Im having a problem where no matter what time I run at the track it ends up being 94.x MPH. Ive gone 13.521-14.1 and the MPH stays the same no matter the 60ft, hooking dead on or spinning. I was told by getting a scan tool I might be able to see whats going on and possibly it could be a knock sensor giving me problems, heres what I got info wise, can someone help me decipher it please.

Throttle sensor: .64
O2 sensor: 409 mVolts
MAP: 1.25 volts
Battery: 13.7 Volts
Spark Advance: 18.2 degrees
Knock Sensor: 8
Knock Retard: 0 degrees
Rich Lean Flag: Lean
Loop Status: Open

This is just part of the info, the more important stuff Id figured but I dont rightly know. Can someone please let me know what are the more important stats to look for, whats's within spec and if they see anything above that raises an eyebrow or if I left something out. I have access to the scan tool (Auto Xray) for the next couple of days so no hurry but any advice would be greatly appreciated, thanks!!

 

OK, that looks like data while you were idling, it's of no value to us.

I'm not familiar w/ exactly what functions the auto xray has. What you need is the ability to store data while you do some 1/4 mile blasts. If it can do that, you're set.

What you're looking for is things that are weird. The fact that your car is so consistent is actally a sign that there might not be much wrong w/ it, at least from an easy to diagnose point of view.

At WOT you don't want any knock retard. If you're getting a bunch of knock counts and retard at WOT then you are losing power. Do whatever is in your power to stop the detonation (which ranges from simply reducing base timing to writing custom code in the chip to pull timing on upshifts to avoid that common detonation point)

If this was a consistency issue then you would look for stuff like inconsistent injector pulsewidths to give you an idea of what your ECM was doing wrong, and you could use other sensors to pinpoint why the ECM is doing that wrong thing.

Beyond that, i don't even know your combo so i don't even know how far off you are from what you'd expect. Keep in mind it doesn't even have to be something in the ECM/calibration. A tranny / TC on it's way out can eat power (even if you don't feel it slipping.) You could have a caliper thats partially frozen robbing power. You might run way too sticky of a tire for your power level and / or too little tire pressure which also costs power.

My pie in the sky WAG is gonna be the last of those. 1.7 60's is bad ***. I'm sure you're running some kind of boots for that. What type are they? Yes, sticky rubber will most definitely slow your car down. Especially (ex.) if you're running a 10" slick, thats just too much tire for a 13 second car. Also, if you're airing them puppies way down for bite, that will also eat heavily into your mph. If you have a basic 100mph L98 car w/ 10" tires at 12psi, well i think i should win a prize for pulling this out of my *** so fast. If not, well, it was worth mentioning, eh?

 

Thanks for replying so fast and yes thats at an idle. Ill try and get some runs in when I can and look for what you were talking about. Altho it still lays down some good numbers the car has not run smooth for a long time now. I had myself, a friend whos a mechanic, another local ASE Mechanic on the side and 2 other shops try and hunt the problem down(rough revs and vibrations at 2500 rpms). I gave up after spending good $ after bad but its not as bad as it may sound without changing the topic to a trouble shooting question. As for my combo is nothing more than basic boltons, SLP 800 over stock converter, shift kit and cooler. Back in Nov I ran 13.521 at 94.7, since then added SLP 1 3/4s and !AC and I ran 13.608 on a 1.798 60ft at you 94.3 MPH last Sat and I was expecting atleast 1-2 MPH added to my traps and a 13.4x. I got 4 more runs in that day and the 60fts crept up to 2.23, MPH was still 94.x. Im running BFG drag radials 255/50/16s and I run em at 15-16 psi, maybe I should try adding more psi but when I experimented when I 1st got them more air wasnt the solution, 16 psi got me the 1.769, too much got me 1.9s at best but it wont hurt to give it another try with different air pressures. Thanks for your reply and info its appreciated!!!

 

OK, drag radials aren't that extremely sticky, good choice of tire for what youre doing. It's worth experimenting w/ pressure for sure, the more air you can run, the faster you'll go, and the more stable you'll be on the big end.

I think i rememeber now, you posted a similar question as part of another topic right? I think you had a relocated MAT as well, and theselatest runs were at e-town last weekend right? A relocated MAT will cause a pretty over-rich condition on SD cars. If you don't have any chip work whatsoever that could be hurting you. Do you have an AFPR? If you're running extra fuel pressure you could be compounding the problem.

i know it sounds like a cop-out, but i'd really like to see you do some TnT with it at the track and report back. Move the fuel pressure around and see what happens. If you drop fuel and go faster then you know what that means. At the very least go out and do some plug reading. Do a good top of 2nd to 3rd gear WOT blast and cut the engine off and roll to a stop. Pull a plug and see whats up. That'll give you a good clue as to where you are. You can also look at your O2 volts at WOT on the auto-xray. Tuning by O2 is pretty useless, but if you're O2s are hella high (like 1V and beyond) then you know you're way fat. Similarly, if they're in the 700s and you know the sensor is warmed up then you're probably way lean.


