mnm99
Well-Known Member
Yea I know, It's never good enough...lol. Winter is here and I want to play again.
A few years ago I had my props re-pitched because I was above my WOT range of 4200-4600. I was at 4730 so I ended up going from a 18x21 with a .125 cup to a 18x22 with a .075 cup. After that I was at 4620 for some reason and gained like 3mph. So last year I had them go over the props again and add a .250 cup. My speed right now is 28 to 28.5 mph at 3450rpm and a WOT of 38.5 at 4560-80 rpm. I called ACME props and talked to him for a while. He suggested there 18x23 with a .043 cup. He told me it would gain around 1 mph on the top end at 4450rpm and .75 mph at cruise. Well if you do the math, there is no way i'm spending $3500 for that. So I'm thinking...safe RPM range is 4200-4600. What's stopping me to add another 1 degree of pitch and take out .125 cup or so. I would drop like 150 rpm bringing me to around 4400 rpm. I should gain better mph at cruise. I know optimal rpm is 4600, but if the range is 4200 to 4600 I should be good? right? I'm not sure how my gas mileage will do also after? Right now I'm burning 32GPH right at 28-28.5 mph. Here are some scenarios.
Current =WOT 4580 rpm with 22 pitch prop .15.26 slip at 38.5 mph
Proposed =WOT 4400 rpm with 23 pitch prop .16.73 slip at 38 mph
Proposed =WOT 4400 rpm with 23 pitch prop .15.63 slip at 38.5 mph
Proposed =WOT 4400 rpm with 23 pitch prop .14.54 slip at 39 mph
Proposed =WOT 4400 rpm with 23 pitch prop .13.44 slip at 39.5 mph
Proposed =WOT 4400 rpm with 23 pitch prop .12.35 slip at 38.5 mph
Current =CRUISE 3450 rpm with 22 pitch prop .18.19 slip at 28 mph
Proposed =CRUISE 3450 rpm with 23 pitch prop .21.74 slip at 28 mph
Proposed =CRUISE 3450 rpm with 23 pitch prop .20.35 slip at 28.5 mph
Proposed =CRUISE 3450 rpm with 23 pitch prop .18.95 slip at 29 mph
Proposed =CRUISE 3450 rpm with 23 pitch prop .17.55 slip at 29.5 mph
Proposed =CRUISE 3450 rpm with 23 pitch prop .16.15 slip at 30 mph
A few years ago I had my props re-pitched because I was above my WOT range of 4200-4600. I was at 4730 so I ended up going from a 18x21 with a .125 cup to a 18x22 with a .075 cup. After that I was at 4620 for some reason and gained like 3mph. So last year I had them go over the props again and add a .250 cup. My speed right now is 28 to 28.5 mph at 3450rpm and a WOT of 38.5 at 4560-80 rpm. I called ACME props and talked to him for a while. He suggested there 18x23 with a .043 cup. He told me it would gain around 1 mph on the top end at 4450rpm and .75 mph at cruise. Well if you do the math, there is no way i'm spending $3500 for that. So I'm thinking...safe RPM range is 4200-4600. What's stopping me to add another 1 degree of pitch and take out .125 cup or so. I would drop like 150 rpm bringing me to around 4400 rpm. I should gain better mph at cruise. I know optimal rpm is 4600, but if the range is 4200 to 4600 I should be good? right? I'm not sure how my gas mileage will do also after? Right now I'm burning 32GPH right at 28-28.5 mph. Here are some scenarios.
Current =WOT 4580 rpm with 22 pitch prop .15.26 slip at 38.5 mph
Proposed =WOT 4400 rpm with 23 pitch prop .16.73 slip at 38 mph
Proposed =WOT 4400 rpm with 23 pitch prop .15.63 slip at 38.5 mph
Proposed =WOT 4400 rpm with 23 pitch prop .14.54 slip at 39 mph
Proposed =WOT 4400 rpm with 23 pitch prop .13.44 slip at 39.5 mph
Proposed =WOT 4400 rpm with 23 pitch prop .12.35 slip at 38.5 mph
Current =CRUISE 3450 rpm with 22 pitch prop .18.19 slip at 28 mph
Proposed =CRUISE 3450 rpm with 23 pitch prop .21.74 slip at 28 mph
Proposed =CRUISE 3450 rpm with 23 pitch prop .20.35 slip at 28.5 mph
Proposed =CRUISE 3450 rpm with 23 pitch prop .18.95 slip at 29 mph
Proposed =CRUISE 3450 rpm with 23 pitch prop .17.55 slip at 29.5 mph
Proposed =CRUISE 3450 rpm with 23 pitch prop .16.15 slip at 30 mph