stock rpm vs speed for a 93 jetta

[lurchzuki]

Hi All,

New to the forum so forgive me if this has already been beat to death...

I have repowered my 92 Suzuki Sidekick with an AAZ out of a 93 Jetta.

My RPM seems quite high... 4th gear (1.00) is giving me 2100 at 30MPH. Is this even remotely close to what the engine would be geared in a Jetta/ Golf? From a stop 1st gear gets me about 15 feet and in my opinion the engine is ready to shift. By the time I get to the otherside of the intersection I'm just about ready to hit 3rd. Power is not a problem... can pull a 14% grade with two very sharp corners in 4th gear and accelerate up it.

What would the stock Jetta manual trann,/ ring and pinion, and stock tire size have been....hoping I can find ratios to do some math and figure out what gears and tire size I need to get back to into theRPM range the engine was designed for.

Any insight you guys can provide will be greatly appreciated

[wolf_walker]

There is, somewhere, a calculator with trans codes and such. I'll see if I can find it tomorrow.

Sent from my SCH-I535 using Tapatalk 2

[wolf_walker]

http://www.techtonicstuning.com/TransRatios.html

http://www.richmondgear.com/101032.html

I think between these two you can see what the stock RPM's were.

With the AGS diesel 5spd and stock 13" tires at 1:1 no OD @30mph is showing 1753rpm.
That isn't a valid scenario for the stock setup but it's telling.
5th gear @60mph is 2630rpm for reference.
15mph in 1st is 3Krpm, so we shift out of first half way through an intersection too.

You can pop the numbers around and see how they come out, the stock 13" tire is about 22.6" tall.

[lurchzuki]

Thanks for the links!! I'll play with them tonight and see what I come up with.

[CrazyAndy]

There's also scirocco.org/gears if you want to calculate the rpms based on speed and tire size after you find out the stock ratios and tire sizes for that year.  It's a great site also if you know your tire sizes and gear ratios already in order to determine your rpms at a certain speed.

[Jetmugg]

What is the ring and pinion ratio in the Sidekick?  That's probably going to be the limiting factor in the drive-ablity of the vehicle.

Steve.

[lurchzuki]

Thanks for the link Crazy!

Jet,

Currently it has 5.125s in it, i also have a set of 4.62s.
I can go up 2 -3" on tire size to to help me out as well. I'm really not counting on being able to match up exactly what ratios would be in the Jetta. Just will be nice to have a goal to shoot for...

I love the amount of power I have right now in a given gear compared to the old gasser it used to have. But I really don't need to be able to accelerate up a 14% grade in 4th Just sort of thinking if I can flatten out overall gear ratio by manipulating R/P tire size I may be able to increase economy a bit more.

[JamesT]

To match final drives of a stock Jetta (3.67) on stock tires (23.5" diameter), you would need 33" tires with a 5.125 final drive. That's assuming your gearing is close to the VW gears, which it looks as though it is except it gets a little shorter in higher gears.

The 4.62 gears would probably work better, as 29.5" diameter tires give you the same final drive as a stock Jetta, and 31.4" will give you the same overall in 5th as a VW with .75 gearing if you have an earlier Sammy 5-speed.

[CrazyAndy]

You should throw some pics up when you have this all hashed out and done; folks love to drop AAZs in their Suzukis around here it seems.

[bajacalal]

Before you start worrying though, these were designed as high-rpm engines.

[wolf_walker]

Yep.  Isn't going to explode. 
But your fuel mileage will suffer if you are beyond the expected steady state RPM/load they designed them for.
Even a little Rabbit will drop 3-5mpg going from 60 to 70mph unless it's got a tall 5th.  There was just the other day a kid on Vortex experimenting with this
and pondering safe cruising speed for an old NA motor.

[CrazyAndy]

Yep.  Isn't going to explode. 
But your fuel mileage will suffer if you are beyond the expected steady state RPM/load they designed them for.
Even a little Rabbit will drop 3-5mpg going from 60 to 70mph unless it's got a tall 5th.  There was just the other day a kid on Vortex experimenting with this
and pondering safe cruising speed for an old NA motor.

Links?  Would actually like to see the data regarding this; my calculations for myself put me from 2600-2800 @ 70 depending on my wheel choice.

[TylerDurden]

3-5mpg less from going 70mph vs. 60mph?... Simple aero losses: drag increases to the square of speed.

FWIW, my 85/86 TD cruises 62mph @ 3000rpm. AGS tranny. I believe the speedo is correct, but I need a stopwatch to validate. (no sweep hand on clock).

[wolf_walker]

Yonder..  http://forums.vwvortex.com/showthread.php?6017962-a-quick-question-regarding-1.5-Diesel-on-modern-highway&p=81573275#post81573275  Hardly scientific but it sounds pretty average from my experience.

I have very little faith in stock tach's or speedo's without verifying em.

[JamesT]

Interesting thread, but hardly scientific.
I like that someone claims that it's impossible for a 1.5N/A to do 80Mi/h just because their 1.6TD is reluctant to.
I think that's called vortex logic.