Beyond that, i know you don't want to keep throwing money at the car, but have you considered sending your injectors out for cleaning? A frshly cleaned and balanced set of injectors is always a good idea and certainly eliminates that as a possibility. While i didn;t pick up a lot of power when i put my injectors in, it definitely made a difference as far as my tune went. I could run a bunch more timing in the midrange, my theory is that i had a weak injector or 2 leaving me some lean holes to detonate with the high cylinder pressures of the torque peak.

 

Yep thats me and Im just trying to figure out whats up if anything with this car. I have an AFPR but its not on yet so thats one less variable to account for. I did a few quick blasts with the Auto X ray and under WOT the 02 Volts read 924 mVolts and 941 mVolts on the 2nd monitoring looks a lil rich Im assuming? I get KS readings of 15 and 20 respectively and 2-4 degrees of knock retard on the 2nd run. Ill check the plugs tomorrow, I changed them not too long ago so it would be a good idea to see where shes at so thats some good advice as well as the injector cleaning. Once I check a few more things and TnT at the track some more Ill see what I can come up with and Ill post the results. As for proms its a Hypertech II so I dont know how that would affect the relocated MAT but like I said thats easy enough to put back into the factory location to see if its part of the problem. Sorry for all the question but I appreciate the answers, info and suggestions, half the reason my car runs what it does is thru searching archives, asking questions and talking to others. I started late on the whole 3rdGen and even 1/4 mile stuff and have some catching up to do, but better late than never....

 

The autoxray does have a record mode.
13.5 @ 94mph! Man, you must be getting out of the hole FAST! My 13.81 was at 98.96mph. my 92Z28 convt 14.21 was at 96mph. Thats what I call an efficient driveline. What gears you running?

 

Stock rear 3:23s and a best of 1.76 short time, the car hooks strong for what it is, I just hate seeing 13.5-13.7 at 94.x MPH but yeah I guess that sure is efficient....

 

This might sound weird, but you ought to try putting the stock chip back in. The stock bin isn't bad, and you can always move the distributor.
For now i'd put the AFPR on it and go to the track. Do some testing with the relocated MAT and in the stock location. Keep track of the O2s and injector pulse widths @ rpm. At least 2 consistent runs w/ each, usually best to keep it kinda warm for consistency. When you know which one is best, use the AFPR and timing to fine tune it. If you're getting knock retard definitely drop some timing unless it's already set low. In that case i'd consider the injectors like i said.
Don't look past the little stuff.

 

I finally got to watch your videos in the other post. IN the 10 second video you can clearly hear the problem. Right after the shift into 3rd gear you can hear the motor bog down. It's one of 2 things, guaranteed...

- knock. it just happens on upshifts for some reason and it coudl besuckinga bunch of timing right there.

- the torque converter clutch. In the stock chip it's set to lock up at 75mph. When it locks up right after the chip, it can pull the engine down out of the powerband, the higher stall would make that more noticed. The only fix to this is to hook up a lock-up switch or get into the chip and change the TCC unlock prevention speed.

 

This is the kinda of info I was looking for. Ive run with and without the aftermarket chip with NO change in ET. My next run which in all likely hood will be this Sat Im going to put the stock chip back in, return the MAT to its stock location and keep an eye on what youve said. I dont think Ill have the AFPR on before then but you never know. AS for the lock up causing the car to bog down, its done that forever and its a main thing Ive asked about ever since I noticed it in the vids and now it makes sense. I figured it was possibly that, fuel related or recently I was thinking it was my KS. I have a harness I bought way back that prevents the converter from locking up and simply plugs inline at the tranny, looks like I got some things to try next trip to the track. Will that harness hurt anything tho other than gas mileage that I could care less about?? Now I just got to hope for good weather Sat., consistant 60fts and lets see if I cant figure this out with your help, Ill keep you posted!!!

 

I did a little messing with the car today, I got rid of the poly tranny mount couldnt take the rough ride from it, also removed the chip and started to bump the timing up. On the scan tool I got KS=43 and 2 degree NR at 70 MPH aprox so I guess it likes base of 6 degrees, 6 degrees showed KS=15 and KR=0 degrees under similar conditions. I also threw in the harness to prevent the conv. from locking up so we'll see if that helps or not. Tomorrow Im gonna see about putting on my fuel presure gauge to see what its doing and Sat I should be hitting the track again if the weather allows....