down and up and down , when logging it should resemble a castle top around the castle wall if that makes sense

 

When you log I will be glad to remote in and look at the log why its running , I use http://www.teamviewer.com if you would like the help

 

Tom

[Vovchandr]

Your in the right direction yes , Fuel psi is to high , Unhook the Vac to your regulator and see what the psi is engine running at idle ( proper way to check psi ) adjust psi to 39-41psi by lowering your fuel psi you could throw off your WOT A/F so watch that , your target WOT A/F is 12.8 and anything over 13.2 after 3500 LET OFF your lean

 

Now we need to see what your stft1 is reading , this reading is your short turm fuel trim ( Info from your new o2 to the PCM to control fueling ) and if it is way off you could loose 1-3 MPG with very steady throttle at idle or cruise ideally you want it to read between .97 to 1.03 always switching up and down and up and down , when logging it should resemble a castle top around the castle wall if that makes sense

 

When you log I will be glad to remote in and look at the log why its running , I use www.teamviewer.com if you would like the help

 

Tom

 

Tom, my TWM FPR is part of the fuel rail and doesn't have a vacuum line hook up? I can adjust down to ~40psi and from what I've seen so far my fuel pressure doesn't fluctuate at all. I have never diverged into fuel system in vehicles, but to make sure i understand correctly, typically fuel pumps put out constant pressure and systems like FPR adjust the pressure with vacuum or other means? ECU never controls pressure at fuel pump with different voltages for closed/open loop conditions? IE running rich or lean wouldn't be a function of ECU commands? Car is getting better mileage but feels more sluggish on the top end on the butt dyno, but we all know that measures pretty inconsistently.

 

http://www.usa7s.net/vb/attachment.php?attachmentid=15565&stc=1

 

 

I'm still struggling to get my profile loaded to get Pectel to communicate with Descpro software properly and will keep addressing that.

 

 

I'll be looking at my A/F at idle as I adjust it? I use my downstream plug past the cat I should expect to read ~.2 to ~.5 richer or leaner?

[Vovchandr]

I've got this issue too, I did some Googling about those TWM throttles (what I've got on my Zetec), and found Honda guys complaining about the same issue. One guy fabbed up a secondary return spring to get them to snap all the way closed. Have been planning to look into doing that myself, after fixing other things...

 

I'm going to be taking a better look at this myself. I did a through lubing of the cable yesterday and will see if that helped.

 

Otherwise this is what I gathered on the matter

 

As the shaft that the spring loaded butterfly valves are attached to rotates in the brass or bronze bushing in the throttle body housing, it tends to wear one side of the bushing out.

[Slonie]

I'm going to be taking a better look at this myself.

 

I'm looking forward to your findings, for when I get around to it. It's a few rungs down on the hierarchy of needs for my car right now, but one of the truly annoying things with it when it was up and running...

[1turbofocus]

Tom, my TWM FPR is part of the fuel rail and doesn't have a vacuum line hook up? I can adjust down to ~40psi and from what I've seen so far my fuel pressure doesn't fluctuate at all. I have never diverged into fuel system in vehicles, but to make sure i understand correctly, typically fuel pumps put out constant pressure and systems like FPR adjust the pressure with vacuum or other means? ECU never controls pressure at fuel pump with different voltages for closed/open loop conditions? IE running rich or lean wouldn't be a function of ECU commands? Car is getting better mileage but feels more sluggish on the top end on the butt dyno, but we all know that measures pretty inconsistently.

 

 

 

 

I'm still struggling to get my profile loaded to get Pectel to communicate with Descpro software properly and will keep addressing that.

 

 

I'll be looking at my A/F at idle as I adjust it? I use my downstream plug past the cat I should expect to read ~.2 to ~.5 richer or leaner?

No way to answer this , depends on to many things , I would use the front o2 hole and see what it reads vs behind the CAT

 

" typically fuel pumps put out constant pressure and systems like FPR adjust the pressure with vacuum or other means? " With your System yes your correct return fuel system , In the Focus the ECU/PCM controls the Fuel psi which is a non return fuel system

 

" ECU never controls pressure at fuel pump with different voltages for closed/open loop conditions? " in a non return fuel system ( most EFI cars ) the ECU totally controls the fuel pump psi , with a return system most have a Vac port and depending on Vac raises or lowers the fuel psi.

 

" IE running rich or lean wouldn't be a function of ECU commands? " Incorrect

Closed loop ( idle and part throttle ) fuel control works off the front o2 and tells the ECU what your A/F is to rich or to lean the ECU adjust the fueling through the short turm fuel trim , The stft will tell you if you need to add or remove fuel to hit the targeted closed loop fuel

 

Open Loop Fueling ( Wide Open Throttle ) is set tables in your tuning software and depending on your WOT A/F you adjust these to hit a set A/F , I use 12.8 A/F

 

Tom

[Vovchandr]

Quick update.

 

Tried to adjust this two days ago before a track day yesterday. As soon as I tried to rotate the allen key on the FPR with the car at idle, the twisting force let the gas squirt out around the mount of the FPR (it's bolted straight to fuel rail as shown above).

