Dyno Shootout: Battle between Dinan and RD Sport for 4.6 Liter Stroker Motor Bragging Rights
Introduction
From the time Dinan and RD Sport each introduced their 4.6L stroker motors, it's always been our dream to have a dyno shootout to see how they would match up against each other. Both companies make 4.6 liter stroker motors, but each took a slightly different approach in their design. Dinan chose to design a shorter stroke and bigger bore, while RD Sport chose to design a longer stroke and slightly smaller bore. The shorter stroke approach gives the Dinan stroker a 4608 cc displacement, and the longer stroke approach gives RD Sport a 4619 cc displacement. Practically speaking, both engines are the same displacement, but in theory the longer stroke of the RD engine should give it a torque advantage. We always wanted to put this theory to the test, so we called up our buddy "Mr. Data Collector" who would set it up and collect all the data.
The Dinan stroker motor was purchased by Alekshop customer "Dray-M3." This car is well known to Alekshop dyno days and has been dyno'd on three previous occasions. Dray-M3 always wanted to dyno his car, but we wanted to wait until Alekshop customer "Sleeper" finished his RD Sport stroker so we could dyno them together and turn this into a mini stroker shootout. But scheduling this shootout wasn't as easy as it sounds. It seemed that everybody's schedules never meshed. After six months of trying, we finally found a one-week window of opportunity where everybody was available. Not wanting to pass up this golden opportunity, we set it up and made it happen.
The Dinan Stroker
The Dinan stroker comes in a complete turn-key package. If you don't want to send in your own motor in advance, Dinan will build up one of their cores and ship you the engine as soon as it's completed. They charge you a nominal core charge which is refunded as soon as your engine is received. To gain maximum power from the Dinan stroker, Dinan also recommends to purchase Dinan stage-2 intake, Dinan throttle bodies, 16% underdrive pulley, and free flow exhaust. Although these accessories cost extra, Dinan does list them as optional to achieve maximum power.
Price: $25,999, includes:- Bore: 94mm / Stroke: 83mm (4608 cc displacement)
- Compression Ratio: 12.0:1
- Dinan proprietary billet crankshaft
- Dinan proprietary lightweight forged pistons
- Dinan proprietary light-weight connecting rods
- Balanced and blueprinted
- Dinan electronics and engine management software
- Dinan serial numbered block
Optional Equipment / Expenses:- Exhaust
- Under drive pulley
- Stage-2 inake
- Throttle bodies
- Installation
Rated power output (measured at crankshaft):- 502 horsepower @ 7500-7800 RPMs *
- 384 ft-lbs torque @ 5600 RPMs *
- 527 horsepower @ 7800 RPMs **
- 407 ft-lbs torque @ 5200 RPMs **
* Engine tested using 93 octane with High Flow Intake Stage 2, Throttle Bodies, 16% underdrive pulley and Free Flow Mufflers
** Engine tested same as (*) above, but with BOTH CAT delete, Dinan racing mid-pipe, and Dinan racing exhaust.
The Dinan crankshaft is a top quality piece. It's manufactured from billet steel at a highly reputable crankshaft manufacturer who specializes in these types of custom builds. Dinan uses Mahle pistons made to their specifications. The pistons are made from the same manufacturing line as the factory BMW pistons, thus guarantees their compatibility with the S65's Alusil engine block. Dinan seemed to skimp a little on the connecting rods. Though they are made by Carrillo, Dinan chose to use the Carrillo A-Beam connecting rods -- which are considered a "budget" connecting rod. The A-Beam is plenty strong for this application, but you wouldn't want to supercharge this engine with the A-Beam connecting rod. Since most people aren't "boosting" their stroker motors, the A-Beam rod should not dissuade anybody from buying this stroker motor.
