Originally Posted by jlashley2001ss
What can i do to "pick up" the poor accel. from 30-50mph range on an A4. As you can see below i already have an SY3500 tc and ive had my shift pts. bumped up all the way through and Torque Management deleted. What else can I do to get better in this range? TIA guys.
This is all about gearing and IMO 3.23 is one of the worst setups for A4 Fbody's.
Sure from a dig the 3.23's are ok if you go to WOT straight off but from a roll they leave a great big dead spot.
30mph I would have thought was ok, but maybe 33-35mph area would be the start of the dead spot.
30mph in 1st is 3900rpm and I would have thought it would kick down to that from a roll. 35mph however is 4500rpm which it probably wouldn't shift down to as standard which means 2nd gear is all you are going to get at that speed, but that equates to 2400rpm which is why the accelaration is pretty flat.
the same goes for 50mph, that would be the red line in 1st so when you floor it the gearbox will only kick down to 2nd gear, but it would still only be at 3400rpm hence it still won't feel as fast as it should.
If you want to roll race with 3.23's then 25-30mph is probably a pretty good low speed start and 60-65mph for a higher speed roll, anywhere in between will be a flat spot for the gearing. How can you get around it?
Well there's several answers. If yuo have a good bolt on cammed car then you can increase you shift points, kickdown points and red line to give a greater terminal speed in gear and more flexability.
Stock the A4's shift at 5850rpm hence it won't kick down to anything above 4400rpm because the duration in gear would be too short, but increasing the shift point to say 6300rpm would mean you could allow it to kick down at much higher speeds.
Evidently you need a cam appropriate for this setup though and it does make for quite an aggressive style of driving and shifting.
Changing your final drive ratio is your other option.
Strangly enough 2.73 geared cars don't suffer this same flat spot. This is due to the fact that they can achieve higher terminal speeds in gear. They will kick down to 1st from speeds upto 39-40mph which will actually bring you in right at PEAK torque of 4400rpm. This makes then good for low speed roll races. 50mph is a dead spot because it won't kick down to 1st only 2nd gear which is only 2900rpm. So you can see the flat spot still exists just at different speeds (typically speeds which are not as common for roll racing).
However due to the taller gearing of 2.73's the in gear accelaration will be less, hence from a dig a 3.23 car should be the faster. But from a 35-40mph roll with stock cars the 2.73 geared car would pull ahead and probably maintain the lead until 100mph at least.
So the next step is to lower the final drive ratio (numerically increase). Common gears are 3.42, 3.73 and 4.10
Now all of these will increase your crusing rpm which will affect mpg. But they will also lower your terminal speed in gear which can be an issue if you typically run to higher speeds.
Before you choose on gears however it's worth considering a few factors.
First off these 4l60e gearboxes are really only 3 speed with an Over Drive and not 4 speed boxes. This means that for WOT kick downs you really should have the box in D (3rd) and not OD (4th). This is less damaging and also the gearbox will react quicker.
This means your top speed will be limited to your red line in 3rd.
Assuming stock limiter this would mean with:
2.73 = 158mph @ 5650rpm (which is actually the speed limiter not rpm limiter)
3.23 = 142mph @ 6000rpm
3.42 = 134mph @ 6000rpm
3.73 = 123mph @ 6000rpm
4.10 = 112mph @ 6000rpm
As you can see 4.10 gears severely limit your high speed ability and if you regulary top 140mph then only 2.73's & 3.23's will be able to achieve this.
Ways around this are to increase you rpm limter and shift points, but without a suitable cam setup you may not benefit from this.
Run larger tyres, but this will offset the point of running lower final drive gears (N.B. Remember numerically higher means lower gearing
So it's all about deciding what the car is used for. At the 1/4 mile 4.10's or 3.73's on the correct setup will work very well, but for me I often want to blast up to 120-140mph even often up to the 158mph limiter so such gears would be of no use to me.
If I go n/a cammed setup I'm getting 3.42's as with an increased rpm limit to 6500rpm I should still lbe able to top 140-145mph while still mainting acceptable low rpm accelaration due to the more agressive cam setup.
My preferred setup however would be FI in which case I would go for 3.08 final dirve ratio (this is only availble with aftermarket 12 bolt rears, not the stock 10 bolt) as they would allow easy 150mph ability. But then again I don't spend every weekend at the track, my car is mostly a road going machine so a broad range of abilities are much preferred, this isn't the case for everyone so pic wisely. Tips:
-Use D instead of OD for improved gearbox response
-Only roll race from speeds which suit your setup
-Match gears, cam and other mods for intended use
In my sig there's a link to a gear calculator so you can see what different final drive ratio's and rpm limters can acheive terminal speed wise.
Hope this helped