I have a 2000 A4 with a 2800 TC and a IC Magnacharger. My tuner
set the shift points at 6100 and I wanted them set at 6500 but he
sez that it will not buy me anything at the drags and I disagree before
I had the blower my car went faster everytime I raised the shift points. I have the CC RPM kit so valve float is not an issue. Is there any valid reason not to raise the shift points at track with my combination ?

Thanks >>>>> INTHERED

 

In a 1-2 shift for example when

flywheel torque @ shift pt. rpm x 1st gear ratio
= flywheel torque @ shift recovery rpm x 2nd gear ratio

The same argument goes for later upshifts.

What you'll discover is the following:

1.) On the Magnacharged (and most LSx) setup, you can't shift high enough w/o hurting the engine or accessories as the wheel torque in lower gears is always > wheel torque in the next high gear after shift. Hence you should shift as high as your valvetrain limits and risk tolerance.

2.) Seasoned drag racers like to shift 10-15% above peak power rpms. Hence Z06 guys that have 6k rpm peak pwr. like to shift at 6600 rpms. Or LS1 stockers that make peak pwr. @ 5200 rpms (you sure don't shift your A4 at 5200 rpms when stock to get best times) get best times at 5800-6100 rpms. The torque curve in Mag. setup holds up more nicely than a stock LS1 which is more incentive to hold the gears longer.

3.) This is why some setups that peg peak power at the fuel cut rpm (and IF the fuel cut rpm cannot be raised any higher for certain reasons) can never fully exploit the power curve and contribute toward a "dyno queen" timeslip.

Alas, the beauty of the Mag., any PD blower, moderately cammed 427s, quick-spool turbos is that those setups are forgiving to premature shifts (and wider ratio spreads) than other setups. The SC'd AMG MB cars don't follow those 10-15% peak power rules since the penalty in performance is so small to the gains in longevity. Although many tuners in the first thing raise shiftpoints to better trace that torque x gearing sweep. You've seen guys with quick-spool turbos that shift 1k rpms too early, still pull hard even in the next gear initially.

'gmf's' Mag. C5 A4 ran 10.9s @ 124.1 mph on 6100-6300 rpm shifts. His smog-legal, 10-second ride valvetrain will last very long!

 

 

I really doubt that GMFs A4 was shifting at 6100 on a 10.9 run.
Just my two cents though.

 

He actually told me and I have his scans during the runs he made somewhere. He and I've discussed about him about raising shifts to 6500 rpms.

It's easy to tell how to optimise shiftpoints. Tap your car and find out where the car really shifts in rpm and where the rpm values drop. Then go back and backcalculate your torque curve to the flywheel with the 80% rule. The take the est. flywheel torque and multiply it by the transmission ratios (you can multiply rear end ratio, but I don't think it makes a difference in the shift point determination since the car has the same diff ratio regardless of gear). Do this for each gear over the dyno'd rpm range.

You'll see the drop in axle torque (not flywheel) is bigger with 6100 rpms vs. 6500 rpm shiftpoints. You want to minimize torque drops during each shift obviously; ideally you want no torque drop but practically all aftermarket C5s make this impossible. Edit: In other words, for example, even at 6500 rpms where the torque has dropped off some, it's still much higher at the wheel due to the much higher 1st gear ratio than in 2nd gear with it's much lower ratio but only modestly higher flywheel torque.

This is no theoretical mumbo jumbo. It's simply your dyno results (that's real world stuff) and using your gear ratio info (also truthful stuff).

I have tons of real world examples. Wide powerband medium-small single turbo upgraded Supras that peak power ~6-6.3k rpms do so much better with 7700 rpm or so shiftpoints than 6800 rpm shiftpoints. So we're talking about shifting maybe 1500 rpms above peak power rpms...and that's with a close ratio 6-speed! Now if your wider ratio spread A4 Mag. C5 is making peak power at around 6k rpms or a bit higher, you know that a 6100 rpm shiftpoint is nowhere near the 10-15% above peak power rpms (it just happens to be so on most cars) requirement; although mechanical limitations make it tough to go by that rule.

Shifting at 6100 rpms on your Mag. setup is right around peak power rpms. That's like shifting at 5200 rpms (stock LS1s [peak at 5200 rpms) when your car was stock...and we know you can't cut a good slip with that. Plus the Mag. setup holds the torque curve nice and high (and doesn't drop off like a stocker) giving more incentive to hold the gears longer. Wider ratio spread or torque curve that doesn't drop off sharply are all factors compatible with holding the gears longer.

I mentioned tuners raising shiftpoints on SC'd AMG MB because they shift at their power peak rpms. The GM 3800SC guys also know that the cars shift too prematurely (if I recall correctly 5400 rpm peak power rpms, 5400-5700 rpm shifts depending on car/year, but tuners take shifts to around 6000 rpms), which is ~10-15% above peak power rpms.

