U 4.4 or MR-12?

tylerthetrex
Profile picture for user tylerthetrex
Posts
78
Joined
2/16/2012
Location
Manakin Sabot, VA, USA
tylerthetrex
Edited Date/Time 2/22/2012 5:40pm
I have a 2010 CRF250R that I had the motor modified this past winter. In a dyno test done after it was completed it ran at 40hp with some kind of mix that my engine builder put in it. When we got it home we dumped out the mix and put in some fresh C-12. In a dyno test done a few days afterward it ran at no more than 35hp. Apparently C-12 isn't oxygenated fuel and my bike needs something between 90-95 octane. I've done some research and will probably run U 4.4 or MR-12. Any suggestions or other things I should consider?
|
mx5471
Profile picture for user mx5471
Posts
985
Joined
7/10/2008
Location
USA
mx5471 2/20/2012 5:07pm
2/20/2012 5:07pm
Why not ask the engine builder what he put in it?
newmann
Profile picture for user newmann
Posts
24438
Joined
4/1/2008
Location
USA
newmann 2/20/2012 5:26pm
2/20/2012 5:26pm
So with race gas (C12), your "built" race engine made less power than a stocker on pump gas? I'd be asking my engine builder a few other questions as well.
tylerthetrex
Profile picture for user tylerthetrex
Posts
78
Joined
2/16/2012
Location
Manakin Sabot, VA, USA
tylerthetrex 2/20/2012 5:32pm
2/20/2012 5:32pm
I did indeed ask him but it was MR-12 with some odd 2-cycle additive. I asked his partner who was well-informed of my bike and he simply told me the piece of 90-95 octane rating.
gyd58
Profile picture for user gyd58
Posts
74
Joined
9/7/2011
Location
USA
gyd58 2/21/2012 5:22am
2/21/2012 5:22am
They were probably using Mr12 mixed with MRx01. MR 12 is 87 motor octane and MRx01 is 98 motor octane. Much better than U4.4. MRx01 was typically used straight in 2 stroke mod bikes due to the higher octane requirements and it is perfect for mixxing with MR12 to get octane up on higher compression 4 stroke mod bikes. I would be concerned if you couldn't get better info than you got from the motor builder, he should know what fuel you should run based upon his experience and dyno work.

You could always run Renegade SX4 or SX4+. We run SX4 for practice and SX4+ for races and like it better than VP.

C12 is not what you want to run in a mod 4 stroke. In our experience it makes less horsepower than good non ethanol pump gas.

The Shop

See All »
mxtech1
Profile picture for user mxtech1
Posts
1968
Joined
7/21/2011
Location
Galesburg, IL, USA
mxtech1 2/21/2012 5:29am
2/21/2012 5:29am
Sorry to burst your bubble, but no type of fuel is going to give you a 5hp increase. Average gains are 1-2 hp and sometimes you might see 3hp in an extremely modified engine with very high compression. 40 hp is not alot and I can usually get that out of my engines just by bumping up the compression a bit, jetting, race fuel, and an aftermarket exhaust. If I were you, I would ask to be present when they dyno your engine next time and see what they are doing to get that 40 hp number.

For your info, your stock engine probably makes around 36-37 hp, so im not sure how you are getting less hp out of your modified engine vs stock. Hope you are aware of this, because something is wrong with your engine. And these hp numbers I gave you are at the wheel on a chassis, not on an engine dyno.

As to to your question about fuel, run the U4.4. It is a very good fuel for 4 strokes and it's burns very clean and crisp. You should not be adding octane booster or fuel additives to race fuel, that's just asking for trouble.
tylerthetrex
Profile picture for user tylerthetrex
Posts
78
Joined
2/16/2012
Location
Manakin Sabot, VA, USA
tylerthetrex 2/21/2012 7:39am
2/21/2012 7:39am
mxtech1 wrote:
Sorry to burst your bubble, but no type of fuel is going to give you a 5hp increase. Average gains are 1-2 hp and sometimes you...
Sorry to burst your bubble, but no type of fuel is going to give you a 5hp increase. Average gains are 1-2 hp and sometimes you might see 3hp in an extremely modified engine with very high compression. 40 hp is not alot and I can usually get that out of my engines just by bumping up the compression a bit, jetting, race fuel, and an aftermarket exhaust. If I were you, I would ask to be present when they dyno your engine next time and see what they are doing to get that 40 hp number.

For your info, your stock engine probably makes around 36-37 hp, so im not sure how you are getting less hp out of your modified engine vs stock. Hope you are aware of this, because something is wrong with your engine. And these hp numbers I gave you are at the wheel on a chassis, not on an engine dyno.

As to to your question about fuel, run the U4.4. It is a very good fuel for 4 strokes and it's burns very clean and crisp. You should not be adding octane booster or fuel additives to race fuel, that's just asking for trouble.
To start off thanks for the great advice gyd58

When the engine was built it ran 39hp pushing 40 in the right conditions. I was present at the last dyno run and saw the numbers on the graph. Before the motor was built it had a Yoshi RS4 system and ran 31-32. Along with the RS4 I put in a the PIM-2 (electronic fuel mapping system) and fooled around with the mapping some between the test (made some errors, but fined tuned with my builder later). With the C-12 on a cold day it got no higher than 35.6hp.

