V45 Sabre on the Dyno ===================== ---------- Author: Robyn Landers rblanders@math.uwaterloo.ca Revision: 1.1 (September 1995) change: it was a Dynojet dynamometer, not a Dynotronics. Copyright: by the author. Reproduce only if this header is included. ---------- In September 1993 I had my '83 V45 Sabre on the Dynojet Dynamometer. Why? Because I'm tiring of the Sabre and lusting after a new VFR, but the VFR is rather pricey. If a pipe and jet kit would boost the Sabre's performance appreciably, I might be content with the Sabre for a couple more seasons while saving up for a VFR. See accompanying JPEG images of the dyno graphs. (I had to enhance them with thicker lines for the scanner to pick out the details, so that's why they look kind of strange.) Initial Conditions ------------------ As far as intake, engine, and exhaust are concerned, my Sabre is completely stock. Since it's a relatively old bike, the suspicions were that it could benefit significantly from a freer flowing pipe and jetting to match. Also, a Dynojet kit typically improves throttle response because of its faster acting slides, in addition to whatever the jetting does. My desire was to improve midrange power and throttle response. If that meant giving up some top end power, that's okay. Real world use is what matters to me, not race track use at 10K rpm. Also, I refuse to use a very loud pipe, so any aftermarket exhaust systems I'd consider would have to be reasonably quiet. Aftermarket Exhaust ------------------- The news here is generally bad. The Sabre is so old and forgotten that there's not much out there for it anymore. My tuner recommended Kerker. I called them, and they offer only one system for the V45 Sabre, their basic no frills black model. Also they told me it is now discontinued, and there are only about 40 of them left in Kerker's warehouse (plus whatever some dealers might have sitting around). So, any replacement parts that aren't common to other Kerker pipes will not be available. Because the product is discontinued, the sales guy had no information to give me (i.e. any of their specific claims for weight, power output, etc are not on file any more). This adds up to being too risky for me. Besides, I'm not too crazy about Kerker's black systems. They seem pretty quick to rust. I also tried Hindle, Wolff, SuperTrapp. None of these offer V45 Sabre exhaust, either slip-on or full systems. Hindle does still offer a V65 system though. My tuner said he could adapt a slip-on to fit, though, so if I wanted a SuperTrapp for example it could be done. The suspicion was that the stock mufflers are restrictive enough that even just replacing them with freer flowing slip-ons would help. DynoJet Kit ----------- The DynoJet catalog I saw mentioned only the VF750 Interceptor, part number DJH 1108, so I called to inquire further. They do offer both Sabre and Magna kits too, DJH 1119 and DJH 1112 respectively. Because my bike is a Canadian model, the jetting will be slightly different, so they referred me to the Canadian distributor who apparently adjust the kits to suit Canadian bikes. Dyno Time --------- I went for the whole dyno treatment, including exhaust gas analyzer and several dyno runs for various tests. We did not do any air box experiments (such as running without the air box snorkel or lid). The EGA showed my idle mixture settings weren't quite balanced, so we adjusted that. It also showed that the bike was set up for fuel economy and emissions politeness, not surprisingly, but the readings were within expected values, so at least the bike wasn't way out of whack. A 4th gear idle-to-redline run was done to measure horsepower versus RPM. The curve was very smooth and steadily increasing, with a peak of about 65 hp at 9000 rpm. Honda claimed 82 HP for the Sabre, at the crank, and a 15% loss is generally expected by the time it reaches the rear wheel, so 65 isn't too far out of line. Interestingly, the Dyno said the engine was doing only 9000 rpm when the bike's tach claimed 10,000 rpm (redline), so we did another run running past indicated redline. Power dropped off suddenly, so it seems there's a sort of rev-limiter or at least intentionally retarded ignition timing built in to the ignition system to prevent over-revving. The absence of any significant dips or peaks in the horsepower curve showed that the jetting was pretty good over all, so we don't have any big problems to fix. Next we did two runs in second gear. The first was an idle-to-redline run. The next is a "slide" test, that tests how the carb slides respond to sudden throttle demands. Here, you hold the bike at 30 or 40 mph for a while then suddenly crack the throttle and run to redline. Ideally, the two curves should superimpose from the midrange up. On my bike, the slide test curve never caught up to the full RPM curve. It was down by a couple HP throughout. This says that the slides respond slowly and never allow full fuel supply to be achieved in a sudden roll-on, so a few horse power are lost in a roll-on situation. The DynoJet kit should solve this nicely. Following this we did an all gear run. This plots HP against MPH, starting at idle in 1st gear and going through all the gears as hard as possible. Ideally you'll see a series of flat-topped segments of equal height, separated by narrow deep dips (during shifts). The segments should be equal in height to show that full HP is developed quickly in each gear. On my bike, each of the segments had a sloping top. This shows that full HP is not quickly developed, but rather the carb responds more slowly and so HP takes time to build in each gear. Also, while 2nd 3rd and 4th were almost equal at their maxima, near 65 HP, 5th and 6th were much lower in overall power output. This suggests that the carb is over-fuelling in the higher gears where acceleration is slower, since it is biased to perform well in lower gears when you accelerate quickly. Finally, to test whether or not freer flowing mufflers would help, we did a run with no mufflers on the bike. The stock header and collector was of course still attached. If a large difference was noticed (which would be a loss of power from running too rich with no mufflers), we could expect that almost as much power could be gained with a free flowing exhaust plus rejetting to suit. In fact, only a couple HP were lost throughout the RPM range. It turns out that the stock mufflers flow reasonably well, and any restrictions are happening farther up in the collector, or are dominated by carb or air intake. You can see just by looking that the Sabre mufflers have a fairly large diameter unobstructed passage through them. We also looked a some Katana 600 mufflers, and the inner pipe was very narrow and pinched off. Couldn't even see any light through them, unlike the Sabre. This was a valuable test, then, because it told us that spending money on aftermarket slip-ons would be a waste. So, the conclusions from the dyno testing were: a) no serious flaws in stock jetting to be corrected b) if we want to play with exhaust system, it would have to be a complete system to do any good, and there aren't any out there for the V45 (unless you want to risk the Kerker). c) a DynoJet kit would still probably prove helpful in improving midrange roll-on and throttle response, and perhaps also in higher gear power output. Other things we talked about but didn't pursue included a) top end refresh (3 angle valve job, bump the compression a bit) b) degree the cams (I've already had the sprockets slotted but have never played with adjusting them.) Conclusions ----------- I will be calling the Canadian distributor of DynoJet (Action Accessories) to ask about their modifications to the Sabre kit. At this point I'm more interested in saving up for a VFR than in sinking lots more money into the Sabre, but if a VFR doesn't happen in the very near future (not likely to) I'll probably try the DynoJet kit, which lists for about $150 Canadian.