mike somethin was his name. he is out of conn. this sled is ABSOLUTLY MINT !!!!! he only rode it in maine. the milage is 2900, but thats when it was unhooked. i felt up there, the boot was off and it wasnt even tight. lol anyways. i stripped it down to the bulkhead for a good cleaning. i broke the original blue locktite on everything !!!! suspension bushings... omg this thing looks like new. nice custom airbrush paint on the cowl. an absolute steel. i would have not bickered about price even if it were 1000 higher.
getting ready to take son for a ride, hes buggin the crap out of me. dad dad dad dad dad dad....... ok lets go. lol
YAMMIEGOD3:16
Active member
SOUNDS LIKE A GREAT SLED. SEE YA SOON. 3:16 (yammie tony)
bufalobob
Member
tony:
most people don't understand jetting ( even some engine builders ). there's 2 types of jetting: lean & rich. there is no such thing as perfect jetting. why, because air density is in a constant state of flux. on 3/17/08 i went to dynotech in batavia, ny to tune my 835. it was 40 degrees & 107% air density. when i got back to benders in colden the air density was 101%...that's 6% less air. that means my very safe 440 mains were now overly rich & should be 410's. so guess what i did...i put in 460's. why, because it's a trail sled & i don't want to be bothered changing jets regularly or carrying octane booster. who knows if the premium fuel i'm buying @ the pump is 73 or 93 octane & what if the temperature dips below 0 degrees & air density goes up 5%?
i have to laugh when someone posts pictures of their piston tops & the so called experts give their opinions. there will be 2 finger nail wash marks & they will say that's perfect... maybe for a race engine but not a trail sled. there are way too many variables w/ a trail sled...quality of fuel & air density. if you don't have large areas of wash around the transfers then you're simply tooo lean & will be suffering engine failure.
bob
most people don't understand jetting ( even some engine builders ). there's 2 types of jetting: lean & rich. there is no such thing as perfect jetting. why, because air density is in a constant state of flux. on 3/17/08 i went to dynotech in batavia, ny to tune my 835. it was 40 degrees & 107% air density. when i got back to benders in colden the air density was 101%...that's 6% less air. that means my very safe 440 mains were now overly rich & should be 410's. so guess what i did...i put in 460's. why, because it's a trail sled & i don't want to be bothered changing jets regularly or carrying octane booster. who knows if the premium fuel i'm buying @ the pump is 73 or 93 octane & what if the temperature dips below 0 degrees & air density goes up 5%?
i have to laugh when someone posts pictures of their piston tops & the so called experts give their opinions. there will be 2 finger nail wash marks & they will say that's perfect... maybe for a race engine but not a trail sled. there are way too many variables w/ a trail sled...quality of fuel & air density. if you don't have large areas of wash around the transfers then you're simply tooo lean & will be suffering engine failure.
bob
valin
Active member
107 is damn good air. Almost as good as when I was there at 110! We're lucky to get over 100 here.
bufalobob
Member
ryan:
2 area's i've raced & trail ridden w/ lousy air is north bay & old forge, ny. in n.bay @ 30 degrees i had the same air density as lancaster, ny dragway in july @ 65-70 degrees.
bob
2 area's i've raced & trail ridden w/ lousy air is north bay & old forge, ny. in n.bay @ 30 degrees i had the same air density as lancaster, ny dragway in july @ 65-70 degrees.
bob
bufalobob said:
If you can't control the loud lever based on conditions, I agree that you should jet for the worst case.
Holding it to the bar for a 1/2 mile with ragged edged jetting and unknown fuel is a recipe for engine failure.
I'd rather putz around during lean a/f conditions while monitoring EGTs than put up with burbling, excessive carbon deposits and HCs.
Mac
Member
780 Bb
Bob - Your scenario about jetting is absolutely correct when trial riding. The problem is I'm usually chasing maximum power. When tuned correct my plugs are a light to medium tan color representing as lean as I am willing to go in 1000 to 1200 foot pulls on the lake. Lean is where the power and fun is. When I add fuel say two or three steps richer the motor feels flat. Whats a guy to do? I run a blend of AV 100 low lead 50/50 with premium feeling protected somewhat. Your thoughts.
