ESE's works engine tuner

[Kickaha]

Ok here's a question. Kart guys seem to like to start their karts on the stands then rev them. From cold- Revvvv. Brake
Revvvvv. Brake. RREEEEVVVV brake.

Used to be confined to the KT100 guys, dunno if the Rotax Max guys do to and used to annoy the crap out me parked beside someone doing it

Oh yeah, fucked if I know why they do it

[Yow Ling]

Ok here's a question. Kart guys seem to like to start their karts on the stands then rev them. From cold- Revvvv. Brake
Revvvvv. Brake. RREEEEVVVV brake.

What do they think they are doing? They don't seem to be warming them up. They can't be tuning them as they are not to temperature and not under load. What do they think they are doing?

Other concerning thing is the spinning wheels at waist height would take you apart if you walked into them.

Maybe they testing the brakes?

[TZ350]

Page 940-A

Fixers Cylinder and Pipe and some very insightful advice from Wobbly.

My beloved Aprilia RS50 acquired a new Doppler Vortex 50cc kit recently. I bought it because I liked the look of the wide bridged exhaust port and the wide and (I believe) nicely-angled transfer ports. It's advertised as a road kit so it (as I have discovered) has relatively mild port timing.

There's a video showing the inside of the kit here: https://www.youtube.com/watch?v=mUeeycpkpc8 .


The standard Aprilia top end with some exhaust port mods made a bit over 11hp on the ESE dyno. So we put her back on the dyno and, lo and behold, with the Doppler kit she was making just under 10hp with a dip in the power band the size of the Grand Canyon.

But ... we took advantage of the large number of exhaust pipes to be found in the ESE workshop to see if a different pipe might conjure up another pony or two.



So the Conti pipe (which had been largely responsible for an earlier increase from 5hp to 8hp) came off and another pipe went on. Still a large dip in the power band, but substantially more power. Back up to just over 11hp. This pipe was a bit large and only fitted a couple of mm into the barrel. So we shaved a bit off the OD so it would fit in better.

It was probably about 10-12mm shorter when properly fitted, and was a disaster. Back down to just over 10hp. What?? Okay ... so we tried a different pipe. The result was MUCH better. Nearly 12hp with a much nicer looking power curve.

And then for the hell of it, we tried the original Conti pipe with a shorter adaptor between the pipe and the barrel (probably by about 12-15mm). Based on our previous experience of a longer pipe being better, I bet that this shorter adaptor would make things worse. WRONG!!! There was still a chunky dip in the power band, but it was back up to nearly 12hp.

The moral of the story ... the proof is in the dyno! Below centre is a photo of the 5 dyno charts. You can see the range of different results obtained from 3 different pipes, with two of them tried twice each with shorter or longer adaptors. The maximum power varies by around 20 percent, but 4 out of 5 have a similar dip. One doesn't. This is very promising.



The photo on the left illustrates the huge difference that just having a 10mm or so longer adaptor between the pipe and the barrel can make. The photo second from right shows the two adaptors.

So on went the degree wheel and some considered measurements were taken with the result being that we're going to raise the barrel a bit with a spacer, machine the head to fit it into the top of the cylinder. Tweak the squish band and stick her back on the dyno. More exhaust port duration is apparently what is required here.

Two-strokes and dynos ... a match made in, well, if not Heaven, then at least Wonderland. Tim

Simply lifting the cylinder to get 115 on the transfers and 192 on the Ex means you will have shit loads of STA on both, but the thing will then be severely blowdown limited.

It may in fact make better power than what you have now - but such a STA mismatch will always mean narrowing of the useable power and probably even
more issues with big torque holes.

115 is what you would run on a full noise road racing setup, 192 is what a much lower power hot road bike might need - so the resulting power will always be compromised by the missing blowdown
that matches neither the transfers nor the Ex STA.

I am picking that they think there may be excessive blowdown with the standard setup and that by raising the barrel and RPM ceiling that what was excessive blowdown STA at lower rpm is suitably adequate for the higher rpm they are aiming for.

