asinow

What's the best way to run they RCF?

Do I keep it in auto mode, keep it floored and trust the car will shift or manual and I do the shifting?

Going Tuesday 4/17 and will share results

Thanks...

LXSDO

You would want to shift manually. Pretty sure it'll shift before redline and may shift prematurely. That would be my guess.

rjmalm

Frame by frame shows the shift at 7.05k if in manual. Did not video Sport+

Image attached.

I did run expert and you can see traction control involvement at lower RPM.

Watch the traction light come on about 5-6k and at 7k shift point.

mirza

Im going to try testing it with an obd2 dongle and torque app. I finally found it

TruPlaya26

iTrader: (4)

The method I've used to get the best run is Launching in Manual (in Sport +), and after shifting into 2nd I pop it back into automatic and let it do it's work from there.

RCFormante

iTrader: (1)

From my experience, auto mode shifts way too early, auto shifts at 98 mph in 3rd, while manual you can shift at 104 mph, its going to affect your 1/4.

DougHII

Red line not always optimal shifting point. The up shift at 98 from third to fourth may actually be the optimal shift point.

Just as the what exhaust makes the most hp focus is misplaced, the key in both is your torque and shifting at those points that maximize the area under the torque curve. A crude and oversimplied explanation is that you shift where torque achieved for the upshift gear will be the same as the torque of your current gear. If you go past that point, you are losing time.

It is possible that depending upon the shape of your torque curve you may never reach the point wherein torque for the upshift gear matches the torque in the current gear so you would take it to redline. I find that rather unlikely in the RCF with 8 gears and with your peak torque being around 5,000 based on the dyno you posted in the exhaust section . . . although yours was not very linear so the calculations may be a bit funky.

You should be able to find calculators to determine optimal shif points with hearing data and a dyno chart.

Aron9000

Also leave the traction control off on the strip. The engine is cutting timing, possibly hitting the rear brakes and doing all kinds of non-sense that is going to screw with your time. If the track is well prepped, its WAY stickier than the street. You might have to pedal it out of the hole so to speak to keep it from spinning.

Best way I've found to launch an automatic transmission car is to put your left foot hard on the brake, put your foot on the gas and get the revs up a bit, inch forward to trip the beams by letting your left foot off the brake slightly, then when the light turns green you let your left foot off the brake while rolling onto the throttle. Key is to figure out how many revs to hold the car at and how fast you can get the car to wide open throttle without losing traction. Practice on the street before you go, I bet by about 3-4 trips down the strip you'll have it figured out and be cutting 2.0 60' times or better.

RCFormante

iTrader: (1)

If left in auto mode, the transmission will not have the direct shift that it does in manual mode. When it is in manual mode, the torque converter locks up from 2nd gear and up allowing very fast shifts giving you that quicker time, shifting right after the beep.

The guys with the ISF, which has the same block and transmission as ours, gets the best 1/4 mi time by shifting right after the beep, which is close to redline, if not at the redline.

ISF001

As a side comment, the RC F tranny is not quite the same as the IS F. It has a specially tuned version of the eight-speed Sports Direct Shift (SPDS) transmission, which has been refined to handle higher engine speeds. The transmission control program delivers a more linear response.

We do have the same block as the IS F, but just about everything else is different: new cylinder heads, higher compression, lighter internal parts, etc.

The stock RC F loves to stretch its legs at higher speeds much more than my retired IS F did.

DougHII

I was not suggesting using auto mode, especially since you have made modifications that could change your torque and power curves. I was only pointing out that shifting at red line is not always optimal and ignores the torque curve. If you have dyno sheets for your car, you can actually accurately calculate optimal shift points for your car.

Two things: I have no idea if Lexus has dialed in tuning to correspond with or to maximize power for redline shifts (seeing peak around 5k suggest no given higher than normal redline of 7.2k); and, if they did, slapping on some bolt ons without actually tuning to tranny may result in different shift points.

The ISF may have a different curve, with different peak point and despite the belief he is at optimal, may not be shifting at the optimal point. True, many vehicles will have optimal shift points at or even above the red line, but that may not be true with high reving NA engines hitting peak torque 2.2k rpms below the red line.

Here are a few shift calculators and the last page has a whole bunch of calculators that you might find fun and useful if doing 1/4 track stuff and trying to optimize time:

http://glennmessersmith.com/shiftpt.html

http://www.welltall.com/ymc/discovery/car/shiftpt.html

http://www.allpar.com/eek/hp-vs-torque.html

Fun calculators for 1/4 mile guys:

http://www.wallaceracing.com/Calculators.htm

DougHII

BTW, these calculators demonstrate how slapping on aftermarket parts without actually tuning may not actually improve 0 - 60, 0 - 100 or 1/4 mile time even if there is a claimed or observed increase peak hp. The focus should be on maximizing torque under the curve and perhaps keeping power bands very linear. Some of the dynos posted seem anything but linear. Challenges of a locked ECU doesn't help any either.

rjmalm

DougHII, JoeZ, or any

Does any one have that calculated shift point results for RC-F with JoeZ exhaust?
Or can you point to the link for the best torque vs rpm plot for RC-F with JoeZ exhaust?
I can only find plots with HP.

I have just been guessing by sound and feel and would like to have
some targets.

Thanks

Would use these from the announcement spec
Gear Ratios
1st 4.596
2nd 2.724
3rd 1.863
4th 1.464
5th 1.231
6th 1.000
7th 0.824
8th 0.685

Not sure of the actual tire diameter needed for the calculation using Mich PPS. 25.5" vertical and 26" horizontal. So 25.75" is what I would use.

Using the torque showngin a RF-F stock dyno posted re haus on http://gthausblog.com/?p=6287 and the calculater from DougHII ref http://glennmessersmith.com/shiftpt.html and the RC-F gear ratios I get







When I get any torque numbers for JoeZ I will edit this post.

RCFormante

iTrader: (1)

Cool thanks for the link. Final drive is 2.94.

Here is my numbers below with my latest dyno sheet, which is pretty close to the beep, it's about 7-7.1K RPM, where I usually shift. Redline is 7.3K

RPMx1000 Shift Points = 7, 7, 6.95, 6.95, 6.95
Speed MPH =42, 70, 102, 130, 154

DougHII

RCF500:

Be sure also to check out those Wallace Racing calculators since you are having fun in 1/4s and straight lines. A lot of interesting stuff in there for that: weight, incremental hp, various time intervals and etc.