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The Production Version of the Supercharger System:
Did we create a vintage Volvo supercar?
This series of articles started with the idea of turning an 1800 into a real performance sports car, the type of car many of us wished Volvo had made to begin with. In the beginning, it was my personal quest for a street car that would perform like my 1800 vintage racecar. I named it the "Boxster Beater" project after I spent over an hour in a rental car following a Porsche Boxster on the coast highway through California's Big Sur. After settling on the supercharger as the best way to achieve the goal, it quickly broadened into an effort to make the same technology available to the owners of other vintage Volvos.
The original supercharged 1800S began testing two years ago. For more than a year we have been working to turn the original supercharger prototype into a kit that would give other vintage Volvo owners the option of significant "bolt on" power increases at a reasonable cost. At the same time we have been able to incorporate several improvements into the system.
As part of the process, four main goals were identified.
The main change from the first prototype has been the inclusion of a state-of-the-art water to air intercooler as an integral part of the system. By including an intercooler we are able to keep the charge air temp down and the density up, allowing our kit to produce more power per pound of boost than other systems.
Delays in turning the prototype into a production system were very frustrating. The configuration of the system changed several times as we searched for an economical way to get it into production. At some point, at least four different companies had agreed to produce or supply significant parts of the system, and all of these arrangements eventually fell through. Finally we settled on a combination of local component production and direct supply by the Swedish manufacturer. Details of the design of the system had to be changed as updated versions of the basic supercharger and intercooler components superceded earlier versions. These problems have been solved, and the system is now in production.
The first of the production versions was installed and tested on our 1800ES test car this winter. The supercharged ES is a ball to drive. Its performance can honestly be characterized as thrilling. (This car is a story in itself. It was purchased sight unseen in response to an e-mail that offered to sell it for $750 to the first person who could pay cash and pick it up from a Perkins restaurant parking lot in Easton, PA. It somehow only made it that far on a trip from Massachusetts to North Carolina. A bank check had to be sent to a person who called herself Amariel in North Carolina in exchange for the keys and title.) In any case it met the requirements of a test car. It was cheap, available, didn't require a lot of work before we could use it (at least in theory), was expendable in that we could drive it through our salt laden winters, and was mechanically typical of a well-used street car that appeared to be mechanically sound. (In addition, it makes a great "sleeper.")
The ES is being used as a test bed for various configurations of the system. We recognize that slightly different versions of the kit will have to be available for the variety of compression ratio, displacement, and cam combinations that exist in the B18/B20 range, including aftermarket modifications, and that it will be necessary to test the system with some of these different engine specifications. The installation in the ES was accomplished with most of its injection components still in place, as they would be needed for testing a fuel injected version of the system. In the process it clearly demonstrated the ease of installing the carbed version of the supercharger system on a fuel injected car. No modifications to the wiring or fuel system were necessary other than removing the stock fuel pressure regulator, substituting one with a wider range, and adding a fuel hose to the Weber carb. Thus, it will be a simple process to switch back to FI.
For testing purposes, the car is equipped with instruments to monitor air and water temperatures both before and after flow through the intercooler, a competition-type tach for accuracy, an oxygen sensor and air/fuel ratio meter, two dual exhaust gas temperature gauges, a knock sensing ignition retard system with monitor, and a marine-type fuel flow meter. Testing issues involve tuning to provide the proper combination of safe boost levels for each engine version, while getting good low end power and response together with decent fuel mileage at both high and low boost levels.
Contrary to what most would guess, the system operates under boost less than 1% of the time during normal driving. Even at a 70 MPH cruising speed, the system is running at an approximate vacuum of 10", and only uses minor levels of boost for most hills and acceleration in traffic. When power is not called upon, the car with stock engine and exhaust drives like any other ES (actually more smoothly than most), but changes character completely when significant throttle is used. The only negatives so far are that it uses more fuel than stock, in certain ice and snow conditions it is more difficult to drive than the unmodified car, as it is too easy to spin the tires, and even with a manual choke, in temps below 40 degrees needs a minute or so of running to warm up before it will pull away smoothly.
