ESE's works engine tuner

[TZ350]

Page 1400 ...

Interesting supercharged 2T:- http://www.odd-bike.com/2014/02/dkw-...force-fed.html Carb Tuning. http://www.3cyl.com/mraxl/manuals/carbtune/carbtune.htm

The "downdraft" Keihin FCR carbs such as:- http://www.ebay.com/itm/KEIHIN-FCR-3...f-9G9A&vxp=mtr

Can one of these carbs be made to work on a 2 stroke engine? They are pretty steep even with the bowl flat and very steep when the bowl is inclined. They are relatively expensive even for one and I need two, so if it's not doable I don't want to waste all that money, but getting the carbs very steep would solve a lot of other problems.

Mine pwm carb is at it's limit, if i alter the angle a little bit steeper it starts to drip from ventilation. Maybe one could make a deeper bottom plug on bowl and make the jets reach longer into that plug, then lower float level.

PWM and some newer PWK´s (Airstriker?) has a new separated idle system from low speed jet. It runs through the choke system instead, throttle is resting dead on the floor, air runs through the choke hole instead.
You adjust the idle with turning the choke knob.

Really neat feature actually =) http://www.pbase.com/jdjetting1/image/43260810

TeeZee: I remember you did some tests on the dyno some (100 ) pages back. Do you still know which page you showed the results? And do you had a chance to use a A/F meter at that time? Juergen

No sorry, but under "Thread Tools" which is near the top right hand side of the page, you can "View Thread Images" and sort them into 70 per page. When you find an interesting image click on the N/A sign to see the post, there are more than 7,000 images.

When I was playing with EFI I did use a A/F meter but with a 2T there are traps as the A/F reading is seemingly rich when the trapping efficiency is not good, like when you are moving away from peak torque or well out of the power band.

The A/F meter accuracy seemed at its best when the rpm was at peak torque, everywhere else it indicated varying degrees of rich but was not.

Frits put me on to this, the indicated richness was just air/fuel being blown through the exhaust port and lost down the pipe the remaining air/fuel that got trapped in the cylinder burnt correctly.

All the air/fuel was of the correct strength for good combustion just some was not trapped and consequently lost and looked to the meter like the engine was running rich when in fact it was not.

Maybe Wobbly or Frits may know the answer to this. ... Curious if any of the V4 500cc 2 strokes ever tried 2 into 1 pipes? Would have improved bottom end and midrange with very minimal peak loss. Plus the sound a 2 into 1 makes... incredible! I built one for my RZ350 back in the day.

No V4 GP engines ran 2:1 but from my experience with World Champ Ski engines the 2:1 doesn't even come close to well designed single pipes, no matter where you bring the headers together.

You can get a big boost in top end power by cutting the piston skirts short on the Ex side. This creates havoc with the jetting, but once sorted it does work well.

I spent a huge amount of time on EngMod trying to replicate or even get close to twin single pipe performance on a hot road RZ350, but simply
couldn't achieve the mid, or top end, with a 2:1.

In twin snowmobiles and those adapted for small aircraft use, the best performance is achieved with a 2:1 when the Ex duration is up at 200*.
But this then seriously affects the powerband shape,as it looses a huge amount of mid power that then needs the pipe designed to get some of it back,badly compromising the top end - just not worth it IMHO.

Edit - here is about as good as it gets, a very good aftermarket 2:1 Vs aftermarket singles.

Were you able to determine where best to bring the headers together and what sort of angle the headers would have relative to each other where they meet?

Most people I know seem to think making the headers so that they come together at the least possible distance from the port, without undue bends is best. It seems to make sense, but I have also wondered if maybe not bringing the headers together until almost the large mid section of the pipe might work so that the pipe header and a lot of the diverging section work like individual pipes and the reverse cone reflects the two.

Building it like that you could say why not just build it single pipes because it would be halfway a single pipe anyway but I was thinking for when rules insist 2:1. Maybe build single pipes and connect the stingers but I think that wouldn't fly with the rules.

Re Vegas - here is some cut and paste from a report on the result I did.

We were top 3 fastest thru all the sessions, but the engine guy for the team we race for didn't tighten the new spark plug prior to qualifying.

Of course it wound almost all the way out and our pace dropped by 3/10s, enough only for 6th.

In the first heat we were up to 4th pulling in the top 3 easily within 2 laps when the 3rd place missed a gear mid bend under big pressure and spun right in our karts path - DNF.

Means we went into the final from 12 on the grid, got to 5th place and ran out of time - track position is everything when only a few 1/10ths cover the top 5 pace.

