Light-Pressure Turbo 1.6 SOHC Civic Manual

We have looked at Light Pressure Turbo-charged 1.6SOHC Civics in our last two Beyond-Stock articles. Though we covered both VTEC and non-VTEC versions, nevertheless both cars uses an automatic transmission. So, there will doubtless be readers who will think about a similar modification on a manual transmissioned 1.6SOHC Civic. We have seen that the HKS LPT kit can upgrade the power output of a automatic non-VTEC 1.6SOHC to equal that from an automatic B16A. The results would be similar on a manual 1.6SOHC as well. But since a manual transmission has power losses of only half of that of an automatic (~15% vs ~30%), a manual 1.6SOHC Civic, if suitably turbo-charged should be a very potent car. Indeed, via an LPT bolt-on kit, owners of 1.6SOHC can look forward to modifying their cars to match the overall performance of a Civic SiR !

By sheer coincidence, the third HKS LPT 1.6SOHC Civic that I had experience with was a manual model. The local Malaysian Honda agent at that time (Honda has since came into Malaysia with an official presence) did locally assemble and market a manual model for the EK generation, fitted with a 1.6SOHC non-VTEC engine giving 120ps and a 6800rpm red-line. The engine is in fact the same as that on the automatic LPT demo-Civic. I often wonder about the rationale of this marketing decision though - that of not using the more powerful VTEC engine in order to exploit the more performance oriented manual transmission.

Nevertheless, a number of this Civic models were sold, to owners who no doubt prefer the performance advantage of a manual transmission and was willing to tolerate the inconvenience incurred during traffic jams and slow, stop-go middle of town driving. One of them have decided to upgrade the engine using the custom-designed HKS Light-pressure turbo bolt-on kit, not long after the demo-Civic was finished so I was fortunate to be able to test it along with the demo-Civic.

HKS Light-Pressure Turbo with a Manual Transmission

The 1.6SOHC VTEC Civic had the prototype kit, the 1.6SOHC Civic was a demo car. Both of course are automatics. This 1.6SOHC manual Civic however is fully a customer's car and it uses the actual finalized production kit. Supply of the properly designed and casted manifold have of course been secured by this time so the problems with a leaking manifold are non-existent in this car. Coupled with the benefits of experience with the demo-Civic, installation of the HKS LPT kit on this manual Civic was a very straight-forward task.

Because shift-shocks do not exist with an automatic transmission (we let off of the throttle during gear-shifts), boost spikes are not a problem in this Civic. As a result, the working boost, which was set to 0.3bar, the same as the demo Civic, was easily kept stable. Similary, the original catalytic converter was retained, with the "down-pipe" from the turbo-charger to the cat being custom fabricated. As has been explained, a blow-off valve is part of the kit and that was installed and routed in a similar way to that on the demo-Civic.

As described in the demo-Civic article, the kit does not include an oil-cooler but this accessory is deemed important if one desires durability and reliability from the engine. The owner thus opted to install an oil-cooler, choosing the same model as that installed on the demo-Civic. In this car, the oil-cooler was installed "on its side", with the oil lines going in and out on the right hand side (as shown on the photograph).

Fuel management is again via the proven HKS FCON-4 piggy back computer, the device being provided as part of the HKS kit. The base map was taken from that on the demo-car and then fine-tuned to cater for any deviations due to the manual transmission (which were minimal since the engines are the same). The owner of the Civic also opted to install the HKS ignition timing computer in order to ensure the best tuning for the car. Most people will mount the FCON-4 computer somewhere on the dash in order to show it off but the owner decided to put it into the glove-compartment. Again only a boost meter was installed to track operating boost. As a result, the car's cockpit looked very stock indeed.

As I would expect from an Aerotech project, the car also received attention to the other equally important parts. The suspension has been upgraded using Bilstein adjustable shocks along with Eibach Pro-Kit springs. This takes care of the handling aspect of the car but stopping can be an even more important aspect, so while the rear brakes are still drums, the front discs were replaced with PowerSlot slotted ventilated brake discs of the same size. Brake-Pads are stock but the flexible rubber brake hoses were replaced with steel braided teflon hoses to ensure firm confident braking. The brake fluid were changed at the same time to HKS Super DOT-4 Racing. As can be clearly seen, no area is ignored when upgrading the performance of the car. Finally, while the stock rims were retained, the tyres were upgraded to Bridgestone Turanzas.

