Are the Star YZ250F's using a second injector like the KX250F's?

Joko
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Joko
Edited Date/Time 5/30/2016 1:31am
They are looking very fast, wondering if they are utilizing the second downstream injectors like C4MX and Twisted Develpment are offering? Anyone know who is building their engines?
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ML512
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ML512 5/29/2016 12:16pm
5/29/2016 12:16pm Edited Date/Time 5/29/2016 12:16pm
Joko wrote:
They are looking very fast, wondering if they are utilizing the second downstream injectors like C4MX and Twisted Develpment are offering? Anyone know who is building...
They are looking very fast, wondering if they are utilizing the second downstream injectors like C4MX and Twisted Develpment are offering? Anyone know who is building their engines?
Star Racing builds and develops their engines in-house with assistance from Yamaha.
Zycki11
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Zycki11 5/29/2016 12:49pm
5/29/2016 12:49pm
Still didn't answer the dual injection question. Would make sense to me for top end.
norcal3737
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norcal3737 5/29/2016 12:53pm
5/29/2016 12:53pm
How does an extra injector increase top end? Coming from the performance car world, an injector is merely selected based on CC requirement for horsepower needs.

Can get a little extra power out of the fuel system based on injector tip design that can lead to better fuel atomization, but not catching what two injectors can do for power?
BobPA
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BobPA 5/29/2016 12:57pm
5/29/2016 12:57pm
Zycki11 wrote:
Still didn't answer the dual injection question. Would make sense to me for top end.
How would a second injector increase top end at all?

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Beast666
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Beast666 5/29/2016 1:50pm
5/29/2016 1:50pm
BobPA wrote:
How would a second injector increase top end at all?
The positioning of the second injector further from the cylinder head allows for the fuel time to atomize prior to combustion due to the higher velocity of the air in the intake tract. The primary injector in the throttle body is to close to allow for properly atomize at high RPM's but positioned properly for low to mid range. The better a fuel gets atomized the more power can be extracted from it.
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BobPA
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BobPA 5/29/2016 1:58pm
5/29/2016 1:58pm
Beast666 wrote:
The positioning of the second injector further from the cylinder head allows for the fuel time to atomize prior to combustion due to the higher velocity...
The positioning of the second injector further from the cylinder head allows for the fuel time to atomize prior to combustion due to the higher velocity of the air in the intake tract. The primary injector in the throttle body is to close to allow for properly atomize at high RPM's but positioned properly for low to mid range. The better a fuel gets atomized the more power can be extracted from it.
Sounds good on paper, but I'm not sold on that. If that is the case why do DI systems work so well? Do you think they run the primary injector up to a certain RPM and then go to the secondary (farther away). Or do you think the secondary comes in to assist the primary after a certain RPM? My RX7 runs a primary and secondary setup, but they do this because under boost the engine requires a TON of fuel, but if you run a giant primary the car will idle like shit because you have to run it at such a light duty cycle.
MR. X
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MR. X 5/29/2016 2:04pm
5/29/2016 2:04pm
I thought (i could be mistaken) the single injector pulse can't keep up with a wide range needed to do the job alone so the duals help where the 1st injector falls off. At least that was my understanding when Polaris had the dual injectors on their snowmobiles.
mb
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mb 5/29/2016 2:08pm
5/29/2016 2:08pm
Boosted 1000hp 2L engines have a wide range. A naturally aspirated 4 stroke mx bike does not.
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chump6784
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chump6784 5/29/2016 2:10pm
5/29/2016 2:10pm
I don't know why you guys are debating whether 2 injectors would work, Kawi added the second injector in 2012 to increase top end from the 2011 model
mx184
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mx184 5/29/2016 2:28pm
5/29/2016 2:28pm Edited Date/Time 5/29/2016 2:33pm
it is a counter sunk injector that is cut at a 37 degree angle that helps with atomizing the fuel which was mentioned above. There is only one injector ! I know, I build it for them.
I am selling them for $ 200 .00 each, this also comes with a swift kick in the ass for anyone who was remotely interested in this bull shit post that I just made up. right wrist = outcomes. figure that out you will be one step closer to a win. You are welcome..
Beast666
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Beast666 5/29/2016 3:16pm
5/29/2016 3:16pm
BobPA wrote:
Sounds good on paper, but I'm not sold on that. If that is the case why do DI systems work so well? Do you think they...
Sounds good on paper, but I'm not sold on that. If that is the case why do DI systems work so well? Do you think they run the primary injector up to a certain RPM and then go to the secondary (farther away). Or do you think the secondary comes in to assist the primary after a certain RPM? My RX7 runs a primary and secondary setup, but they do this because under boost the engine requires a TON of fuel, but if you run a giant primary the car will idle like shit because you have to run it at such a light duty cycle.
DI systems are completely different animals over port injection. With a DI system the fuel is injected at very high pressure right before the spark plug fires. The high pressure as well as injector design allows for instant atomization of the fuel. The pressure has to be higher than the pressure in the combustion chamber at injection or the fuel will not make it into the engine. Most DI systems have multiple fuel pumps to boost up fuel pressure where as a port system injects fuel at 40-45 PSI, A DI injector fires at up to 2200 PSI.
Derek Harris 5/29/2016 3:57pm
5/29/2016 3:57pm
Last year they did not.

This year I do not know.


The dual injector set up works well - GET has offered it for a couple years now - and with lots of tuning time - it's a good power adder. However there are other methods to get results that work well too - that most teams and private companies have been playing with too.

The big drawback to a dual injector set up is added complexity - it gives you more parts to fail - more weight, and more tuning time - which has to be backed up not just in the shop and on the dyno, but on the race track.
The big plus is the performance for the average guy.

