JHM Gear Ratio Change kits for better fuel economy in 6th. Gauging interest?????

[jaybquick@JHM]

Hey guys wanted to see what kind of interest there is in higher gears for 6th to get better fuel economy. I doubt many people are racing in 6th gear and I know I generally skip 5th since 4th and 6th are close enough. I haven' fully tested it yet, but I can't see why it won't help fuel economy.

6th gear is made up of 2 parts and is in the rear, only 15% of the trans needs to be dissasembled. It comes off with a 2 jaw puller once the center diff is out and the rear case is off. (my Rebuild DVD would probably be offered with this as well)

Pricing on the set of 2 gears in those ratios would probably be in the $600 or $800 range. Haven't finalized pricing yet, just getting a feeler of interest to see if I should pursue this further. These are available to me now, just takes 2 to 4 weeks until I decide to go full force and stock them. Email me if you are interested now at [email protected] .


THE TECH STUFF

Our trannys have the following ratio for 6th. 0.68

I can get .56, .58 or .60 for 6th

Right now you should be at 3000 rpm at 80.


With the new ratios you would see the following RPM.

2450 rpm with .56 6th, 2550 rpm with .58 6th or 2650 rpm with .60 6th


Just to give you a reference the 5th gear ratio in our trannys is .81 yielding 3600 rpm at 80 mph. I can get other ratios for this as well but I would think this is still a usable gear since at 7000 rpm it should reach 155mph in 5th which should be more than enough for normal humans.


Thanks guys I would love to hear feedback and interest.


ACTUAL PRICING 4-07-08

I couldn't locate the .58 ratio but could locate the .60 and .56 For whatever reason one of the two gears for the .56 was pricey. Probably best to just have two options anyways since the .58 would just be in the middle of the 2.

.60 OD - 350 rpm drop at about 80 mph - JHM Price $650

.56 OD - 550 rpm drop at about 80mph - JHM Price $775 (one of the 2 gears was very pricey I will continue to shop around)



The math based on those prices
Lets do this based on an fuel economy average of 23 mpg (368 miles to a tank) I know many can do better, just being conservative.

So if the car increased 3 mpg (think more is very possible on a long trip) on the freeway you could get 416 miles to the tank. So that would be 48 miles more to the tank. Split that in half and you get 24 miles. So lets just say you get the use of 2 more gallons of gas per tank. Right now 91 octane in my area costs $3.99, but I will go with a more modest $3.50. So that is $7 savings per tank on the conservative side. So that would take 110 tank fulls on the .56 gear if it only increased by 3 mpg. And 92 tank fulls on the .60 gear ratio kit. I think if someone used 6th at lower speeds around town at about 45 mph they could save a ton. If you gas up all the way twice a week, it only takes a year to pay for itself (this is normal for commuters)


I think I need to get these gears in a car and get the real MPG gain to do the math on. But those are some numbers to chew on and get some people thinking.

[The_Jerbel]

It will increase the possible top speed in 6th too

[jaybquick@JHM]

It will increase the possible top speed in 6th too

yup in 6th gear at 7000 rpm here is what is possible, baring you have the HP.



186mph with stock .68 6th gear.
211mph with .60 6th gear.
218mph with .58 6th gear.
226mph with .56 6th gear.


Kind of scary. [O_O]

[2ndEngineS4]

Woo hoo. 226 here I come!

[k0mpresd]

what do you run in your car?

considering there are qty 2 3rd, qty 3 4th, qty 3 5th,, and qty 3 6th gears available.

just curious

[mike-2ptzero]

yup in 6th gear at 7000 rpm here is what is possible, baring you have the HP.



186mph with stock .68 6th gear.
211mph with .60 6th gear.
218mph with .58 6th gear.
226mph with .56 6th gear.


Kind of scary. [O_O]

Just think of what it would be if you have a 8500 rpm rev limter

[nocturnals4]

Im in, I do a lot of hwy driving.

[thebigchu]

Nice Jay! I was wondering about this! I really hate that the only answer to "How do I get better fuel economy?" is "Don't drive so g*dd@mned fast!"

85 is the flow of traffic around here... and @ about 77 is where the fuel economy really seems to fall off in 6th.

[sweed]

What would be the guestimate MPG at 65, 70 and 80 mph? any ideas?

