I just got my s300 and am installing it along with a aem uego for my turbo z6 build. My plans r to take my z6 out this weekend and put a new head gasket, arp hs, and a lil bit of goodies I got for it. So I'll b riding for a lil while without a turbo so I thought I'd play around with it a lil and c what kind of milage I can get out of this thing without having to worry about emissions. So if Im pulling fuel at light load around 55-60mph what should I b doing with the timing. Could I get better milage by running 93 and adding 1 to 2 degrees while I pull some fuel to prob around 17-19:1 depending on what it does or is that a reciept for disaster, I understand running real lean will produce alot of heat and emissions. Should I just keep the stock timing and 87.

I will have a intake, tb, skunk 2 im, headers and exhaust. U know, a lil ve improvers.

 

Its probably the dumbest thing you can do by starving your motor. Keeping it stock or within reasonable AFR would probably be a smarter idea. Running high 14's to mid 15's is for your AFR would probably be best while cruising. And stock timing is always preffered unless you have aftermarket cams/ cam gears.

 

With good distrubution comes a decent running motor on lean afrs. Like what kind of timing are these direct injected motors running when they r pushing 22:1 afr (in europe its much leaner than this).

 

when cruising (low loads) it is safe to run up to 16:1 AFR. running high 14's to mid 15's while cruising is just wasting fuel, but its a good target for low loads (mild acceleration).
sorry but I can't help you with the ignition timing specifics, but one way to check is to go on the highway and watch vehicle speed vs throttle position. If you change the timing and your throttle position raises (you'll have to watch the exact % on a computer) while keeping a constant speed, then you know your making the same power with less throttle and hence increased possible fuel mileage.

 

Good idea I wonder if cruise control could help with this. Im thinking maybe I should invest in a egt guage. I just dont want the pistons to be getting super hot running so lean over long periods of time. I wonder how much that would effect the coolent temp

 

depending on your injectors, head flow.....etc advancing ignition timing will allow you to run leaner mixtures before getting a misfire. Running a leaner mixture will raise EGT which in turn will put unnecessary heat in the combustion chamber. To combat this, you add timing to drop EGT's. I have ran my old h23vtec with RDX injectors at 55psi to 17.5:1 cruising without a hint of misfiring. At cruising, low rpm speeds you can get away with running lean mixtures as the cylinder pressures and heat are so little compared to higher rpm and higher loads. I typically cruised in the 16.1-16.5:1 area.

i would recommend testing whatever works best and verifying your test by properly understanding what the spark plug is trying to tell you.
________
ANGELINA JOLIE NUDE

 

So ur saying additional ignition timing will cool it down. I was thinking the opposite, i used to run my b16 at 17:1 at light loads but I never messed with timing. It had rc550 and now Im running siemen deka 630cc on a z6. I just dont want to melt the piston on a hour long freeway ride. What can I look for if the pistons are getting to hot...misfires, rising ect, nothing haha?

 

I ran mid 15:1 on light loads on my internally stock b20 and took it on a road trip where the car drove for over 30 hours straight, twice, and had zero issues.

 

yeah but mid 15s isnt lean at all. What kind of milage did u get? Mayb I'll go ahead and throw in some colder plugs also

 

With a static ignition timing, the more lean the combustion event, the higher the EGT's, but your combustion temperatures fall.

Peak combustion temperatures are always going to be at stoichiometric air-fuel and MBT. EGT's are not always a direct relation to combustion temperature.

You may need to run 45-55* BTDC of ignition when attempting to tune lean cruising. If you encounter lean misfire, add some timing in that area. I've been able to sustain ~16.5:1 with about 48-50* BTDC on my 2.0L in the low load (18+ inches-Hg), higher RPM cruising areas.

AFR's in the 19-23:1 range are common on lean-burn ICE's, but these engines also have very specific cam profiles and cylinder head design to support.

 

wow this thread is teaching me alot, whenever i'm cruising i'm in the 15's and 16's alot, i never smelled anything bad and plugs looked great.. also, i've ran the same tune for almost a year now and no problems. crusing at 4,000 rpms at 80 mph at 14-15 afrs and i've been fine.


i've been wondering how the motor has stayed together, but i guess it isn't that bad of an afr

 

ICE Motors? I understand fuel burning on the way out increases egt's but ur saying if I lean it out past 14.7 egts will fall but combustion temp goes up? and at mean best torque and 14.7 egts will be the highest? That seems unsafe to me to be running stoich while ur making best torque and best torque comes at 12.5-13.3 anyways. Ur two liter have any internal friction coatings?

 

if you are tunning for mpg's, you can always set a base tune and go on the highway and see the injector ms. and throttle position. lean and adjust timming so the injector ms is at its smallest without having to give it alot of throttle. to maintain your cruise speed.

doesn't work for all types of driving. But when taking long trips I tend to do this ( or play with the temperature compensation map as I might drive at freezing temps or hot temps ).