The current intercooler is a modular unit using Laminova cooling tubes, a patented Swedish design that is also used in automotive oil coolers. With this design, used in several high-end kits and OEM installations on Mercedes, BMW, etc., we were able to incorporate the intercooler cores into the intake manifold plenum. (Essentially the same intercooler is sold at www.subysports.com as an aftermarket turbo intercooler upgrade for the Subaru WRX for $1495.) With the modular construction of the unit, we can make modifications to accommodate different applications without changing the basic unit. The intercooler is attached by automotive-type coolant hoses to an intercooler radiator located in front of the car's radiator. Our intercooler radiator is the same one made for the Kleemann Mercedes supercharger systems. Water is circulated through the radiator and intercooler cores by an electric water pump located near the radiator, behind the front grill.
On our test car we have the pump connected to a switch so that we can turn it off and simulate operation without an intercooler, as the temperature quickly rises without the benefit of water circulation to non-intercooled charge air temps. By turning the pump on and off and on we can control the temperature and can test at various temps. This has turned out to be a very useful tool in our testing, especially in regards to boost vs. detonation tendencies. It also lets us demonstrate how effective the system is in cooling the charge air and producing additional power.
As part of the development process, we are continuing a series of chassis dyno tests, using a state-of-the-art, computer-controlled, Superflow chassis dyno. For the first tests we purposely kept the ES in stock condition in order to replicate the conditions of the average customer installation. The exhaust was the stock three muffler system. To improve the handling ball joints, suspension bushings, Bilstein shocks and our progressive suspension spring system were installed. The suspension changes were made in the interests of comfort and safety at the higher speed levels the car was expected to reach, and to take the whole project in the direction of the 1800 "supercar" goal. Further chassis testing has included a switch to Carrera shocks where we can have a choice of valving.
The car was tested on the dyno before the supercharger was installed. The result was 90 HP at the rear wheels. After supercharger installation, with no other changes, the dyno numbers have been in line with projections that were based on prototype testing. Running a drive ratio calculated to give a comparatively low boost level, we got 127 HP at the rear wheels (approximately 155 flywheel HP) at 6 lbs. boost at 5500 RPM. This represents slightly more than a 40% increase in power over stock and would be the basic boost configuration of the supercharger kit designed to be used with a stock engine and stock exhaust.
With a higher supercharger to engine drive ratio we got 143 HP at the rear wheels, the equivalent of over 170 flywheel HP, at 6000 RPM at 10.6 lbs. boost. At this boost level some type of ignition retard system would be required in order to avoid detonation. On our test car we use a sophisticated knock sensing system. Less sophisticated systems simply allow a programed amount of ignition retard per pound of boost.
It has to be noted that we were able to attain this level of power with a stock engine and highly restrictive stock exhaust system. It would be unusual for an owner to go to this much trouble to improve performance, and then keep the stock system. At higher RPM levels it was clear that power was being significantly restricted by the exhaust system. After a certain point, further increases in boost produced comparatively insignificant increases in HP. I was sure that similar power could be achieved at lower boost levels with the engine equipped with a more appropriate exhaust system. This was borne out in subsequent tests -- see below. For this reason we recommend to anyone using the SC system that they install a high capacity exhaust system.
Actually, it took considerable restraint not to jump immediately to higher power tests, but we wanted to first develop a good baseline for what might be expected by the average Volvo owner with an unmodified car.
Once the baseline tests were done, modifications to the test car were completed for higher power tests. These included the installation of a modified head with significant exhaust porting and a reshaped combustion chamber, a large tube tri-wye header, 2.5 inch exhaust system and Dynomax Superturbo muffler. As an added experiment we modified the test system to include a bypass valve that was designed to relieve stress on the supercharger during non-boost operation and at the same time improve fuel mileage by reducing the power needed to turn the supercharger at cruising speeds.
