750cc injector help needed
Thread Starter
Teching In
Joined: Oct 2012
Posts: 17
Likes: 0
750cc injector help needed Just swapped in some RC Engineering 750cc (71/72lb) injectors in my LS6. I can't get them tuned to save my life. Contacting RC was pretty much a waste of time. I calculated an offset table based on the few numbers they gave me. Also figured out the flow rate. I need help with short pulse limit, short pulse adder, and min injector rate. Using HP tuners. Anyone able/willing to help a fellow hobbyist out?
when you say you can't get them tuned, what are you having problems with while the car is running?
Did RC not offer any support at all?
cut the stock tables by 30% and see where you get.
Did RC not offer any support at all?
cut the stock tables by 30% and see where you get.
Thread Starter
Teching In
Joined: Oct 2012
Posts: 17
Likes: 0
The only help RC gave me was a a few offset values at a few voltages. I had to use a datafit to calculate the curve of the rest and then create the offset table from that.
Issues I'm having are they are very lean (17:1) when you start the engine. After 30 sec to a min and a half it richens up (same time command afr tries to lean it up from 13.7 to 14.7) Once it richens up like that then if you restart then engine any time withing 15 min or so its fine and idles rich (13.2:1). If the engine sits off for any longer than that when you restart it it goes lean again. To even get it to run this good I had to cut short pulse adder by about 80%. Anything more and its always crazy rich. I currently have min pulse rate at .8ms or so. During idle the injectors are usually around 1.8ms.
Issues I'm having are they are very lean (17:1) when you start the engine. After 30 sec to a min and a half it richens up (same time command afr tries to lean it up from 13.7 to 14.7) Once it richens up like that then if you restart then engine any time withing 15 min or so its fine and idles rich (13.2:1). If the engine sits off for any longer than that when you restart it it goes lean again. To even get it to run this good I had to cut short pulse adder by about 80%. Anything more and its always crazy rich. I currently have min pulse rate at .8ms or so. During idle the injectors are usually around 1.8ms.
what is your Open loop fueling table look like? can you post your tune?
can you post a few data logs or at least one? post the data you are dealing with. I will try to help best I can.
can you post a few data logs or at least one? post the data you are dealing with. I will try to help best I can.
Thread Starter
Teching In
Joined: Oct 2012
Posts: 17
Likes: 0
Open loop eq ratio is set to 1.0 in the temp areas I would see. I should also mention that COT is disabled as is the air pump (also completely unhooked from headers) so those are not throwing off the initial lean situation. You feel it wanting to die when its that lean. Heres the current tune. No available log right now. I know VE is pretty choppy as well but it does the lean issue when it idles (800rpm)
your ifr table at the beginning is a little funny.
based off the 750cc injectors, you have 71.36# injectors
convert that to 58psi (is this the actual fuel pressure you are running?)
and you get 1.1547 * 71.36 = 82.4# base, then apply bernoulli and you will get the table I have attached. I also messed with your open loop EQ ratio. Are you boosted or not now? I see you have the 2 bar map applied.
I smoothed your VE table also. The car will go from open loop to closed loop depending on how long it is off...try to see in the scanner and watch your AFR when it switches. there is a status bit/ indicator for open/closed loop watch it while watching your AFR.
based off the 750cc injectors, you have 71.36# injectors
convert that to 58psi (is this the actual fuel pressure you are running?)
and you get 1.1547 * 71.36 = 82.4# base, then apply bernoulli and you will get the table I have attached. I also messed with your open loop EQ ratio. Are you boosted or not now? I see you have the 2 bar map applied.
I smoothed your VE table also. The car will go from open loop to closed loop depending on how long it is off...try to see in the scanner and watch your AFR when it switches. there is a status bit/ indicator for open/closed loop watch it while watching your AFR.
Thread Starter
Teching In
Joined: Oct 2012
Posts: 17
Likes: 0
I can't open the zip file for some reason. I thought I had closed loop disabled so it would stay in open loop. Did I miss something and that's not the case? I only planned on keeping it in open loop until I get it tuned decently for now (getting VE tuned for now with these injectors as well as the injector change ironed out) then going back to closed loop. Yes, fuel pressure is 58. Its not currently boosted. I'll be adding some twins this winter, so thats the reason for 2 bar SD tune and larger injectors. I want to get it running decently now before I fab everything up for the turbos and retune. So was the possible issue that to was still in closed loop? I know fuel trims are currently disabled, so that would make sense why those never changed if it was in CL. Like I said, I can't open the zip file for some reason. Any chance you still have your changes in hpt format?
Trending Topics
Thread Starter
Teching In
Joined: Oct 2012
Posts: 17
Likes: 0
Alright, so I was able to open your changes and apply them. I did not change anything other than what you had changed. Here are 2 logs. The first is from a complete cold start after uploading the changes. You'll see when the wideband is up to temp and starts reading. Right about 4:42 you'll notice is starts getting rich. At this same time, I noticed the fan shut off. Usually when it changes into rich at idle after start, I notice the fan shuts off then as well. In past tunes I have tried setting the cooling fan airflow to 0 lb/min for both but that never changed anything except a very slight drop in voltage. Right at 6 min in I gave it some throttle to see how it reacts.
The second log was once it was warmed up. It was pretty much exactly 1 min after the first one ended, so the engine was only off for 1 min. Again I gave it some light throttle in a little to see any changes. My wideband is located about 48-58" from the heads, so there's some slight slight delay to account for.
Your chances did seem to help quite a bit as far as how lean it is at initial idle, but as you can see, it still goes to rich later. Ideas???
EDIT: Something else I just noticed... When it switches from lean to rich it does so when TPS drops from 9 to 8. Then gets even richer as TPS drops down to 7. Injector pulse width and RPM remain the same as this all happens. I know when driving it if you are below a certain TPS (I thought 12% or so) with this tune and injectors it would go rich just like at idle. Where would cut down on fuel based on TPS? I don't see anything specific to TPS in fueling or idle.
The second log was once it was warmed up. It was pretty much exactly 1 min after the first one ended, so the engine was only off for 1 min. Again I gave it some light throttle in a little to see any changes. My wideband is located about 48-58" from the heads, so there's some slight slight delay to account for.
Your chances did seem to help quite a bit as far as how lean it is at initial idle, but as you can see, it still goes to rich later. Ideas???
EDIT: Something else I just noticed... When it switches from lean to rich it does so when TPS drops from 9 to 8. Then gets even richer as TPS drops down to 7. Injector pulse width and RPM remain the same as this all happens. I know when driving it if you are below a certain TPS (I thought 12% or so) with this tune and injectors it would go rich just like at idle. Where would cut down on fuel based on TPS? I don't see anything specific to TPS in fueling or idle.
Last edited by yttz; Oct 29, 2012 at 12:47 PM.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo Thread Starter
Teching In
Joined: Oct 2012
Posts: 17
Likes: 0
See above post.
Here's a log of starting it 30 min after the last one. Again, same thing seen where its lean. As TPS drops, it gets richer even though it maintains the same RPM and injector pulse width. I'm lost here as to what table would deal with this issue. How to drop the pulse width/fueling based on tps. Or if there's a way to keep the TPS up without raising the RPM. Stuck...
Here's a log of starting it 30 min after the last one. Again, same thing seen where its lean. As TPS drops, it gets richer even though it maintains the same RPM and injector pulse width. I'm lost here as to what table would deal with this issue. How to drop the pulse width/fueling based on tps. Or if there's a way to keep the TPS up without raising the RPM. Stuck...
Last edited by yttz; Oct 29, 2012 at 02:34 PM.
