I have a 2001 seadoo xp with a 951, the ski is all stock besides the carbs having the assorters and a set of beach house sponsons, i just replaced the wear ring and the oil in the jet pump,pritty much the ski is a blast and on flats i can get it up to 67 mph topped out on 93 pump gas, what simple bolt ons can i add to reach speeds just over 70mph without loosing my hole shot acceleration?
-
This site contains eBay affiliate links for which Sea-Doo Forum may be compensated.
2001 xp looking for more top end speed...
- Thread starter Seadoo-XP
- Start date
- Status
JJinSC
Well-Known Member
Correct me if I am wrong, cause I am still learning, but considering the stock 951 engine and knowing what I have learned regarding fuel, octane and the purpose of changing the octane in fuel. Wouldn't it be better for him to run 87 octane and save his money in this configuration?
SabrToothSqrl
Well-Known Member
87 does provide more power per gallon... in thermal units anyway. only when you have high compression does higher octane = more power. (because lower octane will cause uncontrolled ignition)
my stock 2002 XP does a GPS'd 67 MPH with a solas concord... and the hole shot is near breakneck. LOVE IT.
is this a GPS speedo or the paddle wheel? because my paddle wheel is 2-3 MPH off at those speeds... and is this the average of up and down river or lake? what was air temp? water temp? cold water makes mine SO much faster...
http://en.wikipedia.org/wiki/Octane_rating#Effects_of_octane_rating
but let's not get into that, now... let's get his and MY XP going faster... or mine going at all, it needs a rebuild
what's your compression now? COLD?
my stock 2002 XP does a GPS'd 67 MPH with a solas concord... and the hole shot is near breakneck. LOVE IT.
is this a GPS speedo or the paddle wheel? because my paddle wheel is 2-3 MPH off at those speeds... and is this the average of up and down river or lake? what was air temp? water temp? cold water makes mine SO much faster...
http://en.wikipedia.org/wiki/Octane_rating#Effects_of_octane_rating
but let's not get into that, now... let's get his and MY XP going faster... or mine going at all, it needs a rebuild
what's your compression now? COLD?
Last edited by a moderator:
Dr Honda
Well-Known Member
Yes to both. Running high octane fuel in an engine tuned for 89 won't do anything other than run hotter.
As SaberTooth touched on.... higher octane will support more power... but it doesn't MAKE more power on it's own.
Basically... the higher the "Octane"... the slower the fuel burns. SO... as an extreme example... putting 110 oct "Race fuel" in an engine designed to burn 89 will probably make it loos RPM, and it will melt the piston crowns at the exhaust port. The reason is... that fuel is burning significantly slower, and is only partly burnt as the exhaust port opens. When that happens... the burning fuel rushes out the port, and focuses the heat at the crown. (The squish band in our engine can only cool the crowns under normal conditions) Also... since the fuel is burning out the port... you aren't getting it's full "Push" on the piston. (wasted power)
NOW... if you properly raise the static compression to 180 psi... you can cause the "Race Fuel" to burn at a higher rate, and completed it's burn cycle before the exhaust port opens.
So what can we take from this???
The Race fuel, on it's own, didn't make more power... but the higher compression is going to give a harder push on the piston. (The compression is what made more power, but regular fuel wont' support 180 psi static)
Sorry for that....
I guess the real question is what Saber tooth was asking. How did you measure the speed, and in what condition is your engine? If you have a 9 year old factory engine... it may not live very long if you mod it.
As SaberTooth touched on.... higher octane will support more power... but it doesn't MAKE more power on it's own.
Basically... the higher the "Octane"... the slower the fuel burns. SO... as an extreme example... putting 110 oct "Race fuel" in an engine designed to burn 89 will probably make it loos RPM, and it will melt the piston crowns at the exhaust port. The reason is... that fuel is burning significantly slower, and is only partly burnt as the exhaust port opens. When that happens... the burning fuel rushes out the port, and focuses the heat at the crown. (The squish band in our engine can only cool the crowns under normal conditions) Also... since the fuel is burning out the port... you aren't getting it's full "Push" on the piston. (wasted power)
NOW... if you properly raise the static compression to 180 psi... you can cause the "Race Fuel" to burn at a higher rate, and completed it's burn cycle before the exhaust port opens.
So what can we take from this???
The Race fuel, on it's own, didn't make more power... but the higher compression is going to give a harder push on the piston. (The compression is what made more power, but regular fuel wont' support 180 psi static)
Sorry for that....
I guess the real question is what Saber tooth was asking. How did you measure the speed, and in what condition is your engine? If you have a 9 year old factory engine... it may not live very long if you mod it.
Last edited by a moderator:
SabrToothSqrl
Well-Known Member
Tuned for 89?
My manual says 87 is fine in the carb 951 ski...
we used to run 89 in my old ski, and it went 300 hours before a rebuild...
should I switch to 89? a few cents a gallon is cheaper than a rebuild!!!
My manual says 87 is fine in the carb 951 ski...
we used to run 89 in my old ski, and it went 300 hours before a rebuild...
should I switch to 89? a few cents a gallon is cheaper than a rebuild!!!
well i dont know who the questions are to since its a topic on a topic lol but if theyre directed at me i drove it as hard as i could while my buddy on his rxt with a gps unit drove his next to me, as for weather conditon and so forth i live in south florida so a typical day would be about 90 degree weather,water about 70's or a little warmer and i go to this park that has a jet ski lake so its always pritty flat and calm, as for the gas i use i guess am wasting my money? lol being an automtive mechanic am a firm believer about the better the gas the better your engine performs and lasts longer but i guess when aplying that to the 2 strokes its crap... lol would a intake grate help out with speed or is that for pick up? and where can i find a decent race pipe guys? i dont want to do anything to the engine, i want to keep it stock btw
SabrToothSqrl
Well-Known Member
a scoop intake grate will scrub top speed as it causes drag...
- Status
