Perhaps this should land in a different Section of the Forums, but I’ll put it here.
I like cars, and I know cars, but I will admit that I don’t know cars, as in precisely how they function and what to do to make them function better. So I’m asking the people of Forza Forums, perhaps an expert will find this and enlighten me: is the 1997 Stagea’s RB25DET really a more capable engine than the RB26DETT found in the R34 Skyline GT-R? A maxed out Stagea pushes 910hp and falls into low S2 class, while the R34 Skyline GT-R makes “just” 798hp maxed out, and doesn’t leave S1 class.
I know that the whole RB platform has seen changes across its production years, one of which if I recall correctly was modifying fuel injection for RB NEO engines which debuted after the Stagea we now have in the game. What I don’t know is if the RB26 is accurately portrayed in Forza to make a smaller max power output than the not-top-of-the-range RB25. Because maybe things are how they should be and I’ve been living under a rock, or maybe Forza really doesn’t care about accuracy more than I’d expect. Or maybe it’s just P2W, even though the Stagea isn’t the best handling car for obvious reasons.
A quick Google search on real life rb26dett modifying should clear up your question about Forza. 
Some say Google searches aren’t trustworthy, that’s why I came here. This also shows something very nonsensical in Forza.
Okay, so to clear up a bit… both engines are highly capable. People unfortunately always rank the RB series engine as difficult to build and make reliable power(which I understand reliable isn’t an issue or a thing for forza) but look at the boys in Australia, they have rb26’s pushing well over 1200whp reliably. T10 and Playground seem to be suckups to the 2jz unfortunately(except for the 2jz-ge in the sc300 which is underwhelming but it sounds good). Now, that being said, I tend to believe the racing 3L turbo is a RB30 due to the hp/torque graph looks so close to the RB26 graph with how it shows the power and torque build. But im not sure if thats what T10 did. I know back in FM4 the RB26 pushed over 1000hp which was awesome. On FM8 it pushes 986hp or so. Im not sure why they nerfed it. Its sad.
Hey mate,
I am australian and i have spent the last decade working on JDM cars with my specialty being Nissan.
I have a large collection of JDM cars and also RB engines from stripped to stock to fully forged and built.
We have a lot of very powerful RB’s here and for good reason.
All the RB blocks are identical except the RB30 which is slightly taller, and the RB20 which is the same block as the RB25, RB26 and RB25 NEO just with a slightly smaller bore.
There is also a company in the city where i live called Bullet Race Engineering who make Billet RB (and other) engine blocks that are capable of 3000hp+
Last week they finished a fully built RB20 for my drift car and that is a reliable 750hp capable engine, and it is a 2 litre!
All the cylinder heads are what is really different between the engines
Rb20 is restrictive compared to RB25/26det heads
Best head in my opinion comes on the RB25DET Neo
RB30 heads are only single cam BUT with a slight modification to the block and head the RB30 block can suit a twin cam head from a 20/25/26
You shouldn’t expect too much difference in performance between the RB25 and the RB26 if they have the same modifications.
The RB20 with the same modifications will me at least 20% less torquey than the bigger engines but can safely rev a lot more and the RB30 will make slightly more torque than the 25 and 26 and will rev good too with the right modifications, but never as good as a 20.
Forza should have the option to swap in a billet 3.2 litre RB25/30 with a modest 1500hp
I would love to see us be able to pick blocks and heads in the RB series of engines because there are SO many possibilities of combinations.
Forza really let us down with the RB’s in the games.
If youd like any more information, dont hesitate to ask
Also, the RB25DET Neo differs from the rest of the series due to variable cam timing.
It does have a different injector design to the rest of the series but that is neither here nor there 
Short answer is: It’s Forza, and some times they simply miss or omit the details.
Long answer is: It’s FOOOOOOOORRRRRRRRRRRRRRZAHHHHHHHHHHHHH and some times they simply miss or omit the details.
It’s not a “SIM” It’s a Sim-Arcade - with emphasis on the ‘arcade’.
While the names are real - the performance stats and tuning are ‘all made up’.
Because - it’s a game - and in such a game like this - you always have meta - and meta
isn’t real life. e.g: Bugatti is commonly known to have the fastest production cars - but - are they actually the fastest production cars in the game over all others because that is true in real life?
Nope. It’s all in the name of balance in game play in the races.
This is a non-answer then
I mean we’re talking about a game where you can reduce the weight of vehicles using magic.
Frankly, I’m a little forgiving of the upgrade inaccuracies. Making every car’s and engine’s upgrades accurate would severely slow down the car addition pipeline. I would appreciate less cars with more accurate upgrades, but I’m not representative of the majority. I’m making an assumption here, but I think most are satisfied with the upgrade system being “good enough”, especially if that means more cars in game.
I know this doesn’t answer your question directly, and I don’t actually know the answer to your question, but…
… you can put a V8 in a Ford Focus without modifying the hood in this game. Realism isn’t exactly it’s strong suit.
I just want the RB26DETT to be somewhat viable
No, it’s the only answer, and you happen top not like it.
I mean it’s the truth. It sounds like you want this game to be a hardcore simulation, and that’s never been the goal of the Horizon series. There are other titles out there that focus much more heavily on car fidelity.
I don’t need this game to be a hardcore simulator, though an open world sim would be awesome. I just want upgrades to be somewhat consistent across all cars, and there’s no need for the discrepancy between the RB26 and RB25 in FH5.
In reality? Again, this is a game and thus isn’t reality and on top of it all - the game has to be balanced - or “biggest engine would always win no matter what” and then that would be all you’d be able to use or always lose.
It’s more than just stats copied from reality - there is more to it than that. it’s not as simple as you’re making it seem simply because in real life actual stats say one engine is better than another.
I get you, I hear you loud and clear - and not saying you’re wrong - only that your expectations about this are muddled by your insistence that this game should essentially be more realistic not understanding that what you see as an imbalance or something incorrect is actually a balance in and of itself to other non-realities that make up this game.
How dirty T10 did the RB series engines cough cough R34 done the dirtiest imo.
Supra riders and they really really like supra’s and seemingly hate skylines. Been a normal thing with T10 devs. I mean the fact that there’s more than enough proof of the engines being so neck and neck with the 2JZ that it should at least not be done so wrong in the game. Like 2JZ & the WP version are 1400-1600hp and the R32 gets 800ish and the R33/34 are apparently only capable of an FBO lmao