Out of the car:

The emphasis is on straight low volume runners everywhere.

I often see too much preference toward the wastegate which greatly hurts flow to the turbine.

Here’s are a couple of disasters:

The boost wiggles are not relevant to boost creep, rather they relate to the boost controller closed loop settings. The key is you see a large output turbo in a low boost situation and NO CREEP.

The more recent map shows the controller properly set and boost is rock solid at 18.1 psi as of December 2017.

Many manifolds use two wastegates with the objective of keeping the very distinct rotary power impulses separate and undiluted. This is a good idea but it can also be achieved by using a partitioned single wastegate. Dual wastegates add loads of additional tubing, welding, prone to leak V bands, and heat.

Boost control is significantly influenced by wastegate piston area. I use a large single 60 MM piston wastegate. Dual wastegates are generally 44 mm or 38 mm.

Piston area

(1)     60 mm     4.38 square inches

(2)     44 mm     4.71 sq inches

(2)     38 mm      3.51 sq inches

Two 44s add a modest 7% over a single 60.

Wastegates are a VERY important component of the manifold system. They are a valve that must always function superbly at 1800 degrees F.

A sticking valve can add 20 psi in a fraction of a second. Major engine damage can occur if the valve sticks closed.  The CPR manifold is designed to use a single top shelf Tial V60 mm wastegate.

It is also important to locate the wastegate so the heat sensitive end (silicone diaphragm) is away from the heat. The CPR location is under the car and away from any heat source. I see many wastegates located just above or very close to the very hot manifolding. Silicone does not do well in an oven and a wastegate malfunction can quickly break an engine..  it was thoughtful of Mazda to design the lower A arm/subframe so as to provide an optimal location for my 60 mm wastegate.

Another wastegate consideration is flow from the manifold thru the wastegate and back into the exhaust. The CPR manifold scores highly with zero  bends and a smooth blend back into the downpipe. Open wastegate dump tubes are both annoying and not needed if the flow meets the downpipe at a friendly angle. I see little power penalty with this friendly feature. I was going over 160 between the ¼ and 3/8 markers at the Texas Mile at 25 psi with my 3 inch street exhaust.

A flex section (between wastegate and downpipe) is included to avoid any downpipe cracking.

The 13B-REW exhaust port is 50 mm or 3.04 square inches of area. Any reduction of runner area will reduce flow. Runners need to be at least 50 mm inside diameter.

Avoid manifolds that use smaller runners. While smaller runners increase velocity the more important factor is that the drag caused by the step down area reduction decreases overall flow. You can’t have something (velocity) increased without losing something (flow) else.  A bad idea.

The above example is such a manifold... note after a bunch of bevels and grinding the inside diameter of this manifold is significantly reduced. Many manifolds are made from 1 ½ pipe which has an inner area of 2.035 square inches or 39% less than the CPR manifold which is 3.35 square inches. Reduced runner area creates:

Less Turbo Drive

Higher Exhaust Gas Temperature

Higher Exhaust Backpressure

Higher Combustion Chamber Heat (CCH)

System No No Number Two

Sucking Hot Air

I see many setups where the air intake/filter is located almost on top of or just behind the intercooler!  What could be crazier? You add an intercooler for the sole purpose of removing heat from the intake charge. A good intercooler removes between 100 and 150 degrees F. That massive amount of heat is expelled out of the backside of the intercooler. The air intake for the motor should be nowhere near it.

Power loss (below) at only 8 psi.. probably quite a bit more at 20 psi and beyond plus increased potential for knock at elevated Intake Air Temperatures. (thanks Kenne Bell)

Design and execution wins races and delivers the victory margin.

All of my racing accomplishments were achieved without a turbo in sight. All “NA”. (Normally Aspirated) Nothing but 14.7 psi of Mother Nature’s own pressure. No turbo hammer for power.

The NA world is a very different world. So much brainpower devoted to finding every single CFM. Flowbenches are one of the tools of choice. Most turbo guys don’t even know what a flowbench is. Every bend in the tubing, the length, the area, the temperature, the ambient surrounding pressure, all so important as to encouraging as much flow as possible…  the game is to encourage as many oxygen molecules into the motor as possible so as to burn them to make power.

The CPR turbo manifold is exactly similar… trying to get as much flow to the driven turbine wheel is JOB ONE.

My manifold is just part of my overall rotary system which includes the ports, the post turbo exhaust, intercooler type and location etc. All these items are designed with a NA mindset. Sure we have the hammer (turbo) but I want to further exploit it thru NA engineering.

Let’s get in to the manifold design.

