Auto Technology Repair, AKA ATR Performance, AKA Highline Car Care is the culmination of over 20 years of automotive passion and knowhow. Located in Gilbert, AZ – You’ll find our storefront – Highline Car Care at 1372 N Marvin st. WEBSITE here Why so many names? Because we never stop innovating, and we would like to cater to each customer base in a unique and individual manner. Lets set the other two aside for now and talk about a passion project ATR Performance has been developing in 2020 and 2021 (COVID left us with some extra time on our hands)

2010 Nissan GTR – The beginnings

If you’ve been following us any length of time, you might know of our shop GTR – More info on its beginnings HERE. This car started off as somewhat of a rescue vehicle. It had been damaged in a minor front/rear collision (no sheet metal was damaged) and essentially abandoned at a local body shop. We were able to purchase this vehicle from the body shop directly, and the passion began. At first, it was an effort to simply reassemble the vehicle and have a little fun. We never intended to keep it more than maybe 5-6 months. Well, 5 years later its still here – and badder than ever!

Pushing the limits of the R35 Nissan GTR

The R35 nomenclature refers to the 2009-2022 Nissan GTR. It was equipped with a VR38 engine and GR6 dual clutch transmission, uniquely located in the rear of the vehicle. More info on the R35 HERE. This platform was able to provide roughly 500hp from the factory, and varied by production model. Straight off the lot it was an exhilarating ride with crisp clean shifts, and a 0-60 that would rival just about any supercar.

This was fun for a bit, but we decided we wanted a little more kick in the pants, and Project GTR 8.0 began. Follow us for the step by step research and development we have laid out on our quest for an 8.0 second quarter mile at approximately 175mph.

The FBO R35 GTR

FBO stands for full bolt on. This encompasses everything that can be done with the car while retaining the stock engine internals and turbos. Please notate that many of these modifications are not legal for street usage. We were able to test these items on a local dyno and private drag racing facility. Please also notate that installation of all of these items WILL require software tuning to compensate. We will go over that towards the end. Some of the basics are as follows:

FBO exhaust

• Installation of downpipes. The primary catalytic converters are located directly downstream of the stock IHI turbocharges. They are responsible for cleaning up the exhaust emissions. As we found though, they are also quite restrictive to the flow of exhaust and actually limit turbo output. We went with ETS 3″ downpipes.
• Installation of aftermarket midpipe. The stock midpipe contains the secondary catalytic converters and is also quite restrictive. We installed an ETS 4″ inlet downpipe that splits off into dual 3″ outlets. Once downpipes and mid pipe were installed, we noticed a 2psi increase in turbo boost output. In our study, this added approximately 35 horsepower. This was however, met with an engine over boost error code that would have to be addressed through tuning.
• We retained the factory exhaust and mufflers which are located downstream of the catalytic converters and mid pipe. We did not find this to be a limiting factor at these power levels

FBO air intakes

We found that the stock air intake piping and air filters are quite restrictive – They are designed to muffle air intake noise from the factor, and thus to not flow optimally. The restriction in airflow became evident when we attempted to turn the boost above 15psi, so we upgraded:

• Cobb Big SF 3″ air intakes. This would allow us to EVENTUALLY (more below) run up to 28-30 psi of boost without restriction

FBO flex fuel

As we found very shortly after installing better flowing air intakes and exhaust components, and increase the boost levels – 91 octane fuel was no longer sufficient. It was prone to predetonation (also known as knock) when boost levels were increased past 15-16psi. The solution? Flex fuel (also known as ethanol). Select gas stations around the Gilbert and Phoenix, AZ area sell ethanol flex fuel straight from the pump, and it is quite economical. Please notate, that most pump handles are yellow and the pump is labeled “E85 flex fuel”. An interesting note is that this E85 flex fuel is legally allowed to be 54% all the way to 98% ethanol content. The remaining content is regular gasoline. For general purposed, more ethanol content will allow more boost (more on results below) Supporting ethanol components are as follows:

