Why Asking “What’s your WHP” Is Stupid When Comparing Similar Cars

"Greenmobile Supremo Commando, BRZ Extrordinare" (jbezugs) 02/15/2020 at 20:05 • Filed to: BRZ, Dyno

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I have seen constant posts in Facebook groups that I’m a part of for the FRS/BRZ/86 platform that go something like this: “What are your mods and WHP numbers?”

What ensues is a complete shit-show of a dick measuring contest. I’m tired of seeing it over and over, so here is a long-winded post about why this bench-racing effort is mostly futile, and what the most viable solutions are to this issue. I’m sure this same thing happens within every circle of car enthusiasts.

The most important factor: every dyno reads differently.

A bunch of us in these groups/clubs have had our cars on the dyno with a variety of different modifications. But, there is no one “reference” dyno that everyone uses. We have all used a variety of different tuners who use different types of dynos (Dynojet, Dynapack, DynoDynamics, Mustang, etc.) that all bring their own ways of reading wheel power, and with that, have different correction factors. Even two dynos of the same exact model won’t read exactly the same. Calibration and correction factors once again can swing numbers around.

In summary: The tape measure you use matters just as much as what your packin’ if your talking strictly numbers.

Just asking for numbers from people is irrelevant w/o knowing what the baseline of a stock car is on the same dyno they ran their vehicle on - ideally the same car before/after mods and tune, on the same day.

With the baseline, you can get the truly important metric when measuring engine modifications - percentage gain, as well as the increase in area under the curve.

Here’s an example with my “Stage 2+” (I think) 2017 BRZ. My mods are as follows:

- JDL 4-2-1 EL Header

- Stock Air Intake with a new OEM Paper Air Filter

- Stock Over Pipe

- Stock Front Pipe

- Invidia R400 Catback

- Custom Dyno Tune from OnPoint Dyno

My car was tuned by Sasha with OnPoint Dyno. For reference, stock BRZ/FRSes make anywhere from 140-150ish whp on this dyno. How can I prove this? Check the link and come back and keep reading below:

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This basically stock FRS in the link above dyno’d at 155whp with the stock tune, an axle back exhaust and a Grimspeed Intake, which is the only aftermarket intake that actually produces reasonable gains on the factory tune  (anywhere from 6 to 10whp depending on the dyno). From talking to Sasha as well as conservatively looking at the gains from the Grimmspeed dyno, you could estimate a completely stock FRS/BRZ/86 to pull around 150whp and 131wtq.

My car made 176whp and 153wtq on the same dyno. Note that the baseline on my graph is not accurate as the car already had the mods installed on the vehicle.

Therefore, high level, the approximate percentage peak gains are about:

- +17.3% WHP

- +16.8% WTQ

And these are just the peak gains, not including the significant area under the curve increase (especially around the torque dip).

Now, when scouring through the ft86club forums, generally, it looks like Drift Office’s DynoJet is representative of an average baseline for most places, with stock FRS/BRZ/86‘s putting down around 167whp.

That baseline number is an +11.5% difference compared to OnPoint’s baseline dyno.

With this information, I decided to do some maths. Take that “forum average” baseline, and then apply a correction factor to my OnPoint numbers. The correction factor would be the 11.5% difference between the two dyno’s baseline numbers.

See how my car is at almost 200whp now? The percentage gains didn’t change at all from baseline to Stage 2+! Only the baseline number has increased.

Now is this method perfect? Of course not. Even compensating for “correction factor”, this is still a theoretical value given that the baseline cars were two different stock cars, where there can be variance between them.

So now, what’s the best method of comparison then? If you want to look at numbers, Dyno Days are usually the closest you can get when comparing cars side by side. This means that any car that wants to participate will be running on the exact same dyno, under the exact same conditions, on the exact same day. That way, the most important variance in comparing cars and their mods/tunes (the Dyno) has now been removed.

In having a few stock vehicles as well as a whole host of cars with different modifications and tuning methods - this should provide the most objective base of comparison that we can hope for.

But above all else, if you’re shopping for parts and trying to compare the increase in performance, look at the percentage gains - not just raw numbers.

