I may be in the wrong forum for this, but it is a custom chip on a 383 SuperRam setup, and I'm using Datamaster and working towards programming myself... hopefully someone can help. If not I'll go to the TPI board.

Anyway, here's the scoop:

383 SuperRam, 10.5 compression, Sportsman II iron heads, custom CompCam roller cam [218I, 224E duration at .050, lift .525I (1.6 roller rocker), .502E (1.5 RR)], in a 70's era 010 block. Have gone thru valve adjustments out the wazoo trying to make sure they aren't rattling as the cause, don't think that's it.

Problem is it runs like dung. Base timing is set at 6 BTDC, and Datamaster is cycling through 256 detonation counts in like 4 or 5 seconds. No known exhaust leaks, but I'm using SLP Tri-Y headers so they're loud to begin with. All emissions (AIR, EGR, etc.) is hooked up. This is a T-5 manual setup, and I'm getting these counts while sitting in neutral sitting in the driveway.

I'm about to give up on this one.....

I'm using a brand new 350 knock sensor for a 1991.

Any suggestions or ideas on how to address this problem? What can cause this type/level of detonation counts?

 

At idle a bearing noise can set it off, as well as a bad serpentine belt.

If it's running the count up that high that fast, you might try just popping the belt off and try running it a couple seconds to see if the knock count stops.

 

OK, I'll try that tonight. Thanks for your input.

 

What kind of gas are you running? Also, why 10.5 compression on an iron head?

Just curious...

 

Gas is strictly "premium", which is either 92 or 93 octane.

As for the compression, that's what the motor came with frm the engine builder.

 

Yeah...I will be curious to see how much actual timing you can run...I know that another user (MikeH) had a problem with aluminum heads and 11.3 compression...so I would suspect that you will too...

Good luck,

 

I had the same problem with my sportsman-II's. Show us your timing table.

-- Joe

 

I'm running 10:1 with same heads without that problem. I would double check your coil bind numbers, I think with that cam & rocker set-up, you may be coil binding if you are running the springs that came on the heads. Also it is possible to make the knock sensor "hyper" sensitive if you tighten too tight, I recommend only by hand (hand being the wrench), enough for water not to leak. This place is full of great tips, keep checking back.

 

Well, guess I need to type it again, got "cannot find server" when previewing my 1st response...

Anyway, tonight we verified the valve lash, all was fine there. Checked it both with and without the MSD Digital 6+ ignition, no difference. Took off the serpentine belt for a few seconds to make sure nothing rotating on the front of the engine is the culprit, and it isn't that. Based on 87tpi7749's sugestions, tomorrow I'll try another knock sensor and make sure it isn't tightened too tightly. I'll also call Comp Cams and verify the springs are the right ones to address the coil bind idea. Any other way to check this?

As for the timing table, this prom was done by Jeremy Formato out of FL, he's the guy Lingenfelter recommended to me when I got my SuperRam. I haven't been able to delve into the DIY myself yet, but that may come sooner than later. I'll see if he will forward me the BIN he used so we can get that info. I can offer to forward a copy of the Datamaster log file to show what it's doing, that will show the knocks, timing, retard, etc. if anyone can use that to help me.

Tomorrow night I may also try lowering the 6 degree base timing and see if that makes any difference as well. It's after 1AM here and I just finished tonight's testing, all to no avail.

THANKS for all the ideas so far, and PLEASE KEEP THEM COMING! Hopefully tomorrow will hold the solution for this. Again, THANKS!

- Vern

 

If you're getting those kinds of knock counts what is your knock retard set at? I'd be interested in seeing exactly what was done by the famous Formato's son (is it Jim's son?).
What masks detected knock at idle? My calibration doesn't start doing knock retard unless a mph, rpm, and coolant temp threshold are met.
Did you try and unplug the knock sensor? If not, try that and turn the base timing down. Don't forget about that little bypass wire being unplugged when setting base timing.

 

JPrevost, as far as the masks go, since I'm not doing the prom I don't know the answer. I do know from observing the Datamaster runs that for the most part there is no knock retard at the 800-850 RPM idle, but after it runs for a while (still at idle in the driveway) I do occasionally see a 4.9 retard briefly come in, I suspect it's temperature based at around 190 or so but haven't paid enough attention to that detail to be able to say that for sure.

Watching the Datamaster monitor when I first start the car, the knock counts are instantaneous as soon as it starts running. It only takes 30-45 seconds to go into closed loop (I did a 3 wire heated sensor conversion), but the knock counts start long before it goes closed loop. As long as the engine is running, they're there.

I'll be trying the distributor timing drop this evening, and yes, I've been doing the ESC disconnect anytime I check the timing. With it connected the timing varies from 15-24 BTDC, sits solid at 5-6 BTDC with it disconnected.

I haven't tried disconnecting the knock sensor yet. Primary reason is I thought I read in another post from my searching on this condition that disconnecting it throws an error and the ECM goes into "limp home" mode. Guess I can try that, I'm planning to try a different knock sensor as well. Do you guys recommend using a 305 or a 350 knock sensor? Searching the archives led me to believe they are different and that a 350 would be better, but I solicit input on this.

