The optimum ratio for best MPG?
 

Recently, I have developed my own digital chip for my Ford Ranger 2.5 TDCi. The chip can manipulate CRP MAP and MAF for all RPM range. I have got a lot more power and responsiveness from my little engine with a little more smoke only when slamming the paddle strongly. But at cruise speed, I can only see a very very thin cloud, almost nothing.

My question is, how do we know if we have the optimum mix of fuel and air especially at cruise speed say 2000-2500 rpm. Because I don't have any gain in MPG as claimed by all other chips. And I think I have not got the mixture right just yet.

Anyone has any suggestion?


note:

My stock power is 143 bhp at 3500rpm and 330 nm at 1800 rpm. With my chip, I now have211 bhp at 3600rpm and 505 nm at 2000 rpm. Just about maximum output I can get from the stock engine, I guess. I am looking for a little bigger nozzle for the injector but not sure if it is the right way to do.

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Oh...tough question.

I though I would get the answer in a flash. :s:

I wish I could help with your truck but my knowledge on gas engines is limited. Do you have a regular air filter on your truck? I changed the regular paper filter on my truck to a better air flow type and noticed a small increase in milage

I think we have many ways of improving MPG, and I have been trying everything. Yes, I have hi flow filter as well.

As Diesel engines have a very wide A/F ratio, I am not surprised that I could not find any source talking about its optimum. However, I still believe there must be some number from either lab or real life that could be helpful in MPG business.

Still waiting................

I know "optimum" AFR for a gas engine is 14.7, I don't know if it's the same for diesel or not. Sorry I couldn't be of more help.

Thank you, Thank you.

Will continue searching.

if your only tweeking MAP and MAF i can understand the lack of any milage gains basicly your giving the engine the full boost fuel earlier which yeah helps low end power and drivablitly but not milage, you need a way to alter the timing to see the best milage gains

Why would advancing timimg gain MPG?

At cruise speed says 100-120 km/h, the load of the same truck should be the same which may be only 15-20% of engine max power. So, the only way to gain MPG is to have higher efficiency engine at that very light load. To me, if advancing timing can raise the efficiency at this light load, the stock engine engineers should have done it.

Also, at the same load, there would be about the same fuel injected into the cylender. A more efficient engine may need a little less fuel.

Anyway, please let me know more detail.

Actually, most chips on the market now do not even control any MAP or MAF, only CRP. But they still claim the gain in MPG.

My truck has wheel power of about 191 BHP at about 3600 rpm. I thought I had a very good hi end power already :humm:

As Ususal, It Depends...
 

Depends mostly on your driving style / environment. City driving likes more gear, highway driving needs less gear.

you have to add timing because diesel fuel burns at a steady rate...so when you add more fuel to the mix you are actually retarding your timing because more fuel means a longer burn...because of this you need to add timing to make up for the longer burn....timing is the most critical parameter that can be changed on a diesel engine...i know of a p-pumped 24v cummins that was heavily modified that with a timing change of only 4* made a 250hp difference at 2600rpm with nothing else being changed.....so basicly more fuel = the need for more timing also smoke can be reduced with proper timing

i know some rangers run 4.10 gears from factory, friend of mine has a 03 with 4.10s an it would screen 2200-2400 down the highway with 245's so i gave her a set of 33/12.5/15 M/T's an her ranger runs way better, 1700-1900 down the hwy...better mpg too