Engine Setup Strategy for Front4

There are many engine choices available in Front4, and you have the flexibility to choose somewhere between low weight (and lower power) or high power (and higher weight). The current 2018 rules establish the following parameters:

Engine Output = (Engine_WHP + Engine_TQ) / 2
Engine Output cannot exceed 160
Vehicle Minimum Weight (w/ driver) = Engine Output * 17
Vehicle Minimum Weight must be at least 2200 lbs

Based on this, we know that anything below an Engine Output of 129.4 (2200 lbs / 17) is leaving something on the table. We also know that at 160 Engine Output, we’d have to weigh 2720 lbs (160 * 17), which is a whopping 520 lbs more!

Some Real-World Examples (Honda Engines)

Underpowered Baseline: B18B1 I/H/E, 126.8 whp and 116.7 whp (Engine Output: 121.8), 7000 rpm redline, paired with a LS transmission (long gears). Minimum Weight: 2200 lbs

Low Weight / Low Cost: Low-Compression B20B (8.8:1), 128.3 whp and 123.0 ft-lbs (Engine Output: 125.7), 7000 rpm redline, paired with a LS transmission (long gears). Minimum Weight: 2200 lbs

A Little More Power and Weight: High-Compression B20Z (9.6:1) I/H/E, 146.2 whp and 133.4 ft-lbs (Engine Output: 139.8), 7000 rpm redline, paired with a LS transmission (long gears). Minimum Weight: 2376 lbs

Big Power / Big Cost: Integra Type-R B18C5, 170.1 whp and 124.1 ft-lbs (Engine Output: 147.1), 8500 rpm redline, paired with a Type-R transmission (short close-ratio gears). Minimum Weight: 2500 lbs

Notice that the Type-R setup differs in that it’s a high-revving VTEC engine with far more horsepower than torque, and it’s also paired with a much more optimal track transmission than the others, so we’ve given it a bit of an advantage there. These extremes were chosen to better illustrate its different characteristics, and also how our weight rules affect it in both straight-line and cornering performance.

Straight-Line Acceleration

With the B20B example being a little below the ideal Engine Output of 129.4 for 2200 lbs, it’s leaving something on the table, and surely we’d expect the Type-R to beat it down the straight anyway. We can calculate wheel torque from the dyno plot and effective gear ratios, which clearly shows that the Type-R is indeed putting the most to the wheels at almost all speeds:

But what if we factor in the vehicle mass, being that we make the B20Z carry 176 lbs more and the Type-R carry 300 lbs more? Things get quite a bit closer, especially for the B20’s, but the high-revving short-geared Type-R is still pretty strong:

Then we factor in aerodynamics and the stronger engines show a slight edge at higher speeds:

Keep in mind that having more acceleration early is much more valuable than having it late, and we can see that the B20’s will have more initial acceleration out of many corners, but still the Type-R is the clear straight-line winner here.

Cornering & Braking

It’s now clear that the Type-R setup is going to be faster down the straights, and that can lead to complaints such as, “He motored me down the straight, I had no chance!”, “How is this fair!?!?”, etc. We’re quick to forget that we’re really here for the turns, and the Type-R B18C5 will have to brake and turn with an extra 300 lbs, per our minimum weight rules.

Using an arbitrary amount of force for tire holding grip, and the vehicle’s mass, we can calculate the maximum potential G-force for that grip level:
B18B 7k RPM (2200 lbs): 1.23 G
B20B 7k RPM (2200 lbs): 1.23 G
B20Z 7k RPM (2376 lbs): 1.13 G
B18C5 8.5k RPM (2500 lbs): 1.08 G
(actual G-forces will vary; these are just examples to show deltas based on vehicle weight)

So, with our weight rules, the Type-R will be faster on the straights, but his extra 300 lbs means he could have about 0.15 G less potential in the corners and braking. Wow, that sucks for him! He should probably run a cheaper engine or a restrictor plate in order to run with less weight.

But what does 0.15 G mean in terms of cornering speed and time? There’s math for that too…

Single 60 Degree Turn

Turn Radius 1.23 G
(B20B, 2200 lbs)
1.13 G
(B20Z, 2376 lbs)
1.08 G
(B18C5, 2500 lbs)
50 m / 164 ft 54.9 mph, 2.13 sec 52.8 mph, 2.22 sec 51.4 mph, 2.28 sec
75 m / 246 ft 67.2 mph. 2.61 sec 64.6 mph, 2.72 sec 63.0 mph, 2.79 sec
100 m / 328 ft 77.6 mph, 3.02 sec 74.6 mph, 3.14 sec 72.8 mph, 3.22 sec

That’s just one corner. It’s not hard to see how this could add up quickly when applied to an entire track.

To be fair, this is a simplified example and the real-world drop in lateral G force due to increased weight likely won’t be quite this harsh… This assumes optimal driving and handling, and also doesn’t account for increased tire grip as a result of increased weight. Some tires gain more than others, but there’s a point of dimishing returns, and it’s never a good trade-off anyway. The weight and resulting heat adds other handling complications too.

Conclusions

1) More engine will typically be an advantage on the straights, despite carrying the extra weight, and it doesn’t really take any skill to utilize that.
2) Lower weight can offer a much larger advantage in braking and turning. It absolutely will take some skill to capitalize on that, but that’s why we’re here, right?
3) Although the balance between these two will vary from track to track, lower weight and optimal driving should prevail. A cheap good-condition B20 from the junkyard can compete with a hot Type-R engine in Front4!

4) If you can’t get your car down to low weight, you might as well run as much engine as you can for the weight you have, and/or use the option to “spend” some of your weight to run wider tires.
5) Gearing changes weren’t covered here, but it will impact straight-line acceleration and acceleration out of corners. That’s one part of why the Type-R setup is strong on the straights, and the B20’s could benefit with shorter gearing like a GS-R gearbox. There’s usually a trade-off with gearing, so this may come at a cost in other areas. See our article on Honda B-Series Transmission Gearing.

6) The 2018 Engine Output formula is intentionally simple and it works very well for many cases. Nothing is ever 100% perfect, and we are aware of some potential setups (nobody is doing this presently) where this simple formula may not provide the desired balance, so you should expect to see some rules adjustments in the future if this becomes an issue. As always, don’t put money or time into exploiting the rules, because it’s not helping you become any better of a driver, and any advantage you may gain will likely be taken away before long.

Weston

Front4 Series Co-Director #73 White 1995 Acura Integra

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