Is HPtuners capable of checking fuel rail psi
10-07-2011, 10:51 AM
#21
With a crate LS6 and full bolt-ons, you are probably just at the upper limit of the capabilities of the stock injectors.
When another friend comes along that has a wideband, just make sure you don't run off with his girl too. Friends with widebands come in handy, and the sensors usually last longer than most relationships. Just sayin.
When another friend comes along that has a wideband, just make sure you don't run off with his girl too. Friends with widebands come in handy, and the sensors usually last longer than most relationships. Just sayin.
10-08-2011, 10:11 AM
#22
On The Tree
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lol ya I hear ya thanks for all the advice the injectors probably do need to be swapped and the reason the DC is high is because he probably added some fuel up top so it didnt run lean accidently. Just for peace of mind I did get a racetronix pump with the hotwire kit. Turns out a friend bought one for his trans am and never used it so he gave it to me for a deal I just couldnt pass up the peace of mind will be worth it lol.
10-08-2011, 03:39 PM
#23
I use a pressure guage with a hose long enough to rest under the windshield wipers
works great. A tired pump can be in specs for all but WOT, pressure dropping off to say 50psi WOT is a problem the racetronix kit does a good job of fixing SOTP differnce.
works great. A tired pump can be in specs for all but WOT, pressure dropping off to say 50psi WOT is a problem the racetronix kit does a good job of fixing SOTP differnce.
10-08-2011, 10:11 PM
#24
The IFR table is set by the injectors chosen, but is based on the assumption that the fuel pressure is somewhere around 58 psi. If the pressure drops significantly under load, the injector flow rate will go down, but most people don't take the time to figure that out and incorporate it into the IFR table.
It has already been made clear that the PCM doesn't know what the fuel pressure is, but the PCM does control the AFR. If the fuel pressure is dropping but that fact is not documented in the IFR table, you can easily compensate for that by jacking up the values in the MAF table (or VE table if you are running SD). Or you can start playing games with any of the other tables in the PCM that control fueling (the PE table was popular in the not-too-distant past).
So say you install a new fuel pump, be that a higher volume pump or a stock replacement, and that happens to fix the fuel pressure dropping at WOT (or at least keeps it from dropping as much as it was). If you don't touch the tune, you WILL be running richer under the conditions where the pressure was dropping before. Why? Because the PCM doesn't know the fuel pressure was altered...all it knows is what injector pulse width to demand based on the conditions (RPM, MAP, TPS, etc.), and that is something either the factory, you, or another tuner told it to do.
If you didn't know the pressure was dropping before, but you saw your AFR going lean, you'd add fuel to the tune. That can only be done in the PCM by asking the injectors to stay open longer, because you certainly can't ask it to increase the fuel pressure. That would drive your injector duty cycle up, and if it goes too far, it will only leave you two choices - increase the fuel pressure, or replace the injectors with ones that can flow more fuel.
If you were on the factory tune and stated having problems with the fuel pump where it was dropping pressure, you'd end up running lean. If you (or someone else) used software to alter the tune in the PCM to bring the AFR back in line, you could compensate for this by asking the injectors to stay open longer, but you can only do that to a point, and that point is where the injectors go static and physically can't flow any more fuel (IDC = 100%).
Fuel pressure does play into this equation, but it is only one of the variables involved. Unfortunately, it is the one variable that the PCM doesn't know on its own, so you either have to tell it or suffer the consequences.
10-09-2011, 09:06 AM
#25
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It does, but it is indirect - the volume of fuel your engine requires to maintain the proper AFR is fixed by whatever combo you are running (it is only an air pump after all). That leaves a couple variables that matter - the stock lines start to become a restriction north of 700 RWHP or so, so that doesn't matter in this case. That leaves the injector flow rate and the fuel pressure at the injectors. The lower the pressure, the lower the injector flow rate.
The IFR table is set by the injectors chosen, but is based on the assumption that the fuel pressure is somewhere around 58 psi. If the pressure drops significantly under load, the injector flow rate will go down, but most people don't take the time to figure that out and incorporate it into the IFR table.
It has already been made clear that the PCM doesn't know what the fuel pressure is, but the PCM does control the AFR. If the fuel pressure is dropping but that fact is not documented in the IFR table, you can easily compensate for that by jacking up the values in the MAF table (or VE table if you are running SD). Or you can start playing games with any of the other tables in the PCM that control fueling (the PE table was popular in the not-too-distant past).
