Tuesday, July 10, 2012


This post has been a very long time coming!

I've been short of cash and so things had to slow down. I had been
promising detail as to engine condition after tear down. And the news
was mostly all good. The rings seated well enough and the Wiseco
pistons are certainly tougher than the ancient design cast ART's I was
using in the first iteration of this engine! I can't get the head off
this engine with the engine in the chassis so I decided to buy a fiber
optic scope to get a "good" look at the pistons. Just pull the spark
plug and stick the business end of the scope down the hole. The piston
wash was substantial which of course indicates rich operation. After
busting up two different cast pistons, I was leery about chasing the
main jet way down. Once the engine was out of the chassis and I pulled
the head, it was clear that the jetting wasn't close. The under side
of the pistons showed no color at all. Which means that I was way off
on the jetting. I suspect I have been giving away 4-6 HP for no real
good reason .... other than my lack of skill. Even at that the engine,
at tear down, was at 78 HP with a very linear power delivery. I am
very looking forward to putting this engine back together with
detailed port work, head work and new pipes appropriate to the
displacement. Gary at HPbyGD is busy on the pipes, porting the
cylinders and making new inserts for the head. We are going to try a
knock sensor bolted directly to the head. Gary is encouraged by his
preliminary work on the mule engine which is a DT 200 and we hope will
transfer to the 400. I will have a new base line for jetting to work
from (courtesy Gary) ...... and will watch the plugs and deto-sensor

The reason the bike has come all this way is that Gary has indulged my
maniacal desire to find power to rival a modern 600 (and of course
THAT bar keeps moving .......). My role in development is to ask
annoying questions - which Gary indulges - as he continues doing the
hard work of finding more HP in a reliable design. Tricky at best. The
first role for this bike has always been as a street ride. I am asking
him to serve two gods.

Wednesday, December 22, 2010

Ignition Curve Testing

I will say that I have been a little disappointed with this project for a specific reason.  Though I made "breathing improvements" as I increased the displacement of this engine, the BMEP is actually _less_ than a stone stock TZR250 (117 vs. 121).  All of the torque I have gained has been leveraged by the increase in displacement.  Now 70 HP is 70 HP so the bike is much more fun to ride, but I had hoped my tuner and I were actually making improvements along the way.  (OK I'll stop with the whining.....)

The airbox is gone.  The carburetor bore area is increased 50%.  The reed valve tip area has been increased 70%.  It is my hope that the Jolly Moto pipes are now the restriction to breathing.  I am hoping for a BMEP of somewhere between 145-160 - with torque peak in the 8000-9000 range.

I didn't believe I could greatly index torque with ignition timing, but who knows until you have a whack at it?

This first chart is of all the ignition curves I tested that day.  The Zeeltronic makes it easy, as I can store up to 10 discrete curves at once.  Of course the baseline curve ("Jim") is stored along with 4 more.  Two advanced (approximately +2 & +4) and two retarded (approximately -2 & -4).  I have neglected to mention that I have a rev limiter set at 11,000.  The data point at 12,000 RPM is only to establish the downward slope of the curve past 10,000 RPM.  You will also notice the the advanced curves shade back toward the Jim curve.  It was suggested that under no circumstance did I want more than 16 degs of advance after 10,000 RPM.

Note:  All tests are based on full throttle application.  NOW - I would give you that running all the same tests at both say 1/2 and 1/3 throttle might generate some interesting results ....... I am inclined to "tune" for full throttle and _compromise_ settings to find acceptable part throttle operation.

First up was the -2 deg curve.  I was under no illusion as I was pretty sure less would be less .......

..... and I was pretty much right with one exception.  At about 6700 RPM the -2 shows a 1 HP advantage.  Dyno aberration?  Don't know.  Right at the top -2 gave away about 1 HP.  Not really enough to draw a firm conclusion.  This run was not enough different to make much of a difference.

-4 deg curve test

OK - less advance ain't gettin' me nothin' at full throttle openings.  On to ignition advance.

