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PostPosted: Sat Oct 06, 2012 6:27 am 
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Still in the Driveway

Joined: Thu Oct 04, 2012 1:39 am
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Country: uk
Bikes owned: Gt750 TR750 TR750 Sidecar
Tz375, do you have a chrisian name, strange talkin to TZ375.
it would be nice to find a way to trim the inlet timing at lower rpms, like a ypvs on the ex port, but the pv would have to be very close to the piston to effect a seal, (much lower pressures on the inlet), however I would have thought something in the way to reduce the inlet timing to pull the inlet timing back to about 140 degrees has got to help even if it doesn't actually seal. Never seen anything like this done, so I assume it doesn't work? Or is fairly innefective?

James


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PostPosted: Sat Oct 06, 2012 9:44 am 
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Moto GP
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Location: Illinois
James,

I was looking at the data late last night to fine tune some of the duct dimensions to work out why MOTA on 76 TR750 pipes seems to think it should peak at 8250.

I had made some assumptions as to how wide your intake and exhaust are and whether or not the intake is bridged, now I need to adjust the transfer ducts to your outlet sizes and then I'll add some transfer intake area to better model that duct. You have an enormous amount of intake timing on that motor so I'll try a couple of alternatives and see how much low-mid it will pick up before it starts to lose too much at the top end.

Depending on the fuel you have access to, it might be beneficial to add more compression. My street bike has more than that static and dynamic - but I went overboard and need to drop that a little. Squish could also be tightened. I'd try for 1.2-1.3mm. A wider squish might also help the low end, but the chamber would have to me deeper to keep CR in bounds.

MOTA has just taken a dump. for some reason it's found a set of conditions at exactly 9000 where the iterations are erratic and are diverging rather than asymptotic. One time at 9k it drops to zero and on the next iteration it hits 200hp. This time it swung from 105 to 34 to 500HP, so either the software picked up the flu or I just struck a set of variables that create resonant chaos. I'll get back to you on that.

TZ375/Teazer/Richard


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PostPosted: Sat Oct 06, 2012 10:48 am 
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Still in the Driveway

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Bikes owned: Gt750 TR750 TR750 Sidecar
Hey Richard appreciate your time looking at the data, the inlet has no bridge just a small tit at the top to stop the rings falling in, I can't remember the width, but its gonna be about 75/76% of the bore, exhaust is 72/73% I think. The squish should be closer and wider, I normally look for 85/90ft/s. This is going to be significantly less. I did open out the transfer ducts considerably, but I don't have any data.


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PostPosted: Sat Oct 06, 2012 10:52 am 
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Still in the Driveway

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Bikes owned: Gt750 TR750 TR750 Sidecar
one other thing I did was to sleeve the ex port to give 38/39mm dia at the flange like a TR. It has already converged to a point about 2" from the port and is starting to diverge 1" from the flange.


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PostPosted: Sat Oct 06, 2012 10:54 am 
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Moto GP
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Location: Illinois
That was weird. At one exact intake event, the whole thing went nuts. Half a degree of timing either way was fine.

MOTA is peaking at 8250 and that is where the pipe I used resonates. The stuffing wave is timed perfectly for just over 8000 revs. That may be different to the pipe you are using.

I pulled back intake timing in a couple of steps, and that raises power and torque nicely at the bottom end and the curves all cross at 6000. Unfortunately, the HP lost from 6 up is far more than HP gained below that point, so that isn't going to work on a race motor.

Widening the transfers and dialing in more compression suggests a development path and that's consist with what we have seen before and requires a lot of work and some more welding. I cranked in a ton of compression and much larger transfers and that lifts the whole curve very nicely but too much compression kills the over rev. That can be stretched in the real world with a little more retard in the ignition.

That was fun. Now to get back to work..


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PostPosted: Sat Oct 06, 2012 11:33 am 
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Moto GP
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jamesbdk wrote:
Hey Richard appreciate your time looking at the data, the inlet has no bridge just a small tit at the top to stop the rings falling in, I can't remember the width, but its gonna be about 75/76% of the bore, exhaust is 72/73% I think. The squish should be closer and wider, I normally look for 85/90ft/s. This is going to be significantly less. I did open out the transfer ducts considerably, but I don't have any data.


Those widths are close enough to the data I used to not be a significant issue, and the intake shape is consistent with the data in the model. The exhaust sleeve will make a difference though. That exhaust restriction creates a slightly stronger pressure wave, but doesn't make a huge difference at the peak but adds a bulge from 5500 to 6500 with fattest change at 6000. That was interesting.


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PostPosted: Mon Oct 08, 2012 2:14 pm 
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Bikes owned: Gt750 TR750 TR750 Sidecar
Richard, the converge/diverge normally reduces fuel consumption significantly as well. Good thing on a GT/TR. What I was wondering is how much I would need to reduce the inlet timing at low rpms, and at what rpm point to switch over to fully open to optimise?


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PostPosted: Mon Oct 08, 2012 2:38 pm 
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Moto GP
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Location: Lancaster Pa.
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Bikes owned: GT750 x2 97 -1200 Bandit 86 GSXR1100
jamesbdk wrote:
Richard, the converge/diverge normally reduces fuel consumption significantly as well. Good thing on a GT/TR. What I was wondering is how much I would need to reduce the inlet timing at low rpms, and at what rpm point to switch over to fully open to optimise?
You dont feel reeds viewtopic.php?f=5&t=1812 would be easier to fit up than a variable intake ?

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PostPosted: Mon Oct 08, 2012 2:44 pm 
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Still in the Driveway

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Bikes owned: Gt750 TR750 TR750 Sidecar
Hey Dave, long time no talk, would probably work, but unless very big would suppress peak pwr, by then its not lookin so pretty. I was thinking of a shaft 14mm dia ish at the btm of the inlet port against the piston, half cut away at the port to advance/retard the inlet timing. prob only needs 15/20 deg off each side to make a very significant difference. Plus it would look the same, save for the wheel and cables at one end.


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PostPosted: Mon Oct 08, 2012 3:09 pm 
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Moto GP
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Location: Lancaster Pa.
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Bikes owned: GT750 x2 97 -1200 Bandit 86 GSXR1100
And it would be something different to be tried .. i dont believe i have seen it done before on a GT engine .

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PostPosted: Wed Apr 05, 2017 2:36 pm 
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Still in the Driveway

Joined: Wed Jul 07, 2010 9:53 pm
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Location: San Diego, CA USA
100+ HP is achievable! Thanks to a real TR750 barrel, my 1mm OS (760cc) GT full road race motor is putting out 125 RWHP :up:
I have new Lectron 38mm carbs with power jets, and was running a RITA ignition, but now have just received a digital and programmable ignition from Zeeltronic.
My combustion chambers were redesigned using software from Bimotion.
Would be glad to share info with like minded engine builders.

John

Yes, it has 4 wheels, lol.


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PostPosted: Wed Apr 05, 2017 4:22 pm 
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Moto GP
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Location: Lancaster Pa.
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Bikes owned: GT750 x2 97 -1200 Bandit 86 GSXR1100
It appears the top engine case also needs modding around the transfer area to get some extra HP .. I think Kevin is getting around 135~140 hp with his stock bore drag engine on NOX .

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PostPosted: Thu Apr 06, 2017 8:41 am 
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Moto GP
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Location: Illinois
Hi John,

Nice picture of the car. Glad to see you are putting it to good use.


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PostPosted: Thu Apr 06, 2017 9:48 am 
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Moto GP
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Location: Lancaster Pa.
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Bikes owned: GT750 x2 97 -1200 Bandit 86 GSXR1100
John , is this your setup :up: Image

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