Yz444 Tuning: Building a Monster Torque Curve
- Thread starter Masterphil
- Start date
Exhaust for 444
MasterPhil,
Have you figured out your exhaust fully yet? Do you have the primary pipe length that will fit? Your meg length is too short. Running stock ports or are they being worked on? Rich/SFO, about how much improvement in flow is being seen on ported 426 heads for both the intake and the exhaust? Is most of the head flow across the lift range or is it rocking the low and high lift flow numbers? I know that this design idea is for a torque engine, but has anyone ever tried a LARGER carb on the Yam engines?
Phil, in one of the early posts you mentioned 9k as the peak hp rpm, and then said you were going to change it to 9k?? Were you meaning to say something else?
Since I don't have a 426 I will have to ask, what is the stock rev-limiter set up for. From the previous posts, I figure that SFO typically runs a bit higher rpms than Rich does. Are there comparable dyno charts online showing Rich's and SFO's 444 engine runs? I already know, diffferent dyno and different results. Never hurts to compare the curves.
Swiss
MasterPhil,
Have you figured out your exhaust fully yet? Do you have the primary pipe length that will fit? Your meg length is too short. Running stock ports or are they being worked on? Rich/SFO, about how much improvement in flow is being seen on ported 426 heads for both the intake and the exhaust? Is most of the head flow across the lift range or is it rocking the low and high lift flow numbers? I know that this design idea is for a torque engine, but has anyone ever tried a LARGER carb on the Yam engines?
Phil, in one of the early posts you mentioned 9k as the peak hp rpm, and then said you were going to change it to 9k?? Were you meaning to say something else?
Since I don't have a 426 I will have to ask, what is the stock rev-limiter set up for. From the previous posts, I figure that SFO typically runs a bit higher rpms than Rich does. Are there comparable dyno charts online showing Rich's and SFO's 444 engine runs? I already know, diffferent dyno and different results. Never hurts to compare the curves.
Swiss
pursang262
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- Jul 22, 2000
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stock rev limiter is at 11,700rpm
SFO
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- Feb 16, 2001
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On the 450 last year we used a Woody Kile big valve head in conjunction with his 41mm keyhole bored carb.
My friend Dale Lineaweaver had some success with modifying the carb airboot transition so we modeled the intake boot and made stereo lith intake horns in 1mm increment length changes and dynoed them all.
It was great having 3D systems as a sponsor.
My friend Dale Lineaweaver had some success with modifying the carb airboot transition so we modeled the intake boot and made stereo lith intake horns in 1mm increment length changes and dynoed them all.
It was great having 3D systems as a sponsor.
So is there a set of dyno charts online that shows the difference between the 39mm carb and the 41mm carb, or is it stock engine vs. fully modded one? I am interested in the comparison of say the modified head with the difference the carbs will make.
Thanks,
Swiss
Thanks,
Swiss
SFO
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- Feb 16, 2001
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I do not have any of the runs from the team last year.
Our development started with a pipe and throat blending everything else stock, we went from 48rwhp to 52rwhp.
Once we went to the big valve head and big carb we never went back, to back to back test the carb mod.
The next big increase after the head was a big intake cam from a place in NZ.
It had a limited life span as it reached off of the bucket.
Our development started with a pipe and throat blending everything else stock, we went from 48rwhp to 52rwhp.
Once we went to the big valve head and big carb we never went back, to back to back test the carb mod.
The next big increase after the head was a big intake cam from a place in NZ.
It had a limited life span as it reached off of the bucket.
So Phil, from your memory, how did the power curves compare between the smaller valve/carb engine adn the bigger pieces? Similar power curve, just higher numbers or did the curve shift to higher rpms? I am guessing that the curve went up without losing the bottom end performance.
Swiss
Swiss
SFO
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- Feb 16, 2001
- 2,001
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Swiss,
Your account seems accurate from my memory.
Once we had the head, intake, cams, we began to diddle with pipes.
It helped that Doug was finishing on the podium hence everyone began to send us pipes gratis.
The tapered head pipes and megaphone designs all created non-linear torque curves on our engine.
The best peak # we got was with a Akrapovic but it had the choppy torque curve. When Doug actually drove it he was pretty quick to give it the thumbs down.
None of the fancy pipes worked with our combo.
The PC pipe we ran was an off the shelf pipe that had a spark arrestor screen in it.
The screen made no difference on the dyno so we left it in.
I can say this about the big carb, we went from a 158 main to a 195, which implies some signal strength differences from my limited understanding.
Bill
Your account seems accurate from my memory.
Once we had the head, intake, cams, we began to diddle with pipes.
It helped that Doug was finishing on the podium hence everyone began to send us pipes gratis.
The tapered head pipes and megaphone designs all created non-linear torque curves on our engine.
The best peak # we got was with a Akrapovic but it had the choppy torque curve. When Doug actually drove it he was pretty quick to give it the thumbs down.
None of the fancy pipes worked with our combo.
The PC pipe we ran was an off the shelf pipe that had a spark arrestor screen in it.
The screen made no difference on the dyno so we left it in.
I can say this about the big carb, we went from a 158 main to a 195, which implies some signal strength differences from my limited understanding.
Bill
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