Quick ECU ? for Robert and Wes

[pdqwrx]

Hello Guys- There has been alot of talk about the available ECU maps for 91 or 93 octane......What about a 87 octane map so we can n ot get as rapped this summer by high gas prices. It would be ideal for me to have a 91 octane "High Performance" map and a 87 octane "Economy Map"...

Just a idea, I use my car alot and would love to be able to save some money.

ThanksScott

[maxnix]

Mechanical engine parameters not set up for 87 octane.

The main changes in the performance ECU is to lean out more and change timing advance on the camshafts earlier. They are all based on premium.

How much do you think you would actually save burning 87 octane? $200-$300 per year? Not worth it for the diminished performance with even standard ECU.

[Q45tech]

Robert:

Can you describe the way the KS subtract works [initial steps down and recovery rate, does it desensitize with rpms cutoff etc] ......is there a load cell/temp component......ignored at WOT?

Also how does aircon signal on affect advance [just increase load cell position?] other than WOT cutoff switch. What does ecu do when AC on that it doesn't do with AC off at WOT.

It appears that more than just the compressor drag is slowing acceleration.

People might be interested in the battery voltage compensation of injector open time trim.....big amps big current draw..oscillating injectors on Bass Notes.

[elwesso]

Our program will be safe for 91 octane and we dont really want to go below that......

[DrewQ45]

Our program will be safe for 91 octane and we dont really want to go below that......

Gas is going to > $3.00 by summer. I'm willing to risk the Q.......NOT!!!!

Sure would be nice to have that option though. I'd definately invest in another chip if I could sacrifice performance and run 87 octate SAFELY.

[elwesso]

in theory, you COULD run 87 even with our ECU... Since our KS map is the same as stock, it shoudlnt detonate using 87... but I cant recommend that at all, but in theory, your not oging to blow your engine up by running 87 on our ECU..

[maxnix]

Gas is going to > $3.00 by summer. I'm willing to risk the Q.......NOT!!!!

Gasoline is $8/gal in Europe now. We still get it cheap.

Wait until China revalues the Yuan upwards 30% (true market value). You think the world's second largest user of oil might buy a little more? With inflation coming back, we might look back in two years and think of these as the good old days when gas was only $3/gal.

Then there is India's growing economy.
Modified by maxnix at 5:55 PM 4/12/2006

[redmanfx]

Mark my words......$5.00 a gal here in 2 years!! That'll put a dent in it.

red

[Q45tech]

The problem is US gasoline is not speced the way the gasoline is in Europe and Japan.

The averaging TRICK allows garbage to look good/satisfactory on the pump decal.EACH MON POINT COST refiners 4-5 times more than each RON POINT.

No way does the best US [non racing] gasoline meet a minimal 87 MON

The computers blend to a minimal cost solution that won't get the board of directors burned at the stake by car owners.......the average bulk of consumers. High performance owners are ignore for the good of the many. Just as Premium is ignored because only 15% BUY IT.Reducing fuel prices by a few pennies........actually to produce a quality product would cost another 5 cents but this gets multiplied thru the distribution chain.

Unfortunately the Q engine cannot accept crappy gasoline.

If you listen to the KS output you will be shocked at the amount of mild knocking covered up by the sound deadening between driver and engine.

Typical Properties of a quality racing galone

Research Octane (RON) 114 Road Octane (RdON) 110 AKI (R+M)/2 110 Motor Octane (MON) 106 Specific Gravity 0.728 Gravity API 63 Color Red Lead, gm/gal 3.0+ Reid Vapor Pressure 6.5

Fuel Property Typical Specifications of an unleaded racing gasolineSpecific Gravity 0.763 Pump Octane (R+M)/2 98 RON 104 MON 94 Reid Vapor Pressure (psi) 5.7 ASTM D86 Distillation (deg. F) Initial Boiling Point 92 10% 185 50% 221 90% 228 Final Boiling Point 247 Oxygen (weight %) 0 Leaded No - for off road use only Color Green

[RobertsnewQ]

In THEORY I could set up an iginition map that would not ping on 87 octane, but the engine would be an absolute DOG. In addition, the retarded timing would reduce VE, causing fuel mileage to go down. I suspect the end result would be a wash.

Robert:

Can you describe the way the KS subtract works [initial steps down and recovery rate, does it desensitize with rpms cutoff etc] ......is there a load cell/temp component......ignored at WOT?