Take a look at the Exhaust port here:- https://www.youtube.com/watch?v=mUeeycpkpc8

So it could be they are tuning for the blowdown area they already have. Yes the spacer plate is easy but it also makes things easily reversible.

If so then the original timings of 90* and 121* by their very nature would produce a small ( though not necessarily correctly matched ) blowdown STA.

Then by simply lifting the cylinder , the transfers suddenly become suitable for a full noise road racing setup, but that small blowdown number remains relatively the same.

Its very similar thinking to lengthening and shortening a pipe by chopping or sleeving the header.

Sure the tuned length is being affected, and the engine may in fact respond to this change favourably, but if you fail to realise that having a header say 28% or 36% of the tuned length will invariably produce huge holes in the torque curve - due to the incorrect positioning of the diffuser.

To prove my point about the pipes, here is a dyno graph of a pipe designed using TSR for a 490 Banshee.



The rpm was some 1500 down , so of course they cut the header, oh dear even less power.
I redesigned the pipe ( with exactly the same length as the shortened version ) and it suddenly seems to work a little better.

The point I was making about cutting or sleeving headers to do a dyno test, is that simply doing that and trying to analyse the results is completely pointless if you have not measured the pipes beforehand to see what the original design intent was.

If the header is short to start with, and you then shorten it more, the tuned length may be perfect, but the negative effect from the now silly short header length will overpower any of the good effects of the overall length.

Conversely if the header was short and you lengthened it, the power increase may be mainly due to now having a " correct " % of header - though the pipe length may be completely wrong for the port timing.

Your explanation makes sense of Fixers dyno graphs. It will be interesting to see a post from TZ with a new (after modification) dyno graph explaining their reasoning for the cylinder plate approach. But it may be a bit of a wait as I hear they have had a woopsie with the dyno computer and need a replacement copy of the Dynojet software so they can commission a replacement computer.

The only way to establish the port timings is to use the STA numbers generated in a CAD program of some sort.

But as I explained before, running the transfers up at 130* would in most cases indicate you are looking to make 50Hp and go to 14,000 in a 125 cylinder with plenty of port width.

In that case 192 is a wild mismatch, no matter what the Ex geometry is, as the Blowdown STA will be tiny in comparison to the transfers ability.

This would mean far too low port velocity in the transfer ducts,where the port then looses coherence of the scavenging streams, and short circuiting kills the power dead – especially if you somehow manage to get a well designed pipe that will suck like hell around BDC.

Then, not to mention we are fighting the huge residual pressure sitting above the transfers as they open - killing even more the flow velocity, due to the restricted Blowdown STA.

I hear what your saying. if I am starting at 180/124 should I just widen the trans as much as I can, raise exh a little and widen it then test and see what happens ?

I do have engmod2t but its a bugger putting in all the info. plus I have not used it enough to decipher the output info

In EngMod all you gotta do is enter the basic engine bore/stroke etc and then the Ex and transfer data, and the front page gives you the STA info.
Tells you in a few minutes all the answers you will ever need.

hey wobbly or anyone else. I have seen what happens with insufficient blowdown. is there such a thing as too much blowdown ?

Its not so much the issue of too much blowdown per se in an engine spec. The real issue is how did the excess blowdown for the planned Hp/rpm actually occur.

Using a CAD program it is easy to see a mismatch between the STA numbers for any combination of port area and timing.

If for example we see really big numbers for the EX and Bl STA but a mismatched small Tr STA then the performance will be transfer limited - and we wont see the power as the BL STA would predict..

Go the other way and we can have big Tr STA and big Bl STA, and this in fact may not be an issue, as in many cases having the TR and Bl correct.

But an under size Ex STA will just mean that a clever person has filled in the EX floor and the bottom corner rads to reduce short circuiting. This scenario will perform as per the correct BL and TR STA numbers predict.

What I was going on about the other day was to point out that taking a cylinder with low Tr and low Ex timings and simply jacking it up, will for sure give a useful improvement.

Simply due to the better timing numbers suited to alot more performance, but having huge 130* transfers and a relatively low 192* Ex points to the engine then being BL STA limited.

