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REV LIMITER???? (Read 1444 times)
PipJones
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Re: REV LIMITER????
Reply #15 - 03/19/10 at 14:18:59
 
jef.savage wrote on 03/19/10 at 02:04:00:
I don't have a lot of mechanical experience but this sounds very similar to a problem I ran into with my '66 Dodge Charger.  With the stock valve springs the engine would not rev past about 5600 rpm even though the tach showed a 6500 red line.  The springs just didn't have enough tension to close the valves any faster so they would "float", just staying open.  When I had the heads milled and replaced the cam I also replaced the springs with a competition set that had dual inner and outer springs like our bikes.  With the new springs the car would easily rev to it's red line and beyond, even in high gear.

I'm thinking with stiffer springs these engines may rev higher and even allow you to blow one up if that's your goal.


I really hope blowing one of these things up isn't acutally someone's goal. But if it is, give me a call... I'd love to be there
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Re: REV LIMITER????
Reply #16 - 03/21/10 at 03:41:23
 

It's not a goal, just an observation ....


Do you really think it is spring pressure?   We have 4 valves (relatively small valves) and dual springs on those small valves.

Plus, if the valves floated regularly don't you think there might be some popped or bent tulip heads or certainly quite a few burned exhaust valves would have been seen as a consequence?  

(VERY occasionally we do pop a valve head off around here but it is not been noted as being an over-rev situation per se -- it just happens when rolling down the road)
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« Last Edit: 03/23/10 at 09:52:00 by Oldfeller--FSO »  

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Re: REV LIMITER????
Reply #17 - 03/23/10 at 08:55:03
 
Megan at Suzuki America is working on it.

Surprise -- this isn't an easy question for American Suzuki to answer.  It is not listed in a feature list anywhere and the black box does not list all its functions as some of the control is based on PROGRAMMABLE (burn once) E-prom chips and you are actually asking about the details of an old prom burn program located at a vendor that is like 10+ years old.

"I dunno" seems to be the current answer still ....

But she's working on it.


I'm going to draft a letter asking the same question, just to see if it gets routed a different path to a different answer.

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Re: REV LIMITER????
Reply #18 - 04/27/10 at 03:06:31
 
There has been no further reply to either telephone calls or written letters.

Suzuki America does not know .... or Japan won't be bothered to look, take your pick.


So, the mystery continues
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Re: REV LIMITER????
Reply #19 - 05/22/10 at 12:24:11
 
I wonder - over on the Rubber Side Up there has been posted a torque curve going up to 7000. Yet some say there is a 6500 rev limiter. Others have remarked that there is a difference between the early and later ignition boxes. Perhaps the older ones had the rev limiter and the newer ones do not?
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Re: REV LIMITER????
Reply #20 - 05/22/10 at 12:49:23
 
Only way to prove or disprove it since you won't except the statements from the few that have modified their engines to be high rev engines.

send the CDI to a known high roller and do a before and after dyno run.

oh, wait... you'll still question if the numbers can be believed.
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Re: REV LIMITER????
Reply #21 - 05/22/10 at 13:24:10
 
There's no need for a limiter,... so there is no limiter...
She runs out piss before she gets there...  Huh...
If you do over-rev intentionally,.. you may feel what could be perceived as a rev limiter,... that's when the valves go into float, you'll loose compression and she'll fall back... it's a "law of physics" limiter... but by then, she's been screaming to be shifted for more than a thousand rpm's,... probably 7500 or 8000 revs...
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Ludicrous Speed !... ... Huh...
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Re: REV LIMITER????
Reply #22 - 05/22/10 at 14:39:20
 
As a matter of interest, yesterday May 22, 2010, I took my box stock '07 S40 out with the idea of seeing whether I could hit a rev limiter. Note that I have no tach on the bike. After riding it for plenty long enough to be sure it was warm, I put it in second and wound it up till it would go no faster. There was no sound of break-up as one would expect from an on-off rev limiter. It topped at 60 mph, which if Suzuki's table on Page 4-2 of the Owner's Manual is correct, corresponds to 7150 rpm (slide-rule accuracy). I repeated the run using first gear, but quite frankly I am unsure of my own measurements, since I didn't write them down immediately. I think I remember seeing 47 mph in first, which would be about 8700 rpm and which I do not believe. If on the other hand I saw 37 mph the rpm would have been just under 7000. I would expect the rpm in 1st to be higher because there is less aerodynamic drag at the lower speed, but not that much higher. It is easy to misread a speedometer, and I may well have done so.

If anyone cares, I was using 87 octane fuel (with Sta-Bil) from last fall when I put the bike away for the winter. Shell Rotella 15W-40 oil. Bike has about 6200 miles. Temperature about 70 degrees, altitude about 1800 feet.

Suzuki gives the following speeds at 6500 rpm. 1st, 35 mph. 2nd, 55 mph. 3rd, 75 mph. 4th, 90 mph. 5th, 100 mph. There is some rounding, as both the Metric and English speeds are given to the nearest 5, and the Metric and English speeds as given are not exactly equivalent. Because of that rounding my rpm calculations are necessarily inexact.

Okay, people. Since I seem to have a reputation for questioning the methodology of others, here's your chance to question mine.
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Re: REV LIMITER????
Reply #23 - 05/22/10 at 15:04:37
 
I like it,... I'm with ya'!...
Pretty darn gutsy too!... Wink...

