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Hi,
Already a good few weeks the mechanic has a problem in fixing the serial LT4 with the lower pulley IW 18% and full halltech intake. The fuel pressure drops at high engine speeds. Surprisingly, the meter was able to measure, but it is very unsatisfactory for me ...
I have also logs in. hpl format recorded during rides where you can clearly see a drop in fuel pressure, but the file is slightly too big to upload here.
Hey OP, a few others and myself can run the stock tune out of fuel at 150mph without a pulley.
p228c and p0089 are the codes you are throwing, i know
Stock tune runs too rich, and the low side cant keep up. Your air is 700hp worth, but the car commands over 800hp worth of fuel to try to run rich.
Low side pump cant keep up.
One possibility if you want to keep your stock tune and warranty, is to install a separate low side pump and Y into the low side fuel line... have that pump be boost actuated at a certain boost pressure using a hobbs switch.
Otherwise, as the other people suggest, you need to tune your car. The tune will solve it... and will also void your warranty. If you dont care about warranty, then absolutely tune your car man.
It's not the tune. The stock tune is surprisingly lean, commanding an AFR of 12.6, much leaner than you'd expect for a supercharged engine. You're running out of fuel on the low side pump and need an auxiliary low pressure fuel system.
.... or he can tune it, and he will have enough fuel. How do you think the 757 callaway runs on the stock pump? They have the AFR in line with where they should be instead of so rich as the stock cars are.
He is not too lean currently, he is far too rich.
There are users on this forum who have had the same problem with their callaway 757 cars, and callaway sends the tuner to their house, and the cars are fixed and run strong as death.
No pump is needed if he goes the tune route.
Users Salcolkat can confirm what I am saying is true.
To the OP, the User above me has an air intake that cheats the MAF, and his car runs slightly lean at very low RPM, but then his car comes back to rich, ive looked at his dyno sheets before, and he and I have been round and round about this, no stock tune car runs lean, it either runs rich, or it runs out of fuel pressure and shuts down.
Stock tune cars match the air coming past the MAF with EXTRA fuel. The only way they dont is when one cheats the MAF.
User above will never understand or agree with this apparently. Please dont for a second believe your car is currently running lean. It is running rich, and running past the in-tank fuel pumps ability to pump.
Your high side pump is fine.
A good tuner will solve it all for you, no fuel pump needed.
You can't tune out a lack of fuel. If your fuel pressure is dropping you are asking for more than the low side pump can deliver. There is no tune in the world that can help that. The stock tune runs leaner than the earlier tunes because this is a direct injection engine, not port injection. It only runs rich (stock) when it goes into COT.
To the OP: Ask any of the reputable builders/tuners, they'll tell you the same thing. Add an auxiliary low pressure fuel system, or methanol injection, THEN try tuning from there.
dude... in the stock tune, the cars request more fuel than is needed.
But IF Instead, by requesting less fuel, and running proper AFR, the low side pump is no longer out paced by the high side pump... the high side pump is no longer commanded to pump so much with a proper aftermarket tune. AFR become normal at that point instead of rich. This is done via an aftermarket tune.
The stock tune cars run rich, and the tunes prove it. You are the only one who will sit and argue instead of call callaway and see if im lying. 757 cars run on stock fuel pumps... flowing more air than our cars do with their 2300 bigger blowers. But the 757's don't run out of fuel, because they are not running the rich stock tune... their AFR is tuned more lean than GM's rich stock tune... especially when COT comes on.
The op's 18% pulley is not causing the stock blower to flow more air than a 2300 on a 757 callaway. The fuel system CAN keep up fine on the OP's car with an aftermarket tune... especially if he does norcal catless pipes and has his tuner disable COT (aka, run rich mode).. then he could make 800hp safely, instead of only 757.
the stock tune does command a lean power enrichment lambda and it does run very rich when COT kicks in.
the problem is it basically runs in COT mode almost constantly so it really doesn't matter what PE is commanded until COT is disabled.
the pulley exacerbates the problem by leaning out the mixture and causing fuel trims to go positive which carry over to PE during the part throttle to full throttle transition and command even more fuel at WOT/PE/COT and run it out of capacity.
first you tune the car, then you upgrade the fuel system if needed.
higgs, when the car is cold, that is the only time it runs lean, or when a person is in vacuum.
