Dyno Results the Asian Fit/Jazz VTEC

The amazing Honda Fit / Jazz is quickly turning out to be Honda's most popular, most successful model of the modern era. Its recent launch and success in the U.S./Canada market has again confirmed the excellence and timelessness of this excellent design. More importantly however is the fact that while Honda desperately fights a constant and not entirely successful battle to retain its large fanatical fan base and restore 'lost' excitement to its core models like the Civic and Accord, the Fit/Jazz has since gardnered an incredible fan base, with an enthusiasm that brings back fond memories of the incredible fan fever that used to be enjoyed by great Honda models of the past like EG-Civics, DC2 Integras, CD-Accords and so forth. I have always felt that from the hard-core enthusiast's point of view, this enthusiasm, this fever, have been steadily eroding with Honda models of recent times and if Honda is not careful, its highly likely they will lose a large portion of their fanatical fan base. The Fit/Jazz however is the one of a very few modern Honda models which have not only gained a huge fan base, but have also cultivated a feverish enthusiasm in that fan base.

This article is a continuation of the Fit/Jazz feature series that I started last year. I wrote 4 articles for this series last year, starting with a look at the original design objectives of the Fit/Jazz, then a technical overview of the new L-series engine, a photo-gallery of the L-series engine and then I published my full review of the Jazz VTEC as sold in Asia.

In this article, I decided that its time to make a move 'back to basics', TOVA basics that is, and that is by a close look at one of the areas most important to Honda fans. In this article, I take a look at the crucial question 'how much does the Fit/Jazz VTEC deliver on a dyno'. One cavert is that the cars dyno'ed in this articles are Asian versions which are built in Japan (though I'd expect the Thai built ones to deliver identical results). Also they are running on the CVT-7 gearbox as unfortunately the 5MT Jazz is not universally sold throughout Asia, certainly not in Malaysia so I do not have an opportunity to dyno-check this version.

A very important acknowledgement needs to be made first. This article and subsequent ones like this will not be possible without the generous support of our latest sponsor, JC Asia Motorsports or more popularly known to Malaysian Honda enthusiasts as AMOIL Motorsports. Its owner Jackie is very generously sponsoring free dyno checks of all review cars that I will be taking from Honda Malaysia. This means that I no longer have to worry about financing for dyno-checks and that I will be dyno-checking ALL the cars I will be taking from Honda Malaysia for my full reviews. This Jazz VTEC dyno-check is the first one.

The dyno facility that AMOIL uses is a Dynojet chassis dynos. This is rather fortunate as most of the dynos previously published by me in the past were done on Dynojets so this allows an important continuity, especially in comparing between different engines. AMOIL MOTORSPORTS owner and tuner is a Jackie Ng, whom as might be expected from his generousity in sponsoring TOVA dyno-checks, is an easy going and honest person. Needless to say that should any TOVA reader in Malaysia or even neighbouring Singapore or Thailand decide to make a trip to Malaysia for parts shopping or tuning, I would recommend you look up Jackie as one of the 'must-do' itinerary in your trip. AMOIL's contact number of 60-3-5633-8529. Ask for Jackie Ng and mention that you are referred to him by TOVA.

Dyno Check - Stock Honda Jazz VTEC

We start off with the dyno output for a completely stock Jazz VTEC CVT-7. For reference, the power/torque chart as published by Honda for the L15A VTEC engine is shown on the right. The unit being dyno'ed is not in its optimum condition though as it was due for a major service involving engine oil and filter and air-filter change. Nevertheless, based on experience, these items should not detract too much from the actual results, perhaps at most a couple of ps less in measured power output so the result here can be taken to be more or less representative of the power output of a stock Honda Fit/Jazz VTEC.

A stock Fit/Jazz VTEC as we can see from the chart delivers around 80ps at the wheels when measured on a Dynojet. Although this result is somewhat lower than what I was expecting based on experience with the 1st generation Multimatic gearbox on the EK3 Civics (the CVT-7 is the current generation Multimatic gearbox and actually carries this name in JDM guise), nevertheless 80ps at the wheels in absolute terms is still quite high for a car in this market segment. A power of 80ps at the wheels for a stock Fit/Jazz VTEC has since been confirmed when Amoil had a chance to dyno other units. So the baseline for a Fit/Jazz VTEC can be confidently set at 80ps at the wheels. Based on comparisons the D-series which the L-series replaced, this is about par with the ASEAN 1.6l SOHC and SOHC-VTEC Civics which delivered 84ps and 90ps from rated engine powers of 120ps and 127ps respectively (check out out 'Beyond Stock' archives for a comprehensive listing of those engines).