I found only one nit against the Dinan stroker: it's the use of a 94mm bore. Old rule of thumb says you shouldn't bore more than 2mm over stock, lest the cylinder walls become too thin and you can't rebuild the engine beyond this point. The stock bore starts at 92mm, so boring to 94mm means you're at the limits of the cylinder walls and may not have any options except replacing the motor should you ever need to rebuild it. Dinan believes the extra bore size was important to meet their philosophy of making the engine as "square" as possible (getting the bore size equal to the stroke length). Many engine builders believe this too and are willing to make this trade off. Hopefully our dyno test will see how well this works.
The RD Sport Stroker
The RD Sport stroker also comes in a complete turn-key package. Just as with Dinan, if you don't want to send in your motor in advance, RD Sport will build one for you from one of their available cores. The RD Sport stroker comes in two flavors: 1) Basic Stroker, 2) Full Stroker Package. RD Sport also offers custom stroker packages using custom strokes (82mm - 85mm), custom bore sizes (up to 94mm,), low compression pistons for supercharged applications, and Carrillo H-Beam-HD connecting rods for supercharged stroker applications. RD Sport has built both high and low compression stroker motors from 4.4L to 4.7L displacements.
Price: $23,995 includes (Basic Stroker Package)- Bore: 93mm / Stroker: 85mm (4619 cc displacement)
- Compression Ratio: 12.0:1
- RD Sport billet crankshaft
- Mahle lightweight forged pistons
- Carrillo H-Beam connecting rods
- Balanced and blueprinted
- 16% Underdrive pulley
- RD Sport engine management software
Price: $32,995 includes (Full Stroker Package)- All of the above
- RD Sport proprietary long tube headers
- RD Sport high flow CATs
- RD Sport mid pipe
- RD Sport high flow exhaust
Optional Equipment / Expenses ***- Front bumper which also serves more air to the intake system
- Installation
Rated power output (measured at crankshaft):- 480 horsepower @ 7700 RPMs *
- 387 ft-lbs @ 4800 RPMs *
- 525 horsepower @ 7700 RPMs **
- 425 ft-lbs @ 4800 RPMs **
* Basic Stroker Package tested with 91 octane gasoline, stock exhaust
** Full Stroker Package tested with 96 octane gasoline
*** Installation is free when RD Sport has access to the car
The RD Sport crankshaft is also a top quality piece. Also made from billet steel, this crankshaft comes from an equally reputable crankshaft manufacturer who specializes in these types of custom builds. RD Sport uses Mahle pistons made to their specifications. The pistons are made from the same manufacturing line as the factory BMW pistons, thus guarantees their compatibility with the S65's Alusil engine block. Instead of using the Carrillo "budget" A-Beam connecting rod, RD Sport uses the stronger and ($500 more expensive) H-Beam connecting rod. But RD Sport also offers the Carrillo H-Beam-HD connecting rod for low compression supercharged stroker motors.
I also found one nit against the RD Stroker. If you live near RD Sport facilities, they will install your engine for free as part of the price. But if you don't live nearby or can't ship your car, there is no cash allowance or rebate for the installation. RD Sport explains that they offer the installation service as complimentary, but really isn't included as part of the price. Even without this allowance, sending the car to RD Sport is worth the extra money, because it's still cheaper to send the car on a round trip journey than it is to pay your local shop to perform the installation.
A Third Entry into the battle
We originally planned a head's up match between the two strokers. But after thinking about it, we decided to add a third car into the mix. The Alekshop M3 is a 2013 Limerock Edition that is being build as US Spec M3 GTS. As of today it still has a stock 4.0 Engine. But we thought it would be nice to add this car to the mix because it has enough bolt-on performance enhancers that might put it into the running.
Testing Methodology
Over the past few years, we've run many dyno days and tested approximately 40-50 BMW M3's. We test each car with the same methodology and as time goes on, we have developed the ability to data log many important parameters and incorporate them into our dyno charts. Today's methodology is as follows:
- Neither Dinan nor RD Sport were notified in advance of this test.
- Three or more dyno runs until the car doesn't make any more power.
