Sometimes, after coasting down using engine braking for a stretch, I get back on the gas, and at that moment, or shortly thereafter, maybe around 2000 or 2500 rpms, I hear something that might be confused for light detonation. Its hard to describe it. You hear it faintly for a second when you get back on the gas, but it goes away in a second. And, when it occurs, it ALWAYS occurs WAY before any boost is made, like I said, down around 2k or 2500 rpms.

So, I dont see how this could be in any way related to my Supercharger setup. Because it happens under very low load, I dont see how it can even be detonation. It sounds maybe like a slight hiss. Or, it might be described as a couple of bbs shaken up in a small coffee can. Now I know some people describe detonation this way. But I just dont see how, with only 2-2.5k rpms being made, and well before any boost is made, it could have anything to do with knock. BTW, when I say I get back on the gas after engine braking, Im not even talking about flooring it. Im talking about a mild increase in the throttle, not to the floor, but to maybe half way or so. Ive never heard of knock occuring this way. So it must be something else. Ive just wondered what it might be... One of those unexplained little idiocyncracies or something.

Paul, sounds like detonation to me. An easy way to tell is to dump in some race gas or toluene and see if it goes away.

I hear about this all the time.

How the heck can you tell what it sounds like?

Over the sound of the SC and my track pipe/exhaust I don't think I would be able to hear that.

>>Paul, sounds like detonation to me<<

But how can a car, which doesnt detonate at all under full boost, produce detonation at really minimal load, like at 2000 rpms, with 1/4 throttle??

>>How the heck can you tell what it sounds like? Over the sound of the SC and my track pipe/exhaust I don't think I would be able to hear that.<<

See thats my point. At 2000 rpms at a quarter throttle, there IS no SC noise. There IS no boost. Theres nothing but low throttle, light load operation. I just dont see how the car could be knocking on 93 octane, way before it even gets into any boost at all. Conversely, when Im under boost, I never hear a damn thing except the sheer power of the thing. It must be some kind of hiss that the breather valve, or vapor separator is making or something.

What karl told me is detonation sounds like glass breaking, he said the best way to hear it is the windows up and the radio off.

>>What karl told me is denoation souds like glass breaking, he the best way to hear it is the windows up and the radio off.<<

Ive heard detonation in the past...Plenty. Back in the '60s and 70s, cars knocked all the time. IT wasnt even that unusual for a car to have run-on issues. Know what that is? Thats when you turn your ignition off, and the car just keeps trying to idle, roughly, and sporadicaly, spitting and farting, but it wants to keep on running. Real shitty for the engine. But its a form of detonation. Before electronic ignitions, most cars seemed to detonate some. The kind you heard the most was when you stepped on the gas hard, and the engine just would sound like it was gurgling loudly during the first part of your acceleration. Knocking is a good description of how it sounded. Well, mine doesnt sound like that. Its much more subtle. It sounds more like a hissing, making me think its valve related.

Knock in our cars, boosted, is caused by overloading the engine due to too lean a mixture, too much timing, and too much load for these values. At 2K rpms, under light throttle, with a way conservative state of tune thanks to Dinan, there just arent any parameters that I have which would cause detonation under the conditions Im hearing this.

Paul, tip-in detonation is hardly unheard of. You're transitioning from the injectors being 'off' to them getting back in on the action, and if they aren't responding in time you may have a temporary lean condition that results in knock. I spent LOTS of time fiddling with this on the TEC-II, and you have to get the acceleration settings right to prevent it. Now, the stock ecu has different areas to address this, but you still have to accomodate for the transition point. The point is, just because it's not under boost or under heavy load doesn't mean you can't have detonation. If you had an AFR gauge you'd tell easily enough, but the EGT probably isn't fast enough to show you anything. Perhaps you can wire up an LED or a speaker to the stock knock sensor to see if it picks anything up?

Originally posted by RyanC
The point is, just because it's not under boost or under heavy load doesn't mean you can't have detonation.

Ryan hit the nail on the head. Lots of cars have detonation under tip-in or low-rpm conditions. You shouldn't assume that just because you're not under boost means you can't have detonation.

>>The point is, just because it's not under boost or under heavy load doesn't mean you can't have detonation<<

Ok...well, now what! Its not like we go to Dinan and say, Hey, you use conservative tuning for load conditions, but what about this tip-in issue? Whats likely to be the result of doing nothing? Would changing from 93 to 94 octane, which is available via sunoco, make any difference? Otherwise, I dont see much to be done about it.

I mean, its just sooo ironic. I spend all my detonation related thought on making sure Im not leaning out under high load, with egt and boost gauges, and dyno runs showing afrs, and so forth, and then whats turns around and bites me? Lousy 2000 rpm light acceleration! Damn this is one ironic field.