[jaybquick@JHM]

Woo hoo. 226 here I come!

HAHA. I will look for that on the news, once you hit one of the pot holes in our classy highways.

what do you run in your car?

considering there are qty 2 3rd, qty 3 4th, qty 3 5th,, and qty 3 6th gears available.

just curious

My car has all stock ratios with 120k on the original gears. I don't do highway usually for more than 10 miles that often anymore. My business and home are in the same town and my Fiances work is only 10 miles away when she has the car. However next time I have the trans out I will be wanting to put them in and give it a go.

Just think of what it would be if you have a 8500 rpm rev limter

Since you mentioned it if you had the HP, here are the numbers. I don't think the car would be very stable though. HAHA. Understatement of the century.

226mph with stock .68 6th gear.
256mph with .60 6th gear.
265mph with .58 6th gear.
274mph with .56 6th gear.

Im in, I do a lot of hwy driving.

Cool I will start working on finalized pricing and nail down my sources.

Nice Jay! I was wondering about this! I really hate that the only answer to "How do I get better fuel economy?" is "Don't drive so g*dd@mned fast!"

85 is the flow of traffic around here... and @ about 77 is where the fuel economy really seems to fall off in 6th.

My philosophy is simple. For every problem there is a solution. Well, most of the time. HAHA

What would be the guestimate MPG at 65, 70 and 80 mph? any ideas?

Hmm. I would expect between 2 and 4 MPG being possible depending on speed. If you drive a lot of highway that adds up fast. I actually have a frien locally who drives 80 miles round trip for a commute to school. So i am asking him to pay attention to his current fuel mileage. I will most likely use his car as a test car when we do his clutch and see what kind of data he returns.

[quicksilver_S]

A lot of B6S4 owners would get in on this. The 6th gear ratio sucks on those cars. Waste so much gas while cruising on the highway.

You should extend our offer to them

[jaybquick@JHM]

A lot of B6S4 owners would get in on this. The 6th gear ratio sucks on those cars. Waste so much gas while cruising on the highway.

You should extend our offer to them

Did already. They contacted me and nobody bit on it. Never did an official feeler though. I think the labor costs scare people away, this is probably something a DYIer could do with my trans rebuild video as a helper. Just use the beginning and the end only.

Here is where I talked about this there->http://www.audizine.com/forum/showthread.php?t=181719

[Kruat]

I'd be down also, I drive 25 miles one way to work. I've been getting 24mpg-26mpg @ about 55-65mph (traffic)

[okkim]

Are these OEM gears? I might also be interested.

[diaftia]

This would be awesome! This is why Corvettes get in the high 20's on the freeway. At 60 those things are at like 1700rpm. Granted its a bigger V8 with more TQ. But I have always thought that these cars (and most cars) tach high at freeway speeds.

Would this be a type of thing that we have to send out transmission back to you and you swap these gears out or what? Most of the members on this board would not venture into a transmission other than to remove it from the car. ;)

[AudiSportB5S4]

right now im putting 60 highway miles a day going to school. its kind of nice actually, i miss traffic both ways so my car has a real solid ride there and back, 9/10 mornings depending on what assholes are out i usually get on the highway shift into 6th then dont have to shift out of it until 30 miles later! right now on stage 3- since my stock injectors are getting raped i get 18 MPG highway! so i would be interested! i actually told my dad the reason im doing fueling on the car in a month is so i get better gas mileage with bigger injectors :-p. LOL

[mike-2ptzero]

This would be awesome! This is why Corvettes get in the high 20's on the freeway. At 60 those things are at like 1700rpm. Granted its a bigger V8 with more TQ. But I have always thought that these cars (and most cars) tach high at freeway speeds.

Would this be a type of thing that we have to send out transmission back to you and you swap these gears out or what? Most of the members on this board would not venture into a transmission other than to remove it from the car. ;)

Well you also have to remember that a V8 is spinning 2 more cylinders so it needs to run at a much lower rpm. If all the cars are running the same speed a V8 spinning at 1700 rpm is equal to a 4 cylinder spinning at 3400 and a V6 spinning at 2550 rpm, unless the V8 has DOD (displacment on demand). This is exactly why a 4 cylinder car even while running at very high rpms will still get better gas mileage.