The only dynamic that drives the turbo is the power from the explosion within the engine. I want my turbine wheel to be as close to that explosion as possible. I would love to bolt the turbo to the exhaust port!  Not being able to do that I will settle for being as close as possible.

In 2014  Ford released one of their most important engines:  the clean sheet of paper EcoBoost turbo 2.3 liter four.

Three hundred and ten horsepower, 320 foot pounds of torque from 144 cubic inches!!! Engineered in the 21st century from a totally clean sheet of paper… take a good look at where the turbine housing situates… bolted to the head!

Small air filter due to space limit. Directly behind really hot intercooler exhaust. Blow off valve not only located on intake tube but on outside of turn. 3 strikes and you’re… but there is a fourth. The output of the turbo should have turned 90 degrees and entered straight into the bottom of the intercooler.

Note the exhaust path leads straight to the wastegates and the remainder to the turbo. The carriage is driving the horse.

The absolute last thing you want to do is locate any outlet port on the outside of a turn as the outside wall is the controlling factor for the turn. (I see this often re blow off valve location on the intercooler pipe to the throttle body)

Here’s another example of major flow interruption due to wastegate port location on the outside of the turn:

After heating a Mica panel with a 1300 F propane air torch for 2 minutes I was able to comfortably touch within an inch of the center of the heated surface on the back side.

Try that with any metal.

Combine the 12 X 13 inch Mica sheet with a PTP Lava Turbo Blanket to reduce under hood temperatures and you are set.

A turbo blanket, PTP or otherwise, will greatly help reduce underhood temperatures but is insufficient to eliminate LIM runner heating. Only Mica will solve the problem.

Mica P/N 85165K82 @ McMaster Carr (1/4 inch)

Mica P/N 85165K81 (1/8 inch)

On duty in my engine bay...

High flow with minimized restriction all to designed to lower exhaust manifold backpressure.

Backpressure is as evil to the motor as front weight is to the chassis.

Backpressure reduces turbo drive.....

If you visit the "No Dyno No Problem Section" you will see that in addition to delivering exceptional midrange power the system makes killer top end. For instance it made 552 rwhp at  peak

torque (6487) and 548 rwhp at 8604! Almost no top end drop off.

Backpressure increases exhaust being carried into the next intake stroke!

Imagine: you are trying to get as much oxygen into the motor to burn. To the extent it is cold it is more dense and therefore more powerful. To the extent it is cold it is less likely to detonate.

To the extent you have backpressure a volume of hot, non oxygen bearing gas is mixed into your cool intake charge.

Backpressure stacks back into the exhaust phase raising the temperature and overheating your apex seals… warp.

If you review my manifold details you will see short, large area runners and a perfect straight blend to the T4 flange.


Cadillac just revealed a clean sheet of paper radical twin turbo 4.2 liter monster that makes 550 flywheel hp. Radical because the head is reverse flow. The twin turbos are located in the valley between the heads AND the exhaust blows right into the hotside housings. The compressed air after a liquid intercooler enters where the exhaust ports normally locate,

“the turbochargers located at the tops of the cylinder heads, provides a number of benefits. Most importantly, it essentially drops turbo lag to zero, making for a more responsive engine…”

“the turbocharger housings also act as the exhaust manifolds to assist efficiency. The manifolds are also configured to work with the engine’s exhaust pulses to deliver the proper airflow to each of the scrolls in the turbos.”

Scuttlebutt is that the engine will be made in Bowling Green, home of the Corvette and may be the engine for the mid engine Corvette.

My point is, of course, that each of these modern turbo’d powerplants place the turbine wheel as close to the exhaust port as possible for improved response.

That is the primary concept behind my design .

"While many of the features designed into the new mill seem to be borrowed from the Cadillac line of twin turbo V6s, including turbo placement and what appears to be exhaust manifolds that are directly integrated into the head castings—just like the LGW V6 found in the ATS-V.”

Enginelabs January  5, 2018

Breaking March 21, 2018… another vote for low manifold volume.


CPR is joint venturing with Carter Thompson and will probably be

back in production with an uprated manifold and downpipe.

stay tuned.



Many V mount setups feature the air filter just behind the intercooler which, although not as dramatic as the enclosed picture, is just as bad.

Setup No No Number Three

Restrictive Air Filter

Many of setups I see feature air filters too small to flow enough air without restriction.

There are so many interrelating factors that must be considered while designing a total system and some seem too often end up not receiving the proper attention. Air filters remind me of 

CPR objective:

minimize the wastegate as much as possible while controlling boost.

