ESE's works engine tuner

[gamma500]

Hi Frits, could you explain those numbers at bottom of the A-102Fos pipe drawing

from your Aprilia files?


Lsz=0.427? Vol=32.6(pipe volume/cylinder volume?)/46?

iso=1? nL=13036, nD=13035 and nT=13035 must mean max power rpm?


Btw is there any power difference between A-102Fos pipe and Aprilia pipe 102?

[F5 Dave]

Thanks for the thoughts about restrictions relating to power output Wob.

Thanks for the pics again Frits.
I have been using an old RS pipe & there is a connecting area so I have machined up a few shapes pretty much as above. Only issue that had me thinking was that my stinger tube was 23mm & for a 100cc my restriction was 18mm so it was diffusing 5mm instead of suggested 1.5. I wasn't having much joy with the 18 & really didn't see much change between 19 & 23 straight pipe, but I really need to get my next pipe on the dyno & retry but I'll start with 19 & go from there & try match a stinger pipe closer to 1.5. Clearly as power levels make steps up (I'm on interim get-me-going arrangements) I'll need to retrial.

Changing the stinger to match is the hardest part though. Pity you can't just buy different size thin wall tube by the foot.

[speedpro]

Changing the stinger to match is the hardest part though. Pity you can't just buy different size thin wall tube by the foot.

Make your own from say .8mm sheet. If you cut it nice and straight on a guillotine it comes out very nice. I have a good selection of different size axles which I form it on. Once welded it typically jams on the axle but a bit of smashing it with a rubber mallet soon frees it up and leaves it looking good. I form a lot of stuff from .8mm sheet - exhaust mounting brackets, brake stay arms, engine mounts. I have a couple of lumps of steel for beating it over and getting it flat so it welds up nicely.

[Gigglebutton]

Quick question for all you wise ones out there. Should be a little more simple than what has been going on for the last month. Finally got around to trying to tap out the head studs which i ripped out two months ago. No worries except I also ripped out the one which I had previously tapped out to 10mm. Which is a slight delima as there is buggah all room left to go much bigger. So could I get it welded up and then re-drill it? or should I just devcon it back in....

as You can see in the pic I had a channel machined around the liner, to fit the head gasket/o-ring. This means there's not a whole lot of room around the studs.

Attachment 252550

I have Helicoils if you want to bring it in

[Bert]

Quick question for all you wise ones out there. Should be a little more simple than what has been going on for the last month. Finally got around to trying to tap out the head studs which i ripped out two months ago. No worries except I also ripped out the one which I had previously tapped out to 10mm. Which is a slight delima as there is buggah all room left to go much bigger. So could I get it welded up and then re-drill it? or should I just devcon it back in....

as You can see in the pic I had a channel machined around the liner, to fit the head gasket/o-ring. This means there's not a whole lot of room around the studs.

Attachment 252550

I have Helicoils if you want to bring it in

Get it correctly welded up (this may require drilling it out larger to give a better welding surface) and re-cut the o-ring channel and plain everything true; the poor old barrel is suffering from age and crap alloy.

i chased all sorts of "fix's" on my TF head and at the end of the day I wished I'd fixed the bloody thing correctly in the first place. nothing worse than having your day ended by a popped helicoil or duraweld coming apart.
but when you do sort it out; 24hr Araldite in the studs (I think that came from speedpro??) never had that issue again (if you are running an o-ring then you shouldn't need to torque the ass out of the head anyway)...

[speedpro]

Buy a good torque wrench and use it. Welding is going to cause all sorts of distortion and maybe even seperate the aluminium from the liner. A helicoil inserted using a drill press to get it dead straight and square should be fine.

[Gigglebutton]

We use loctite retaining compound on the helicoils to help retain them.

We have welded barrels in containers filled with water to help minimize the heat affected area

[TZ350]

Just add another nut to the end of flywheel, then you can add a bolt that secures the degree wheel. Pointer must be secure (I use a clamped on scriber) & degree wheel should be as big as possible.

Barrel must be bolted down well or gives incorrect readings, this can be a problem if engine has thru bolts & a few gaskets used. Use feeler gauge to determine if port is closed by piston, doing it by eye is imprecise.

When starting with another carb just pull the mainjet out, no point putting a big one in. If the engine doesn’t bog past ½ way then the needle is too fat.

Ha, just for giggles I re-read the first page back in 2008. Post 5 for me & I'm probably still spouting nonsense.

I thought you were offering good advice, still do ...

[husaberg]

although no one has accused anyone of being like Hitler (although maybe that did occur & I've forgotten).

[edit]
Ha, just for giggles

Found this TZ quotes Hitler in engine development kind of anyway. Note he was on to the exhaust venturi as well. All on PG 8

From Koba,s post, and Goggle I have found some interesting info on air cooled motors. Before the "War" in some circles water cooling was considered inefficient, unreliable and expensive. This is the era V-Dubs come from.

Before the "War" Hitler had the Autobahns built, this was before there were fast cars. Then he encouraged the car makers to build Autobahn cars. They were often air cooled and very aerodynamic. There was an air cooled 3.8l V8.

In the 80's when large wind tunnels became available some of these old cars were tested and their drag coefficients (and fuel consumption) were lower than modern cars.

A quick intro to Mackerle. Julius Mackerle was the chief engineer at Tatra motorworks for many years. Tatra make a lot of air cooled vehicles and trucks. Mackerle published a huge amount of interesting air cooled engine information in a book of his called Air-Cooled Engines.

