M30 tune-up update

[zmuff]

I installed a set of 19lb injectors last fall to try and help out my aging 535im a little. Other than smoothing out the engine some, I didn't really notice a difference. OBC average MPG stayed around 16.4. New plugs, wires, cap and rotor, fuel filter, valve adjust, and switch to Mobil1 0W40 in March smoothed things out a little more, OBC average MPG went up to around 16.8. Installed a 3.5 bar fuel pressure regulator several weeks ago and now the OBC average MPG is 19.5, I'm on the 5th tank of gas now so that's a pretty good average. Highway MPG was 23.5 before so I can't wait to do another road trip now and see what it is. The bottom line: the 19lb injectors and 3.5 bar FPR are a very good combination. Thanks Mike Holbrook for the FPR recommendation...it was right on target. :D :D :D

http://images.cardomain.com/member_images/4/web/556000-556999/556352_9_full.jpg

http://images.cardomain.com/member_images/4/web/556000-556999/556352_2_full.jpg

[Derek A.]

I am thinking about doing the same. Any installation tips or hurdles to watch out for ?

Thanks

[zmuff]

The fuel pressure regulator is an easy direct replacement. I used the one from a Porsche 944S P/N 0 280 160 263, seems like it was $49.00 plus shipping. The fuel injectors are a bigger project but not hard, I did mine in about two hours. Use this link to Don Gale's site for play by play action...it's very accurate. http://http://www.nmia.com/~dgnrg/page_17.htm The only trouble I really had was when I was started the car for the first time, it ran like one plug wire was off. I spent alot of time troubleshooting trying to find the miss. I ended up taking it for a drive and it smoothed out perfectly in about five minutes. I am assuming the computer had to readjust itself. For tools, a scribe is handy to help pull and hold the fuel injector clips, a flashlight and mirror to find the one that you dropped anyway, and a magnet to retrieve it from the black hole that it fell into...hehe. Good luck.

[zmuff]

Sorry about the link...here it is http://www.nmia.com/~dgnrg/page_17.htm Mike

[mholbrook]

Glad you had good luck with the FPR change. I noticed the same fuel mileage change basically. I just drove to LA and back last weekend and averaged 25 mpg highway. I'm just a nick under 20mpg average for my all around driving (not including and autocross time). I just finished up doing a valve adjustment, changing plugs, wires, distro cap and rotor. Hope to find a little improvement here since the stuff coming out was in some cases pretty used up.

I painted my valve cover aluminum with clear coat and polished the raised portions as well. I'm very happy with the way it looks.....hope it runs as strong!

[Jeff N.]

Your mileage hasn't really gone up.

When you raised the fuel pressure, you increased the amount of fuel per injector pulse. In response to this, the lamda function of the DME shortened the pulse to keep the a/f ratio within the target spec. You are basically putting in the same amount of fuel to the engine but just using a shorter injector pulse to do it.

The fuel mileage is calculated by duration of the injector pulse. The DME (thinks it) knows how much fuel is used for a specified pulse duration. As the pulse is now shorter (but the fuel shot is the same), the DME is reporting better mileage. But that's not what is really occuring.

Suggest you carefully check your tank inputs vs. road mileage and you'll find this out.

Jeff

[Hector]

installing the 19 lb injectors and the 3.5 bar pressure regulator? I never trust the OBC for calculating mpg... always a back of envelope calculation for me. I was also thinking that if they are getting good fuel economy then something is gotta give, either a slight drop in power output or they are really hitting the optimal a/f peak ratio. It would be good to verify the mpg as you suggest. If these mods really give you good fuel economy, then this is something that many of us would want to jump on.


Your mileage hasn't really gone up.

When you raised the fuel pressure, you increased the amount of fuel per injector pulse. In response to this, the lamda function of the DME shortened the pulse to keep the a/f ratio within the target spec. You are basically putting in the same amount of fuel to the engine but just using a shorter injector pulse to do it.

The fuel mileage is calculated by duration of the injector pulse. The DME (thinks it) knows how much fuel is used for a specified pulse duration. As the pulse is now shorter (but the fuel shot is the same), the DME is reporting better mileage. But that's not what is really occuring.

Suggest you carefully check your tank inputs vs. road mileage and you'll find this out.

Jeff

[mholbrook]

On my car, 1989 535im with 3.5 bar fpr and #19 injectors, the OBC is almost exactly what I'm actually getting dividing miles from the odometer by gallons. After checking this numerous times, the difference is less than 1/2 mpg over a 300+ mile range. That's close enough for me to just use the OBC for my benchmark. The OBC does have some adjustments supposedly but I'm fine with the feedback I'm getting.

[Jeff N.]