Another thought...I just remembered isnt this under closed loop control? Then why isnt the dme compensating for it? Does it mean im losing timing at part throttle due to the knock sensors likely responding to this? And again, how can I be lean under closed loop......I thought the whole point of closed loop was to maintain lambda 1. Hmmmm....Am I not in closed loop as I transition from engine braking to light throttle?

Paul,

" Hmmmm....Am I not in closed loop as I transition from engine braking to light throttle?"

When you are engine braking above a certain RPM (usually around 1900ish) your fuel injectors are off. IOW, your engine is just spinning down, it isn't burning fuel. If you check your mixture you would see you are extremely lean.

"And again, how can I be lean under closed loop......I thought the whole point of closed loop was to maintain lambda 1."

When you are at lambda = 1 doesn't mean you can't have detonation.

"Its not like we go to Dinan and say, Hey, you use conservative tuning for load conditions, but what about this tip-in issue? "

Why not? You paid a lot of money for their kit. On the flip side you altered their kit so they may not be very helpful.

Shawn

>>Why not? You paid a lot of money for their kit. On the flip side you altered their kit so they may not be very helpful<<

Big deal.. .If I thought theyd do anything about it, Id just slap on the stock belt and pulley....Before I start jumping to conclusions, maybe its a bad tank of gas...I'll first try 94 octane, and another brand. If it continues then I'll call them. But Ive never heard of them doing a special state of tune for somebody. Thats not to say that if I pressed them on it, they wouldnt say, 'ok, so youre one of the few that are having these tip in detonation issues....we do have a special program for guys like you, and we'll upload it to your dealer right away...'...I mean, it Could happen. But it would knock me over if it did...

If it's the software that's doing it, they should, by all means, resolve any detonation issues. On the somewhat brighter side, you're less likely to frag a piston or break a ring land by detonating under low load than under high load, but it still isn't a good thing.

>>If it's the software that's doing it, they should, by all means, resolve any detonation issues<<

Guys, Ive had this kit for 3.5 years. I suppose it could have been doing it from the beginning, but I think not. I would have heard it. Its fairly recent im pretty sure. Thats why Im thinking maybe gas. But what might have caused it to come on in the last few months, say. Couldnt be software with this recent development. Wonder what else it could be...Of course, there's still the chance that its not detonation. But if it were software related, at tip in, I would have thought it would have been there all along.

Paul it may be time for dyno tuning. You also may want to consider an aftercooler setup. You are still running a large amount of boost for no real intercooling. Water/alchy may not be enough, and is not effective under low rpms...

Greg, I agree that it might be good to persue an intercooler. Although Im far from thrilled about our choices. So far as this tip in detonation is concerned, if thats what it is, I dont see where my 'large amount of boost' would have anything to do with it. Not only do I not see a large amount of boost at 2-2.5k where I hear the sound, I dont see any boost. I think we can remove boost as a factor. Ironically, when boost Does enter the picture, so does winjection, and there is no knock that we can hear, or feel, by way of timing retard or elevated egts etc. Its only a down low, tip in condition. I like the explanations having to do with the idea that the injectors are slow cycling from no flow to flow, as in the case where the noise is heard, ie, from engine braking with no throttle, to light throttle. Certainly, not a boost related situation. But if it were software related, I would think I would have heard it right from the start, not just in the last few wks or so. I think I'll get out my scantool today, and look at some trim values, and some timing values, and see if I can see anything right at tip in time.

Could it be a bad batch of fuel. Someone above mentioned putting in some race fuel. That may help. Try some injector cleaner too.

On a side note, have you checked your coolant for oil, and your oil for coolant? Just as a precaution. You may have a bad gasket.
High boost will eventually make the stock gasket leak... This could cause some idle traumas...

Thanks Greg. Ok...No oil in coolant; no coolant in oil, thank goodness. I had a half tank left of Sunoco 93. I went to a different pump at the same station, but this time filled it up with 11 gallons of 94 octane. So, I 11 of 94, and about 5 of 93, and guess what...It went away! It must have been a bad tankful. I used to use Techron, but lately, I havent used it in 8K miles because Ive always been told that Water injection steam cleans the fuel system, and the cylinders, pistons, plugs, and injectors all look sparkling clean compared to non water injected cars. I'll put some in anyway. Thanks for the tips..

:redspot Thank god!
I always run 94 no matter what!

Happy motoring!

G:cool:

lol,
I always put 95oct.
And guess what... it cost $0.15/gallon
jejeje

P.D: I live in Venezuela, thats why

Paul the water injection will clean the valves and combustion chamber better than any fuel additives on the market.

But it will not clean the fuel injectors and the techron might be cleaning the injectors when you need it.

What I use is the RED LINE Complete Fuel System Cleaner SI 1. Pour the bottle in the tank and then fill it up with gas.

From there I take that empty bottle and then fill enough for 20gas and leave it in my trunk and with every other fill up I pour that into my tank with every fill up.