Some have criticized the angle of my wastegate tube in relation to the runners. They say it isn’t positioned so as to be impacted enough by the exhaust stream towards the turbo. They are half right. The wastegate is positioned so as to not affect the flow to the turbo but it does, by virtue of the piston size, get the job done.

Here’s the proof… a boost plot showing three boost curves, the lower curve, around 16 psi, running off the wastegate spring with the boost controller turned off, a few runs around 20 using the boost controller, and 25. The key as to whether the wastegate works properly is the lack of any boost creep while running low boost with a large 80 pound per minute GT4094r turbo.

Boost is controlled, but flow is unimpeded. Win Win.

It is important that the tube between the intercooler and elbow not be butchered with a blow off valve hole. The blow off valve should be located on the flat end tank surface of the intercooler where it can do its job but not have ANY effect on flow. Carving a hole the same diameter as a pipe greatly disrupts flow.

I favor 3 inch downpipes. The port in the turbo hotside to the exhaust is 3 inches so there is little merit in increasing the size as a chain is as strong as its weakest link. Further there is little pressure in the exhaust as it has expended most of the pressure driving the turbine wheel.

Since the turbo is approximately 6 inches rearward a very nice intake with a large 9 by 7 inch filter is a convenient fit. As previously mentioned, the rotary needs 30% more air than a piston engine to make similar power so a larger filter is a great help. 500 hp requires around 1000 CFM and you don’t want the restriction at that flow level delivered by a smaller filter.

I recommend that you leave the 4 inch clothes dryer aluminum flex tubing with the dryer and connect the filter and turbo with an aluminum 4 inch tube. I have seen dryer tubing collapse and get sucked into the turbo.

Here’s the CPR system in my car:



Almost all manifolds place the turbo forward of the CPR design. Forward manifolds have longer tubes which place the driven wheel (turbine) further from the explosion. They also have an additional set of bends and more volume.  

Just like chassis weight is evil, runner volume is evil as noted by Ford bolting the turbo  hotside to the head and GM copying the position with their twin turbo V6 and new twin turbo V8 for the mid engine Corvette.

“exhaust manifolds that are directly integrated into the head castings—just like the LGW V6 found in the ATS-V.”

Less volume delivers more response.  

The CPR manifold has one bend and then a straight run into the driven wheel. This delivers short runners, places the turbo closer to the explosion and delivers low internal runner volume.

In order to deliver runners that are really short, straight, (almost) equidistant between front and rear rotors the turbine housing, which can reach become cherry red (1800 degrees), is positioned within a half inch of the aluminum lower intake manifold. Aluminum is one of the most heat receptive materials on the planet. Heat the end of a 30 inch aluminum welding rod with a torch and you will quickly not be able to hold the opposite end.

There is no way the engine would run properly with the front two runners receiving the massive heat from the hotside turbo housing even with a turbo blanket..

 Enter magic MICA.

  Material Properties Heat transfer                                               

Aluminum 118
Stainless Steel 16
Titanium 22
Inconel 8.4

Mica .71

I see two crazy numbers… Aluminum 118 and Mica .71

Aluminum is extremely receptive to heat YET charge air must be as cold as possible.

Mica is the answer and allows the CPR flow oriented turbo position to work.

A 1/4 inch Mica heat barrier gets it done.

Does it work? Check this out

While the above was written in 2015 it appears that the same very close turbo to exhaust and low compressor to motor volume is being planned for the 2019 mid engine Corvette.


 NA engineering… encouraging flow, transporting power to the turbine wheel.  


  Wastegate Engineering

The flow bypass component, commonly referred to as a “wastegate,” is a very important to get right. Ideally, from a power point of view, it would be great to have no gate. All of the exhaust would hit the turbo. Of course boost would spike and many bad things would happen.

Flow bypass is about finding a proper balance between flow to the turbine wheel and flow to the bypass/wastegate.

Borg Warner has offered an internal wastegate option recently for a number of high flowing turbos and it has been found to be a challenge to control boost. I much prefer the external wastegate as it delivers, when properly situated, perfect boost control.

Like this:

Often, it appears that the air filter space looks a lot like the “D.”

Since the rotary needs 30% more air to produce the same power as a piston engine it needs an air filter that is 30% larger.

The proper size air filter for a 500/600 hp rotary is 9 inches long and 6 to 7 inches in diameter. The rotary needs 1153 CFM to produce 600 rwhp. A K&N 9 inch long by 6 inch diameter flows 1188 at one inch of water. A 4.5 inch filter of the same diameter flows just 594 CFM. Of course that doesn’t mean the shorter filter won’t pass enough air for 600, it is just that it will be restrictive.