What are some of the repercussions of putting in additives?
mxtech1
Profile picture for user mxtech1
Posts
1968
Joined
7/21/2011
Location
Galesburg, IL, USA
mxtech1 2/21/2012 8:40am
2/21/2012 8:40am
The repercussions are you don't know how you are chemically altering the fuel when you put additives in. Additives will alter the specific gravity, octane number (both points and engine), oxygen level, and will also change how the fuel burns. A company like VP offers so many different fuel blends that you should discuss with your enginer builder your fuel needs and then match a fuel instead of trying to concockt your own blend. You could promote pre-detonation which if not fixed will definately lead to engine problems. Unless you are a petroleum engineer, i'm willing to bet you don't know what the fuel is like when you're done mixing it.

VP's website also gives good descriptions of what time of engine the fuel should run in so you could use that to make a good choice. (BTW, i'm not saying only run VP, there are other good fuel makers too, I am just using VP as an example because I have always used them and it's what I personally know.)

I have a suspicion your engine builder is using very high octane, oxygen rich fuel to make peak hp on his dyno to impress you. Probably not a type of fuel you would want to run all the time. I think there are some underlying issues with the weak hp numbers.

To me it sounds like you may have some compression problems, which would explain why it's down on power. When were the piston rings and valvetrain last done? You might suggest to your engine builder to run a leak-down test on it.

If you don't mind asnwering, can I ask what all the engine has done to it? This would help diagnose your situation.
tylerthetrex
Profile picture for user tylerthetrex
Posts
78
Joined
2/16/2012
Location
Manakin Sabot, VA, USA
tylerthetrex 2/21/2012 11:05am
2/21/2012 11:05am
mxtech1 wrote:
The repercussions are you don't know how you are chemically altering the fuel when you put additives in. Additives will alter the specific gravity, octane number...
The repercussions are you don't know how you are chemically altering the fuel when you put additives in. Additives will alter the specific gravity, octane number (both points and engine), oxygen level, and will also change how the fuel burns. A company like VP offers so many different fuel blends that you should discuss with your enginer builder your fuel needs and then match a fuel instead of trying to concockt your own blend. You could promote pre-detonation which if not fixed will definately lead to engine problems. Unless you are a petroleum engineer, i'm willing to bet you don't know what the fuel is like when you're done mixing it.

VP's website also gives good descriptions of what time of engine the fuel should run in so you could use that to make a good choice. (BTW, i'm not saying only run VP, there are other good fuel makers too, I am just using VP as an example because I have always used them and it's what I personally know.)

I have a suspicion your engine builder is using very high octane, oxygen rich fuel to make peak hp on his dyno to impress you. Probably not a type of fuel you would want to run all the time. I think there are some underlying issues with the weak hp numbers.

To me it sounds like you may have some compression problems, which would explain why it's down on power. When were the piston rings and valvetrain last done? You might suggest to your engine builder to run a leak-down test on it.

If you don't mind asnwering, can I ask what all the engine has done to it? This would help diagnose your situation.
I had the piston rings checked and where 'fine'. Was not present for that. The valves were redone with the engine. I had a new top and bottom end as well as a cp piston placed in it. Like I said before there was also some tinkering done with the fuel curves.
TerryK
Profile picture for user TerryK
Posts
9899
Joined
8/17/2006
Location
CA
TerryK 2/22/2012 5:11am
2/22/2012 5:11am
Listen to mxtech1, he knows whats up.

Btw, we are talking different dyno's right?
gyd58
Profile picture for user gyd58
Posts
74
Joined
9/7/2011
Location
USA
gyd58 2/22/2012 2:22pm
2/22/2012 2:22pm
I find it hard to compare dyno numbers from different dynos . I certainly wouldn’t criticize a motor just base upon the dyno peaked at 40hp. Looking at what Op says, 31-32 hp before the motor was built and 39-40 after, sounds pretty good to me to pick up 7-9hp. Down to 35.6hp on straight C12 under different conditions, doesn’t seem unreasonable especially from using MR12. MR12 is pretty potent fuel at almost 10% oxygen. The only thing I would use c12 for in a modern 4 stroke race bike is to run through the bike after riding to clean out the motor from residue of good fuel and to store the bike till the next ride.

There is a big difference in having a 40hp crf250 where the dyno used has a base run of 31-32hp and a 40hp crf250 where the dyno used has a base run of 36-37hp.
CamP
Profile picture for user CamP
Posts
6826
Joined
8/16/2006
Location
Colleyville, TX, USA
CamP 2/22/2012 4:40pm
2/22/2012 4:40pm
I'm not surprised that you lost 5hp with C12. It has waaay too much octane for even the most modified 4-stroke, and it also runs two jet sizes richer than pump gas. If you were tuned for a fuel like U4.4, you are probably 4 jet sizes too rich with the C12. That's 5hp going out the tailpipe.
TerryK
Profile picture for user TerryK
Posts
9899
Joined
8/17/2006
Location
CA
TerryK 2/22/2012 5:40pm
2/22/2012 5:40pm
Ive seen different dynos register a 20rwhp difference on the same 100hp engine on the same day.

Post a reply to: U 4.4 or MR-12?