zumbooruk
Senior Member
- Joined
- Oct 19, 2024
- Threads
- 9
- Messages
- 580
- Reaction score
- 503
- Location
- Ventura CA
- Vehicle(s)
- 2025 FL5, 2014 Chevy Suburban (wife), previous 2007 FA5
- Thread starter
- #1
Any opinions?
I am not looking for power, just smoothness and responsiveness.
https://www.jsracing.co.jp/spl/trev/us/
The J's Racing T-REV System is a one-way reed valve that installs in the crankcase breather line. It creates controlled negative pressure inside the crankcase by blocking air backflow while allowing blow-by gas to exit.
J's Racing claims reduced piston and crankshaft drag, sharper throttle response, smoother acceleration feel, lighter shift quality on the FL5 version, and modest fuel-economy/CO2 benefits. The principle is drawn from racing practice where crankcase vacuum lowers pumping losses.
Real-world results show measurable vacuum and consistent subjective reports of improved response and smoother engine braking or shift feel. Power gains on a dyno are negligible because the part is a refinement device rather than a power adder.
AI blurb (don't trust and verify):
Product Overview and Function
T-REV stands for Teramoto Racing Eco Valve. It was developed by Teramoto and offered through J’s Racing with Honda-specific calibrations of the reed valve and internal geometry. The unit sits in the breather hose between the engine and the intake or PCV circuit and works alongside the stock PCV valve.Jsracing
During the power stroke a small amount of combustion gas leaks past the piston rings into the crankcase. This creates positive pressure that the stock breather system only partially relieves. When the piston rises or the throttle closes, air can flow back, leaving residual pressure that adds drag. The T-REV’s multi-surface reed valve and internal spiral passages allow outward flow while blocking reverse flow, so the crankcase settles into a mild vacuum. Lower air density inside the case reduces the work the pistons and crankshaft must do against the air mass.
The FL5-specific T-REV BP version adds a bypass circuit. J’s Racing states this allows more effective low-rpm decompression tailored to the K20C and produces a clearer change in shift quality.Torque-performance-developments.myshopify
Manufacturer Claims versus Observed Results
Throttle response: Superior / improved
Observed: Consistently reported as noticeable but not dramatic
Acceleration feel: "Better, smoother, freer-revving"
Observed: Subjective improvement in mid-range “blow-up” and reduced harshness
Shift quality (FL5 BP): Dramatically lighter and smoother up and down shifts
Observed: limited independent FL5 owner data yet
Power / fuel economy: "Same power with less throttle input, lower CO2"
Observed: No meaningful dyno horsepower increase; minor economy gains possible through reduced throttle use
Engine braking: Smoother / milder
Observed: Frequently noted as reduced shock on throttle lift or downshift
Vacuum achieved: Optimizes to negative pressure
Observed: "Measured values typically -8 to -11 kPa street, higher in some tests"
Independent pressure measurements on various engines (motorcycles and cars) confirm the valve does generate the claimed vacuum. User reports from Honda Fit, S2000, K-series, and other applications describe a smoother, more responsive character rather than a large performance jump. One early installer summarized the change as “not a night and day difference, but it’s noticeable.” Motorcycle users and some Japanese reviews tend to report stronger subjective gains, consistent with engines that benefit more from reduced windage.Facebook
No independent chassis-dyno comparisons show large horsepower increases. This is expected. The benefit is reduced internal friction and pumping loss rather than added airflow or boost. On a well-sealed modern turbo engine the absolute gain is modest. The part’s value is therefore in drivability refinement.
Installation, Cost, and Maintenance
Installation is relatively straightforward on a stock engine: the valve is inserted into the model-specific breather hose with the supplied fittings. Aftermarket intake or catch-can plumbing may require re-routing. J’s Racing warns that incorrect installation can lead to oil leaks or engine damage and recommends professional fitting for the FL5 unit.Torque-performance-developments.myshopify
Current street price for the FL5 TRBP-L5 is approximately 95,000 JPY (roughly $550–650 USD depending on retailer and exchange rates). The part is usually made to order with a multi-week lead time.Nengun
Maintenance is required. The reed-valve shim wears. Annual inspection or cleaning at 10,000 km and a full overhaul every two years or 20,000 km are recommended. Neglect can reduce effectiveness or allow contamination.
Practical Considerations for an FL5
The system does not alter boost, fueling, or emissions hardware in a way that typically affects CARB compliance for a California street car, but local inspection rules should be verified. It pairs logically with existing functional modifications (intake, tune, motor mounts) by refining response rather than adding stress. Extreme vacuum levels can theoretically affect oil seals or aeration, yet the calibrated street settings used by Teramoto and J’s Racing are kept well within safe limits (street targets are usually around -10 kPa).