I see some who don’t have room for a proper filter using the open ended filters. An open ended filter, according to K&N, isn’t much better flowing 600 with a 5.5 inch length.

 System No No Number Four

Roasting the front rotor charge air

Cam Worth of Pettit Racing was dynoing a single turbo and getting mixed signals. He noticed the cherry red (1800 F) turbine housing was close to the front two LIM runners and could be the cause. He simply found a piece of stainless steel and placed it between the hotside housing and the LIM. The overall AFR on the next run richened a whole point!

Given the change was effecting one rotor and it moved the global reading one point, i e from 13 to 12, the front rotor was TWO full points lean!

The LIM is made of aluminum, one of the most heat receptive materials on our planet. Heat from the turbo had heated the front runners making the charge air expand and therefore contain less oxygen compared to the cooler rear two runners.

Of course there are numerous manifolds that place the turbo a distance from the LIM but there are many where this is not the case. Most heat shielding including turbo blankets eventually heats and then transfers heat into the LIM.

Most…  (stay tuned)

 System No No Number Five

 Lack of respect for flow dynamics.

‘Nothing complicated here, just the application of common sense. Since an engine is simply an air pump we want to get as much air in and out as possible. The more in and out the more power and happier the motor.

Let’s first focus on the DRIVER of the entire flow, the exhaust side of the motor. The combustion power both turns the crankshaft AND drives the turbine which powers the compressor which powers the motor..

Other than port rework and doing our best to reduce compression leak down (see Engine Section) there isn’t much we can do inside the motor.

There is a huge opportunity to efficiently harness the power of the exhaust flow.

The typical engine loses 40% of its power out the exhaust. One of the primary positives of turbocharging is that we are able to capture a great deal of that power and apply it to a power multiplier, the turbo.

How much?

It takes 100 hp to drive the typical turbo compressor that is delivering enough air (960 CFM) to make 500 rotary rwhp! Borg Warner measures the speed of the exhaust between the exhaust port and turbine wheel in terms of Mach, in other words somewhere around 500 mph.

Enter the under-appreciated turbo manifold, the design of which almost always seems to be influenced more by packaging than flow engineering.

Until now.

The CPR manifold is designed with a single objective placed Number One on the design tree:


Before I get in to the nuts and bolts it might be good to start with the bottom line.  403 rwhp (SAE) at 5000 RPM! While most look at the top hp tick when they see a dyno sheet it is the overall hp curve throughout the RPM band that wins races. After you shift you are looking at 5500 or so… so what do you have at 5500 RPM? How about 448!

The rpm signal was lost around 7800 but the power is good at 8900. Great mid-range and excellent power up to almost 9000.

I ran my manifold at the Texas Mile in 2013. (165 mph between the ¼ and 3/8 mile marker).

Proper manifold engineering is all about exhaust back pressure versus boost.

How about 13.4 psi of back pressure at 18.8 psi boost at 4098 rpm at 35% throttle!   

It is all in the details and the manifold system is an integral part.

There are numerous single turbo manifold options for the FD. An optimized manifold is a vastly underrated link in the 13BREW power chain. Most manifolds are “designed” by welders and packaging is typically at the top of the design tree. This conclusion on my part is purely observational as looking at various manifolds I have no other explanation as to the why of where various items are positioned.

Turbos make us sloppy.

They provide a big hammer to slam air into our motors. Simply stated, it is easy to make a lot of power by hanging a turbo on the rotary. Anywhere.  Anyway.

I don’t do sloppy. Having raced for 17 seasons, the last 6 for a National Championship in an ultra competitive class I know where “sloppy” finishes. Sloppy engineering did not produce lap records at Road America, Brainerd International Raceway, Mid Ohio Sportscar Course, Indianapolis Raceway Park, BlackHawk Farms or under the lap record at Road Atlanta as well as 27 SCCA GT3 National wins including two June Sprints wins and a Second at the Runoffs at Road Atlanta.

                                                                                                                                                                                SYSTEM DESIGN

Let’s start with how not to design a system::  

 Setup No No Number One


 And flow is everything

Let’s take a closer look at the engineering behind the CPR manifold:

All stainless steel of course.  All bends and flanges are pipe, not thin walled tubing. Wall thickness retains heat and conveys it to the driven wheel while providing the strength to support a 20 plus pound turbo. No thin walled tubing in sight and no cracks in the future.

As mentioned previously, the rotary exhaust port is round and 50 mm in diameter and 3.04 square inches of area.

The CPR manifold inside runner area is 52.5 mm diameter and 3.35 square inches area.

