132 % duty cycle-is this possible?
05-06-2007, 09:53 PM
#1
8 Second Club
Thread Starter
iTrader: (18)
Join Date: Oct 2002
Location: Waterloo, Ontario
Posts: 2,609
Likes: 0
Received 0 Likes
on
0 Posts
132 % duty cycle-is this possible? some background, 347, F1R 20psi, pump gas with meth, boost refrenced regulator, Bosch 420 intank, BAP. Car's fuel pressure goes up to 75psi then drops down to 40 psi in a slpit second-is the pump just giving up? S what's the next plan of attack.
Heres a screen shot of the log:
Heres a screen shot of the log:
05-07-2007, 01:25 AM
#2
multiple problems:
1. looks like you're doing MAF with 20psi of boost. that's why your MAF is pegged at 58lb/min while it's really more like 120+lb/min of airflow. not good, need a 3barSD setup.
2. if your fuel pressure drops that much then boost is definitely working against it. so i'd say the manifold referenced fuel pressure regulator isn't exactly working. for this much boost you might need more than a single intank pump.
3. duty cycle is calculated from pulse width. pulse width is calculated from airmass and commanded AFR. it is a calculation, not a measurement. thus 130% is possible, because numbers work out this way, not because injectors actually spray more than they're rated for.
1. looks like you're doing MAF with 20psi of boost. that's why your MAF is pegged at 58lb/min while it's really more like 120+lb/min of airflow. not good, need a 3barSD setup.
2. if your fuel pressure drops that much then boost is definitely working against it. so i'd say the manifold referenced fuel pressure regulator isn't exactly working. for this much boost you might need more than a single intank pump.
3. duty cycle is calculated from pulse width. pulse width is calculated from airmass and commanded AFR. it is a calculation, not a measurement. thus 130% is possible, because numbers work out this way, not because injectors actually spray more than they're rated for.
05-07-2007, 07:06 AM
#4
8 Second Club
Thread Starter
iTrader: (18)
Join Date: Oct 2002
Location: Waterloo, Ontario
Posts: 2,609
Likes: 0
Received 0 Likes
on
0 Posts
Yes still on the stock rails-but I do have a return line-using the 97-98 C5 lines. Bro I realize that the 3 bar setup is probably the way to go-i will convert over to that once all the bugs are sorted out-especially fuel. Lonnie is working on a dual intank setup for me.
05-07-2007, 07:19 AM
#5
05-07-2007, 08:49 AM
#6
Originally Posted by RedHardSupra
multiple problems:
1. looks like you're doing MAF with 20psi of boost. that's why your MAF is pegged at 58lb/min while it's really more like 120+lb/min of airflow. not good, need a 3barSD setup.
2. if your fuel pressure drops that much then boost is definitely working against it. so i'd say the manifold referenced fuel pressure regulator isn't exactly working. for this much boost you might need more than a single intank pump.
3. duty cycle is calculated from pulse width. pulse width is calculated from airmass and commanded AFR. it is a calculation, not a measurement. thus 130% is possible, because numbers work out this way, not because injectors actually spray more than they're rated for.
1. looks like you're doing MAF with 20psi of boost. that's why your MAF is pegged at 58lb/min while it's really more like 120+lb/min of airflow. not good, need a 3barSD setup.
2. if your fuel pressure drops that much then boost is definitely working against it. so i'd say the manifold referenced fuel pressure regulator isn't exactly working. for this much boost you might need more than a single intank pump.
3. duty cycle is calculated from pulse width. pulse width is calculated from airmass and commanded AFR. it is a calculation, not a measurement. thus 130% is possible, because numbers work out this way, not because injectors actually spray more than they're rated for.
I agree with number 2, that fall in pressure is slamming the injectors in response.