 

Tried it again and same thing happened.

 

At the same time my wideband computer box stopped working (battery corroded off the 9v terminal).

 

with no way to measure and a track day the next day (yesterday) and still trying to get ready for NJMP I left this alone right now and won't touch it through the week.

 

 

 

Got some other issues to troubleshoot right now to get the car ready for next week.

 

If the FPR leaks during operation that could also be a relevant issue to the bad MPG.

[Vovchandr]

New pigtails ordered to fix the wide band.

 

Will mess with this further after NJ

 

http://www.usa7s.net/vb/attachment.php?attachmentid=15590&stc=1

[Vovchandr]

As some of you know the car had an transmission/clutch fail at NJMP. It's still down waiting for me to do an engine out troubleshooting of what exactly happened.

 

This obviously puts any MPG troubleshooting on hold for at least another month.

 

 

On this subject, should I do both engine and transmission at once or separate at the bell housing and just pull the engine out? I'm coming out of the top.

[Croc]

Do both at once is the accepted wisdom.

[JohnCh]

Just remember to drain the transmission first or you will have an oil slick under the car once the driveshaft separates.

 

-John

[wemtd]

vov

if you can I've always taken mine out from below (except for an oil slick the first time). i found no amount of wrapping or plugging adequately seals the tail shaft end. The birkin has a removable frame brace beneath the gear box which allows it to be dropped straight down. I'm not sure if your frame allows this or not.

Good luck and have fun getting intimate with your cat.

[lotsats]

This is a couple of months old, but I thought I would add my two cents anyway. The fuel gauge on my Caterham is very inaccurate so I would not assume that because the gauge moved to the halfway point, you actually used half a tank of gas. It is also very difficult to fill the tank, and I believe this is a common problem. The 90° elbow on the filler neck just doesn’t seem to let gas and air pass in opposite directions readily. My car often regurgitates gas while filling it and I question whether I actually get it full. What is “full” at one stop may not be ”full” the next time. For some reason, I have found an individual pump at one station which seems to work most of the time. I finally eliminated the elbow leaving the original gas cap in place for appearance and added a straight filler tube inside the boot with its own cap. If you really want to check the fuel mileage, and don’t have a working odometer in the car, you may be able to record the distance on a GPS. I suggest driving a considerable distance, maybe a couple hundred miles. Try to get the tank absolutely full before doing this, record any fuel added during this period, and then make sure you get it absolutely full at the end. This will give you a lot better idea of what your fuel mileage actually is.

[Vovchandr]

This is a couple of months old, but I thought I would add my two cents anyway. The fuel gauge on my Caterham is very inaccurate so I would not assume that because the gauge moved to the halfway point, you actually used half a tank of gas. It is also very difficult to fill the tank, and I believe this is a common problem. The 90° elbow on the filler neck just doesn’t seem to let gas and air pass in opposite directions readily. My car often regurgitates gas while filling it and I question whether I actually get it full. What is “full” at one stop may not be ”full” the next time. For some reason, I have found an individual pump at one station which seems to work most of the time. I finally eliminated the elbow leaving the original gas cap in place for appearance and added a straight filler tube inside the boot with its own cap. If you really want to check the fuel mileage, and don’t have a working odometer in the car, you may be able to record the distance on a GPS. I suggest driving a considerable distance, maybe a couple hundred miles. Try to get the tank absolutely full before doing this, record any fuel added during this period, and then make sure you get it absolutely full at the end. This will give you a lot better idea of what your fuel mileage actually is.

 

I appreciate the concerns, but for posterity's sake.

 

Mileage was logged using GPS as well as tripometer for the times when it worked. I tried to use the same gas pumps before and after for consistency. I've started doing much longer distances as well as you read through the thread. I tried my best to eliminate most variables and assumptions.

 

However when I would drive ~60 miles from full on highway and then be approaching E already I knew there is something going on beyond just gauge reading inaccurate.

 

In the end I got it into the teens/low 20's at best.

 

Still pending:

Compression test

FPR adjustment possibly while logging AF

Getting PECTEL to communicate with software properly

Making sure there is nothing seeping past the ITB butterfly's

 

Results won't be around for at least another month.

[wemtd]

With respect to gas pumps: my Birkin was always very finicky filling up. I had to hold the nozzle at an angle, turned sideways, inserted as far in as possible, and just let a trickle of gas flow. Otherwise gas would splash back onto the nozzle and shut off flow. TBox56 filled me in on the solution: the stock gas tank had a small lip inside the filler at the top of the tank (round hole cut in tank, round pipe welded an an angle = oval mating surface. Trimming this internal lip solved the problem. Check to see if your tank has a similar situation.

[Vovchandr]

Current update:

 

Cluster is fixed and speedometer is dialed in.

 

Have been averaging ~20mpg or so this year after the engine out job last year and fixing a bunch of misc issues car had.

 

Between short gearing (6spd 3.62) with highway and not so easy driving it occasionally I'd say I'm a lot closer to the healthy ballpark than before.

 

 

I still think I'm running rich and have a few small issues but makes me feel a lot better overall.