I track my car on various tracks in France.

Some are really twisty like Lohéac. My Vmax on the main straight is around 175-180 km/h. With stock diff i am mainly in 2 and 3. I'm not in the powerband quite often, in some turns the 2 is to low...

Another is Fay de Bretagne. It combines very twisty sections with a long straigh (900m) where i take 220km/h with the stock diff (limiter of 4th).

In the twisty section the car lack of juice in 3th and is too high in 2...And sometimes to low on 2 ..

And the Bugatti Le Mans where power and elasticity is really important. With the stock diff the car lacks of juice in the exits of most corners, which are in 3.

Theses parameters made me choose this diff, i though that on most corner exits the car would be faster.

Now i will drive on theses tracks and probably some new ones (we have a lot of tracks in France, we're lucky) to see if there is a gain...

It seems I am the only one in France with an HR and a 4.08 drive, so since in US the community is bigger with a lot of track fans, i asked if someone made the raw comparison between the two diffs on the track...

I precise i don't care at all of the Drag strip, for me it's not racing (it's a personnal point of view, no offense)

Thanks

ps : i'll keep you informed of my results in none of you had made it before me

 

I run 19's with 275/30's on 10.5" wheels in back. I haven't dragged the car in years. If I did, I would run 17's with DR's. I use to track the car sometimes but haven't been using the car much.

From a roll or 20-30 mph & romp on it the 4.08's are a lot of fun.

 

i went 3.9 FD and LSD and was very pleased. Improved times to 60 mph by .3-.4 sec. 2nd tops out right at 60mph. All gears seem to be right in the sweet spot. have yet to take it to the drag strip

 

So the new diff may have helped in those areas...but hurt in other areas that were previously suited to the stock diff.

It's a tough balancing act, eh?

 

Great thread.
I've just switched over to 4.08's and a quaife LSD ('07 HR). Super excited to try the new mods on the track this weekend. I found that I was exiting turns in the low end rpms of 3rd and waiting too long to get into the power band.

For street driving 2nd gear is WOW. I used to really like 2nd on the 3.5 fd but now....the car launches. Way more alive and angry now. I much prefer this gearing for fun factor.

 

I agree with you the fun factor is really up

Let´s hope the laptimes will also go down.

Do you record your laptimes ? If yes please give us some feedback of your laptimes for this week end

 

From my understanding, it really depends on the track.

Here's an example I dug up a while back

3.9FD right, 3.5FD left :

 

^interesting vid. I noticed the 3.9's were being shifted sooner, I liked watching when the driver shifted or not shifted just a bit sooner/later than the other side.

 

i know this vid. but since it´s a DE with 6600 redline, and not as happy in the high rpm range than the HR...

0.4 s of difference is not significant since the 2 times are separated by 6 months, lot of things can change...driver skill, temperature humidity, track condition.....

 

keep stock gears and make sure a quaife is in there... 4.08's arnt honestly worth it unless your doing a lot of tight autocross and caught in between gears with stock ratio...for acceleration sure it feels faster but if you have taken a physics class your actually only shortening the gears and you will need to shift more so you honestly gain nothing because you have to shift more...if that makes any sense...save your money get an lsd and spend it elsewhere...

 

It does depend on the track. My problem is that I was coming out of the corners that lead to straights in a low rpm 3rd gear. Now with the 4.08's I'm in the sweet zone of 3rd.
I managed to shave 2 seconds off my old lap time of 1:29:27 which I'm super happy about (being my 4th HPDE)


old lap time with 3.5's


-sorry about the crap audio. Still working on a better mic setup.

I'm hitting higher speeds on the straights which means I am coming out of the corners quicker.

 

uhhhhhh whaaaatt????????

Did you guys put yours in backwards????????




It shines in an HR and VHR and can also in a DE.. but you need to raise your rev limit.

You're taking away top speed and winding your Z out much faster, regardless of gear, dig or roll.
Z's stock gears are way too long imho.. 200+mph!?!?! That's why you feel the pull in 4th that you don't quite "feel" with the 4.08.. because you're already there in the 4.08.



stock HR-Z vs stock HR-Z with gears OR DE-Z vs DE-Z with gears and rev limit raised..

