rpm limiter on a blower

[steve@kps]

Is it possible to put an rpm limiter on a blower motor? If so, how to instal w/out hurting parts?
thanks for the advice.
This is a 454 w/ a B&M megablower.

[steve@kps]

i should be picking it up tomorrow. I do have some pics that we took of the boat about 1/2 way through the restoration. I'll try to e-mail one to ya. I talked to the guy last week. I asked him if he'd go 100mph in it. He said hell i'd go 130mph, no problem.. That made me feel good. He only added about 20 pounds to the boat.
steve g.

[steve@kps]

that's funny..
He re-inforced w/ balsa wood, just like he uses in his boats. The glass is that new hi-tech shit(i don't know what's called). Most of the weight is from a larger bulk head, and re-inforced flooring. The bottom job looks kick-ass. We did away w/ the top hatch, because it would have been to hard to keep the lines, plus it's stronger now. :D

[Infomaniac]

Steve: Who fixed that thing?

[steve@kps]

Hey infomaniac.
Wyatt @ Wyatts Performance Boats in Cushing is doing all the glass and some gelcoat work. He's been doing great job on it.

[Infomaniac]

Thats Cool,
I am building a 10-71 blown 540 for a guy that has one of Wyatt's 23' tunnels. We intend to make it the fastest one out there.

[steve@kps]

Info.
Wyatt does build some kickass boats. Man that blown 540 sounds cool.. Are you planning on running at Keystone very much? any pics of the motor?
BTW (little spam..lol) if you'll need a new prop, i'm closing out some of the new OFX 4 blades by Powertech.

[Infomaniac]

Steve,
The owner lives in Wagoner, so Ft. Gibson primarily. Just started on the engine. Plenty of pics as it progresses. Custom pistons will take a few more weeks. Rods showed up yesterday. Oliver makes some nice stuff.
One owner of another one of those boats said Hydromotive props work well on that hull for some reason. He will probably need a 32 pitch with the new engine.
[ December 06, 2002, 12:56 PM: Message edited by: Infomaniac ]

[steve@kps]

Sounds like good parts. I've been real successful w/ srp pistons,and eagle 3d rods on a Ohio crankshaft(internally balanced) in my dragster. Makes 814hp, and now have over 180 passes at 162mph. (7400r's)
Sounds like your motor will live a long time also.
Gibson is not far at all, we actually plan on goin into the river several times next year when the boat gets finished. I'll be looking forward to meeting you guys and drinking a cold w/ ya.
props, can't help ya there. throttle up props would be the place to go.

[steve@kps]

Just ran some numbers on that new combination.
5400 rpms = 120mph
6200 rpms = 138mph
That's with the gear ratio of 1.36 (is that correct?)
that's fast! I wanna ride :D

[Infomaniac]

Steve,
He has a 1.5 ratio outdrive. until he trashes it anyway. One Wyatt boat owner says they really like prop RPM. We will probably run it up around 6,200 RPM. More if necessary to get into the 120's
The engine will be bullit proof, Dart Big M, Callies, Oliver, J&E, Dart Heads etc. Some day if he wants to put good gas in it and step the blower up, the engine will not be an issue.

[steve@kps]

Man, those are good parts. I wish you guys much success. Here's link to easily figure out the theoretical speed. Keep in touch. Call me anytime if you need some help.
:)
http://www.go-fast.com/Prop_Slip_Calculator.htm

[blowngas]

steve@kps:
Is it possible to put an rpm limiter on a blower motor? If so, how to instal w/out hurting parts?
thanks for the advice.
This is a 454 w/ a B&M megablower.Use a speed switch of some sort to kill the ignition---don't use any kind of a stutter box with a blower

[paradigm shift]

blowngas:
steve@kps:
Is it possible to put an rpm limiter on a blower motor? If so, how to instal w/out hurting parts?
thanks for the advice.
This is a 454 w/ a B&M megablower.Use a speed switch of some sort to kill the ignition---don't use any kind of a stutter box with a blowerJust curious why you recommend this method. I know several that run an MSD ignition myself included with a blower and have had no problem yet. Or do you not consider that a stutter box? Mine never really runs up against the rev limiter because I prop it not to. But it has hit it on occasion without banging the blower so far. I use a low RPM chip until I get some time on new motors so I can't get to crazy.

