Dumb noob question about HP

sjeff35 · 10-01-2017, 02:18 PM

Hey there,

I've only had one bike in the past, (2007 HD Sportster)

How do they get 25 HP out of the 250 cc RX3 and only 16 out of the 230 cc on the TT250?

Really curious about this!

Thanks

ben2go · 10-01-2017, 02:43 PM

Quote:

Originally Posted by sjeff35

Hey there,

I've only had one bike in the past, (2007 HD Sportster)

How do they get 25 HP out of the 250 cc RX3 and only 16 out of the 230 cc on the TT250?

Really curious about this!

Thanks

It's all in the head and cam. The 230 uses a single cam with a single lobe to operate both valves. The RX3 engine uses a double lobe cam with four valves. More air and fuel in more power out.

sjeff35 · 10-01-2017, 04:29 PM

Quote:

Originally Posted by ben2go

It's all in the head and cam. The 230 uses a single cam with a single lobe to operate both valves. The RX3 engine uses a double lobe cam with four valves. More air and fuel in more power out.

Thanks Ben

Makes sense

pyoungbl · 10-01-2017, 05:55 PM

Also, the TT250 is pushrod operated and air cooled. The pushrod system limits revs and air cooling means greater clearances due to less control of the heat being generated. Not only is the RX3 water cooled for better heat management, it has a much lighter valve train so the RX3 can rev well beyond its 9K red line. The TT250 does not have a tach so we cannot see how limited its rev range really is. The good part is that the TT250 engine is really old school and darn near indestructible with only modest maintenance.

Peter Y.

ben2go · 10-01-2017, 09:25 PM

Quote:

Originally Posted by sjeff35

Thanks Ben

Makes sense

BlackBike · 10-01-2017, 11:59 PM

How much more beneficial is the fuel injection ?

pyoungbl · 10-02-2017, 09:51 AM

I think fuel injection makes a big difference when you are talking about both power and reliability. The FI will constantly adjust to get to a set A/F ratio. That's what the O2 sensor is doing. On a carb you will probably have the correct A/F ratio in some riding conditions but outside that window it's a crap shoot. Throw in variables like temp, altitude, wear...then the carb gets less and less desirable. With that said, if you were just shooting for max power at WFO I suspect you could set up a carb to produce power but it would probably run like crap at any other setting.

Peter Y.

ben2go · 10-02-2017, 10:10 PM

Quote:

Originally Posted by pyoungbl

I think fuel injection makes a big difference when you are talking about both power and reliability. The FI will constantly adjust to get to a set A/F ratio. That's what the O2 sensor is doing. On a carb you will probably have the correct A/F ratio in some riding conditions but outside that window it's a crap shoot. Throw in variables like temp, altitude, wear...then the carb gets less and less desirable. With that said, if you were just shooting for max power at WFO I suspect you could set up a carb to produce power but it would probably run like crap at any other setting.

Peter Y.

Pretty much plus FI is smoother through out the rev range and fuel mileage is better. Power could be better but it really depends on the engine.

Inroads · 10-03-2017, 06:46 AM

The RX3 is in a higher state of tune(water cooled,4valve,FI)and 25 hp is in the upper state of a 250cc.

You can get more but then you can’t run regular gas and engines become peaky.

Big advantage in FI is when you go up in altitude and it maintains optimum F/A ratio.

The biggest advantage though IMO that FI has its ability to handle Ethanol so much better

Than a carb and there is no petcock to worry about cutting off.

Of course the downside is you now have a fuel pump to contend with.

Good news is that FI systems (Delphi in the RX3’s case) have become ultra reliable and

Trouble free.

Jay In Milpitas · 10-03-2017, 08:00 PM

Quote:

Originally Posted by BlackBike

How much more beneficial is the fuel injection ?

Same as in a car or truck engine.

AdventureDad · 10-03-2017, 08:09 PM

I can't imagine the rx3 isn't peaky, and would not want ANY bike with a more narrow power than the rx3. Not for any price. I really like efi but we forget weve run carbs for oh about a 100 years now.

