Your tuner can use his Tech II to moniter exactly what the engine is doing, which should give you some ideas, but if it's pulling timing down to 15 deg, then something is telling the ECM to do that. I would suggest looking at IAT and go from there. If it thinks the IAT is too hot it will detonate, and the knock sensors pick it up and tell the ECM to pull out timing. Also, what's your coolant temp?

Ed

 

My A/F ratio was at 11.8 I believe. I have no idea what it could be then. Sorry man. Jeff did the tune on my car and he was great.

 

watch what on each cylinder? as far as I know afr can only be looked at on a bank basis left or right. what else can be looked at to check that each injector is working properly? as far as I know the only sure way to check each injector is to have them tested outside of the car.

But then I learn something new every day.

More Than Zero

 

Alky injection would keep your engine clean, and get rid of your knock, but you do need to figure out the origanal problem.

 

Doug,

I would definitely entertain the idea of installing alcohol since I am running non intercooled.

However, like you said, I need to cure the problem first. I'm trying remove one doubt at a time.

Thanks,

Mark

 

Mark,
I once had a car in here with a mag that had the breather/pcv lines hooked up incorrecly. It was sucking in a fair amount of oil but not enough to smoke. Oil consumption can couse a knock condition. (it was not installed here of course )

Just some food for thought, good luck

 

Doug,

I appreciate it. I realize that any responses made are suggestions so I'm not out there running to the car doing every adjustment made but it gives me as you say "food for thought". It may be something simple or stupid but you have start somewhere.

Mark

 

Mark, add octane to the gas and see if the knock goes away. If so.. then its an octane issue.

There is a product called GM Top Engine cleaner that can be used for breaking up any carbon deposits on top of the pistons. If you run this product, change the oil afterwards. On the turbo buicks we pour it down its throat while reving the motor.. you'll get tons of white smoke exiting the tailpipes. Some actually run it through the PCV hose while reving the motor. Dont know if this is safe to do an LS1.. just food for thought.

Also you didnt say what gasoline and its octane your running.

 

Julio,

I agree and disagree. Higher octane may make the detonation go away but I fear that may be nothing more than a band-aid to cure the problem. Something other than low octane could be causing the detonation, don't you think?

As far as the top engine cleaner, that's funny. I had just gotten off the phone with one of my friends who works as a tech at a dealership and he just told me about it. We decided that we were going to wait until I could take a look using the bore scope and see what the top of the pistons look like.... if they're in really good shape, there's no point in adding something that acidic into the engine.

I've been discussing fuel and different brands. I usually run Shell or BP. There's a Texaco that was on the corner and the night before the dyno, I realized I was really low. It was late so I stopped in there. Well, apparently it had been bought out by Kangaroo??? WTF??? I needed the gas so I filled up. The more I think about it, the more I'm wondering how crappy any station selling Kangaroo gas may be.

I'm going to add some 100 octane today, I'll add about 5 gallons and see if that helps.

When I actually go back to the dyno run, I don't want to be on anything higher than 93 only to have it ping once I fill up using everyday gas.

Thanks for the help, I'll post what I find with the bore scope today.

Mark

 

Not all knock picked up by the sensor is detonation. Any metalic sound eminating from the motor can cuase a knock sensor to flare. Even simple items like a serpentine belt tensioner can cuase the sensor to flare up.

The issue of octane is to assert the problem is just that. Get the tank very low and drop 5-6 gallons of 100 octane.. then put the scan tool on it.. see if it clears up. If it does, you have 100% everything is ok.. If the knock doesnt go away with octane.. then you have something to look for. I have seen a lot of weirdness chasing knock issues on customer's cars. The strangest was a cracked flexplate, and an air intake pipe hitting a bracket.

So your question of 93 on the dyno.. man I tell ya. I would have way higher octane in the tank... If that works. Have the shop drain the fuel system on the rail, and put 93 in the tank.. then retry. Would suck to put the car on rollers and the knock issue continues on 93.. cuase then your back to square 1.

HTH

 

I agree that the knock sensor can pick up other things to "think" it's detonation but you can clearly and physically hear it detonating.... so in this case, it really is retarding the timing for a reason.

Okay, I understand the logic behind that. Sorry, didn't understand. Yes, that makes perfect sense.

I'll keep ya posted once I get a few things straight.

Thanks,

Mark

 

I was getting really bad detonation when I had my mag installed. Turned out to be the engine running hot. Check your rad for obstructions

 

When you say hot, how hot is hot? I'm running at 190-194 and am told that that's too hot for a charger. I'm going to install a 160 thermostat and redo the ECM to see if it'll lower temps.