• Flex fuel sensor. This sensor will allow the engine computer to analyze the ethanol content in the fuel, and adjust timing and boost accordingly. It is most commonly mounted on the passenger side firewall, on the fuel return line (line RETURNING to fuel tank from the engine). To communicate with the ECU, we hijack the air injection MAF sensor for a plug and play connection. We opted for the Visconti kit at this time, although replaced that later down the road due to its shape, size, and lack of customer support by the manufacturer
• Upgraded fuel pumps. We found ethanol to be quite corrosive, and not friendly with the factory fuel pumps. In addition to this, we found that approximately 25% more fuel quantity is required when running ethanol vs pump gas. For these reasons, we opted to upgrade the fuel pumps using dual DW300 (DeatschWerks) fuel pumps. These pumps allowed us to retain the factory fuel pump basket, though we moved away from this setup as power levels increased past 690 horsepower at a later point in time.
• Fuel injectors. We actually tried two different sized fuel injectors. At first we started with the Injector Dynamics 1050X which flow approximately 1000cc. We found that these injectors like to hang open once the duty cycle is pushed past 85-90% duty cycle though. We were approaching this at FBO levels, and opted to install the Injector Dynamics 1300x injectors which will run approximately 60% duty cycle at FBO levels.
• Speed Density sensor. The GTR uses MAF (mass airflow) sensors in stock configuration. These sensors will physically monitor the amount of air that enters the engine. They also monitor the AIT (air intake temperature). With this data the total air mass the engine is ingesting is calculated. Once total air mass is calculated, the engine computer takes this data to mathematically calculate engine load. Engine load data is used to calculated fueling and ignition requirements at any given point in time that the engine is operating. On the GTR we found another very important function of engine load – It tells the transmission what to do. The GR6 transmission found in the GTR is very sensitive to engine load figures, this will cause it to upshift and downshift, raise and lower line and clutch fluid pressures, among other things. As we increased our power levels past stock, we found the engine load data to be inconsistent at times. One of the big reasons we noticed, is that the MAF sensors measure the air temperature PRE turbo. As we increased boost pressure though, post turbo air temperatures increased as much as 20%. The stock MAF sensors cannot detect or compensate for this. This is when we decided to convert the engine to SD tuning configuration (Speed Density). As we learned, SD tuning is the most accurate way to tune and engine for maximum performance and drivability. We replace the passenger side boost sensor (located at the charge pipe just before the passenger side throttle body with a 4 wire TMAP sensor. The “T” being the important part – This sensor is now able to measure charge air temperature (IAT) which is after it has passed through the turbos and intercoolers. This gives us a much more precise reading of the actual temperature of the air as it enters the engine. This new sensor required an adapter harness to send the additional temperature info to the computer. Several companies make this plug n play harness, though we opted for the Boost Logic unit. The GTR in stock configuration also has a MAP (manifold absolute pressure) sensor that is located in the upper intake plenum. Absolute pressure is defined as pressure above a zero reference (a perfect vacuum). With the engine off, at sea level, at an average temperature, the MAP sensor should read approximately 14.7 psi, or 1 bar. In stock configuration the MAP sensor monitors boost and not a whole lot more. In SD configuration, we use the MAP sensor in conjunction with the TMAP sensor and a theoretical VE (volumetric efficiency) table to calculate engine load and air mass. At this point, it is prudent to discuss VE. Think of an engine as a big vacuum pump that consumes air. We must now create a table showing engine speed vs manifold absolute pressure so that the computer can reference theoretical volumetric efficiency. Once we’ve done this, SD tuning is a snap. The ECU will provide timing and fueling based on manifold pressure, engine RPM, and charge air temp (IAT). We found this to be a much more accurate way to operate the engine with higher than stock power levels. Circling back around to the transmission and its required load signal, we now have a load value calculated by ignition timing and VE. The last thing we had to do was adjust the torque tables inside of the ECU, so that the computer is expecting the actual torque the engine is supplying at any given RPM and load level. Once this is configured, the GR6 transmission became much smoother and user friendly than with the previous MAF tuning.
