By Chuck Johnson of Moto-IQ
In the last three years, it seems that I’ve said it over a thousand times. When it comes to land speed racing, take most everything you know about racing and throw it away. There are so many generally accepted practices in motorsports and preconceived notions about racing that just don’t apply when it comes to land speed racing. In fact, much of the time these common practices are the polar opposite of the practices standard to that of building a car for Bonneville. Land speed racing is the realm of motorsports where lead weights are added to cars, wide tires are replaced with skinny ones, and the thought of replacing the factory brakes with an exotic multi-piston brake kit is considered to be a foolish investment.
In the same sense, where most racers would consider changes in displacement only in one direction (larger), the land speed racer will do whatever it takes to set a land speed record even if it means decreasing an engine’s displacement. Why did we choose this route though?
Winston Churchill once said, “Seize the opportunity in every difficulty.” Well, our difficulties started while going through tech inspection during the last race of the season at El Mirage. See, up until that point we had been chasing the G-BGC (1.51 L to 2.0 L Blown, Gas, Coupe) record. And, one of the stipulations to run in that particular class is an engine swap. No problem right? We swapped an SR20DET into a 240SX. Wrong! Apparently, in the eyes of the SCTA we essentially just recreated a Japanese spec car (a late model 180SX). Long story short, this placed us back in the Production class… where the record was over 226 MPH! Shit.
Producing over 900 WHP, the Raver Motorsports Mitsubishi Galant VR4 has set G/PS records in excess of 220 MPH at both Bonneville and El Mirage. Photo courtesy of Vernon Brunges.
Here’s where “seizing the opportunity in every difficulty” comes into play… although I would like to think of it as shear brilliance. The record in the production class for a 1.51 L to 2.0 L was 226 MPH by an AWD Galant and the other an AWD Audi. The Production class is the only place an AWD car is allowed to compete since it provides such a distinct advantage. However, for a 1.0 to 1.5L engine, the Production class record remained a more reasonable 167 MPH at Bonneville and 135 MPH at El Mirage. Inspiration! We’ll simply reduce the SR20DET’s displacement. Necessity is the mother of invention isn’t it?
Look at the miniscule distance between TDC and BDC. This surely isn’t 86 MM of stroke!
Removing 25% or one cylinder’s worth of displacement from an engine is easier said than done though. My first instinct was to have some custom sleeves made to decrease the bore to 83.0 MM and use an SR16VE crankshaft with 68.7 MM of stroke. It seemed easy enough, but there were actually many complications and disadvantages that came along with it. The result of de-boring the cylinders would leave a step where the 86mm diameter combustion chambers met the smaller 83.0 mm bore sleeves. This wasn’t exactly ideal for the translation of combustion pressures into the rotating assembly. Also, this mismatch in diameters would require that notches be machined into the smaller sleeves to ensure proper valve clearance and even then the flow would most likely be shrouded by the smaller diameter bores. And what about the head gasket? These were just a few of the challenges… It was time to focus our attention on modifying the crankshaft instead.
Since a high quality billet crankshaft for a four cylinder engine starts at around $3,000, we were fortunate enough that Nissan made the SR16VE. The SR16VE still utilizes an 86 MM bore, but the stroke has been reduced to 68.7 MM to net the 1.6L of displacement. The stroke of the factory SR16VE would get us close enough so that we could have the connecting rods journals welded and then offset ground towards the crank centerline to reduce the stroke. Jackpot!
Since the SR16VE was never offered in the U.S., finding a crankshaft from one could prove challenging. Through text messages, Facebook status updates, and a few good ol’ fashion phone calls, we put the word out to the Nissan community. Eventually, an old SE-R buddy of mine Chiris Allen told me that Greg Vogel of G-Spec Performance (another old school SE-R buddy) might have a stash of SR16VE cranks lying around. I should have figured that Greg had one since his business G-spec Performance specializes in stocking those hard to find Nissan race bits. The rest is history from there.
The process of destroking a crankshaft is best described as tedious and if done right, methodical. To be certain that this methodical process was properly executed, I turned to one of the best crankshaft guys I know in the industry, Joe Castillo of Castillo’s Crankshaft Service.
Joe Castillo starts out by welding one rod journal at a time. After a journal is welded, the crankshaft is straightened. This process of welding and straightening is repeated again and again until all four journals are done. Straightening the crank after each rod journal is welded helps ensure that the main journals remain coaxial and on centerline.
Once the welding process is complete, the journals are each rough ground, leaving .080″ of excess material diametrically and about .015″ in width. Since we are de-stroking the engine to 1.5L, our journals were offset ground towards the crankshaft centerline by 2.6 MM or .102″. (2.6 MM = ((68.7 MM – 63.5 MM) /2). On a typical stroker crank, the journals would be moved away from the center line to increase the throw of the crankshaft (stroke).
With the rough grinding complete, the crankshaft is then placed in an oven for four hours at 980 degrees. After the four hour period, the oven is turned off and left to cool slowly overnight. By the time the morning rolls around the oven has cooled to around 280 degrees. The doors are cracked slightly and the crank is slowly brought down to ambient temperature. This process helps relieve internal stresses that resulted from the welding process.
The crank is then checked and straightened again if necessary. It is then rough ground again, but this time to .025″ in diameter and .005″ in width. Following that the oil holes are deburred and cleaned. The tops of the welds are also deburred. The journal is then finish ground to size and the oil holes chamfered and tear dropped.
Our crank was finish ground slightly undersized to allow for the buildup, which occurs during the plasma ion nitriding process. Plasma ion nitriding is a case hardening process that produces a thin, yet hard shell on the surface of the journal which functions optimally as a bearing surface. Once returned from the ion plasma nitirde process, the journals are then polished to remove the chalky build up caused from the heat treating process. Finalyy, the crankshaft is straightened again.
