Background:
9.4:1 scr 408ci sbc
AFR215s, MRII, MB
large solid roller cam (240+/250+ @0.050")
currently 12 psi SCed boost at 6300 (D1R)
street car w/ pump gas (93 advertised octane), no additives
FAST tuning
A/F Ratio typically (under boost) 11.6 - 12.2

Issue:
I have run with timing retarded for nearly 14 mos now due to high IAT issues (225° at end of full 1/4 mile pass). I have recently went to a very large IC, but it is not quite installed. I ran the timing up by 2° under moderate boost and 1° at full boost (21.5° total). I was happy with the motor as it was, but decided to experiment. The motor really liked the extra timing. I am thinking of putting more timing (used to run 26-28° total timing at full boost). I upped the ESC (knock) to 3° max, and saw no knock under full load, though I always seem to get some knock retard just cruising (SR cams tend to be noisy).

BTW, I still get the black dots on the rear bumper regularly, though it runs well, and the plugs are regularly quite black and "fueled".

Thoughts on cranking the timing? Leaning out the AFR?

Thanks,
Aaron

 

Aaron, my experience with the FAST stuff and knock control, is that it doesn't work real well. Personally I've had situations where the plugs scream detonation and yet the knock sensor never went off. I've also seen a few motors taken out by detonation where the knock sensor didn't go off. I put zero faith in it.

If that black on the plugs is near the center electrode end of the plug, you're looking at the A/F mixture of your part throttle and idle areas. The WOT fueling is read down at the base of the ceramic inside the threaded part of the plug.

To get an idea if your timing is where it should be you need to look at the ground strap of the plug after a WOT pull. With a proper heat range plug you'll see the ground strap "blue" back to where the ground strap makes the 90 degree angle down to the body of the plug. If the heat line is near the tip of the ground strap, you can add some timing, if it's past the 90 down towards the threads, you need to check the ceramic closely for signs of detonation. With no signs of detonation, I'd be checking the fueling ring down at the base of the plug. You could probably lean it out a touch and drop back a degree or 2.

Disregard this if I'm repeating stuff you're already aware of.

Paul

 

SloR,
I run the FAST with the LT4 knock module. I find the FAST knock control to be, if anything, overly active. For the most part, I leave the max retard at 1°, just to get an idea if I am seeing any detonation. I tend to get knock either in part throttle situations, or at gear shift. I theorize that these are all a function of the SR cam (lash is ~0.018") and the single mass flywheel (box of rocks "clunking"). I do run more spark retard when experimenting (such as adding timing as mentioned).

As for plug readings, they tend to be black (or possibly even a bit wet) over the total center electrode. I am not sure how I would be able to see the base of the ceramic inside of the threaded portion of the plug. Please expand on this subject.

Another issue I have is that even after a full WOT run, then you have the drive back to the house. Are the "tell-tale" signs of the WOT run negated by the part throttle/idle back to the house?

I have checked the plugs, and it appears (very hard to distinguish) that the "blue line" or more like the high heat line is ~50% between the ground strap end and the 90. The face of the electrode (ring on the ceramic around the actual electrode) ranges from light/dark chocolate to almost black, migrating to what I would call black fuel fouled all the way into the threaded portion of the electrode on all eight plugs. This is on the Autolite AR3910 plugs (these are the "cut-back" racing plugs).

Thanks for all of the help.

Aaron

 

Interesting of the knock deal. I've seen a bunch of messes with the Buick stuff.

Those plugs you've got sound like they're on the cold side. The plug isn't getting hot enough to clean the ceramic. I just checked my cross reference and they're crossing over to a #9 plug in the NGK line. That's pretty damn cold to be running on the street. For reading timing the NGK stuff is real nice because they use a cad plating on the ground strap. Instead of trying to read the blue line you look for where the plating's burnt off to. I'd look at a R 5671a-7 or a R5672a-8 in the NGK line. The 7 is a non projected tip where the 8 is a projected tip and a little colder than the 7. My cross reference has the AR3910 being a projected tip.

If you get the plug heat range in line, then the tell tale signs of detonation on the ceramic will stay visible.

I was going to put a link in here to Pro-Systems Carbs website. They sell an ottoscope - the thing that a doctor uses to look in your ears - thats been slightly modified for using to read spark plugs. It's a little pricey but it flat out works. I've tried using those magnifier things that Jeg's and Summit sells but they're no comparision to the ottoscope.

You've got your fuel map set up so that at those points where the engine is getting "lugged" on the shifts it's getting a good shot of fuel ? Negative correction from the upper rpms isn't affecting that fueling point after the shift ? It's a whole lot easier to keep an engine from "rattling" than it is to get it to stop. Those knock places you're describing are places where real knock occurs a lot of times.

Not to change the subject, but I'm going to How's your valvetrain been holding up ? I'm pretty sure I've got the twin to your cam in my new motor. Nitrous and compression rather than the blower.