Bob - Your scenario about jetting is absolutely correct when trial riding. The problem is I'm usually chasing maximum power. When tuned correct my plugs are a light to medium tan color representing as lean as I am willing to go in 1000 to 1200 foot pulls on the lake. Lean is where the power and fun is. When I add fuel say two or three steps richer the motor feels flat. Whats a guy to do? I run a blend of AV 100 low lead 50/50 with premium feeling protected somewhat. Your thoughts.
bufalobob
Member
egt's are distracting & useless on the trail.
they are a helpful tool to a experienced tuner when racing combined w/ reading piston wash & reading spark plugs.
the problem w/ egt's is that when an engine starts to go lean the protective layer of cooling fuel on the piston dome burns off & the piston now starts to absorb the combustion heat instead of sending it out the header pipe to the egt probes. so the probes can't sense what's really going on in the engine & everything looks fine on the display. then the headlight goes out.
the other problem is the probes themselves. they can be fragile & susptible to failure & erratic readings.
bob
they are a helpful tool to a experienced tuner when racing combined w/ reading piston wash & reading spark plugs.
the problem w/ egt's is that when an engine starts to go lean the protective layer of cooling fuel on the piston dome burns off & the piston now starts to absorb the combustion heat instead of sending it out the header pipe to the egt probes. so the probes can't sense what's really going on in the engine & everything looks fine on the display. then the headlight goes out.
the other problem is the probes themselves. they can be fragile & susptible to failure & erratic readings.
bob
This is why I love my DCS!
I don't have EGTs on any of my trail sleds and don't plan on adding them, but I think I am going to add an accurate temp guage to my SRX. The reason being that I am getting DCS flashes in low snow[poor exchanger cooling] and after coming off of a slow bumpy portage then back onto an emmediate hard pull on the lake. This is with conservative jetting and known High Octane fuel. I do not get the DCS flashing even on long hard pulls in good snow conditions for cooling, so I am deducting that high engine temp is triggering some detonation and setting off my DCS!? The small Mountain Viper rear exchanger on my 144" tunnel extension I believe is contributing to my occasional temp issues...but still no high temp light.
I don't have EGTs on any of my trail sleds and don't plan on adding them, but I think I am going to add an accurate temp guage to my SRX. The reason being that I am getting DCS flashes in low snow[poor exchanger cooling] and after coming off of a slow bumpy portage then back onto an emmediate hard pull on the lake. This is with conservative jetting and known High Octane fuel. I do not get the DCS flashing even on long hard pulls in good snow conditions for cooling, so I am deducting that high engine temp is triggering some detonation and setting off my DCS!? The small Mountain Viper rear exchanger on my 144" tunnel extension I believe is contributing to my occasional temp issues...but still no high temp light.
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YAMMIEGOD3:16
Active member
BOB GREAT POINTS, PROBLEM WITH NYIRP IS I BELIEVE THAT TRACK IS AROUND 1600 F.T. (not shure) I KNOW THERE IS ELAVATION THERE. IF YA GET GOOD AIR, BY NIGHT FALL DUE ALWAYS SETTLES IN, I HAVE FOUND MY BEST PERFORMANCE EITHER RACING OR JUST OUT SMASHING THE TROTTLE IS AT SEA LEVEL OR BELOW. NOW OF CORSE THAT ALL COMES INTO PLAY WITH AIR DESTINY AND YOUR JETTING. NO DOUBT THE SLED WILL PERFORM BETTER AT 600 F.T. THAN 1700 F.T. 3:16 (yammie tony)
Not uncommon in my neck of the woods to see CRADS over 110...always great for making power but have to watch the jetting!
harness racer
New member
sideshowBob said:
Bob absolutely put on the digital temp gauge for $89.00 , srx thermostats are seriously starting to fail given their age I have replaced 4 of them the pin lodges itself sideways and jams the housing closed given time , i beleive it is somewhat of a process aswell . If you have done everything you can to solve the temp issue , then go to the crank , there is a brass gear that is pressed by 2 bearings , not pined or splined , it drives the impeller shaft and it is spinning , less noticable at high rpm as it will centrefugally spin the shaft some . It is absolutely not noticeble @ start up as the brass gear swells faster then the crank , untill higher temps ..
The temp gauge will help diagnose this alot easier ...and hopefully some of the symptoms i described will help others who like me struglled for 2 years with this ..
vince
bufalobob said:
Air temp,humidity and barometric pressure all have a differance on air density. With higher air density you have more oxygen going into the cylinder, and vice versa the other way. The problem lies within the same change in air density also changes the pressure on the gas in the float bowl, so if the RAD drops, this will lean out the mixture due to lower air pressure,but only to a certain degree. The jetting doesnt follow the change in RAD percent for percent by any means... a drop in RAD from like 15% would only require a change to the jetting of 4-5%! !
You also have to have a referance point to which use a scale to refer to the size to go to with using weather station to tune from.
