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Old 07-07-2003, 11:47 PM   #1576
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Quote:
Originally posted by tl2111
Corse-R is ur Sirio a AAC or ABC type, if they are AAC then I believe it should run cooler??
Nope, mine was one of the first batch ABC engines (black head, leaky 3 needle carb). Engine solid as a rock, thru their P/S went more than 5 gallons and still strong. First engine mod was changing those carb for a Nova one, solved all their carb problems.
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Old 07-08-2003, 02:10 PM   #1577
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The plastic venturi on the Novarossi NS12 appears to be the same size and taper from the picture as the all metal carb is on the MT-12, so I don't think it's meant to be a restrictor but maybe more about keeping the incoming air cooler since it will not hold heat as well as the aluminum will. They might offer different sizes which would be restrictors but I was just seeing what other people thought about it. In the attached picture of an RB carb that looks like what I think they are attempting as the jet hole size doesn't seem to be tampered with. Thanks!
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Old 07-08-2003, 11:17 PM   #1578
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Question... I was reading the dyno tests on one of the Nitro magazines web pages. One was a Picco 7 port .12... high rpm power, the other was the Orion Drone, lower rpm powerband. The question I have is on the right pipe for each motor. Lets say for a 10th scale touring car. Do you use a pipe that compliments the power band, such as a high rpm pipe on the 7 port or do you want a lower rpm "torque" pipe to help it make power lower in the rpm range. Or would that just take away too much top end and make it just average all through the power band? Same for the Drone.. torque pipe or high rpm pipe... and why?
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Old 07-08-2003, 11:42 PM   #1579
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An engine that has good bottom end should be complimented with a pipe that would make the top end good. That's the general rule.

You should not discard the subject of gearing when talking about engine RPM. A car that has a high internal drive ratio or has a Centax clutch that has a tight clutch spring would favour an engine that can make high RPMs. Hence if the engine is already good at the top end, you may want a pipe that is low to mid end biased to unload the bottom end.

Torquey engines should go with high revving pipe to let it unload at the top.
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Old 07-08-2003, 11:45 PM   #1580
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Quote:
Originally posted by ottoman
Question... I was reading the dyno tests on one of the Nitro magazines web pages. One was a Picco 7 port .12... high rpm power, the other was the Orion Drone, lower rpm powerband. The question I have is on the right pipe for each motor. Lets say for a 10th scale touring car. Do you use a pipe that compliments the power band, such as a high rpm pipe on the 7 port or do you want a lower rpm "torque" pipe to help it make power lower in the rpm range. Or would that just take away too much top end and make it just average all through the power band? Same for the Drone.. torque pipe or high rpm pipe... and why?
I think it is depend of application ( track design). Some tracks requered more torq some requered more RPM.
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Old 07-09-2003, 02:24 PM   #1581
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Dennis,

On the bottom of some pistons there is a relief cut or the bottom of it has been machined smaller diameter. Do you think that can make an engine stall or not run as good since when the piston is at TDC that the exhaust port is slightly open if you look at it from the side?
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Old 07-09-2003, 04:51 PM   #1582
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Quote:
Originally posted by Corse-R
Nope, mine was one of the first batch ABC engines (black head, leaky 3 needle carb). Engine solid as a rock, thru their P/S went more than 5 gallons and still strong. First engine mod was changing those carb for a Nova one, solved all their carb problems.
Did all the sirios with the 3 needle carbs have leaking problems? I bought mine in december and its got a 3 needle car and black head but I think you got yours before I got mine and Im not sure If mine is from the first batch or not. Are the ones with the 2 needle carbs the second batch? or ar they a 3rd or 4th batch? I havent broken mine in yet so mabey I could exchange the carb if its one of the bad ones.
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Old 07-09-2003, 05:58 PM   #1583
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Quote:
Originally posted by SlobbaTech
Dennis,

On the bottom of some pistons there is a relief cut or the bottom of it has been machined smaller diameter. Do you think that can make an engine stall or not run as good since when the piston is at TDC that the exhaust port is slightly open if you look at it from the side?
I would hazard a guess that you mean a part cut out of one side of the bottom of the piston? If this is the case then you must have it in back to front. That cut should sit towards the boost port and carnkshaft (not the exhaust port).