05-07-2007, 09:32 AM
#7
Frost, while I agree that SC isn't AS variable in airmass delivery as a turbo, it still doesn't mean it's so predictable that you don't have to measure it at all (which is what you're effectively doing if you got a pegged sensor). best example i got for you, is a guy with a SC in kentucky, lives on a hill, works down the hill, and couldnt nail his AFR%Error. turns out he was getting 5psi on higher alitude, and 9psi on lower altitude, so his airmass reading were all over the place, and because he was stubborn and refused to do a 2bar, he couldnt account for just how much air there really is, so if he set his PE to value X to match airflow Y and then drove down the hill, and then the new airflow was more like 1.3*Y, his AFR was 30% off.
would you call 30% off a 'completely tunable' solution? are you willing to be 30% off at wot, only on behalf of being stubborn? if the sensors are not giving you real numbers, why look at them at all?
another point that should fall out of my earlier post but it's not too obvious...
you can measure 58lb/min at max. with that amount of boost you probably have TWICE that. IPW is calculated off the 58lb/min figure, thus what you should be seeing is not 27ms IPW but more like 55ms, which would be around 275% at 6000rpm. OUCH!
so the big point here is that without proper airflow measurement you'll never get to the truth on fueling, aka how big of an injector do you really need. and without 2/3 bar OS and MAP sensor you'll never get that airflow.
would you call 30% off a 'completely tunable' solution? are you willing to be 30% off at wot, only on behalf of being stubborn? if the sensors are not giving you real numbers, why look at them at all?
another point that should fall out of my earlier post but it's not too obvious...
you can measure 58lb/min at max. with that amount of boost you probably have TWICE that. IPW is calculated off the 58lb/min figure, thus what you should be seeing is not 27ms IPW but more like 55ms, which would be around 275% at 6000rpm. OUCH!
so the big point here is that without proper airflow measurement you'll never get to the truth on fueling, aka how big of an injector do you really need. and without 2/3 bar OS and MAP sensor you'll never get that airflow.
Trending Topics
05-07-2007, 10:21 AM
#8
There are literally truckloads of SC'd cars around here that run consistent off of PE and have for years. I guess if you drive up and down mountains it makes a difference. Rather than sweating the change in AFR, a tiny tweak of the meth **** in either direction keeps the AFR in check. Not everyone is eaten up with the desire to have everything in the PCM match commanded or be numbers-on if it is working; most are more concerned by how it drives when they are driving it.
05-07-2007, 11:08 AM
#9
yes, popularity makes things right. for example 'top 40' chart is populated exclusively in the greatest the music has to offer 
seriously though, 'how it drives' is not exactly the best method to assess the quality of the setup. this guy's case is a great example. he needs injectors 3 times bigger than what he's got and he doesn't even know it! feels ok though. if the computer doesn't need any of these 'numbers' correct, then why bother tuning at all?
the whole 'it's how everyone been doing it' approach sucks major *****, because it establishes **** poor tune quality as the standard. people blow **** up, and 'tuners' and shops get away with shitty quality work blaming it on people and getting away with it 'it's a race car, no liability here' mentality.
all i know is that every now and then when i actually manage to convince people of getting their 'numbers' realistic they've managed to gain 100hp sometimes, simply on not bullshitting the computer. but i guess that's just a number too, so it's not important.
seriously though, 'how it drives' is not exactly the best method to assess the quality of the setup. this guy's case is a great example. he needs injectors 3 times bigger than what he's got and he doesn't even know it! feels ok though. if the computer doesn't need any of these 'numbers' correct, then why bother tuning at all?
the whole 'it's how everyone been doing it' approach sucks major *****, because it establishes **** poor tune quality as the standard. people blow **** up, and 'tuners' and shops get away with shitty quality work blaming it on people and getting away with it 'it's a race car, no liability here' mentality.
all i know is that every now and then when i actually manage to convince people of getting their 'numbers' realistic they've managed to gain 100hp sometimes, simply on not bullshitting the computer. but i guess that's just a number too, so it's not important.
05-07-2007, 12:29 PM
#10
His injector jump coincides with pressure loss and he needs injectors that are 3 times bigger?
There are literally thousands of SC'd cars riding around on PE tunes that are solid, have been running for years, and and WILL NOT GAIN 100HP or even 50 by moving to a 2-bar tune with an accurate VE. I'm not going to sit here and argue over it, your idea of the right way doesn't make it the ONLY right way. FWIW I prefer the 2-bar setup too, but that doesn't make other alternatives "wrong".
