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 Let off some steam today

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Oz1200Guzzi
Don Abbondio
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PostSubject: Let off some steam today   Thu Nov 06, 2014 8:59 pm

Today was my last Uni exam for this year. Why is an old fart like me going to Uni? Don't ask, I have enough trouble trying to answer that myself, without you sticking your nose in...)

Anyway, after my exam I went for a ride, to unload some shit. A funny thing happened - I hit the rev limiter for the first time ever. I wasn't watching the tacho, but I was giving it the berries, big time. Anyway, when it happened and I realised that all was good, my smile got bigger, so I decided to ride further. I think I am better again!

Mark/Pete/guru others, is it safe to move the rev limiter up further? If so how much?

It (the bike, stupid) felt like it could rev much more - there was not even the slightest hint of running out of puff before the cutoff. Engine is bog standard apart from the exhaust. Obviously 8400 rpm is safe - though not many standard bikes (without ECU tweaking) would be willing to go there.

All thoughts welcome but I won't hold anyone to anything - if I do anything, it will all be my doing... (mandatory disclaimer)
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ghezzi
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PostSubject: Re: Let off some steam today   Thu Nov 06, 2014 9:39 pm

The real limit Tony is governed by piston speed.
Stroke x 2, x max rpm, /60 (sec) = m/sec.
For our old dungers the safe limit should be 21m/sec. Of course there are other things in the valve train to consider.

Bella 66mm stroke has a piston speed of 18.26m/sec at 8,300 RPM.
I could go to 9,500 RPM for 20.9m/sec, but it is a mute point when peak horsepower is reached by 8,300.

When Mr Roper forces me to fit bigger throttle bodies, and I find some Carillo rods, Ti rocker gear, a big cam and light flywheel, yeah baby!
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DungeonMaster
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PostSubject: Re: Let off some steam today   Thu Nov 06, 2014 10:06 pm

Well, 8500 sounds good to me.
wait - I have an 1100
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Oz1200Guzzi
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PostSubject: Re: Let off some steam today   Thu Nov 06, 2014 10:11 pm

Might be pretty close Michael. Mine is a 2 valve like yours, just a bigger bore... (and maybe stroke)
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DungeonMaster
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PostSubject: Re: Let off some steam today   Thu Nov 06, 2014 10:12 pm

Close enough?
Works for me. Smile
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beetle
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PostSubject: Re: Let off some steam today   Thu Nov 06, 2014 10:37 pm

What's the power curve on the 2V look like? The 8V curve (at least on a my GRiSO running one of the Mistral maps) peaks at 7400 rpm and stays flat to just after 8000, but even them doesn't plummet. I've had some people screech at me for letting a map run past peak power (bear with me). But of course I says, your still accelerating because power is not dropping horribly. At what point does power start to drop off on the 2V? If it's outside the rev limit and the hardware can suffer through it, there's no reason why you couldn't up the the rev limit. There's no point running it past the point that power plummets methinks.

What did I just say? I've confused myself.
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Oz1200Guzzi
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PostSubject: Re: Let off some steam today   Thu Nov 06, 2014 11:10 pm

Mark, Bum dyno says pretty flat from 5000-8400, and still pulling strong. It's anyone's guess as to reality, but it's certainly not disappointing as it it. Today I cried for my mother - May I have another please?
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grisorosso
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PostSubject: Re: Let off some steam today   Thu Nov 06, 2014 11:16 pm

Not much point after 7800, max torque has been developed, max power too.
There isn't a gear where if (at 7800) you change up a gear, that doesn't put you in the sweet spot.

The sweet spot being where peak power and torque become as one.
Anything close to that is good.

Beauty of that six speed is the closeness of the ratios. Sweet.

Went for a ride today, had a Ducati 1200 Multistrada  follow me for 30 odd ks on
Hollow tree Road between Bothwell and Hamilton...
mate following behind mentioned the Ducati rider had to brake a few times when the corners tightened up, and a couple that had blue metal spread across the riding line.
Grisorosso didn't brake once and I can't ride for shit.

