Dyno day and the RE5

[wayne]

Fantastic day on the dyno. We had 6 RE5's (new Aussie record) and 1 Norton (also a GT750).

Lots of information, some of it very surprising. It's going to take me a couple of days to scan graphs and let the day sink in.

The dyno guy is well renowned and used to spanner for Mick Doohan. Mick publicly backs his dyno shop.

Phil Aynsley, well known Motorcycle photographer and publisher of several quality bike books was there and photographed numerous aspects of the day. This may appear in a UK magazine as a small feature. Will keep you informed.

For now though, I just have one thing to reveal about the day's top RE5. This is going to have one of our southern state friends crying in his Kentucky Bourbon, but he knew that after he'd made the mistake of selling the bike:

Compression- 142.2 + PSI (figure to be refined on close examination).

Edit: on close examination, of the last 7 peaks, 5 are right on the 142.2 line and the the last two are actually above it. The zero reference is spot on. If I'd let it run longer, we may have had even higher compression. Call it 142.2. Highest I've ever heard of.

Power- peak run was 49.92 hp !! This is almost 3 hp more than the journo's were getting on new bikes in '75 and it was 5 hp more than the next-best contender.

This bike, I've said before, has it all. It handles, it has PERFECT carburetion and is significantly more powerful than anything else I've ridden. The Dyno proved it and here's one Steve Thompson, already well known as "MR Waterbottle" and now a very happy owner of what is possibly the world's #1 RE5.



Left to right, myself, John Steain, Luis Gallur, Steve Thompson- Phil Aynsley photograph. Note that only John and myself are in "uniform" polo shirt. You others, the transgression will be noted in the club log !



All very interesting. Kim Hunter (Norton) in the foreground, Clyde Ikin background left, Dyno Dudley second from right- Phil Aynsley photograph:



Luis Gallur's- if nothing else, he reckons he had the shiniest bike- Phil Aynsley photograph:

[hunter]

Fantastic day, Interesting results. Thankyou Wayne for organizing. Just bit sad I could not get my Hercules there as well.

[wayne]

Yeah, and didn't that Norton sound fantastic at redline.........like you'd imagine a rotary to sound......turbine !

[hunter]

Was great sound and considering the owners' handbook claimed bhp of 79 was @ 9,000 rpm, we could have gone further. We got 65 bhp @ 7,500 rpm which was the marked redline.
The RE5s sounded great too at redline.
Look forward to your summary of days results.

[wayne]

Preliminary results from our day at Dudley's dyno shop. Compression is mostly directly related to peak horsepower. I have ridden all these bikes and ranked them by seat-of-the-pants (see Bathurst rally thread). I misjudged where one of them. I had compression readings for three of the bikes and checked the other two on the day.

Note, the #1 and #2 bikes had stock jetting and no carb issues. The 3 and 4 bikes had big primary jets which effectively solved carby issues and the #5 bike was deliberately run with stock jetting to ensure that it had the hesitation. Because of the way the dyno session was done, the whole hesitation thing is irrelevant. It's picked up in the graph but has no effect on final horsepower. When a larger jet was put in the #5 bike to return it to hesitation free, total hp dropped.

1: Steve Thompson’s red M: 142.2 psi HP 49.2 (the 49.92 explained later).

2: My red M: 130.0 psi HP 44.7

3: John Steain’s M/A hybrid 136.9 psi HP 42.7 dropping to 41.2 with rising engine temp.

This was a big surprise. On the road, I ranked this bike as #2 and a compression test on dyno day backed this up returning the second highest reading. In rollon’s it leaves other RE5’s (‘cept Thommo’s) for dead......a couple of bike lengths against the 44 horse M, but something like 8 to 10 bike lengths when up against the 41 horse below. The dyno guy said that was probably because this bike reached its peak horsepower earlier and unlike all the others, held the power to redline. However, this bike does have issues. On the day, it burned 250 cc of sump oil in 150 klm and this has been its habit for some time. It had a failure of the oil line check valve a couple of years ago and ran up to 1500 klm without injection oil. Although it seemed to have survived and the check valve was replaced with one of Jess’s new designs, it’s obvious that something is not quite right anymore. Another thing with is that it had a significantly large drop in horsepower as the bike’s temperature rose (3.5%). This wasn’t as obvious the others.

4: Luis Gallur’s blue M 116 psi Horsepower 41 (40.98)

5: My A model 109 psi Horsepower 40.2 (39.2 with larger Primary Main Jet).