Coming back to the dyno-chart, note that while the profile of the power & torque curves follows the one published by Honda closely, good torque also seems to be available at a lower rpm than the specifications say. In this case, the torque around the 2,000rpm to 3,000rpm seems to be as high as the spec max torque at around 5,000rpm. The other thing is that with the CVT-7 gearbox, the ECU upshifts at the max-power point (the dyno run was conducted at manual 7-speed mode in '2nd gear'), which is 5,800rpm. So on the dyno, we do not see the power curve dipping because the ECU does an upshift before the engine revs into into that part of the rpm band.

Note how even the torque curve for the L15A VTEC is on a dyno, unlike the published spec curve which shows a clear bump after 3,500rpm. On the dyno, from 2,500rpm to 5,000rpm, the torque is almost flat at 11kgm and only dips after 5,000rpm. Even then, it loses less than 1kgm over that last 1,000rpm. This correlates well with how consistently the Fit/Jazz VTEC pulls across its rpm band unlike what the paper specs suggests. Finally, the L15A VTEC runs with a very consistent air-fuel ratio. Almost completely flat at 12:1 across the whole rpm band. Actually this is slightly rich for Honda NA engines as based on past experience, they seem to deliver most power at around 13:1.

I think the dyno result shows that the L15A VTEC is at least a potent as the D-series which it replaces but with a much higher fuel economy potential to boot. More importantly, the flexibility of the CVT-7 with its 7 speed mode means that the Fit/Jazz VTEC CVT-7 is a capable of quite a fair bit higher performance to boot even in stock form.

Modifying the L15A VTEC NA means

Chris is a TOVA reader from Singapore who owns a JDM Fit VTEC, imported into Singapore by their many parallel importers. Chris first approached me for recommendations for a good workshop here in Malaysia when he had exhausted his means of locating a workshop he can trust down south. That was when I introduced him to AMOIL MOTORSPORTS. In contrast to the stock Jazz VTEC above, Chris' Fit VTEC has been extensively modified. Subsequently Chris had his engine rebuilt and then re-tuned by AMOIL, including dynoing on their Dynojet and this of course gives us the unique opportunity of seeing how high a potential the little L15A VTEC has in response to street legal NA mods.

Rather unfortunately I have lost contact with Chris lately so I am unsure of the complete list of mods on his engines but based on memory, he had the engine rebuilt because of the cold-air intake system he was using caused hydrolock during a day of particulary heavy rain and flooded roads. In the rebuilt process, he had the crankshaft balanced and the cylinder head received a mild port and polish. Other than that, all internal parts remained the same.

Complementing this was the standard array of drop-in mods, a Spoon header and enlarged throttle body together with a set of aftermarket cat-back exhaust from HKS. The air-filter however is a straight drop-in replacement from Mugen as Singapore road authorities has very high intolerance of engine modifications so Chris decided not to run the risk of using another open element air-filter.

The rebuilt process, especially the port and polish and combined with the drop in mods clearly served to increase air-flow into the engine significantly. The dyno-chart for Chris' car is on the left. Note that no air-fuel ratio correction can be done. Originally Chris has a used SFC-VTEC AF controller installed in his car but it was subsequently judged to be faulty and so was removed. Note that as a result of all the air-flow mods, Chris' engine runs extremely lean, at an A/F ratio of 15:1 ! I think this shows well the high air-flow potential the L15A VTEC has potential for. Remember that Chris did not really rebuilt his engine, only having a mild P&P done to the head and all the rest of the mods are really drop-ins.

Of most significance is the characteristic of the power curve vs the stock as shown by the graphs on the right. While the power curve tracks the original stock one quite closely, it does not fall off at all at high-rpms. Rather the power continues to rise right until the shift-point (we can't hit the engine's rev-limiter with a CVT-7 gearbox as the ECU shifts up at around 5,800rpm irregardless of how much we are pushing the throttle). I think this result clearly shows that despite, or perhaps because of, its fuel-economy roots, the little L15A VTEC engine is a very efficient engine in terms of air-flow. This efficiency clearly extends right up to the high-rpms, the stock engine being quite constrained here by the stock ancilliaries like headers, throttle body and the exhaust. This is why by simply replacing those items, and with the help of a mild P&P, Chris could coax his L15A VTEC to deliver power right till almost its redline.