Drop the cylinder and grind up the Ex to get all 3 STA numbers complementing each other, and more power than the simple jack up scenario is a given.



Here are the STA numbers for an Athena 50 - one with the cylinder jacked up, the other with the same transfers but the Ex ground up to match.

[TZ350]

Page 940-B

Woo hoo! ... The Team ESE dyno is up and running again after some ... er ... minor computer issues. So we put the RS50 Aprilia back on and experimented with a couple of different adaptors in the exhaust header.



The result ... 130hp at just over 6000rpm! Can't wait to get it on the track.

Seriously its great to have the dyno sort of working again, and its a big thanks to Fixer for his efforts and the donation of a suitable computer. Now at least we are back to being able to tell if something has made an improvement or not.

We will get the proper config file from DynoJet soon and it should all be back to normal.

What I was going on about the other day was to point out that taking a cylinder with low Tr and low Ex timings and simply jacking it up, will for sure give a useful improvement.

Simply due to the better timing numbers suited to a lot more performance, but having huge 130* transfers and a relatively low 192* Ex points to the engine then being BL STA limited.

Because the dyno software thinks its looking at a 2000hp setup not our 200hp one the hp is way over stated but I think the rpm and shape of the curve are realistic.



Well, just like Wobbly predicted we might by simply jacking the cylinder up, we did get what looks like a useful improvement and the dip is no where as bad as it was, but its no where ideal. Interestingly the best run now is with a pipe that was the worst of the 5 pipes we tried before.

We are exploring this cylinder in reversible steps so the next move in following Wobs advice is to increase the blow down STA and we are going to try and do this by Devconning the top of the transfers so they open a little later.

[TZ350]

Page 490-C

Rear cylinder wall in red, as I understand it. Could you offer a potential interpretation as to why this did not offer any gains?

Answers are easy to "get " when you know the effects of the mods.

Cutting away the rear tang support at the base of the cylinder means that the flow thru the reeds then smashes directly onto a flat surface - the piston.

This may seem counter intuitive, in that most people think ( wrong ) that when the piston rises it creates a depression that opens the reeds and it is this that causes inflow into
the case.

The rising piston may make a piston port lawnmower operate, but the vast majority of bulk flow in a race 2T is caused by the pipes diffuser depression, around BDC - when the piston is very much in the way.
This negative pressure ratio at the Ex port is then communicated to the reeds via the transfer ducts , creating flow when the piston is at BDC - exactly opposite to the theoretical scenario.

Secondly - many , in fact most modern engines have the same sharp edge scenario as is shown in the pic of the Honda transfer entry, at the bore. But be aware - Mr Thiel is no idiot, and the Aprilia ( and all my engines ) have a LARGE ball nose radius where the duct meets the bore edge.

This is one of the ideas that last weekend won the National Kart title for KZ2 - 125 against the very best World Cup winning engines tuned at enormous expense in Europe by a French dude called Savard.

We kicked arse - making the pass for the lead by simply having more power down the shoot, and better chassis setup to drive away on better tyres.

Transfer duct length is a very tricky area, in that most times when you shorten this, in effect you are reducing the duct volume, AND reducing the area ratio between entry and exit. This I believe has more effect than the actual "tuned" duct length has.

The other small point I thought of later was that the drop down rear piston support tang, if shaped well also helps to deflect the reed flow sideways toward the transfer duct entry area, and not allow most of it to migrate straight forward and hide under the piston.

I should temper my comments about reed flow at BDC somewhat in that when you watch the tip lift and case depression curves in EngMod you see that the case going negative and the inlet going positive, if tuned correctly opens the reeds very quickly and soon after BDC, thus initiating flow into the case when the piston is still hanging around " in the way ".

But again I emphasize it isn’t the rising piston that creates the inflow in a race engine.

So, as fuel passes inside the open reed cage there should not meet a very big case entry or the flow velocity is lowered too much, then the fuel should go in the easier path to sit under transfer ducts. Is this right?

The amount of inlet flow capability varies from motor to motor with cylinder reed setups.