This last bike is the only one to have significantly variable compression across the 3 lobes. Actual figures are 104/108/116. All the other bikes are so close it’s nearly impossible to discriminate on the graph. Call this an average of 109. Note that more learned people on this board have advised that factory guidelines were lobes within 10% and acceptable to 15%.

The sixth RE5 wasn’t dyno’d.

Note the relationship between power and compression except for John. Interestingly, other than the 49 hp bike, all the others are very close on the road. In a roll on, as mentioned, John’s bike will leave the others for dead but in general riding, it’s pretty hard to pick one from the other. I’ve had people rank my A above my M but I’ve had the advantage of thousands of clicks on both so I guess I’ve got a finer tuned wrist for them both. I could feel that I had more throttle on at any given speed on the 40 hp A model. Also my M carries the full tour kit and riders not used to it are really put off looking through a screen.

Going back to the compression guideline thread, it shows that even at 109 psi, you still have a very rideable bike which is almost indiscernible from more powerful engines when on the road. Jess notes that anything over 100 psi is still good for many enjoyable miles.

On the subject of the grinding vibration. Dan (bdalameda) told some time ago how the factory mentioned that this was a torsional harmonic. He noted how it is transmitted through the primary and into the transmission. Forgive me if I remember this incorrectly, but I recall it even being visible in the final drive chain (?).

Turns out it is visible in the final drive chain. My red M probably has the worst grinding and it is the highest mileage bike. Through several runs to 7000 rpm as the bike passed the grinding harmonic band (~ 3800 to 4000) you could seen the unloaded length of the final drive chain go from smooth to a violent whipping and back to smooth.

This was far more noticeable on this bike but was discernible on the others as well. While I say that the grinding is greatest on my M, it also has the 530 chain so I wonder if they are more prone to the whipping (?). I have the chain reacting to the harmonic on this video at 1:17-



I believe that this harmonic is a feature of the engine based on related factory comments and information I've had from more than one Mazda mechanic. It also seems that the RE5 design exacerbates the transmission of this harmonic with a relatively long primary and final drive chain. It also makes sense that as components wear, any transmission of the harmonic is amplified and this seems borne out by the mileages on the tested bikes related to the severity of the perceived harmonic. Highest mileage bike = worst perceived vibration.

I'm sure after spannering for the likes of Doohan and Magee, Dudley's Motorcycle service and performance centre NEVER imagined something looking like this on the ramp. They did it, they just probably wouldn't ever admit it !

[ap951]

Thank you Wayne, I learn a LOT from you

looking at the pictures and reading the posts makes me wish I lived in Australia so I could hang out with you guys

[wayne]

Much appreciated.......thanks.

[wayne]

Gentlemen, see this video of the day, mainly for entertainment but about 1:17, you'll see the chain whip associated with the grinding harmonic.

We had one of us watching the tacho and signalling at the harmonic rpm band to verify that this is what we were seeing.

It was repeated over several runs.



EDIT: For everybody's peace of mind, I think I better clarify some footage in that video that may look disturbing. We had a doctor with us (Luis) and he examined both riders and said that while it looked bad, neither rider was seriously hurt (I take that to mean no spinal or brain injury). The Old Pacific Hwy north of Sydney was once considered one of the top ten rides in Australia. Due to motorcycle deaths, the speed limits have been reduced to 80 and 60 kph but it's still a fantastic road so close to the city.

[hunter]

Great stuff Wayne.. They sounded good, But didn't that Norton squeal?

[Al Corelli]

You guys sure seem to be having a great time.

Nice to see that many RE5s together.

[gerryggg]

Fantastic pictures and video! I haven't seen that many rotaries together since the late 70s when we had 6 in the shop at the same time. I can't wait to get back to work on mine (actually trying to make one good one out of two). I've only seen one running rotary in the last 20 years around here. I wish I could make it "down under" or over to the UK where they seem to be much more plentiful and appreciated.

[wayne]

Fuel/Air mixtures.......now it gets really muddy. Typical RE5.

Unless I specifically state, nothing below is my opinion. It's what I recall the Dyno guy told me. So those of you out there who know more about these charts are welcome to jump in with interpretations.

Note that these graphs are at full throttle so we're not looking at the hesitation, it's a broad brush of the general performance. Dyno guy suggested I come back with one bike and a bag of jets and we'll go through the whole rev range and look at it in detail.