You have to previously have a baseline setting with all the same air temp,humidity,RAD recorded on that day in those exact conditions and then preferably at differnt RAD to make a adjustment of any value.
bufalobob
Member
mac:
if the motor feels flat that doesn't mean it's making less power or going slower. the only way to be sure is timers, radar or gps.
ssbob:
i wish i had dcs on my 835. your theroy is correct on the detonation issue. i have done a lot of testing w/ 2 cycle cooling systems & can confidently tell you to pull out the thermostat. valin may want to chime in on the cooling issue. if i remeber correctly he found a significant reduction in coolant temperatures by eliminating the t-stat.
yg316:
i think your confusing lancaster speedway w/ nyirp ( liecester,ny ). lancaster speedway is about the same elavation as n.bay.
mrviper:
an air density gauge measures a combination of temperature & atmospheric pressure - not humidity. Compared to the differences made by temperature and air pressure, humidity has a small effect on the air's density. But, humid air is lighter than dry air at the same temperature and pressure. since cold air is generally very humid to begin with it is basically irreiivant to calculating winter jetting. jim @ dynotech enlightened me on this phenom many years ago. also, the reason for routing the vent hoses to the air box is to eliminate the difference in fuel flow from the float bowls caused by different atmospheres in the belly pan & the inside of the air box.
since humidity is not a factor in winter tuning, a weather station is not necessary. a simple rad gauge is all that is necessary. you will need to establish a safe baseline jetting ( best done on a dyno ) and then it is a lineir equation after that. if the rad is up 5% then your jetting goes up 5%. as i have explained previously you need to use a mikuni slide rule if you have round main jets & convert them to an equal hex jet size. you then multiply the + or - % of change in rad by the comparable hex jet size & reconvert to round jet size.
bob
if the motor feels flat that doesn't mean it's making less power or going slower. the only way to be sure is timers, radar or gps.
ssbob:
i wish i had dcs on my 835. your theroy is correct on the detonation issue. i have done a lot of testing w/ 2 cycle cooling systems & can confidently tell you to pull out the thermostat. valin may want to chime in on the cooling issue. if i remeber correctly he found a significant reduction in coolant temperatures by eliminating the t-stat.
yg316:
i think your confusing lancaster speedway w/ nyirp ( liecester,ny ). lancaster speedway is about the same elavation as n.bay.
mrviper:
an air density gauge measures a combination of temperature & atmospheric pressure - not humidity. Compared to the differences made by temperature and air pressure, humidity has a small effect on the air's density. But, humid air is lighter than dry air at the same temperature and pressure. since cold air is generally very humid to begin with it is basically irreiivant to calculating winter jetting. jim @ dynotech enlightened me on this phenom many years ago. also, the reason for routing the vent hoses to the air box is to eliminate the difference in fuel flow from the float bowls caused by different atmospheres in the belly pan & the inside of the air box.
since humidity is not a factor in winter tuning, a weather station is not necessary. a simple rad gauge is all that is necessary. you will need to establish a safe baseline jetting ( best done on a dyno ) and then it is a lineir equation after that. if the rad is up 5% then your jetting goes up 5%. as i have explained previously you need to use a mikuni slide rule if you have round main jets & convert them to an equal hex jet size. you then multiply the + or - % of change in rad by the comparable hex jet size & reconvert to round jet size.
bob
Humidity does in fact play a role,it effects the the true air density. Using your RAD guage you would need to correct the reading for the relative humidty to get a actual RAD. The formula to do this is: Corrected RAD= RAD reading- (S%xRH,divided by 100). S%=saturation percentage,and RH=Relative humidity. Definition of relative humdity:
RELATIVE HUMIDITY:
Relative humidity (RH) (expressed as a percent) also measures water vapor, but RELATIVE to the temperature of the air. In other words, it is a measure of the actual amount of water vapor in the air compared to the total amount of vapor that can exist in the air at its current temperature. Warm air can possess more water vapor (moisture) than cold air, so with the same amount of absolute/specific humidity, air will have a HIGHER relative humidity if the air is cooler, and a LOWER relative humidity if the air is warmer. What we "feel" outside is the actual amount of moisture (absolute humidity) in the air.
Now,I agree that very cold air below 20 degrees is lower in humidity,but you get the most snowfall from 25-35 degrees, btw,snowflakes are made of water. We are talking about trail riding you say and these temps are very often observed.
