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All Forums >> RC Cars, Buggies, Trucks, Tanks and more >> HPI Racing >> HPI On-Road >> Speed
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Speed - 11/21/2007 9:09:51 PM   
Northrup822


 

Posts: 5
Joined: 10/11/2007
From: O'FallonMO, USA
Status: offline 		If the engine has a higher RPM will the car be faster? I've noticed that the .12 engines have a higher RPM than any .18-.25 i've seen.
       Post #: 1

RE: Speed - 11/25/2007 11:22:26 PM   
hpi apollo



Posts: 2639
Joined: 5/13/2006
From: Georgetown, KY, USA
Status: offline 		no, engine rpm doesnt have any indication of speed, speed is reliant on everything, engine, clutch, gears, tires, ect, smaller engines have higher rpms and less torque, bigger engine are opposite of that


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RE: Speed - 3/5/2008 2:38:15 AM   
bocam1


 

Posts: 9
Joined: 9/13/2005
From: birmingham, AL, USA
Status: offline 		I have to disagree with you a little on the RPM not making a difference on TOP speed. Yes everything does matter that you said, ie. clutch, tires, gear ratio, fuel source, etc. However the only point I wanted to make is this. If you have a .12 engine that turns 20,000 RPM to make numbers easy, and a .21 that turns 18,000 RPM, If the .12 has enough torque to pull the gear ration all the way, it will be faster on top end. The problem is that some of these engines that are rated at certain RPM can not achieve that RPM due to gear ratio. THis is why a stroker engine in a hotrod works better. More cubic inches, and they tend to rev higher. More RPM, more speed. Just my 2 cents.

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       Post #: 3

RE: Speed - 3/5/2008 2:40:45 AM   
bocam1


 

Posts: 9
Joined: 9/13/2005
From: birmingham, AL, USA
Status: offline 		I have to disagree with you a little on the RPM not making a difference on TOP speed. Yes everything does matter that you said, ie. clutch, tires, gear ratio, fuel source, etc. However the only point I wanted to make is this. If you have a .12 engine that turns 20,000 RPM to make numbers easy, and a .21 that turns 18,000 RPM, If the .12 has enough torque to pull the gear ration all the way, it will be faster on top end. The problem is that some of these engines that are rated at certain RPM can not achieve that RPM due to gear ratio. THis is why a stroker engine in a hotrod works better. More cubic inches, and they tend to rev higher. More RPM, more speed. Just my 2 cents.

(in reply to hpi apollo)
       Post #: 4

RE: Speed - 3/5/2008 11:09:48 AM   
red man


 

Posts: 43
Joined: 3/4/2008
From: , NY, USA
Status: offline 		high rpm is good for drifting

(in reply to bocam1)
       Post #: 5

RE: Speed - 3/5/2008 10:06:06 PM   
iexion


 

Posts: 758
Joined: 8/1/2006
From: Sioux Falls, SD, USA
Status: offline
quote:

ORIGINAL: red man

high rpm is good for drifting

An engine with Mid-High torq range is good for drifting. Drift cars tend to need more torque in the middle and have higher RPM's (talking about a 240sx with a SR20det engine for a basic example)

But with the main point being on RC engines, apollo is mostly correct and we also need to take into mind that that most cars that run a .12 are extremely light weight and dont need a huge engine to get them moving. (as said in another post i can remember)

I also want to add to this that some of these .12 engines co$t more then a good .26-28 big block engine would.

So if we are talking about why a 1/10 nitro with a .12 is faster then a 1/8 with a .26 my bet would be power to weight. Those .12 are becoming more and more advanced and almost hard to control.... if you dont know how to drive it anyways

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       Post #: 6

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