Max rail pressure aftermarket injectors

[cadillactech]

For those of you who have calibrated cars with larger DI injectors like XDI's +30%, how far have you pushed rail pressure?
XDI notes that maximum pressure is 2900PSI "(tested rock solid on engine and roller dyno)" and the 3500PSI in perfect conditions.

I know that some people have had issues with stock LT4 injectors above 21MPa but wasn't sure if anyone has had issues with these higher than that? I think I remember Ben Charles posting he runs 24MPa regularly on stock LT4 systems.

I have a customer with a new to him ZL1 that has a 416 stroker with a big cam, 2.9L Whipple and from searching around in the calibration I pulled out of it, +30% injectors. It baselined at 725whp on another dyno before it made its way to me to fix a list of things including making more power and adding ethanol.

I haven't reached out to XDI yet but wanted to ask around if anyone has pushed the bigger injectors to 24MPa without issues as I think I am going to need all I can get if we add ethanol.

Thanks in advance!

[TriPinTaZ]

I've taken the XDI 30's to 22MPA before and didn't see an issue, but ultimately I backed them down to 21MPA because I was afraid of a misfire at WOT on a street car. Real quick way to blow up a motor. You could try 22MPA and see if there are any misfires after multiple pulls.

BTW, I'd recommend adjusting the Density Multiplier for WOT for those injectors. The stock table on some cars makes them inconsistent at WOT. I've got these injectors pretty stable on the ZL1 and Z06 platforms.

[cadillactech]

I've taken the XDI 30's to 22MPA before and didn't see an issue, but ultimately I backed them down to 21MPA because I was afraid of a misfire at WOT on a street car. Real quick way to blow up a motor. You could try 22MPA and see if there are any misfires after multiple pulls.

BTW, I'd recommend adjusting the Density Multiplier for WOT for those injectors. The stock table on some cars makes them inconsistent at WOT. I've got these injectors pretty stable on the ZL1 and Z06 platforms.

Thanks for the input Jason.

I chatted with someone at XDI and they said the same thing basically. No need to risk it, I will put the ceiling at 21MPa and see how much ethanol it will take.

Are you seeing the density multiplier need to be increased past the 1.0 in the tables in the WOT areas? Does XDI not supply this data with their injectors?

[GHuggins]

Nobody supplies the density info cause everything motor wise changes it. This is a screenshot of the same set your referencing that I'm still smoothing out for these same injectors. I've heard of people having issues with them around 16 to 18Mpa and if you look at the density table it starts to make sense. You'll need to also dial in your rail pressure multipliers to get "everything" in line. I'm running these to 21Mpa. Everything will change the density settings from the engine build cause of how air is flowing into the combustion chamber and the effects of compression from that point. This is why I dial in density for every major engine mod. Hotter temps are actually where I had to add a lot of fuel back in and then took out of the colder temps.



density +30% 427.jpgdensity +30% 427 2.jpg

[cadillactech]

Nobody supplies the density info cause everything motor wise changes it. This is a screenshot of the same set your referencing that I'm still smoothing out for these same injectors. I've heard of people having issues with them around 16 to 18Mpa and if you look at the density table it starts to make sense. You'll need to also dial in your rail pressure multipliers to get "everything" in line. I'm running these to 21Mpa. Everything will change the density settings from the engine build cause of how air is flowing into the combustion chamber and the effects of compression from that point. This is why I dial in density for every major engine mod. Hotter temps are actually where I had to add a lot of fuel back in and then took out of the colder temps.



density +30% 427.jpgdensity +30% 427 2.jpg

Looks like Lingenfelter provides this data with their injectors but I know there are really impossible to get ahold of for support. Would you say this data isn't correct?

My understanding of these tables is that they are characterized by the injector manufacture and shouldn't change, that they are independent of the engine they are in but I certainly am open to being wrong.

Are you logging lambda error over this table and using that as your correction factor?

I don't know which manufacturer these injectors are yet as I haven't tried using a scope to see or pulled the Whipple yet but I may do that just so I know. Also, sounds like the Whipple front snout bearing is coming apart so we may need to rebuild or switch to a 2650 soon.

Thanks guys for all the input, much appreciated!

[GHuggins]

I don't care how precise you dial in the VE - cause I get it really precise with cam movement and all or how much you dial in the open loop adders - cause again I dial those in too. EVERYTHING and I do mean EVERYTHING changes the density table from injection timing to mechanical changes. I use a simple math formula to dial it in using trims and then a wideband for PE to fine tune fueling and keep wot fueling right and then I have a very specific process for doing the rough dial in using trims. All I can say is once it's dialed in, cold starts, drivability, torque control and a lot of those things seem to mostly fall right in line.