The Dyno Result

After that brief coverage of the installation of the HKS kit, the most awaited part will definitely be the dyno result. However, let's discuss about the expected result purely from a theoretical point of view first. As we have seen, the same kit used on an automatic Civic gave almost 111ps at the wheels. This works back to almost 159ps at the engine, using the reference 30% power loss at a Honda automatic gearbox. If we are to assume that the two engines (this one and that in the demo-Civic) are identical; Honda's engines are generally built to very close tolerances; then on a manual gearbox with a reference 15% power loss, 158-159ps at the engine will work out to around 135ps at the wheels. I.e. assuming our working reference for power losses due to transmissions that we use here at TOVA is correct, we would expect this Civic to generate around 135ps at the wheels.

Coincidentally, 135ps at the wheels is also around what an early generation B16A engine would deliver with a manual transmission. Early generation B16As are spec'ed at 160ps while the later generation B16As, the so-called "Big VTECs" generates a higher 170ps. As we have seen in our Beyond Stock article looking at reference power figures for B16As, the early generation B16A dynos at 136ps while the later generation dynos at 142ps, both values at the wheels on a Dynojet machine. As we have discussed before in the previous two articles, a natural target for a project to turbo-charge a 1.6SOHC would be a Civic SiR with the B16A engine. Therefore, the basis by which we might judge the power acheivement of the manual EJ7 Civic in this project would be whether it can or cannot equal the power of a B16A Civic and at a minimum that of the early gen 160ps B16A.

As the dyno chart on the left shows, final tuning allowed this manual turbo-charged 1.6SOHC Civic to dyno at slightly over 133ps at the wheels on a dynojet. This is almost exactly what we have calculated above ! Impressively, this is also almost equal to the 136ps at the wheels reference power level that we have previously established for an early gen 160ps B16A with a manual transmission. Therefore, in this aspect, the HKS LPT kit really did acheive the targets expected of it. As with the automatic Civics, this manual Civic again enjoyed a large power advantage in the midrange when compared with the B16A Civics. In this case, the mid-range power advantage is significant, not only versus the earlier 160ps B16A, but also against the later 170ps B16As. Let's take the power levels at a few rpm points for comparison; say 4000, 5000, and 6000rpm.

At 4000rpm, both generations B16A will deliver around 70ps or so while the LPT 1.6SOHC generates 90ps at the wheels, a 20ps advantage. At 5000rpm, the LPT 1.6SOHC delivers around 120ps while the B16As hovers around 90ps or so, an even higher 30ps advantage. That is more than 30 percent higher power at the wheels !! Even when we venture into wild-cams territory for the B16As, 6000rpm, the LPT 1.6SOHC still retains around a 10ps advantage: ~130ps for the LPT 1.6SOHC against around 120ps for the later gen 170ps B16A. But as we all know, the B16As are high-revving kings. So, while the 1.6SOHC have to stop at 6800rpm, LPT or not, the B16As have just gotten into stride here and both generations will happily rev on for another 1000+rpm, right up into the 8000rpm territory !

Of course we are being very inconsistent here; comparing a turbo-charged engine against an NA'ed one, especially when both are the same engine capacity, can be unfair to the NA engine. This is because turbo-charging in a sense can be viewed as somewhat similar to increasing the displacement of the engine; thus the 1.6SOHC when turbo-charged, will operate as if it's a 2.0l or even a 2.2l engine and subsequently can enjoy considerable power advantages against the NA version at the same rpm points. That the B16A can deliver the same max power as the LPT 1.6SOHC gives considerable credit to both engines; to the B16A in that DOHC and VTEC can allow it to equal the acheivements of a turbo-charger, and to the LPT 1.6SOHC too, in that turbo-charging can allow what is basically a much lower tech'ed engine to challenge - and beat in some areas - a very high tech'ed racing tuned engine ! It is very important to emphasize this point; frequently proponents of either turbo-charging or so-called "NA tuning" will criticize the other alternative to the extent of being overly defensive. The truth is of course that both are equally valid approaches to building an engine, and in this case, we have seen that while we can build a 1.6l engine using double camshafts, VTEC, and generous doses of racing technology to deliver 160ps or more, it is also equally possible to acheive the same results (and the same driveability) by turbo-charging a much lower tech'ed implementation of the same sized engine.