I took the deto gauge off the dyno and ran the 0-5V output into the Pi data logger, and was very surprised to find that after leaning down enough to get hits, that the only place it deto'ed was the acceleration phase after 2nd, 3rd, 4th gear changes, when dropping back to near peak power after overeving to 12200.

The 5th to 6th change stayed above peak power and didnt deto at all down into the shute. So I fitted the new header with the deto button installed and the gearchange deto disappeared completely. That allowed another 3 jets leaner before it started again.

Get this - the egt at that level was 1390* F with no sign of deto or piston heat stress. This is due to the fuel octane being too high for the com, and the fact that the SKUSA advance restrictor plate does not allow us to add enough static timing to create more power - only pipe heat.

I think I have worked the logic of the deto button - it creates turbulence in the top 1/2 of the duct, allowing the smooth flow along the floor to return easily up the duct and be aimed upward off the ski jump at the closing Ex port.

This came from finding that having the floor of the oval/round transition spigot co linear with the duct floor, and all of the transition angle in the roof made best power.

So here is the jetting chart prior to adding the new header, based on safe deto level, not egt as I would usually use.
The Lambda ( in the muffler ) showed the kart was fastest at 13.8 :1 ( and it hardly varied anywhere within the usable power band ), going leaner or richer was slower on track.

We tested both VP C12 ( 108 octane ) and VP98, the 98 being both faster and easier to tune to the edge.

The original deto mushrooms were installed about 50mm down into the pipe header, but in the SKUSA Honda we cant touch the spec pipe. Whereas the spigot is open except for the overall length.

I was a bit surprised that moving the thing closer to the piston still worked so well, no power loss on the dyno, but I didn't have lean enough jets
during testing to get deto happening.

As the area where the mushroom was installed was less than out in the header I simply scaled it down. But as I said I was surprised to find that the piston killing deto only occurred after dropping back to around peak power from gear changes, and that the change into 6th ( with minimal rev drop ) didn't deto at all in the overev.

It would work just as well in model engines if you are getting deto that eats away the piston in the squish band, but as I see it you are running for
the longest period way into overev, not sitting on peak Hp during flight - so it may not have any useful effect.

The end of the mushroom is step threaded, and this screws into a hole with a chamfer on the outer surface where the pipe sleeve seals.
After installing it I sat it in the press and using a 90* pointed mandrel on centre, expanded the flat threaded end into the spigot chamfer.
I would have preferred to have a small boss within the spigot, but this involved way too much extra CNC time with difficult programming and special tooling.

Ok Frits, how are we going to build a continuous fuel injection system, not pulsed.

The old Hiborn mechanical fuel injection was crude at best but if we were to put a electronically controlled needle valve in place of the return "pill" it could work? Or as you have suggested a DC motor driven by pules width modulation.

I developed the continuous injection idea for a 6,5 cc model engine that revs past 35.000 rpm, so no chance in hell that I would ever find an injector that's quick enough. I decided upon a gear pump driven by a pulse width modulated electromotor and a spring-loaded injection nozzle that I posted here before.

As flow sensors, MAP sensors, Lambda sensors and the like are all too big for this engine, and as it's an unthrottled (always WOT) engine, I planned to use only an engine rpm / pump rpm lookup table. Crude as this would be, it would be an improvement on the present carburation system that depends on a pre-set (before flight) needle and exhaust pressure.

Of course such an rpm/rpm lookup table is totally insufficient if you want any throttle control and rideability.

Frits... There is a very simple non conventional 2 stroke mechanical fuel injection patented by a Barry Holtzman. Its concept may be applicable for your project...

The unit I had was very compact, yet able to feed a 125cc on methanol. It was roughly the dia of an ink pen and somewhere around 20 mm long. It screwed into a 3mm hole drilled in the cylinder wall, which was located so the piston uncovered it about 60 degrees atdc. Output of the injector pump was plumbed into the crankcase.

Engine compression was sufficient to operate the pump for starting purposes. In operation each injection pulse is directly proportional to the pressure of the previous power stroke. It functioned remarkably well. I ended up sending it to a customer for testing and never got it back.

The patent number is US 6725845 B2 Here is a link to Google patents.... https://www.google.com/patents/US672...zDBhsQ6AEIIzAB

Kermit Buller

Hey Kermit, in my view that idea is absolute genius, I hope Miss Piggy gave you what you deserved.

Hello everyone! I have a question concerning auxiliary exhaust ports:

If you have plugged your wrist pin and are on the quest for more exhaust TA - why not make the ports wider than 100% of the Bore?