I would say if Lingenfelter supplies the data it should be close enough to drive around and fine tune on but again everything seems to change it. It is also a very time consuming process if you're starting from scratch.

[TriPinTaZ]

Thanks for the input Jason.

I chatted with someone at XDI and they said the same thing basically. No need to risk it, I will put the ceiling at 21MPa and see how much ethanol it will take.

Are you seeing the density multiplier need to be increased past the 1.0 in the tables in the WOT areas? Does XDI not supply this data with their injectors?

I agree with everything Greg has said. He's right on the money. The issue with the Density Table at WOT with the XDI injectors, some cars have large changes between cells. Say 20mpa at injector tip temp 170 is greatly different than 19mpa at 170. This causes the WOT fueling to bounce around a lot or trend in a direction. I would make a correction for the car going rich and then a couple of pulls later it was lean in that spot. It just made things inconsistent as the swings were too large. If you look at Greg's images above, that is essentially what my Density Table looks like in the WOT area.

The normal operating range (temp and pressure) have the highest peak. Then as the injector temps get warmer, the value decreases a bit, just like the stock logic, but stock was based on injectors that flowed less volume. The reason here is that when coolant temps are up, usually intake or blower temps are too so you get less air into the cylinders and need slightly less fuel. And on the flip side, when its cold out and the injector tip temps are low, usually the MAF reads a lot more airmass due to the cold dense air. If you set everything to 1.0 in the WOT density on boosted stuff, you will have a hard time maintaining the commanded Lambda in different temp and weather scenarios. NA stuff is a bit more forgiving and a lot of those cars just have 1.0 in the density table at WOT which is fine.

Greg has a lot of time invested in Density Multiplier and is very knowledgeable here.

[cadillactech]

I agree with everything Greg has said. He's right on the money. The issue with the Density Table at WOT with the XDI injectors, some cars have large changes between cells. Say 20mpa at injector tip temp 170 is greatly different than 19mpa at 170. This causes the WOT fueling to bounce around a lot or trend in a direction. I would make a correction for the car going rich and then a couple of pulls later it was lean in that spot. It just made things inconsistent as the swings were too large. If you look at Greg's images above, that is essentially what my Density Table looks like in the WOT area.

The normal operating range (temp and pressure) have the highest peak. Then as the injector temps get warmer, the value decreases a bit, just like the stock logic, but stock was based on injectors that flowed less volume. The reason here is that when coolant temps are up, usually intake or blower temps are too so you get less air into the cylinders and need slightly less fuel. And on the flip side, when its cold out and the injector tip temps are low, usually the MAF reads a lot more airmass due to the cold dense air. If you set everything to 1.0 in the WOT density on boosted stuff, you will have a hard time maintaining the commanded Lambda in different temp and weather scenarios. NA stuff is a bit more forgiving and a lot of those cars just have 1.0 in the density table at WOT which is fine.

Greg has a lot of time invested in Density Multiplier and is very knowledgeable here.

Right on, this is very helpful.

Once we get this Whipple noise figured out I will see how it behaves on the dyno and make sure to look at the Density Tables, they look stock compared to base file so these could be XDI injectors.

The flow rate is 177.3 vs stock 140.7 so 26% increase, I am going to try and get a look at the injector to verify the actual manufacturer. Not ideal when customers have a build this big and we have no documentation.

Thanks Greg and Jason!

[GHuggins]

Thanks Jason.

Though, time invested may be an understatement. That above posted table probably had 40 hrs of elevated idle time dialing it in. It was a pita. Would make a change - overshoot - then slowly settled out after several revisions for each rail pressure - those were some touchy injectors at times and other times wouldn't change at all just depending on the pressure. I've probably got a few hundred hours into just coming up with the ideal method for modifying it and getting it right, BUT I can say once you get the base tables for certain mods like cams or combo setups like cam heads and so on they'll just about work with the same other mods motor wise minus doing some minor fine tuning to it for each setup. LT4 injectors probably stay the most consistent for engine mods - guess that's why you can take the lt4 density settings and transfer them with the injectors fairly easily - still requires modding, but doesn't have the "big" changes like other injectors do... 6.2 lt1 injectors on the other hand takes big modding - they're also the ones that fail a lot, so maybe something there as a design flaw? I've fixed a lot of stalling and weird drivability issues dialing in the density tables. Even took it to another level and will shape the air models mostly how I like them and then dial the density table in to make torque and everything work better. NOT CORRECT, but it works great on the one's I've done it to. I just look at the density table as another VE table.