[FrimmelNoJerz]

doesnt do much for me but thats a damn cool idea.

[lil' is 300]

How about a longer first gear? I hate how short it is...

[okkim]

You have to change the whole axel to change different first gear, because it is straight in it.

[my2000APB]

How about a longer first gear? I hate how short it is...

2nd that bigtime, i wanna go to 40 at stock redline, 45-48mph at 8kish

[Das General]

longer first, longer last...that would be nice.

226 mph would be sweet. 200mph club here we come..!

[Matt@JHM]

Looks like enough interest Jay, now order one so I can test it out

[infinkc]

how about a fuel savings chip that can be dual loaded like stock/valet/race or even an e85 chip.

[GURUMAN]

Yess sir, now whe can catch veyrons

[slow ride]

The only problem with a longer 1st is the added stress it puts on the clutch during a slip style launch. If you don't launch the car hard often it wouldn't be a big deal.

[anaxagoras]

I would definitely be down, that's one of the things about the car that bothers me the short 6th gear.

[jaybquick@JHM]

I'd be down also, I drive 25 miles one way to work. I've been getting 24mpg-26mpg @ about 55-65mph (traffic)

Good to know. Thanks

Are these OEM gears? I might also be interested.

Yes, OEM gears

This would be awesome! This is why Corvettes get in the high 20's on the freeway. At 60 those things are at like 1700rpm. Granted its a bigger V8 with more TQ. But I have always thought that these cars (and most cars) tach high at freeway speeds.

Would this be a type of thing that we have to send out transmission back to you and you swap these gears out or what? Most of the members on this board would not venture into a transmission other than to remove it from the car. ;)

Looks like you live nearby near where I grew up. I am just south of Stockton. So you could just come on over for something like thi.

They could send it me for this ($350 - $400 shipping round trip), but this most likely will be a good mod to do when doing a clutch upgrade or trans rebuild to save on labor. A really good tech with a lift could do it in the car even. But with my DVD any decent tech should be able to just take the rear off the trans and swap out the last 2 gears.

right now im putting 60 highway miles a day going to school. its kind of nice actually, i miss traffic both ways so my car has a real solid ride there and back, 9/10 mornings depending on what assholes are out i usually get on the highway shift into 6th then dont have to shift out of it until 30 miles later! right now on stage 3- since my stock injectors are getting raped i get 18 MPG highway! so i would be interested! i actually told my dad the reason im doing fueling on the car in a month is so i get better gas mileage with bigger injectors :-p. LOL

Our cars go into closed loop at part throttle (like most cars since the early 80s even with computer controlled carburetors) and the ECU maintains the mixture based on the 02 sensor readindgs. Fuel economy at cruising speeds has nothing to do with injectors, turbos, or much else for that matter. Other than major head work and cam shafts. So it sounds like your 02 sensors are going south and not reading accurately. Check your car for codes first though to rule anything out.

How about a longer first gear? I hate how short it is...

That is why we raised our limit with our K04 tunes to 7350 for helping on tire spinning launches since clutch slipping is a dangerous habit to get into if you want your clutch to live.

It is part of the mainshaft on one of the sides. The mainshaft includes 1st and 2nd, so they can only be changed as pairs. The mainshafts retail for around $1,140 and the gears (you would need both 1st and 2nd) retail for around $500 each. I could probably chop a good 10% to 15% off that and package it together. This would not be a bad idea if you were redbuilding your trans and found that the 1st gear was worn in the mainshaft (most common especially when launched alot).

Our 1st and 2nd ratios are as follows.

3.50 1.89

The allroad trans has a lower 1st and 2nd.

3.75 2.05

But, I haven't seen any higher 1st and 2nd ratios. But I haven't looked hard. Generally the other trannys just have a higer final drive like 3.89 and ours has a 4.11. But that is a pain due to that affecting all gears, needing the gears in the rear end to be changed and some ECU and instrument cluster recalibration which I have never ventured into. I will look around for a higher 1st and 2nd option.

how about a fuel savings chip that can be dual loaded like stock/valet/race or even an e85 chip.

That would be called your right foot or lowering boost. Being that the car goes into closed loop you can't force it safely to run leaner than the 14.7 it is programmed to maintain. That ratio also maximizes the catalytic converter efficiency. You wouldn't want to damage your cat either.