Mark

 

I'm no guru, but for what it's worth, on an LS1 I think 15.x timing and 11.2 AFR, around 5000rpm is about where you should be with a Mag. Headers dont change the MAF but will reduce the intake pressure and thus lower the MAF utilization.

With the 3.3 inch pulley you may be running out of fuel and thus unable to run under 12 AFR. clamping the fuel pump voltage to 15VDC fixed this problem for me. the kenne bell Boost a pump is a kit version. If you have 39# injectors go bigger.

But then again I could be wrong.

 

Thanks depot but I switched back to the 3.5 and according to Magnuson themselves, they suggest 19-21 degrees. As far as AFR, at 11.2 at 5Krpm, the thing was soooo rich, it was blowing smoke... I guess each sc has different requirements.

Mark

 

This is not a direct answer but more of a catalog of possible issues to past F.I. setups that was KR-free at first install, then KR issue arises over time.

First of all, non-IC'd blowers/high compression ratios/pump gas have a thin tuning window even at moderately low boost pressures. I've also experience KR-free running at blower bolt on then KR becoming more prevalent as time progressed back when I had my non-IC'd Vortech A-trim on my '95 T/A.

The following is a list of possibilities that each my not be an issue to warrant action, but when combined will really thin out the tuning window. The best response short of addressing real mechanical/electrical issues (if they exist) is to intercool to restore the width of the tuning window.

1.) Carbon desposits. But on stock hypereutectic piston lower ends, the engine stays fairly clean and OEM valve seals last long. PCV and ring issues not withstanding.

2.) Valve seating surface degradation. Ever wonder why high mileage cars under stress often fail from burned exhaust valves? The valves loose their surface area of contact with the head. This increases thermal resistances in the thermal flow path. The exhaust valve gets hotter. So ever car over time will have a gradually hotter and hotter exhaust valve for given operating conditions because the valve cannot reject heat as well as one just after a fresh valve job. A few degrees hotter exhaust valve (possible starting point for abnormal combustion) + carbon deposits will thin out an already thin tuning window of a non-IC'd blower on a high CR engine and pump gas.

3.) Fuel pump degradation. You tune the setup for X air/fuel ratio at install. But over time as fuel pressure degrades just like treadwear wanes on a tire. It's possible that after a few dozen thousand miles you'll be 0.5 or higher air/fuel ratio. Look at Alternative Auto's website for one of the best F.I. tuners. He sacrifices 30-50hp to compensate for this factor! My motto is if one wants to be 11.8:1 50,000 miles post install, you should tune for 11.0:1 at install. Gradually leaner A/F ratios at **open-loop** combined with hotter exhaust valve + more carbon deposits will really make a thin tuning window of a non-IC'd blower on a high CR engine and pump gas.

4.) Alternator degradation. Ever see the gradual drop in voltage output of an alternator over time. This in turn drops fuel pressure and compounds the natural degradation of the fuel pump. I've lost 25 psi of fuel pressure at idle due to a failing alternator personally. Combine this with 1, 2, 3 and you've got a recipe for engine rebuild after a few oil changes.

As I said, it's most likely a combination of above and all 4 above happen to 100% of cars out there over time. The thin tuning window of even a moderately low-boost non-IC'd high compression pump gas setup means the window will vanish with even a slightest combination of above. On NA, octane-boosted, or intercooled setups, the above wouldn't even be an issue because the wider tuning window can absorb those natural car&motor-aging artifacts.

Also when tuning, do not tune near the edge. You'll end up having to constantly retune the car/monitor it as it ages and pay a be-back visit to tuner even though it saw 0 KR previously. Tune it conservatively and the car's aging will naturally take up that tuning window slack as miles roll by but not enough to cause headaches.

 

Staged,

Thanks for the response. I agree on all that but just for the record, everything was pretty well in the "middle". I didn't want to push the envelope since this is a daily driver and like you said, I don't want to be returning to the tuner due to degradation of components as the car gets older. The car just turned 40K miles so as of yet, I don't think there is too much wear and tear on it.

As far as carbon build-up. I used a scope to view the tops of the pistons. (It took me 3 tries, the first 2 times, the flashcube on the camera broke off in the sparkplug hole...lol) Seriously, the scope showed the tops of the pistons and there was basically nothing there... very clean.

I think for now, I've got 3 changes before I go to the dyno Friday.

1) higher octane fuel
2) relocation of IAT sensor
3) 160 thermostat (currently have stock 195)

We'll see where that goes...

Thanks,

Mark

 

Yup/ Like I said, the tight wall clearances of stock gm pistons admit very little oil on cold start-up. I like your other suggestions too. Still I'd think about charge air cooling (retro IC kit or AFTER-BLOWER spray).

Good luck
Eric