"Making Turbocharger Technology Work"

BMW M3 Turbo Systems

BMW E36 M3 Intercooled Turbocharger System

After the fourth iteration of forced induction BMW’s, with almost every conceivable blower type, we simply cannot justify, either technically or functionally, any other mechanism than the turbo.  We have unhesitatingly set our sights on building the best “spare no expense” system that twenty-five years of experience permits.  It is quite evident that the “best” had to have the turbo.

At the outset, we had no specific agenda regarding blower types, eventhough we have been producing turbocharger systems for various BMWs over the last 25 years. The perception after one trip around the block in an M3 with a centrifugal supercharger (CS), clearly showed that it was not an acceptable machine.  This system was built by the current “top dog,” and is representative of the best offered today. After months of evaluation of the fixed displacement blower, we concluded this approach offered the best performance available under 2000 rpm, but real power was going to be very illusive.  2000 rpm is not the performance range that fast motoring is all about. When the complexity and cost required of the fixed displacement blower installation was summed up, the low rpm advantage was not considered worth the trouble and expense. Then came the turbo.  The whole spectrum of performance of the turbo just came alive and easily proved vastly superior to our experience with the CS.  Except for boost below the 2000 mark, the turbo performance so badly eclipsed the fixed displacement blower that our path to the intended performance was clearly spelled out. 

We had many objectives in mind when designing this system.  Simplicity and serviceability were of urgent priority, but the two greatest objectives were; first, to weed out all the “fussy” little problems that have thus far kept forced induction systems for the BMW from being either acceptable or successful.  Second, to build a system technically and functionally correct. The simplicity, elegance and component quality of M3 turbo solve all these problems and create many  happy owners. The performance of the turbo will create even more incredulous owners.  The long term durability and fuss free operation of the turbo will produce a whole new cadre of firm believers.

Major Component Description
We manufacture all of the components in our systems completely in-house, with the exception of the electronics and the turbocharger. Hope the following data answers a few questions.

Exhaust manifold:

We designed and patterned this manifold completely from scratch. Styled after the Offenhauser Indy car manifolds, this ductile iron casting is extremely strong, yet not overweight.  The decision to use a casting and ductile iron as the material is prompted by the desire to have a high-quality and high-durability piece. The design is slightly conical from the port to the turbine entry and thermal expansion is carefully controlled such that thermal warping is eliminated and straight line expansion assured. This manifold will flow well up to rates equivalent to 600+ bhp.  The T4 turbine flange is machined precisely to eliminate the usual gasket. The manifold comes to you with a proper thermal coating.  No paint. Stainless steel fasteners are provided to hold things together.

Wastegate:

The Tial unit is a CNC billet aluminum top and stainless base. It's a race quality item with the highest temperature diaphragms available. We have integrated the gate into the system in a very interesting manner. We utilized a layout similar to the Toyota IMSA GTP racers of a few years back (arguably the most successful turbo endurance racing effort since the 917). This gate configured to be compatible with modern remote controllers. A Cartech boost gauge and Greddy Profec-B electronic boost controller are also included in the system.

Turbocharger:

The Garrett Airesearch TO4 series turbo is the real workhorse of the industry.  The Turbonetics 60-1 is the starting point and provides nearly infinite room for growth as engine modifications dictate. It has been kept modern with the latest in high efficiency compressor wheels and shaft seals. A ball bearing version is the leading choice for our system. We also like it for the extreme durability it offers. A water cooled bearing section is available and adds even more life. A choice of three turbines, six compressors, and five different A/R ratios gives us the opportunity to size the turbo right on for the end user’s needs.

Turbine Outlet Pipe (downpipe):

The stianless TO pipe is 3.0 inch in diameter and ideal for power outputs to 600+ bhp.  We’ve put the wastegate dump back into the exhaust far down the pipe to avoid the power robbing turbulence right behind the turbine.

Compressor Inlet & Intercooler Tubes:

All tubes are fabricated from high quality mandrel bends, bead rolled on the ends and powder coated with black wrinkle finish. Alternate finishes are available at no additional cost. Silicone material hoses are used throughout, and, on the pressure side, retained by stainless cross-bolt style clamps.

