some boost questions?

[turbocat]

Well I took the plunge and picked up an 08 nytro with a mcx 305 kit in it.Now thats 305 using 114 at 18psi. How much boost can i run safely with 100 octane as i can get it cheap. thanks

 

[overkill131313]

I have the same question but for a apex! was told 50/50 avy/c12 at 17-18

can some one give a chart on what to mix for what PSI? I dont want to break the bank but dont want to hurt the engine! sled pulls every hill at 12 psi but is more fun at 17 psi lol.

 

[NM]

Well I took the plunge and picked up an 08 nytro with a mcx 305 kit in it.Now thats 305 using 114 at 18psi. How much boost can i run safely with 100 octane as i can get it cheap. thanks

What kind of fuel? Av or race gas? What elevation do you ride? I would say straight av you could run 18 lbs. I am thinking you have a head shim motor? You could probably run 15-16 lbs on straight premium at over 5000 ft.

 

[INSTGUY]

I've got a 240hp MCX (head shim)set to 14 psi....hardly ever get there...usually at 3/4 throttle and 80mph @ 10-12 psi...takes any chute...very reliable on premium....if I upgrade I need to run 50/50 premium-c12, 10-14 psi boost seems to be the most reliable combination

 

[turbocat]

Its is 100octane av gas at over 5000ft.18 psi seems like a little much without 114.but u probly know better as 4 stroke turbo's is new to me.Have a boosted m8 and would never go that high without mass detonation wit that fuel.

 

[SLY]

I have been running run 17psi on 100ll for the last 3 seasons on an MCX Nytro at 1900-7500 ft. I have always figured it was approx 270hp though, that is what MCX advertise it as. There are a few guys running 91 octane at the higher elevations. 114 sounds like too much octane, as long as you have lowered compression. Running higher octane fuel than required robs horsepower and in my experience causes more frequent exhaust cracks, which I believe are caused by the higher temps of the slower burning fuel. Just my opinion though.

 

[Prairie Dog]

I ran 17lbs on my MCX Apex using straight AV gas.

Now running 14lbs on Alpine Nytro mixing premium and C12 50/50 with no problems. I was told to run 16lbs I'd have to run straight C12.

Not sure how high I could go with AV gas.

 

[tranquillicer]

I think every kit is different. I ran 91 with some av gas last year with PL stage2@ up to 13lbs and this year I ran 91 with PL stage3@ over 16lbs (from time to time) and even 18lbs. Recomendations are for premium up to 16lbs. Had some c12 last trip out west but never went above 16lbs cause I really didn't need it.

 

[turbocat]

So to be safe should probly run c12 or 14 if i want to run in the 18psi range?

 

[tranquillicer]

So to be safe should probly run c12 or 14 if i want to run in the 18psi range?

I would say yes to that.I would if I was running 18lbs on my set up consistantly

 

[Wapbuck]

All I can say is what I have been doing with my Apex. I only run 100LL as we have a tank for our float plane. I have a Boondocker Stage 1 kit with a head spacer. I have had no problems running 18 PSI of boost anywhere ( 1500 - 9000 ft elevation ) and have accumulated around 5000km on my sled since I installed the turbo. It still seems to run well.

Is this right or wrong? I don't know but my sled is still running and I would depend on it to go on a 1000km trip tomorrow if there was still snow around here. If the motor goes away, I just get to improve it as it doesn't owe me a thing since it has lasted longer than any 2 stroke I have ever owned!!

 

[shawnmcgr]

Boost calc. I've found useful.

TY 4 Stroke - Totallyamaha :: View topic - calculator for hp with altitude, octane, c/r, and boost