The '00-'01 Maximas (and current Q45s) are called dyno queens because their track numbers don't support the perception of peak power ratings and weight; a 222 hp Maxima A4 put up same numbers as a '00-'01 A4 Accord or Camry with 200 and 194 hp. That's because those cars have peak power rpms within 100 or so from the redline (6400 rpm peak power / 6500 rpm redline)...thereby making full use of the top of the power curve tough while the Accord and Camry had ample space to the rev ceiling. But the '02+ Maximas picked up tremendously and much more than what the modest output bump would've suggested. This due to a lowering of the peak power rpm to 5800 while keeping the 6500 rpm redline same; making the 10-15% rule doable.

PM me your email and I'll email you a cool shiftpoint determination tutorial. There's so much to say about this.

In the end don't expect too much gain with this thanks to the forgiving powerband of PD blowers that you have; and hence your times with 6500 rpm shifts in warm weather would still be worse than your times with 6100 rpm shifts/cool&crisp air.

There's no doubt in my mind that a 6500 rpm shiftpoint would be a benefit. You'd have to have a torque curve drop off steeply enough such that your peak power rpm is around 5400 rpms to make 6100 rpm shifts sensible (note higher gear shifts don't require as higher shift rpms due to progressively closer spacing). The real question is if one is a wild driver, how much that would harm longevity.

Sorry for the long post.

 

I forgot 6500 rpm shift/6700 rpm fuel cut sounds good only with stronger valvesprings. With stock valvesprings 6100 rpms sounds like a good limit.

 

I have the Comp Cams RPM kit which consists of springs, pushrods and titanium retainers. I would like to shift at 6500 with a 6600 fuel cut off do you think 6500 is too close to the fuel cut off for strip use.

Thanks >>>>> INTHERED

 

If your dyno sheet shows you pulling past 6200 then 6500 shifts should be alright.

 

I'd put the fuel cut at 6700 rpms. That way as your trans. ages, you have a bit more cushion (sometimes old slippy trans. makes the engine revs flare in between gears).

In summary, 440-460 rwhp bolt-on modded '03+ Cobras trap 117-121 mph in low DA/favorable air thanks to shifts at least a few and sometimes more than a few (with custom rev limit adjustment) hundred rpms above peak power rpms. But those guys weigh 3665 lbs. W/O DRIVER.

That means a 3350-3450 lb. Magnacharged C5 making 440-460 rwhp (and likely much more aerodynamic) better not even be in that same 117-121 mph window but a good bit higher so long as the shift points are appropriately set.

 

If your trans is slipping you should get it fixed. Not detuned in the PCM.

 

I have a new 3.42 rear, a new Rossler trans and a new Yank 2800

 

My peak power starts at ~438 rwhp @ 6400 rpm and ends at
440 rwhp @ 6600 rpm where the fuel cutoff kicks in. But the
curve has some small 4-5 hp dips in it between 6400 & 6600.
At 6200 rpm Iam below 430 rwhp so it makes sense to me to
shift at 6500 I guess.

 

Have you tried experimenting at the track? How does it run at the track right now? Try shifting it manually at the track next time you go and see what your time slips say. Remember, you can't race dynos, the track will tell!

Jersey

 

It sure does. If power is climbing then by all means go as high as you & car can tolerate. Unless the PCM program is unstable from KR or if the dyno plot is bogus from another car and not yours (the latter we should rule out), the stuff I sent and discussed above should translate directly to the track. It's no abstract theoretical gibber-gabber. It's just mechanical advantage (or leverage) over speed; just like one deosn't need to think twice that applying a force on a longer wrench = more torque than same force on smaller wrench. Only thing is not to compare apples to oranges track and weather conditions when experimenting with shiftpts...that might lead one to wrong conclusions.

 

If he tries to manually shift above the automatic shift points at the track the car will do what most with "tiptronic" transmisions do -- shift automatically at the program's desired shift point.

I see tuners overanalyze this a lot. It's really based on the car's potential as depicted on a dyno. If it pulls to 6500 and drops past that, I'd set the shift points to, say 6700 and be done with it. Adjust the rev limiter to 6900 so TCC slippage won't come into play.

Track conditions that are less than favorable will not make for the best ET's anyway so adjusting this for each track/track condition is pretty useless.

 

What did the scan tool show, while on the dyno, about that dip between 6400-6600? Someone, DID have a scan tool hooked up for the runs, right?

 

In this case I agree. No analysis needed. If power continues to climb until rev cut, the set the shifts 100-200 rpms below rev cut.

In situations where there's a big difference in peak power rpms and rev limit (not that common these days), the engineers plot out thrust (flywheel torque x gearing / rolling radius) vs. speed curves and set shifts at where the curves between two consecutive gears intersect; it usually ends up being 8-15% above peak power rpms. But like I said, this idealogy comes only after other constraints like durability are satisfied (e.g., the honest 1-2 ideal shift on a Mag. setup peaking power at 6600 rpms would be 7000+ rpms, but there's no way that's feasible due to mechanical issues).

 

In all cases of these particular cars there's no more analysis required. Shifts are set 1-200 rpm above the peak Hp reading off the chassis dyno graph -- DONE!

The main reason being that you want to stay in the peak Hp curve through the shifts as much as possible and the only way to do that is to shift above the peak so that when you shift into the next gear you drop as close to the peak Hp value as possible. The same goes for manual cars as well. Put the calculator away.

 

You put it very succinctly well!

 

If you are revving above 6500rpm I hope you have a good set of rod bolts in the car