• Software tuning. When we acquired our GTR, it was running on Cobb engine and transmission management. Cobb was OK at producing FBO power, but we found the user interface to be extremely tedious. We did send the car to a local tuner for flex fuel tuning, and were able to produce approximately 580 wheel horsepower. As the months after progressed, we found ourselves running into occasional hiccups and random drivability issues that we were unable to diagnose, monitor, or remedy. We decided to take the car into the twenty first century and upgraded to Ecutek engine and transmission software. Much like Cobb, this software uses the stock engine and transmission computers (ECM and TCM), but allows us to hack in and modify data and functionality. We like the fact that Ecutek allows us to monitor data using bluetooth and a cell phone. It is also quite user friendly as far as changing performance maps, launch settings, logging, and viewing logs. We had a local tuner set the car up, and the car functioned much smoother but was still lacking some power. This is when we reached out to a Canadian tuner (Master Tuned) for help. Master Tuned has years of experience tuning the R35 GTR with an in house dyno. Precise results were commanded and monitored. We were able to bump the car up to approximately 610 wheel horsepower, and realize much smoother startup and drivability.
• Forced induction (BOOST) considerations. A stock GTR will produce approximately 12lbs of boost on wide open throttle (WOT). The main goal of all the prior upgrades has been to allow the vehicle to safely produce more boost. Prior to adding additional fueling (fuel pumps and injectors) we found the stock fuel injectors reached an unsafe duty cycle at anything over 16psi of boost. After adding additional fueling we were able to safely produce 20-21psi of boost. We calculated that for each lb of added boost, we added approximately 15hp to the vehicle. How does more boost lead to more power? Horsepower is a product of the correct ratio of air and fuel combusted at just the most efficient time (ignition timing) in a number of cylinders, and turned into power. We create more horsepower by adding more fuel and air to each cylinder per combustion cycle. Higher boost means we can cram more air into the cylinders, bigger injectors allow us to add the needed fuel to compensate. A byproduct of compressing any gas is added heat. As we add more boost, we create more heat and higher IAT. We found that in the AZ summertime, it was common to see IAT reach and exceed 60c. At this temperature, it was necessary to decrease ignition timing to alleviate pre-detonation (knock). Decreased ignition timing (as notated below) led to less power output. We made the decision to upgrade the intercoolers to a larger aftermarket unit. At this point in time, we chose to install an ETS street intercooler. We found this to be sufficient in controlling IAT at all stock turbo power levels, and thus optimizing HP output.
• Ignition timing. The exact point in time that a spark plug fires is very critical to engine performance. Fire it too late and you lose rotational momentum and thus lose power output. Fire it too soon, and the combustion process happens before the piston has reached top dead center which creates an unsafe explosion (knock) that can and will damage your engine. So the goal for for maximum power is to fire the spark plug as early as possible in the compression stroke without creating knock. We found that the stock GTR was running about 13-14 degrees of timing on 91 octane fuel and stock boost levels(although stock ignition timing strategy is vastly different and much more complicated than Ecutek strategy. We were only safely able to add about 1 degree of timing on pump gas. Once we added our ethanol (E70 or higher), we were able to add several more degrees of timing without experiencing knock.
• Tires. As we set this vehicle (or any vehicle) up for more power, it is essential to make sure we have proper rubber to put the added power to the ground. At these FBO levels, we decided to stay with the stock fitment 255/285 Michelin Pilot 4 Season. This tire provided us with reasonable traction and super quiet cruising. We have found that Toyo R888 tires in larger 285/325 fitment is the absolute best setup for traction while maintaining 20″ wheels, but we just were not ready to deal with the road noise that these tires produce.