Since the runner turns after the ½ inch thick manifold flange the additional area is welcome so as to promote unencumbered (by drag) flow. The first turn out of the engine is the most important flow-wise and needs to be as smooth and gradual as possible.

After the turn the CPR  manifold presents a straight shot to the driven wheel.

The straight portion of the runner starts with the same area as the turn but is designed to  linearly neck down to the area of the T4 footprint which is 2.69 square inches.

A primary challenge is presented:

Exhaust port, round and 3.04 square inches area

Turbine port rectangular and 11.5% less area.

How to get from point A to point B while changing from round to rectangular LINEARLY? All manifolds are confronted with the same challenge.

CPR wanted a perfectly executed solution and invested a significant amount of time and money for the ultimate solution: we have constructed four separate dies that go from round to a perfect T4 fit. Two each are joined longitudinally. As a consequence the manifold is constructed using four entirely different straight longitudinal sections.

The following year GM released details on the engineering behind their twin turbo V6.

Similar to the Ecoboost four, Cadillac cast the turbo manifold as part of the head so as to reduce runner volume and place the driven turbine wheel as close to the driving force as possible.

I also find their interest in reducing volume between the compressor and engine instructive.

“Patented low-volume charge-air cooling

Cadillac’s patented, manifold-integrated water-to-air charge cooling system also contributes to more immediate torque response, because the compressors blow through very short pipes up to the intercooler.

With no circuitous heat-exchanger tubing, there is essentially no lag with the response of the turbochargers. Airflow routing volume is reduced by 60 percent when compared with a conventional design that features a remotely mounted heat exchanger.

“It is a very short path from the compressors to the intake ports,” said Bartlett. “The compressors draw their air directly from the inlet box and send their pressurized air through the intercooler immediately for a tremendous feeling of power on demand.”

Run your finger over the engine flanges and round initial runner and the turbo flanges and upper runner and you will feel nothing but a smooth transition.

A very short trip from the turbo to intercooler.

GM notes the benefits:

“immediate torque response, because the compressors blow through very short pipes up to the intercooler. there is essentially no lag with the response of the turbochargers.””

As we consider charge air cooling volume front mounted intercoolers especially come to mind. Both higher runner volume to the intercooler and bends are significant drawbacks. My design features minimal runner volume and one bend.

I prefer the stock location intercooler (Pettit Coolcharge 3) to the V mount as it retains the stock location radiator, doesn’t require messing with the hood, adds engine bay space while delivering equal cooling.

In keeping with short runner length, note the ultra short straight mating with the large stock location intercooler. The Pettit Cool Charge 3 is my pick. I measure (thermocouples) temperature out of the turbo and after the intercooler and the Cool Charge III removes 130 degrees F.

The stock location IC delivers major advantages over a front mount in that  the fins are mostly protected from road junk, runner volume is vastly reduced, the radiator remains in its’ most efficient (OE) position, and all important front weight is significantly reduced.

While I am at it I recommend you locate your BOV on a flat surface on the intercooler end tank. That way you are not carving a 2.5 inch hole in a 2.75 inch tube and disturbing flow into the throttle body.  Note location in the following picture.

And speaking of cooling, please note the Thermocouple located on the intercooler intake pipe. Unlike any other type of thermo-sensor, a Thermocouple generates temperature output accurate within a few degrees and a quarter of a second!  More on that in the tuning section.

There is but ONE modest bend in the flow between the engine and turbine wheel. Almost all other manifolds have at least two and they are closer to 90 degrees.

CPR turbo location, as previously discussed is due to the magic of Mica. While the turbine housing, which can reach as much as 1800F is close to the LIM virtually no heat penetrates the Mica barrier. The LIM in this photo is the Ground Zero item however both the OE LIM and Elite Rotary Shop LIM provide clearance.  

Note that the wastegate flow has NO bends and joins the downpipe at a friendly to flow angle.

Note that the heat sensitive end of the wastegate is nowhere near a heat source.

Instead of a bulky dash 10 Aeroquip line with a number of large aluminum fittings a purpose bent 2 piece powder coated tube returns oil from the turbo bearing to the engine.

Exhaust gas temperature bungs and an exhaust backpressure line fully instrument the manifold.

The downpipe features two O2 sensor bungs, one for the ECU and one for the dyno.

You may note a V band connection about a foot from the turbo. I built this downpipe so as to be able to swap in different turbos so I have a number of upper sections that connect at the flange.

Comparing the CPR manifold with the typical manifold, we find smaller diameter runners, two additional 90 degree turns, long runner volume which decreases the combustion impulse/heat, and at least one wastegate port located on the outside wall of the turn.