AND just to clarify, I haven't found a way to multiply by errors on the table just for the fact that certain rail pressures behave differently than others and due to the nature of the beast you have to use an inverse to make changes. My formula adds to the existing table. Subtracting from adds fuel, adding to takes fuel away. The same way nearly all of the fuel multipliers works on fifth gens. I will also say the formula allows you to modify the other multipliers the same way for things like the E multipliers for example.

[TriPinTaZ]

AND just to clarify, I haven't found a way to multiply by errors on the table just for the fact that certain rail pressures behave differently than others and due to the nature of the beast you have to use an inverse to make changes. My formula adds to the existing table. Subtracting from adds fuel, adding to takes fuel away. The same way nearly all of the fuel multipliers works on fifth gens. I will also say the formula allows you to modify the other multipliers the same way for things like the E multipliers for example.

So I seem to have found that adding to the Density Multiplier adds fuel and subtracting removes fuel. At least at WOT. Initially I thought the reverse would be true, thinking that the multiplier was saying the fuel injectors were X amount of the base size defined in the tune as the flow rate. A larger number would mean the injectors were larger so lower the pulsewidth which would mean less fuel. But everytime I tested, a lower value in the Density table would result in a leaner Lambda value.

I tested 1.00 vs 1.005. 1.00 gives me a lambda of .85-.86 and 1.005 gives me a lambda of .83-.84. No other changes were made. Am I seeing the lambda swing due to something else and it just happened to skew my testing?

[GHuggins]

So I seem to have found that adding to the Density Multiplier adds fuel and subtracting removes fuel. At least at WOT. Initially I thought the reverse would be true, thinking that the multiplier was saying the fuel injectors were X amount of the base size defined in the tune as the flow rate. A larger number would mean the injectors were larger so lower the pulsewidth which would mean less fuel. But everytime I tested, a lower value in the Density table would result in a leaner Lambda value.

I tested 1.00 vs 1.005. 1.00 gives me a lambda of .85-.86 and 1.005 gives me a lambda of .83-.84. No other changes were made. Am I seeing the lambda swing due to something else and it just happened to skew my testing?

Might just be coincidence with belt slip or something else - which seems to be a regular problem on the lt4's. Even in PE adding to should remove fuel. I've got one lt4 I'm tuning here recently that just showed 6% lean out of the blue, but it was also showing more airflow in general. I find it best to look at airflow and fueling errors together when making these adjustments. For example this same car suddenly started showing higher boost kpa readings and less airflow a few weeks back. Owner went over it front to back and found nothing. Density table and MAF were both dialed in and keeping less than a 1% error until todays log he sent me. It was suddenly back to showing the airflow it used to have and 6% lean. I still think belt slip or something in the exhaust, but can't say for sure. He did say the belt was 2yrs old, so there's that...

Plus a .005 should be a 5% change - roughly... I'm pretty sure there are also other changers in the cal that we can't change, so that may have been playing in your case as well?

[TriPinTaZ]

Might just be coincidence with belt slip or something else - which seems to be a regular problem on the lt4's. Even in PE adding to should remove fuel. I've got one lt4 I'm tuning here recently that just showed 6% lean out of the blue, but it was also showing more airflow in general. I find it best to look at airflow and fueling errors together when making these adjustments. For example this same car suddenly started showing higher boost kpa readings and less airflow a few weeks back. Owner went over it front to back and found nothing. Density table and MAF were both dialed in and keeping less than a 1% error until todays log he sent me. It was suddenly back to showing the airflow it used to have and 6% lean. I still think belt slip or something in the exhaust, but can't say for sure. He did say the belt was 2yrs old, so there's that...

Plus a .005 should be a 5% change - roughly... I'm pretty sure there are also other changers in the cal that we can't change, so that may have been playing in your case as well?

I'll have to go back and make some larger changes and see what the results are. This is only in 2000+ PSI area's. Initially I kept making the number smaller because logic would make sense that a smaller multiplier would tell the ECU the injector is smaller and it would then inject more fuel. I'll do some more testing and check for belt slip and verify the SOI/EOI is the same. I know if the SOI changes too much it will show up on the wideband. The Air Density also makes a difference as you will see the same or similar KPA but the airmass will change and fueling will be referencing a different part of the MAF, which will change reported Airmass. I didn't look at these things closely enough in my initial testing. I'll be paying much more attention to this. I have a Z06 and a ZL1 to tune this week. Perfect time to test.


