L67 Injector IFR help

[SMOKINV8]

I'm assuming 5_liter misspoke up above, but it doesn't have anything to do with the return system directly. You aren't going to have a vacuum referenced FPR on a returnless system because your FPR is in the back of the car by the gas tank.

If your FPR is vacuum referenced then your IFR is flat. If it isn't, its sloped.

[5_Liter_Eater]

You figure the flow rate of the injector using the equation here: http://www.rceng.com/technical.aspx?...ressure_Change It's not just a multiplier. Whatever number you come up with there is what the injector will flow at atmospheric pressure.

As CTX said in post #11, basically under vacuum the fuel is bing sucked out of the injectors, effectively, virtually increasing the fuel pressure so the injector flows more. Under boost the injectors are having to push against the manifold pressure, effectively virtually decreasing the fuel pressure. So, to get the slope of the line you simply add or subtract the MAP to/from the rail fuel pressure. So a 60# injector rated at 3 bar (43.5 PSI) running at 4 bar (58 PSI) would flow ~69.3#/hr (at atmospheric). Say it idles at a MAP of 55 KPa which is ~8 PSI of vacuum then you'd add 8 PSI to the 58 and re-calculate and you get ~73.9#/hr.

Now, if the system is return style and vacuum referenced then yes, the IFR should be be flatlined. Thats because the regulator is lowering the fuel pressure for you at a 1:1 ratio to MAP PSI. So 5 PSI of manifold vacuum would reduce the fuel pressure 5 PSI so the equation would not have to take the 5 PSI of manifold vacuum into account and you'd have the same value as when it's run at atmospheric. The consequences of running a sloped IFR table with a vacuum referenced return style fuel system is incorrect fueling (too much fuel) getting worse and worse as vacuum increases.

Making more sense now?

Sorry but I seem to be a bit thickheaded in trying to figure this out.
So i have Siemens 60# injectors rated at 43.5psi
I have a 99GTP with return style fuel system and vacuum on stock FPR
Based on this I should have a flat graph line in my injector table but I don't. What are the consequences of this?

Also, how is the sloped rate properly calculated.
Stock GTP injector 36lbs divided by new injector 60lbs, so 60/36=1.6667
We multiply our current injector by new upgraded scale factor..
36x 1.6667 = 60.012 lbs new IFR linear chart?

Now, If the above is correct, how do we turn this into a sloped table? We don't use the HPT conversion chart do we. It asks for current and new fuel pressure. Most of us change injectors, not fuel pressure so this conversion chart seem useless you raise fuel pressure correct?

[krunchss]

Clear as mud 5_Liter_Eater :P

I was going to just leave this thread alone as the more I read, the more I got confused. But as eclipse5302 said, both the L67 and L36 have the same fuel system, but one has a flat IFR and the other has a ramped IFR. So, back to my original question...

Should I be running a sloped IFR on a boosted L36 that was originally NA?

eclipse5302, I do plan to consider trying the L67 bin at some point, as there are a few things I could benefit from such as the MAP, and I think the spark tables also have better resolution just to name a few. I guess I don't mind reading my bin and it then say I have a 2002 Grand Prix GTP instead of a Monte Carlo. Before I make the change, I need to decide on the best bin match for my car as there was no 2002 L67 Monte Carlo :P I'll worry bout that later, but few to no people have told me to upgrade to a bin that supports 2 or more bars, so I question if it's really necessary for my car or not.

Krunch

[krunchss]

Oops! Missed this post

So are you saying that even though my L36 that was originally NA should STILL run a flat IFR even though now I am boosted?

Krunch

I'm assuming 5_liter misspoke up above, but it doesn't have anything to do with the return system directly. You aren't going to have a vacuum referenced FPR on a returnless system because your FPR is in the back of the car by the gas tank.

If your FPR is vacuum referenced then your IFR is flat. If it isn't, its sloped.

[eclipse5302]

Clear as mud 5_Liter_Eater :P

I was going to just leave this thread alone as the more I read, the more I got confused. But as eclipse5302 said, both the L67 and L36 have the same fuel system, but one has a flat IFR and the other has a ramped IFR. So, back to my original question...

Should I be running a sloped IFR on a boosted L36 that was originally NA?

eclipse5302, I do plan to consider trying the L67 bin at some point, as there are a few things I could benefit from such as the MAP, and I think the spark tables also have better resolution just to name a few. I guess I don't mind reading my bin and it then say I have a 2002 Grand Prix GTP instead of a Monte Carlo. Before I make the change, I need to decide on the best bin match for my car as there was no 2002 L67 Monte Carlo :P I'll worry bout that later, but few to no people have told me to upgrade to a bin that supports 2 or more bars, so I question if it's really necessary for my car or not.