Jay In Milpitas · 10-03-2017, 08:11 PM

Quote:

Originally Posted by sjeff35

Hey there,

I've only had one bike in the past, (2007 HD Sportster)

How do they get 25 HP out of the 250 cc RX3 and only 16 out of the 230 cc on the TT250?

Really curious about this!

Thanks

First, welcome to the herd.
The engine used in the TT is descended from the Honda CG engine which never made it to the USA. It was designed for less developed countries to require less specialty type tools and equipment for service. Yes, it uses pushrods and it also only has one cam lobe. Wrap your head around that.

The state of tune for the engine is low to promote longevity by under stressing the parts, also to allow use of GOQQ, Gasoline of questionable quality.

So it's a simple basic bike at a simple basic price.

10-01-2017, 02:18 PM	#1
sjeff35 Join Date: Sep 2017 Location: Corrales, NM Posts: 118	Dumb noob question about HP Hey there, I've only had one bike in the past, (2007 HD Sportster) How do they get 25 HP out of the 250 cc RX3 and only 16 out of the 230 cc on the TT250? Really curious about this! Thanks
	0

10-01-2017, 11:59 PM	#6
BlackBike Join Date: Feb 2016 Location: George West, Texas Posts: 4,097	How much more beneficial is the fuel injection ? __________________ ***************************************** 2015 Bashan"Blaze" BS250GY-31 (DB-07K-250) GONE 2017 Suzuki V Strom 650 XT "We are all born ignorant, but one must work hard to remain stupid." ~Benjamin Franklin~
	0

10-03-2017, 08:09 PM	#11
AdventureDad Join Date: Apr 2016 Location: South Mississippi Posts: 253	I can't imagine the rx3 isn't peaky, and would not want ANY bike with a more narrow power than the rx3. Not for any price. I really like efi but we forget weve run carbs for oh about a 100 years now. Last edited by AdventureDad; 10-03-2017 at 11:03 PM.
	0

10-01-2017, 05:55 PM	#4
pyoungbl Join Date: Feb 2016 Location: Portsmouth, Virginia, USA Posts: 632	Also, the TT250 is pushrod operated and air cooled. The pushrod system limits revs and air cooling means greater clearances due to less control of the heat being generated. Not only is the RX3 water cooled for better heat management, it has a much lighter valve train so the RX3 can rev well beyond its 9K red line. The TT250 does not have a tach so we cannot see how limited its rev range really is. The good part is that the TT250 engine is really old school and darn near indestructible with only modest maintenance. Peter Y.
	5

10-02-2017, 09:51 AM	#7
pyoungbl Join Date: Feb 2016 Location: Portsmouth, Virginia, USA Posts: 632	I think fuel injection makes a big difference when you are talking about both power and reliability. The FI will constantly adjust to get to a set A/F ratio. That's what the O2 sensor is doing. On a carb you will probably have the correct A/F ratio in some riding conditions but outside that window it's a crap shoot. Throw in variables like temp, altitude, wear...then the carb gets less and less desirable. With that said, if you were just shooting for max power at WFO I suspect you could set up a carb to produce power but it would probably run like crap at any other setting. Peter Y.
	1

10-03-2017, 06:46 AM	#9
Inroads Join Date: May 2015 Location: Wimberley Texas Posts: 193	The RX3 is in a higher state of tune(water cooled,4valve,FI)and 25 hp is in the upper state of a 250cc. You can get more but then you can’t run regular gas and engines become peaky. Big advantage in FI is when you go up in altitude and it maintains optimum F/A ratio. The biggest advantage though IMO that FI has its ability to handle Ethanol so much better Than a carb and there is no petcock to worry about cutting off. Of course the downside is you now have a fuel pump to contend with. Good news is that FI systems (Delphi in the RX3’s case) have become ultra reliable and Trouble free.
	1