Basically here's how the ignition code works:

-There are two (sometimes three) ignition maps. Low Octane (knock) and Hi Octane (no knock).- When the ECU determines the timing for a given cell based on RPM and load, it also looks at the same cell in the other map. i.e. if the ECU is reading off the hi octane map, it looks at the low octane map. -It stores the difference between the two cells. That is the maximum "range" of timing at that load/rpm point.- Every time the key is turned on, the ECU reverts to the Hi octane map.- Every time a knock is detected (in a set timing window that varies w/load and RPM) the knock counter is incremented.- After a set number of ignition cycles with knock events (varying according to RPM and load via a simple two-row/three-column map) the ECU retards timing from the hi octane map (assuming it is still using the hi octane map). It retards by a set (and changeable) number of degrees each time, which happens to be 1 in the stock ECU.- When the timing reaches the "floor" set by the lo octane map, the ECU switches to that map. - If the ECU is running from the lo octane map, it advances timing after each X number of engine cycles WITHOUT knock. If it reaches the "ceiling" set by the hi octane map, it switches to that map.

The knock sensor reading is gated according to crank degrees, and the overall sensitivity is controlled by several filters. Above X RPM (2000 in USDM, 2500 in JDM) sensitivity decreases more significantly. There is also load-based filtering of knock sensitivity.

Quote »

Also how does aircon signal on affect advance [just increase load cell position?] other than WOT cutoff switch. What does ecu do when AC on that it doesn't do with AC off at WOT.

It appears that more than just the compressor drag is slowing acceleration.

People might be interested in the battery voltage compensation of injector open time trim.....big amps big current draw..oscillating injectors on Bass Notes.[/quote]On the AC question, the AC compressor is turned off above 4600 RPM. Oddly enough, there is no throttle or load-based cutoff.

Once turned off, the AC relay is only off for about 6 seconds or so, then cycles back on for 6 seconds, then off, until the RPM drops back below 4600.

The injector dead time is affected by battery voltage. So is the ignition coil dwell time. Lower battery voltage means longer dwell and longer dead time.

[elwesso]

So lets say I have like 11.9 volts at the positive terminal up front (Since my battery is in the trunk). Is that enough to matter?

[RobertsnewQ]

So lets say I have like 11.9 volts at the positive terminal up front (Since my battery is in the trunk). Is that enough to matter?

No, the ECU compensates for it, as long as it is above 10.6v

[rsiwicki]

On the AC question, the AC compressor is turned off above 4600 RPM. Oddly enough, there is no throttle or load-based cutoff.

Once turned off, the AC relay is only off for about 6 seconds or so, then cycles back on for 6 seconds, then off, until the RPM drops back below 4600.

Okay....now I guess this finally explains why I seem to be the only one noticing that my AC would shut off when I decided to lay down my temporary raceway on I-95 and wind the speedo out to 150mph. This is the first justification that I have heard that explains that the AC shut off is normal and to be expected under certain conditions. Well...it ain't my car anymore, but I still like to check out NICO every now and then.

[Q451990]

The A/C cut-out is definately normal... I suspect the compressor isn't designed to turn at that high of an RPM.

Heath

[elwesso]

Or probably it would cause too high of a pressure where the dual pressure switch would just cut it off anyway..

[DrewQ45]

The A/C cut-out is definately normal... I suspect the compressor isn't designed to turn at that high of an RPM.

Heath

I've never noticed the cut-off. At that RPM I usually mean business and have already turned off AC and other unnecessary accesories manually hoping to maximize power...(old school habit)

[elwesso]

I am in the same boat drew..... I do that too

[Q45tech]

the retarded timing would reduce VE.

The VE in the real sense is a mechanical function: the restrictions of the design and the valve curtain area [cams]. The amount of filling of the cylinder vs the theoretical ideal based on displacement and atmospheric pressure/temperature at a certain rpm.............VE 90% vs VE 93%.

Obviously if you squirt fuel into the air stream it displaces the air by some amount. If you change the VVT cut point rpm you can change the VE at that rpm point. The ecu load table steps are the result of a measurement with a Lab GRADE MAF and the oem maf is modified by a TRANSFER FUNCTION equation to approximate the true air flow give or take say better than 95% accuracy when brand new with an oem filter and the oem designed air intake system sitting in front of the MAF.

Believe Robert was alluding to the fact that as you reduce advance, you must enrichen the fuel to maintain a suitable flame speed to increase the probabilty of a more complete burn. If you squirt more fuel the VE does go down but not related by the advance pre se.

Nit picking for sure since we don't have accurate REAL VE numbers for the Q engine. Obviously a 1% improvement in VE has the theoretical ability to increase power output by 1%.

VE can be approximated by measuring the pressure changes in the plenum.

[Q45tech]

Lowering the 4600 rpm cut off might be useful in the situation where you have need of an emergency pass at less than 60-63 mph.

Say 3700-4,000 [50-54 mph in 2nd 90-93] ok to cycle off/on at 110 mph in 4th instead of 138 mph as oem.

As many can tell I'm always hung up on the common situation where you are stuck in 2nd before the torque peak hits ~~ 2000-3700.........sometimes every 0.1 second counts = 5 feet.

I thought of another trick lock out 1st gear start/down shift when it's raining [windshield wiper on] for those without TCS........again we need TCU mods or a piggy back semi mod.