Lets talk about my KR (update 11-28) - Page 7 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 11-24-2007, 02:56 PM   #61
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I'm suspecting your IPW numbers from the scantool. IIRC, you're using the CP9110? It has some wierd flukes. I can compare IPW'* on mine later today and see if it reports correctly.
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Old 11-24-2007, 02:59 PM   #62
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Yea, that is what i am using.

Yea, if you dont mind, see how yours reads. I have been told before that it does not read them 100% accurate and they are actually good til 25 ipws but i am unsure.
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Old 11-24-2007, 06:17 PM   #63
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if you whant to compare a few of mine

IPW 18 to 19 max
o2 905 to 920
maf frequency 8970 max
ign advance 27 max at WOT
LTFT +16.4 at WOT
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Old 11-24-2007, 06:28 PM   #64
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I am just waiting for Ryan to get back a hold of me. I know looking at my scans my car is looking for more fuel. Not sure if it is tuning, injectors, pump, ect. But it seems to be looking for fuel.

I think deep down Ryan beleives it is false knock. On the last email he wrote, if this doesnt cure the kr then i believe it is a bad knock sensor or a mechanical noise. I mean it may be but i dunno. I think the car is crying for fuel. And O2'* being that low, i can see why.
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Old 11-25-2007, 02:41 PM   #65
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Quote:
Originally Posted by willwren
There'* NO WAY you are outflowing stock injectors.
Using the industry standard injector/hp calculations, 21lb injectors will only support about 200hp; this assuming a maximum duty cycle of 80% and an engine with a Brake Specific Fuel Consumption of 0.50. Is it possible to force the injectors to support more HP? Sure, but you need to increase the duty cycle or the engine has to require less fuel to make each HP. So, in fact it is very likely he (TJ'sblackbonne) is in need of larger injectors for his application.

Secondly, the Series 2 SC injectors' flow rate of 36lb/hr is based on a maximum fuel pressure of 60psi. If you scale this back to the L36'* 48psi, then the actual flow rate of these injectors on a L36 system is only 32lb/hr. The computer can be easily tuned for this.

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Check your plugs again too. You should be reading them on a regular basis.
Reading plugs is great for carburated engines, but in an EFI system with O2 feedback, it'* a little more tricky. The reason why is because the computer is going to force a 14.7:1 or leaner AFR any time other than PE (power enrichment, or WOT) which will result in the plugs looking like they are running lean; unless you shut the engine off immediately after a WOT run which isn't a good idea. In most EFI applications the computer will shut off the injectors during decelleration or command a very lean AFR which will "clean" the plugs after WOT operation anyway. The absolute BEST way of determining AFR on an EFI engine is by use of a wideband O2 sensor.

Having said that the spark plugs can still tell you a lot. They can tell you if they are the correct temperature range for the engine or if there is detonation occurring. But I would not rely solely on their appearance to determine if the engine is getting enough fuel at WOT.

Now that I have explained all that, here is what I think is going on with TJ'* car. There is absolutely NO reason why he should be getting any detonation on a free rev of the engine. There is no load on the engine so there shouldn't be enough heat in the combustion chamber to create detonation. It is FAR MORE LIKELY that he has a mechanical noise in the engine that is causing his KR issue. In this latest chip I did for him I reduced the ignition timing in some places by 5 degrees which doesn't seem to have helped his KR issue at all. So I am inclined to believe the root cause of all this KR is due to a mechanical noise or other issue that isn't true detonation.

Now I will admit the latest fuel numbers don't look all that great either. Should see narrow band O2 voltage readings in the 800'* at WOT; not 700'* or 600'*. The IPW'* of 22ms he is getting indicates to me his injectors are maxxed out for this application, and he is in need of bigger injectors. Could the lean AFR cause detonation? Yes. But this still doesn't explain the KR he is getting on a free rev; even with lean AFR it takes a lot to get an engine to detonate on a free rev with no load on it.

First thing TJ needs to do is check fuel pressure at WOT. It should hold at his maximum 48psi during the entire WOT run and should not drop off. If it does drop off, this could indicate a restriction in the fuel system or a problem with the pump not being able to keep up with the flow demands @ pressure that is required of it. If, in-fact his fuel pressure is steady during WOT operation, then I think it'* safe to say he needs bigger injectors. Are Series 2 L67 injectors a little excessive? Maybe, but if he can get them for a good price then we can tune the computer to work with them.

I suggest we get the fuel hammered out first and then look into the KR issue. As I mentioned before, a lean AFR at WOT can lead to detonation; and we already know we are in need of more fuel right now. Once that problem is solved, then we can look into this KR issue more. But I still fear it is false KR and not actual detonation.

-ryan
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Old 11-25-2007, 04:44 PM   #66
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Correct my numbers if I goof something here. I know quite a bit, but I'm certainly not an expert in this:


The OEM Bosch injectors in TJ'* car are rated at 21lb @43.5psi (3bar). The L36 actually has a 3.5bar regulator, which increases the flow to 22.6lb/hr. BSFC numbers should be higher for that rating.