The PE table, on the LT4's its actually inverse from Commanded EQ. A higher value = more fuel. On the LT4 stuff the EQ table would work as the following and its reflected in the Commanded EQ PID.
(Assuming you're using a sliding Flex Fuel variable Stoich table)

PE Table set to 1.2: 14.68/1.2 = 12.23 Commanded AFR Commanded EQ PID will show .836
PE Table set to 1.15: 14.68/1.15 = 12.76 Commanded AFR Commanded EQ PID will show .869

[TriPinTaZ]

Confirming Greg is correct. A lower number in the density table is richer. .005 is about 5% as mentioned as well.

[GHuggins]

The 5% part depends on rail pressure and injectors. The bigger AM injectors for example - well small changes like that won't make diddly squat of a difference at the higher rail pressures, which is why we might have to tweak the rail pressure multipliers at the same time, but will make "some" difference at the lower rail pressures. I still don't have a way to 100% accurately log for density corrections - think it would require averaging and a lot of functions to kick the out liars out such as decel and so on. Other than that I can mostly calculate it out with normal driving and keep the trims to a 1 to 2 % swing from freezing cold to scorching hot temps.

Also once you figure out the affects or how the changes relate to percentages and how to apply those errors, well all the other multipliers work the same way in the genV's... Gen4's too, but the opposite on them Always wondered how to dial the open loop tables in on the gen4's. Now I know....

Keeping my finger's crossed on this one, but if GM is using sonic airflow to define throttle opening, my coding expert may have found the TB table for converting NA's to Boost..... Wish I knew how the heck to calculate sonic airflow, but looking at the lt4 table vs the stock trucks and doing a little research into sonic airflow, some things are making sense. May still be barking up the wrong tree, but if they are using sonic airflow then pressure ratio and vacuum alike are already calculated into it not to mention temperature and density calcs which would explain everything with the lt4's being able to control throttle with boost.

Anyone know how to convert g/s, map kpa, temperature and so forth into sonic airflow Anybody know for sure that's what GM is using?

[TriPinTaZ]

The 5% part depends on rail pressure and injectors. The bigger AM injectors for example - well small changes like that won't make diddly squat of a difference at the higher rail pressures, which is why we might have to tweak the rail pressure multipliers at the same time, but will make "some" difference at the lower rail pressures. I still don't have a way to 100% accurately log for density corrections - think it would require averaging and a lot of functions to kick the out liars out such as decel and so on. Other than that I can mostly calculate it out with normal driving and keep the trims to a 1 to 2 % swing from freezing cold to scorching hot temps.

Also once you figure out the affects or how the changes relate to percentages and how to apply those errors, well all the other multipliers work the same way in the genV's... Gen4's too, but the opposite on them Always wondered how to dial the open loop tables in on the gen4's. Now I know....

Keeping my finger's crossed on this one, but if GM is using sonic airflow to define throttle opening, my coding expert may have found the TB table for converting NA's to Boost..... Wish I knew how the heck to calculate sonic airflow, but looking at the lt4 table vs the stock trucks and doing a little research into sonic airflow, some things are making sense. May still be barking up the wrong tree, but if they are using sonic airflow then pressure ratio and vacuum alike are already calculated into it not to mention temperature and density calcs which would explain everything with the lt4's being able to control throttle with boost.

Anyone know how to convert g/s, map kpa, temperature and so forth into sonic airflow Anybody know for sure that's what GM is using?

Maybe that is why I wasn't seeing discernable changes in Injector Density on my setup. I'm running the LPE pump and XDI 30's so the pressures and other things are not OEM settings. But when I was tuning a ZL1 last night with stock injectors, the Density Table had a much larger effect. This was all in the WOT are by the way.

As for your coding guy, hopefully you can have HPTuners add these tables for the rest of us lol. But I understand if you keep the edge to yourself. Maybe you can see if they can get some more DFCO tables as well? Specifically the DFCO entry/exit time like we have on the Gen 4 stuff. I don't tune anymore Gen 4's as I have enough Gen V work and I enjoy the newer stuff. It's been years since I touched any Gen 4 stuff. Funny thing is I was helping a buddy with his Gen 3 the other day and I was like hmmmmmmm now which table did I use to fix this in the past. I forgot lol.

