Photo by Sam Draiss Photography
A whole nine years have passed since we published the first installment of our Building a Honda Prelude Racecar series. And thanks to enthusiasts like you, these old articles still receive hundreds of views every week.
While the advice and recommendations in these early articles are still relevant today, some of the products mentioned are no longer available or have been supplanted by better options. So, I thought it would help to put this quick list of updates and errata together for those of you who may be building a Honda Prelude Racecar in 2024:
Classing
The US race classing landscape has changed dramatically in the past 10 years. Most new club racing classes now rely on power to weight ratio or bracket racing style lap time-based classes for their race groups.
This is a good thing for owners of 4th and 5th gen Preludes, who traditionally had to fit their cars into classes where they couldn't get their cars light enough to meet minimum weight or couldn't reach power targets with the stock H23A1 or H22 engines.
We now recommend choosing a class which allow for cars to be competitive with a minimum weight of 2500 lbs or higher (with driver), and a target power output of 180 hp to 250 hp. Those figures should be attainable for the average club racer.
Suspension
While we at StudioVRM are still fans of Tein's tanky twin-tube suspension dampers, they are becoming harder to find. Ever since Tein's non-rebuildable "Z" dampers became the focus of their aftermarket coilover business, they have made fewer and fewer suspension dampers that are actually suitable for track use.
Because of this reality, we now have to look elsewhere for budget-friendly coilover options. We now recommend looking at the following options when choosing budget-friendly race coilovers for your Prelude racecar:
While slightly more expensive than the budget-friendly dampers on our Prelude, the budget options from these three vendors should perform similarly or better than what we use today.
The silver lining is that the cost of durable, spherical bearing conversions for our Honda control arms have come down dramatically in the past few years. We now recommend skipping the polyurethane bushings kits and going straight to spherical bearings, even on street cars.
We also recommend running higher spring rates than in the past. Part of this is because newer dampers do such a good job of managing low-speed movement in the shock that there are fewer penalties to running stiffer main springs. The other is due to another reason, which is mentioned further below.
Brakes
Thanks to the low cost of track-capable aftermarket calipers and rotors, most racing classes now allow the use of aftermarket brake calipers and rotors. This is great news for those of us with 4th and 5th gen Preludes which, due to the size and weight of their base chassis, will often end up running with a race weight north of 2500 lbs.
Our budget recommendation for Preludes with larger (17" or 18") wheels is the FatFour Customs Acura RL brake kit - a sturdy big brake kit that combines the 4 piston aluminum calipers off of a 2005 Acura RL with redrilled rotors from a Nissan 350Z. While this kit is heavier than most of the Wilwood-based kits out there, we have found it to be a more rigid and fade-resistant setup.
As far as brake pad compounds, we still recommend the Raybestos ST-43, ST-45, and ST-47 compounds for the front and ST-77s for the rear calipers. However, The ST-45 and ST-77 compounds are still on an extraordinarily long (6 to 12 month) backorder due to ongoing supply issues. If you need something on a more urgent basis, we would recommend looking in the Carbotech or G-Loc brakes catalog for a suitable substitute.
As for cooling, we now recommend skipping the traditional metal hose brake ducts and using vents in the bumper to encourage more airflow to the wheel well to help keep the front brakes cool. This is partly because routing large diameter brake hose is so difficult within the Prelude's cluttered wheel wells, and partly because you can cool the brakes, axles, and shocks with much smaller openings in the front bumper.
Engine
Due to a lack of spare parts, we were forced to switch from the affordable Honda H23A1 non-VTEC engine to the more high-strung H22 VTEC platform in 2023. And while having access to a greater variety of off the shelf parts is a welcome change, it is hard to ignore the fact that H-series engine cores are no longer as cheap or as affordable as they used to be.
Yes, Honda K series swaps are a popular and common option for street cars. However, the K swap mounts for the 4th and 5th gen chassis place the transmission in a position which puts the cv joints at an extreme angle. The load on those joints is so extreme that even top shelf racing axles (e.g. Raxles VIR axles) will typically only last a handful of race weekends before breaking. At $800 per set, replacing these axles on a regular basis can get very expensive very quickly.
While we do plan to continue with the H22 platform for the foreseeable future, we now plan to use race-prepared, sleeved blocks from our Technical Partner, Bad Guys Worldwide. The costs to build a sleeved block are still reasonable at the time of writing, and will greatly extend the life of the engines. This is especially important as many H22 engines are now so old that the FRM coated cylinder liners are starting to fail due to old age and wear.
Differential and Transmission
Limited slip differentials and aftermarket Final Drives have become so affordable and cheap that they are now among the first Powertrain modifications that we would make if we were building a new Prelude racecar. This is partly because most used manual transmissions tend to come with a fair bit of synchro and bearing wear, and should be inspected or rebuilt before putting into service in a race car.
Fortunately, companies like MFactory / Synchrotech have made this very affordable for us Prelude owners, with several options available for rebuild kits, final drives, and limited slip differentials.
As for what type of Limited Slip Differential to use, metal plate clutch pack LSDs have a decisive performance advantage over helical gear units, to the tune of about one second per lap on a 1 minute 30 second road course. However, even modern-day clutch pack diffs need to be serviced and rebuilt on a regular basis. For those of us who are not able to rebuild transaxles and differentials on a regular basis, we recommend a WaveTrac. WaveTrac diffs continue to offer an affordable, low-maintenance alternative to more expensive clutch pack differentials, and offer performance somewhere between a helical differential and a clutch pack differential.
Aero
Thanks to the increased flexibility offered by modern rulebooks, downforce-producing aero is both affordable and effective to the point of being almost mandatory.
We recommend cutting your own splitter from 1/2" birch plywood and using quick release mounts and splitter rods from Professional Awesome Racing to mount it. PA's quick release mechanism and compression fit splitter rod design are clever, durable, affordable, and you can buy spare parts for them. The last bit is important as splitters and splitter mounting components tend to suffer a tremendous amount of wear and damage, especially as both car and driver become faster.
As far as rear wings, we recommend looking at large-chord aluminum wings, similar to what is offered by Winglogic. Be warned that the Winglogic wings are not bolt-on aero pieces. You will need some fabrication skills and the ability to weld thin-gauge aluminum, and the ability to source your own uprights. However, as far as budget-friendly wings go, they currently offer the best balance between affordability and outright performance. One of their wing elements, a set of eBay-sourced wing upgrights, and a TIG welder to bring it all together will shave seconds off of your lap times for pennies on the dollar.
Questions?
Have a question about any of the info above? Feel free to reach out to us via our Contact Us form.
Disclosure:
The Bad Guys (AKA Bad Guys Worldwide) is a Technical Partner of StudioVRM.Racing, and have provided discounted engine rebuild services to us for our latest race engine build.
StudioVRM and Roger Maeda are not affiliated with Tein, Redshift Suspension, Shaftworks, Motion Control Suspension, FatFour Customs, Carbotech, G-Loc, Raxles, MFactory / Synchromesh, WaveTrac, Professional Awesome Racing, Winglogic, or any of the other vendors mentioned here. Any of the parts purchased and reviewed for this article have been purchased at full price from our team's car development budget.
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