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Old 07-02-2003, 10:33 AM   #1546
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Quote:
Originally posted by Manticore
I wonder how people could tell the performance of an engine by only MEASURING the conrod?

On the same engine if you put longer conrod-you will make transfer and exhaust timing tighter (horter)-you will have more torq and lower RPM on the top, if you put shorter-you will increase timing-means higher top end and lower torq. But don't put to long-you might open exhaust windows on the bottom, when piston on the top dead end-in this case you wll loose performance completely.
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Old 07-02-2003, 01:37 PM   #1547
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Arrow Dennis Richey

Does Dennis frequent these Boards anymore? I tried to get in touch with him on a different Forum without a response. I was wondering if anyone knows how I can get in touch with him?

thanks,
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Old 07-02-2003, 02:08 PM   #1548
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Default Re: Dennis Richey

Quote:
Originally posted by muddywaters
Does Dennis frequent these Boards anymore? I tried to get in touch with him on a different Forum without a response. I was wondering if anyone knows how I can get in touch with him?

thanks,
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Old 07-02-2003, 02:33 PM   #1549
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I really don't have a problem with the piston sticking, just seemed odd. Been racing for 5 years now and never had an engine with this issue is all. I know not to leave the piston at TDC but don't always follow up with it. The piston also sticks sometimes when not left at TDC when you let it cool down and try to restart. The Smeltz Sirrio has very good mid range, and on short tracks I really like it!
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Old 07-02-2003, 03:00 PM   #1550
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Arrow Cartman

had a few questions I would like answered.
Has he totally given up his support to the public?

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Old 07-02-2003, 03:10 PM   #1551
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Originally posted by muddywaters
had a few questions I would like answered.
Has he totally given up his support to the public?

muddywaters
You got PM
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Old 07-03-2003, 09:57 PM   #1552
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Default Sirio Outlaw 12 Carb Sticking

I guess my first post was a little confusing.

The piston isn't sticking. The slide on the carb sticks when I set the idle. Apparently the idle screw doesn't align with the slide as it should and when I set it for a good idle it messes up the operation of the carb... the slide is stiff and wants to stick once it gets wide open.

As previously mentioned, the work around is using the trim on the radio to set the idle. But its a limited fix because when i hit the brakes the servo pulls the slide closed and the motor gets starved for fuel and dies if I use more than just a tap on the brakes.

I'm learning to live with it but i'd prefer more control.

Any suggestions??
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Old 07-03-2003, 10:45 PM   #1553
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This was a problem with the older 3 needle Sirio carbs. The idle set screw is too fat at the end and does not allow the slide to work properly. A friend of mine sent his back to Trinity and they gave him a new one. You may want to look into this.
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Old 07-04-2003, 01:52 AM   #1554
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Quote:
Originally posted by InitialD
I don't think so... Short rod engines are suppose to be better at the top end.

Anyway, I actually physically measured the Sirio conrod. Their lenghts are actually the same as the Collari engines (Picco based). The only difference was the bushing hole was bigger. I would think that since Dennis once categorised the Collari as a mid rod engine, the Sirio should also fall into the same category. Neither short nor long
Sorry to pinch your bubble, but....

Anyone told you that the stroke of an engine SHOULDN'T be measured by measuring the conrod? should be measured by the radius from the center of the crank to the center of the conrod pin (as did on full size engines), multiply by 2 those measurement and you will get the stroke of an engine with this crank....

If an engine is a short rod or a long rod shouldn't mean anything about their performance. You can have an engine with a 13mm stroke and a conrod of 30mm and their stroke still be 13mm, not 30.

Conrod lenght affects to other parameters... (linear velocity of the piston at different angles of the crank, dwell time and others like side loads applied to the piston sides but never tell you where should be located their power curve).
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Old 07-04-2003, 02:14 AM   #1555
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Quote:
Originally posted by Corse-R
Anyone told you that the stroke of an engine SHOULDN'T be measured by measuring the conrod? should be measured by the radius from the center of the crank to the center of the conrod pin (as did on full size engines), multiply by 2 those measurement and you will get the stroke of an engine with this crank....

If an engine is a short rod or a long rod shouldn't mean anything about their performance. You can have an engine with a 13mm stroke and a conrod of 30mm and their stroke still be 13mm, not 30.
Thanks for taking the time to reply amidst all other useless replies that others gave. I found yours to be the most constructive

Anyway, if you have read my post, I did not relate conrod length to length of stroke the engine makes. Anybody knows that they are not the same. Please re read my post.

Quote:
Originally posted by Corse-R
Conrod lenght affects to other parameters... (linear velocity of the piston at different angles of the crank, dwell time and others like side loads applied to the piston sides but never tell you where should be located their power curve).
I agree with your first statement but I cannot agree with the statement that one is not able associate the engine's power curve with the conrod length. Engines with longer conrod have a better crank angle upon blowdown than engines with short conrod. Having a longer conrod therefore creates more torque. Dennis Ritchey will tell you this.

In his older post, I quote;

Posted by Motorman on 03-11-2002 11:01 AM:

long stroke = more torque at what used to be the expense of revs
short stroke = more revs at the expense of torque.

The reason long strokes don't suffer from lack of revs any more is piston materials have made it so the pistons are alot lighter and hence they don't explode near as often from excessive piston velocity caused by a long stroke at big revs.

short stroke engines have lower piston speeds (don't confuse this with RPM)

Also rod length is another factor, longer rod better torque, shorter rod better revs but the long rod engine can turn the same revs as a short rod engine and have better torque. (rod length has no relevance to stroke)

basic explanation in a nutshell
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Old 07-04-2003, 05:18 AM   #1556
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Default Sirio Carb

Thanks Grinder. I'll look into it.
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Old 07-04-2003, 08:58 AM   #1557
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Quote:
Also rod length is another factor, longer rod better torque, shorter rod better revs but the long rod engine can turn the same revs as a short rod engine and have better torque. (rod length has no relevance to stroke)
Quote:
Engines with longer conrod have a better CRANK ANGLE(more peak leverage for a longer time) upon blowdown than engines with short conrod.

Eactly. Hence the reason I have stayed with MT long rod engines all this time. given EQUAL (you must compare apples to apples) timing parameters between a long rod engine and a short rod engine both engines will have the same top end but the long rod will have a significant advantage out of the corner. The limiting factor is that given piston velocity with the longer rod will the piston stay together at higher revs. This is not a problem whatsoever with novarossi 12's so the added rod length is a significant advantage.

Quote:
Anyway, if you have read my post, I did not relate conrod length to length of stroke the engine makes. Anybody knows that they are not the same. Please re read my post.
InitialD
for some reason alot of people think there is a relation, they just ain't getting it.

I'll say it one more time even though courseR has said it two posts ago there is no STROKE difference on any novarossi 12 engine period. Just a rod length difference and a corresponding change in the height at which the liner is located in the case
Quote:
Engines with longer conrod have a better crank angle upon blowdown than engines with short conrod.
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Old 07-04-2003, 09:11 AM   #1558
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Sometimes I don't get to all the Q&A that is requested of me, I apologize for that but in being rercently moved to an upper level executive position at the corporation I work at 80 hour weeks leave little time to do much Q&A. I think some folks think I'm just sitting around waiting their call, they forget that there are many others.

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Old 07-04-2003, 12:17 PM   #1559
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Wassssuuuupppp????????
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Old 07-04-2003, 11:45 PM   #1560
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Motorman,i read somewhere that there is a novamega and rex .12 that are exactly the same as the MT12 engine.Do you know exactly which models they are,thanks.
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