Exhaust systems are purchased here in the US all the time - and often they don't help performance at all. but for about 1400-1500 an ignition set up with dual injector kit can be had too - usually with better gains - and of course tuneability. But here stateside consumers read the "X brand powers the holeshot" pipe ads - and eats it up.

I'd say the team, engine builders, and all the hours testing gets the holeshot...not the pipe - but that's me - as pipes certainly play a large role in weight reduction - and at the pro level are completely custom to the engine package.


Underground 5/29/2016 4:18pm
5/29/2016 4:18pm
Derek Harris wrote:
Last year they did not. This year I do not know. The dual injector set up works well - GET has offered it for a couple...
Last year they did not.

This year I do not know.


The dual injector set up works well - GET has offered it for a couple years now - and with lots of tuning time - it's a good power adder. However there are other methods to get results that work well too - that most teams and private companies have been playing with too.

The big drawback to a dual injector set up is added complexity - it gives you more parts to fail - more weight, and more tuning time - which has to be backed up not just in the shop and on the dyno, but on the race track.
The big plus is the performance for the average guy.

Exhaust systems are purchased here in the US all the time - and often they don't help performance at all. but for about 1400-1500 an ignition set up with dual injector kit can be had too - usually with better gains - and of course tuneability. But here stateside consumers read the "X brand powers the holeshot" pipe ads - and eats it up.

I'd say the team, engine builders, and all the hours testing gets the holeshot...not the pipe - but that's me - as pipes certainly play a large role in weight reduction - and at the pro level are completely custom to the engine package.


You guys need to listen to this guy more often cause he definitely knows his shit. Thanks for sharing it too Derek. And yes, some other teams run them. The reason the Yamaha 250 and 450 makes so much dam HP is due the base design of the engine that all these idiots hate, it's straight shot intake at the back of the inlet valve, design of the head allowed by being in reverse, off centred crank and length of exhaust that they are able to run.
Underground 5/29/2016 4:24pm
5/29/2016 4:24pm
Beast666 wrote:
The positioning of the second injector further from the cylinder head allows for the fuel time to atomize prior to combustion due to the higher velocity...
The positioning of the second injector further from the cylinder head allows for the fuel time to atomize prior to combustion due to the higher velocity of the air in the intake tract. The primary injector in the throttle body is to close to allow for properly atomize at high RPM's but positioned properly for low to mid range. The better a fuel gets atomized the more power can be extracted from it.
BobPA wrote:
Sounds good on paper, but I'm not sold on that. If that is the case why do DI systems work so well? Do you think they...
Sounds good on paper, but I'm not sold on that. If that is the case why do DI systems work so well? Do you think they run the primary injector up to a certain RPM and then go to the secondary (farther away). Or do you think the secondary comes in to assist the primary after a certain RPM? My RX7 runs a primary and secondary setup, but they do this because under boost the engine requires a TON of fuel, but if you run a giant primary the car will idle like shit because you have to run it at such a light duty cycle.
Sounds good on paper Bob, and works even better on the dyno. Just takes a ton of know how, fabrication and tuning.
Hcallz5
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Hcallz5 5/29/2016 8:13pm
5/29/2016 8:13pm
Weren't they getting something like 2-3 additional hp on top end with the second injector?

Sounds real nice.

cwtoyota
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cwtoyota 5/29/2016 10:09pm
5/29/2016 10:09pm
Derek Harris wrote:
Last year they did not. This year I do not know. The dual injector set up works well - GET has offered it for a couple...
Last year they did not.

This year I do not know.


The dual injector set up works well - GET has offered it for a couple years now - and with lots of tuning time - it's a good power adder. However there are other methods to get results that work well too - that most teams and private companies have been playing with too.

The big drawback to a dual injector set up is added complexity - it gives you more parts to fail - more weight, and more tuning time - which has to be backed up not just in the shop and on the dyno, but on the race track.
The big plus is the performance for the average guy.

Exhaust systems are purchased here in the US all the time - and often they don't help performance at all. but for about 1400-1500 an ignition set up with dual injector kit can be had too - usually with better gains - and of course tuneability. But here stateside consumers read the "X brand powers the holeshot" pipe ads - and eats it up.

I'd say the team, engine builders, and all the hours testing gets the holeshot...not the pipe - but that's me - as pipes certainly play a large role in weight reduction - and at the pro level are completely custom to the engine package.


Underground wrote:
You guys need to listen to this guy more often cause he definitely knows his shit. Thanks for sharing it too Derek. And yes, some other...
You guys need to listen to this guy more often cause he definitely knows his shit. Thanks for sharing it too Derek. And yes, some other teams run them. The reason the Yamaha 250 and 450 makes so much dam HP is due the base design of the engine that all these idiots hate, it's straight shot intake at the back of the inlet valve, design of the head allowed by being in reverse, off centred crank and length of exhaust that they are able to run.
This. The reverse-flow cylinder head on the YZ-F engines has more potential for horsepower simply due to the straightened intake tract.

Kawasaki is bragging about their 2017 250F having a better intake angle. It will never be as straight as the current Yamaha configuration without drastic chassis layout changes.

Derek, the exhaust thing drives me crazy too. An oversized rotor (on bikes that came with less than 270mm) will do more for your lap times than any exhaust system.
Jrewing
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Jrewing 5/30/2016 1:31am
5/30/2016 1:31am
Good thread. If I had a yami I'd add it.
What's the difference between straight intake horizontal v downdraft yami style.
At what speed does ram airbox start working?

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