Air Filter Assembly:

Generally one does not consider an air filter as a major component. This time, it's different. Three severe problems exist with the installation of the air filtration system for the M3. Inadequate space for a proper size air filter (160 square inches, minimum) and we've nothing but the atmosphere to push the air into the turbo, hence flow losses are potentially high. The space problem is solved by using the space the factory chose for the original air filter.

Intercooler:

The intercooler is an aluminum fabrication sized for approximately 500 bhp. We use bar-plate cores which yield the greatest efficiency at the lowest pressure drop. These are the very same cores that Spearco chooses to sell. We also decided to utilize a vertical charge flow configuration to increase the internal flow area and reduce the internal friction of a typical horizontal flow configuration. The air temperature going into the engine, as stated so often, is the key element in deciding life or death for a forced induction engine. The hotter the air, the sooner knock sets in, and knock is hugely destructive.  Further to the safety benefit is a virtually free 12 to14% gain in torque due to the cooler, more dense air. The sanity of not having a proper intercooler in any supercharger or turbo system can only be explained by the maker’s accountant and sales staff. It is fundamental engineering that an intercooled SC system is both safer for the engine and more powerful than a system that has no
intercooler.

Anti-Surge / Bypass valve:

The by-pass valve is an air diverter when cruising so the blower or turbo will not need to make boost that would only pile up on the throttle plate and load up the blower. A nice touch that all OEM system have. We have adapted a
brand new style valve that cannot be opened by boost pressure on the turbo side, thus further improving turbo response. Thus far, few makers of centrifugal blower kits see fit to include this essential feature.

Engine Management:

Our system utilizes the factory DME for both OBD I and OBD II systems. We have spent countless months of chassis dyno time to get you a completely reliable and very powerful engine map (a Clayton variable load dyno for those interested). A standard voltage clamp is provided to maintain the drivability and excellent street manners. Also a complete set of injectors is included to compliment the power level and turbo selection.

Pricing

The Enthusiast’s Objectives
Your, and our, objectives for performance and reliability are virtually the same. Only the subtle difference exists that we provide and you use.  With you as the user,  take a minute and spell out the objectives you personally have for the M3 as equipped with forced induction. This paper will try to make the case that the turbocharger will meet those objectives very well. I at least hope to pique your interest to investigate these things further than just listening to the pitch of a supercharger salesman.  Or us, for that matter.

We would like to suggest that most are looking for the best combination of the following facets of performance:

Our contention is that the turbo wins every category, hands down.

Why the Turbo?
For technical excellence and engineering judgment, we should all stick with the industrial leaders such as Rolls Royce, Porsche, Mercedes, Audi, Lotus, Mitsubishi, Toyota, Nissan, Saab, Volvo, and Ferrari. These guys are turbo adherents and lead the world in automotive engineering. Over the last 45 years, turbochargers have been essential in winning thousands of races with the diversity of Formula One, Indy Cars, and even the great endurance contests of Le Mans, Daytona and Sebring. Is the disparity between the abilities of the turbo and the SC that large? Yes it is, and here’s why.

Shape of the torque curve:
The centrifugal supercharger is fabled to offer huge low end torque advantages over the turbo. That is flat wrong, never had an inkling of truth.  With a size compressor selected for, say 8 psi, the CS must turn at some specific speed at the engine redline to flow the air needed to produce that boost. It is necessary to understand that flow through these types of compressors varies with the cube of the shaft speed.  In other words, doubling the speed of the shaft will produce 23, or 8 times the flow.  Turn that around and clearly, the flow is 1/8 at half the engine speed that it would be at the redline.  Basically, that means you have 1/8 the boost at half the redline.  And that is about where it really falls, 1 psi boost at about 3300 rpm.

Please understand, that is what you get with the centrifugal blower, but we strongly suspect it is not what you either want or think you are getting with a supercharger. Wouldn’t it be a hoot if someone invented a way to let the same compressor wheel speed up relative to the engine so more low engine speed boost could be produced?  Such a device exists and it is the turbo.  The key to this great turbo performance benefit is that it can change speeds independently of the engine.

The net result is this: The turbocharger applied to the BMW M3 can produce all of it's boost by 3500 RPM.