- Use best three runs, regardless.
- Dyno each car in same gear (4th gear).
- Attempt to dyno each car at same engine temperatures.
- Heat soak test the car to see if it degrades performance. Runs are usually about 2-minutes apart. This induces a heat soak test to see how the car performs under stressful back to back conditions.
- Data Logging with BT Tool
- RPM
- Throttle Position
- Gear Selection
- Intake Air Temperature (IAT)
- Spark Advance (can see knock)
- Both O2 Sensors (converts to Air-Fuel-Ratio)
- Oil Temperature
- Water Temperature
- Data Logging with Kestrel Weather Station. This allows us to verify accuracy of Dyno weather station and the Dyno horsepower correction formulas. This prevents cheating.
- Temperature
- Barometric pressure
- Humidity
- Density Altitude
- Filming. All runs filmed without breaks from start to finish.
Prices as tested (MSRP prices, excluding installation):
Dinan price as tested: $35,496
- Dinan 4.6L Stroker Motor
- Dinan Throttle Bodies
- Dinan Underdrive Pulley
- Dinan Stage-2 Intake
- Akrapovic Evolution Exhaust
RD Sport price as tested: $29,995
- RD Sport 4.6L Stroker Motor
- RD Sport Underdrive Pulley
- Akrapovic Evolution Exhaust
Alekshop M3 price as tested: $$$ Don't even ask. $$$
Results
This is the part of the report we call the "Data Storm." We will present the data we collected, and let you be the judge of what it means. These results will certainly spark a controversy and a heated debate. At the very bottom, we will make some observations. We only ask that you post your opinions in a respectful manner.
Dyno Charts (SAE Correction):
Dyno Charts (STD Correction):
Dyno Charts (Uncorrected):
Does this really matter?
Out of our own curiosity, we decided to graph the engine data logs during the entire dyno session to see how the temperatures changed during the entire event.
Dinan
RD Sport
Alekshop M3
Post Mortem
To say the least, we were shocked by the results. The RD Sport handily beat the Dinan stroker, and the Alekshop M3 even beat the Dinan stroker. The extra torque of the RD Sport stroker is overwhelming and evident. The RD Stroker has a consistent torque advantage over the Dinan stroker from start to finish. But we were shocked that the Alekshop M3 beat the Dinan stroker. So we asked "Mr. Data Collector" to dig deeper into the results to see what he could discover the reasons.
It's our belief that there's a few things wrong with the Dinan tune. We can see from the data logs that the Dinan ECU starts closing the throttle bodies around 5500 RPMs and doesn't fully open them even to redline. This appears to be in response to some knock events because the throttle bodies begin to close around the same time we see spark retarding due to knock. Just to ensure the throttle bodies weren't closing due to dyno operator error, we looked at the data logs for all Dinan runs and we see the same exact closing for every run (see supporting data below).
The Dinan ECU is also very conservative on spark advance having a min of 8 degrees advance and max of 27 degress. Compared to the others, this seems far too conservative. Both the RD Sport and ESS ECU have minimum 15 degrees advance and maximum 34 degrees advance. The Dinan Stage-2 Intake also seems to retain or pass along more heat than the factory intake. Even though the ambient temperature was coldest during the Dinan dyno runs, the data logs show the Dinan intake air temperatures (IAT's) were significantly higher than the other two cars (see supporting details below).
After running this test, both Dinan and RD Sport were notified of the results. Both companies responded with the same comments: that's not our latest ECU files! I'm not sure it would have mattered because it appears the RD Stroker has a sizeable torque advantage, but it's unknown how much of this advantage is due to the different ECU tuning. As of this writing, the Dinan dyno files and data logs have been sent to the car's owner, who at the request of Dinan, will turn them over to Dinan for review. Following review, it is our belief that Dinan will retune the car. In the mean time, RD Sport has also shown an interest in retuning their customer's car. So it sounds like we have all the makings of a rematch. Stay tuned!