But I know for example in the RZ400 I had to make the Boyesen ports in the CPI cylinder twice as big and then use a Blaster type piston full of big holes to get sufficient inlet STA to support over 100 Crank Hp.

That engine ended up making 96 RWHP and held up over 90 at 12,000 so when pushing the limits on a cylinder reed you have to use everything available.



Here is a pic of the Blaster pistons in 66mm bore, next to stock Blaster and RZ ,I had Wossner make them for the RZ and the TZ400. Been reliable to over 500Km hard racing so far.

Re the reed flow - yes keeping the reed box duct volume small helps keep the velocity high and in all late model engines you can see the progressively smaller entry volume being redesigned year by year.

I have thought about making a pair of curved vertical guides in the reed box that would direct the flow from the outer reed petals ( in a 6 petal reed ) toward the transfer duct entries.

The center petals then dumping flow onto the big end slot for lube - not had a suitable project yet to try this yet.

So what are your thoughts on making the cases as wide as possible on a case Reed motor? This NSR500 has the case Reed width almost as wide as the transfer ducts in the cases.

I have a cr125 that I'm doing and debating on how wide I should make the case Reed width entering the crankcase, and ultimately into the transfer ducts in crankcase

From what I have seen by various factories the development seems to have been toward reducing the area/volume in front of the reed tips as much as possible - at the expense of what you would think was a "good " flow regime.

But along with that the Italians are lifting the duct floor higher and higher with it sloping upward and transitioning into the flywheel covers, just leaving a slot for lube.

This has also coincided with angling the carb upward, removing any bend in the inlet tract.

That has also given festerers like me endless fun with reed configurations - no longer do we need to bias the flow with differing stiffness and or backups on the top/bottom to counteract the manifold bends deleterious effect on flow.

Has anyone tried adding transfer ports under the exhaust port?

Yes and No ... tried an exhaust port dam, seemed to work OK, as for the transfers under the exhaust port itself, good idea but from memory Frits reported that Jan Theil had tried it without success.

Follow the link trail to read about Ex port floor dams and extra transfer ports there.

Most of us cut the squish angle of our heads on the lathe. With a domed piston which is a radius... the squish angle is slightly mismatched being a straight angle. Any performance benefit to CNC the head squish to match piston dome?

There was one guy in Czech republic who tuned a moped engine to get he's degree at university.



And he did this kind of test, here are the results Blue line piston angle same as head angle and red line domed piston and straight angle head and 2nd picture modified piston to get same angle as head.

The squish following the piston shape by using CNC is even more important if you are pushing the limits with around 50% SAR and very tight clearance.



This also works together with the sharp edge into the bowl, and I suspect that if the tests shown were done with all this in mind the difference in performance would have been even greater.

Yamaha paid a fortune to the sly old fox Dr Erlich for his patented offset combustion chamber, they used it once in the TZ 250 G model, and as we know all that did was deto its tits off due to insane MSV on one side and none on the other.

http://killacycleracing.com/about-us/eva-hakansson/

KillaJoule is the world’s fastest electric sidecar motorcycle with a top speed of 216 mph (348 km/h) so far.
Builder, owner and driver is Eva Håkansson.
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And then there is the 8 second drag bike.

http://media.killacycleracing.com/20...for_slider.jpg

You will have to go and have a poke around the sight if you wan't to know more.

http://killacycleracing.com/about-us/eva-hakansson/

[chrisc]

Page 490-A

490? You've gone back in time Rob!

[husaberg]

Page 490-C

[TZ350]

490? You've gone back in time Rob!

Back to the Future ....... fwk.. ...... anyway the links list from the last 10-20 pages is to go there when I have compiled it.

[Grumph]

Ok here's a question. Kart guys seem to like to start their karts on the stands then rev them. From cold- Revvvv. Brake
Revvvvv. Brake. RREEEEVVVV brake.

What do they think they are doing? They don't seem to be warming them up. They can't be tuning them as they are not to temperature and not under load. What do they think they are doing?

Other concerning thing is the spinning wheels at waist height would take you apart if you walked into them.

