Power Curve

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Power Curve

Postby fastharry » 18 Sep 2017 18:14

Well i have to say im a bit dissapointed with what i have just seen on the dyno, My 350s/372cc looks to be well behind the factory figure of 35bhp. Probably at the crank. But with open pipes and filters 71mm pistons and a gentle smoothing of the ports i was hoping for better than 27.6 bhp at the rear wheel, it may have picked up a little more, but we shut off at 8000. Looks to be running a little rich, so maybe a bit to come there, but not a lot more. i have been running on a 105 main . The strange thing is the bike is definately not slow, So im hoping the 507 for next season will be a be a good step up.
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Re: Power Curve

Postby 72degrees » 19 Sep 2017 06:27

I've never thought they actually produce a lot more than 30 odd BHP where it matters. My Gilera GFR 125 is claimed to be about that and 'seems' quicker than a Morini 350 - though being 20Kg lighter and fully faired helps with velocity and the electronic power valve 2T always makes it *feel* snappier when it eventually opens at 7000 rpm.

I really ought to get a back to back dyno test on my two to confirm my gut feeling that the 375/L5 is producing significantly more power than the 350/? (both with PHBH28s) version.

The power curve also goes a bit wobbly over 7000 - spark breaking down or ignition advance not spot on?

As Harrymuffin points out, however, perhaps you don't want an engine that needs to be revved to > 8000 to produce power for what you do?

No substitute for cubes in the torque at lower revs department, so the 507 should do the business.
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Re: Power Curve

Postby mgelder » 19 Sep 2017 08:09

The official Morini power 'figures' have always been outlandish, but then most were back in the seventies and early eighties when it was almost unknown for journalists to have access to rolling road dynamometers. 39bhp? Really?

I think one of the American magazines measured a 500 at 25bhp or so at the back wheel when they were a current model. Given the performance this sounds a lot more credible to me, so I don't think your figure of 27 for a tuned 375 is too bad.
Morini stuff on RealClassic.co.uk: http://www.realclassic.co.uk/profiles.html#morini
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Re: Power Curve

Postby fastharry » 19 Sep 2017 10:15

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I ran it because i wanted to no if i was in the ball park jetting wise which i was, and to have a comparison for when i get the 507 done. I think the torque curve is pretty useful for the short speedway tracks that we use, i will gear it accordingly in future. My big decision is what cam to start with for the 507. i looked at someones post put on here a while back that had a multi cam graph showing most of the cams that are supposed to be available and the J that i have comes out fairly well so i will start with that, the one i bought from the members stand at stafford is a bit of an unknown quantity it do's not look to be ground off the base circle as Harrymuffin said they sometimes can. and i will look into the easy cam change change conversion while it is in bits. Has anyone had experience with mikuni's on these bikes? I get a good deal on them from my supplier, Nothing worse than starting a race project with old carbs. The j is on the left, the so called L/L5 on the right. Unfortunately i do not have any numbers for the L/L5 cam.
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Re: Power Curve

Postby MarkB » 19 Sep 2017 10:37

My 350/501 (Excalibur engine) had the J cam, which gave waves of lovely torque. The engine was very flexible with strong acceleration. Despite being much more powerful in all ways than my 350 Sport, it produced about 29bhp on the dyno.
"I'll have a V please, Bob."
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Re: Power Curve

Postby pedro » 19 Sep 2017 10:56

I now have Marks old 350/501 and can tell you that despite only 29bhp it is enough to put it past every British 650 that I've ever come across on track, it goes well.
Interestingly I managed to knacker it at Cadwell, having just gone past a Laverda Montjuic, that had nothing to do with knackering it, that had more to do with it's unknown past history over 40 years, and the engine is currently in bits, I have an L cam from a late trailie, which I intend to try, although I don't think that there is much wrong with the J cam.
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Re: Power Curve

Postby MickeyMoto » 19 Sep 2017 13:18

The torque curve is good past peak torque.

Is the J cam from the Excalibur? If so, then good torque from 2.5k.
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Re: Power Curve

Postby fastharry » 19 Sep 2017 21:42

Mine is a New York 507 which i think is the same , So i will go with that j cam to start with, Im looking forward to trying the bigger engine for comparison. What went bang at cadwell? would be interesting to no. If you get the L cam in please let us no how it performs.
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Re: Power Curve

Postby smotorboy » 20 Sep 2017 13:58

Well FastHarry, I have good news and some not so good news:

1st- a well tuned and properly run-in 350 K2 street legal will pull 26 hp on a dyno at the rear wheel on a cool day at sea level...
Mine did before I turned it into a dedicated land speed bike...

2nd- The good news is you are making a lot more torque everywhere than the 19.5 lb-ft my 350 made at peak,,,, Torque is Acceleration !

3rd- Morinis don't breath very well at high rpm so our hp numbers are less than they could be....However the Torque numbers are good...

4th- I guess you have 350 cylinder heads on that motor....If so, think about acquiring some 500 heads to go with your large bore....If you do, I would bet your HP numbers will go up as the 350 heads have exhaust valves on the small side of ideal ...

5th- These motors are very timing sensitive and the rear cylinder will go into detonation easily, so multiple ignition curves are an advantage in getting everything from the motor ...The Sachse system has 9 to chose from...

Best wishes for your future Track success,

Robert in California
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Re: Power Curve

Postby fastharry » 20 Sep 2017 19:24

Thank you Robert, Yes i was impressed with the torque curve, and yes it do's pull well. It do's have the 350 heads, It was all just an interim/stop gap bike while i get my 507 and my Bsa B50 engines finished. so the winter will bring some changes, The 507 will get done, i want to push some of the bigger twins that are in my class, Ignition is one of my biggest conumdrums. Its fine people saying that there is nothing wrong with the original system, and i would agree, so get me a new one please and i will buy it, to be let down by a 40 year old ignition when you have done all the race prep driven hundreds of miles only to be let down by an old component do's not register in my book. i will have a word with the saches bloke.
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Re: Power Curve

Postby huub » 20 Sep 2017 21:00

if you want to extract the last bit of power a programmable ignition is nice to have , i had a bit of a hesitation before the 350 went into the proper powerband, (350 dart engine)
turned out retarding the ignition between 4000 and 5500 completely solved that
i was amazed how well you can feel small differences in ignition timing.
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Re: Power Curve

Postby fastharry » 20 Sep 2017 21:57

The biggest headache with running these new style ignitions is having to run a battery. Something i have always tried not to do on a race bike, I will try to find out what the draw is on the sachse unit.
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