The interesting thing is that the air cooling was effected in different ways.

There was the V-Dub style cooling fan

Another device like a turbo charger that was spun by the exhaust gas and the fan compressor sucked or blew the air through the cooling fin ducts.

And a ventuire ejector system that also used the energy of the exhaust gas to sucke the air through the cooling fin ducts.

I am not sure about the difference between a venturie and a venturie ejector. But I think a venturie is like a motorcycle carb's needle-jet/choke arrangement. Where a small pipe leads into the middle of the venturie's choke and a venturie ejector is more like the old vaccume cleaner spray paint gun?

A venturie ejector is used where shifting bulk is the aim.

Here is an abstract from a US Patent.

Venturi exhaust cooler Document Type and Number: United States Patent 3875745

"The kinetic energy of the exhaust gas from an internal combustion engine is utilized as a driving fluid to aspirate a large volume of quiescent ambient air as a driven fluid for cooling the exhaust gas quickly in a very short path of travel. This mode of operation is to be distinguished from conventional injector and ejector devices utilizing a current of air as the driving fluid. The present device utilizes the Coanda effect to introduce the exhaust gas around a lip on one end of a venturi tube, causing the gas to flow in a high velocity film adherent to the inner surface of the tube. This laminar flow draws in a large volume flow of air through the center of the venturi, cooling 1000°F. exhaust gas down almost to ambient temperature in a distance of a few inches."

I have seen on some modern expansion chamber designs, that the stinger has changed to a restricter that looks like a venture with a tail pipe, makes me think this could be made into a venture ejector.

The good thing about using the energy in the exhaust gas to do some work, is that it quietens it like a muffler does.

A ventuire ejector might have possibilities.

.

[Farmaken]

Hey Tz, having used both these sims, do you reckon they give similar outputs for the same data input? Seems that Engmod is alot more involved and requires far more data input from what you have posted so far, but having ordered Mota the day before you listed your copy for sale was curious about your results so far.
Cheers Ken

[wobbly]

Problem with Mota is that in many cases the data cant be entered correctly,and there is now no backup or updates.
Engmod is way ahead in accuracy due to the extra work needed on data entry, but also is way ahead now due to the constant updates and refining that Neels has
been doing.

[TZ350]

Hey Tz, having used both these sims, do you reckon they give similar outputs for the same data input? Seems that Engmod is alot more involved and requires far more data input from what you have posted so far, but having ordered Mota the day before you listed your copy for sale was curious about your results so far.
Cheers Ken

Mota's good I learnt a lot from using it, you won't be disappointed.

My opinion of Mota vis EngMod2T

I couldn't get Mota to mimic my engines real dyno curve as well as EngMod2T does but Mota did show the general shape and rpm range although it over stated the power.

Mota was good at showing what effect a change was going to have and it did allow me to find the port timing and shape and pipe dimensions that best suited my engine. With Mota's help we got an old Suzuki GP125 into the high 20's (28.9 rwhp which must be over 30 at the crank) so it can't be all bad.

Mota also has some nifty side applications for developing curved multi section pipe cone templates that we found very usefull.

Being an integrated package I found Mota very easy to get started with where EngMod2T is spread over three main applications and two sub apps like a Mota to EngMod data file converta. EngMod took a little getting used to, but now I am starting to know my way around it I find its very easy to use too.

Mota vis EngMod2T is like comparing Jennings port-time-area work with Blairs work at Belfast University, Blair and Neels EngMod2T are a generation or two ahead and incorporate a much more developed understanding of 2 stroke behaviour, but Jennings and Motoa are still very useful for a basic understanding of tuning 2-strokes.

On the negative Mota only deals with a single exhaust port EngMod2T can handle a triple port and has other refinements like a convergent cone stinger nozzle, a rpm dependent variable pipe temperature, much more sophisticated combustion modelling amongst other better developed features. Also the range of information available from EngMod2T's output like the STA values and detailed graphs are streets ahead.

Yes I think EngMod2T is more accurate (by a mile) and produces much more information than Mota but Mota got me to where I am and EngMod2T tells me I am about as far as I can get, with a little EngMod polish there may be another hp or two but with the 24mm carb 30 rwhp is about it for my engine.

[Farmaken]

Thanks Wobbly and TZ for your thoughts, good to know Mota will give a fair idea of the expected HP amd torque curves even if they are a little optimistic !!

Have been playing with numbers for my TF engine - hoping for 20+Hp from 9000 to 12500 with peak power of 26.5 at 11500

Plugged numbers in as I had it running at Taupo and got data output which seemed to correspond with how it felt on track - peak power 17 Hp at 9000 then nothing from there on.

No wonder it was easy to ride on slicks in the wet

[TZ350]

Thanks Wobbly and TZ for your thoughts, good to know Mota will give a fair idea of the expected HP amd torque curves even if they are a little optimistic !!

I probably could have got Mota closer to the real thing by playing with the combustion efficency and other variables more but it was the shape of the curve and how it was affected by changes to the engine/pipe/inlet that mattered more than the displayed hp numbers.

[TZ350]

if these pesky two strokes get too fast I guess we can always get the four stroke limit bumped up to 200cc? Sounds fair doesnt it?
MotoGP went from 500cc two strokes to 990cc four strokes, MX has 125 2 strokes racing with 250 four strokes ...

Yes 125 2-stroke vis 200 4 with a 24mm carb restriction and air cooling only, same rules for both, sounds fair to me.