-to 60mph = Geared Z win
-to 80mph = Geared Z win
-to 100mph = Geared Z win
-to 120mph = Geared Z win
-to 140mph = Geared Z win
-to 160mph = Geared Z win
-to 180mph = Geared Z win
-to 200mph = Stock Z win - but the other Geared Z passed you and started slowing down before you caught up to him to beat him @ 200mph. (You just have a higher top speed)


Let me rephrase this whole thing for you guys.... seems like a lot of confusion.

If you want to race a Bugatti and top speed is your goal.. stay stock or get like a 3.3fd.
If you want to get there faster while sacrificing top speed, a 4.08 gear is for you.

~180mph should be plenty fast for any of us regardless of being on the street, track or dragstrip.



oh, get the 4.08 and an OSGiken LSD ...not just the quaife...

just my

 

^^^
This scenario assumes you are launching from zero to whatever. That's correct if it's a dragstrip, but there are more variables on a track (or even racing from a roll), such as number of shifts and the powerband.

 

^^^

 

That's a huge improvment

Does this better laptime caused only by the gear or also improved driving ?

Do you feel this laptime was possible with your old 3.5 FD ?

Moreover, is this better time caused by the 4.08 or by the new diff (i assume that you added a Quaife or Osjiken in top of your 4.08) ?

Thanks.

Personnaly i still have to stock VSLD which quite sucks... Perhaps i should have taken a 1.5 Way LSD alongside with my 4.08...

 

I posted this link on a drag post I made recently. Me running a 5AT, these numbers just don't seem right. Don't know if it'll help you guys figure this out or not, but it might help. The link has my 5AT gear numbers plugged in, so you'll need to swap in your MT gear ratios and tire size.

http://www.dragtimes.com/gear-ratio-...tton=Calculate

I used this to see my MPH per gear because I'm thinking if going to a 3.69/"3.7" FD and new LSD. And going from a 3.3 to a 3.7, my top speed dropped from 186.64-167.98.

Since I shift right at peak power for me (6200) and I run an 1/8 drag strip, I'm topping 3rd right as I get to the line. So comparing mph for 1st-3rd here are my mph lost per gear: 1st -3 MPH, 2nd -5 MPH, and 3rd -9 MPH.

 

This thread is about track laptimes and the conclusion is that improvement (or lack of) from the 4.08 final drive is course dependent.

Why are people chiming in with drag racing results? It's not like you stop at every corner then go again from zero.

 

Because 'MURICA, we ain't got none them fancy drag ways with them corners in such.

I was just trying to provide info on figuring out MPH per gear, which is what somebody doing any sort of racing might need to know, IMO. That way you almost know what your MPH is in your powerband of each gear. So what was once your choice of gear for a turn may change, because a lower or higher gear is more or less in your powerband.

 

I think it's a combination of all. I did have to learn the whole new gear ratio and the new shifting. I found I was accidentally shifting from 5th to 6th when I was supposed to be down shifting to 4th on the long right hand corner. Nothing worse than blowing a lap because you downshift to 6th! After half the day I was getting into the zone so I actually think I can do a lot better next time as I'm learning the new gears.

As for the 3.5 - yes I believe that time is achievable with better driving. If you could manage to get through the corner at a higher RPM you could utilize the power in the 3.5. For me though now with the 4.08s, when I get through the corner, 3rd gear is ready to rock no matter what.

Yes I added a Quaife LSD. I am not sure that I am utilizing it yet though because I'm not pushing the car to it's traction breaking limits. It will definitely come in handy though when I do. To put it in perspective I've seen a 350 DE with a BBK, semi-slicks, and a few bolt ons do 1:22 times... 5 seconds faster than me so there's a lot of room to improve.

 

Awesome Thread! I am not an HR but I do run 4.08s/Quaife on my DE with full bolts and 14lb flywheel.