+2 deg test

Still really hard to see the difference in the chart, but I am clearly now heading in the right direction.

+4 degs test

Now we're slicing the bread pretty thin.  Mostly a 1 HP gain between 9500 and 11,000.

I decided not to advance the curve +4 degs through the mid range.  It was getting me about .5 HP.  I decided instead to mostly mirror the +2 and settle at 16.5 degs at 10,000.

The next chart is a where I was at the begining of the day and where I ended up.

Final Settings Pull

I netted a gain from 6700 all the way to 11,000 - averaging something like 2.5 HP.  A nice day's work considering all I did was tell electrons to do different things.

The jetting is not far off.  Is there another 3-4 HP hiding in this basic set-up?  I think so, but it will most likely  come from jetting.

I just can't get over what those Jolly Moto's did to the 250 engine .......  The 389 doesn't seem too interested in making substantial power after 11,000.  I would like to think that the Jolly's are really holding this set-up back.  With the self imposed 11,000 RPM limit I've set, I will have to find a lot more torque to get anywhere near 150 BMEP. 

Time to set the Jolly's aside and design a pipe to work with this set-up.  The BEST part is that I now have the tools to optimize the new pipes.  It will be a whole new game!

The next instalment will likely be as regards the condition of the engine at tear down.  Stay tuned.  

Power Valve Testing

Yesterday as I wrote about what the Jolly Moto pipes did and did not do for the TZR I thought it would be nice to include a dyno chart.  Well I did have one, but it has less data points than the other charts I have.  Not so worried about that as I am not trying to make any significant comparisons - just show it as reference to where I was (and am never going back to).  More important is the shape of the Jolly Moto curve.  I will say that the only other thing I had done concurrent to the addition of the Jolly Moto's was conversion to the FIII carb spec as per Yamaha engineering notes.  The first generation TZR does not like to have its airbox stripped off unless the carbs are carefully re-jetted.  The RZ350 is the same way.  So did I loose some of the midrange as a result of the airbox-ectomy alone?  Maybe - but I think not.  I can't parse those two changes to be sure.  The chart doesn't show it, but the Jolly's allowed for a lot of over-rev - to 12,000 if I was of a mind - bordering on abuse with stock crankshaft components!  I guess the Jollys are an OK pipe if you're not bashful about high RPM.  Still - I think they are best suited to a track bike and then _only_ if the crankshaft is built to an appropriate spec.  Might as well get out the grinder and widen the exhaust port while your at it.  I think maybe high 50's would be the best you'd get as the standard transfers are pretty modest by 250 race-rep standards.

I need to give Krazy Katt and BDK Race Engineering a big shout out here because they have been a good source of race-rep info.  It has been a while since I've been to the KK website and it seems the dyno charts they had detailing the change to power valve timing _only_ are no longer available.  I believe they still offer a ride in service that swaps out only the standard Yamaha power valve controller (for a Zeeltronic controller).  That chart is what I based my initial setting for the TZR389.  The stock tune 2MA engine likes to have the PV openning "window" shifted down the RPM range.  According to BDK Race Engineering the standard 1KT pv starts to open at 5850 RPM and is not fully open until 10,500.  Look back at the chart above and you will see that the standard 250 engine is _done_ at 9500 RPM.  What were Yamaha thinking?  Just indexing the fully open state to 8550 RPM nets big gains from 6500 to 9500 RPM.  See chart below.

So!  That is the initial logic I decided to go with at the dyno.

To test the logic with _this_ engine, I decided to do a couple of runs to proof theory.  One run with the valves left in the closed position and one with the valves in the open position.  Easy enough to do with the Zeeltronic pv controller.

A few things seem to speak out here:

You might look at the above comparison chart and say "Simple - open the valves at 7912 RPM." and you'd be kind of right.  While indeed the torque curves do cross at approximately that point, there are other things to think about.  First - the electronics / pv motor can't react instantaneously (over a single RPM?!).  Second: and while opening the valves as quickly as possible is likely an appropriate logic for say ........ an RG500 engine it likely isn't for the Yamaha spool type power valves.