Indeed, the considerable midrange power of the LPT 1.6SOHC can be fully appreciated when comparing it against the more powerful, larger capacity B18C engine as installed in the DC2 Integra SiR. Now, the Integra engine has a much higher max power than the LPT 1.6SOHC. This is one of the design aspects of a Light-Pressure-Turbo kit anyway. Street-use means sacrificing outright top-end power in return for very good streetability which includes very good low-end and mid-range power. But, even against the higher max powered B18C, taking the same rpm points as before; at 4000rpm, the LPT 1.6SOHC still retains a 10ps advantage; 90ps vs ~80ps for the B18C. At 5000rpm, surprisingly the power advantage goes even more on the side of the LPT 1.6SOHC; 120ps vs ~105ps for the B18C. This is in spite of the fact that VTEC cuts in at 4800rpm for the B18C. At 6000rpm however, things have equalized with both engines delivering ~130ps at the wheels (note that VVIS would have already opened the secondary intake runners at 5500rpm).

It can be clearly seen that the manual transmission have allowed the power characteristics of the LPT 1.6SOHC to shine. The max power of the 1.6SOHC is of course ultimately limited by its much lower 6800rpm red-line - between 1200 to 1400rpm lower than the two super high tech'ed DOHC VTEC engines. But this rev-limit is basically because of a much lower tech'ed engine. The stubborn proponent of the turbo-charger may even argue that if we are to lower the 1.6SOHC's CR and thereafter go for sky-high boost levels, we can easily cream the DOHC-VTECs in max-power. But I think that would be missing a very important point here. We are after all looking at a Low-Pressure-Turbo kit here. And the design objectives of an LPT kit, designed specifically for street-use as discussed my 'tuning approach' editorial does not emphasize absolute max power but rather important practicality aspects like very good throttle response, seamless power delivery, powerful low-end and mid-range, and most often complete bolt-in installation. With these characteristics, we will enjoy the same user-friendly streetable characteristics -and performance- of the much higher tech'ed DOHC VTEC B16A and B18C engines without having to resort to extensive engine builds or severe driveability compromises.

The Brief Test Drive

I did take the car for a very brief spin immediately after it was completed. The owner was with me and we took the car out to where I was able to floor the throttle several times. I tried going full throttle from various starting rpm points - low revs around 2000rpm, as well as from between 3000-4000rpm. The results were always satisfying. The stock car itself is actually designed to work with a 1.6SOHC engine. Though the owner have beefed the rest of the car up, the car is basically still a light weight compact sized sedan. So the LPT'ed 1.6SOHC imparted a startling pick-up ability to the car. Strangely, there was even a VTEC-like power surge around 4500rpm (it can be clearly seen from the dyno chart too). However, this surge should not be mistaken with a turbo boost surge. The car is LPT'ed and that means almost instant boost and response anytime the throttle is floored. With the benefit of a very healthy power to weight ratio (even better than the heavier bodyweight Civic SiRs), the car, especially in the midrange, literally jerks forward anytime the throttle is floored. Even from as low as 2000+rpm, there is no discernable lag, thanks to the LPT design. In the mid-range, this LPT 1.6SOHC will indeed be faster than a manual Civic SiR, even the DC2 Integra SiR !

Again I have to say I am very impressed by this LPT 1.6SOHC Civic. Readers who have been following this 3-parter turbo-charged SOHC series will hopefully now know what kind of power benefits they can have with a well designed LPT kit, as well as its considerable advantages. However, I would emphasize that doing this 3-parter series does not imply any "pro-turbo" slant in TOVA. But over the years, I have been contacted by many TOVA readers who are driving SOHC Civics, asking if there are "effective power upgrades" to what they describe as their "low-tech SOHC" engines. Therefore I want to highlight that there is indeed life for Honda's SOHC engines - it is not a "no-hope" case where one will forever be envious of the performance that a Civic SiR driver enjoys. So, 1.6SOHC Civic drivers, you can enjoy good power too - very good power as a matter of fact. Indeed, seeing that the 1.6SOHC engine is also used on the Integra ZXi models, owners of those models should be happy with this news too.

It have been pointed out to me that an LPT kit is a very costly project. That is indeed true but unfortunately quality do have to come with a price. I hope that with the conclusion of this 3 part series on the Low-Pressure-Turbo 1.6SOHC engine, owners of 1.6SOHCs (be it on a Civic or an Integra or even one of the rarer Honda models like the Concerto and Domani) will no longer feel like they are the "poor" cousins; very high power can be acheived, allowing performance levels as good as the B16A'ed Civic SiRs, indeed even approaching that of the B18C'ed Integra SiR; the key is simply the Light-Pressure-Turbo !