Ecu Fuel Settings??

[bill mason]

Hey guys is there a "general" rule of thumb guide as to setting a 260 ECU's fuel curve % for elevation? Perhaps something like for every 1000 foot of elevation back off fuel % so many percentage points? I realise this is a very "general" application and you have to read plugs but that it is a little difficult to cut engine off at top speed driving an Allison!! We are racing in areas that have 2000 and more elevation and it is killing our two strokes. I have ran 97% fuel setting (once) at sea level. (best she ever ran) but I didn't know that mechanic had set the ECU that low! Any help would be much appreciated and again perhaps this is to general a question? I don't want to be running on the edge but she sure is loading up when first starting.

[Jay Smith]

Hi Bill ,
To accurately plot what your engine demands are to achieve PEAK performance at different locations is a must for engine longevity and ET consistancy ( rope racing ). True altitude and weather conditions at the time you enter the water is an extreme important part of the equation also the wet bulb and adjusted altitude .... Racers that are on top of thier game use a weather station device ( I use a Kestrel 4000 ) to plot thier ecu needs as per each portion of the day's weather condition as they change rapidly and call for an ECU change from 9:00 AM until 2:00 PM ( heat , humitidy, and wet bulb , or water droplet count in the air ) ..The Kestrel 4000 also has a computer attachment for lap tops .... Me being a basic kinda guy I use a yellow legal pad to record what the weather station tells me the weather is for the time frame I am tuning for I then form a data base , I can correct now the ECU fuel curve to accieve max HP as per the information the weather station has yeilded. You will soon get a handle and a pattern started on what weather readings demands what movement on your ECU to yeild lowest ETS...You will be AMAZED the difference in what the weather station tells you the weather actuatially IS verses what you THINK it is..Spot on jetting and the ability to truely KNOW what the weather conditions are can make the difference in winning and a mid pack boat ....

Also the fuel and oil ratio mixed is important as a different brand and or octane race fuel with different specific gravity will richen and lean your engine dramaticly. As the specific gravity lessens or becomes greater it will pass through the metering system ( injector or jet ) differentely, most normal race gas will be 635 to 675 specific gravity as pump gas premium will yeild as heavy as 770 SG... At the same fuel pressure the thicker specific gravity fuel will pass through the metering system SLOWER thus the engine is LEANER and the EGTS higher. Also a choice of a different oil to fuel ratio will yeild differences as the soecific gravity will rise as fuel to oil ratio lessens...

If your wanting a specific number as per altitude changes from location to location my opinion is it can't be done accurately without first forming a data base and truely knowing what a weather station's information is yeilding as per the condition BEFORE you can make an educated guess.. IMO without a spot on true understanding of what the weather is ( altitude playing a hugh part also ) your trying to catch smoke and are doing nothing more than guessing and that causes many a guy to come out of the water after getting his butt handed to him saying " Damn I missed my fuel curve " for with the proper tools ( weather station , fuel hydrometer ) fuel curve tuning and or adjustments is a science not a guess.......

Good luck Buddy !

PS Kestrel 4000 are approx. $250.00 and available on E-Bay I bough mine used for $175.00 and I use it even to predict the weather... GREAT TOOL !!! There are others on the market BUT I was turned on to the Kestrel by a Pro Comp NHRA friend and they use it exclusively and are very successfull ...

[bill mason]

Hey as usual you are the man!! Thanks for all the info. We are headed to Houston to see grandkids today. Wish I had time to stop by and take you guys to lunch but don't think we are going to be able to. Thanks again for your help Jay. Take care ole friend

[Vecman]

Jay I understand that there is way to many variable's with
the weather and conditions. Bill, Mike (the rocket) and myself
have fought the elements at Brady, Lubbock, and San Angelo.
Pumping up the compression (200 psi) and leaning down the ecu to as low
as 95%. Egt still showing only 1100 deg. at 4400 to 5800 air on the
weather station. My question is do we keep dropping the ecu or
maybe lower the fuel pressure a couple of psi. I'm running c 12 vp racing
and cutting it to 100 octane with 93 pump. I don't know what
to do next. Any help would be great.

Thanks
Donnie Lott

[Jay Smith]

Hi Donnie,
The weather and locations where air is BAD is a big part of racing... If you are having trouble building heat I suggest adding less rface gas and more pump. As the pump gas burns HOTTER it will increase you EGTS BUT it becomes a tight rope to walk. The guy who has a handle on the weather and air conditions at a particular race site does have a distint advantage....Alway remember that the 2.5 LOVES fuel and unlike its predisor IT loves fule and doen't have to have ETS at or above 1200 to WIN, I WON several Worls and High Points Championships and never got ove 1100 degrees and hurt VERY few parts , only competitors feeling :rolleyes:

Good luck, see you in Ark...

[Sam Baker]

Jay, what's the difference between what the weather station does in this regard and an Air Density gauge? I use a Barry Grant air density gauge and have had good luck with that through the years. Bought it used on e-Bay for $60. The weather station isn't THAT much more money so if that's truly better and has other advantages, then that might make sense. I just grew up using the Air Density gauge which tells me the actual density (or "amount")of air based on an index using barometric pressure, altitude, and temperature.

Thanks in advance for your response.

