Humor me here guys and try to follow my thinking here......

I have two Mini's....'04 R53 with 15% pulley. Also have a '06 factory JCW with no mods to engine at all, yet....I plan on a 17% pulley this spring.

Here's my thinking. The JCW gets lousy mileage, and yea, I know ....just go with me here for a minute. The '04 Mini gets great mileage and will run circles around the JCW car. The JCW has no codes, no pending codes, so it's running like it should. I was thinking of changing out the blue 380cc injectors to stock "S" injectors to see if my mileage will increase and burn a little cleaner. I'm not racing or tracking the car, and I'm sure that the ECU should be able to control the pulse width for the smaller injectors to keep the check engine light off. I might even gain a little more power if my train of thought is on track......or is my train going to get "derailed" if I try the other injectors

I want some input on this from those who would know

Thanks, Bryan

 

The JCW car has a tune that's designed for the 380cc JCW injectors. If you put the stock S injectors in there, and don't change the tune....there is a good chance it's going to run lean at WOT and you will burn something up. The ECU in these cars run "Closed Loop" (reading the narrow band O2 sensor) only at mid/cruising throttle. At idle, and wide open throttle...the ECU is operating in "open loop"....using preset data tables....NOT going off of the o2 sensor.

In other words.....it's going to run lean at idle and wide open throttle. If it was me, I would find someone to tune your JCW car. That's going to be much cheaper than a new motor after you burn it up.

 

OK...thanks for the clarification about not running in closed loop at idle....I can understand about open loop at WOT, most all cars run this way....I don't understand the thinking of open loop at idle....oh well, I didn't design the system....

I have already put a motor in this car a few years ago,...I really don't want to spend the money again.

I may look into a tune...but would the cost of the tune offset the fuel mileage savings? Probably not

My idea sounded good on paper...but in the real world, I will leave it alone and just go with my other idea of the 17% pulley

Thanks for your input

Bryan

 

If it's tuned right....it really shouldn't be sucking down all kinds of fuel and getting bad MPG. My 03' JCW with 380cc injectors is getting 28-31mpg on the highway at 70mph.

 

We get similar MPG as above with our 03' JCW I have yet to see if there is any difference between it and the 05' JCW we just acquired. I don't expect too much difference but do expect a bit less due to gear ratio change for the 05' 6 speeds.

 

If you're not tracking the car, why consider installing a 17% pulley but concerned about gas mileage? Do you think the 17% pulley will save gas?

 

How do the fuel trims look for the JCW car?

 

To be honest, it's been a while since I looked at the fuel trims....if I remember, they were pretty normal, although a little bit on the high side, probably due to being in open loop at idle per the above posts. Maybe after I get the 17%V pulley on, it may drop the fuel trim back down due to pushing a bit more air into the engine at idle....maybe

Thanks for asking that question, I guess I need to get my scanners out and connect to the car and see what it's reading. Might not be until spring....car is put away for the winter and we got snow the other day

Bryan

 

As long as they are within the -10 / 10% range than you should generally be ok.

 

Those values are a little on the extreme for me...at least from all the cars that I have worked on over the years and now retired from the trade. Ideal trims would be +3 to -3.....but that may not be possible with open loop at idle....I'm thinking maybe +7 to -7 would be max for me....if I could see them at +/-5...I would be happy with those trim numbers.

I should probably look at my scanner data more closely and see what everything is doing......I had a T-Map sensor issue last year that drove me nuts trying to track it down....I just wanted the car to run decent after a year of putting everything back together and wanted to at least drive it before summer was over. For all I know, my pre-O2 sensor may be lazy...but I would think it would throw a code for that if it was bad

Bryan

 

I agree with the ranges, I also adhere to the -+3 & -+7. But generally speaking that is the "safe" range.

I also had a strange t-map sensor problem, switching to a new one didnt actually solve my issue. Until I read a tip on NAM, to check the plug and push in the electrical connectors a bit tighter together, which solved the issue!

 

almost forgot, you can get another ecu with a proper tune and immobilizer bypass, I sell them. just keep your stock ecu and drop it back in for emissions testing.

wideband will tell you if you can get by with 380 +better tune

these ecu's ignore the narrow band above about 30 % load and go straight to the fuel/air tables, they simply dont adapt to mods byond what the long term trim adds

 

I have an Ultragauge on my '06 R52 JCW car....everything is stock on the engine except for the 17% pulley on the supercharger....my engine runs closed loop at idle once warmed up....most of the times the Mini's run fat and rich to help keep from damaging the engine

Bryan