Engine Upgrades Making No Difference

I tried several broad Google searches before deciding to create a thread on this , but I’ve been noticing a recurring issue the last few days and wanted to get feedback and see if anyone else is having this issue (if it even IS an issue). Note: Playing on Xbox One X, and game is up to date as of 12/22/2019.

For several days now I’ve been going through my car collection and picking a few high-end cars for upgrading for specific uses. Some I’m going for a rally build, some for drag racing, and some for street racing. Note that I’m usually starting with a car designed for that purpose (in that category), but not always. In each of these cases, I’ve had several cars that gain no discernible benefits from engine upgrades after swapping engines and/or aspirations. I’ll literally put in a different engine and then go to change parts, but will get no added benefit, and in some cases a dip in performance with each new part. Here’s an example:

I was curious to see what kind of power I could get out of a 2013 Caterham Superlight R500, so I went to upgrade and see. Swapped the stock engine for a 3.2L I6 for added torque (note: this is the same for EVERY engine). Then I go to aspiration and add a single turbo, which adds horsepower, but all of the ratings turn red (except speed). Seems odd, but moving on to engine parts. Intake has a positive effect, but fuel, ignition, engine block, turbos, intercooler, and oil ALL have a negative effects on index numbers, even though the power curve is going up.

What’s going on? How are these having a negative effect on everything but speed? Surely they would have a positive impact on acceleration or launch at the least.

That was just an example with the car I was currently looking at, but I’ve had equivalent results with several other cars (from different categories, I should add).

Any insight would be appreciated.

Couple things going on here;

First is those out of ten numbers can be pretty misleading and/or just not enough info. For example sometimes upgrades will improve 0-60 but hurt 0-100 (or other way around) which can cause the acceleration stat to be red.

Acceleration and top speed are often very dependent on how gearing is adjusted, and the 0-10 stats don’t change with tuning, just with upgrades.

If it’s RWD on tires that aren’t sticky/wide enough, then at a certain point engine upgrades won’t make any difference no matter how much power you add, UNLESS it’s an upgrade that also decreases weight like the intake or exhaust. (This can be fun for making silly sleeper cars, since you can make like a 1500hp B class monster, but also really impractical)

Anyways, there’s more to it than that and I feel like I’m not explaining it well at all… so I’ll tldr this by just suggesting that you focus on tires and weight, then worry about power.

I hadn’t looked at some of the finer details as far as 0-60 vs 0-100, so that makes a little sense, and the fact that too much power might be lost on a car that can’t accommodate may help to explain the rest. It just seems really odd, though, since I’ve had it happen across several types of cars and tuning for different purposes.

I should probably clarify that I’ve been tuning cars for years now, and I have it down to a bit of a science (for my purposes, at least). I start with all the drivetrain and transmission parts first, then tires, suspension, and then I move on to power last. I’ll always tune my gears (usually only have to adjust the final gear) and brakes, then test drive and adjust the differential and suspension for understeer/oversteer before going into an actual race.

Anyway, that gave me some things to consider, so thanks for responding!

If anyone else has any suggestions, too, let me know!

I have my own (empty) rant on the same topic, but on low end cars :-

https://forums.forza.net/turn10_postst159738_Where-did-my-power-go---aka-are-the-numbers-lies.aspx

In numerous other cases in very mid field cars I’ve noticed obvious discrepancies between the on-road performance of the cars and their claimed performance via that panel.