How to Develop a Honda Prelude Racecar - Part 2

Giving our 2022 Spec Car its first race laps

Posted by Roger on May 29, 2022

In the first installment of our new series, we assembled the tools that we needed to develop the StudioVRM Honda Prelude, established a baseline for the car, and set up a development plan for our first race of the season. All that was left was to put that plan to the test at the first round of the USTCC East Series season at Summit Point Raceway.

Getting to The Point

Traveling to Summit Point Motorsports Park's Main course is like visiting an old friend. And not just because several of our old friends live nearby.

It was the first track that yours truly ever spent 4+ hours driving to, back when we were working our way up the track day ladder in the mid-2000's. The circuit's 1/2 mile-long main straight and flowing high-speed corners were the site of some of the best wet weather races we had ever experienced. Turn 10 also happened to be the site of our first ever catastrophic engine failure*. It was the perfect place for the car's first true test of the season.

Putting the Plan to the Test

Because we had so many items to check, we opted to spend a few extra dollars and enter the pre-race test day on Friday. The five extra practice sessions would be a nice stress-free way of testing the car.

The first order of business was to re-learn the track and prepare for the litany of items that we had on our initial plan. Yours truly prepared the car early, arrived at grid early, and sat patiently at the back half of the grid so we could be the last car on track. Having 15+ years of on-track experience doesn't make up for the fact that we hadn't driven this car on this track for several years. Humility and patience would be key to a successful first test.

And so it proved, as we took our first tentative laps at a snail's pace, lapping 5 to 6 seconds a lap off our regular pace while cautiously feeling out the powertrain, suspension, and driver. The good news was that, despite being repaved twice since our last visit, the course was as familiar to us as ever. The bad news was that the car exhibited an unsettling tendency to suddenly kick its tail out through the faster right-hand turns on the track. Not a good thing on a track that is predominantly composed of fast right-hand turns.

We approached the problem systematically:

  • First, we checked the hot tyre pressures on the car to see both rear tyres showed the same pressures

  • Next, we checked the rear suspension for any loose bolts or components

  • Then, we looked at any broken components that could cause the alignment to shift

  • Fourth, we checked for any binding in the rear suspension or any indication that the rear dampers were damaged or leaking

  • Finally, we broke out the alignment kit and did a very quick check to make sure that the rear toe and camber hadn't shifted from its pre-season settings

This thorough check revealed no problems. So we recorded the results on our trusty Trello board and went back out for the second session of the day. Again, the snap oversteer reared its ugly head through every right-hand turn. Knowing that we had plenty of time left, we chose to retrace our steps and go through the same five steps again.

This time, our slow, methodical approach proved its worth. Our race engineer noticed that the right rear tyre pressure was still reading the same as it was after our first on-track session - An anomaly considering that the three other tyres were reading 2 psi hotter than before. A few attempts to add air to the right rear revealed the problem: The valve core on the right rear tyre was partially jammed. It was reading 25 psi regardless of how much air was actually in the tyre.

A quick trip to the local Walmart later, we were back at the track with a fresh valve core and a valve core replacement tool. Replacing the jammed core revealed that we had less than 17 psi on the right rear tyre. No wonder the car's handling was so squirrelly.

With that unexpected problem sorted out, we got back to our scheduled program and kept working through our development plan.

 

Mid-Weekend Findings

Our first test day was a productive one. By the end of Friday, we had recorded some productive results against our original plan:

Powertrain

  • Verify that the engine is fully broken in
    • Day 1 Result: Power output indicates that engine is healthy

  • Verify that the new catch can setup has sufficient capacity to handle the blow-by from our engine
    • Day 1 Result: Verified that the catch can setup has enough capacity to last 10 laps at 7250 rpm. Will need additional testing to see if it can last longer

  • If the engine is healthy, consider raising the rev limiter to 7700 rpm
    • Day 1 Result: Defer decision until after day 1 of racing

Suspension & Handling

  • Test the compliance of the suspension by riding the taller kerbs at Summit Point
    • Day 1 Result: Car has no issues absorbing any of the kerbs except for the gator cut kerbs on the outside of Turn 1

  • Check whether the suspension is stiff enough to keep the aero working under hard braking and full acceleration
    • Day 1 Result: Front and rear aero working well enough to change feel of car. Splitter does not contact ground under full braking on flat ground. 

