Is my fear justified?

[McDog]

I'm about to put a MSD Enhancer, a b-pipe, and a RIVA head with 35cc domes on my ski.

I do a lot of WOT runs to chase boats down on the small lake I live on. That's what you have to do when there is like 1 or 2 boats out on the whole 7 mile lake during the week (if you want any wakes to jump).

Would it be a good idea to crank the rev limiter back just a little from the 9000 limit on the Enhancer (like a 1/4 turn maybe)? If it's choppy my pump is sucking air half the time I'm at WOT. I really don't want to blow my engine but I don't want to sacrifice a lot of power either. Should I back off even more? Is my fear even justified?

 

[Sospikey]

What fuel are you running? There might be some danger with low octane, higher compression and MSD along with extended WOT. What about running on the safer side, trying to keep the limiter just above stock?

 

[McDog]

93 octane, what is the stock limit?

 

[Sospikey]

Not sure, check at GroupK.com.

 

[sflsurfrider]

i crank the pot all the way up and use the throttle as the rev limiter.

 

[Foximus]

what do 35cc domes net in compression? My 701 has a triton eng. head on it and nets 200 psi. This is probably a little higher than I would like, 180 seems more desirable. I use 93, 50:1, and a riva red which will hopefully soon be a B pipe. Again i do the same thing... occasional wot to chase down, but usually not so much. Should I bother going to MSD or keep the stock CDI?

 

[sflsurfrider]

stock cdi rev limiters are just to low, even for a stock engine, IMO.

msd.

 

[McDog]

35cc domes net about 185psi

 

[hangtime]

185 is the limit for pump gas .
I have an ADA at 185 with B pipe, prop etc and use 93 octane at 40/1 mix all the time .

Your supposed to be safe at 185 compression with 93 octane for WOT runs :fing02:

 

[McDog]

185 is the limit for pump gas .
I have an ADA at 185 with B pipe, prop etc and use 93 octane at 40/1 mix all the time .

Your supposed to be safe at 185 compression with 93 octane for WOT runs :fing02:

What about the rpm limit?

 

[Foximus]

185 is the limit for pump gas .
I have an ADA at 185 with B pipe, prop etc and use 93 octane at 40/1 mix all the time .

Your supposed to be safe at 185 compression with 93 octane for WOT runs :fing02:

hrmm.. damn. looks like stock CDI is stayin in for sure. I dont get any detonation either. Wonder why.

 

[hangtime]

What about the rpm limit?

I have an MSD set all the way up but quite frankly I dont do many WOT runs for more than 5 seconds or so since I only ride surf .:wink1:

 

[Mile9c1]

I don't think it's worth worrying about.

 

[McDog]

Thanks guys. Just to confirm, you don't think WOT runs for up to 5 minutes with a rev limit at 9000 rpms is likely to damage the engine?

 

[Foximus]

5 minutes is a long time in 9000rpm world...

 

[Superjetjim]

Detonation kills 2 x strokes with WOT runs.. the MSD Enhancer retards the timing at the top end (unlike stock CDI) and is actually safer! The MSD gains come in bottom end ´Hit´where it advances the timing compared to stock CDI.

In reality I can´t see you holding WOT for 5 mins..
You´ll be fine dude - ride it like a rental

 

[sjetrider]

You will be fine at 9000 rpm setting with that set up. I ran that exact set up w/ 44 mm carbs and a billet alum flywheel for years and NEVER detinated, the cylender ran 9 years on its original bore.

 

[Mark44]

You will be fine I run 180 on compression and the MSD with 2mm advanced timing and have no problems just make sure you run at least 92 octane.

Mark44

 

[sflsurfrider]

just because your limit is set to 9k, it doesnt mean your motor is actually capable of spinning 9k on a WOT run. if your pump is hooked to the water, its going to take some mad modification to hit 9k.

many ltd skis dont even hit the stock rev limit unless their pumps come out of the water.

 

[Big Kahuna]

Thanks guys. Just to confirm, you don't think WOT runs for up to 5 minutes with a rev limit at 9000 rpms is likely to damage the engine?

no because your ski is not going to be running 9000 rpms.