How to Develop a Honda Prelude Racecar - Part 6

Analyzing and adapting to our new VTEC powerplant

Posted by Roger on June 24, 2023

Side by Side: Our new H22A to our old H23A1 Engine

Despite producing similar peak power figures, our new H22 engine and our previous H23A1 race engine are quite different internally. If we were to compare some of the key specs of the two powerplants side-by-side, here's how they would stack up:

  2023 Spec H22A VTEC Engine 2020 Spec H23A1 non-VTEC Engine
Displacement 2157 cc 2259cc
Max Power

194hp at 7800 rpm
(on Shue Tuning's SuperFlow dyno)

194 hp at 6500 rpm
(on Evans Performance Academy's Dynapack)

Rev limiter 7900 rpm 7300 rpm
Compression 10.6:1 12.0:1
Bore x Stroke 87mm x 90.7mm 87mm x 95mm
Cams OEM Crower Race Stage 2 Race Cam
Cam Gears OEM AEM Tru-Time
Valves OEM Supertech
Valve Springs & Retainers OEM Crower
Head Ports de-burred, casting flashes removed. OEM port shape Race Ported head and port matching
Fuel rail OEM Rosko Racing
Fuel injectors Injector Nation E14 600cc Acura RDX 410cc
Piston OEM Nippon Racing H22 pistons
Rod OEM OEM with high strength rod bolts
Oil Pan Baffled OEM w/ Ishihara-Johnson Crank Scraper Moroso Steel H-Series Race Pan
Oil Accumulator Accusump 2 qt Accusump 2 qt
Balance shafts Balance Shaft belt removed KSTuned Balance Shaft Delete
Intake AEM AEM
Intake Manifold CMP Racing Ported Intake Manifold Bad Guys Ported Intake Manifold with IM spacer
Exhaust Header PLM H22 Tri-Y Header Hytech H23A1 4-2-1 Race Header
Exhaust 3" ID exhaust built by the Powertrain Wizard 2.5" to 3" step up exhaust built by the Powertrain Wizard
ECU Hondata S300 Hondata S300
Ignition Burton Racing / HondaRulez Coil on Plug with Honda K20 coil packs OEM Distributor and wires
Harmonic Balancer Ati Super Damper OEM Honda

There are also some notable differences between the externally similar transmissions on the two engines:

  2023 Spec M2F4 Transmission 2020 Spec M2S4 Transmission
Gear Ratios

1st - 3.307
2nd - 1.95
3rd - 1.36
4th: 1.071
5th - 0.871

1st - 3.307
2nd - 1.857
3rd - 1.32
4th: 1.034
5th - 0.812

Final Drive 4.64:1 4.64:1
Synchronizers Honda Synchrotech Carbon Lined
Differential WaveTrac WaveTrac


More than VTEC vs non-VTEC

As you might expect, these small differences added up to something much more substantial in the car. And we felt this in a big way through the first two rounds of the 2023 USTCC East Series Season.

In terms of pure seat-of-the-pants feel, the new H22A and its matching M2F4 transmission felt significantly more powerful in the upper reaches of the powerband. Above 6000 rpm, our new H22 VTEC engine would scream to redline, making full power right up to the fuel cut at 7900 rpm. Even on stock cams and a stock head with lightly deburred ports, our new motor was more eager to rev than our H23A1 ever was. The higher rev limit also let us hold gears for longer through corners like Turn 10 at Summit Point, where our car always felt like it should be between 4th and 5th gear. And of course, that top end power would be accompanied by the dry high-end roar that Honda enthusiasts know and love.

At the same time, the new engine felt like it packed less mid-range punch compared to our old H23A1. We could no longer hang the car out at the bottom of 4th gear through medium speed corners and expect the engine's torque to pull us out at corner exit. In general, the power delivery of the H22 felt more peaky, more akin to a VTEC B-series engine than the torquey H23A1 that we had become so accustomed to.

In order to extract the maximum from this new engine, we would need to be more precise with gear selection when going through medium-speed corners or when dogfighting other cars. This also means shifting a few extra times every lap, something that would be an adjustment for sure.


Is the New Engine Faster?

Characteristics and quirks aside, one thing was clear - Our new engine made our car faster.

Even at a conservative race pace, we were on average a second per lap faster on Summit Point's Main course and 4-5 mph faster at the end of the main straight at NJ Motorsports Park's Lightning track. Between the slightly shorter gearing and the ability to continue building peak power at high RPM, our new engine proved that the tradeoff of low-end torque for top-end power was one worth making on the tracks we race at.

Our AIM Solo II estimated that we could have achieved a 1:22.9 during our first race at Summit Point - over 2 seconds faster than we had previously managed on the West Virginian track. Based on the feedback that the car was giving us, we think that we could have beaten that time over a single push lap.

Admittedly, this gap was likely exaggerated by the oiling and leakdown issues that we experienced with our 2020-spec engine in the 2022 season. Still, considering the fact that our new engine is still saddled with stock cams, this boost in performance bodes well for our future.

Driveshaft Disruptions

More power leads to more problems, as they say. And our car proved this to be true in the first two races of the season.

In our case, these problems manifested in the outer CV joints of our previously reliable driveshafts. The outer CV joint of our Insane Shafts-built left front axle failed spectacularly at Summit Point. We replaced this unit with an aftermarket unit that we repacked with Redline CV2 grease, only to have that one fail at NJ Motorsports Park when the CV joint boot popped off due to insufficient venting in the outer boot. This would have been a major disappointment for us, if we hadn't discovered that the outer CV joint of the right front axle had also developed a worrying amount of play. In all likelihood, it was also going to fail in the very near future.

There is no doubt that the higher speeds contributed to the sudden failures of these axles. At the same time, our driver noted that he was hitting kerbs harder and cutting apexes more aggressively to keep the engine revs from dropping out of the powerband. These two changes combined would easily be enough to shatter our already stressed Honda axles.

Fortunately, CMP Racing's Ross Shull had provided us with a brand new set of Raxles-built "VIR-spec" race axles, and Prelude racer turned prototype racecar designer Billy Howell offered several sets of unopened axles for us to use as cores. The Raxles race axles use OEM Honda shafts as cores, rebuild them with a high-temp grease, and use metal vent tubes on the boots to prevent hot air from building up inside the CV joints. These race-proven axles should give us the reliability we need to keep the Prelude's newfound power from breaking our car.

Closing the Gap

Drivability is just as important as reliability. In order to make our new h22 engine an effective dogfighter, we would need to give it some of the bottom end torque that gave our H23A1 its mid-range punch.

Our first steps to addressing this are to install the throttle body, upper intake manifold, and intake manifold spacer that our technical partner Bad Guys Worldwide had previously built for us. The increase in intake manifold plenum volume should change the characteristics of the engine to better suit our needs, while the enormous 74mm Skunk2 throttle body and the precision-machined taper bore adapter will ensure that our engine will get all of the airflow it needs to perform at its best.

In a few short days, Jeff Evans of Evans Performance Academy will adjust our tune to get the most out of our new hardware.

How will these new improvements change the characteristics of our new powertrain? Find out in Part 7 of How to Develop a Honda Prelude Racecar.


Disclosure Section:

The Bad Guys (AKA Bad Guys Worldwide) is a Technical Partner of StudioVRM.Racing. Roger Maeda and StudioVRM are not affiliated with Evans Performance Academy or CMP Racing.

 The H22 powertrain mentioned above was purchased from CMP Racing at an agreed upon fair market value. All other products mentioned above were purchased at full price out of Roger's own pocket.