This is a 305 ECM, but Jeremy's chip is a daughter-board/piggy back arrangement so the base ECM shouldn't make any difference should it? I do have another memcal I can use to piggyback off Jeremy's chip just to make sure that isn't the problem as well.

The only two things different from the 305 and this 383 is I used a new 350 knock sensor when we installed the 383 (but new sensors have been known to be bad before), and I used a new memcal because the 305 was running a Jet Performance memcal and I figured it would be better not to use that. All the other sensors and front accessories are the same as on the 305. I may swap the Jet memcal into the ECM just to make sure it's not my "new" memcal piggy backed off Jeremy's chip that's causing the problem. Don't see how it could be, but then again stranger things have happened...

I'll also try and find out if he is Jim's son for you, but that may be this evening before I can get that info.

Appreciate the inputs and ideas, PLEASE KEEP THEM COMING!!! It's probably going to be some little thing we overlooked on the engine swap, hope so at least. I fear it's something internally wrong in the engine that's gonna come back and bite my a$$, but I sure hope/pray that's not it.

Have a Great Day!

- Vern

 

I believe the knock sensor goes on bore size and the 350 sensor is the accepted one to use for a 383. -John

 

Really the general idea is to keep the knock sensor with an engine of similar bore since it's the cylinder wall that's producing the frequency and different diameter cylinders have different natural frequencies. The only odd thing is that a piezo electric microphone picks up all noise and vibration, the ESC contains the filtering information to process the amplitude and frequency. So I believe any knock sensor will work but it's good to have matched knock filtering. A trick is to use the older ESC modules because they have a double filter that seems to be less sensitive to engine noise.
As for the removed knock sensor, I don't know what it'll do to your car but if it's got the knock routine where it forces the engine to knock to check if the sensor is working they yes, it'll set a code and run bad. The trick is to start the engine cool where the temp is below the threshold and don't do any WOT runs (obvious since we're still working on the idle ). So I highly doubt you'll get an instant code if the knock sensor is unplugged for initial startup.
Does anybody else know this Formato guy? I never heard of him until recently but it seems as if he's been around the vette scene for a LONG time. I read that Jim passed away and his vette is for sale for $40k being sold by Jeremy Formato.

 

the Formato chip was one of the 1st mail order (good) chips out there, I believe...I am sure that Grumpy would have some input to the way that this actually occurred...

 

You're not going to believe the solution....

When I swapped out the 305 and put in the 383, I went to install Jeremy's first chip on this set-up. Since it was a piggyback arrangement, I was planning to use the original 305 chip. I had previously asked Jeremy if I could use it, and he said, any memcal should work.

Imagine my surprise when I opened up the ECM and found a JetChip memcal. Not a piggyback configuration, but an actual regular looking memcal with a Jet sticker on it. Not knowing if this would be a good idea with Formato's setup, I chose instead to put in a 350 memcal I got off of eBay a few months ago.

After pondering where the problem could be all day long, I decided to take out the piggyback custom prom and just put in the original Jet memcal and see if I still had the knock count problem - I didn't! Fuel map was definitely off, but no knock counts at idle or while revving the car in the driveway. At that point I pulled the Jet chip back out of the ECM and replaced the eBay chip on the Formato piggyback board with the JetChip. No Knocks using this one either!

So the problem was the eBay 350 chip as the memcal on the piggyback board. Then I got to looking closer at the eBay memcal and noticed some numbers on the prom. From what I've learned the last few days I knew it was the memcal ID, so I tracked that down and learned it was from a 1989 TPI 350, which was a MAF based ECM vs. my speed density setup. So I guess I learned that MAF memcals have changes in the ESC area of the memcal and was not compatible with a speed density prom. In other words, they are not interchangeable at the memcal level (other than the prom). Either that or I've just got a bad one.

I really appreciate all everyone's ideas and assistance on this, and I still intend to delve into the DIY area (I've already bought Datamaster and downloaded TunerPro RT). My next step is to figure out how to pull a copy of the BIN file off Jeremy's chip so I can watch what he changes and try to better understand what he's doing for me and why.

Again, Thanks to everyone!!!!!


- Vern

 

I can't believe you got that to start with the MAF memcal..

-- Joe

 

The MAF TPI MEMCAL doesn't have the knock filter as part of the MEMCAL, where the SD TPI MEMCAL does.

Look at the two MEMCALs and one will have a small white board with a clear covering on it. That is the knock filter (ESC module). On the MAF cars this is a separate module under the hood.

RBob.

 

Hmmmm.... I hadn't noticed that RBob, but will check it out tonight. I don't quite understand how that would cause continuous knock counts, but then again I don't know which circuits are getting evaluated for what on the different memcals. Seems strange that would cause continous knock counts, but stranger things have happened. Regardless, I'm only getting an occasional knock now (20 some if 30 minutes of in town driving), so we'll address that in the "normal" tuning process.

Again, Thanks to everyone who offered suggestions and lent a hand in trying to help me out on this one!

Have a Great Day!!!


- Vern