I have the picture of Frits in mind where the auxiliary ports do not aim directly to the bore center but more to the C-Port.

I can imagine that the scavenging will not work properly as the A Ports will shoot straight in the auxiliary ports, also the returning fresh gas mixture might swirl the cylinder a lot more than in an "conventional" engine...

So... Has anyone made an computer fluid dynamic of this and it seems to be bullshit? Or why was it never (?) done before? cheers! Tim

Re the idea of increasing the Aux ports wider than 100% of the bore.

This was tested even better than CFD - Jan did it with the RSA on the dyno, lost power. I believe due to any advantage gained from the extra blowdown area is offset by the much longer path length for the Ex wave when its past 1/2 way in the bore, and this smears out the pulse amplitude entering the header.

I was asked about Aux ports and spigot design in a PM, and as I cant add pics to a PM, here is the welded duct on a KTM250 with 75% area at the face - 52mm wide by 32mm high, considerably reducing the duct volume in the cylinder just short of going sonic in EngMod ( PS the floor is 4mm above BDC ).

I added the male spigot, so that the oval to round transition could be made smoothly before entering the pipe header.

wobbly: Do you have any more comments or pics of the ktm250 exhaust (in port or portmap) of the work you did? Thanks Jeff

Here are some more pics of the road racing KTM250. It has a long rod from an earlier model with a Wossner flat top single ring piston from CR250, needed an 8mm plate under cylinder that corrected the case com, and got ports close - still needed 2 days of grinding as the ring pinned on centre enabled huge B ports.

The reed is a VF4 off a late model KTM and the inlet length is tuned to 10,000 rpm with a 42mm bored SPJ carb of late model RS250 to use the solenoid PJ for over rev power.

This has a screw adjustable powerjet on a CNC carb bowl. I cut off the kickstart gear housing to get the intake dead straight. Water route has been changed with CNC head and has bronze insert.

The Aux ports were welded then made triangular and twice the area around to bore centre, Ex port floor and corner rads are welded.

Port setup is with B,C highest and set in EngMod for 72 Hp on Avgas.

Servo driven PV is used as it drops over 1500 rpm into 5th gear due to MX gearbox ratios.

Wobbly: Thank you for the pics and reply. If I may, a question about the intake length. It looks a bit long and is the long red spacer block just a transition from the round carb to the square reed?

Another question, from the 4mm build-up at the bottom of the exhaust port, are you adding 4mm of fill the whole length of the port or is it 4mm at the port window and tapering to 0mm at the spigot end? I am building a 250 KTM now for hill climbing and very interested in what you did.Thank you, Jeff

No,and no. The intake length isn't long at all, just remember that the "normal " 250 intake is the same as a 125 - simply so the carb can fit in behind the suspension etc. How can that possibly be correct for an engine that peaks all of 2000 rpm lower.

The built up Ex floor is full length, as the roof is set by the PV blade, and that is flat to begin with.

The red block is simply a spacer to adapt the differing bolt patterns and get the length correct.
The round to squarish transition is done in the manifold rubber.

Hello, i've just read a post on another site in which the poster said" we dropped the compression right down as it enabled the bike to rev higher". Is this correct, less compression easier to rev? less forces on the piston/ conrod/bearings maybe less heat?

once you have your engine on the pipe maybe a conservative 9500rpm with all its momentum would being able to vary the compression (lower) at this peak make it rev more?

Has anyone have any views on this, come across anything, on the net, relating to this? thanks, nigel.

Less compression = less expansion = more heat and energy left in the exhaust gases when the exhaust port opens = higher exhaust pipe frequency.

I suppose one must pose the inevitable question, what is regarded as a high or low compression number within the context of ,say a good 125cc engine?

The actual number of a ratio tells us nothing of the actual quantity of mixture contained in the combustion chamber at the point of ignition.

If there is little in there, squeeze the hell out of it! Perhaps the real answer is a variable ratio that progressively lowers at escalating, higher rpm that provides for improving cylinder filling! Avgas reacts better to a high ratio, unleaded though faster burning is averse to high cr. So what is high and what is low in compression ratios? Trevor

The amount of energy available to the combustion process is finite. How it is distributed is dependent upon the CR , the ignition timing and the squish velocity.

As you raise the com, more energy within the A/F mixture is transferred to the surrounding metal ( head/piston/cylinder wall ) and to raising the gas pressure earlier within the cycle. Thus less remnant heat energy is available to the wave process within the pipe.

Same for ignition timing, spark of the mixture earlier and the same thing as above occurs. Then lastly we have squish velocity - as this is raised the turbulence within the combustion space is increased - thus raising the burn speed, with the same effect as advancing the timing.

