Power/weight ratio vs PI

Does anybody find it interesting that some engine conversion options have a higher power/weight ratio with a lower PI than other options (and vice versa)?

For example, all else equal, for the 2003 VW Golf R32 2003, the 3.7L V6 with a race centrifugal supercharger has a HP/weight ratio of 0.155 and a 612 PI, while the 3.7L V6 with a race positive displacement supercharger has a HP/weight ratio of 0.152 and a 627 PI.

Why would anyone ever take the 3.7L V6 with a race PDSC versus the race CS? It’s a higher PI for a lower power/weight ratio.

What might explain this difference?
-Do the engine power curves differ (i.e., the centrifugal SC has a broader curve)?
-Is the gearing for each engine a factor?

PI of an engine is calculated for power and torque over the whole powerband.
Centrifugal superchargers only increase power at high rpm and thus cost less PI/power than turbos or superchargers.

In a racing situation (especially in this Motorsport with race gearbox being meta) you ideally only use high rpm. Thus, the PI cost of turbos/superchargers at low rpm is basically wasted.

Thats why centrifugal superchargers are the most PI-efficient aspiration and should be the go-to upgrade if possible.

This also explains why electric engines are the worst engines available.

It would be easier to show it alongside engine graphs but this game has none displayed for whatever reason.

4 Likes

Thanks. So it’s clear the game really needs horsepower and torque curves for all the engines, both stock and conversions.

1 Like

The dyno graph was in prior installments, and bringing it back is currently 29th in vote count (with 124 votes) in the Motorsport Features section of the Suggetions Hub (SHUB):

3 Likes

This, and also fact that pi don’t include rpms after redline, so cars like, E36 M3, Miata, BRZ, 97’civic, ITR, p.550 or viper V10, 1.3R engine swap, that have rly long redline where they don’t lose power, have big advantage. P. 550 is probably the most PI broken car, it got like 5k rpm with high power near max rpm, but since u can redline up to 6k rpm w/o losing power, with good gearing, u are almost always on redline while driving this car.

1 Like

So if HP/weight is not a good measure (understandably), how about 0-60, 0-100, and 1/4 mile times? Those are affected by gearing, aero, and other tuning settings, but if you assume the stock gearing/tuning settings (which is consistent between engine conversions for a specific car), these times might be a reasonably consistent way to determine which engines/configs for a given car are faster or slower, for a given PI. (Asking because I notice engine configs that have slower 0-60, 0-100 and 1/4 mile times with a higher PI, and vice-versa.)

Well power to weight ratio is the most accurate way to benchmark cars, since 0-60 or 1/4 mile time includes 1st gear lunch, that is totally pointless in circuit racing, the problem is, pi calculation does not include power curve after redline, and measures only specific part of power curve, like 75% to 100% rpm (but it also is dependable on transmission default gearing, be it stock/sport/race transmission), while player depending on car, usually uses range between 85% to 115% of max rpm (where redline starts)

Or like in horizon games, f4-turbo engine swap, u get power peak between 30-50% of max rpm (totally broken engine)

I think to fix pi issues we need system like in Gran Turismo, measure only max power, and give player ability to flatten power curve, tho that would make ev engines op …

Other solutions is… To make hard rpm cap in place where redline starts, it’s simple solution… It would instantly nerf all op engines, if u can’t redline abuse, u won’t gain any advantage from higher power to weight ratio, because u won’t be able to use peak power all the time.