FBO GTR Performance Results and Additional Data

The goal from the beginning has been to make more horsepower, and in turn run a faster quarter mile. As anticipated, we have also discovered the limits of some mechanical components.

Cobb Accessport results

• The car as we received it came equipped with air intakes, downpipes, and Cobb tuning software. It was still tuned on MAF as well. We decided to take it out to Wildhorse Pass to run the 1/4 mile. We also had the car dynoed. Results as follows:
• 1/4 mile time – 11.493 seconds
• 1/4 mph – 122.13
• 60 ft time – 1.911 seconds
• 667.6hp @ 6835 rpm
• 645.4 ft lbs torque @ 4228 rpm

Ecutek Results

• After running the above setup, we went ahead and installed an SD sensor for speed density tuning , and loaded Ecutek software. We were not able to get back on the dyno at this power level (we do not have a dyno in house). We were however, able to make it back out to the track.
• 1/4 mile time – 10.640 seconds
• 1/4 mph – 131.02
• 60 ft time – 1.66 seconds

Analysis

We were able to gain a better 60 ft time by running Ecutek. We found this due to the advanced traction control strategy over Cobb. We are able to configure torque output settings in first and second gear in order to maintain traction on launch. Cobb launch resulted in excessive wheel spin, which results in a slower 60 ft time. The easiest way to run a faster 1/4 mile is to decrease your 60ft time. So much so we’ve found, that saving .1 second on your 60ft results in .2 second faster 1/4 mile time(assuming the same horsepower levels). As we ran the car on Ecutek we were also able to run data logs. One interesting data point is boost levels. It became very apparent the stock turbos cannot flow enough air at higher RPM levels to maintain 20psi of boost. Boost levels consistently dropped to 17-18psi by redline in each gear. This told us it was time for bigger turbos.

Beyond FBO – Stock block and upgraded turbos

One limitation we do not want to find is the strength of the stock connecting rods. Connecting rod failure will result in catastrophic engine failure, block damage, and potential front differential and power steering gear damage. We’ve done much research in collaboration with Master Tuned in Canada. The maximum safe and reliable power level for a stock engine block is 650 ft lbs of torque. Horsepower will vary a bit, but is generally pretty safe from 775hp-850hp. Torque is the key item that must be managed by limiting boost levels and ignition timing in the mid rpm range (3800-4400rpm). The VR38 engine produces its maximum torque in the mid range, so once past that we can allow more boost and timing.

Turbo modification list

• Master tuned modified stock turbos(MT1000). Stock exhaust manifolds are machined to accept a larger turbo cartridge. Triple ball bearing turbo cartridge with billet compressor wheel and Inconel turbine wheel. Both wheels are approximately 20% larger than stock. This setup will provide more than enough power to maximize performance of the stock block through the entire rpm range.
• Bigger fuel pumps. The DW stock replacement pumps were found to only flow approximately 400 liters per hour at 55psi base pressure, which is less than the manufacturer specified. This is likely due to the higher fuel pressure required under boost. We set the base fuel pressure (engine idling) at 55psi. However, as the car is under boost the fuel pressure must increase so the fuel injectors can emit the same amount of fuel as the intake manifold is essentially pushing back on them. We ran out of fuel pump with the DW setup, this left the fuel injectors starving for fuel at higher boost levels. We made the decision to install a Visconti fuel pump basket fitting with two Walbro 450lph fuel pumps. We ran the car a week or two at this level when it suddenly stopped running. We found the culprit to be overheated and burned stock fuel pump wiring. At this point we opted to install a Visconti hard wire kit which replaced the stock fuel pump wiring with a higher gauge setup that will not overheat. The car can now supply sufficient fuel for our 800+ horsepower goal. It should be notated however, that over the next year we realized several inadequacies with this Visconti basket and Walbro pumps. Anytime we would drive the vehicle over an hour (while running ethanol content of 70% or higher) when the ambient temperature was above 105 degrees Fahrenheit, one or both pumps would fail. We decided to start monitoring fuel temperatures and came to a shocking conclusion – The ethanol in the fuel tank was getting so hot, that it would eventually start boiling in the fuel tank. This causes the fuel pumps to cavitate and fail. We experienced this failure no fewer than 5 times before finally switching to a brushless fuel pump setup (more on this below).
• Fuel injectors – We found the injector dynamics 1300cc injectors to be sufficient for this power level
• MAP sensor. When running approximately 28psi of boost, we found the car would run super rich (dumping way too much fuel). We traced this back to the stop MAP sensor. It appears that the stock sensor will only read approximately 28psi of boost before going out of limit. At this point in time, we opted to install a 4 bar MAP sensor by Omni. This gave us the head room to run more boost without running out of room.
• Upgraded clutch packs. Once we increased engine torque output, we started noticing excessive transmission clutch slip. On the stock turbos, we had never notated a slip greater than 120rpm on a WOT run. With the added engine output, it quickly shot over 200rpm which would put the car into clutch slip protection (CSP) and reduce power output to save the transmission. This was unacceptable, so we reached back out to our friends at Master Tuned Canada for a solution. The stock clutch pack consists of an A basket (responsible for gears 2,4,6) and a B basket (responsible for gears 1,3,5,R) which each contain 6 friction discs. We ended up replacing this with a 14p clutch upgrade which contains 7 discs per basket. This clutch setup was more than enough to hold our required 650ft lb of torque, and we never realized a slip greater than 80 rpm on this setup.