Redline are very good products. This way the water injection cleans the valves and combustion chamber and the redline the injectors.

http://www.redlineoil.com/products.htm

>>From there I take that empty bottle and then fill enough for 20gas and leave it in my trunk and with every other fill up I pour that into my tank with every fill up.<<

Hi Mark. Thanks for the tip...Any reason you prefer the redline to the pure techron? BTW, what does this mean?? I cant make sense of it.. what is '20gas'?

Thanks.

Paul each bottle is designed to treat 100 gallon of gas.

There is a marking on the bottle in increments of 10 gallon sorry for the confusion.

I just pour to the 20 gallon mark in the spare bottle sorry about the mis typo :)

The redline is one of the best and it also works out cheaper than the techron especially when you use it on a constantly basis between every full up.

>>What I use is the RED LINE Complete Fuel System Cleaner SI 1. Pour the bottle in the tank and then fill it up with gas.
From there I take that empty bottle and then fill enough for 20gas and leave it in my trunk and with every other fill up I pour that into my tank with every fill up.<<

Mark, I must be exceedingly dense this morning. Taking this literally, what it says to me is that you buy more than 1 bottle of the stuff. Then, wnen the gas is near empty, you pour one complete bottle into the tank and fill it up. This gives you a spare empty bottle. Then it sounds like you take one of your full bottles, and pour off 20 gals worth into your empty, and keep that in the trunk, for use every other gas fillup. You keep refreshing your empty so that ther's always 20 gals worth of redline to use, with every other fill up.

But what Im not seeing is why you pour the whole 100 gals worth into your gas tank at one time. Isnt that overkill? Is there a danger of using too much of the stuff this way? Or am I just taking your 'method' too literally.....Or, were you not clear ....

Not trying to bust your chops...Honestly........thanks.

The reason Redline recommends you pour the entire bottle the first time is if your injectors and valves are dirty it will clean them to almost a 98% eff.

If you feel that you injectors are good then you do not have to pour the entire bottle in but since you have not since 8k then I would at least 50% of that bottle.

By using the smaller amount it keeps the injectors and valves constantly clean. All I use the redline is for peak performance of the injectors and the w/a cleans everything else.

This is my old cylinder head and new one. You can see how clean the exhaust ports are the first two was where the head gasket was leaking.

The w/a steams clean it right down to the metal just like when you pull your spark plugs mine are completely clean no deposits what so ever.

Wow...what a difference. I dont think any local stores carry it, so I'll have to order it via mail order....Im searching for a source right now. I like your method. I'll go with a whole bottle first time too. I just wanted to make sure you werent hurting the engine by using like 5 times what they recommend. I didnt realize thats part of their directions. Thanks again. Why the head change. Did we talk about this? If so, forgive my sieve of a brain. Did the leaky head gasket present any problems you could detect?

When I had my car on the dyno last year we ran it with the motor cold jackass that owns the dyno was running 2 1/2 half hours behind I had the hood open and when it was my time to run touching the motor it was completely cold. (Oh No )

After 3 dyno runs the motor was so cold that the oxygen sensor was not even warmed up as my split sec a/f gauge was not even moving Argg. :mad:

Normally I only boost when the motor and oxygen sensor if fully warmed up as the metal expands and make better contact. It was three years I had it with out any problems and would have none if I let the motor warmed up properly.

Then four days later heard a vacuum leak ticking at idle and the car began to idle bad. :95

When my mechanic pulled the head and sent it out to get it check they noticed a two hair line crack and did not know if it was there before.

I did not want to take a chance and use a used one or the old head to find out that over time that I may have problems. So I bought a new one and got the valves cut and match port the exhaust ports and manifold to the gasket.

>>
I did not want to take a chance and use a used one or the old head to find out that over time that I may have problems. So I bought a new one and got the valves cut and match port the exhaust ports and manifold to the gasket<<

Do you have to have all that done when you buy a new head? Did you think about using the opportunity to lower your compression and go for some more boost or anything like that? Did polishing and porting the head give you any extra on the dyno?

later...

Do you have to have all that done when you buy a new head? Did you think about using the opportunity to lower your compression and go for some more boost or anything like that? Did polishing and porting the head give you any extra on the dyno?

later... [/B][/QUOTE]


Yes I did everything when the head was off and I would have went with the Bmp lower head gasket but they did not have in stock and said it would be several weeks and I could not wait that long so I went with the Bmp stock compression gasket they are alot stronger than stock.

I dont know if it is the angle valve job or the exhaust porting to the manifold or both but the midrange to top end you can feel the motor is stronger there is more torque it pulls harder.

I ported just the exhaust side. After reading about porting the intake head it would have to be flow tested for best results I could not bother with the extra expense and time. I did not think that there would be a big benefit as the intake runners are plastic and there would be a velocity loss from the intake runners going from smaller to larger opening (cyl head) maybe I wrong here.

I have not dyno the car since but I will. The motor feels stronger from 3500rpm+ compared to before at the same boost settings.