Green86 > Greenmobile Supremo Commando, BRZ Extrordinare 02/15/2020 at 21:25

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“In summary: The tape measure you use matters just as much as what your packin’ if your talking strictly numbers.”

Lol

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > Greenmobile Supremo Commando, BRZ Extrordinare 02/15/2020 at 21:29

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I’m all for mods and such, but my grand scheme look at car ownership is this:

Q #1. Does your car make you smile and do YOU find it fun?
A. If yes, y ou win - this is all that matters ! If no, find a different car!

Q #2. What kind of car/amount of horsepower/top speed ?
A. See question # 1.

You can have the most modded out Ford Mustang with ridiculous horsepower or the crappiest East German Trabant built on the laziest Friday at the Zwickau plant in history....if YOU enjoy it, that’s the most important thing.

SmugAardvark > Greenmobile Supremo Commando, BRZ Extrordinare 02/15/2020 at 21:45

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Back in high school, I had a Chevy Cavalier (don’t worry, I know you’re jealous ) . On the J-Body forums, many claimed they had a “factory freak” car, meaning theirs was supposedly built on a good day (or something) at the factory and that they knew the car was making more than the advertised power numbers. Occasionally, this was backed up via a G-Tech or similar device.

This amused me for a couple reasons. First, the thought that the GM factory was so haphazard in building the cars that a huge number of them made wildly different power numbers. Second, that so many folks have a butt dyno capable of telling the difference between 120hp and 122 hp.

Nice to see times haven’t changed that much in 20 years.

Side note: I love that green color on your car.

19JRC99 > SmugAardvark 02/15/2020 at 22:50

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My grandfather worked for over 30 years at Ford. He said it was common for engineers or whoever to select a car so they could “try something.” So some cars do come from the factory a little better, or at least, they did.

His Mustang MAY have been such a case but I don’t run around claiming it because, really, who cares? It doesn’t make it some rare magical beast. 

Scary__goongala! > Greenmobile Supremo Commando, BRZ Extrordinare 02/15/2020 at 23:00

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G ood content, nice read . I’ll toss in my own little opinion. Doesn't matter how much power your car makes if you can't drive it well enough.

ITA97, now with more Jag @ opposite-lock.com > SmugAardvark 02/15/2020 at 23:57

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While I’d laugh at the butt dyno, there can be a surprisingly big variation in factory motors. Back in the miata shop days, there turned out to be meaningful variation in head castings as it related to the valve seating area on 1.8l NA and NB1 heads. When you have two or three dozen miata heads on hand at any given time, you learn that castings ranged from ones that looked perfect with the smooth transition you would expect, to ones with visible lip that was no bueno.

The different was something on the order of a handful of hp, but in a spec class that could mean the difference between being a contender and being 10th in 40 car field at high level races. At the time, the rules allowed no modification to the head in that area, so sunbelt and any shop that had enough enough motors on hand could build better stock motors from more ideal sets of stock, unmodified castings and matched sets of rotating assemblies (i.e, if you have 50 brand new, crate miata motors on hand you can start putting together of gram perfect matched sets of pistons, and rods, and so on... Once you have enough matched sets, you can even charge more the sets that are few grams lighter than others) for a few more hp for customers willing to pay stupid money for a shot a running up front (because everyone else at the front also paid stupid money for the same).

This was also true of the collector flange weld on OEM exhaust manifolds. There was huge variation of welds from fairly nice and smooth to big nasty globs sitting out in the exhaust flow (and also for a measurable impact on hp). At the time, no welding was allowed on the collector, and a tech inspector was liable to have all the top finishers pull their manifolds in impound after a bigger race to check for welds that had been ground.

This turns out to be the downside of “spec” racing. They eventually changed some of the rules to allow for folks to do small modification to some of this stuff to cover the variation of OEM parts, with the idea of keeping folks from paying $15K for a stock miata motor built from the best stock parts.

Greenmobile Supremo Commando, BRZ Extrordinare > Scary__goongala! 02/16/2020 at 00:27

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Yes, driver mod is the most important mod you can do! I’m still constantly learning and trying to improve. 

