ESE's works engine tuner

[marsheng]

Really - tell me then why every stock TZ350 I have ever seen runs over 70* - add an aftermarket thicker modern radiator and if you are lucky
it might get down to 60* on a cool day.
I had to completely change the water routing with a plate welded on top of the cylinder, then CNC an impeller 50% deeper to get the TZ400
down to 50* where it should be.

Is it a water pump issue or size of radiator issue? The 2 are to a large extent independent. The original question was about water pump. The pump with road going air flow through the radiator may well be sufficient.

[wobbly]

Anything making serious power needs a shit load of pump and radiator.
General rule is 1L/Min/Hp - and the RSW did 50L/min with the whole of the frontal area filled with radiator in an effort to keep it at 50*C.
No way would any TZ250/350 not boil instantly without a pump,no matter how fast the road speed.
A water cooled head only, is a special case off on a serious tangent - rejecting the head load transferred into the combustion
chamber of a Bucket is nothing like what is needed doing the whole cylinder of a highly tuned road race engine.
Like I said the 400 needed an impeller 50% bigger than the stock TZ350 to pull the temp down to a proper level, with as big a radiator as would fit,and
that just keeps to 50*C even doing 235Km/Hr in 20* weather.

[marsheng]

Anything making serious power needs a shit load of pump and radiator.
General rule is 1L/Min/Hp - and the RSW did 50L/min with the whole of the frontal area filled with radiator in an effort to keep it at 50*C.
No way would any TZ250/350 not boil instantly without a pump,no matter how fast the road speed.
A water cooled head only, is a special case off on a serious tangent - rejecting the head load transferred into the combustion
chamber of a Bucket is nothing like what is needed doing the whole cylinder of a highly tuned road race engine.
Like I said the 400 needed an impeller 50% bigger than the stock TZ350 to pull the temp down to a proper level, with as big a radiator as would fit,and
that just keeps to 50*C even doing 235Km/Hr in 20* weather.

Great info, thanks.

[oldjohnno]

I'm playing with a Rotax cylinder in a bike at the moment; the original engine had an angled duct that directed the header around the side of the single central downtube. The Rotax on the other hand has a duct that exits straight out from the bore in a plan view. The duct is 50mm long and 45mm diameter and there is about 70mm from the flange face to the back of the frame downtube.

A 45deg bend (about 1.5D radius) that starts immediately at the flange will clear the downtube, but will this affect performance badly (I'm aiming for about 10.5bar)? Or should I keep the header straight and use double downtubes instead?

[Frits Overmars]

I'm playing with a Rotax cylinder in a bike at the moment; the original engine had an angled duct that directed the header around the side of the single central downtube. The Rotax on the other hand has a duct that exits straight out from the bore in a plan view. The duct is 50mm long and 45mm diameter and there is about 70mm from the flange face to the back of the frame downtube. A 45deg bend (about 1.5D radius) that starts immediately at the flange will clear the downtube, but will this affect performance badly (I'm aiming for about 10.5bar)? Or should I keep the header straight and use double downtubes instead?

A forked downtube could be a solution. Substituting the part of the downtube directly in front of the exhaust duct with a ring through which the exhaust header fits, would allow you to maintain the single downtube under the engine. Or maybe you can rotate the cylinder 180°.

[wobbly]

A bend close to the flange that is vertically up or down is nowhere near as bad as a sideways inclined one.
This give asymmetric plugging flow into the cylinder, and upsets the loop scavenging regime.
10 odd bar isnt really pushing the envelope, but if the rest of the setup is synergistic, the header bend may be just a small detraction.

[SwePatrick]

Thanks, and I look forward to some videos of the KX if you get to take a few.

Weekend have gone, but quite succesfull to be honest.
Started out just 'feeling' the machine on saturday, no spectacular.
But we saw a lot of potensial in theese runs.
Driver started way later than his opponent(just a qualifyrun) but almost passed him at the end, my driver had to pull the brakes due to promises that we just tested

Video, mine is the one on the far lane, this run 9,27 on the eigth mile, bad start and heavy braking on the end, just 50mph trapspeed says a lot
The clutch wasn´t good,, it jerked a lot and pulled the cycle forward, hard to stand still and concentrate on a good start.
https://www.facebook.com/patrick.wet...4129881694475/

Sunday, bad weather was heading in, and no power in my camera,, bollocks!
But the track was rearranged to 150m instead of 201m(1/8 mile)
I decided not to touch any tune at all, infact, only thing i checked was sparkplug, nothing else.

