anestech*

Notice the dip near the torque peak. It is obvious in the exhaust note as well. It was like this when it was stock as well (got it with 14K on the odo). I've cleaned the MAF element, ran a can of seafoam through it and put on a catch can as well, none of that helped anything.

I don't plan on doing any more engine mods for at least a couple years. I have a TB coolant bypass that will go on this week.

A tune should get rid of that, right? Before I plunk down $500 for a tune, I need some reassurance.

I plan on having Xtreme Motorsports in Tempe, AZ do it. Unless you PHX guys have any other recommendations.

Mazzenger

iTrader: (5)

maybe a colder plug would help?

Revelation222

If you truely do not plan on doing any more mods for a few years, you might as well get a tune now. You will get rid of the KR (assuming it isnt false knock), and possibly gain 10-15 hp depending on you current a/f, timing, etc.

A good tuner will normally give you a discount on future adjustments to the PCM after they have done a full dyno tune, so make sure that they have a similar program.

Good luck to you.

anestech*

It did it with the stock plugs as well, and there was no change when I put the TR55s in.

lilbuddy1587

iTrader: (1)

I say call AZ Dyno chip and let nic tune it. He's one of the best if not the best in AZ

Edit- He's on here as well, forgot his SN

Another_User

If that knock isn't false, then you have a problem. And it is not something you will be able to tune out (if you do, it will just mean a lot less power). You really need to log your trims, KR, etc. before you go any further. Is your MAF screen still in? Did they log your AF ratio? If that is real knock on a stock timing table and everything has been cleaned out, then something is probably puching your engine way lean. False knock will make your engine sound different. My 98 sounded way different before I tuned out my false knock. It got really loud and rumbly and the car felt like it fell on it's face. The sound changes because of the pulled timing...but your knock may be real.

anestech*

MAF is stock (still has screen), and I have cleaned the elements with contact cleaner. No change. I emailed them to have them pull my a/f ratio, but they just moved locations and that dyno was from Feb of this year, so I hope they still have it. It was out of whack, but I don't remember if it was lean or rich, pretty sure it was lean.

You can hear what it sounds like in the video I posted in the original post. Sounds like it is hesatating or stuttering.

anestech*

I found their info, and sent them an email. Thanks!

RevGTO

iTrader: (12)

Another thing to consider is the quality of gas you get in your area. The highest octane we have here is 91. I think 91 is marginal for a lot of LS1's. When I add BG Supercharge to mine, it makes a noticeable difference.

anestech*

Yeah, both here in AZ and back in CA, 91 is the best we get. I've thought about trying octane boost and seeing if it clears up, but I would rather get a tune than have to buy octane boost every tank.

Revelation222

So what is is called when my header was banging on my frame causing the car to pull timing? Real knock retard? Maybe i used the wrong terminology?

Another_User

Well...that would be false knock. But I doubt it would look like what he has on his dyno sheet. His looks like something I would expect out a 98 car.

RevGTO

iTrader: (12)

BG Supercharge is actually fuel system cleaner product, but it must have a lot of naphtha in it, because the difference is incredible when I throw it in the tank. Using it has shown me that my car pulls some timing on 91; you can experiment with it or some racing gas, and if your problem goes away, you'll know the source.

Revelation222

My bad on the terminology then. I thought thats what I was refering too when i said it. I thought real knock would be caused by detonation.


Why just a 98 car? Just Curious.

lilbuddy1587

iTrader: (1)

Sounds like you need to have a complete fuel injection cleaning done

Another_User

Most 98 cars have mysterious false knock that appears at about 3500ish rpms and pulls about 4 degrees of timing. Oversensitive knock sensors. It would look a lot like that on a dyno graph.

anestech*

I just dumped a bottle of CD2 octane boost in it with a fresh tank of Chevron 91 (the car has ONLY seen Unocal or Chevron 91 since I have had it). I'll let it diffuse into the whole tank for a few days, then give it a good flogging and see if it changes. The funny thing is that I can usually only notice it NOT under load, like just a hard rev. At WOT under load, I usually can't hear/feel it, only every once in a while.

Will be talking to Nic at AZ Dyno Chip about a tune as well, and I sent them an email with this attached.

Hopefully gonna have someone with autotap take a ride with me as well. And PHXers wanna do it for a 12 pack?