Youre right when it comes to city driving I felt like the 4.08s had better gas mileage , I believe for that exact reason you stated. I mainly do just highway though and noticed immediately.

 

The human mind plays tricks and can be pretty convincing. You are also prone to bias. Real scientific experiments have controls and attempts to minimize as many variables as possible, and tries to cut out human errors altogether. Your comparisons have too many variables and common sense goes against some of what you're saying. Your excitement and even mentioning your power (which in itself is already different between comparisons) shows you're probably biased in a particular direction.

Shorter gears = faster acceleration & lower top speed. This is a fact. Having 4.08 gears will accelerate quicker than the stock gearing. FI guys use stock gearing because of their lack of traction, not because it's quicker (quicker != faster). In order to test which accelerates faster, do a 6th gear pull from like 40 to 100 with both rear ends back to back (somewhere not illegal). Using the highest gear only minimizes traction issues, cuts down other variables like shift point and shift time, and it's easier to differences in time since it accelerates slowest. Or, you can do a 5th and 6th gear pull starting and ending at same speeds and realize shorter gears will accelerate faster (only difference here will be the transmission gearing and that's the same concept).

As for MPG, that really depends on how you drive and the distance driven. As a human, it's nearly impossible to keep everything exactly the same, especially driving style, and road conditions are out of your control. Driving style will determine MPG overall, but you can still compare your mileage. To do that, just hold a particular speed in one gear for X amount of time (no stopping or any other changes) then repeat with the other FD. The gearing that lets you stay at a lower RPM will yield higher mileage in most cases, assuming you're on a flat surface.

 

I know all this I've had 4.08s for the last 3 years and will be building another diff with that gear set. As for my power level between the 2 videos, they are close , if anything I probably have a little less in the stock gearing video due to running air filters, when I race I dont run filters and my car was tuned without air filters in the air boxes.
outside temp was nearly identical in both vids (75F) , also kept the same stretch of road as before. Thing is, my shifting was better in my 4.08 video and I also didnt have traction problems, yet with the stock gear I spun a good bit in first and the speedo even stops at 55mph for a split second and even moves backwards some lol still managed to get to 100 and 140 a bit quicker. Of course this is all just my personal testing and you're right the best way to compare is to do what you said but I'm not about to find another 4.08 and do a 6th gear pull with both gear sets to compare lol . This is enough proof for myself, others can watch and take what they want from it of course, which is why I put the vids up to watch and discuss

 

Oh and I though turbo guys stick with 3.5 or even 3.3 gears not so much for traction since there are better ways in fixing traction issues like slicks or drag radials but to stay in boost longer per gear?

 

All I was saying is that you shouldn't claim that 3.5 accelerates faster than 4.08 gears when it doesn't. Your videos simply show acceleration of each in different conditions with variables but shouldn't be directly compared with one another. The MPG part was really for the other guy.

The FI guys stick with 3.5 or swap to 3.3 because they can stay in lower gears longer without having to shift as many times going up to the same speed and thus loosing boost/time. It doesn't offer any acceleration benefits when compared to shorter gears when traction isn't an issue and the boost itself doesn't change as it's not mechanically dependent on gearing. Longer gears do allow them to get to higher top speeds.

 

I felt a noticeable loss when switching back to 3.53 after having the 4.08s for several months.

 

^ Are you talking about MPG? Maybe you're shifting at different points, staying in gears for different lengths of time, time on gas vs coasting, etc -- too many factors. Driving style, which changes with different FDs because of different acceleration rates, is the biggest factor for MPG. The only way to truly compare is the method I already posted.

 

Picked up this baby today
let the fun begin

 

Whats the plan?

 

No - was talking acceleration.

 

I'm thinkin just slowly build it for fun and put a 37VHR crank in it, forged internals while I'm already in there, some aggressive cams, springs, retainers etc.etc. Gonna try and get my hands on a GTR intake manifold which ill try to bore out and fit dual 09 maxima throttle bodies along with proper sized piping and MAF housings of course. Ill put my PPE headers on it when the time to swap comes around, might go boost by means of a BP style big single, still debating though, no rush at all though. Itll be set up for E85 so ill up the fuel system components for the extra flow needed for E85. Any suggestions are more than welcome

 

That's gonna be awesome...

 

Finally swapped out my POS fitting Motordyne XYZ pipe.

This was all the clearance I had with stacking 3 gaskets per side.




Here's the fitment with new pipe.

 

Was the short-length issue from the XYZ pipe or the PPE headers or both? It seems only those with the headers seem to have issues. Also, is that a titanium y-pipe?

 

I think it's a bit of both. XYZ pipe is very close to the tranny brace to begin with.

Yup, that's Tomei Y Pipe. It's also length adjustable to some extent to compensate the short-length issue.

 

Very interesting. Iv noticed on some weird driving habits as well as start ups and had a nasty nasty vibration metal on metal sound which im 99.9% its my xyz. Maybe tomei will be next choice. Any better piks? Also thx 4 posting

 

I posted a gallery here.
http://imgur.com/a/cpXLb

Only problem with Tomei is the inlet diameter causing some rasp and hiss.
60.5mm (2.38") to 70.5mm (2.78")

I will have to live with the extra rasp/hiss until I can find a 2.5" to 3" that fit better than XYZ.

 

Well that's also a bummer. What exhaust you run? Id love a 2.5 to 3" y but would be pissed if it didn't fit better

 

I got the Amuse. At least everything after the header is titanium now.

 

Let's hear this thing sing...

I don't mind rasp...it's like shots with no chaser