In summary, the T-REV delivers on its core mechanical claim of generating crankcase vacuum and produces a real but subtle improvement in throttle response and smoothness for most users. It is not a high-impact power part. Owners seeking measurable horsepower or major track gains will find larger returns elsewhere. Owners focused on drivability polish and longevity-oriented refinement may find the change worthwhile if the cost and maintenance are acceptable.
Survey of Crankcase Pressure Control and the T-REV System
Crankcase pressure management has long been recognized in high-performance engine development as a means of reducing parasitic losses. In a conventional four-stroke engine, blow-by gas that passes the piston rings elevates pressure in the crankcase. The rising and falling pistons then displace this air mass, creating both pumping work and aerodynamic drag (windage) on the rotating assembly. Racing engines, particularly those in motorcycle Grand Prix and certain four-wheel categories, have for decades employed active or passive methods to maintain a controlled vacuum in the crankcase. Lower air density reduces the energy required to accelerate the internal air volume and allows the pistons and crankshaft to move with less resistance. The result is freer engine response, reduced mechanical drag, and in some cases a measurable improvement in efficiency.
The T-REV system adapts this principle for production vehicles through a passive one-way valve. Developed by Teramoto Racing and calibrated by J’s Racing for specific Honda applications, the device is inserted into the existing breather path. Its internal geometry incorporates fluid-dynamic features intended to accelerate outward flow: spiral surface detailing and a multi-faceted reed valve that disperses pressure loading across three surfaces. These details are claimed to improve sealing reliability and flow characteristics relative to a simple check valve. Because the valve is model-specific, the reed thickness and spring rate are selected to match the blow-by characteristics and desired vacuum level of the target engine. Street calibrations typically target moderate vacuum in the region of -10 kPa, a level that laboratory and on-vehicle measurements have shown is achievable while remaining compatible with oil seals and lubrication systems.
Empirical pressure data collected by the manufacturer and independent experimenters confirm that the valve functions as designed. On various test engines, crankcase pressure that previously hovered near atmospheric or slightly positive drops into consistent negative territory once the T-REV is fitted. Values of -8 to -11 kPa under load are commonly recorded, with higher vacuum possible under certain operating conditions or with more aggressive calibrations. These measurements establish that the core physical claim is valid.
The translation of that vacuum into driver-perceived performance is more nuanced. Reduced internal drag manifests primarily as improved throttle response and a smoother transition between load and overrun. Many users describe a freer-revving character, reduced “jerky” behavior on throttle lift, and a milder engine-braking sensation. On the FL5-specific T-REV BP variant the manufacturer further claims an improvement in shift quality, attributing the change to more stable crankcase pressure during the load transfer that accompanies gear changes. Independent long-term owner reports specific to the FL5 remain limited because the BP version is relatively recent, yet the pattern of feedback across earlier Honda applications (Fit, S2000, earlier Civic Type R models) is consistent with the manufacturer’s qualitative description.
Quantifiable power increases on a chassis dynamometer are small to nonexistent under steady-state conditions. This outcome is expected. The system does not increase mass airflow, boost pressure, or combustion efficiency in a primary sense. Any power benefit is second-order and arises only from the reduction of internal friction. Consequently, claims of “the same power with less throttle” or reduced CO2 are plausible in principle through lower average throttle opening for a given road speed, yet they are difficult to isolate from other variables in everyday driving. Fuel-economy gains, when reported, are modest.
Practical limitations accompany the benefits. The reed valve is a wear item. Periodic inspection and eventual overhaul are necessary to maintain the intended vacuum level. Installation on a heavily modified engine may require custom plumbing. Excessive vacuum beyond the design range can, in theory, draw oil past seals or promote aeration, although the calibrated street units are intended to avoid this regime. Cost is also a consideration. At roughly $550–650 for the FL5 unit the price is high relative to the magnitude of the subjective improvement, placing the part in the category of refinement rather than essential performance hardware.
From an engineering standpoint the T-REV occupies a legitimate niche. It is neither a placebo nor a transformative power modification. It is a carefully calibrated passive vacuum valve that demonstrably lowers crankcase pressure and produces corresponding refinements in engine response and drivability. For an owner whose priority is longevity, smoothness, and precise throttle connection—particularly on a high-strung turbocharged engine such as the K20C in the FL5 Civic Type R—the system can deliver a measurable improvement in the quality of the driving experience. For an owner seeking large gains in peak power or lap time, other modifications will return greater value. The decision therefore rests on the relative weighting of refinement versus outright performance within the overall build philosophy.
Key Citations
I am not looking for power, just smoothness and responsiveness.
https://www.jsracing.co.jp/spl/trev/us/
The J's Racing T-REV System is a one-way reed valve that installs in the crankcase breather line. It creates controlled negative pressure inside the crankcase by blocking air backflow while allowing blow-by gas to exit.