[DEL51]

blowngas:
steve@kps:
Is it possible to put an rpm limiter on a blower motor? If so, how to instal w/out hurting parts?
thanks for the advice.
This is a 454 w/ a B&M megablower.Use a speed switch of some sort to kill the ignition---don't use any kind of a stutter box with a blowerI used an Msd 6AL box for 5 years without causing a problem.Is a stutter box something different than the rev limiter on the Msd.The Msd is suppose to cause misfiring on different cylinders each cycle to prevent fuel loading.

[steve@kps]

Hey, thanks for helping on the rpm deal.
My only concern on overreving is the boat possibly going airborne in rough water, (blowing out the prop). I know lot's of people that run blowers on their race cars, and they will not run an rpm limiter. I wasn't sure if the little b&m blower would have the same effect on the engine.
When an engine (msd controlled) mis-fires to reduce rpms, then the other cylinders, and manifold fill w/ fuel, possibly popping the blower. AM I THINKING CORRECTLY ON THIS?

[flat broke]

Steve,
I think there needs to be a quick clarification on how the MSD rev limiters work. They DO NOT induce a missfire. What they do is sequentially let one cylinder go dead out of every complete combustion cycle. As an example, you trip the limiter at say 6krpm. The msd doesn't send spark on the first of 8 sparks, if that doesn't sufficiently lower the RPM, then the unit times it so that the second spark in a group of 8 sparks doesn't get sent, then the 3rd in the next cycle, then the 4th in the next cycle, so on and so fourth until the RPM drops below the limit point. Efectively you have a roving dead plug in the motor until you drop below your limit point.
The reason they do this is so that one cylinder doesn't load up with a bunch of extra fuel and foul the plug while you're up against the limiter. Bear in mind though that your valvetrain is still moving even when the cylinder goes dead on the plug; so you still expell the unburnt charge through the exhaust stroke. Once you fall back below the limit point the MSD stops witholding spark and lets all 8(assuming your running an 8 cylinder) fire in their normal manner.
The main point of this is that there isn't a missfire, just a plain ol miss. The worst case I could see from this would be a slightly rich condition in the effected cylinders on the next combustion cycle following a limited(dead plug) cycle.
Bottom line, go grab an MSD 6al, or any number of other boxes that run a quality limiter setup and enjoy.
I hope that helped,
Chris

[steve@kps]

chris, that's a killer explanation. I always knew that the msd cut out the cylinders like that, but honestly i forgot about the fuel being discharged by the valve train. On my car i do run a rich barrell valve to get the car to leave hard.
So, why do so many people "freak" while limiting w/ an msd w/ a blower motor? If the fuel is leaving the cylinder, then how could it "pop" a blower? Or does it :D
Can ya tell i'm bored today. Nothin' else to do, until the shop warms up.. Freakin' cold :mad:

[flat broke]

steve@kps:
chris, that's a killer explanation. I always knew that the msd cut out the cylinders like that, but honestly i forgot about the fuel being discharged by the valve train. On my car i do run a rich barrell valve to get the car to leave hard.
So, why do so many people "freak" while limiting w/ an msd w/ a blower motor? If the fuel is leaving the cylinder, then how could it "pop" a blower? Or does it :D
Can ya tell i'm bored today. Nothin' else to do, until the shop warms up.. Freakin' cold :mad: Steve,
Well, if the limiter truly did cause a "misfire" that would pop the blower. If for some reason spark were to be re-introduced to the distributor at the wrong time and managed to get to the plug at the wrong time, I can see a problem. But from my perspective, I don't see how it can happen if your ignition system is solid. Even if the MSD sent a charge to the distributor at the wrong time(I probably have better odds of being hit by a bus today) your timing would have to be off for the misfire to occur because even if the spark got to the cap, the rotor wouldn't send it do the plug if its in the wrong position.
Thats the best I can come up with. I'll be honest, I've never run a blower, so maybe there is something more to this scenario, but I highly doubt it. Getting spark to the plug is pretty straight forward, and unless you can somehow get it there at the wrong time, I don't think you're gonna pop the blower.
Chris

[flat broke]

I have a possibility for you Steve.
What if your combustion temp was high enough that because the charge wasn't lit when the plug went dead, when the piston comes up for the exhaust stroke, there is enough back pressure to cause just enough compression to detonate any unburned fuel and send the explosion back up the intake valve due to valve overlap.
Since most of the blower lore comes from ye' olden non intercooled days, that theory is somewhat plausible.
Just a thought,
Chris

[MikeF]

Chris, I think you might have a point there. If you are using a LOG type exhaust manifold, that unburned fuel might be lit and chase up an exhaust port and through the overlap period, into the manifold eek! :rolleyes: :D .