Broadly speaking, four of the five bikes ran too rich and would benefit from smaller SMJ's. This is backed up by our spark plugs. I once gave one to an old board member who showed it to four stroke mechanics who had a flip out (too rich, it would blow black smoke etc etc). I had taken that same plug to a Mazda shop and they shrugged, said it was a bit rich but rotaries tend to be (and the bike runs fine returning up to mid 40's mp imperial gallon).

Now the anomalies. The two perfectly running bikes had very similar graphs and were in one case, totally stock including air filter (WayneM), the other is totally stock but using what I believe is one of Sam's red racing filters (SteveM).

Both of the hesitating bikes which have been "fixed" with larger PMJ's ran leaner but still on the rich side of ideal- go figure. EDIT: Both bikes had a 100 PMJ but one ran leaner (John) and was the only bike close to a good fuel/air mix. Both ran Jess's grey filter.

The bike that was jetted deliberately to hesitate with an 87.5/180 combination (WayneA) ran the leanest of all and was too lean. This figures on one hand and makes NO SENSE on the other. This bike runs hot- always to the right of the middle mark. In my SMJ thread, I noted that in the end the only difference I got from using a larger SMJ was that the bike ran cooler. Makes sense given what the dyno showed. BUT......it is an NOS carby identical to WayneM in jetting and AP set up yet it runs considerably leaner and uses a filter that should give at least the same air flow and at worst be MORE restrictive (ie richer).

We did two runs on this bike (WayneA). One with 87.5 and then I changed to a 102.5. The former gives a hesitation, the latter eliminates it 99% of the time. Dyno guy came out with the graph and said "you put in a larger air jet right ?" Nope, larger fuel jet. "No, the run was leaner, you changed an air jet". Nope, trust me.....I had to take out the brass screw to show him fuel pouring out.

Anyway.......I'll start with my M model graph because it is the clearest to show the richness and the effect on power. To clarify, this bike is totally stock to the latest specs. PMJ/SMJ is 87.5/180, Air filter is original NOS Suzuki, AP is Bulletin 9 at 28 degrees.

By the time the graph starts, from my own investigations, the Port valve is open, the accelerator pump has already done its thing. The throttle is wound fully open on the rolling road dyno.

Upper line is power, lower line is fuel/air mix. Note the fuel dips well into the RICH range and this is matched by a flattening of the power curve. After that, fuel moves towards the "ideal" but only nears it right at 7000 rpm. Dyno guy says that putting a smaller SMJ, around 10 to 15% less fuel flow would flatten out the dip in the early power curve and improve overall horsepower. However, read below the graph.

If you're running windows, hold down Ctrl and then hit + or - resize the screen to better see the details.



I just don't know enough about rotaries and our dyno guy is a two stroke/four stroke expert. Perhaps the richness is designed to keep temperatures down ? I wouldn't go rushing out to put in smaller SMJ's just yet. Perhaps you rotary mechanics out there could comment ?

[goandy]

I was led to believe that rotaries tend to be tuned leaner EDIT** I meant RICHER** for a couple of reasons.

One is that they tend to run very high exhaust gas temps due to inefficient combustion, so running leaner may start melting exhausts.

The other is that they are not very tolerant to pinging from being too lean. Side seals and apex seals can break fairly easily from a good pinging session.

Good write up there on the dyno session by the way! Hmm, I might have to whip out the die grinder and "clean up" my ports a bit more now.

I'm guessing that all the bikes are cranking at about the same speed? That affects the compression quite a bit.

[wayne]

Thanks Andy, good to hear from as many people as possible with actual training and hands-on.

I take your point if that is the case. Why I finished the post with the thought that I won't be rushing out to buy smaller jets just yet. Also, never thought of the pinging issue. This does make me worry about my lean running bike though.

I'll post another two graphs which have interesting points.

With regards to the compression tests, all the bikes have either new or near new batteries bar the 109 psi A. All of the others crank briskly and while I didn't take tacho readings, by sound, they were all healthy spin overs. The A model is adequate but I should hook up a new battery to it and just compare.

I'm also sending our dyno guy a copy of the carb section of our manual so he can get his head around it before any of us go back.

[bdalameda]

Back in 1975 Suzuki taught in the service school that the rotary needed to run lean for a couple of reasons - They charted the intake timing vs a piston engine and it showed the intake cycle of the rotary engine was much longer than a piston engine. If the fuel mixture was too rich the fuel economy would be much worse than it already is. Also being that the rotor was made of steel and cooled internally the engine could be run very lean without damage. The final reason for lean running was to reduce deposits on the rotor and seals. Leaner running kept the apex seals clean and free.

Dan