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THE BEAST's Avatar
Posts: 1,427
Join Date: Apr 2016
Car: 2008 E93
Default 08-23-2019, 10:55 AM

Originally Posted by codesx
Hey Beast,

My intent with this specific thread is to better understand how to limit damage to the car, while still going 'almost' flat out.
I've read some threads where people say "as long as you shift right...", and have wondered what they mean about this.

- I believe I'm learning that I should not put my A/T in Manual, put it in 4th at 120kph, then floor it and shift to 3rd at the same time. It hits like a rocket, but this is also how I shredded my serpentine belt last fall. (abrupt RPM change on the crank pulley takes 100-200~(?) ms before other pulleys have adjusted to the same. This can cause momentary stretching of the serpentine belt, causing it to jump one (or more) of 7 groves, resulting in super shredding and possible ingestion into the engine via the crank pulley seal.
- I'm still testing, but maybe manually shifting next to 7000RPM results in poor timing recovery, vs a manual (A/T) shift at 5900 RPM.
- Perhaps timing recovery is harder during shift with the xHP A/T tune? (the DME 'projects' RPM values as it calculates things, this is why, with the xHP A/T tune, you often need to set certain RPM values to "20,000"... not that it will reach this, but if it measures 800, 2000, 6000, it will project in the next 100ms it will reach 16000, meanwhile we are shifting and never get there (fact that some calculations with xHP (if not the transmission itself) use this 'projected calculation').

So, at this point, I'm trying to figure out how people shift, to lighten the intensity on the engine/tranmission/drive-line, while still being (almost) flat out.
(maybe some people let off the throttle by 25% as they shift to help timing recovery?)

--- Meth testing variations (BM10 & BM5) ---
To respond to your earlier suggestion of logs;
I respect it's annoying when someone asks for help and then they don't produce much when asked. This drives us all nuts.
I started this thread just before I realized my meth ratio detail was impacting Fuel Trims and Timing. I'm testing a variety of things, from timing recovery during shift at different ratios, etc.
Currently logging (all values meth/water)
30/70, 3rd gear pull, 1,2,3,4 pull for timing recovery review (done)
50/50, 3rd gear pull, 1,2,3,4 pull for timing recovery review (done)
70/30, 3rd gear pull, 1,2,3,4 pull for timing recovery review (Fri/Sat)
100%, 3rd gear pull, 1,2,3,4 pull for timing recovery review (Sun/Mon)
80%, 3rd gear pull, 1,2,3,4 pull for timing recovery review (Mon/Tues)
60%, 3rd gear pull, 1,2,3,4 pull for timing recovery review (Tues/Wed)

I've attached generic logs (50/50, BM10) for 3rd and 1,2,3.
We can see that the timing doesn't recover over shifts. I had intended to create a unique thread for that subject after I completed gathering the relevant information.
Maybe try a custom tune ? I see you dont hit 19psi until 3500 and then fall off well before you get to 6000 rpm.
Never the less, I would limit 1st gear boost. Try 12 psi and launch. If it hooks, try a little higher boost, if tires spin, try 10 psi, etc.
Early shifting to minimize momentum loss as you mentioned earlier will kill your time. You want absolute traction for better time.
Im also xHP and always drive in manual mode, shifting down to 4th, hammering the gas, and downshifting to 3rd is not the best thing to do. If you are roll racing, you will do better smashing in 3rd and then upshift to 4th DEPENDING on your actual launch speed of course (im just going off your example), downshift or upshift kills time as well. Even if its a fraction of a second, you are still losing time.
If you want, you could try a different value in auto shift reduction vs letting off the throttle before shifting. There should be no need for that. The videos I sent you are 100% floored through all gears.
As far as breaking things, the more the car hooks, the more the driveline takes the hit. So either traction slips a bit and you get not so great track times (and helps save driveline), or get better times with tires that hook and risk breaking parts.
Also I believe thats a typo on your manual vs manual shifting from 5900 vs 7000rpm. You should absolutely be shifting IMO at no more than 6k given your logs posted, for better E.T. Personally, I would shift around 5800 rpm for your particular set up to stay within powerband.

Last edited by THE BEAST; 08-23-2019 at 11:01 AM..
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