Braking

  • No changes

Tyre and Wheel

  • Monitor treadwear, switch to backup dry set (white wheels) if tyres show damage
    • Day 1 Results: Treadwear on hard compound slicks is significantly less than expected. Replaced right rear valve core due to sticky valve. Tyres seem to work best with a cold pressure of ~22 psi and a hot pressure just around 30 psi.

Aero

  • Monitor effectiveness of gurney flap installed on hood
    • Day 1 Results: Needs testing. Continue monitoring. 

  • Monitor splitter height and check how often it contacts the ground
    • Day 1 Results: Splitter skids contact the ground under hard braking and cornering into Turns 1, 5, 6, and 9. Consider raising splitter by 1 inch to avoid being a nuisance to corner workers.

  • Monitor side skirt height to see how far it is off the ground under cornering
    • Day 1 Results: Confirmed that side skirts were not contacting the track. Need photographs to see how far it is off ground.

Driver

  • Gain a better understanding of Summit Point Raceway
    • Day 1 Results: Check.

  • Avoid unnecessary risks
    • Day 1 Results: So far, so good

 

Turn it up to 10

Friday went well. Time to push the car a little. We found a nice gap in Qualifying, warmed the cold slicks as quickly as we could, and started on a few laps at 9/10ths pace. We weren't really testing anything in the braking system, so we kept our corner entries and braking zones conservative. Aside from that, it was race pace or better for the entire session.

We needed to see if the oil catch cans would be able to hold enough blow-by from a full 15-minute session. And we still weren't sure if the side skirts would contact the ground.

The car's pace was good. The used slicks were thoroughly heat-cycled-out at this point, and the reduced grip meant understeer through every low-speed corner. But otherwise, the car felt good. The front splitter skids were still contacting the ground when the front suspension was loaded up, slowly grinding down the stainless steel skids bolted into the underside of the splitter. And there was an occasional puff of smoke, indicating that the engine was sucking in a little bit of oil from the PCV. Something to note.

The one thing we couldn't tell was how close the side skirts were coming to the ground. Ideally, the metal side skirts on our car should be as close to the ground as possible without touching. We knew that they weren't touching the ground, which means that we could extend them closer to the ground for better performance. But how much taller could we make them?

There was no way to tell without looking at the car from the outside under hard cornering. So yours truly came up with an incredibly convoluted solution - Find a photographer on one of the corner stations, get their attention, drive aggressively enough for them to get a good photo, buy a high-res photo from them afterwards, and use Photoshop to measure the distance between the ground and the bottom of the side skirt.

Corner workers and spectators looked on with furrowed brows as the driver of the #22 Honda Prelude started waving to the photographers under hard cornering in the middle of a qualifying session. This bizarre strategy worked. A few days after the race, we had this photo loaded up into Photoshop, where the ruler tool told us that we could extend the side skirts by another 4 inches before it would hit the ground. Brilliant.

Less brilliant was what happened during the following heat race. The zip ties holding down the oil dipstick were apparently not tight enough. The crankcase pressure had popped the engine oil dipstick up and sprayed Penn Grade 1 5w30 all over the engine bay. There was so much oil that some of it dripped onto the left rear tyre and pitched the car into a wild slide during the second lap of the race.

It was pretty clear what was happening. The crankcase pressure from our high-compression engine was so much that the stock crankcase ventilation system on our car could not relieve the pressure quickly enough. The excess pressure found the one weak seal in Honda's oiling system (the oil dipstick itself) and pushed it out.

Based on some friendly advice from Savage Garage Racing's Coyote Black, we took a trip to the local Home Depot and fabricobbled a homemade vented oil cap. But the 1/2" rubber hose that we used was not built for venting hot vapors from an internal combustion engine. It softened under the heat of the engine and pinched shut after a few laps. The resulting crankcase pressure pushed engine oil out through the stock PCV vents, filling both catch cans and allowing the Honda's H23A powerplant to ingest engine oil. The result? A smokescreen so prominent that it would have made James Bond proud.

Unfortunately, huge clouds of oily smoke are far better suited to action films than the racetrack. We pulled off and retired the car before we could cause any damage to our engine or any of our competitors' cars.

Final Findings from Round 1

By the end of the weekend, the scorecard looked dramatically different from a few days ago:

Powertrain

  • Verify that the engine is fully broken in
    • Result: Power output indicates that engine is healthy. However, crankcase pressure indicates that we may be losing compression on one or more cylinders

  • Verify that the new catch can setup has sufficient capacity to handle the blow-by from our engine
    • Result: Stock PCV and catch can setup has insufficient capacity to last a full 25 minute session at race speeds. A higher capacity catch can and better ventilation is needed.