So say you install a new fuel pump, be that a higher volume pump or a stock replacement, and that happens to fix the fuel pressure dropping at WOT (or at least keeps it from dropping as much as it was). If you don't touch the tune, you WILL be running richer under the conditions where the pressure was dropping before. Why? Because the PCM doesn't know the fuel pressure was altered...all it knows is what injector pulse width to demand based on the conditions (RPM, MAP, TPS, etc.), and that is something either the factory, you, or another tuner told it to do.
If you didn't know the pressure was dropping before, but you saw your AFR going lean, you'd add fuel to the tune. That can only be done in the PCM by asking the injectors to stay open longer, because you certainly can't ask it to increase the fuel pressure. That would drive your injector duty cycle up, and if it goes too far, it will only leave you two choices - increase the fuel pressure, or replace the injectors with ones that can flow more fuel.
If you were on the factory tune and stated having problems with the fuel pump where it was dropping pressure, you'd end up running lean. If you (or someone else) used software to alter the tune in the PCM to bring the AFR back in line, you could compensate for this by asking the injectors to stay open longer, but you can only do that to a point, and that point is where the injectors go static and physically can't flow any more fuel (IDC = 100%).
Fuel pressure does play into this equation, but it is only one of the variables involved. Unfortunately, it is the one variable that the PCM doesn't know on its own, so you either have to tell it or suffer the consequences.
The IFR table is set by the injectors chosen, but is based on the assumption that the fuel pressure is somewhere around 58 psi. If the pressure drops significantly under load, the injector flow rate will go down, but most people don't take the time to figure that out and incorporate it into the IFR table.
It has already been made clear that the PCM doesn't know what the fuel pressure is, but the PCM does control the AFR. If the fuel pressure is dropping but that fact is not documented in the IFR table, you can easily compensate for that by jacking up the values in the MAF table (or VE table if you are running SD). Or you can start playing games with any of the other tables in the PCM that control fueling (the PE table was popular in the not-too-distant past).
So say you install a new fuel pump, be that a higher volume pump or a stock replacement, and that happens to fix the fuel pressure dropping at WOT (or at least keeps it from dropping as much as it was). If you don't touch the tune, you WILL be running richer under the conditions where the pressure was dropping before. Why? Because the PCM doesn't know the fuel pressure was altered...all it knows is what injector pulse width to demand based on the conditions (RPM, MAP, TPS, etc.), and that is something either the factory, you, or another tuner told it to do.
If you didn't know the pressure was dropping before, but you saw your AFR going lean, you'd add fuel to the tune. That can only be done in the PCM by asking the injectors to stay open longer, because you certainly can't ask it to increase the fuel pressure. That would drive your injector duty cycle up, and if it goes too far, it will only leave you two choices - increase the fuel pressure, or replace the injectors with ones that can flow more fuel.
If you were on the factory tune and stated having problems with the fuel pump where it was dropping pressure, you'd end up running lean. If you (or someone else) used software to alter the tune in the PCM to bring the AFR back in line, you could compensate for this by asking the injectors to stay open longer, but you can only do that to a point, and that point is where the injectors go static and physically can't flow any more fuel (IDC = 100%).
Fuel pressure does play into this equation, but it is only one of the variables involved. Unfortunately, it is the one variable that the PCM doesn't know on its own, so you either have to tell it or suffer the consequences.
Now what I've learned from in here is that the fuel pressure will not have any effect on the IDC that hptuners shows because the pcm only determines that number off the tune...
Now it can still be running lean because of a bad pump up top however it will not show by looking at IDC in hptuners it will only show with a wideband or psi gauge. However IF it is going lean and I'm not even sure it is because it runs good it should be corrected with the racetronix pump because originally the car was tuned assuming 58psi and good afr.
With that all said haha I was wondering if anyone had some insight on how to run the hotwire kit up over the tank while using the trap door method to put in the pump. Has anyone even installed the hotwire kit with the tank in the car?
10-09-2011, 02:18 PM
#26
I dropped the tank to do mine...it would have been a bitch otherwise. If you don't end up dropping the tank, do yourself a favor and at least loosen the bolts that hold the straps in place. There's quite a bit of wiggle room with those bolts - you can loosen them at least 3/4"-1" without actually removing the bolts.