Upgraded turbo results

With the larger turbos installed, with supporting fuel system – We were ready to gather some data to analyze our results. We ran it on a dyno first, and then 1/4 mile

Dyno results

• 785hp @ 6200rpm
• 730 ft lbs of torque @ 5000rpm (limited below 680 in mid range for safety sake)

Track results

• 1/4 mile time 10.465 seconds
• 1/4 mph 137.11
• 60 ft time 1.690 seconds

Analysis

We were able to significantly increase the power output of the VR38 engine by installing larger turbos. The only issue we ran into on the dyno in the 104 degree Tucson heat was that our IAT would climb to unsafe ranges after an extended pull. We confirmed this not to be the case when the car is moving down the road with air flowing over the intercooler. Our 1/4 mile mph shows a solid increase over the stock turbos, though we suspect there is more power available in these turbos if we take away the limitations of the stock engine.

Master Tuned MT1000 turbos on a fully built engine

We wanted to find the maximum capability of the MT1000 turbo without running into engine or transmission restrictions. It should be notated here, that THIS is the point in time our project became VERY expensive. If you are interested in cost/horsepower benefit, we recommend you stay with the above setup and 800 horsepower or less. If you’re like us though, you might feel limits were meant to be found and broken. We are on a quest to an 8 second 1/4 mile after all…

Fully built motor( an engine whos internals have been upgraded to hold substantially more power than stock)

• We opted to purchase a Stage 2 built short block rotating assembly from Lynch Mob Racing. LMR is the expert in VR38 performance, and we only wanted the best.
• New Nissan block
• Used Nissan OEM crank, balanced
• Manley 300M connecting rods
• Wiseco LMR spec 10:1 piston set with .220 pins
• ARP main stud hardware set
• Nissan rod and main bearings

Cylinder heads

• We opted to upgrade our cylinder heads in house
• Ferrea stainless valves
• GSC Stage 3 camshafts with conical springs
• ARP L19 cylinder head studs
• OEM Nissan head gaskets (we regret not installing T1 spec cometic head gaskets, though we have not had a failure to this date)
• Dodson front oil passage gasket kit
• ATI crank damper pulley (the stock damper is prone to failure over 8,500RPM)