  • If the engine is healthy, consider raising the rev limiter to 7700 rpm
    • Result: Defer decision to Race 2, pending resolution of crankcase ventilation issues.

Suspension & Handling

  • Test the compliance of the suspension by riding the taller kerbs at Summit Point
    • Result: Car has no issues absorbing any of the kerbs except for the gator cut kerbs on the outside of Turn 1. Retain setup for Round 2.

  • Check whether the suspension is stiff enough to keep the aero working under hard braking and full acceleration
    • Result: Front and rear aero working well enough to change feel of car. Splitter does not contact ground under full braking on flat ground. 

Braking

  • No changes

Tyre and Wheel

  • Monitor treadwear, switch to backup dry set (white wheels) if tyres show damage
    • Result: Treadwear on hard compound slicks is significantly less than expected. Replaced right rear valve core due to sticky valve. Tyres seem to work best with a cold pressure of ~22 psi and a hot pressure just around 30 psi.

      Tyres have reached end of service life. Replace with new Hankook F200s before Round 2.

Aero

  • Monitor effectiveness of gurney flap installed on hood
    • Result: Oil streaking from Saturday incident indicates better flow attachment and higher velocity of flow from hood vent. Retain setup for Round 2.
       
  • Monitor splitter height and check how often it contacts the ground
    • Result: Splitter skids contact the ground under hard braking and cornering into Turns 1, 5, 6, and 9. Raise splitter by 1 inch to avoid being a nuisance to corner workers.

  • Monitor side skirt height to see how far it is off the ground under cornering
    • Result: Confirmed that side skirts were not contacting the track. Extend splitter by 4 inches to improve effectiveness.

Driver

  • Gain a better understanding of Summit Point Raceway
    • Result: Check.

  • Avoid unnecessary risks
    • Result: Mission accomplished.

 

Fixes and Upgrades

Priority one was to address the excessive blow-by being generated by the Prelude's H23A1 powerplant. A permanent solution might involve disassembling the engine and putting new piston rings in the engine. We completed another leakdown test on the engine to check its health, and were relieved to find that the leakdown numbers had improved to under 6% on cylinders 1 and 4, and under 1% on cylinders 2 and 3. Maybe a full engine rebuild could wait.

Instead, we took the approach suggested by fellow USTCC driver, Coyote Black of Savage Garage Racing. We would completely revamp our engine oil vent system, eliminating the stock PCV system and replacing it with a vented oil cap plumbed to a vented catch can. We would then plumb a drain from the bottom of the catch can into our car's Moroso oil pan, which came from the factory with a port for an oil return line. We covered the stock vent to the air intake with a PCV filter, and used this attractive laser-etched plug from Laurel Highlands Laser to close the stock PCV vent hold on the H23A1 valve cover.

In order to avoid a repeat of incident with the oil dipstick popping out, we procured an English Tune oil dipstick hold down. This spring-loaded handle was a much nicer alternative to the amalgamation of zip ties that kept the engine from pushing out the dipstick under load. 

We also took the opportunity to rework the splitter with shorter supports to keep the splitter blade from scraping across the ground as much as it had at Summit Point. The DiFTech splitter support rods that we used were discontinued, so we opted for these exceptionally overbuilt splitter quick support rods from FS Performance Engineering. These support rods have quick release clips similar to the old DiFTech rods and make it much easier to load the Prelude onto our open deck trailer.

Mid-Season Retest

There really is only one way to verify whether changes like these worked, and that is to run the car hard through a long session on a full-size racetrack. As luck would have it, we were already planning on taking a 3-day trip to VIRginia International Raceway for a relaxing weekend of track days with friends from the Honda Prelude racing community. We could use the extra track time to test out our changes in a low-pressure DE environment and maybe enjoy a beer or two with friends afterwards.

With that, we loaded up the rig and prepared for a long tow down to the quiet town of Alton, Virginia.

Did our crankcase ventilation upgrades and new splitter supports address our woes from our Summit Point race? Find out in Part 3 of How to Develop a Honda Prelude Racecar, out now.

In the meantime, I'll see you at the track.

~R

 

*Special thanks to SSM racer Rob Myles, not only for bringing us back from Summit Point all those years ago, but for going back there to tow the stranded Prelude back to our home just one short week later. I still owe you Rob, and I'm still working on paying it forward.