If the exhaust port is open below the piston while it is at TDC you would be losing an awful lot of power and if the gap was big enough it would cause the engine to continuously stall or not even start worst case.
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Old 07-09-2003, 06:00 PM   #1584
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Quote:
Originally posted by AE Racer
Did all the sirios with the 3 needle carbs have leaking problems? I bought mine in december and its got a 3 needle car and black head but I think you got yours before I got mine and Im not sure If mine is from the first batch or not. Are the ones with the 2 needle carbs the second batch? or ar they a 3rd or 4th batch? I havent broken mine in yet so mabey I could exchange the carb if its one of the bad ones.
Don't be afraid, not all the Sirios suffer from the leaky carb (mine unit was one of the very early ones). The black head denotes (at least here) ABC construction, the .12 AAC ones come with a blue head.

Saw some Sirios with 3 needle carbs that don't leak and others leak, seems quite a Loto (some 2 needle carbs still leak, it's a flaw that predates it). Is a real fine engine. if you encounter this problem, quickest, safest and best way to solve it is putting a Nova carb in the place of the plastic unit.
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Old 07-09-2003, 08:33 PM   #1585
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Sorry, it hasn't been cut like they are on the boost port side but the OD of the bottom of the piston has been turned down a little and that cut is about .100" tall. The bottom of the piston doesn't come above the bottom of the exhaust port on the sleeve but since there is a small gap between the piston and sleeve that air can pass through and was wondering what the deal was about it.
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Old 07-09-2003, 11:07 PM   #1586
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Quote:
Originally posted by Corse-R
Don't be afraid, not all the Sirios suffer from the leaky carb (mine unit was one of the very early ones). The black head denotes (at least here) ABC construction, the .12 AAC ones come with a blue head.

Saw some Sirios with 3 needle carbs that don't leak and others leak, seems quite a Loto (some 2 needle carbs still leak, it's a flaw that predates it). Is a real fine engine. if you encounter this problem, quickest, safest and best way to solve it is putting a Nova carb in the place of the plastic unit.
Thanks hopefully mine wont leak because with what trinity is charging for Novarossi engines I can only Imagine what a carb wwill cost.
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Old 07-10-2003, 08:03 AM   #1587
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Quote:
Originally posted by SlobbaTech
Sorry, it hasn't been cut like they are on the boost port side but the OD of the bottom of the piston has been turned down a little and that cut is about .100" tall. The bottom of the piston doesn't come above the bottom of the exhaust port on the sleeve but since there is a small gap between the piston and sleeve that air can pass through and was wondering what the deal was about it.
Hmm, I know what you talking about now. I have never seen it done on the bottom of the piston like that but generally people reduce the OD of the piston at certain areas to reduce friction. But this normally is done around the pin ring area.

If there is a gap visible between the piston and sleeve at TDC through the exhaust port then it wont be helping the engine power any. Some of the fresh mixture entering the engine will go straight out through the exhaust port and reduce the power. I would change the P/S for good measure.
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Old 07-10-2003, 03:16 PM   #1588
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It is undercut to compensate for thermal expansion as it is thin there and would lock up if it were not relieved slightly there. It grows alot there. It also helps to trap a microfilm of oil at the hottest point of the sleeve and piston at full temp.
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Old 07-10-2003, 07:31 PM   #1589
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Thanks everyone!
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Old 07-11-2003, 01:23 PM   #1590
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Hello Dennis. Can you tell me please, if you don't mind, I saw some sleeve and piston set for boats and I was surprized what I saw there. It was 4 ports sleeve-2 transfers and 2 boosters. For some reason right buster and transfer are higher then left, apprx. 1.5 mm or so ( view from the back). Do you have any idea, what for it was done like that. I was thinking it was wrong manufactured, but the guy showed to me second set, which was endentical. I saw a lot of different designs, but not this kind. What is idea behind this uneven porting.
Thnx.
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