Otherwise, at WOT, once at temp, the car is ALWAYS running very rich on the stock tune.
COT mode, the car is running EVEN MORE rich. +800hp worth of fuel rich to be exact.... which is when the low side pump falls on its face. High side CAN pump over 800hp worth of fuel, low side cant supply the high side.
Car requests 800hp worth of fuel when 700+ hp worth of air is going across the MAF.... on the stock tune.
I did so much research on the topic, i found where you even hit the code once higgs, the limp mode at 150... it was cold in texas that night, i looked up the date in the weather history records. Way way back when you still had a stock tuned vehicle.
And he and I are not arguing the same thing... he thinks that as more aggressive pulleys are added, the car does not compensate for the extra air across the MAF it detects by commanding more fuel.
He honestly believes that the car becomes more and more lean with the aggressive pulleys, and the tune is not smart enough to match air-flow with fuel.
Under his theory, if he drove down off his mountain in Colorado, to the coast line, his engine would be so lean it would blow up. But he does not agree with that either. He wants to have his cake and eat it too, and argue to argue.
I think he knows hes wrong, he just likes to bother me whenever he sees me speak on the topic. Notice he was not in here until i said something..
higgs, when the car is cold, that is the only time it runs lean, or when a person is in vacuum.
Otherwise, at WOT, once at temp, the car is ALWAYS running very rich on the stock tune.
COT mode, the car is running EVEN MORE rich. +800hp worth of fuel rich to be exact.... which is when the low side pump falls on its face. High side CAN pump over 800hp worth of fuel, low side cant supply the high side.
Car requests 800hp worth of fuel when 700+ hp worth of air is going across the MAF.... on the stock tune.
I did so much research on the topic, i found where you even hit the code once higgs, the limp mode at 150... it was cold in texas that night, i looked up the date in the weather history records. Way way back when you still had a stock tuned vehicle.
And he and I are not arguing the same thing... he thinks that as more aggressive pulleys are added, the car does not compensate for the extra air across the MAF it detects by commanding more fuel.
He honestly believes that the car becomes more and more lean with the aggressive pulleys, and the tune is not smart enough to match air-flow with fuel.
Under his theory, if he drove down off his mountain in Colorado, to the coast line, his engine would be so lean it would blow up. But he does not agree with that either. He wants to have his cake and eat it too, and argue to argue.
I think he knows hes wrong, he just likes to bother me whenever he sees me speak on the topic. Notice he was not in here until i said something..
no the car isn't running rich all the time on the stock tune, the car runs rich under COT and that's it, otherwise it runs stoich with minimal fuel trims or as commanded by PE at WOT, verifiable simply by disabling COT.
you say the car runs lean when the car is cold.....when the car is cold or when the air outside is cold? how cold does the car have to be? how cold does the air have to be?
why would the car run lean and have a fuel pressure problem since running lean uses less fuel than running rich?
could you post the link or what have you where you saw me hitting a code with a tune stock Z06 so I can see too? my memory ain't what it used to be. I've popped a lot of codes in my tuning and modding experiments. :-) what are you referring to?
where are you getting or what makes you think it is commanding "800 HP of fuel" when "700 HP is going across the MAF" especially when the car makes 650 peak?
don't take it as arguing, I am trying to understand your perspective.
when i said car runs lean when cold, nothing to do with outside temps... everything to do with the car trying to warm itself up.
Its like the opposite of COT ive heard, and the car runs lean to warm itself up and warm up the cats... true or untrue?