It was a mistake to start opening the valves at 5500 RPM.  Look at how the torque curve for the pv closed run (blue) is above the base line run (black) until about 7300 RPM.  That says leave the valves closed until about 7300.

I was closer on having the valves fully open at 8500.  We'll say 8300.

For the rest of the testing the valves were programmed to start opening at 7300 and be fully open by 8300.

Note:  There is an anomaly on this chart.  Why does the pv open run measurably stronger (almost 3 HP) above 8300 RPM when all other conditions were as much the same as I could make them?  Hmmmmm.

next post ....... Ignition Curve Testing

Tuesday, December 21, 2010

Ignition and Power Valve - Dyno testing

It has been suggested that, at the very least, I need to include a picture of the bike so's .....

Very Brief History

Some folks have shown an interest in the big engine TZR project that I have had going for years.  I am not going back to the beginning to recap in detail.  Just understand that I started with a weather worn / low mileage TZR250 model 2XT.  It is very similar to the 2MA, 2ME and 1KT sold in various international markets.  The 2XT was the last of the parallel twins that have the exhaust out the front (unlike the later 3MA).  In stock trim its a great light-weight that is under powered - like nearly all race-rep 250's.  I bought this Japanese spec bike with the full intention of developing it over time in to something that made similar HP to the real-deal TZ250's of the '90's.

Flash Forward

Well finally this summer I managed to achieve very important goals: I reached the 70 HP range, the engine is streetable and is reliable.  The engine nets out at about 389cc's.  I have used a pair of Yamaha DT200 cylinders with a slightly shorter stroke and custom parts to make the cylinders fit.  Much thanks goes out to Gary Davis - HorsePower by Gary Davis for his tireless efforts (welding and machining) and his patience for enduring the endless questions I have.  Yamaha is not known for the robustness of their 2-stroke ignitions (ask anyone with an '84 RZ350!) and so when the Zeeltronic ignition became available for the TZR - I bought one promptly!  The application for the TZR is a nice one in that it allows full adjustability of both ignition timing and power valve logic.  It really only makes sense as for years we could jet/carburate, modify ports and build pipes in attempts to tune our way to HP nirvana, but it is only the last ten years or so when the shade tree tuner has had this critical part of the puzzle.


I looked at a lot of ignition curves before deciding on a baseline to start dyno testing.  The curve for the start of dyno testing this fall, I used all spring and summer (while watching the plugs very closely!).  I was jetted way too rich for most of the summer, but finally this fall I got braver and jetted down on the mains even as daily temps dropped.  I bought a bore scope and have been watching the carbon char - spread across the pistons as I jetted down.  I was cross checking plugs against the piston crowns.

The following two charts are of the baseline ignition timing and the first repeatable run on the SuperFlow Dyno.  Sorry for the display quality of the xls files .......  The black trace is of a stock TZR250.

Another note:  The power valve was set to start opening at 5500 and to be fully open by 8500.

On the street it feels all of a 70 HP engine.  That of course is owing to the fact that the bike now tips the scales at 291 lbs. with 1/2 tank of fuel.  All kind of 4-stroke in the engine's delivery.  I suppose has to do with the shape of the (dirtbike) transfers.  Right now its not the type of engine that demands you tap the gear shift to assure forward motion.  In the spring I was trying to ride it like it was peaky - silly and not necessary with a torque "curve" as flat as Kansas.  The engine is saddled with Jolly Moto pipes designed for the 250.  When the engine was still a 250, the Jolly's really gutted the mid range (by as much as 8 HP) from 6500 to 8000.  Only besting the stock engine's output after 10,000 - holding on 'til 11,000.  Made the bike unpleasant to ride unless you were flogging it all the time.  So 73 HP and change is where the dyno day started .........