With regard to compression ratios in a ( normal tech - not Ryger ) 125, this is entirely fuel and end use dependent. For what we regard as unleaded ie pump gas of the 95/98 octane range we can use around 13.5 to 14.5 :1, the higher number is common for MX where throttle response is favored over outright peak Hp numbers, and thus the bmep is lower compared to say a road race designed engine spec.

This comes back to the effective dynamic compression created within the combustion space by the entire engines design specifics. And for what we regard as leaded race gas ie Avgas the numbers are 15.5 to 16.5:1. Go up to 110 leaded rocket fuel ( or C12/C14 ) then 17.5:1 is commonplace.

As the com is dropped, then more heat is seen in the header pipe as measured by an egt, and this extra heat is created thru the entire rev range - thus as usual, no free lunch ie greater mach number of the gas speed from the higher local temp means better overev, at the expense of course of bottom end.

This can to some extent be ameliorated by winding in advance lower in the rev range - but as many have found,this can create havoc on part throttle use off the powerband.

Re the Ryger patent info - we already know how the top end "works " from an existing published paper, but we still have no idea at all about the 30,000 rpm capable sealed bottom end.

[ken seeber]

Page 1400 ...

but wait, there's more useful stats.......

It's been going for 7 years 16 days = 2555 days which @ 20986 posts = 8.16 posts per day

Well done...a belated happy birthday and a happy 8th Xmas to ESE

And also 17 days to go for the big spreading of the Ryger legs

[F5 Dave]

And the big secret is.
Sex lube.
Good for a 125 to 30,000 at 20:1, and a 14yr olds right hand to 40,000.

[TZ350]

Where all good Buckets start.

A bunch of TF125 farm bike engines just waiting for a good home .... http://www.trademe.co.nz/motors/moto...-995371499.htm

Two seriously good TF125 powered bikes bracketing a fast FXR150:- https://www.flickr.com/photos/sonscc...7659734847064/

[Holeshot]

No doubt this is the best thread on the net. Reading from page 1, im still back in 2009 and page 64, but i will catch up eventually. Thank you all for this incredible thread.

[F5 Dave]

Heck, I feel like I'm still back in 1997. Welcome anyway.

[wobbly]

Previously I said I would post pics of the mods done to the TZ400 that won at the Shorai Challenge, so here are some of the modified head
and new water circuit.
From the pump water enters the rear of the cylinder below the welded on top plate, this forces flow around over the transfers then up into the front of
the head via holes on each side of the Ex duct.
This water is then forced to flow around the inserted head, and out at the highest point, with an auto air bleed back to the top of the crossflow rad.
The 3G3 - 6 port cylinder has an intake bridge added with a boost port cut on each side and ported to suit the Banshee 58mm stroker crank and special single ring
Wossner 66mm Blaster pistons.
After plating the 6mm welded on plate was reduced 2.8mm so that all the squish is in the cylinder with no step on the insert face.
It runs 16.2 :1 com on Avgas with 40mm Lectron HV carbs that are period legal- running into CR125 Reedblocks from VeeForce.
This makes the cylinder the same configuration as the TZ500 factory engine as run by Roberts - pre 82

[FastFred]

No doubt this is the best thread on the net. Reading from page 1, im still back in 2009 and page 64, but i will catch up eventually. Thank you all for this incredible thread.

Check out page 1000 it has a lot of accumulated info there and a bit of a directory to other good stuff on the thread.

[MotleyCrue]

Wobbly, thank you for posting your pics.

I had a few questions about the Lectron carb.

I see it is a Fast by Gast carb and as far as I know they only run 4 strokes there. Did FBG or Lectron set up the carb for a 2 stroke, or did you just buy it as a 4 stroke carb then reconfigure it for a 2 stroke engine, and if so was it difficult?

I have thought about getting Lectrons, I know they come up once in awhile on ebay off of a 2 stroke engine but I can get them easier and cheaper if they come off a 4 stroke engine. There doesn't seem to be much info around as to how difficult it would be to configure them for a 2 stroke. Lectrons don't have a bunch of circuits so it seemed like maybe it wouldn't be too hard, maybe just a needle change, but they cost a lot so I wouldn't want to just end up having them sit on the shelf.

Some people say Lectrons are better than Mikuni and Keihin, but others disagree, what do you think?