That's harder to answer. During WOT, the engine stops using the lamda correction and just goes off the WOT fuel map. With larger injectors and more FP, this will shoot more fuel for the specified injector pulse. Sooo.... if your engine needs more fuel at WOT, then it's a good performance thing. However, my understanding is that most of the aftermarket chips improve WOT performance by adding timing and leaning out the mixture a bit. That would mean upping the F/P & bigger injectors would counter a chip from someone like Mark D. or Jim C.

It's gets really fun when you've modded the engine like I have. Then you get into the whole custom chip world - a very dark and scary place to be! :)

[zmuff]

I guess I should have mentioned in my original post that I did verify actual fuel consumption versus OBC calculated fuel consumption. OBC function #20 correction factor is dead on to actual fuel used, so I trust my OBC readout.

[Derek A.]

As I see it the reasons for going through these motions are :
1. Installation of a better/newer injector - offering better atomization of the fuel and increasing throttle response. At the same time slightly increasing fuel economy due the better mixture characteritics of the fuel/air.
2. Adjustment of fuel pressure to accomodate the 3lb/hour flow rate of the Ford Injector vs. the stock BMW Injector.
3. The addition of more fuel at WOT will increase horsepower, at the cost of emissions and maybe fuel economy - but only at WOT throttle. I know from my carb jetting adventures that more fuel=more power to a limit where the returns are dimished and can lead to an overrich condition, but one needs to be letting black smoke trails to reach that point.

Am I correct ?

[632 Regal]

How to get it into the best power band is when the timing is perfect you increase the jet till the MPH drops then go lean untill the best MPH is obtained, which is not something very easy to do with these fuel injected pc controlled cars. My recollection is like 5 jet sizes lean from rich.

[Jeff N.]

Get the jetting right then set the timing or set the timing then adjust the jets?

Most things I have read suggest you get the a/f mixture right first then advance the timing till it pings and then retard slightly.

Jeff



How to get it into the best power band is when the timing is perfect you increase the jet till the ET drops then go lean untill the best ET is obtained, which is not something very easy to do with these fuel injected pc controlled cars. My recollection is like 5 jet sizes lean from rich.

[632 Regal]

Pinging is not engine friendly...ever. I was off in my little post above its go till its rich then lean it out till you get the most MPH not ET...I'm rusty.

As to your question the idea on timing is kinda determined by the combustion chamber design and shape, the piston dish/dome and the fuel propogation or efficiency and dynamic compression not static compression.

On that basis is how you detrmine what the full advance would be such as looking at other engines that are similar IE: 350 chevy 340 Chrysler etc usually around 34-36 degrees. After your baseline is set then you go to the fuel curves and play with them til you get the best performance THEN you would go back and tinker with the timing a few degrees.

I have seen 350 chevys with 2bbl carbs and headers that wouldnt run unless the timing was set at 60 degrees to make up for the overly lean condition. Now that cant be a good thing ya know? Talk about heat and silent detonation!

Maxing out the timing until it pings (detonates) isn't a good way to tune for best power because the most power is obtained X degrees before that catastrophic scenereo. Better to go with the seat of the pants or actually track the car to see where it likes it most.

or something like that.

[Derek A.]

All I can speak for is small block Chevy as far as timing is concerned. The goal is 36 degrees of total timing and all the advance is in by 2800 rpm. Its my understanding that the majority of the chipped cars have advanced initial timing, but the curves remain basically the same.

I guess we would need someone like Mark Dyslivia. to chime in and elabortate on the timing changes and what is the ultimate result from richening the fuel mixture at WOT.

[632 Regal]

my chip has about the same timing as stock initial cause it doesnt perform as well as Marks chip in the lower RPMS but I must say that the error codes going away and the transmission problems going away is a fair tradeoff.

I think the advance curves are also effected by the TPS, WOT, and RPMs not just a straight curve. Fuel increase in the WOT and part throttle area are the most significant gains that are acheaved by re-mapping the chips.

You dont think that anyone is really going to "chime" in and tell you their secrets do you? LOL

[DueyT]

my chip has about the same timing as stock initial cause it doesnt perform as well as Marks chip in the lower RPMS but I must say that the error codes going away and the transmission problems going away is a fair tradeoff.

I think the advance curves are also effected by the TPS, WOT, and RPMs not just a straight curve. Fuel increase in the WOT and part throttle area are the most significant gains that are acheaved by re-mapping the chips.

You dont think that anyone is really going to "chime" in and tell you their secrets do you? LOLWell...ok...15* initial and 38*-39* total on a big Mopar wedge running a 245*@0.050 cam with 92's in the mains works nicely! :D

Cheers,
Duey

[alfisti]

Can anyone describe how to remove the fuel injector harness from the injectors on the 535? I can't seem to get to the clips.

Thanks,
Andre

[myles]

On mine, I just pull gently straight up and the (electric) connector comes off the injector. The electric connector is mounted firmly in the wiring conduit, so I actually just pull gently up on the wiring conduit.

[Jason]

would love to see it