[Jay Smith]

Sam,
What works for you, a instrument you can understand , your comfortable using and has helped by giving you a handle on your jetting by reading the air is what I would stick with. The Kestrel 4000 is the instrument I chose to start with on the advice of an NHRA buddy that uses one to jet a Pro Comp Car I had him as an instructor of the unit which quickly jump started me on the correct use of the machine so that is the one I chose, there are many of these types of "helpers" on the market to get a handle on the condition of air so one can develope a benchmark of air conditions verses performance increases via proper jetting to achieve max. potiential HP. The 4000 has served me and customers well over the years of racing always trying to zero in on the jetting verses the air delima to make max. HP is a challenge and a BIG part of being successfull in racing. An air density gauge should give you one element of the weather as the Kestrel 4000 gives you mulitude of funtions ( 21 if I'm not mistaken ) it can , with an added lead tie into a lap top so one can record and plot changes to the ECU verses the air conditions and will give much more information than a singular fasited gauge... This thing is SOO smart I can't even begin to understand ALL the whistles and bells it is capable of taking readings of... All for about $250.00 USD I bought mine on E-bay for $150.00 USD about 7 years ago and the size of a small pack of cigars, I spend alot of my time at the races answering raciers #1 question " Jay, hows the air ??? "

Good luck,

[Vecman]

Jay,

Thanks for the great info. Hope to see ya soon.

Donnie

[Sam Baker]

I agree with Jay too on temps. I never ran my drag over 1100 - usually between 1050 and 1100 (I had an A63). If I tried to lean it down to get the temps any higher, it would have a pronounced flat spot around 6500-7500 RPMs. So, I always ran it up a number or two and it would pull all the way through, but the temps never got over 1100.

[The Big Al]

First let me say as for as tuning that ECU your own your own.

But in Racing were the combustion engine is used, the most important weather instrument is a
AIR DENSITY GAUGE!
HANDS DOWN NUMBER 1 tool
(and I would also invest in the Kestrel 4000)

Now you will need to get one, pick your base line location (your favorite handy place you use to tune your engine) this is were you will tune your engine for your baseline. Then the information you get from that baseline you can use with the Air Density gauge for tuning.
It has been argued the digital gauges are not natural measuring tools and the built in processor rounds out the numbers. But no NASCAR, IHRA, NHRA team is without a analog one! They use this as it's most important tool.
I did also when I was drag racing and it gave me the competitive edge 25 years ago.
Go to this web site and read how it's done.
Instead of you changing jets your changing fuel curve.

http://www.stockcarproducts.com/acc17a.htm





<TABLE width=510 align=center><TBODY><TR><TD>
Air Density Gauge



http://www.intercompracing.com/images/360093-AirDensGauge.jpgAir density is the single-most important engine tuning parameter in all forms of professional motorsports because it is derived from air temperature, barometric pressure, and humidity.
This tool will allow you to properly tune your engine for optimum performance.
Carrying case and instructions with recommendations are included.
<TABLE align=center><TBODY><TR><TD>

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[95RapidRiot]

Doesn't the "altitude density" give you a accurate reading for current air density. It is a reading the Kestrel 4000 gives. When i looked up altitude density it said it makes corrections for temperature, altitude, and humidity. Unless I am not understanding it properly. Jay what do you think? I would like to get a Kestrel 4000 to tune properly.

THANKS!

[Jay Smith]

IMO I would'nt trade my Kestrel 4000's MULTI funtionion abilitys for ANY single funtion gauge PERIOD ! IT DOES IT ALL......

Others can do as they please, after all we living in America still have the freedom of choice and is still an option, as for me I'll stick with the Kestrel 4000.....

HAPPY HOLIDAYS,
Jay

[rpm racing]

Jay I agree with a lot of what you are saying here...but I have never heard of normal race gas with such low specific gravity. I know some of the really pricey crap like c44 have high 600's but I know none of the Sunoco or c12 stuff is below the low 700's??

what are calling normal race gas??? just curious because I have talked to you in the past about cutting gas and this would change mix ratios and results.

[Jay Smith]

Checking SG MUST be done with the proper accurate SG gauge of coarse as well as the fuel temp being tested MUST be lowered to a specific target temp. number by chilling so that tests are consistant and concure with the standerdised testing procedures all fuels adhear to to check thier SG quotes so that they are the same at different testing points geographicley..Some that just pull fuel from a drum or boat fuel tank and throw a hydrometer in could and WILL be getting werid and incorrect data. Also 2 cycle oils that are mixed in fuels that is being tested will also taint the test and yeild a bad or incorrect results..

As you say most very high octane with oxygen added ( C-44 ) racing motor gasolines are high in the 600's SG .. I haven't had to "weigh" fuels lately ( 10 years ) and was mistaken about low side numbers being as low as 635 ish. BUT the super unleaded motor gasolines of today market may even be a bit higher than 770 with the addition to the eth. as it ( eth, meth. ) is very heavy ( I'm thinking over 800 ) and will add consideratably to the SG weights , I'm told , at work, that the newer formulatiuons of motor gasolines vary greatly even from rural to metro. city destonations with the high populated areas recieving fuels with more of an ox. agent to comply with EPA specs and requirements to create a hot more effecient burn ..

Thanks for keeping the "ole Man's" brain working..:p

HAPPY HOLIDAYS,
Jay