Water molecules are heavy,and they easily change the air pressure. This is whats done(read) with a weather station, something I bet not 3 members total here own,nor need to for trail riding. Higher humidity results in smaller oxygen molecules being drawn into the cylinders,with water molecules taking up space theres more space between the fuel,air molecules because of the water,this in fact slows down the flame front. The fuel molecules would normally go from one to the other in the flame front/burn process get slowed down by the water not being a part of the process
This is all part of the correction factor used by dyno software, not just your RAD guage and a mikuni slide rule.You also can do alot of things with a dyno but finding your exact jetting wont be one of them as the load applied via the dyno is not the same as what the engine sees in the chassis. I have seen time and time again the guys go to the dyno and they jet the sled for max power and monitor the bsfc, get it setup safe and good power. Take the sled as setup to the track and it wont run rpm or perform good at all,go back to the field tuned/tested jetting setup and the sled pulls correct rpm and performs. Most guys ride sleds for more then a 8-12 second duration dyno sweep. Dyno is a very usefull tool but its definitely not the absolute!
RELATIVE HUMIDITY:
Relative humidity (RH) (expressed as a percent) also measures water vapor, but RELATIVE to the temperature of the air. In other words, it is a measure of the actual amount of water vapor in the air compared to the total amount of vapor that can exist in the air at its current temperature. Warm air can possess more water vapor (moisture) than cold air, so with the same amount of absolute/specific humidity, air will have a HIGHER relative humidity if the air is cooler, and a LOWER relative humidity if the air is warmer. What we "feel" outside is the actual amount of moisture (absolute humidity) in the air.
Now,I agree that very cold air below 20 degrees is lower in humidity,but you get the most snowfall from 25-35 degrees, btw,snowflakes are made of water. We are talking about trail riding you say and these temps are very often observed.
Water molecules are heavy,and they easily change the air pressure. This is whats done(read) with a weather station, something I bet not 3 members total here own,nor need to for trail riding. Higher humidity results in smaller oxygen molecules being drawn into the cylinders,with water molecules taking up space theres more space between the fuel,air molecules because of the water,this in fact slows down the flame front. The fuel molecules would normally go from one to the other in the flame front/burn process get slowed down by the water not being a part of the process
This is all part of the correction factor used by dyno software, not just your RAD guage and a mikuni slide rule.You also can do alot of things with a dyno but finding your exact jetting wont be one of them as the load applied via the dyno is not the same as what the engine sees in the chassis. I have seen time and time again the guys go to the dyno and they jet the sled for max power and monitor the bsfc, get it setup safe and good power. Take the sled as setup to the track and it wont run rpm or perform good at all,go back to the field tuned/tested jetting setup and the sled pulls correct rpm and performs. Most guys ride sleds for more then a 8-12 second duration dyno sweep. Dyno is a very usefull tool but its definitely not the absolute!
I too have always used humidity in my CRAD calculations but in the winter conditions we are normally racing in, it generally has the least effect on the final value, when compared to elevation, barometric pressure, + temperature.
bufalobob said:
Distracting at WOT, yes. Useless on the trail, mostly but somewhat helpful to confirm drastic changes of atmospheric conditions, fuel quality and to a lesser degree, coolant temps. In other words, the increases in EGTs from lower ambient temps remind me to govern the lever. As you and others suggest, temperature isn't the only variable that effect combustion temps so IMO EGTs are a step up from a simple thermometer. They also tell me when the fuel I just put in the tank might not be what is advertised... across multiple throttle openings. I don't rely on an absolute number but do rely on changes seen with various conditions.
Agreed that the probes are fragile and if I was only monitoring one lung it'd be useless, but having three gives a comparision so when one probe starts to go erratic (I've replaced several), it shows up on the other two.
If I had DCS I wouldn't have bothered installing them (well, that and the fact that I had them from a previous sled and the tach is a bit more accuarate and has recording capabilities).
bufalobob
Member
mrviper:
srx154 wanted info on tuning a 835 srx snowmobile engine...not a nhra top fuel engine. a rad gauge & bendalight is all he needs along w/ a safe baseline jetting spec.
a dyno is only as useful as the knowledge & experience of the operator. i have participated in countless tuning sessions @ dynotech tuning various makes & models of sleds. i have yet to see a situation where the dyno tune was not close to the field tune.
bob
srx154 wanted info on tuning a 835 srx snowmobile engine...not a nhra top fuel engine. a rad gauge & bendalight is all he needs along w/ a safe baseline jetting spec.
a dyno is only as useful as the knowledge & experience of the operator. i have participated in countless tuning sessions @ dynotech tuning various makes & models of sleds. i have yet to see a situation where the dyno tune was not close to the field tune.
bob