Shifting WOT into OD??

**rick67** · 09-09-2009, 12:39 PM

So I'm getting ready to install meth injection, boost controller, and A/F gauge into my car and get it tuned. My parts will start arriving tomorrow.

(STS turbo car, 5PSI, all stock except injectors and 3600 stall)

My best pass so far was 12.41 and I'm trapping around 5,500 RPMS in 3rd gear.

I would hope by adding meth and cranking my boost up to 8-9 PSI I should easily be in the 11's. (not sure what my trap speed will be after adding the extra boost)

I'm considering swapping rear ends from the factory 2.73's to a 3.42 rear end I found as well.

My question.... Simple math tells me that 3.42's are about 25% steeper than 2.73's. So 5,500 RPM at the traps would now be almost 6,900 RPM assuming my MPH stays the same.

I don't want to trap that high! Can I shift into OD at the top of the track under WOT? Or should I just keep my 2.73's?

Thanks in advance for your insight!

**thearborbarber** · 09-09-2009, 02:32 PM

You will need to change the shift speeds in the tune. My 99 with 2.73 would let you shift in OD after a certain RPM. It's pretty easy change. I made the same change from 2.73 to 3.42.

**bills98ta** · 09-09-2009, 03:56 PM

Why don't you get a set of 918 valve springs, and turn up your rev limiter, at least 6800...
3.42's won't be that steep.

**bills98ta** · 09-09-2009, 04:05 PM

Oh, to the original question, I let mine hit OD after the traps, but you shouldn't hit before the traps. It's not strong enough...

**rick67** · 09-10-2009, 03:17 AM

Thanks guys. I think I'll keep my 2.73's

**Frost** · 09-10-2009, 06:52 AM

Keep the 2.73s. They are turbo friendly (especially for a rear mount that NEEDS the load to get them spooled). It seems counter intuitive if you have never run a turbo setup, but trust me

If you want better 60's (all you get from gears anyway) leave under boost.

**Qwk Vet** · 09-17-2009, 09:16 AM

I would never hit OD at WOT but that's me!

**Frost** · 09-17-2009, 10:14 AM

Originally Posted by Qwk Vet

I would never hit OD at WOT but that's me!

I don't allow it in the cars that I tune.

**Qwk Vet** · 09-17-2009, 06:41 PM

Originally Posted by Frost

I don't allow it in the cars that I tune.

OD not that strong when u throw some power at it!

**KMdef9** · 09-17-2009, 08:51 PM

I may be alittle green to this, but im only assuming he has an A4. You shouldn't go into 5th for drag racing w.a M6? Ideally top of 4 as you cross the line?

**sutie** · 09-29-2009, 08:46 AM

so when racing, leave the selector in 3rd the whole way through? not push up to D.?

**Frost** · 09-29-2009, 11:31 AM

Originally Posted by sutie

so when racing, leave the selector in 3rd the whole way through? not push up to D.?

I'm talk about tuning, not technique. Leave your car in OD to race though.

**sutie** · 09-29-2009, 11:41 AM

i allways thought that starting in third was the strongest with the A4's. so is this a myth?

**bills98ta** · 09-29-2009, 02:25 PM

With my A4, the computer does the shifting best when I leave it in OD. You want the shift points programmed so it holds 3'rd ( drive ) through the finish line in the 1/4 mile, even though the shifter is in OD...