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Old 10-21-2013, 11:57 AM   #1
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Default ideal fear ratios with 300+whp

I am wondering what you gays think is the best gear ratio for our cars making over 300whp. I should be around 350whp when all is said and done and car more about fuel economy than acceleration. I am thinking about a 8.8 rear end and can get endless options. What is the best?

What will it do to my fuel economy if I find myself in boost more on the highway, even though my revs are lower?

If you could have any ratio what would it be?
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Old 10-21-2013, 12:03 PM   #2
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Somewhere between a mild erection, and shitting my pants is my preferred fear ratio.

Oh, gear ratio? All preference and depends greatly on the size of your turbo. My preferred gear ratio would be something like a 5 speed with a 3.6 gear, but that wouldn't hold up to any power anyways. Would be nice to have a topend of 150+ mph and a usable first gear for once though.
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Old 10-21-2013, 12:07 PM   #3
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Ideal is 3.27....but they don't make those... so 3.63 is the best expensive solution available....
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Old 10-21-2013, 12:10 PM   #4
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They make 3.27! Or something really close I am sure. 3.23 perhaps?
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Old 10-21-2013, 12:17 PM   #5
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V8R will do a 8.8 w/ 3.33 that will work with the miata trans. But then you can source what ever rear gear you want.

That is what I've read, but I've never called them to ask.
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Old 10-21-2013, 12:52 PM   #6
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Quote:
Originally Posted by Amellrotts View Post
They make 3.27! Or something really close I am sure. 3.23 perhaps?
You talk the talk...shut up
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Old 10-21-2013, 12:54 PM   #7
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Originally Posted by viperormiata View Post
V8R will do a 8.8 w/ 3.33 that will work with the miata trans. But then you can source what ever rear gear you want.

That is what I've read, but I've never called them to ask.
I've heard this too and if a complete solution was available for under 2k I'd probably go for it since I want to have v8 swaps in my future anyway
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Old 10-21-2013, 01:30 PM   #8
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You talk the talk...shut up
WTF? My thread! I am serious about doing the 8.8 diff swap, or didn't you read my OP?
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Old 10-21-2013, 01:31 PM   #9
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I think that the 3.9 gears are probably the spookiest gearset.
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Old 10-21-2013, 01:40 PM   #10
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WTF? My thread! I am serious about doing the 8.8 diff swap, or didn't you read my OP?
If you find a 3.27'ish gearing in 7" format (IE. Will fit in Miata diff) then please share because I've only found riddles and cancelled group buys.

Take no offence...I'm simply bitter about this.
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Old 10-21-2013, 01:47 PM   #11
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Quote:
Originally Posted by Amellrotts View Post
I am wondering what you gays think is the best gear ratio for our cars making over 300whp. I should be around 350whp when all is said and done and car more about fuel economy than acceleration. I am thinking about a 8.8 rear end and can get endless options. What is the best?

What will it do to my fuel economy if I find myself in boost more on the highway, even though my revs are lower?

If you could have any ratio what would it be?


Seems rather strange to me...
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Old 10-21-2013, 01:54 PM   #12
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I said in my OP that I was considering the 8.8 Ford IRS diff swap. I am considering buying the 3.6 R&P for my Torsen, but if a 3.27 is a lot better then I will do the fab work and spend the money.

I know it seems weird that I would ask about fuel economy but this car is still a daily driver. If I can retain some fuel economy then maybe the wife won't get so bent about the $$$ I am spending. Besides, I would much rather take this car on trips than something else so if I can have better economy then it is an easier sell to her. I feel with 350+whp that even a tall ratio will still accelerate plenty fast enough for me since I have no interest in street racing. I am building a Locost7 that I will probably gear to max out at 120mhp for serious acceleration.
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Old 10-21-2013, 02:00 PM   #13
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I mean... what kind of fuel economy are you going for?
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Old 10-21-2013, 02:05 PM   #14
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I don't think the mpg improvements of doing this will be as drastic as you think. Properly tuned, our cars don't eat that much fuel even when turning 4k rpm on the hwy at super low load. So unless you plan to do 100k miles in a few months, your goal with this swap shouldn't be as focused on mpg. And if it was, you shoulda just gone with a gt3076 or gt3582 turbo that doesn't come on til 5k or something.

Now, if you want a bulletproof rear that will also be able to put the power down most effectively, then this thread will be much more useful.

(PS: hitting boost at low rpm will also have a negative impact on your mpg. IMO best solution to your mpg problem would be to completely disable boost control with the flick of a switch and a very well tuned fuel and spark map, then when you need to put down power, you hit the switch and voila: bewst......I'm actually doing this on my current car)
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Old 10-21-2013, 02:10 PM   #15
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2.26 for ultimate fuel economy and +250mph top speed runs.
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Old 10-21-2013, 02:39 PM   #16
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So 3.6 it is then.....Thanks Vlad. I was planning on doing the toggle for EBC anyway so I could easily set it to gate pressure as a valet mode for letting others drive the car.

Another benefit of the taller diff is the kind of driving I like to do in the mountains will benefit from being able to stay in a gear a little longer....but truth is the turbo made my car an automatic for mountain driving. When we were hitting the canyons pretty hard all my friends were shifting constantly and I left it in fourth most of the time....lol. LOVE this turbo thing!!!
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Old 10-21-2013, 02:58 PM   #17
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The 6/3.90 setup is so short for that power level and 3.60 is such a conservative increase that I'd have a tough time not entertaining something longer. Wiki lists these as 8.8 FD options: 2.26, 2.73, 3.08, 3.27, 3.45, 3.55, 3.73 & 4.10

Perhaps 3.45 would be a nice compromise if they're readily available.
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Old 10-21-2013, 03:01 PM   #18
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However, anything other than a 3.6 drop in requires quite a commitment. I know lots of talkers on here make it sound like its basically a 30 minute install and costs mere pennies more than a 3.6 rp install, but I take that with a giant grain of salt - if it was as easy and cheap as it sounds we'd have half the forum rockin this setup already.

Just a thought
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Old 10-21-2013, 03:16 PM   #19
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Also food for thought: I get 31-33mpg on the highway in my 6spd/4.10 car.

Sooo....
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Old 10-21-2013, 03:18 PM   #20
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Woh woh woh.....
I know it will be a lot of work. I know a lot of people talk **** and are expert fabricators while sitting at their keyboard. That is not me. I don't claim to have any skills, just endless desire to get what I want. I am prepared to do the work if it is worth while. The cost will be considerable even doing the work myself. I am basically disabled and don't work anymore so this will be a good way for me to stay busy even though the funds are extremely tight. I am into my build for over $18K so far so why stop now? Maybe I just need another litter of puppies to sell for the $$$...lol

For real, what is the best ratio for my application? Stepping down to the 3.6 is almost a 10% change and if I can turn 10% less revs and maybe save close to 10% fuel while on the highway then I don't mind spending the <$500 to get it, especially if I can use first gear again!

If 3.27 will yield no better fuel economy then I will not spend the >$2000 for the conversion (I am sure I will want 600hp+ custom half shafts). If it will see a 25% improvement then I will seriously consider it....doesn't sound like that is going to happen though.

As much as I enjoy this setup I wonder what a higher static compression ratio build would yield for economy?
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