If you want to warm up a kart with either direct drive or a centrifugal clutch, holding at a constant rpm is hard - and hard on chain etc.
Varying the speed - bringing it back down with the brake - is actually the best way to do it. But yeah, noisy and irritating.
Old guys' factoid for you dave - post WW2 preselector gearboxes were still in use for roadracing cars. The only way to warm them up - and you had to otherwise they developed clutch slip etc - was to start the car and put it up on jackstands then run it at a fast idle in gear for 10 - 15 minutes. Noisy, dangerous, hell yes. still done by ERA owners in vintage racing too.

[wobbly]

Re the fuel flashing off all its good light front ends.
Next time you go to a gas station have a look around and somewhere you will see several pipes stacked up in a row that are often over 6M high
with a U bend on top so the outlet faces down.
These are the tank breather pipes, and the pressure head created in the tank by this high exit vent is there to contain the vapour pressure of the fuel.
When you have a 1/2 empty 20L container of petrol, within several hours the light chemicals in the fuel will flash off and create the vapour pressure you always
have when opening a drum - this "good stuff " instantly dissipates to atmosphere as soon as you open the tin, and the more times you do it, the worse the fuel gets.
With fuel sitting in a kart tank, and a direct vent to atmosphere as you must have, the vapour pressure exits to atmosphere continuously, so overnight is plenty long enough to ruin the
already suspect pump gas.
The effect is much worse now that lead has been taken out, and all manner of really bad shit has been put back in to lift the octain to 98 especially.
The number of times I have seen mainly KZ2 but also KT100 and Rotax engines detoed to death by this effect is just amazing - but hey what do I know after all these years at the track and dozens of
National/World No1 plates .
The higher the tune/bmep the worse the effect you see from low octain fuel with low vapour pressure, so alot of racers get away with it, alot of the time - but with fresh fuel you can always rely
on your baseline tuning settings, without that assurance you have no chance against the guys really on the ball.

[wobbly]

PS - the only reason you need to rev/brake a kart on the stand is to circulate the water and get the cylinder/radiator up to temp.
This is usually an issue as they only get 1 lap of warmup, but the other side of the coin is that the things go best when cold, so all they really need
is enough to get say 35* into the water.
There are plenty of wqnkers that make us all deaf in the pit for no reason at all.

[wobbly]

Last point about the markings on the KZ2 piston.
Frits pointed out that Aprilia brighly polished the piston to reflect combustion heat so I tried this on a KZ2.
I also tried using a clear ceramic coating ( often used by cheaters in KT100 ) and found that both helped to save the piston
if deto started to eat away the squish.
But no matter what I did it would always then start eating the head.
Once I understood what not to do, deto went away and it became easy to tune to the edge with egt and a magnifying scope that usb plugs into a laptop.

[F5 Dave]

Re the fuel flashing off all its good light front ends.
Next time you go to a gas station have a look around and somewhere you will see several pipes stacked up in a row that are often over 6M high
with a U bend on top so the outlet faces down.
These are the tank breather pipes, and the pressure head created in the tank by this high exit vent is there to contain the vapour pressure of the fuel.
. . .

ok thanks I'm going to have to think about this for a while.


I've been using Av for years now and the airport is miles away so I get a couple of 20l at a time which lasts me several meetings on the bucket. I've never noticed any affect that I could put my finger on in dyno tests with new fuel, but I'll keep it in mind.

[F5 Dave]

PS - the only reason you need to rev/brake a kart on the stand is to circulate the water and get the cylinder/radiator up to temp.
This is usually an issue as they only get 1 lap of warmup, but the other side of the coin is that the things go best when cold, so all they really need
is enough to get say 35* into the water.
There are plenty of wqnkers that make us all deaf in the pit for no reason at all.

We mainly see this on KTs & it doesn't seem to be before the race, just at random times.

[wobbly]

The problem with the KT100 is that the jetting you use on the track is way too lean in the bottom to use when the engine is cold
and being push started.
Those good drivers/tuners can wind out the bottom needle for the first lap ,then take it back in correctly when the cylinder/pipe is up to temp.
But thrashing it in the pits to heat it up is another way for those not so skilled on the needles.