Im not sure where the link is to the thread where you threw the code but it was years ago... took me a long time to find it and a lot of reading, i dont think it was in your thread per se, so i may never find it again, but i do know you had it happen once and i checked the dates and it was cold out in TX... i want to say it was a december date on the post, from 2015/16 maybe?
The cold ambient has to do with more o2 being detected across the maf from denser air.
The 700hp of air and 800hp worth of fuel is just a simple observation that we have seen stock z06 (every one) run the low side out of fuel in the cold at 150mph at sea level. Meanwhile, the callaway cars can run 757 hp no problem once their tune is corrected. Thus, we determined roughly 800hp was the magic number where the low side pump gives up... give or take a few HP.
Since we assume the lt4 blower with stock pulleys and stock cats, is not going to flow much more than 700hp worth of air (just because its cold outside)... we say 700hp worth of air, and 800hp worth of fuel.. and that is the rough guess for when the stock car goes into limp mode from p228c (we keep air flow to HP, below callaway's 757 number with the 2300 blower, it would not make sense for a stock lt4 with stock pulley to flow more than callaway's 2300).
So we know through simple logic that the lt4 stock tune drinks more fuel than 757 tune, and does so on less air passed through the maf... thus we say... the stock car runs very rich
You are correct about COT i guess... but now lets take it one step further....
Cars are in COT mode after 1 WOT pull from our observations, so that's that. Cars are always rich essentially, especially when being driven hard.
Big shops like weapon X have reported hitting COT on the first dyno pull on a cooled down car (this was in their refrigeration, boost coolant chiller thread, if i remember right)
So i do believe that COT comes on very easily., and essentially remains on almost all the time when driving even spiritedly with occasional WOT's
From what I understand, there are 2 levels (or 3) of COT... you would be able to provide the screen shot faster than I would, but there are several temp values for COT in a table in HP tuners... and there is an upper value that is harder to hit.
I tend to loosely refer to that very rich, higher level 2 value as "COT", since our stock tune cars are pretty much always in COT level 1... running somewhat rich.
Its COT level 2 where things become very rich. See if you can take a screen shot of the COT temp values and lets talk about that, because i'm repeating things i've learned along the way and would like to get your feedback on the subject.
Moral of the story though, as fast as I drive, car is either RICH, or VERY RICH, on the stock tune.
And that of course runs it out of fuel, while in COT level 1, and potentially level 2... (waiting on your feedback that level 2 is a real thing. (or even level 3, but i think its just 2 levels))
when i said car runs lean when cold, nothing to do with outside temps... everything to do with the car trying to warm itself up.
Its like the opposite of COT ive heard, and the car runs lean to warm itself up and warm up the cats... true or untrue?
Im not sure where the link is to the thread where you threw the code but it was years ago... took me a long time to find it and a lot of reading, i dont think it was in your thread per se, so i may never find it again, but i do know you had it happen once and i checked the dates and it was cold out.
The cold ambient has to do with more o2 being detected across the maf from denser air.
The 700hp of air and 800hp worth of fuel is just a simple observation that we have seen stock z06 (every one) run the low side out of fuel in the cold at 150mph at sea level. Meanwhile, the callaway cars can run 757 hp no problem once their tune is corrected. Thus, we determined roughly 800hp was the magic number where the low side pump gives up... give or take a few HP.
Since we assume the lt4 blower with stock pulleys and stock cats, is not going to flow much more than 700hp with of air (just because its cold outside)... we say 700hp worth of air, and 800hp worth of fuel.. and that is the rough guess for when the stock car goes into limp mode from p228c.
You are correct about COT i guess... but now lets take it one step further. Cars are in COT mode after 1 long WOT pull, so thats that.
Big shops like weapon X have reported hitting COT on the first pull (this was in their refrigeration, boost coolant chiller thread, if i remember right)
So i do believe that COT comes on very easily.
From what I understand, there are 2 levels of COT... you would be able to provide the screen shot faster than I would, but there are several temp values for COT... and there is an upper value that is harder to hit.