Greenmobile Supremo Commando, BRZ Extrordinare > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 02/16/2020 at 00:31

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100%. I think this goes back to the whole bench racing thing. When you’re actually driving a car, you don’t have a stop watch in your other hand for 0-60 runs. It’s the experience that’s the most important.

My BRZ is no where near the fastest thing on the road, but it’s a blast whenever I get behind the wheel and that’s what matters.

I’ve had extensive seat time in a 750whp, 6 speed Challenger Hellcat, and while it was completely and utterly hilarious and insane as you think it would be, the fact that I couldn’t even begin to open it up on the street was actually a bit frustrating. It made me appreciate my “slow” car that much more.

We’re here for a good time as they say.

Greenmobile Supremo Commando, BRZ Extrordinare > SmugAardvark 02/16/2020 at 00:40

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Yep, some things never change in this hobby.

Thank you! I had it wrapped back in 2017 before this Hakone nonsense from Toyota (*cough*I’m still waiting on royalties *cough*). Although the two tone brown interior makes me very jealous.

I’m just glad green is finally coming back in style at OEMs.

Greenmobile Supremo Commando, BRZ Extrordinare > ITA97, now with more Jag @ opposite-lock.com 02/16/2020 at 00:46

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Holy smokes, that’s fascinating!

In a similar fashion: talking to Sasha at OnPoint dyno, he has said there is a notable variation in the power output of stock FRS/BRZ/86’s that he has had on his dyno. He’s seen at lowest about 140whp and at most 150whp.   With a motor only putting out at most 150whp in stock form on the dyno, 10whp isn’t insignificant.

SmugAardvark > ITA97, now with more Jag @ opposite-lock.com 02/16/2020 at 00:59

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Great info, thanks for sharing all that. I should be more clear, it was amusing that an abnormally large percentage of the forum users genuinely believed their cars to be this way.

I’m talking, bragging about how they got 20hp from their intake and exhaust, plus another 10hp from their car being assembled better. And knowing this fact because, “they drove their sister-in-law’s cousin’s Sunfire that one time and it definitely didn’t pull as hard in the mid-range.”

And yeah, I hear what you mean on spec racing. I think I’m going to stop telling people that I was just flat out bad driving Spec E30. It was clearly the car’s fault. :)

SmugAardvark > 19JRC99 02/16/2020 at 01:06

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I could certainly see that more on Mustangs than Cavaliers. In fact, I have a bit of a hard time believing that any GM engineers even thought about them once they started rolling down the line.

With that said, my Cavalier was a very good car. Not in terms of performance. But I beat the crap out of it for three years doing autocross , rally cross, track days, and general high school/college stupidity, and it never once broke down on me. I even almost pooped in it once when I spun it hard at Sebring. Still refused to break.

ITA97, now with more Jag @ opposite-lock.com > SmugAardvark 02/16/2020 at 09:55

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Ha! That’s why a “spec” class should either run sealed motors from a single supplier, or base the rules off IT where mild porting and balancing and blue printing of otherwise stock internals means everyone can run a $5k motor and be competitive instead of making folks run a $15k balanced and blue printed motor from the supplier that was willing to order enough crate motors to be able to build them from oem parts.

RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars > Greenmobile Supremo Commando, BRZ Extrordinare 02/16/2020 at 16:28

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Amen! :)

Long_Voyager94 > RallyDarkstrike - Fan of 2-cyl FIATs, Eastern Bloc & Kei cars 02/17/2020 at 07:02

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You have the answer to Q #1 only partially correct.

A. If yes, you win - this is all that matters! If no, mod it until it it does.

i86hotdogs > ITA97, now with more Jag @ opposite-lock.com 02/17/2020 at 11:51

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Same here at Ford’s engine plant. We build the standard ecoboost V6 you see in the F-150 and such, we also build the high output version that goes in the Raptor and new Navigator. The HO uses a special coated main bearing for the higher power output, but sometimes we will install those in the base engines if there is a stock shortage. So there are a handful of base ecoboost v6's with better main bearings than others.

i86hotdogs > Greenmobile Supremo Commando, BRZ Extrordinare 02/17/2020 at 11:53

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I can assure you that there is very little talk about power in teh Transit Connect community. 90% of it is asking where to find F ocus wheels because they are a direct fit and look better than the TC wheels.