[QUOTE=TZ350
EngMod2T is very usefull and only $400 USD to buy, everyone should have a copy ....[/QUOTE]
Won't be long before everyone is racing simulator programmes anyway.....cheaper than actually building something.
Low personal B.M.E.P.
[QUOTE=TZ350
EngMod2T is very usefull and only $400 USD to buy, everyone should have a copy ....[/QUOTE]
Won't be long before everyone is racing simulator programmes anyway.....cheaper than actually building something.
Forum whore
Lot less noisy than a real dyno too ....Originally Posted by Grumph
Forum whore
Ok .... this is where the simulated rubber hits the road.
We are going to see if we can make this.
Bearing in mind this is simulated crankshaft hp that assumes an expertly made motor and that the DynoJet dyno we use graphs rwhp and there will be some differences because of transmission losses and workmanship.
Red line is my efforts with EngMod2T, Blue line is after Wobbly polished it up a bit and replaced the RS pipe with one of his own design.
First off is to fit a degree wheel.
and set the deck-hight and squish clearance
then zero the degree wheel
The transfer timings
and transfer port angles
the exhaust port data, Ex opens 78.5deg ATDC, 0.5 deg now thats pretty exacting.
I will have a measure up and see what I have got then its off to the workshop for a bit of porting fun.
Armature speller
Cheaper to race 2-strokes too, no need to get a sub-woofer.Lot less noisy than a real dyno too ....
Forum whore
Measuring what I have.
A trick suggested to me by Speedpro is to use a piece of lockwire flattened on the end to feel for the port opening.
Mine finished up 0.5mm thick, so I raised the barrel 0.5mm and in theory what I read on the degree wheel and the port timing the motor sees when its all put together and running will be the same thing.
Finding the transfer opening points.
118.5 deg ATDC, Wobbly wants 116 for the main and 117.2 for the other two, so close and fortunatly the roof angles are already close too so not much work needed there.
A look at the Exhaust
Looking for 78.5 deg ATDC, and its way out at 86.5, so plenty to do here.
Remember you cant just copy these timing's because its all about STA or specific time area and is peculiar to your target RPM and Power output.
But Wobblys rule of thumb is, low and wide for the transfers to maximise blowdown time area which is usually in short supply on a single exhaust port cylinder like mine and if you have multiple exhaust ports Low and Wide allows a low exhaust port which helps keep the pipe in resonance for longer (wider power spread).
Forum whore
Yes ... screeeechi tweeters are cheaper ....
if we could get incense candles with the 2-stroke smell too we would be made.
Armature speller
Castrol candlesYes ... screeeechi tweeters are cheaper ....
if we could get incense candles with the 2-stroke smell too we would be made.
Forum whore
Porting tools
Ok ... ported the exhaust port.
Slipped a bit and garked around the transfer, thank goodness for steel putty.
I was able to clean up most of the damage around the exhaust port that happened a while back when a peg came out and allowed the ring to turn and catch in the port.
The barrel is 0.5mm higher because of the lock wire feeler I was using to find the port opening point.
Even curve on the port roof.
Thats as close to the ex opening at 78.5 deg ATDC that I can manage.
Forum whore
Next move is the inlet
Fortunatly most of the work has already been done.
Now to setup the compression ratio.
Basic info
With the ex opening 78.5 deg ATDC a combustion chamber volume of 8.976 or 9cc is required for a 7.4:1 corrected comp ratio.
Small plastic syringes 3-5-10cc can be brought from the Chemist for $2-3 each, I use a 5cc syringe and anti freeze to measure the combustion chamber volume.
Forum whore
As yesterday was Christmas and nothing to do, I had a cylinder to rebore and hone for a friend.
the cylinder was rg400 stock size 50.0 boring to 50.50 plus some clearence so 50.565
All went well and the finished size was honed to 50.56 which in the old money would be .0025" over
I was having a look at some Kart site about honing and they go a few steps further than I did
They bolt torque plates onto the cylinders and leave them for a few hours to let the cylinder distort
bolt an old header pipe and inlet stuff if applicable, and some hone the cylinder hot at about 350° F
http://www.ekartingnews.com/viewtopi...er=asc&start=0
how much are these details worth in hp or reliability, does this allow for tighter clearances ?
Im interested as lately we have talked about the science and simulation and TZs post above reminded me that eventually this stuff needs to be cut into metal as TZ commented earlier "take off some for gearbox losses and some for workmanship" Is this the workmanship we are talking about?
My neighbours diary says I have boundary issues
Forum whore
I like the idea of torqe plates but how much are they worth in hp and reliability? ... I have no idea and I wasn't planning on going to that much trouble myself and expect that a lot of other things have to be got right first before using torqe plates on the final hone job would make much of a differance.
But the talk of how to go about a good finishing hone job, four stones, truing sleeve, stone wear and using that to advantage, it brought back memory’s, I could smell the cutting oil.
What I do know is, that cleaning is important, after washing the cylinder in a cleaning bath and rinsing off, the cylinder wall needs to be scrubbed with a stiff brush (a tooth brush will do for a 50mm bore) and hot water and dish wash.
It needs to be scrubbed vigorously to free the carborundum particles from the hone groves. Then it needs to be rinsed off in hot water and blow dried.
You will know that its been cleaned properly if, as the cylinder dries you see a light yellow stain appear (rust) which will disappear when you oil it.
If you don’t see that stain then it hasn’t been cleaned properly and the carborundum left by the hone stones will cause premature wear of the top ring land and bore.
Just washing in a cleaning bath is not good enough for long life and reliability.
Low personal B.M.E.P.
Torque plates are always a good idea - the aim of course is to finish up with as perfectly round a bore as possible.
Heating the job depends on the cylinder fastening arrangements. TZ750 blocks when set up with torque plates and heated developed a measurable bulge alongside each through stud....things have got better since but if you're working with an iron liner and through studs it's worth having a look at the cylinder hot.
Forum whore
I made a set when I was racing a Suzuki T250 fitted with RD350 cylinders for rebores and honing but never thought to measure them hot.
I wasn't planning on going to that much trouble this time, we have been very slopy with our cylinders but your right they are a good idea especialy for our GP cylinders that have through studs, cylinders like RG400's and RGV250's that don't have through studs may not have the same problems with crush distortion but bolting a dummy head and base wouldn't do any harm.
Forum whore
No ... but I guess its another item on the list. I was thinking about more ordinary things like getting the transfers staggered just like Wobbly wants and the port entry windows in the correct ratio of 1.3 -1.2 and 1.1, and curved nicely. The inlet system the correct length and shape without humps and bumps and the workmanship for making a first class expansion chamber and all those imperfections that creep in, just basic stuff.
Bogeyman
Used to be standard practice for small block Chevs, the block casting was very thin walled and bolting up a solid 2" plate dummy head simulated the finished assembly. The siamesed centre bores on the 400s were particularly bendy, think there's only 1/8" between them...
I know a guy who even went to the trouble of putting the block in a powder coating oven for several heat cycles.
Go soothingly on the grease mud, as there lurks the skid demon
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