Since the welding process throws the crank out of balance, Joe Castillo rebalanced our destroker crankshaft. Then, the entire rotating assembly (crank, rods, and pistons) were balanced as a unit.
With a stroke that was 22.5MM (.886″) shorter in throw, definite changes were in order for the connecting rods and pistons. Using standard SR20DET length connecting rods and pistons would place the piston deep in the hole at TDC; in turn, resulting in a terribly low compression ratio, quench of the air fuel mixture, and a number of other incredibly stupid, undesirable things.
One of the advantages that came with de-stroking our engine versus de-boring it was the freedom to now fill this space at TDC with a longer connecting rod and optimize rod ratio. Perhaps out of habit, I fell back on K1 Technologies’ 4340 forged H-Beam version of the Honda H22A connecting rod again. We’ve had a lot of luck using this rod on our other SR20 long rod engines. The H22A rod length is 5.636″ which is .272″ longer than a factory SR20 rod which measures 5.364″.
The K1 Technologies’ H22A rod is longer than the standard SR20 rod, yet shares the same bearing shell thicknesses along with BE and PE diameters. Lastly, its width can be trimmed slightly to fit in between the cheeks of the factory SR20 crankshaft. However, in this case it wasn’t necessary to modify the BE width of the connecting rod. Instead, Joe Castillo opened up the distance in between the SR20DET crank cheeks by .044″ to .947″ wide to accommodate the wider .938″ BE width of the K1 Technology’s H22A connecting rod.
A custom JE piston was the last component necessary to make the bottom end of our de-stroked, long rod engine work. Although the longer H22A rod brought us closer to the top of the block, we still had an additional .172″ to account for.
Normally in motorsports or high performance applications, the pin height of a piston decreases and the piston itself gets shorter as an engine becomes more exotic.
In this case though, we increased the pin height to 1.427″ to bring the deck of the piston back up to the deck of the block at TDC and still allow .005″ of deck clearance. (The original SR20DET piston has a pin height of 1.260″, which is .167″ shorter than our set of JE Pistons.)
Having spent almost a decade of my life working at JE Pistons, the pistons were obviously one of my most favorite parts of this engine build. Not just because I was a “piston guy” though. When I transitioned from being a piston designer to an engineering manager, my sense of accomplishment also changed. My pleasure was no longer from saying, “I designed that part” but rather, by developing a talented team that was responsible for designing thousands of badass parts for the top tiers of motorsports.
Yes, I conceptualized the piston but, the design you see before you today came from a talented team of individuals whose personal and professional development I had the pleasure to be a part of. Dane Kalinowski, JE’s Product Development Engineer, developed the forged, asymmetrical structure while Josh Wang, an Application Engineer, designed the trick 3D milled undercrown and spec’d the complex skirt profile.
Finally, a promising young engineering tech named Joe Popovits, designed the piston crown as part of a fun, personal development type project. Using my input on piston to valve clearance and then 3D scanning the combustion chambers with a Hexagon Romer Arm, Joe came up with this rather trick piston crown design through a series of design iterations.
There is a certain sense of satisfaction that comes from knowing that you helped people grow both as a person and a professional. And this sense of satisfaction cannot be dampened by any amount of Office Space shenanigans. It was my pleasure to work with such talented and passionate team… but please allow me to digress (quickly) from this personal tangent.
Ultimately, the combination of the 5.636″ long K1 Technology connecting rod and decreased 2.500″ stroke would result in an impressive rod ratio of 2.25:1. Perhaps the next time around we’ll try out the much longer Honda F20C rod, which would yield a rod ratio of 2.41:1 and a much shorter, modern piston height of 1.040″. I’m honestly not too sure if this high of a rod ratio would be a benefit or a detriment in terms of performance. Is there a point when a rod ratio is too high? I would imagine so, but where is that point for our engine?
To help compensate for the loss of displacement, the MotoIQ H.N.I.C. (head nerd in charge) Mike Kojima offered up a super rare, high flowing SR20VE 20V cylinder head that he had stashed away in storage. The SR20VE 20V was the last iteration of the SR head that Nissan would produce before finally doing away with the SR engine family. The 20V designation had nothing to do with the number of valves in the cylinder head (it still had 16 valves). What “20V” means is irrelevant. What’s important is the improvements that the 20V head brings to the game.
The 20V cylinder head was the very last of the SR20 heads designed by Nissan. According to Nick Hunter of 5523 Motorsports, much improved flow came as a result of the 20V’s unique intake flange (mouth) profile and the port design itself, which moved the divider walls closer to the valves. The intake flange of the intake manifold also divorced the injector tip from the intake runner unlike previous iterations of SR20 cylinder heads. In doing so, cleaner flow through the intake runners was achieved.
To further improve the 20V’s flow capabilities, the stems of both the intake and exhaust valve stems were reduced in diameter from 6MM to 5.5MM and were further undercut behind the head of the valve. This not only helped improve flow through the intake and exhaust ports, but also reduced valvetrain mass to improve the already badass high, RPM stability of the SR20VE VVL cylinder head’s shaft mounted rocker system.
The longer valves and unique long reach spark plug design of the SR20VE 20V cylinder head is evidence of another one of Nissan’s improvements over the previous SR20DET, SR20VE, and SR16VE cylinder heads. Nissan opened up the cooling passages inside the cylinder head to help address one of the Achilles heels of the SR engine family, poor coolant flow.
So this is the basic DNA of the record breaking engine that we’ve dubbed the SR15VET 20V. In the next article, we’ll meet the “23 doctor”, Nick Hunter of 5523 Motorsports, who was responsible for bringing this unconventional idea to life. Stay tuned, for an even more intimate look into the heart of our record breaker.
Article by Moto-IQ