mysterious fueling problem
Thread Starter
TECH Apprentice
Joined: Nov 2016
Posts: 371
Likes: 18
From: switzerland
mysterious fueling problem this is an otherwise stock 99 c5 running up to 15 psi on a novi 1500. it was leaning out on top at 100% duty because of falling fp (67 psi idle, 48 psi@6200), so i didnt push it. i also didnt logg for almost a year.
now i have rewired the pump with a modified racetronix harness and an additional ground to the battery. guess what. my fp is exactly the same. this is weird, as every pump i have seen so far has a drop on stock wires. i wanted to mesure the voltage before and after, but was too lazy to do it. now i regrett it.
whats even more weird is that im running richer now by roughly 3%. at 3000, 5000. 6000 rpm. same everywhere. ipw is the same as before, i even uploaded the tune from the car to be sure i was looking at the same loggs. so with the same ipw and pressure, how can it be richer. what am i missing? the pump seems to be louder at idle also.
has the wideband drifted while sitting? i also added some torco. would that make it read higher? im tempted to get another afr meter or have the mixture measured on a dyno.
(fp is logged with efilife and a honeywell sensor. iat is very close in before and after loggs.)
any thoughts?
now i have rewired the pump with a modified racetronix harness and an additional ground to the battery. guess what. my fp is exactly the same. this is weird, as every pump i have seen so far has a drop on stock wires. i wanted to mesure the voltage before and after, but was too lazy to do it. now i regrett it.
whats even more weird is that im running richer now by roughly 3%. at 3000, 5000. 6000 rpm. same everywhere. ipw is the same as before, i even uploaded the tune from the car to be sure i was looking at the same loggs. so with the same ipw and pressure, how can it be richer. what am i missing? the pump seems to be louder at idle also.
has the wideband drifted while sitting? i also added some torco. would that make it read higher? im tempted to get another afr meter or have the mixture measured on a dyno.
(fp is logged with efilife and a honeywell sensor. iat is very close in before and after loggs.)
any thoughts?
Last edited by Dian; Dec 5, 2016 at 12:11 PM.
One thing is PW and a different one the actual fuel mass that goes past the injector.
If you had pump problems and tuned that way then fixed the pump problem, the AFR is going to change for sure.
If pressure changes so will the AFR at the same PW
If you had pump problems and tuned that way then fixed the pump problem, the AFR is going to change for sure.
If pressure changes so will the AFR at the same PW
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
I think that all returnless systems loose a little pressure as the engine load goes up; the tuning compensates for that. That is why I and many others run a return system with the regulator on the rail. (Such a change would require re-tuning because now the pressure is constant.)
Your turbo setup is overloading the stock fuel line and causing the huge pressure drop.
Its probably about a 3/8" ID fuel line and you will need to go to 1/2" to reduce the pressure drop and stabilize it.
Can't explain why you are now 3% richer with the same measured fuel pressure. Perhaps there are pulsations in the pressure and with the new pump they are different.
To each their own, but I would run a return system with rail regulations with your turbo system.
Your turbo setup is overloading the stock fuel line and causing the huge pressure drop.
Its probably about a 3/8" ID fuel line and you will need to go to 1/2" to reduce the pressure drop and stabilize it.
Can't explain why you are now 3% richer with the same measured fuel pressure. Perhaps there are pulsations in the pressure and with the new pump they are different.
To each their own, but I would run a return system with rail regulations with your turbo system.
Staging Lane
Joined: Nov 2015
Posts: 96
Likes: 0
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
IIRC, the flow rate of an injector only goes up by the square root of the increase in pressure. So even going from 48 to 67 psi, a 40% increase, the flow rate will only go up by 18%.
Therefore, if you are at 100% DC at 48 psi, it will only go down to 82% DC at 67 psi, which is still more than the suggested max of 80% duty cycle.
In summary - yes you also will need bigger injectors.
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What I prefer is to use injectors more to the big side (without going too big) to avoid the use of high pressure. Using between 43 to 58 psi keeps the pumps happier and last much longer than forcing them to run at 70 psi or more.
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this is an otherwise stock 99 c5 running up to 15 psi on a novi 1500. it was leaning out on top at 100% duty because of falling fp (67 psi idle, 48 psi@6200), so i didnt push it. i also didnt logg for almost a year.
now i have rewired the pump with a modified racetronix harness and an additional ground to the battery. guess what. my fp is exactly the same. this is weird, as every pump i have seen so far has a drop on stock wires. i wanted to mesure the voltage before and after, but was too lazy to do it. now i regrett it.
whats even more weird is that im running richer now by roughly 3%. at 3000, 5000. 6000 rpm. same everywhere. ipw is the same as before, i even uploaded the tune from the car to be sure i was looking at the same loggs. so with the same ipw and pressure, how can it be richer. what am i missing? the pump seems to be louder at idle also.
has the wideband drifted while sitting? i also added some torco. would that make it read higher? im tempted to get another afr meter or have the mixture measured on a dyno.
(fp is logged with efilife and a honeywell sensor. iat is very close in before and after loggs.)
any thoughts?
now i have rewired the pump with a modified racetronix harness and an additional ground to the battery. guess what. my fp is exactly the same. this is weird, as every pump i have seen so far has a drop on stock wires. i wanted to mesure the voltage before and after, but was too lazy to do it. now i regrett it.
whats even more weird is that im running richer now by roughly 3%. at 3000, 5000. 6000 rpm. same everywhere. ipw is the same as before, i even uploaded the tune from the car to be sure i was looking at the same loggs. so with the same ipw and pressure, how can it be richer. what am i missing? the pump seems to be louder at idle also.
has the wideband drifted while sitting? i also added some torco. would that make it read higher? im tempted to get another afr meter or have the mixture measured on a dyno.