[wobbly]

I got one of the carbs off Ebay and it just happened to be an FBG, nothing special about it, they just jet them to suit.
Make sure you get the HV version with the venturi behind the slide.
The only thing to correct or set is the float needle size for gravity or pump feed, the main needle and the powerjet size.
Thing is they flow alot more air size for size than a Mik or Keihin, and the venturi then gives way better part throttle response than
what you would expect from the carb size.
Looking at the Lambda on the dyno they have a really linear A/F ratio, a Mik or Keihin is all over the place as the circuits overlap.
On the TZ400 I started out with a 4-2 needle and a 75 powerjet, this was too lean on top, and needed a 95 powerjet to settle at 650C at full noise.
This is too big, so I went up to a 6-2 needle and the powerjet dropped into the 60 range - that gave a spot on fuel curve to suit that engine.
Only problem I had is that the Frepin frame has the tank very low and close to the carbs, thus the fuel head is minimal above the bowls unless the tank was near full.
The stock gravity needle and seat is a 3mm, so I got the special option 3.6 and this stopped it leaning out as the fuel level in the tank became low.
They do an add on air bell as well that dramatically improves air flow.

[Holeshot]

Check out page 1000 it has a lot of accumulated info there and a bit of a directory to other good stuff on the thread.

Will do thank you sir. I dont want to clutter your thread with my thank you responses. I will lurk awhile. Im constantly sidetracked studying xlnt information and links that were previously posted. Since i started from page 1 this explains my slow progress to catch up to current posts. You guys are all the best company. Thank you.

[J.A.W.]

Wobbly, thank you for posting your pics.

I had a few questions about the Lectron carb.

I see it is a Fast by Gast carb and as far as I know they only run 4 strokes there. Did FBG or Lectron set up the carb for a 2 stroke, or did you just buy it as a 4 stroke carb then reconfigure it for a 2 stroke engine, and if so was it difficult?

I have thought about getting Lectrons, I know they come up once in awhile on ebay off of a 2 stroke engine but I can get them easier and cheaper if they come off a 4 stroke engine. There doesn't seem to be much info around as to how difficult it would be to configure them for a 2 stroke. Lectrons don't have a bunch of circuits so it seemed like maybe it wouldn't be too hard, maybe just a needle change, but they cost a lot so I wouldn't want to just end up having them sit on the shelf.

Some people say Lectrons are better than Mikuni and Keihin, but others disagree, what do you think?

Paul Gast sure does do 2T Lectrons, as he has for decades.. see here.. www.fastbygast.com/H-2%20parts.htm

& they do work, if a bit pricey, but when limited by regs which forbid late 2T carbs, they are the go - as Wobbly has proven..
Mind you, rocking up with a PG H2 race mill in your bucket - might just raise a few eyebrows..

[J.A.W.]

Wobbly, thank you for posting your pics.

I had a few questions about the Lectron carb.

I see it is a Fast by Gast carb and as far as I know they only run 4 strokes there. Did FBG or Lectron set up the carb for a 2 stroke, or did you just buy it as a 4 stroke carb then reconfigure it for a 2 stroke engine, and if so was it difficult?

Yeah, I should've noted, if you go in to 'tech tips' on the FBG site, you can read some Lectron function/set-up info..

[J.A.W.]

Wobbly, thank you for posting your pics.

I had a few questions about the Lectron carb.

I see it is a Fast by Gast carb and as far as I know they only run 4 strokes there. Did FBG or Lectron set up the carb for a 2 stroke, or did you just buy it as a 4 stroke carb then reconfigure it for a 2 stroke engine, and if so was it difficult?

I have thought about getting Lectrons, I know they come up once in awhile on ebay off of a 2 stroke engine but I can get them easier and cheaper if they come off a 4 stroke engine. There doesn't seem to be much info around as to how difficult it would be to configure them for a 2 stroke. Lectrons don't have a bunch of circuits so it seemed like maybe it wouldn't be too hard, maybe just a needle change, but they cost a lot so I wouldn't want to just end up having them sit on the shelf.

Some people say Lectrons are better than Mikuni and Keihin, but others disagree, what do you think?

You could contact Dave at http://www.twostrokeperformance.com.au - he offers the Lectron set up for 2Ts, & ask him how they compare..

[MotleyCrue]

Paul Gast sure does do 2T Lectrons, as he has for decades.. see here.. www.fastbygast.com/H-2%20parts.htm

& they do work, if a bit pricey, but when limited by regs which forbid late 2T carbs, they are the go - as Wobbly has proven..
Mind you, rocking up with a PG H2 race mill in your bucket - might just raise a few eyebrows..

Interesting, everytime I see anything on the internet about FBG its always to do with big powerful 4 cylinder 4 strokes. To be honest I never heard of an H2 and never clicked on the H-2 tab on the FBG site before.