Forget what injector ms is for cruise at for 100 km/h, but took some playing around to get back to stock highway cruising mpgs and then a little better.

 

Internal Combustion Engine

You have it backwards. With a static ignition timing, the leaner the mixture gets, the less efficient the burn becomes. The trailing edge of the combustion event can even occur during EVO, which is where your EGT's increase. If you are tuning for a stable lean mixture, you will need to advance the ignition point so that the inefficient slow burning lean mixture releases most of its energy during the power stroke, instead of the exhaust stroke.

You don't need an EGT gauge to properly tune lean cruising conditions. Reduce fueling until misfire occurs, add timing until misfire is eliminated, repeat until adding timing no longer has an affect.

Combustion temps will be the highest at MBT and the stoichiometric ratio of fuel. By definition, that is the theory behind stochiometric ratios - the most efficient energy conversion between air and fuel.

Using Heptane and Isooctane, ie: 'gasoline', stoichiometric ratio is 14.7:1. Actual fuel blends contain dozens of other additives such as ethanol/MTBE which adds oxygen to the fuel, reducing the stoichiometric ratio. In practice, actual stoichiometric ratios for pump gas are typically between 13.5:1 and 14.0:1.

It may seem unsafe because that mixture is the hottest burning, which increases the chance for predetonation (knock). Usually your best power will come at the expense of the stoichiometric ratio, because you can achieve higher cylinder pressures using a richer mixture and MBT.

Negative.

 

Thank you type r I was just worrying about overheating it if the timing got two advance over long periods of time. I never took the heat into account I just always thought that was the ratio for gasoline when all fuel is burned. Now that uv said that it makes perfect sense. I could use some help with the s300 also like wiring up full throttle shifting. Do i need some sort of aftermarket clutch switch or can i use the factory one. Do i need to do any wiring or can i just turn it to always on?

 

it took me about a 2 months between summer/fall/winter ish to "perfect" my fuel/temp. compensation tables. if you need any help with those i can throw some numbers your way.

92typer, i'm willing to compare mine to yours to see how well it looks

 

I don't know how I feel about that statement especially considering there is 10% ethanol in most fuels.

 

it is most important to just watch the plugs, i dont think they can lie (sure hope not). I found 16:1 to be safe because the plugs looked very similar all the way up to that point but going past 16:1 they started to lose their color and turn white.

 

Isn't that only in the winter months, then in the summer it's much less than 10%?
Isn't a 10% ethanol blend called gasohol or something like that?
I'm also curious to know what's the max afr for cruising. My tuner got me to about 15:1 afr while cruising at 4k rpm and now I seem to be using more gas than before the tune. I don't know what cruising afr was before the tune though.

 

im having the same issue. =( at cruising and driving around town, which is stop and go, i usually run anywhere between 12.5-13.8 now today i turn on my car to warm up for 10 min. then im off, and i notice light accelaration my AFR's were at 16-17.6 i was like wow!! thats not good. then under boost it falls down to 11.2-12.4. then i jump on the freeway and at cruising 70mph my AFR's are at 16.8-17.9 but mainly in the 17's. can you guys let me know whats happening? im running 550's with stock fuel rail and fpr. with a walbro. its a built LS/Vtec motor with standard timing.

it freak me out because arriving to work it was in the 17's and it started stuttering.

 

how long has it been since you changed the plugs?
was the engine street tuned or just dyno tuned?
was cold start tuned?
post start tuned?
IAT's and ECT's compensated for?
what climate were you tuned in?

 

just dyno tuned.
yes it was cold start but got it up to operating temp before tuning. had 2 1/2 hours of tuning.
i took it to the dyno on a trailer.
yes that day was a hot day but it was tuned towards the evening. (cooler temps) today its warm. im sure that was compensated.

 

i havent change the plugs within the last 10k miles.
what plugs do you recommend? im planing to boost up to 20lbs in a couple weeks with a new tune. what kind of plugs you recommend?

 

ngk coppers, i used to buy iridiums cuz some asshats recommended them. and they must be goood because they're expensive.. right? WRONG!

also, coppers come in a variety of different heat ranges, and are only ~1.99 a plug so u can play with heat ranges and not be broke!

 

from my understanding stoic.(14.7) is only used as a chemicaly complete burn, IG: it has the least emmisions

you can run at a 15.5 (or lower but I dont) at LOW load with no significant drawbacks

when in a low load situation (shallow throttle angle) your engines will have a much lower VE and a large percentage of exhaust gas present into the incoming charge. This will prevent any significant detonation (uncontroled flash) but may raise the EGT's significantly if you go below 15.5 (like 16's).