 

SloR,
Thanks for the in-depth reply. Are the NGK plugs that you reference (5671a-7) available over the counter at say O-Reilly's or AutoZone? Do you know if these are direct crosover for the AFR heads? Is there such thing as a projected tip that might be a bit hotter (i.e. 5670a-8)? I started running the Autolite Racing plugs per AFR recommendations. I would agree, that I think they are too cold, as I used to run the AC FR3-LS6 that I ran in the D-ports. The AR plugs seem to get better if you just continually hammer on them.

Another issue I continually have is the black specs on the rear bumper. I have never been able to completely get rid of this since converting to Speed Density. I have reduced the "pump shot" and have even thought about negative fuel addition when the MAP sees sudden negative change in psi. I may go back to more fuel addition. I will say that I have the fuel addition stop at 108 kPa, so I see no addition (or subtraction) under boost. This has always been the recomendation per FAST and other tuners. Keep the suggestions coming.

As for valvetrain life, I have had no issues. I have been running this cam for over 3 years, and am very happy with the longevity. It will idle at 870RPM, and pulls nicely from 1700 past 6300. My shift lite is set at 6300 and my rev limiter is set at 7000. I have not tried to pull past 7000, but it may be capable. Lift is over 0.660".

Any thoughts at what point I would have issues with the high IATs? I regularly see 225°F. But the pistons are JE customs???

Thanks for all of the help.

Aaron

 

Those plugs are a direct replacement. 5/8" hex, .750" depth, 14mm thread, gasket seat. I've gotten those through speed shops. They are listed with NGK's racing plugs.

Sounds like you're asking for a 6 series heat range, projected tip plug ? The last number in the in the NGK part number series is the heat range. Lower being hotter.

For an over the counter plug you could try an Autolite 3923. I think of them as being between a 6 and 7 in the NGK line - closer to a 6. I take a Dremel tool with one of the little cut off wheels and cut back the elctrodes on those and have good luck with them.

Your bottom row in your VE table should be your deceleration area. Just remember to feed her as she comes back to idle. I use the MAP enrichment to carry AE a little longer. The TPS is immediate and the MAP takes a little longer. They're both only really for enrichment for changes in throttle position. Your VE table should take over after that.

Where is your IAT sensor located ? If your legitimately seeing 225 degree inlet temps, there's a bunch of power left on the table if you get those temps down. That new intercooler's gonna be interesting. Drag racing my V-6 with a large air to air intercooler, I was thinking liquid intercooler when I was seeing 185 degree IAT's.

All of these things are what if's though. Get the plugs in line so you can actually work on being able to see what's happening.

 

SloR,
Do you have CCom on your machine? Are you able to read the FAST files and logs? If you do have FAST files, I would be interested in what sort of TPS AE and MAP AE that is in the set-up. I would love to see these files. If available, maybe you could email them to me.

My IAT is located ~10" in front of the TB. I see temps that are well in the 225+°F range after a full pass. I will call the local auto parts stores to see if they have (or can get) a NGK 5671-6 or an Autolite 3923. What heat range does the 3923 cross over?

Thanks for all of the help,
Aaron

 

I'll see what I can dig up for you file wise. I've got C-com on this machine but I don't use it for tuning. Misplaced my damn USB storage device and thats the link between this machine and the laptop.

The AE stuff is ms pw added so your injector size is going to change the amounts. Curve shape should help you out.

The 3923 looks like it's crossing over to a 6 series plug in the NGK series. Personally, I think it's a little colder. I've got a friends car that I tune - 11:1 383 that I use 3924's in NA and use the 3923's for 150 hits of nitrous. It looks like there's a 3922, which'll be even colder.

 

SloR,
Thanks for the info. You were correct in that the local O'Reilly's had both the Autolite 3923 and 3924 spark plugs. Even though the 3923s had the removable tip (wire side), I oupted for the slightly colder plugs. I will install, and see if I can get some better readings. As for the NGKs, there were no numbers that matched the detail we have discussed. They cross referenced the Autolite number and came up with the same number for the NGKs. I went ahead and spent the $12 for the Autolites.

I would be real interested to see the AE curves that you may have. I will tell you that on every shift, it goes lean (14.5:1), then goes very rich (9.5:1). I had always thought that this was due to the lower rows in the VE tables being lean, and then the large shot of AE due to the TPS and MAP changes on a standard car. Maybe lowering the AE curve is not the right direction. Interested to see your thoughts.

I will say that the tune dynos very well, but that is steady state pull in one gear vs actual driving hard through all the gears. It also has great part throttle manners. I am just so tired of the "plume" after the car and the "black specs" on the rear bumper when you are hammering on it.

Thanks again for the help.
Aaron

 

From the sound of it, I'd say you're on the right path with pulling out some TPS AE. You should try to steady state tune the cells where you end up on the shifts. Then you'll really know. I've heard of people disconnecting the pressure side tubing from superchargers and turbos and tuning the lower part of the map that way. The wideband correction is another thing that can mess you up. That's relying on feedback so it's always a step or 2 behind where you actually are. Same thing with looking at fueling on a datalog. Look at your VE values as you transition through cells. Think whole picture rather than focusing on just single points.

I got your email. I should be able to get over to Staples one night this week to get another USB storage device to send you a couple .GCT files along with corresponding .log files. If you want to send me any of your stuff I'd be glad to take a look at it.

Paul