new weird observation.. low launches == better time to 105 than 2k launches ????

[TopherSho]

Just as the title spells out.. I can consistently get better times to 105mph (should be 1/4 mile time equivalent) by launching at much lower rpms, BUT it drops my 0-60 by 2 tenths.. (4.7-4.8 avg)..

if i launch at 1900-2000 rpm i can get 4.6x seconds 0-60 pretty reliably on dry land.. BUT then it utterly TANKS my 0-105mph time to the tune of 13.x+

super weird..

i noticed in reviewing my old datalogs that one fine day on the 29th of april i did a run from 0-105mph in 12.66 seconds.  every other log on earth has me at 13.xx+

so for giggles today i tried another low launch.  i tried for the same 1200rpm launch as in the older datalog.. but missed and did a 1600 rpm launch.  i swear it was slower feeling than a 2k launch.  yet .. boom we have a 12.9x 0-105mph.. which should be super close to my new 1/4 mile times.

obviously i am super confused.

there is not ANY tire-spin in the 2k launch.. just a hint of a chirp on the 1-2 for both logs.

wha???  AJP save me from this madness!

[StealBlueSho]

I think... the best way to prove that out would be a track with 60ft times...

Rich I believe said he launches around 2K RPMs and has managed low 12's..

[TopherSho]

I think... the best way to prove that out would be a track with 60ft times...

Rich I believe said he launches around 2K RPMs and has managed low 12's..

oh I believe him.   I mean the 0-60 is way better with a 2k launch for me.. i'm baffled.  nothing about this car makes sense yet which is likely due to me being new to boosted power.

[FoMoCoSHO]

I'm gonna go with heat as the culprit.....low rpm launch, slower heat build up.

[StealBlueSho]

I'm gonna go with heat as the culprit.....low rpm launch, slower heat build up.

You think? I mean the launching difference of say 800 RPMs I wouldn't think would make that much difference in IATs.. unless your holding the RPMs longer...

[FoMoCoSHO]

Id look at boost levels at each rpm.....it doesn't take much boost to make a bunch of heat with nothing flowing through the IC....

[TopherSho]

are you suggesting that brake boosting is building to much heat in the system other than the IAT?

[SHOdded]

Tires in good shape?  Is traction an issue?

[FoMoCoSHO]

are you suggesting that brake boosting is building to much heat in the system other than the IAT?

I would say this would start to heat soak IAT2@ right off the bat. The more boost you put through that intercooler without any airflow the hotter IAT2 heats up before you start moving.  Your intercooler is starting to heat soaking when you launch. The higher boost launch gets the initial boost advantage but loses spark up top, the low boost launch is reversed.

I want to loosen up my IAT2 compensations and let the E85 do more work as IAT2s rise. The higher the temps, the more heat it removes from the aircharge. The challenge is we can't see the cooling effects because unlike meth, it is happening in the cylinder. If needed, I can increase the amount of cooling with higher blends or increased enrichment as well.

[10bird]

If heat is slowing it down why is the 0-60 quicker with the boosted launch?

[Macgyver]

Good point.

[FoMoCoSHO]

Do you have the first log in csv format?

[TopherSho]

Do you have the first log in csv format?

/facepalm/  posted the audit of the datalog in error .. here is the orignal csv

[TopherSho]

Tires in good shape?  Is traction an issue?

tires are actually pretty good.  there less than 10k miles old.. 

i rarely have 1-2 traction loss unless it is colder or i launch like a lunatic.  even then it is not wheel spin per say but more a wheel hop for 100-200ms..

[TopherSho]

are you suggesting that brake boosting is building to much heat in the system other than the IAT?

I would say this would start to heat soak IAT2@ right off the bat. The more boost you put through that intercooler without any airflow the hotter IAT2 heats up before you start moving.  Your intercooler is starting to heat soaking when you launch. The higher boost launch gets the initial boost advantage but loses spark up top, the low boost launch is reversed.

I want to loosen up my IAT2 compensations and let the E85 do more work as IAT2s rise. The higher the temps, the more heat it removes from the aircharge. The challenge is we can't see the cooling effects because unlike meth, it is happening in the cylinder. If needed, I can increase the amount of cooling with higher blends or increased enrichment as well.

i am wondering this as well.  and not just the IAT2,  but the cylinder heads, and coolant in general.

i need to run more low rpm tests before the 170' t-stat comes in.  sadly it is going to rain here for DAYS,  and prevents me from going to the track to get a real third party performance metric.  by the time the rain stops well be in vega$ for a week ..

bah!  damn vacations interrupting my SHO-work ..

tired... good night all.. thank you for your ever ready thoughts on my insanity