Red Sport vs SS final gearing discussion +more - Infiniti Q50 Forum
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post #1 of 10 (permalink) Unread 12-01-2018, 03:51 AM Thread Starter
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Lightbulb Red Sport vs SS final gearing discussion +more

OK, so we all know the Red Sport has a lower final drive (Diff gearing) than the other offerings. I'd like to discuss the real world differences here.
Supposedly the lower gearing would make the car "Quicker" right?
Well maybe not. Our turbo efficiency range is low with power falling off at about 5500 RPM. So maybe the higher rear end keeps you in that range longer... maybe?
The other thing is can you hit redline in a 300 hp SS with the higher gearing?
Granted tuned/JB4 the RS and SS are close to the same.
Same mods RS vs SS which is faster in the 1/4 and which is faster top speed?

Also, MPG differences? Again SS vs RS same mods. Discussion on that too.

Is the RS with the dual water pumps a real noticable or needed difference? Or is it just more moving parts to go wrong? Same with the optical turbo sensors? What advantage or disadvantage are they? Desired or cumbersome?

Real world drivability differences?

My MPG with my RS is per tank in the 22-23.5 MPG range mixed. Highway 24ish at 72 MPH. Sweet spot?? Over 75 it opens up and starts to breath. 70 is pretty good. 65 is ok but not as crisp. BORING!

RE: Top end. I have not been over 137 yet. I will track my car this spring. The Porsche club does a track day to raise money for charity. It's not 1/4 mile but a closed real race track. I'll find out hopefully this spring what my top speed is. The EcuTec tune eliminates the speed limiter, I'll see if that is even needed I suspect it is. I think 160 MPH is attainable. But will the car be able to handle at those speeds?? I know at 135 it does.
Let's discuss these things here.

Midwest Hoonigan posted this video and got me thinking so lets do it!

Video link: https://youtu.be/AxmqZLU-SHQ
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post #2 of 10 (permalink) Unread 12-01-2018, 09:54 AM
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Hey John I've had the SS for seven months, average 19.5 with the JB1 at +3, now I have the RS with the same JB1 Average 22.6 all city driving.

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post #3 of 10 (permalink) Unread 12-01-2018, 11:07 AM
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Gearing is usually explained as torque multipliers. So if an RS has a more aggressive gear it may give the impression of more torque when compared to the SS. The RS will go through the RPMs faster while the SS might be a little slower through the RPM range. The benefit to the RS is the torque comparison. However the SS being a bit slower through the RPM band also means in remains"in boost" a little longer so it may result in a higher mph at top end. If you compared the 2 cars at identical mods (tuned at same psi and not stock power levels)then you could probably expect the RS to put out a higher torque output while the SS may produce a higher horsepower number.
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post #4 of 10 (permalink) Unread 12-01-2018, 01:12 PM Thread Starter
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That was what I was thinking .. the higher gearing would keep you in the efficiency range of our stock turbos. Bigger turbos forget it. That fixes the entire powerband adding the top end to prevent the power drop at over 5500 RPM.
But school is out on top end till get on the oval. Often a vehicle is not able to redline in top gear due to comboned drag factors.
If my Red Sport can't redline in 7th a SS will not either. Well maybe. There is some math needed there with dyno plots to see the torque at MPH and what RPM that equates to.
That's a project I'd get one of my engineers on my team to do. (Gad I miss having those resources like I had at DEC) @Avedis53
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post #5 of 10 (permalink) Unread 12-01-2018, 02:04 PM Thread Starter
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Gad, I think to much..

Was realizing that now that I am driving my truck again that in my manual transmission 5th gear is "direct" drive and has the least power loss and is the "strongest" gear. With the torque in a "chipped" Cummins diesel 5th is your beater gear.

Now I'm a real automatic transmission dummy, but is their an equivalent to this in our 7 speed transmission?

In manual mode you can keep your RPM in the sweet spot zone easily. In real world driving I believe the lower gearing is better. For me. If there was a "direct" gear in our auto that would be the play gear.

Tons of barely traveled roads I know here by heart, so on blind spots I know where to behave or not. Driveways, houses, unseen sharp corners etc.
Soooo at those speeds, 60-100 the lower gearing may be more suitable.

For example the road I live on is posted at 35, but the average speed of the normal traffic is 45-50 MPH. 60 is not uncommon at all. If you go 35 MPH you pi$$ people off. Lol even the cops get irritated but know people will go the limit when they are behind them. Must be frustrating lol.

I do have a few favorite roads to drive hard on. Some with long sweepers, speeds 45-125, and others more suited for my Miata with tight packed twisties.. max speeds around 35-70 ..

Just more to ponder. I can't imagine living in a city like NY or Philadelphia, Detroit, LA etc. A Lux would work there. I would not get a RS unless I took road trips out of the city often.

Last edited by JohnInNH; 12-05-2018 at 03:07 AM.
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post #6 of 10 (permalink) Unread 12-05-2018, 03:13 AM Thread Starter
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Bump.
I thought this would spawn some more discussion. RS vs SS.

The more I drive my care the more I enjoy it. Finally the owner of the shop where I get all my work done took it for an extended test drive post tune. was smiling big time. admitted it was one of the fastest street cars he has driven. "Now that's a sleeper"
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post #7 of 10 (permalink) Unread 12-05-2018, 08:12 AM
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Quote:
Originally Posted by JohnInNH View Post
Bump.
I thought this would spawn some more discussion. RS vs SS.

The more I drive my care the more I enjoy it. Finally the owner of the shop where I get all my work done took it for an extended test drive post tune. was smiling big time. admitted it was one of the fastest street cars he has driven. "Now that's a sleeper"
Now that I have been driving the RS for two months, and seeing my son's smile when I have some open space, or having other drivers look at me and say holy crap, your car is fast.
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post #8 of 10 (permalink) Unread 12-05-2018, 12:49 PM
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John:

I get 18.3 mpg combined. And that is with forged, non-run flats and CF driveshaft. In theory, I should be doing better. I don't know if there is any good way to get an idea of the mpg difference in a forum.

Have you tracked a car before and do you know how to prep for it? If not, I have oodles of truly novice advice having learned from my own mistakes.

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post #9 of 10 (permalink) Unread 12-05-2018, 08:21 PM Thread Starter
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Try looking at this link. My last tank was 21.7 mpg but average speed was 38 MPH so lots of idle time.. and around town.
MPG Q50 link: 2018 Infiniti Q50 MPG - Actual MPG from 16 2018 Infiniti Q50 owners
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post #10 of 10 (permalink) Unread 12-06-2018, 02:07 PM
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I have 15k miles on my 2018 RS that I bought in Feb.


I have averaged 21.6 with mostly freeway, but rush hour driving.


Axle back, then Helmholtz and JB4 for most of the miles.

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