The results of the power tests were better than expected. We reached our target of power equivalent to a good vintage race car on our first set of dyno runs at only 8 lbs. boost. Specifically, the chassis dyno tests showed 173 HP at the rear wheels, and 208HP at the flywheel. As we estimated, the modifications to the engine and exhaust system, including replacing the ES's stock "D" cam with a "C" cam, produced more power at the same boost levels as prior tests with the stock engine and exhaust setup. The pleasant surprise is that we got significantly more power at lower boost levels, the only drawback being that the power moved up the RPM range, giving slightly less power under 3000 RPM than the unmodified system. Acceleration runs at this power level have been hindered by retention of the stock clutch, but we have done several 0-60 runs under 7 seconds. The next set of modifications will include an aluminum flywheel and a special clutch disc.
Although few people have asked about it, we have also been concerned about fuel mileage. Initial testing produced some alarming fuel flow numbers, but after a good deal of carb tuning we have gotten as high as 20 MPG on trips. An average mix of around town, some highway and a few acceleration runs yields 16-17 MPG. A 600 mile trip through New England that included a demo of the system and some spirted driving on winding roads through the mountains averaged 18 MPG. It is clear that the most significant impediment to improving mileage is the high numerical gear ratio, 4.3:1. Even with overdrive, cruising RPM is in the 3,000 RPM plus range. With the supercharger this type of gearing is unnecessary and a change to a 3.90 or 3.73 ratio should yield a significant improvement.
Higher boost versions of the system are based on the same components as the lower HP versions, but the drive system is set up with a higher drive ratio that will produce increased boost at any specific RPM. In this configuration it will produce sufficient boost that an engine with upgraded components should be used. Modifications from stock would typically include forged pistons, ARP head studs and rod bolts, and a low-compression head ported to emphasize exhaust flow. We also strongly recommend the use of a knock sensing ignition system with adjustable boost and knock timing retard programs.
Following further tests of the carbed system, we will be testing a fuel injected version using an aftermarket FI system. We will be doing this testing to evaluate the additional performance possibilities of a programable fuel injected version, even though the current ES installation has shown that use of the carbed system in an injected car is not a problem. The question here is whether any improvements in performance are worth the additional cost, estimated to be in the $800 - $1000 range for components alone.
Overall, testing has confirmed that the system can produce the performance we expected. In addition, results to date indicate that the best setup for use with the SC system would include compression ratios of 9:1 or under, and cams with as little overlap as possible, such as the "C" cam found in most of the carbureted B18s and B20s. (Development and testing of a dedicated "supercharger" cam is underway.) A high flow exhaust system should be considered a must as it not only allows significant increases in power, but allows that power can be produced at lower boost.
Have we achieved what we set out to do when I wrote the first in this series of articles almost two years ago: produce an ultimate vintage 1800 street car? I suppose that is a matter of opinion. To me the performance is not a surprise, as I have my racecar for comparison, but for others the performance level achieved is really unexpected. Those who have tried the car have been surprised and thrilled. Comments have included, "Unbelievable," "Unlike anything I have ever experienced in my ES," "the suspension handled... as well as any luxury car I've ever driven in." I can only add that a vintage Volvo with this much power is a unique driving experience and can be truly exciting. Truly racecar performance on the street without changing the car's charm and vintage character.
As improvement is always possible, reaching any "ultimate" is a fleeting goal, unlikely to ever be achieved. The ES accelerates and handles like a racecar, and the dyno plots show strikingly similar power levels at various RPMs to race car engines we have tested, with the supercharger system having a broader power band and more torque at both low and high RPM levels. It has about as much power as most people would want on the street and the sound of it accelerating under load with the throttle open is something special -- think superbike. It is only too easy to bury the speedometer needle.
Though the current ES is a good test bed for proving components, it is still not the best we can do. Clutch, flywheel, transmission, and maybe even steering can all be improved, and there are plans to do so. The ES is heavier than our original 1800S test car, and this is a handicap when trying to achieve ultimate performance. In addition, cosmetically the ES is an ugly duckling and needs a lot of work. In a way these shortcomings are good, as making the necessary improvements will form the basis for another article.
If you have any questions, feel free to e-mail me directly. If you would like to see the actual plots of our dyno tests, please e-mail me and I will add you to an e-mail group to receive copies of past and future tests. To open/view the tests you will have to go to www.superflow.com/windyn/demodisk.html and download their demo program.