Power
There is a very simple equation for calculating the approximate power output of a normally aspirated engine after a forced induction mechanism is applied.  There is no need to solve anything here, but it is quite revealing to understand what the equation says.  Five factors are involved:

 Power  =  Po  x  PR  x  DC  x  Evol Ratio  x  PL

Where:
 Po is the original rated horsepower: say 240 bhp

                                                    Boost + 14.7
  PR is the pressure ratio, or   ---------------------, at 7 psi this is 1.49
                                                          14.7

DC is the density correction due to heating of the air charge.  This is directly proportional to the absolute temperature of the ambient air to the boost air entering the engine.  At 7 psi these corrections are about .85 without an intercooler, and about .96 with the IC. Our systems operate at 8.5-9.0 psi, however we chose the lower boost number for comparison purposes.

Evol is the volumetric efficiency ratio of the blower to the engine.  Since the CS and the turbo have the same Vol Eff, and the engine is the same, this factor can drop out. Assuming comparable compressors are available.

PL is the power loss correction due to the necessary power taken from the crankshaft to drive the blower.  Here the CS takes about 5% of the engine power, whereas the turbo only robs about 1.5%.  The reason for the difference is that the turbo is largely powered by the heat energy in the exhaust gas.  Keep in mind that the heat energy lost out the tailpipe is about the same number of horses as the engine makes. Remember, of the fuel burned, 1/3 goes to power, 1/3 to heat in the cooling system, and 1/3 out the exhaust. Therefore the lost exhaust energy and the engine power are about the same.  When was the last time you saw a 240 hp fan? That is what is made available to the turbo for a driving force without taping off the crank. We don’t need it all, but that’s what’s theoretically available. Enormous, eh?

 So, plug the numbers in and see what they yield:

 New Power:
                          Non-intercooled Centrifugal:

                                   P = 240 x 1.49 x .85 x (1-.05) = 289 bhp

                          Intercooled Turbo:

                                   P = 240 x 1.49 x .96 x (1 - .015) = 338 bhp

If you can do a back to back test on two real cars, those are very close to the numbers you will get.  One wants to ask all the obvious questions of all the CS claims of 340 bhp at 5 psi without an intercooler. 

Lets Talk Value for a Second
Value is the cost of a horsepower.  Assuming everyone makes a nice component, of course.

                                        Typical $6,500*
 Value: Non IC CS =  ----------------------   =   $133  per horsepower
                                       289 hp  - 240 hp

                                            Typical $8,500
 Value: IC and Turbo =  ----------------------- = $87 per horsepower
                                         338 hp  - 240 hp

* Some of the CS systems cost over $9,000, but the equation remains the same.

Notice the difference in power gained between the two systems.  The CS gains 49 hp and the intercooled turbo gains 98 hp.  That means the turbo gains 2 times the power the CS gains.

But I can’t stand the lag!: 
Just answer one basic question.  If you are cruising along at 3000 revs and decide to nail the throttle, would you prefer the zero boost the CS will offer, or the 7 psi that the turbo will reach in less than one second?  If you are cruising at 5000 rpm’s where the CS can actually make some boost, but not yet its maximum, its response is no faster than the turbo.  Rest assured, at a cruise of 5000 revs, you can’t get your foot to the floor and off again without the turbo reaching full boost.  At 5000 revs, the CS will respond quickly too, but it won’t reach full boost. That number is reserved for the absolute redline.

Durability of the Turbo versus the Centrifugal Blower
With the ceramic ball bearing sections and a 5000 mile synthetic oil change interval, the turbo will live well past 100,000 miles (water cooled bearing sections also available). As an example, those 18 wheeler Diesels use approximately a 200,000 mile figure for overhauling their turbos. I doubt there is an 18 wheeler out there that is not turbocharged, and those things cruise under boost.  As it is today for average lives, the turbo will last approximately four times as long as a centrifugal blower.  This is not a small difference, rather, an absurdly large difference.  We provide the ceramic ball bearing section, the oil quality and frequency of change is up to the owner of the M3.

The Turbo Heat Problem
Invariably a supercharger salesman will point to the turbo and flatly state that when it is glowing red hot, it will melt everything under the hood. The problem is knowledge, not the turbo.  Iron and steel begin to glow red at around 1100⁰ F.  The stock exhaust gas temperature is in excess of that, thus the stock exhaust manifold glows when the car is driven hard. No damage is done in the stock condition and none will be done by the turbo.

Engine Safety
It is necessary to feel reasonably comfortable that one is not going to kill the jewel of an engine the M3 is blessed with by adding the forced induction system. To reach this understanding, it is urgent to come to grips with two fundamentals.