[steve@kps]

Chris, i never thought about that one. I like the idea of a kill switch of sorts.
Would it be possible to hook something up to the tachometer, that say, when it hits 6000 rpms. It will kill the engine? That may be a very safe alternative. BUT, would suck if i were in rough water! eek! .....
There has to be a better way of limiting this engine.
Anymore ideas?

[flat broke]

steve@kps:
Chris, i never thought about that one. I like the idea of a kill switch of sorts.
Would it be possible to hook something up to the tachometer, that say, when it hits 6000 rpms. It will kill the engine? That may be a very safe alternative. BUT, would suck if i were in rough water! eek! .....
There has to be a better way of limiting this engine.
Anymore ideas?Steve,
That is a very BAD idea. The reason being is that if you come down from 6k with either a prop or an impeller not spining, the boat is more than likely going to object violently to the idea. If you were haulin the bacon at say 5500RPM and were going 75-80mph, and then got a little air, the motor reves to 6k, then kills and you land with nothin spinin, you're going to get wet(hopefully thats all you'll get).
Really I don't see what the big deal would be if the blower did pop. I don't know what kind of blower you plan on running , but most of them have pressure bypasses on them. In the extremely rare event that for some odd reason the rev limiter did cause a hicup, the worst you'd have to do is replace the relief plate or re-set the plate/spring setup.
I say run the MSD limiter and don't worry about it. I was merely trying to come up with ways in which the scenario could arise. If your combustion chamber temp is hot enough to ignite the charge in the example before, you're running close to a predetonation scenario anyways and have more important issues to tend to.
Give the guys at Teaue, BDS, Clay Smith, etc a call and see what they say. I'd bet you'll be safe with a rev limiter.
Chris

[steve@kps]

"That is a very BAD idea. The reason being is that if you come down from 6k with either a prop or an impeller not spining, the boat is more than likely going to object violently to the idea. If you were haulin the bacon at say 5500RPM and were going 75-80mph, and then got a little air, the motor reves to 6k, then kills and you land with nothin spinin, you're going to get wet(hopefully thats all you'll get)." (quote by chris)
Chris, that's my point exactly..... I was only concerned w/ over reving the motor w/ no high speed limiter. I'm a good enough driver(i think.lol) to handle this, but there will be 1 or 2 others driving the boat occasionally. I'm more worried about them overreving the engine. I'm just trying to save parts.
Thanks for chatting....
I'll stick w/ the limiter and just have some fun.
[ December 09, 2002, 02:44 PM: Message edited by: steve@kps ]

[Infomaniac]

Steve,
Buy an MSD and keep the RPM modules yourself. Be selective on which one is in when you drive and when someone else drives.
[ December 09, 2002, 02:52 PM: Message edited by: Infomaniac ]

[flat broke]

Infomaniac:
Steve,
Buy an MSD and keep the RPM modules yourself. Be selective on which one is in when you drive and when someone else drives.If you want to get really crazy, you could do something that Low River had talked about when we were out at Ming a while back. Install 2 ignition switches, and 2 MSDs. One setup for you, and one for wife/friends/etc. The wifey key is limited to say 4k, while yours is good to whatever you're comfy with :D
A little on the overkill side, but at least no one will feel bad from you having to go to the back of the boat and tinker before they can drive.
Chris

[steve@kps]

Thanks, INFO.....i have a ton of msd chips. I use them in the dragster.. You guys have helped out lot's i appreciate it.
steve g.

[Infomaniac]

Steve,
Your boat is finished? Wyatt has called for Randy's boat to do his fuel tank installation. Getting ready for the blown 540. Got to have enough fuel flow. He is running out of fuel now with a procharged 496.

[steve@kps]

Damn, that's weird.....LOL....you know about it being done before me..LOL.
I can't wait..............HEY, I'M OFFICIALLY A HOT BOATER!!!!!!!!!!!!!!!!!!! :D :D
my partner just talked to Wyatt. The gelcoat went on this morning, but they found a spot by where the top hatch used to be that will need some body work to smooth out. Should be a couple more days. Oh, well. it's not like i'm going to use it in this cold anytime soon.
[ December 10, 2002, 02:42 PM: Message edited by: steve@kps ]