However E85 would be fun, unfortunately there is none here publicly in Nor Cal from my research. I already looked. I found plenty stations in So Cal though.

[generationjdm]

How much will it cost after everything including labor and will the cost ever be justified in gas savings? I mean if it cost 1000 dollars and you get 2-3mpg you wouldn't see any saving unitl you filled the car up over 200+ times.. It would be worth it to see the car go over 200mph for sure...

[AudiSportB5S4]

hey Jay, check your PM's!

[Turtle]

I would love to see a B5 S4 fly by at 225 mph. and Is it just me, but our cars seem about as aerodynamic as a brick>?????


Diaftia - Your Avatar is just straight awesome. Nice.

[AB18]

There not as bad as you think,still nothing spectacular Im pretty sure the B5 chassis has a .28 of drag.

[JayyyyyC]

I would love to see a B5 S4 fly by at 225 mph. and Is it just me, but our cars seem about as aerodynamic as a brick>?????


Diaftia - Your Avatar is just straight awesome. Nice.

I actually wonder about this sometimes. Back in my MKIV Jetta, it was very quiet at mid to high speeds. Less sound dampening material than our Audis too. I hear tons of wind noise outside the car with the Audi, and wonder really how aerodynamic our cars are.

[lil' is 300]

According to Mark P's template, 200 MPH on our tranny would be (6th gear) @ 7570.2 theoretical RPMs and 8010.7 tachometer RPMs.

[The_Jerbel]

Our cars go into closed loop at part throttle (like most cars since the early 80s even with computer controlled carburetors) and the ECU maintains the mixture based on the 02 sensor readindgs. Fuel economy at cruising speeds has nothing to do with injectors, turbos, or much else for that matter. Other than major head work and cam shafts. So it sounds like your 02 sensors are going south and not reading accurately. Check your car for codes first though to rule anything out.

Well, I would venture to say that you are correct, sir, except that when the turbos spool quicker with less throttle, the IDC is necessarily increased to maintain stoich. Therefore, you will use a little more gas with bigger turbos and bigger injectors. BUT, that is only because what you said is true. The ECU will adapt, based on closed-loop inputs, to maintain stoich. Carry on

[quickglx]

I'm definately interested, right now I do ~150 miles a day mostly over 70mph..... I'd love to see another couple MPG. What rpm would 6th yeild at other speeds tho? I use sixth most of the time just putting around town- what speed is ~1500 rpm? If I'm going to change it out, likely I'd opt for the longest gear possible.

[jibberjive]

or even an e85 chip.

[VR4-S4]

really cool idea. For me i don't know if it would be worth the time and cost but definitely a great idea.

[obsess4]

I think the idea is good but $600-$800 is high.

[jaybquick@JHM]

I'm definately interested, right now I do ~150 miles a day mostly over 70mph..... I'd love to see another couple MPG. What rpm would 6th yeild at other speeds tho? I use sixth most of the time just putting around town- what speed is ~1500 rpm? If I'm going to change it out, likely I'd opt for the longest gear possible.

Here I did it with the stock .68 stock ratio and the others the MPH to the right of the RPM amount



RPM .68 .60 .58 .56

500 13 15 16 16
600 16 18 19 19
700 19 21 22 23
800 21 24 25 26
900 24 27 28 29
1000 27 30 31 32
1100 29 33 34 36
1200 32 36 37 39
1300 35 39 41 42
1400 37 42 44 45
1500 40 45 47 48
1600 43 48 50 52
1700 45 51 53 55
1800 48 54 56 58
1900 51 57 59 61
2000 53 60 62 65
2100 56 63 65 68
2200 58 66 69 71
2300 61 69 72 74
2400 64 72 75 77
2500 66 75 78 81
2600 69 78 81 84
2700 72 81 84 87
2800 74 84 87 90
2900 77 87 90 94
3000 80 90 93 97
3100 82 93 97 100
3200 85 96 100 103
3300 88 99 103 107
3400 90 102 106 110
3500 93 105 109 113
3600 96 108 112 116
3700 98 111 115 119
3800 101 114 118 123
3900 104 117 122 126
4000 106 121 125 129