L36'* are notoriously under-rated at 205hp from the factory, so how can that OEM injector only support 200? Granted, TJ has a cam in that car (I keep thinking ER rockers, but that'* the other), so the question is do other L36'* running the ZZP GT1 cam have this issue? If they do, isn't the S2 L67 injector just a bit on the monstrous side, and wouldn't an injector like the 29lb S1 L67 be a better choice? Particularly at 3.5bar fuel pressure?

If I'm not mistaken, the L36 and S2 L67 both run at 3.5bar (50.7psi). But the Bosch injector rating is based on 3bar (43.5psi).
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Old 11-25-2007, 11:40 PM   #67
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Quote:
so the question is do other L36'* running the ZZP GT1 cam have this issue?
in a other club im in the a guy whit a f body L36 that has Kr in the 16 to 18 after a cam swap so TJ not the only one




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Posted: Thu Sep 28, 2006 10:31 am Post subject:

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After I did a camswap I got swamped with 16-18 degrees of KR on my n/a RWD platform

So n/a cars are very apt to get KR, and often times the autos will get it a lot worse than the manuals (atleast that is usually the problem on f-bodies) after engine work.
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Old 11-26-2007, 12:11 PM   #68
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Quote:
Originally Posted by willwren
Correct my numbers if I goof something here. I know quite a bit, but I'm certainly not an expert in this:


The OEM Bosch injectors in TJ'* car are rated at 21lb @43.5psi (3bar). The L36 actually has a 3.5bar regulator, which increases the flow to 22.6lb/hr. BSFC numbers should be higher for that rating.
Every L36 regulator I have seen has a 3.0bar stamp on it, not 3.5bar; but I will admit I haven't worked on too many L36'*. All of the S2 L67'* I have worked on have a 3.5 bar regulator. But lets assume for a moment what you say is the norm...

22.6lb injectors will support up to 217hp at a 80% duty cycle. Like I said before, you can drive the injectors at a higher duty cycle, but the accepted industry standard maximum recommended duty cycle is only 80%. Also, if your engine is more effecient than the "industry standard" 0.50 BSFC rating, then the engine will be able to make more power with less fuel. The numbers I gave you are based on calculations using industry standard values for duty cycle and BSFC. Actual conditions you experience may vary from this. But this is what the rest of the industry uses so that'* what I use. You can read a complete write-up on this subject here: http://www.precisionturbo.net/techinfotext.php?aid=22

Quote:
L36'* are notoriously under-rated at 205hp from the factory, so how can that OEM injector only support 200? Granted, TJ has a cam in that car (I keep thinking ER rockers, but that'* the other), so the question is do other L36'* running the ZZP GT1 cam have this issue? If they do, isn't the S2 L67 injector just a bit on the monstrous side, and wouldn't an injector like the 29lb S1 L67 be a better choice? Particularly at 3.5bar fuel pressure?
I haven't seen enough dyno tests to confirm nor deny what you are saying about the under-ratining of the L36. But what I can tell you is not all cars are the same regardless of what mods they are running. I have seen some bone stock L67'* run fat (rich) while I have seen others run leaner at WOT bone stock, with bone stock programming. What'* the difference? The day of the week the car was built? Can't tell you that. But what I can tell you is just because someone else'* car does something doesn't explain why TJ'* car does something else. I have been tuning for over 8 years now and I have seen two very identical setups require very different timing and fuel tables. My concern is what TJ'* car is doing and not anybody else'* is. Perhaps TJ'* engine is simply requiring more fuel to make the same amount of power (BSFC) than what other peoples' engines are. Efficiency of the engine is something that is not easily measured and can differ significantly from one car to the next.

Having said that would a S1 SC injector be a better choice? Sure; but how easy is it going to be for TJ to find a good used set that doesn't have a million miles on them? You can find S2 SC injectors all over the place that don't have a ton of miles on them for cheap. And as I mentioned earlier, these don't flow all that much more than the S1 SC injectors. As long as he doesn't go with too big of injectors I should be able to tune the computer to work fine with them.
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Old 11-26-2007, 12:36 PM   #69
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Every L36 Regulator I have seen was 3.5 Bar.. That would be for my factory motor... It was 3.5 Bar, The replacement was 3.5 Bar... The replacement engine I used had a 3.5 bar and the extra fuel rail I have is a 3.5 Bar... 3.0 Bar would be in the area of 42-43 Psi and the L27 would fall into that category as it runs 41-47 Psi... 3.5 would fall to the L36 as it runs 48-55 Psi..

I would assume that my LN3 would be 2.8 as it runs 37-41 Psi


Being that you have removed the timing and there was no change... I as well would like to see TJ with a little more fuel... But I am almost thinking he may have some internal issues... Remains to be seen..

TJ How is your fuel pressure holding up?

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Old 11-26-2007, 07:34 PM   #70
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Havent had a chance to get on a fuel pressure gauge but hopefully sometime this week.


As for the injectors, i got low milage S2 L67 injectors for an awesome price (because we have great members). The chip is going out for tuning for them this week and should be back soon enough and i will put them in. It cant hurt.


Lets hope it isnt something internal causing this. I am also going to switch out the knock sensors with the other ones i have. I figure might as well try it. Any ideas on things that maybe causing internal noise?
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