There are literally thousands of SC'd cars riding around on PE tunes that are solid, have been running for years, and and WILL NOT GAIN 100HP or even 50 by moving to a 2-bar tune with an accurate VE. I'm not going to sit here and argue over it, your idea of the right way doesn't make it the ONLY right way. FWIW I prefer the 2-bar setup too, but that doesn't make other alternatives "wrong".
05-07-2007, 03:25 PM
#11
8 Second Club
Thread Starter
iTrader: (18)
Join Date: Oct 2002
Location: Waterloo, Ontario
Posts: 2,609
Likes: 0
Received 0 Likes
on
0 Posts
Guys I appreciate your input. FWIW, the car starts, drives and runs very good-it's just out of injector. I agree this probably is not the "right" way to do it but I cannot argue with the #'s or how it's performed at the track(last year i ran 10.4@137 on the stock short-640rwhp). I just don't want to go through the whole learning curve until all the other bugs are sorted out.
05-07-2007, 10:17 PM
#13
845rwhp though that drivetrain equals roughly 1100hp pushing on the crank.The 420 can't hold and I doubt dual intanks will.A4's use alot more fuel.
Car should have 96lb injectors with a 3 bar SD setup.The bigger injectors will probly help the pump since fuel pressure will be lower and the SD will steady the tune out.
Car should have 96lb injectors with a 3 bar SD setup.The bigger injectors will probly help the pump since fuel pressure will be lower and the SD will steady the tune out.
05-07-2007, 11:12 PM
#14
8 Second Club
Thread Starter
iTrader: (18)
Join Date: Oct 2002
Location: Waterloo, Ontario
Posts: 2,609
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Frost
If it were just injectors why would your pump drop 45% line pressure?
Your right Frost-it is the pump that is taking a dump. Lonnie from LPA says he has customers making 900 rwhp-with dual walbro's and 60's. He's making me a dual Walbro setup right now. I will be doing that and swaping over to RC 72's. I'll run the 72's at 45psi and boost reference them-so at 55 psi they'll be acting like 85's where as the 60's would need to up to 75psi to act the same. This should help with the pumps. The way Lonnie sets up the duals is the second pump only comes on with boost-couple that with the boost a pump and I'm pretty sure it would work. And if it doesn't work-then i guess I'll just have to get a driver box.
Slowhawk-what are you guys running for pumps at this hp level.
1 more thing-i will be turning the power down-i don't need 885 rwhp-850 or even 800 will be plenty. Hell I ran 10.45@136.5 at 640 rwhp with a stick, all i want is mid 9's-with the auto i think 750 rwhp should be plenty.
05-08-2007, 07:04 AM
#15
My setup is similar.... I have a racetronix pump and harness, boost a pump, and a second pump in the bucket that is triggered by a hobbs switch at about 3psi. You can't even tell when it comes on; it's seemless. I run an alkycontrol meth kit too and 60#ers. I run 16psi on pump and meth with a FMFPR and the base pressure at 55#s. I have had it up to about 18.5psi on the street with good gas and haven't had any troubles keeping up so far, and my setup isn't even ideal like yours from Lonnie's will be. I have some restrictive points and even a few feet of STOCK LINE. I know.... I have what I needed to get rid of it, but it hasn't had a problem yet so....
https://ls1tech.com/forums/fueling-injection/615108-my-twin-walbro-s-01-t-pics-schizz.html
https://ls1tech.com/forums/fueling-injection/615108-my-twin-walbro-s-01-t-pics-schizz.html
05-08-2007, 07:27 AM
#16
Don't waste time or $$ on 72's. You need 96's from looking at your setup.
We run dual Walbro 420's up to 1000rwhp on auto's.I doubt a dual intank on a vette will support your power level through an A4. Under real street load the pressure will drop again.
We run dual Walbro 420's up to 1000rwhp on auto's.I doubt a dual intank on a vette will support your power level through an A4. Under real street load the pressure will drop again.