I tend to refer to that loosely as COT, since our stock tune cars are pretty much always in COT level 1... running somewhat rich.
Its COT level 2 where things become very rich. See if you can take a screen shot of the COT temp values and lets talk about that, because im repeating things ive learned along the way and would like to get your feedback on the subject.
Moral of the story though, as fast as I drive, car is either RICH, or VERY RICH, on the stock tune.
And that of course runs it out of fuel, while in COT level 1, and potentially level 2... waiting on your feedback that level 2 is a real thing.
Thank you sir.
when the car is cold it runs very rich until closed loop enables, which is when the O2 sensors warm up enough to switch properly which does not take long at all, maybe a matter of seconds, this is when Short Term fuel trims enable. even so, Long Term fuel trims do not enable until 102 degrees ECT but even that may take only a minute or two, unless you are up north cold starting your car in the dead of winter, in which case I cannot confirm how long it will take. Long Term fuel trims are learned and carry over into full throttle fueling as a safety measure as there are no corrections made during fuel throttle fueling, it is in "open loop" or PE mode, which function the same way (no trim corrections). the car will run a retarded spark value to heat up the cats also on cold start but this also goes away fairly quickly once you move the car, you would not be able to drive the car around with negative timing so this just blows some fuel and heat into the exhaust and then decays out pretty fast. the only way I could see getting a stock Z06 to potentially lose fuel pressure (like actually lose fuel pressure, not the known sensor issue) from running rich due to being cold is to have it in a very cold environment overnight, start it and floor it within a matter of seconds and see what happens. the tune always picks the richest commanded lambda in open loop, whether it be PE, COT, or the open loop warm up tables (based on a calculated intake valve temp). by the way, COT is based on Cat temp, which is also calculated not measured.
honestly it sounds like a lot of guessing on all these HP : airflow figures, I don't think we can have an empirical discussion based on that. it's well known that the stingray craps out around 600 rwhp and the Z06 around 700 rwhp and you can gain or lose a little through modified injection timing, altitude, etc (variables). the stock Z06 runs about 4.9ms injector pulse width at WOT which is as much as I want to see out of any modified car as well before you start to want to use meth or port injection. this can be pushed out to close to 6ms if you want to ride the line a little bit, but I bring my port injection system in right at 5ms and hold the stock fuel system there and let the port make up the rest. amazingly, 5ms happens right at 65 lb/min on the maf, which typically equates to 650 HP.....food for thought I guess.
we agree that pretty much any stock dyno AFR goes into the low to mid 11s, this is COT every time. the stock tune PE value commanded is mid 12s as was mentioned above. the stock tune chooses the richest lambda available (been this way since at least 1997) in open loop, as mentioned. so GM wants to run mid 12s at WOT except for the pesky cats which need to keep cool, and based on the calculated (maybe better to call them inferred) cat temps, this richer lambda (COT) is called into action all the time.
now let's say you have some mods or you have some conditions that warrant positive fuel trims and the last positive fuel trim before you floor it is say, +8%. then you are going to add another 8% of fuel to whatever it already is going to give you, that could take you from 11.4 to 10.7 AFR (yikes).
regarding me hitting some code, I guess we will just have to agree it didn't happen, what do they say, "Pics or it didn't happen?" :-) I am not knowingly denying anything just so you know, I truly don't know what you're referring to and if we can find it, I am happy to discuss it.
the only point I will argue with is that the stock cars CAN run out of fuel pressure in the cold at sea level. There is a forum member who lives near you who did it on his car several times once i explained it to him how it works.
EVERY car others and myself have tested, we can make it happen like clockwork, and the car is above 190 degree oil and coolant temp when it happens. p228c and p0089 are a piece of cake to hit on any car if the person is willing to rally to 150mph in the cold.
the problem with this forum is I cant search your individual posts back past 2018 since it only does a max of 20 pages of posts, and you and I write so damn much.