When an SC salesman tells you his system is so well engineered that an intercooler is not worthwhile, its time to question his motives.  While his argument may sound plausible by citing that the blower doesn’t make heat, or that intercoolers have bad side effects, this is simply not what physics bears out.

The engine safety of our system is well under control.  The turbo and the CS generally share the same style compressor and are therefore, equal in efficiency, which means they produce the same heat in the air charge. The similarity stops right there.  Our intercooler removes 88% of the 120 F added by the turbo, at around 7 psi.  This intercooler is such a powerful influence on the temperatures, that the turbo could produce over 30 psi of boost before the air temperature exiting the intercooler would be the same as that exiting the centrifugal blower.  Further engine safety is provided by the correct air/fuel ratios and the original factory knock sensing system, via our reprogramming of the DME. Follow the rules regarding fuel octane, standard premium grade, and the safety issue is a slam dunk.

Throttle Response
It is common for someone unacquainted with a turbocharged car to complain about the throttle response with the turbo.  The SC salesman will try to convince you that nothing happens when you move the throttle, not even standard, normally aspirated response. Unfortunately, this misinformation persists, as the engine responds instantly to the slightest throttle position change. When the driver of the Turbo M3 applies throttle, there is actually a small amount of boost in the upstream tubes at that instant. With a small amount of boost available to push it's way into the manifold, rather than just atmospheric pressure, the driver will notice a small, but perceptible improvement in throttle response.

The Daily Driver
The substantial increase in engine power does not come about at the expense of the sweet driving nature of the BMW. All aspects of smooth, easy drivability are controlled by such factors as fuel injection calibration, compression ratio, camshaft profiles, and ignition timing. These items are carefully altered in the installation, therefore the drivability is also unchanged from stock.  If one puts a rock under the throttle to eliminate boost, the driver would pronounce the vehicle as just another M3 with perfect drivability.

Mid-range pulling ability of large engines has always been their attraction. This characteristic now shows up in the Turbo BMW with its new found torque capability. We hope the idea of calling the M3 a low and mid-range torquer doesn't sound too preposterous. Before laughing and rejecting the idea, please accept and regard as fact, the Turbo BMW will pull harder in 5th gear at just 3000 rpm than the stock BMW can manage in 3rd gear, at virtually any RPM. Further along the same idea, 3rd gear under boost will accelerate over 10% faster than 2nd gear stock can manage.  It sounds preposterous perhaps, but it is absolute fact, the Turbo BMW M3 will do exactly that with the equipment provided in our system.  And it does so safely.

Along with the sheer fun and entertainment value of the huge power and torque increase, comes the capability to properly decorate your favorite strip of pavement with long black lines. This is particularly fun as the Turbo BMW M3 never looses its composure and accomplishes such feats with true grace and ease.

Emissions Equipment
All emissions equipment items are in place and completely functional. The Turbo M3 will easily pass any tailpipe sniff test in America.

Installation
Capability and complexity do not necessarily go hand-in-hand. The Cartech BMW system is remarkably simple and straightforward. This entire system can easily be installed by the hobbyist do-it-yourselfer. One should consider the skill levels required as the same for changing a header and tailpipe. Without the distraction of football games, lawn mowing and such, the entire job can be accomplished in 18 hours.

Service and Maintenance
A 5000 mile maximum oil change interval is necessary, then service the rest of the car within BMW’s guidelines.  With the Cartech Turbo system, once installed, adjusted and detailed nicely, the owner/driver can close the bonnet and forget it.

Warranty
All items of our system carry a one year warranty. Our warranty does not extend to any stock BMW components. BMW will not warranty engine or driveline items.

Service After the Sale
In our view, the purchase and installation of our system becomes a mutual project between Cartech, the installer, and the end user. We are committed to making this a good experience for all concerned. We know our product and we are here to help if needed.

Terms and Delivery
Delivery time is 30 days. 50% payment is required. Returned goods are subject to a 20% restocking fee. Cancellation fee is 10%. We accept Visa, Mastercard, Discover, American Express and cash.

Telephone: 210.333.1642

FAX: 210.333.1749

Postal address: 18975 Marbach Ln, Suite#812, San Antonio, TX 78266

Sales E-mail: Mike Montgomery

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Last modified: 04/01/05