J's Racing claims reduced piston and crankshaft drag, sharper throttle response, smoother acceleration feel, lighter shift quality on the FL5 version, and modest fuel-economy/CO2 benefits. The principle is drawn from racing practice where crankcase vacuum lowers pumping losses.
Real-world results show measurable vacuum and consistent subjective reports of improved response and smoother engine braking or shift feel. Power gains on a dyno are negligible because the part is a refinement device rather than a power adder.
AI blurb (don't trust and verify):
Product Overview and Function
T-REV stands for Teramoto Racing Eco Valve. It was developed by Teramoto and offered through J’s Racing with Honda-specific calibrations of the reed valve and internal geometry. The unit sits in the breather hose between the engine and the intake or PCV circuit and works alongside the stock PCV valve.Jsracing
During the power stroke a small amount of combustion gas leaks past the piston rings into the crankcase. This creates positive pressure that the stock breather system only partially relieves. When the piston rises or the throttle closes, air can flow back, leaving residual pressure that adds drag. The T-REV’s multi-surface reed valve and internal spiral passages allow outward flow while blocking reverse flow, so the crankcase settles into a mild vacuum. Lower air density inside the case reduces the work the pistons and crankshaft must do against the air mass.
The FL5-specific T-REV BP version adds a bypass circuit. J’s Racing states this allows more effective low-rpm decompression tailored to the K20C and produces a clearer change in shift quality.Torque-performance-developments.myshopify
Manufacturer Claims versus Observed Results
Throttle response: Superior / improved
Observed: Consistently reported as noticeable but not dramatic
Acceleration feel: "Better, smoother, freer-revving"
Observed: Subjective improvement in mid-range “blow-up” and reduced harshness
Shift quality (FL5 BP): Dramatically lighter and smoother up and down shifts
Observed: limited independent FL5 owner data yet
Power / fuel economy: "Same power with less throttle input, lower CO2"
Observed: No meaningful dyno horsepower increase; minor economy gains possible through reduced throttle use
Engine braking: Smoother / milder
Observed: Frequently noted as reduced shock on throttle lift or downshift
Vacuum achieved: Optimizes to negative pressure
Observed: "Measured values typically -8 to -11 kPa street, higher in some tests"
Independent pressure measurements on various engines (motorcycles and cars) confirm the valve does generate the claimed vacuum. User reports from Honda Fit, S2000, K-series, and other applications describe a smoother, more responsive character rather than a large performance jump. One early installer summarized the change as “not a night and day difference, but it’s noticeable.” Motorcycle users and some Japanese reviews tend to report stronger subjective gains, consistent with engines that benefit more from reduced windage.Facebook
No independent chassis-dyno comparisons show large horsepower increases. This is expected. The benefit is reduced internal friction and pumping loss rather than added airflow or boost. On a well-sealed modern turbo engine the absolute gain is modest. The part’s value is therefore in drivability refinement.
Installation, Cost, and Maintenance
Installation is relatively straightforward on a stock engine: the valve is inserted into the model-specific breather hose with the supplied fittings. Aftermarket intake or catch-can plumbing may require re-routing. J’s Racing warns that incorrect installation can lead to oil leaks or engine damage and recommends professional fitting for the FL5 unit.Torque-performance-developments.myshopify
Current street price for the FL5 TRBP-L5 is approximately 95,000 JPY (roughly $550–650 USD depending on retailer and exchange rates). The part is usually made to order with a multi-week lead time.Nengun
Maintenance is required. The reed-valve shim wears. Annual inspection or cleaning at 10,000 km and a full overhaul every two years or 20,000 km are recommended. Neglect can reduce effectiveness or allow contamination.
Practical Considerations for an FL5
The system does not alter boost, fueling, or emissions hardware in a way that typically affects CARB compliance for a California street car, but local inspection rules should be verified. It pairs logically with existing functional modifications (intake, tune, motor mounts) by refining response rather than adding stress. Extreme vacuum levels can theoretically affect oil seals or aeration, yet the calibrated street settings used by Teramoto and J’s Racing are kept well within safe limits (street targets are usually around -10 kPa).
In summary, the T-REV delivers on its core mechanical claim of generating crankcase vacuum and produces a real but subtle improvement in throttle response and smoothness for most users. It is not a high-impact power part. Owners seeking measurable horsepower or major track gains will find larger returns elsewhere. Owners focused on drivability polish and longevity-oriented refinement may find the change worthwhile if the cost and maintenance are acceptable.
