ways to give car better fuel economy!!!

[MagicRat]

Originally Posted by Blue Bowtie

All good information.

Not to beat a dead horse, but to clarify, many early OBD systems used programming and sensors which controlled ignition advance and monitored for detonation. When these systems detected detonation they would retard timing in large steps instead of a couple degrees at a time. Further, they would only slowly attempt to bring the timing back up before detecting detonation and "learning" a reasonable timing advance. However, unlike fuel system trims, this "learned" data was not retained in NV memory, and would repeat at every engine start.

As stated above, in these case, retarding the base timing setting might actually help the mileage by avoiding these large "step" retards by the ECM. As stated further, this method is only a "band aid" for masking a more involved problem(s).

It is possible to reprogram the earlier GM ECMs to reduce the retard steps to less than 1 degree at a time and gain real control, but unfortunately there is a finite number of retard steps available and all timing retard has to be accomplished in that number of steps to prevent serious engine damage if detonation occurs. I've done quite a few older ECM reprograms and PROM burns on pre-OBDII systems and have toyed with the advance tables and retard steps. EVERY engine is different and every program is custom and highly influenced by the modifications.

Both ideas may be valid, but repairing the root cause is the better solution. The often hated EGR system actually has some performance and mileage benefits. The misunderstood EVAP system can improve mileage measurably. Even the EFE systems which always seem to get in the way have benefits.
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Good explanation.
Instead of retarding the ignition for a quick fix, simply try a tankful of premium fuel, and compare the fuel mileage to regular fuel.

My '97 Caddy (with 10:1 compression) will rattle a bit on regular..... not enough to be noticable unless you are listening for it, but fuel mileage is 15-18% worse than premium fuel, just due to the detonation / ECM retarding relationship.

Now, since premium costs only 10% more (around here) I am saving money by spending more for premium.

[consultIII]

[quote=j cAT;6115684][quote=consultIII;6115468]I know, all dealers techs are stupid.

Dealerships are not stupid they full well know how to do this repair work properly...they also have all the info kept in a lock box..this is so other repair shops are at a disadvantage....that is until these internets began...this also is how GM began its tremendous fall ...free info and forums like this !

face it dealerships are not operating on goodwill...scaming customers whenever they can is to help them get some easy cash...short cuts all help the tech as well as the profit line ....If you want to be employee of the month you must play the game their way or the hywy..



my state has small auto repair shops asking the legislature to pass a bill to force GM and the other manufactures to open up that lock box so that all this secret repair info is available to all so as to level the repair playing field...I hope this passes...then the dealerships will not be able to scam ..

I will agree timing to far retarded will cause engine overheat, long crank, less performance but would occur at 4 degrees or greater from manufacturer recommended setting.

In my case this was done after every system was checked and verified to be operating properly (vehicle wasn't egr equipped). ECM reprogram to address this was not available. So we have a complaining customer an no fix. Informed the customer of what we wanted to try and if he wasn't happy with the results we would advance back to factory. How is this cheating a customer?
All warranty work; which paid 0 diagnosis because no dtc was set. Nissan will only pay for the repair 0.3hrs. How long do you think it takes to just verify this concern; a losing situation. How many times in your independant shop do you get paid 0 for diag? 0? How many independants when faced with the same senario would just ship it out to the dealer?

hasn't the right to repair act passed down there?

[j cAT]

[quote=consultIII;6115763][quote=j cAT;6115684]

Originally Posted by consultIII

I know, all dealers techs are stupid.





I will agree timing to far retarded will cause engine overheat, long crank, less performance but would occur at 4 degrees or greater from manufacturer recommended setting.

In my case this was done after every system was checked and verified to be operating properly (vehicle wasn't egr equipped). ECM reprogram to address this was not available. So we have a complaining customer an no fix. Informed the customer of what we wanted to try and if he wasn't happy with the results we would advance back to factory. How is this cheating a customer?
All warranty work; which paid 0 diagnosis because no dtc was set. Nissan will only pay for the repair 0.3hrs. How long do you think it takes to just verify this concern; a losing situation. How many times in your independant shop do you get paid 0 for diag? 0? How many independants when faced with the same senario would just ship it out to the dealer?

hasn't the right to repair act passed down there?

I know that the Nissan maxima had bad cat converters...2005 maxima ..after the replacement the engine ran much better..vehicle had no codes !

[oldblu65]

One thing not mentioned is excessive weight in the car ! Make sure you only carry things that are really necessary ! Carrying multitudes of unnecessary items in the trunk or in the cabin of the vehicle can add weight that will hurt your MPG. For example , your golf clubs or bowling ball in the trunk if they aren't needed on a specific day . This may seem like a trivial matter but it all adds up !

[consultIII]

just contacted my old master tech; there was more to the story than I was aware...was some detonation and poor grade fuel issues in addition; which contributed to the poor economy. The slight retard adjustment correctd the detonation which brought back the fuel economy. my bad. Next time I "tech watch" I better pay attention.

[j cAT]

Originally Posted by consultIII

just contacted my old master tech; there was more to the story than I was aware...was some detonation and poor grade fuel issues in addition; which contributed to the poor economy. The slight retard adjustment correctd the detonation which brought back the fuel economy. my bad. Next time I "tech watch" I better pay attention.

thanks for the explaination but , as you can see there was detonation causing the MPG/PERFORANCE issue....

the computer is a great tool to extract data on engine control operation ...however the end results is very much dependent on the tech's ability to understand what is given...