Top speed prediction

[Baja 252]

Finishing up final tuning on our 08 SJ makeover. Just a lake ski to play with, jump wakes and race around with friends. Runs great so far, getting ready to GPS it tomorrow.

Curious what people think our top speed will be.

Fresh 701
rec (mild) porting of cylinder and case
ADA head, 35cc 180psi 91 octane
MSD Enhancer
lightened stock flywheel
B pipe, Mod chamber, ported manifold & opened up to 50mm.
Modified stock waterbox
Stock 38mm carbs with no chokes and Group K's true bore mod
VForce 2 reeds
ADA couplers
stock pump, cleaned up with dremel
Hooker 10/16
ProWatercraft sponsons
Works grate
Riva rideplate

 

[Vumad]

Do you have a tach? Let us know your RPM too. If you don't have one, Hardline tach / hour meter are inexpensive and work well.

 

[MTRHEAD]

Depends on at least 4 things
#1 your weight
#2 your nozzle size
#3 fuel? based on #2? 7200 rpm is about max you'll run with MSD in stock position and that PSI At 180 psi it doesn't have much more duration than oem so i doubt you'll see high side of 7100. you will need a wide port and good transfers to pull a hooker that high with this setup, but then again. Weight and nozzle?
#4. How far did you modify the box. (Hint your going to go slower)

You will go anywhere from 52.5-55.5 depending on those 4 questions

 

[Baja 252]

Weight - 170
Stock 08 nozzles, not sure of size.
Testing will be done with 1/2 tank, say 2.5 gal
Rpm now is only 7000, I've been focused on getting it broke in and carbs, pipe and FCV adjusted.
Engine builder says my target should be 7300, so I will need a prop/nozzle changes to get some more RPM.
Can't remember the exact size or # of holes in the water box, Judge did it.

I'm just curious what speed people thought I'd hit.

 

[Vumad]

I get 46mph @ 7200 rpm with a 13/17 concord. Similar setup but no porting. I'm sure a little more tuning could be done but I never got to compete so I didn't try to get anything extra out of the top.

Also wonder if my GPS is off because the Xmetal 900SS I clocked was only at like 54 and it kept up with 1100 SXR.

 

[Baja 252]

52.8 mph. I will need to re-pitch to get up to 7250 - 7300

 

[Quinc]

I just switched from a 10/16 back to a Solas 14.5/18 in my blaster and the Solas keeps pulling vs the 10/16 flattens out pretty quick. Before you make any changes to your impeller make sure you have you bpipe tuned correctly following the factory pipe tuning instructions.

 

[Baja 252]

That's a good point. I'm still at the Factory Pipe recommended starting point of 3/4's out on the bottom and the other two closed. Pipe gets hot, but won't sizzle water next to the coupler like it's supposed too. That bottom screw is so hard to adjust in the hull.

Think that will give me 100-200rpm on top?

 

[Quinc]

That's a good point. I'm still at the Factory Pipe recommended starting point of 3/4's out on the bottom and the other two closed. Pipe gets hot, but won't sizzle water next to the coupler like it's supposed too. That bottom screw is so hard to adjust in the hull.

Think that will give me 100-200rpm on top?

Easy enough to find out.

 

[MTRHEAD]

52.8 mph. I will need to re-pitch to get up to 7250 - 7300

try an OEM waterbox without changing anything ....you will be surprised

 

[Vumad]

I just switched from a 10/16 back to a Solas 14.5/18 in my blaster and the Solas keeps pulling vs the 10/16 flattens out pretty quick. Before you make any changes to your impeller make sure you have you bpipe tuned correctly following the factory pipe tuning instructions.

What setup do you have? I have a 13/17 concord per the impros solas application chart and it seems right and runs 7200 rpm. I have pipe, head, flywheel. Maybe my GPS is right with a lower prop.

 

[Baja 252]

try an OEM waterbox without changing anything ....you will be surprised

Do you think with the stock water box I would loose much low end? Even though I started this thread about my top speed, I didn't build this for top speed. Low end is what I use most and is what helps me launch off waves.

 

[Quinc]

What setup do you have? I have a 13/17 concord per the impros solas application chart and it seems right and runs 7200 rpm. I have pipe, head, flywheel. Maybe my GPS is right with a lower prop.

754cc 62t/61x freestyle ported coffman pipe, 175psi, dual 38s, boyesen rad valves, lightened flywheel, enhancer, blueprinted pump. more info in my sig.

I swapped the 10/16 into my freeride superjet 61x, bpipe octane chamber, single 46, boyesen carbon reeds, 170psi, cpt porting and at full throttle across the lake she is bouncing off the stock 61x rev limiter.

 

[Quinc]

Do you think with the stock water box I would loose much low end? Even though I started this thread about my top speed, I didn't build this for top speed. Low end is what I use most and is what helps me launch off waves.

limit the water going to the stinger with a T and flow control valve. Also I believe closing the bottom screw on the headpipe and opening the top screw will help with low end.

There is a horsepower/rpm chart that factory put out showing the bpipe makes it peak hp at 6700rpms and power starts to fall off after that.

 

[Vumad]

754cc 62t/61x freestyle ported coffman pipe, 175psi, dual 38s, boyesen rad valves, lightened flywheel, enhancer, blueprinted pump. more info in my sig.

I swapped the 10/16 into my freeride superjet 61x, bpipe octane chamber, single 46, boyesen carbon reeds, 170psi, cpt porting and at full throttle across the lake she is bouncing off the stock 61x rev limiter.

Makes sense then. You can turn a higher prop to the same RPM. I have OEM carbs, glass dual stage reeds, no porting. Rest is similar except I have a mod chamber which I would assume has no significant impact.

 

[MTRHEAD]

Do you think with the stock water box I would loose much low end? Even though I started this thread about my top speed, I didn't build this for top speed. Low end is what I use most and is what helps me launch off waves.

Your post was about top speed. Oem box works well with anything up to 800cc and 62-64 mph in a Superjet. I will admit an opened up box will hit a touch harder or a gp760/raider 701 box. But at performance expense in upper r's. Especially with your mild setup.

 

[Baja 252]

Thanks MTRHEAD.