Did four runs and best was 6.71 and 79.40mph trapspeed on the shorter track, still nothing was good.(2.077 60ft)
Wheelspin,, a lot!
Even on 2nd gear it was spinning hard.
Tried to heat up tire in an another run, this ended up in wheelspin in 1st gear and a long power wheelie on 2nd, driver had to shut off.
Even though we had problems and had to throttle it on the track this run was an 6.74 and 81Mph trapspeed.(2.403 60ft)

The other two runs was no good, was laying rubber about 150ft
One of theese runs had a better 60ft, 1.9xx something, but it was more like speedway than dragracing at 100ft marker so driver let off the throttle.(my drivers name is Filip)

Good things in weekend was,, pipe seems to be working, just a 5minute calculation job and 2-3 hour building process, not goodlooking, but prototypes don´t need to be goodlooking
Quickshifter was dead on, needed no adjustment at all.
Engine seems to taking it with ease, never any signs of 'stressed out', overheating(was running it on Avgas 100ll) etc etc etc.
No leakage anywere, i just sat in pit talking bullshit to other guys when they were trying to fix their problems, quite nice

The best runhard to see)


It says:
60ft 2.0768862
ET 6.7132968
Trapspeed 127,764(79.40mph)

[oldjohnno]

A bend close to the flange that is vertically up or down is nowhere near as bad as a sideways inclined one.
This give asymmetric plugging flow into the cylinder, and upsets the loop scavenging regime.
10 odd bar isnt really pushing the envelope, but if the rest of the setup is synergistic, the header bend may be just a small detraction.

Thanks Frits, Wob. The downtube can be changed fairly easily so I'll take that route.

[Lightbulb]

Anything making serious power needs a shit load of pump and radiator.
General rule is 1L/Min/Hp - and the RSW did 50L/min with the whole of the frontal area filled with radiator in an effort to keep it at 50*C.
No way would any TZ250/350 not boil instantly without a pump,no matter how fast the road speed.
A water cooled head only, is a special case off on a serious tangent - rejecting the head load transferred into the combustion
chamber of a Bucket is nothing like what is needed doing the whole cylinder of a highly tuned road race engine.
Like I said the 400 needed an impeller 50% bigger than the stock TZ350 to pull the temp down to a proper level, with as big a radiator as would fit,and
that just keeps to 50*C even doing 235Km/Hr in 20* weather.

That's great info their Wobbly. What is the total fluid volume for a RSW ?
How do I figure out the minimum volume of fluid required to cool a 4.5 to 5 hp engine that has to run for 90 seconds ?
You got me thinking overtime again, as if I were not over thinking too many things at the moment.
Neil L

[Frits Overmars]

That's great info their Wobbly. What is the total fluid volume for a RSW ?
How do I figure out the minimum volume of fluid required to cool a 4.5 to 5 hp engine that has to run for 90 seconds ?

I don't recall the coolant flow of the RSW125, only that it was less than in the RSA125 which pumped 60 liters per minute. The RSA125 used the impeller of the RSW250 twin!
For an RSA125 doing a 30 minutes race the 1 liter per hp per minute rule of thumb would work out at 1620 liters. That would be a bit much to carry around, but some clever mind came up with the idea of employing a radiator and recirculating the coolant.
Your 5 hp engine would need 7,5 liters over 90 seconds if the cooling system were total-loss (and then you wouldn't need a radiator at all) but the actual volume, determined by the volume of the radiator and the rest of the cooling system, would be about 3 liters, give or take.

[FastFred]

Anything making serious power needs a shit load of pump and radiator.

........................ ... making serious hp, TZ had better get a bigger radiator.

[wobbly]

Yes Fred, all TZs need more/better rad.
What model are you talking, as I have a CAD file tor TZ350 50% bigger impeller and shaft as well.
Edit - Ha, reckon I misread what TZ you were referring to.

[2T Institute]

If you look at the dyno charts of all the usual 250 MX engines, they are miles over the pipe and make so little power past 10,000
I could see no point in reving there at all.

What about using the brakes while the bike is in the air? It won't slow you down but will change the angle of the bike, same with the throttle.

[FastFred]

Edit - Ha, reckon I misread what TZ you were referring to.

Yes, true. I meant TeeZee but its interesting/helpfull to have heard about the water temp for a performance 2T and flow required, thanks.

[chrisc]

To ride, this bike feels exactly like the power curve suggests, challenging. It's been great for my riding though and what a challenge. Love it.
Red line is current set up, as received from Dave with a new ring fitted and the muffler repacked.
Blue line is Cully's RG50 with fairly stock cylinder and a few little things done to it. Rick's riding this at the moment.



You'll notice the obvious brick wall in the power at 13,100 rpm. A 7.8hp ish drop in power over a few hundred RPM isn't exactly great over rev and I'm keen to see if I can get more of this back. It has enough peak power but needs to be more rideable.
We have a few area's to look into but suggestions on what might normally cause this would be great.

For a quick experiment, we tried running a 25mm long PVC tube on the end of the carb. No peak power was lost and about 0.5-1hp was gained in the mid range. No change to the over rev wall.

Records I got from Dave has the following for this engine:
Squish Clearance 0.90mm
Exhaust Timing ºatdc 81.5 =197
Transfer Timing ºatdc 115.5 =129

Here's a few laps on the local Mt Wellington kart track. I've since got a RS125 rev counter fitted along with the shift light (comes on 12,800rpm) and soon to have a temp gauge too.