The other thing to note is the torque curve. The torque curve now gets a nice boost after 3,500rpm, gaining more than 1kgm by 5,000rpm, again dipping after that. While the stock engine drops to 10kgm by 6,000rpm, Chris' L15A VTEC manages stay near 12kgm. If only the engine can continue to rev higher, so much more power is clearly available.

In terms of outright power, Chris's Fit VTEC is delivering almost 96ps at the wheels. If we use 80ps at the wheels as the baseline for a stock engine, this means that Chris is getting approximately 132ps from his engine, up 22ps or a healthy 20% increase ! This result, in my opinion is simply amazing, especially given that the L15A series is biased towards fuel economy and good mid-rpm power. Given the fact that the engine is running extremely lean, clearly more power is available by installing something like a Greddy eManage and then conducting the suitable dyno-tuning session. This is something I hope Chris will be doing in the near future.

The effect of VTEC on the L15A VTEC

Chris' car also provided a rather unusual but extremely useful and interesting case study. Recall that when he first approached me, we did not know that his AF controller was wired wrongly, causing the VTEC to be permanently disabled. Subsequently when we dyno'ed the car in that condition, we got what we felt were very low power readings on the dyno. Unfortunately as we did not have a baseline for comparison, we do not know if that was because of a problem engine or whether it was really what the little L15A VTEC was capable of delivering.

The turning point came when I recalled the case of Richard, a TOVA reader also from Singapore who came to me many years ago with his modified EK4. At that time, he had the car dyno'ed at the Dynojet Far East facility in K.L. and again he was having the same wiring problem with his car. So he was dyno'ing around 130ps at the wheels, from an EK4 with a 170ps B16A heavily modified. But because there were plenty of baselines of stock B16As around and we know that they deliver at least 130+ to 140+ ps at the wheels on a Dynojet, we knew something was wrong with Richard's car. Subsequently we had the wiring checked and managed to fix the problem and Richard's car went on to dyno at 180ps at the wheels, the highest level of power from a B16A NA at that time that I have seen.

The other breakthrough came when we managed to get a baseline dyno result from a stock Jazz VTEC. After looking at the power output from both cars, we unanimously agreed that Chris' AF controller to be a highly likely problem. Subsequently we decided to dismantle the unit as it was purchased used and we do not know if it was fully functional or not. The nett result was the huge 30ps jump in dyno'ed power which we see above.

The other nett result was also the fact that we now have the rather unique opportunity to compare the power delivery of the L15A VTEC in complete low-cams (VTEC disabled) and low+high cams (VTEC enabled). The chart is shown on the left. Note how the low-cams output tapers off at a very low rpm, 3500rpm (which is exactly the same rpm as I had deduced in my original full Jazz VTEC review, based on listening to the engine note change). This means that the so-called 'high-cams' mode (where both intake valves are working) actually operates over a larger rpm range than the low-cams mode, if we subtract the idle rpm from the range. I.e. low-cams works from around 1,000rpm to 3,500rpm which is 2,500rpm whereas high-cams works from 3,500 rpm to almost 6,500rpm which is almost 3,000rpm. Of more importance is to note how much more power the high-cam mode delivers. This should prove once and for all that all the talks about how 'economy VTEC' or 'SOHC-VTEC' are 'wimpy' for power output are rather misguided. It really is possible to deliver lots of power using the SOHC-VTEC mechanism. As they say, the trick is in the implementation.

Conclusion

I hope this article provides a very worthwhile read to TOVA readers and especially owners of the Fit/Jazz. While the Fit/Jazz VTEC does not deliver as highly on the dynojet as I initially expected, nevertheless it do deliver a fairly good level of power. But more importantly is how relatively well the little L15A VTEC responds to air-flow mods. While getting 100ps/litre might ultimately very tough, I think modding the L15A VTEC via NA means should ultimitely deliver near that amount, perhaps as high as 140ps. Perhaps a TOVA reader might come to me with that acheivement in the future.