Reply With Quotewhos the new writer for ***boat?
TIMINATOR Now he'll have to kill me.
whos the new writer for ***boat?
whos the new writer for ***boat?
TIMINATOR Now he'll have to kill me.
With the delay before hit, the impeller size controls the launch and under those particular circumstances WITH YOUR combination I'm sure it does what you say. If you run with no delay the results will be different, and as normally expected. TIMINATOR
Define "normally expected". I read this a dozen times Timo, and I still can't understand what you're trying to say here. :idea:
I just read the nitrous article in the new ***boat. Did anyone catch the paragraph that said to match your impeller to the engines hp with the nitrous. It stated that nitrous would require on cut larger impeller. Im not understanding that. It has always been my understanding that you want to cut your impeller to allow the engine to run at its peak hp. If this is done right, when you add nitrous it will just allow the engine to spin it even faster. Why would you want to go to a larger impeller?
As usual, it's another magazine article making a general statement that they just shouldn't make. There's just too many variables involved to just say "with nitrous you need a bigger impeller". In some instances it may well be true, but as in Garry's examples, it's not. General statements such as these, IMO, are just a way of saying, "sorry, we really don't have time or space to give you the correct info, so we'll just fill the page here, adn call it good".
Here's a visual...
http://members.cox.net/lvjetboy/N2O.jpg
An engine similar to Squitchas Ford.
I'd agree with Sleek, Gugs, Steel and Duane. Power to the impeller is key. Delay before it hits is a transient or pump loading issue. Once loaded becomes an impeller to engine power matching issue.
Let's assume DTD best guess. One thing with DTD and no dyno test. DTD is better than nothing. N20 means more power at the same rpm. Guess what? Peak doesn't shift and neither does the impeller. Yet a Berk A matched to max power may fall off the engine power curve on the gas. See the chart above.
Is that a big deal? Maybe not in many or most applications. Is that a consideration for those trying to get that last mph or et? Maybe so.
If you look at the engine power curve, one cut size may mean more or less power to the impeller depending on how that power is generated. NOS? Cam? How do engine mods shift max power and so on...
Impeller efficiency is also important. This is an issue not well understood by most jet boaters or mentioned by mfgs. Mfgs don't have the resouces or aren't willing to commit those to testing and mapping pump efficiency curves. Yet impeller cut size will shift the best engine match point depending on how well that impeller cut converts engine power to thrust.
Oh well.
jer
I have a graph here almost identical to the one LV posted. It was cut. I have no control over what ends up in the mag, I submit more than they need, they use what they choose. The choice was made not to use a color graph (not by me), a B&W graph doesn't come across as well in print. LV is exactly correct, and his chart shows WHAT IS EXPECTED, and WHY. I have been useing N2o since I was 23 or so, I am 53 now, do the math. I like to think that I have a clue. In case you haven't figured it out yet, the lead photo is of my 14/71 atop my rollered, intercooled 565" 25 Daytona. It runs over 120+ without the bottle. The setup is adjustable from 140 to 600+ HP. Gugs has been around here for quite a while and obviously can keep a secret, and the man is a sponge, he soaks up any info in the area! I chose not to announce my affiliation (since October 2005),because there are a few confrontational types that like to argue, I do not. There is a lot of good info in the articles, try not to get too caught up in who presented it. TIMINATOR :rollside: P.S. I get ideas for articles based on what I read on these threads. If I feel there is a demand, I will try to fill it. Feel free to post or P.M. me.
In case anybody remembers my 21 Daytona jet; the engine was severely over cammed, on purpose. It turned 5800 rpm on the motor (AA impeller and inducer), the power peak was 6400 rpm, I just added more n2o until it ran at the HP peak on the sauce. That way I gained the N2o hp and the hp difference between the non-bottle rpm and the bottled peak. A 17+ mph gain for a 250 shot! AND a nice, low cruise rpm too! I also ran that 9.5 compression motor on REGULAR 87 octane PUMP GAS! Even on the sauce! With a mechanical fuel pump. When I sold the boat, I kept the motor...... Hmmmmm what do I put it in next? TIMINATOR
Okay.. the reason for the delay is to keep the boat consistent leaving the line by decreasing the possibility of slipping the pump with the extra HP at the hit. IT HAS ABSOLUTELY NOTHING TO DO WITH THE PERFORMANCE GAINS DOWN THE TRACK. In my opinion, the reason for the idea behind the bigger impeller is to simply not over rev the engine. It's all in what RPM you are geared to run. In most lake boats, the owners probably don't want to turn the motors much more than ,say 6000-6500 RPM and going with the bigger impeller with the nitrous will help keep it there. My application is for pure performance in a full fledged drag boat that I don't mind turning the motor to 8000 RPM. I've been there, done it, and got the tee shirt. As far as running without the delay, assuming I wasn't worried about consistency, it would probably run faster, with the nitrous coming on earlier in the run. Keep in mind that I ran the delay with both impellers. But, as always, you should run it whatever way you like.
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