(fp is logged with efilife and a honeywell sensor. iat is very close in before and after loggs.)
any thoughts?
Thread Starter
TECH Apprentice
Joined: Nov 2016
Posts: 371
Likes: 18
From: switzerland
we have no ethanol in the gas. im using shell v-power 100 octane (ron).
iv done some "research" and it seems the lingenfelter pump (probably walbro 255 l/h) is too small. well, i used what came with the kit, as well as the 60 lbs/hr deka injectors.
so at 100% duty and 48 psi they will flow 63 lbs. which works out to 79 gal/hr fuel flow. the walbro pumps are rated at 67 gal for 13.5v at that pressure. so thats where my drop comes from. they only draw 8 amps, which would explain why the stock wiring was o.k. (i supposedly have a walbro grj420p, cant find anything like that, only gssxxx pumps.)
if the fuel line is 3/8 id the drop throug 10 feet should be around 1 psi, so thats not the problem (im loosing 20).
http://www.freecalc.com/fricdia.htm
i have run injectors at 100% duty on several engines and they give no problems. however 504 lbs/hr (79 gal/hr)/0.6 bsfc is 840 hp. the stock ls1 rated at 345 hp and with 15 psi boost is probably putting out 650 hp max through the stock exhaust. so i have no idea where all that fuel is actually going. i should be only needing 60 gal/hr. not sure btw if 0.60 bsfc is realistic at 11.4 afr im aiming for though.
still a mystery why im running richer now, idle and pt trims seem not to have changed. probably the sensor after all or the torco i put in there.
edit: the engine should be needing 510 lbs/hr @11.4 afr and 100% ve, just for comparison.
iv done some "research" and it seems the lingenfelter pump (probably walbro 255 l/h) is too small. well, i used what came with the kit, as well as the 60 lbs/hr deka injectors.
so at 100% duty and 48 psi they will flow 63 lbs. which works out to 79 gal/hr fuel flow. the walbro pumps are rated at 67 gal for 13.5v at that pressure. so thats where my drop comes from. they only draw 8 amps, which would explain why the stock wiring was o.k. (i supposedly have a walbro grj420p, cant find anything like that, only gssxxx pumps.)
if the fuel line is 3/8 id the drop throug 10 feet should be around 1 psi, so thats not the problem (im loosing 20).
http://www.freecalc.com/fricdia.htm
i have run injectors at 100% duty on several engines and they give no problems. however 504 lbs/hr (79 gal/hr)/0.6 bsfc is 840 hp. the stock ls1 rated at 345 hp and with 15 psi boost is probably putting out 650 hp max through the stock exhaust. so i have no idea where all that fuel is actually going. i should be only needing 60 gal/hr. not sure btw if 0.60 bsfc is realistic at 11.4 afr im aiming for though.
still a mystery why im running richer now, idle and pt trims seem not to have changed. probably the sensor after all or the torco i put in there.
edit: the engine should be needing 510 lbs/hr @11.4 afr and 100% ve, just for comparison.
Last edited by Dian; Dec 10, 2016 at 02:54 AM.
Staging Lane
Joined: Nov 2015
Posts: 96
Likes: 0
You don't see too many people calculating fueling requirements using bsfc... it's too dependent on spark timing which makes it difficult to accurately estimate.
To run that pump, you'll likely need a BAP and run it at 18v for it to keep up.
A stock LS1 with 15lbs on a Novi is probably still safe with the 60s (with enough fuel pump flow). The 60s are good in theory to about 700rwhp on gas with enough pump. Anything above that, and I'd go to the 80s. ECS has an external AEM 380 pump that comes on with a Hobbs switch to augment the factory/upgraded in-tank pump (they sell as their Stage 1 Fuel System). They claim it's good for 800rwhp. With the 80s, you'd be safe with that kit.
The other option would be Lonnie's Double Pumper kit with twin in tank Walbro pumps with a hobbs switch. Similar price for both. Depends on whether you want to run an external pump or twin in-tank pumps.
But that'd be my suggestion.
A stock LS1 with 15lbs on a Novi is probably still safe with the 60s (with enough fuel pump flow). The 60s are good in theory to about 700rwhp on gas with enough pump. Anything above that, and I'd go to the 80s. ECS has an external AEM 380 pump that comes on with a Hobbs switch to augment the factory/upgraded in-tank pump (they sell as their Stage 1 Fuel System). They claim it's good for 800rwhp. With the 80s, you'd be safe with that kit.
The other option would be Lonnie's Double Pumper kit with twin in tank Walbro pumps with a hobbs switch. Similar price for both. Depends on whether you want to run an external pump or twin in-tank pumps.
But that'd be my suggestion.
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
If you Google "fuel line size for 700 hp" you will see that the consensus is anything over 500HP should have a line bigger than 3/8".
http://www.ffcars.com/forums/17-fact...hp-rating.html
Your theoretical calculator doesn't account for turns, kinks and connections.
http://www.ffcars.com/forums/17-fact...hp-rating.html
Your theoretical calculator doesn't account for turns, kinks and connections.
Thread Starter
TECH Apprentice
Joined: Nov 2016
Posts: 371
Likes: 18
From: switzerland
i will have larger lines for sure, if i upgrade the system. i was just saying the line restriction could not account for the 20 psi i loose. i will go external, because i dont feel like messing with the intank stuff again. do the hobb-switched pumps produce a pressure rise, when they come on? no bap, i like to keep things simple (no meth for the same reason).