Krunch

Hmm. So how is the car getting more fuel / less timing with boost? Are you running a very small amount of boost? Do you have some other method you are using? I don't doubt what others have said, I just want to understand why that's all.

As for the best match, I would think that a 2002 / 2003 GTP bin would work fine, regardless on the make of car. I know it's not apples to apples, but my 1991 Cutlass Supreme is running a 2002 GTP L67 bin. Of course, the timing tables are from a 2005 GTP, and the VE and MAF tables have been tuned specifically to my engine since it's cammed.

[5_Liter_Eater]

You'll have to forgive me as I'm not familiar with these vehicles, but the concepts are the same. To be sure I'd hook up a fuel pressure gauge to verify whether fuel pressure is dropping with vacuum and increasing with boost. If it does then use a flat IFR with whatever number the spreadsheet gives you for 0 kPa. If it doesn't change then use a sloped IFR using the numbers from the spreadsheet.

I'm not sure why two cars with the same fuel system (return style, vacuum referenced) would have two different types of IFR tables. It wouldn't be the first time GM has messed up. There is no reason to increase IFR as vacuum goes up if the fuel pressure is physically being lowered.

Does the L67 bin have an IFR that covers vacuum and boost where as the L36 only goes from atmospheric to full vacuum?

[krunchss]

Those are very good questions eclipse that I'm afraid I don't have the answers too. It was originally a Cartuning turbo kit (I only say that when I have to) that I have added a liquid intercooler to, well, 95% complete. All I can say is that NONE of the Cartuning kits came with upgraded map sensors. Once people have gotten Kevin's crap tuning straightened out, some people have gotten the kit to work quite well. That's the best I can say. Someone else here might have a better answer for your question. I don't have a lot of knowledge of tuning past VE / MAF yet, I just really haven't focused on that yet until I can get my IC setup complete then do some VE / MAF tuning to straighten out my fuel which on average right now is pig rich without the intercooler. I figured I would jump into this thread as I hope to calibrate my IFR to my DIC soon before I start VE / MAF tuning, and if the sloped IFR was better for my boosted L36, better to make those changes now instead of backtracking later.

Krunch

Hmm. So how is the car getting more fuel / less timing with boost? Are you running a very small amount of boost? Do you have some other method you are using? I don't doubt what others have said, I just want to understand why that's all.

As for the best match, I would think that a 2002 / 2003 GTP bin would work fine, regardless on the make of car. I know it's not apples to apples, but my 1991 Cutlass Supreme is running a 2002 GTP L67 bin. Of course, the timing tables are from a 2005 GTP, and the VE and MAF tables have been tuned specifically to my engine since it's cammed.

[CTX-SLPR]

I don't know about the L67 tune starting since an L67 has a 4T65E and an L36 has a 4T60E which have some different stuff in and on them. I don't think he needs the BBV stuff that the L67 has so that's not a miss.

[krunchss]

Actually my car came OEM with the 4T65E but I have since upgraded to a ZZP trans with 2.92 and 3000 stall which is in essence a 4T65E-HD now with a 3000 stall. I don't follow what you're getting at that the IFR would be related to the trans however, and dumb question, what's BBV :P

Krunch

[krunchss]

Just an add to the post that eclipse made above...

You asked if my boost level was low? Depends on your defination of low...I run the 9 psi that Cartuning set this kit up at when I bought it. I'll see if I can safely up the boost later after I address other issues in this tune.

Krunch

[CTX-SLPR]

BBV=boost bypass valve

Trans relation, GM E-series transmission require trans specific programming meaning that an ECM with code for a 4T60E would not be capable of running a 4T65E. I didn't know that Monte's got 4T65E's as most L36 FWD cars had 4T60E's.

[mtcrusan]

Does the L67 bin have an IFR that covers vacuum and boost where as the L36 only goes from atmospheric to full vacuum?

I have an 04 L67 and the Injector Flow Rate vs. KPA VAC only goes up to 100 kPa. Mine is sloped.

[SMOKINV8]

I can't tell you exactly what to do on that one. If I were in your shoes, I would start with a sloped IFR and go from there. If you end up having to lean out the fueling tables (especially the MAF), then that should indicate you should be running a flat curve.

Here's a question for you. I know the L36's have a vacuum referenced FPR. Do the L67's as well? If they don't, that would certainly explain the discrepancy. Also, which FPR are you running on your car now that you're boosted?

[krunchss]

My car has no BBV then as OEM it was NA. Only the L67 (supercharged) would have this I expect.

Krunch

BBV=boost bypass valve

Trans relation, GM E-series transmission require trans specific programming meaning that an ECM with code for a 4T60E would not be capable of running a 4T65E. I didn't know that Monte's got 4T65E's as most L36 FWD cars had 4T60E's.