If i ever find it again, ill let you know. I even took a screen shot of it at the time, but i take screen shots of everything, so who knows... ill have to dig. You did not write p228c in the post however, you just mentioned that your car went into limp mode at high speed (or maybe only threw an engine light, but i think you went into limp mode) and then you went to the chevy store and you indicated "thought" you got it fixed Or maybe you used a tuning computer or something, i forget.
everyone "thinks" they get it fixed Placebo from the chevy store. Might have been in 2017... but i am 99% it was in december.
the only point I will argue with is that the stock cars CAN run out of fuel pressure in the cold at sea level. There is a forum member who lives near you who did it on his car several times once i explained it to him how it works.
EVERY car others and myself have tested, we can make it happen like clockwork, and the car is above 190 degree oil and coolant temp when it happens. p228c and p0089 are a piece of cake to hit on any car if the person is willing to rally to 150mph in the cold.
hitting a code related to fuel pressure doesn't necessarily mean it's out of fuel pressure, it means the programmed computer parameters and hardware think it could be. I have seen discussion of this phenomena however I haven't seen anyone measure the actual fuel pressure, only rely on the potentially incorrect parameters in the code to interpret it that way.....isn't there a TSB to replace the rail sensor or something like that? not saying it doesn't happen, obviously it does, but I would like to see actual rail pressure when the code is set and actual lift pump pressure when the code is set. maybe someone reading this has a log of it happening. it could just be a software reprogramming needed to loosen up some criteria because I agree the ACTUAL fuel pressure shouldn't drop on a stock vehicle.
seems like there are a lot of guys running hard on the race tracks across the country that would get constantly shut down if they were all losing fuel pressure.... what are the specific criteria needed to induce this behavior? surely not just "floor it and wait?"
the problem with this forum is I cant search your individual posts back past 2018 since it only does a max of 20 pages of posts, and you and I write so damn much.
If i ever find it again, ill let you know. I even took a screen shot of it at the time, but i take screen shots of everything, so who knows... ill have to dig. You did not write p228c in the post however, you just mentioned that your car went into limp mode at high speed (or maybe only threw an engine light, but i think you went into limp mode) and then you went to the chevy store and you indicated "thought" you got it fixed
everyone "thinks" they get it fixed Placebo from the chevy store. Might have been in 2017... but i am 99% it was in december.
ok keep me posted. the only time I remember getting a limp code was when I was spraying meth once but I am willing to have my memory refreshed. :-)
yeah, but in our opinions, the low side fuel pressure sensor is the placebo fix from GM.
The reason they did that as a recall/TSB is because they did not want dealerships swapping out pumps...
we have ALL (over 5 of us) had our low side sensors replaced, and then still hit the code again next cold night.
So, for most people, this sensor being replaced "fixes everything"... because the person never coincidentally goes that fast in the cold again.
(chevy chose the least expensive component of the low side fuel system to swap, since they knew there was nothing wrong with the system at all, but wanted customers and dealers to think it had been fixed).... instead of GM admitting "yeah, all the cars have the problem, happens when its cold out.... cant fix it or at least, we dont want to. Requires a whole new tune, not gonna happen, have a great day, dont sue us please"
so the fuel pressure sensor is the lesser of all evils for them to say is the problem, and it tricked a lot of people. Research when their first failure was... always a cold day/night, or the person has extra air flowing mods to their car... one or the other like clockwork..
dbxtune has the fuel pressue logs on a dyno when its cold, and lives near you. Hit him up. nice guy. Has done the problem 3 or 4 times... will probably lemon his car next year
how many levels of richness are there on COT, 2 or 3? I see the temp threshold boxes up there... 3 of them obviously, I just did not know if the first one was normal OT or if it was level 1 COT activation.
04-13-2019, 03:33 AM
Problem with tune stock Z06 with IW18%
Or maybe you used a tuning computer or something, i forget. 
Placebo from the chevy store. Might have been in 2017... but i am 99% it was in december.