Fueling upgrades

• As notated earlier, we were frustrated with the Visconti fuel basket and associated Walbro fuel pumps. At this point in time we opted to install a Radium Engineering fuel pump hanger which also includes a built in surge tank to avoid fuel starvation. With this hanger and in this current configuration, we installed a Ti Automotive BKS1000 brushless fuel pump as the primary fuel pump. The brushless pump requires an auxiliary controller that we mounted in the trunk. This pump amazingly pumps more fuel and creates LESS heat than the Walbro setup did. We realized fuel temps to run a full 10degrees F cooler than before. As the secondary pump, we installed an AEM 340LPH brushed pump. The secondary pump only runs when the engine is under boost, so its impact on fuel temps is minimal. You’ll see that we replace this AEM pump at a later point in time though.
• Fuel lines. We opted to install the Radium Engineering fuel line set to allow more fuel to flow to and from the engine. Stock lines have been known to restrict flow past 1100hp
• Fuel rails. We opted to install the matching Radium Engineering fuel rails to eliminate the flow restriction of the stock rails as well. Please notate, that we very quickly removed these Radium rails, as they made the fuel injectors sound terribly loud for some reason.
• Fuel pressure regulator. The stock fuel pressure regulator is mounted on the return side of the stock fuel rails and is not adjustable. With the new fuel pumps, lines, and rails, we need to be able to monitor and adjust our fuel pressure. The adjustable regulator allows just that.
• Fuel pressure sensor. With higher power comes higher likelihood of failing fuel components. We thought it prudent to install a fuel pressure sensor which would monitor fuel pressure, and also increase injector duty if pressure ever dropped below the standard threshold. The pressure sensor also allowed us to setup a safety limit to shut the engine down in the case of a loss of fuel pressure.
• Fuel injectors. We opted to install larger ID1700X injectors for this setup, to be certain we would not run out of fuel. We had noticed the prior 1300cc injectors were running upwards of 80% duty cycle and simply would not support added power.

Auxiliary hardware

• 21psi blow off valve springs. This will ensure blow off valves do not hang open under cruising and boost building.
• 21psi wastegate springs. This will apply extra pressure to keep wastegates closed as long as possible without being pushed open by exhaust backpressure.
• Boost Logic Boost Control solenoid (MAC Valve). We opted to replace the unreliable Nissan solenoid with an upgraded unit. The Nissan solenoid was located next to the LH turbo charger, and nearly impossible to access with the engine installed. We mounted the new Boost Logic unit right on top of the engine for less heat and better accessibility.
• DBA inlets. Our CBA car came with smaller turbo inlets that we found to be restrictive over 800hp. The newer DBA version is approximately 1/2″ larger diameter and also matched up perfectly to the inlets on the MT1000 turbos
• AMS race intercooler. We had found in our previous setup running approximately 800hp in moderate AZ weather, that the smaller ETS street version intercooler was not sufficiently cooling intake air temperatures. In 89 degree ambient weather we saw the IAT climb to 159 degrees on our previous dyno pulls. After 140 degrees, the factory ECU will begin to pull timing to avoid pre detonation (which can be quite detrimental to the engine internals). Less timing resulted in a power limitation, so we knew that we needed to upgrade. The AMS race intercooler offered almost DOUBLE the charge air cooling capacity over our previous ETS unit.
• Koyo aluminum radiator. When we removed the engine we noticed that the stock radiator had sprung a leak. This was the perfect time to upgrade. The all aluminum Koyo radiator offers 20% to 30% more cooling capacity over the stock plastic/aluminum radiator. Added horsepower equals added heat, so this was an essential upgrade to keep the engine safe and reliable in the AZ heat.

Transmission Upgrade

We have found in our research, that stock transmission internals are prone to failure at and beyond these power levels. That being said, we decided to further upgrade the transmission in the following manner to support 1,000+ horsepower

• Dodson HD gearset (1-6 gears)
• Dodson Sportsman 18 plate clutch (9 plates per baskets A&B)
• Dodson mechanical circlips

Dyno Results

Front differential upgrade

We had the engine out of the car, so now was the best time to inspect our front differential. Upon disassembly we found evidence that the ring and pinion had been coming out of alignment. It appeared that the cast aluminum front differential housing was flexing under extreme stress. We did some research to find that Precision Performance & Coatings in Utah offered a billet front differential housing. We swapped all differential internals into this housing.