I installed the UltraGauge initially to monitor coolant temp since my truck (I believe) has no tstat. I'm dealing with cooling system maintenance separately so won't go too much into that here.

Background...........I get horrible fuel mileage, even horrible for what I think I should get. I think around 10, maybe 12 MPG highway (taking into account larger tire speedo error), easy on the throttle, not running 90MPH or anything. Until recently when outside temps finally got decent my coolant temp would never go above ~140F on the UG. This truck never runs open loop. The other day I took it for drive and since it's now warm outside, the coolant temp showed as high as 185F and occasionally the UG would indicate open loop. Suffice to say I'm taking care of the cooling system shortly so normal op temps should not be a problem.

Question is this.....I want this truck to run open loop at normal op temps correct? If not running open loop I'm basically using more fuel than necessary which ultimately may cause other issues. Again, am I correct here?

I know I could google most of this at least generically but figured I'm not the only one who could benefit from a discussion on this. I will also be honest and say that I have not searched, I find the search function on these forums to be less than helpful.

Cheers.

 

closed loop at op temp, o2 to be concerned with are upstreams (between engine and cat) ntk brand can be had at a good price on amazon

 

Hmm...guess I knew even less than I thought. Well soon enough i won't have cats, I'm ordering Hedman Hedders as well, plan to install those sooner rather than later. I currently have no fault codes though it had a fault code when I bought it. I checked it, don't recall what it was now but I think I posted it in another thread. I cleared it and it has not returned.

Moving on I guess.

Thanks for your reply.

 

Unless you plan on doing a port/polish, enlarge the intake/exhaust valves, install a decent grind American annealed bumpstick and play with a MS without the benefit of a four wheel dyno your not going to see any benefit with headers. Total waste of a dime and you'll interfere with your steering shaft so have a decent ball peen hammer handy.

These are high compression as far as Rover is concerned but not really in the real world. Your fuel economy boat will be further from the dock, not closer to it. Unfortunately these severely detuned ECU's are programmed to run on a wide variety of fuel refining and don't even notice when an improvement is added, NAS or ROW. You need the cylinder scavenging from the craptastic manifolds, sorry to be the bearer of bad news....... If you can find a set from *any* P38 you'd be better off. Then of course you'll need a custom exhaust......lol.

It's a Disco, leave it alone and fix what's wrong. I get 18 mpg off of 91 octane because I keep the engine internally clean and in decent electrical tune. Want more MPG's? Strip the interior out, it's brittle crap by now anyways......

 

I get about 12mpg. I thought every D1 was.

 

Previous owner said it had been diagnosed with a likely bad cat so I figured better off to just remove them, I won't replace them. The scrap price of the cats will likely pay for the headers and then some so I shouldn't be out any $$$. I'm not really looking for power, I know these things are pigs. I just would like to see some better MPG, more like 15 even. It is reportedly in good electrical tune now with recent plugs/wires. Perhaps I'll change the plugs anyway.

I still have to believe fixing the cooling system issues will help, can't be good to run at such low op temp all the time.

Thanks for more replies, always helpful.

 

Yes, temp is your current problem, the ECU isn't using the few variables it has to learn, fine tune the SFI. I would think your motor is lopping at 10. Each cylinder is getting the same timing, same squirt no matter what the cylinder condition is.

 

Fix the cooling system problem and get your Tstat put back in. You should get to normal operating temp (180-200) within 5 minutes of driving regardless of ambient temps.

On another note, is the whole open/close loop thing on the UG is backwards and has a lot of people confused. By definition, an open loop controller makes adjustments a setpoint variable (like your air/fuel mix) without feedback (as would be the case when you ECU runs its warm up problem and injects a constant amount of fuel). A closed loop system interprets feedback and automatically adjusts the set point (as the case when the ECU reads your temp/O2 data and makes adjustments to the air/fuel mixture).

You want your truck to run in closed loop at normal operating temps but you will never get there if your ECU thinks you're still in warm up mode.

 

I get 12-13 mpg. Going to replace the upstream o2s and plugs and hope for the best. Truck is well cared for, runs right at 185, etc... 33s will do a number on gas mileage though. I'm just glad my DD gets 27-28 mpg

 

Put in a stat, about $10 plus gasket.

On the GEMS engine, here is what the ECU book has to say -

P0125 - Engine Coolant Temperature - Warm up time limit, [closed loop fuel] typically 90 seconds at 20oC start temperature


and

GEMS ECU manual attached, more that most want to know about O2s, codes, etc.