Beetle, ya carn, bloody thing is so smooth it's like linear power almost.
Mad Shit maps for the 2V don't do anything much after 7500 Laughing Laughing
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ghezzi
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PostSubject: Re: Let off some steam today   Fri Nov 07, 2014 12:26 am

1100 stroke is 80mm. 8,300 RPM = 22.13m/sec
1200 stroke is 81.2mm. 8,300 RPM = 22.465m/sec

In the old days 21m/sec was considered the safe limit, however many modern 4 cylinder sports bikes are approaching 25m/sec. But they don't have 95mm dia pistons.

If you want to over rev it, be aware of impending electrical problems ........................ piston 'll knock ya alternator off!
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beetle
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PostSubject: Re: Let off some steam today   Fri Nov 07, 2014 12:53 am

Is 21m/sec somewhat conservative? I regularly take mine to 8500.
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ghezzi
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PostSubject: Re: Let off some steam today   Fri Nov 07, 2014 1:16 am

I did say in the old days. The technical books I bought late last century, were full of examples of things developed and raced earlier last century. From Triumphs thru Honda fours to GS/GSX1100's etc.

Obviously technology advances in metallurgy and manufacturing techniques have moved things forward. But we used to expect high performance engines to last 160,000km, now the average sports bike is pretty tired by 80,000km. Then, when your 20 valve R1 needs seats and valves as part of a reco, the head work alone will be worth more than the bike.

Performance costs!
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Pete Roper
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PostSubject: Re: Let off some steam today   Fri Nov 07, 2014 2:18 am

beetle wrote:
Is 21m/sec somewhat conservative? I regularly take mine to 8500.

Yup, so do I but really the time we spend there is momentary. MEPS doesn't reflect the whole story. One of the major advantages is much lighter piston weights compared to the 'Old Days'. Couple that with stronger rods, better lubricants, Nicasil rather than cast iron bores and a plethora of better ways of disposing of waste heat and the previous limits can be exceeded, if only briefly.

For the simple issues of legal liability rev-limiters are set very low. Bouncing off them will do your engine no harm. Holding it wide open in third while it goes 'Blurp, Blurp, Blurp!' For mile after mile? That's a different matter but just giving it a good caning sometimes is actually beneficial! It's a motorbike! Not a rare example of Russian Orthodox Iconography that will fall apart if shown the light of day!

Pete
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beetle
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PostSubject: Re: Let off some steam today   Fri Nov 07, 2014 2:35 am

Just for the record, holding it in third while it goes 'blurp, blurp, blurp' is something that does happen often. And 2nd, and 4th... at 40%, 50%, 60%, 75% and WOT. For a few seconds. Twice. Every time I do a logging run for a map. This is the last map I'm building, fortunately.
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Grisonut
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PostSubject: Re: Let off some steam today   Fri Nov 07, 2014 3:54 am

Yeah after 8500rpm you're wasting your time on the 8V.
My 1100 doesn't seem to get any more power after 6500 though (bike's stock).
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motomonster
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PostSubject: Re: Let off some steam today   Fri Nov 07, 2014 5:05 am

When my 4V was stock I could feel the motor straining after I passed 7K. I never hit the limiter. With Beetle's new map I have power all the way to 8K, and I hit the limiter quite a few times. Still not used to it.

In any case, I doubt you'd gain much by moving the limiter up. Just shift, man. Laughing
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DungeonMaster
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PostSubject: Re: Let off some steam today   Fri Nov 07, 2014 6:23 am

I think the power development of the 1100 is very good and quite well placed.
It has a nice, pleasant increase from the middle to the top that just works very well. Great motor.

DM
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tocino
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PostSubject: Re: Let off some steam today   Fri Nov 07, 2014 8:17 am

Possibly silly question: I thought the rev-limit setting was just for when the little red triangle flashed and that the rev limiter was fixed by the ECU? Or have I missed a feature in GuzziDiag?
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Pete Roper
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PostSubject: Re: Let off some steam today   Fri Nov 07, 2014 8:46 am

I believe the actual cutoff point is adjustable with Tunerpro. It's not something that can be fiddled with by changing the 'Gear change indicator' function in the dash.

Pete
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beetle
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PostSubject: Re: Let off some steam today   Fri Nov 07, 2014 1:52 pm

What Pete said. We can set the real rev limit which is the point that the ECU says "no more fuel for you". Hence the 'blurp blurp blurp' when you hit the limit. The ECU stops the injectors and then restarts them when the revs drop by 100 rpm. We could set it at 10000 rpm if we wanted to.
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