Survey of Crankcase Pressure Control and the T-REV System
Crankcase pressure management has long been recognized in high-performance engine development as a means of reducing parasitic losses. In a conventional four-stroke engine, blow-by gas that passes the piston rings elevates pressure in the crankcase. The rising and falling pistons then displace this air mass, creating both pumping work and aerodynamic drag (windage) on the rotating assembly. Racing engines, particularly those in motorcycle Grand Prix and certain four-wheel categories, have for decades employed active or passive methods to maintain a controlled vacuum in the crankcase. Lower air density reduces the energy required to accelerate the internal air volume and allows the pistons and crankshaft to move with less resistance. The result is freer engine response, reduced mechanical drag, and in some cases a measurable improvement in efficiency.
The T-REV system adapts this principle for production vehicles through a passive one-way valve. Developed by Teramoto Racing and calibrated by J’s Racing for specific Honda applications, the device is inserted into the existing breather path. Its internal geometry incorporates fluid-dynamic features intended to accelerate outward flow: spiral surface detailing and a multi-faceted reed valve that disperses pressure loading across three surfaces. These details are claimed to improve sealing reliability and flow characteristics relative to a simple check valve. Because the valve is model-specific, the reed thickness and spring rate are selected to match the blow-by characteristics and desired vacuum level of the target engine. Street calibrations typically target moderate vacuum in the region of -10 kPa, a level that laboratory and on-vehicle measurements have shown is achievable while remaining compatible with oil seals and lubrication systems.
Empirical pressure data collected by the manufacturer and independent experimenters confirm that the valve functions as designed. On various test engines, crankcase pressure that previously hovered near atmospheric or slightly positive drops into consistent negative territory once the T-REV is fitted. Values of -8 to -11 kPa under load are commonly recorded, with higher vacuum possible under certain operating conditions or with more aggressive calibrations. These measurements establish that the core physical claim is valid.
The translation of that vacuum into driver-perceived performance is more nuanced. Reduced internal drag manifests primarily as improved throttle response and a smoother transition between load and overrun. Many users describe a freer-revving character, reduced “jerky” behavior on throttle lift, and a milder engine-braking sensation. On the FL5-specific T-REV BP variant the manufacturer further claims an improvement in shift quality, attributing the change to more stable crankcase pressure during the load transfer that accompanies gear changes. Independent long-term owner reports specific to the FL5 remain limited because the BP version is relatively recent, yet the pattern of feedback across earlier Honda applications (Fit, S2000, earlier Civic Type R models) is consistent with the manufacturer’s qualitative description.
Quantifiable power increases on a chassis dynamometer are small to nonexistent under steady-state conditions. This outcome is expected. The system does not increase mass airflow, boost pressure, or combustion efficiency in a primary sense. Any power benefit is second-order and arises only from the reduction of internal friction. Consequently, claims of “the same power with less throttle” or reduced CO2 are plausible in principle through lower average throttle opening for a given road speed, yet they are difficult to isolate from other variables in everyday driving. Fuel-economy gains, when reported, are modest.
Practical limitations accompany the benefits. The reed valve is a wear item. Periodic inspection and eventual overhaul are necessary to maintain the intended vacuum level. Installation on a heavily modified engine may require custom plumbing. Excessive vacuum beyond the design range can, in theory, draw oil past seals or promote aeration, although the calibrated street units are intended to avoid this regime. Cost is also a consideration. At roughly $550–650 for the FL5 unit the price is high relative to the magnitude of the subjective improvement, placing the part in the category of refinement rather than essential performance hardware.
From an engineering standpoint the T-REV occupies a legitimate niche. It is neither a placebo nor a transformative power modification. It is a carefully calibrated passive vacuum valve that demonstrably lowers crankcase pressure and produces corresponding refinements in engine response and drivability. For an owner whose priority is longevity, smoothness, and precise throttle connection—particularly on a high-strung turbocharged engine such as the K20C in the FL5 Civic Type R—the system can deliver a measurable improvement in the quality of the driving experience. For an owner seeking large gains in peak power or lap time, other modifications will return greater value. The decision therefore rests on the relative weighting of refinement versus outright performance within the overall build philosophy.
Key Citations
- J’s Racing official T-REV System page: https://www.jsracing.co.jp/spl/trev/us/
- Nengun Performance product listing (FL5 TRBP-L5 pricing and details): https://www.nengun.com/js-racing/t-rev-system
- Torque Performance Developments FL5 T-REV BP product page: https://torque-performance-developments.myshopify.com/products/js-racing-fl5-t-rev-bp
- Black Hawk Japan FL5 TRBP-L5 listing: https://www.blackhawkjapan.com/products/js-racing-trbp-l5
- FitFreak forum discussion of T-REV function and user experiences: https://www.fitfreak.net/forums/2nd-generation-ge-08-13/107205-what-does-t-rev-system-do.html
- K20a.org thread on J’s Racing T-REV System: https://www.k20a.org/threads/js-rac...anyone-installed-one-of-these-curious.228571/
- Manufacturer pressure measurement examples and technical explanations from Teramoto-related sources and test videos.
Sponsored