[krunchss]

If you're talking to me, my car after the turbo install still uses the OEM FPR. No replacement was included nor suggested with my turbo kit.

Krunch

I can't tell you exactly what to do on that one. If I were in your shoes, I would start with a sloped IFR and go from there. If you end up having to lean out the fueling tables (especially the MAF), then that should indicate you should be running a flat curve.

Here's a question for you. I know the L36's have a vacuum referenced FPR. Do the L67's as well? If they don't, that would certainly explain the discrepancy. Also, which FPR are you running on your car now that you're boosted?

[krunchss]

That's odd? You have an OEM boosted car and the IFR only goes to 100 Kpa? The GTPs IFR DOES go higher than 100 Kpa right? Your IFR ramp is what I expected from an L67 though.

Krunch

I have an 04 L67 and the Injector Flow Rate vs. KPA VAC only goes up to 100 kPa. Mine is sloped.

[5_Liter_Eater]

That's odd? You have an OEM boosted car and the IFR only goes to 100 Kpa? The GTPs IFR DOES go higher than 100 Kpa right? Your IFR ramp is what I expected from an L67 though.

Krunch

Thats 100 kPa of vacuum.

[n0dih]

It doesn't matter if it is returnless or not. Take the "mode" of all the LTFT values for each MAP range, 20-29, 30-39, etc, and then scale the fuel flow accordingly to bring it back to 0. Mine are extremely tight. I have a spreadsheet I plug the MAP values in and the existing table and it gives me a new table to put in. With this I can get my LTFT's within 2%, most often, 0-1%, it is rare to get out of that.

At low vacuum or high, most NEED to be scaled anyway. Has nothing to do with returnless or non returnless fuel delivery at all.

Yeah, it's not making sense to me either. I understand what is being said, but the L36 (3800 NA) and L67 (3800 SC) are both return fuel systems, and by that rationale should both have flat IFR. Although in practice, they don't...why not?

And krunchss, this may be a silly question, but if you've got the ability to tune, why are you still running a 1 bar MAP on a boosted engine? You could start with an L67 tune and work it from that, right?

[5_Liter_Eater]

While you may be able to gleem some results from that I think the method is a poor way to go about it. How do you know the fueling errors (fuel trims) are due to injector flow rate inconsistencies and not air metering inconsistencies. If you were running speed density then you could make up for incorrect IFR values (sloped when it should be flat or vice-versa, or just improper values altogether) with the VE table but if you're running a MAF then it's independent of RPM and MAP. So if you have stock injectors and put headers on you're telling me you're going to change the IFR table to get the trims back in line? The flow rate of the injectors hasn't changed.

There are two variables in tuning AFR; fuel and air. There are several tables you can edit to change the amount of fuel being injected but the IFR is not a good one to use. The injector flow rate is an equation. Assuming the injectors are clean and reasonably balanced then it doesn't make sense to change the IFR at particular MAP regions to deviate from that equation. Even if they are dirty and not balanced it doesn't make sense to try to make up for that be editing the IFR. Use the airflow table to change the amount of fuel.

[n0dih]

Exactly why I take the MODE of it, not the average/mean, that would toss you all over the place. Think of it as the coarse adjustment. Then once you are fairly tight with LTFT's then you make some fine adjustments if needed with MAF/Airflow tables. It is all math, just where do you change the values at. MAF/Airflow table should be last adjustment not first.

Look at it this way, our cars are tuned factory with real gas, not 10% ethanol gas, so in most cars the LTFT's are off out of the factory, just because some idiot politician decided that they know more about tuning cars than we do and force gas on us that we don't want. So tweak the Injector Flow to tighten up where it should be, and then you shouldn't even need to touch anything else.

Is there enough bandwidth in the PCM to handle 10% ethanol? Yes, the newer the better it handles it. But older PCM's don't handle it near as gracefully.... Which makes having a sloped injector flow rate so helpful.

While you may be able to gleem some results from that I think the method is a poor way to go about it. How do you know the fueling errors (fuel trims) are due to injector flow rate inconsistencies and not air metering inconsistencies. If you were running speed density then you could make up for incorrect IFR values (sloped when it should be flat or vice-versa, or just improper values altogether) with the VE table but if you're running a MAF then it's independent of RPM and MAP. So if you have stock injectors and put headers on you're telling me you're going to change the IFR table to get the trims back in line? The flow rate of the injectors hasn't changed.

There are two variables in tuning AFR; fuel and air. There are several tables you can edit to change the amount of fuel being injected but the IFR is not a good one to use. The injector flow rate is an equation. Assuming the injectors are clean and reasonably balanced then it doesn't make sense to change the IFR at particular MAP regions to deviate from that equation. Even if they are dirty and not balanced it doesn't make sense to try to make up for that be editing the IFR. Use the airflow table to change the amount of fuel.