Savage pistons are made from Unexplodium... Grin...
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Ludicrous Speed !... ... Huh...
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Re: REV LIMITER????
Reply #24 - 05/24/10 at 19:50:16
 
Even with a tach and a dynamometer, the only way to find out whether an engine has a rev limiter is to wind it up until the rev limiter operates. If the rev limiter doesn't operate, or isn't present, you have to keep increasing engine speed until some other limit is reached. You can do it with the engine unloaded, for example in Neutral. Or you can do it with the engine loaded either on a dynamometer or the road. If someone has a different or better idea, speak up.

Now, as it happens, I spent my working career as an electronics tech. Given a little more test equipment than I have, I would test the ignition box electronically. On the bike, I'd just unplug the wiring from the pulse generator coil in the stator and use an electronic pulse generator to trigger the ignition box. I would then vary the pulse generator frequency to simulate different engine speeds, and observe the spark output with a 'scope. With a little more work, that procedure could also "map" ignition timing at different engine speeds.

If I were going to design a rev limiter for a carbureted engine, given present EPA rules, I would not design a system that worked by interrupting the ignition. That's because the interrupted ignition allows unburned hydrocarbons into the exhaust. Instead, I would start retarding the timing as the engine approached redline. The timing could be retarded even to the point that the spark fired just before exhaust valve opening. The rider would never realize the limiter was working, but would just feel the engine going flat and revving no higher. Fuel-injected systems do it by interrupting the injectors, but a carbureted engine doesn't have that option.
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Re: REV LIMITER????
Reply #25 - 05/25/10 at 08:54:16
 

OK, we can pretty much say we don't have an ignition cut off type of rev limiter.

We may have a spark retard electronic only version of rev limiter, but apparently it will still let you go way up past the official 6,500 rpm red line.

Construction of the engine is apparently fairly explosion resistant just from the natural construction of the motor.


Unexplodium piston, indeed !!


Question answered well enough for me -- jest run it !!
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Re: REV LIMITER????
Reply #26 - 05/25/10 at 10:44:13
 
Charon wrote on 05/24/10 at 19:50:16:
Even with a tach and a dynamometer, the only way to find out whether an engine has a rev limiter is to wind it up until the rev limiter operates. If the rev limiter doesn't operate, or isn't present, you have to keep increasing engine speed until some other limit is reached. You can do it with the engine unloaded, for example in Neutral. Or you can do it with the engine loaded either on a dynamometer or the road. If someone has a different or better idea, speak up.

Now, as it happens, I spent my working career as an electronics tech. Given a little more test equipment than I have, I would test the ignition box electronically. On the bike, I'd just unplug the wiring from the pulse generator coil in the stator and use an electronic pulse generator to trigger the ignition box. I would then vary the pulse generator frequency to simulate different engine speeds, and observe the spark output with a 'scope. With a little more work, that procedure could also "map" ignition timing at different engine speeds.

If I were going to design a rev limiter for a carbureted engine, given present EPA rules, I would not design a system that worked by interrupting the ignition. That's because the interrupted ignition allows unburned hydrocarbons into the exhaust. Instead, I would start retarding the timing as the engine approached redline. The timing could be retarded even to the point that the spark fired just before exhaust valve opening. The rider would never realize the limiter was working, but would just feel the engine going flat and revving no higher. Fuel-injected systems do it by interrupting the injectors, but a carbureted engine doesn't have that option.

Hmm,you may have come up with my next project!I do have a pulse generator and a O'scope.I'm thinking a square wave for the pulse.
I guess if you put the CDI input on Ch.1,and the output on Ch.2,it would more or less show the advance curve and how it behaves as the revs go up.
The Savage fires twice per revolution,doesn't it?
As an aside,I have a '91 Suzuki Bandit(carbureted)that definitely does use the cut-off type of limiter.Breaks up really well at 13,500 RPMs!
Of course,you did say CURRENT EPA regs,so that doesn't say much.
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Re: REV LIMITER????
Reply #27 - 05/27/10 at 11:26:24
 
Oldfeller--FSO wrote on 03/02/10 at 17:11:18:
But Verslagen, nobody has ever blown up an engine...


Something is keeping us from fatal RPMs ....

I don't think we know yet what it is......



could it be a long stroke, and a low compression ratio?
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Re: REV LIMITER????
Reply #28 - 05/27/10 at 14:55:13
 
Johnboy, it isn't a long stroke -- it is perfectly square or equal ratio which used to mean a performance engine.  Long stroke engines have strokes longer than their bore diameters.   Ours does not have that at all.

8.5 to 1 compression ratio isn't a high compression ratio to modern standards -- that starts at over 9 to 1 and is generally around 10 to 1.  But it isn't a slug either.   It means it is an engine intended to burn regular gasoline.

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Re: REV LIMITER????
Reply #29 - 05/27/10 at 19:07:48
 
ratz wrote on 05/25/10 at 10:44:13:
The Savage fires twice per revolution,doesn't it?


I believe it's once per revolution,... twice per 4 cycle... Huh...
but,.. that's what you meant...
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Ludicrous Speed !... ... Huh...
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