More Datalogging

[Scottie-GNZ]

Here is the datalog from my best run last Wednesday night. As a refresher, the car went 1.687, 7.18 @ 97.58, 11.22 @ 120.24. Despite a 1.68 60', the launch felt soft, the car hesitated most of the way down the track and you will see the cause in the data log.

 

 

0-60 in 2.83 gets boring after you see it a couple of times so this time the point in time is 100mph which you can see came up in 7.25 secs at 679' and that is right in line with the 1/8-mile time.

 

Now the spoolup "problem". First, take note of the SPEED box and see where the car starts moving. Now focus on RPM and TPS and you will see where I went about half throttle and the RPMs immediately came up but the boost did not, so I floored it and held it (TPS now wide open) and even with it floored, notice the RPMs barely changed and at the point that I released the transbrake, I only had 5# boost. During spoolup, the chip senses TPS open and no speed and is supposed to lean out the fuel but the O2s are about 800 at that point, which is too rich and why it felt soft.

 

Once the car got rolling and hit full boost, note the sharp rise in the RPMs and the 1-2 happens so quick you almost do not feel it. Now for the other "problem". The chip retarded the timing at the top of every gear and mysteriously after the 2-3. There is sometimes maybe 1* of retard on each shift but I had too much retard too many times. The big retard on the 1-2 is understandable because there was a drop in the O2s. The drop was previously a major spike so he did hit on the problem but still does not have it right yet.

 

At 100mph, the O2s are 816 and still too rich. It was dropping as the load increased in 3rd but you can see it was richer at mid-track and that is what makes the retard unexplainable, at least to me .

 

If he can get rid of that dip in the O2s and all that retard, I should see a nice gain, then I have more boost and about 40mV to play with.

 

Enjoy!

 

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Scottie

71 240GN-Z

Scottie's GNZ

[Drax240z]

I love it! I need to get me one of those... (ok, so maybe I should get the car running first! )

 

The stuff occuring at the top of first gear (1-2 shift) seems wierd to me. Why would there be a drop of O2's there? Small chip problem?

 

 

 

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"Nothing is fool proof to a sufficiently talented fool."

 

Richard Lewis - 1972 240z, Powered by a Nissan 2.8L Turbo Inline 6.

Drax240's Turbo Site

Beginners Turbo FAQ & Answers

[Kevin Shasteen]

Scottie,

 

Very interesting stuff. BTW-I was checking out some auto/performance books again this past Saturday at B&N. I came across a TPI/LT1 book that stated you should disconnect the O2 sensor during racing(?). It also suggested using a diode/resistor (whatever) on the coolant sensor that bypasses the coolant sensor while racing as the book stated the coolant sensor will have a tendency of retarding the engine.

 

I know this book was about the LT1..but it's still a GM EFI & probably has the same effect as your system.

 

If you're curious about the diode I can go back to B&N & find that book/relay back here which diode/resistor they suggested(?). Every little bit helps-this may be enough to get you into the 10sec realm. Have you heard of doing this before? What are your thoughts?

 

Kevin,

(Yea,Still an Inliner)

[Scottie-GNZ]

Kevin,

 

I can only guess at why they would do that and it is certainly not something that I would or want to do.

 

I am guessing that if during race mode the O2 reading is lean, the ECM will retard the timing and I can tell you about that . By disconnecting the O2, they are forcing the ECM into open loop mode, and by not using the temp sensor, they are trying to fool the ECM into thinking the engine temp is cooler and force it to richen up the fuel.

 

If they say that works, then good for them but being N/A they have more of a safety margin than a turbo/s-charger. BLKMGK has an Impala SS and knows some of the tricks they deploy and maybe can have some input here.

 

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Scottie

71 240GN-Z

Scottie's GNZ

[Kevin Shasteen]

I was kind of thinking the "Normally Aspirated" factor was an issue when making those mod's...oh well, just trying to get you in the 10's/back to the drawing board I guess.

 

Kevin,

(Yea,Still an Inliner)

[BLKMGK]

Honestly... don't F* with the sensors like that! There's a bunch of tricks like that that th eMustang guys do too - it's STUPID. The computer needs to see accurate data. If ynking sensors makes th ecar faster than the ECU programming isn't optimized. In Scottie's case and in the case of the Impallas it's actually possible to modify the stock programming - bonus! Until recently doing this on a Mustang was nearly impossible - the SpeedBrain and some other boxes have helped a great deal. Custom chips are a great idea too but only if you've got someone you can work with like Scottie does. Fooling sensors is a little risky on a N/A car but death defying on a forced induction vehicle (shiver).

 

Always understand what it is that you're doing when fooling around like this - pulling an air temp sensor makes the car run richer when it sees cooler air - terrific if you've uped airflow and it's NOT a MAF based car (Scotties is and so are the Impallas). O2 sensor being pulled makes it go "limp home" I think - no telling what curves it'll be but expect conservative. Water temps changes from thermostats and whatnot also make it go rich usually - it will often think warmup mode and this effects ignition timing too (doh!). The "recurved" MAFs that Ford guys use are also a BIG mistake - hard to explain quickly but it also totally changes the ignition curve - BAD idea! Ahem, I've got one on my car with a custom chip - I know it's not optimal, I can explain if anyone needs it.

 

Anyway, you get the ideas - best to tune the chip and not voodoo the sensors IMO.