need to reduce top speed, HELP!!

[swissdoo]

hi helpers,


my problem made short, to pass the noise emmision test over here in switzerland i have to reduce my top-speed from my challenger 230 SE round 10-15mph.

this has to be done in the pump, i am not allowed to lower the revs.. they check that before the test begins..

my main problem is the water sound, we have done several tests and the engine sound is now ok, after having the engines out to dampen the engine room.. ;(

so what will give me the best result? change the nozzels or sand out the ware rings? i like the ware ring way because its very easy to change the modd back to stock after the test. dose anyone have any experience how much i will have to sand out to get my 10-15mph loss??

or any other ideas?? thanks so much for any help , patrick

 

[kustomkarl]

I would think the best way would be to put a stop on the throttle linkage to prevent it from going to full throttle. If you remove material from the wear ring it will rev high , but have very poor performance. You will loose jet pump pressure and not really be able to regulate it as far as how much material in the wear ring you remove. to loose just 10-15 mph...you might not even go 15 mph top end if you remove too much. Maybe buy a different impeller to reduce top end?

Karl

 

[swissdoo]

hi karl,

thx for your help.

i cant block the throttle, the guy who dose the noise test drives himself and before the test they check with a external knock sensor the rpm.. so no cheeting.. :boxing_smiley:

i have to reach the rpm max on the test drive.

i have no experience with the impellers, would there be a impeller on the market that will loose that much in top speed?

yes, this would be the best way to go... i just have to keep the rpms up..

thanks, patrick

 

[kustomkarl]

If you go to a less degree in pitch, you will have lots of bottom end pulling power and loose top speed as a trade off. Contact solas.com and inquire about the different pitches available. I think they ship everywhere too.

Karl

 

[Bdt1967]

Sounds like you need to move.

 

[swissdoo]

nice one, :hurray:

in fact, i drive your cars, your boats and even my RV is not from here :rofl:

greez

 

[global1]

you might try some pump nozzle wedge's to point the pump flow downward and bring the bow down.also larger diameter nozzle's would slow you down.

 

[Dr Honda]

Get yourself an extra pump nozzle from eBay. Then get your local machine shop open it up as far as they can. The result will be lower internal nozzle pressure and exit velocity… but you will increase the volume. This will actually allow the boat to accelerate faster, and pull a heavier load… but it will scrub off speed. If you can open the nozzle by 8~10mm… you should be able to drop the speed by 10mph.

Actually… there may be a way to cheat. If this is on the 510 boat in your signature… loosen up one of one intake lines… or add a “T” fitting somewhere… where you can hide it… and bleed off some of the boost pressure. That in turn will run the boat slower.

Now that I think about it… since you have a supercharged boat… opening up the pump will just let it bounce off the rev limiter since you will lose pump loading. I would try to scrub boost pressure somehow.

Good luck

 

[robertm]

How about lowering the fuel octane?

 

[timmyboy76]

scratch....$$$

what about a different mechanic?

I can get a skateboard smogged....

 

[swissdoo]

hey tony,

nice idea, i will get my dealer to try that on a PWC he has in the shop...

i`m just wondering if that would not show a fault on the computer? less air going in the engine than through the supercharger?

and, will my engine still rev up 8000rpm, even with less air?

i am just thinking of the commen supercharger issue, much less pressure from the supercharger and the revs only go to 5000. ( had that on my speedster 200..)

thanks for your help!!

 

[swissdoo]

tony, just a new thought,

the air intake idea will not help in my situation, i have to lower the speed but keep the 8000 rpm. and if i dont change anything in the pump and still have my 8000rpm i wount loose any speed...

so i will have to go the pump way... i will try to get 2 nozzels to play arround with...

any idea what will happen if i block off the intakte grate like 10%?

thanks man, patrick

 

[RichC]

Looking for suggestions on how to lose some top speed. Wow. Seems to be kinda contrary to everything I've ever read in this forum.

Best of luck to you.

 

[robertm]

If you lower the Btus of the fuel the engines knock sensors will detect it. Power output will be lower but rpms will remain the same. Top speed will def be reduced.

 

[Dr Honda]

If you lower the Btus of the fuel the engines knock sensors will detect it. Power output will be lower but rpms will remain the same. Top speed will def be reduced.

You can’t count on the computer to lower the timing, and richen up the fuel to compensate for using the wrong fuel. Besides… with a supercharged engine… if you can hear knocking… you are at the point of burning holes in the pistons, and smashing crank and con rod bearings. It’s a VERY bad idea. (not bashing… just saying the truth)

Oh… and lower octane doesn’t nessaseraly reflect the fuels BTU’s.

Swis….

If you lose boost… yes, in turn you will lose RPM’s. BUT… if the inspector can see that the throttle plate is opening fully… but in the water it only runs up to say… 5500 RPM… who’s to say that isn’t what it is suppose to do?? Also… I’m not saying to lose all the boost pressure… just enough to drop it 10mph, and it will run at 7000 rpm.

I don’t think you will trip a check engine light with lower boost. People on this board have slipping washers… and they don’t get a check engine. They only know that the boat/PWC isn’t going full speed.

Closing off the intake a little would work too. If you pick up a few used intake grates… you could have someone weld on a flat plate. Heck… you can have them weld on a plate going straight down a few inches. That may put enough drag on the boat to scrub 10mph. (just a thought)

 

[Gunsrunner]

Here is my 2 bob!!
Repitch your impellor, this will cost you nothing and you can return it to original once your done!!
all the info you will need is on another site, sorry it's from another place but!!
google repitching seadoo impellor.

 

[bigJake]

Hey Tony, I notice you are from Pittsburgh too. Anywhere near Peters Twp?
Where do you ride?

 

[06challenger]

hey

i dont know about you guys but this problem sounds crazzzy! lol.. the pics look amazing swiss so i dont see you moving! lol... down here in South Carolina i see people doing over a 100 mph screaming accross the water! its kinda nuts! but theres not too many laws that say you cant! you can ever drink beer wile you drive your boat! your just not suppose do be drunk! lol... everything that i have been reading i think may end up hurting your boat! what if you kinda blocked your intake grate a little??? mabe if you can fab up a piece of metal to clamp on your intake greate to cut down the water flow... make it look stock and tell your mechanic you purchased this of the internet and thats what its made for? that might work.. and you can do a little trial and error on how big to make the cover to see how much water you need blocked??? it may work.... :cheers: good luck brother!