Sonic airflow yikes, might need some serious tools for that. Mike at Soler is that kind of engineer, he may be able to shed some light if he is willing. He's a smart guy.

[GHuggins]

Maybe that is why I wasn't seeing discernable changes in Injector Density on my setup. I'm running the LPE pump and XDI 30's so the pressures and other things are not OEM settings. But when I was tuning a ZL1 last night with stock injectors, the Density Table had a much larger effect. This was all in the WOT are by the way.

As for your coding guy, hopefully you can have HPTuners add these tables for the rest of us lol. But I understand if you keep the edge to yourself. Maybe you can see if they can get some more DFCO tables as well? Specifically the DFCO entry/exit time like we have on the Gen 4 stuff. I don't tune anymore Gen 4's as I have enough Gen V work and I enjoy the newer stuff. It's been years since I touched any Gen 4 stuff. Funny thing is I was helping a buddy with his Gen 3 the other day and I was like hmmmmmmm now which table did I use to fix this in the past. I forgot lol.

Sonic airflow yikes, might need some serious tools for that. Mike at Soler is that kind of engineer, he may be able to shed some light if he is willing. He's a smart guy.

I feel like I keep hijacking threads by changing the subject, but the throttle table worked. Not perfectly, but when combined with some DD tweaks and throttle progression tweaks it just about had this crazy trucks throttle under complete control. I had to make a 70% pedal correction as it was opening up to 100% there at 100+ Kph with constant held throttle at that position.

I don't have a clue about how to calculate sonic airflow, but moving the table how the lt4's shifts it even further seems to have done the trick.

My coding person - Will_974 on here - is opening up an online store for creating the tables and making them available to everyone via the user defined parameters access point. That's what I've been using to make the changes. I don't have a clue how to hunt down and find the tables much less how to set them up to use in hpt. I just know how to edit them after the fact The dfco tables are there along with some others she's hunting down and adding in if you need any of these. Reasonably priced too considering.

The throttle progression table alone controls a sheet load. It's used for dfco, idle torque and timing, neutral free revving, throttle control and so on. I used it to get rev matching back in line on a 22 zl. Guy said it never had worked right since the first tuner worked on it or since the car was modded as far as that goes. Even having the lower area of the torque model right didn't have it working right. Adjusted the throttle progression table a touch and back to working perfectly, so I was happy about that. The idle torque and timing influence is interesting too.

The throttle rate table is the reason you aren't changing the etc scaler although I don't think changing the etc scaler is a bad thing now that I understand this a little better. It's the one that seems to be using sonic airflow as it's units. Or I assume that's what it's using especially since all of the patents hing around that for tb control?

Back to subject. Yes if stock injectors then the correction formulas will work correctly. I do half lambda corrections until the MAF is really close then correct the MAF by adding to it only. If it's wanting a chunk of fuel removed I do that via the density table.

Now back off subject Yes I know what you mean about the gen3's. I've had to do a few here recently due to my drivability reputation. All I can say about that is I've forgotten a whole heck of a lot more than I still know.... LOL... This is why I like the forums and the "how to's". Even if they're some you yourself typed up or someone else. Just go read them then the memory slowly comes back a little

[TriPinTaZ]

The throttle rate table is the reason you aren't changing the etc scaler although I don't think changing the etc scaler is a bad thing now that I understand this a little better. It's the one that seems to be using sonic airflow as it's units. Or I assume that's what it's using especially since all of the patents hing around that for tb control?

The simple answer for me is that changing the scaler more than just a little, always introduced torque model issues somewhere else along the line. I got good at lining up Airmass, VVE and adjusting Virtual Torque as needed. Then I would change the scaler just a little at the end. Honestly, I only change the scaler for the "BRAPs" lol. Once the car is dialed in, you can move this value a little bit to get the up shift and down shift Braps to be more pronounced on Automatic cars. I know it sounds dumb, but I swear it works lol

Thanks for the heads up on the User Defined Parameters. I actually installed Tuner Tools and was messing with finding tables. But its time consuming to poke around. If someone has already done the leg work I will gladly pay a fee to access those tables and save myself some time.

[GHuggins]

The simple answer for me is that changing the scaler more than just a little, always introduced torque model issues somewhere else along the line. I got good at lining up Airmass, VVE and adjusting Virtual Torque as needed. Then I would change the scaler just a little at the end. Honestly, I only change the scaler for the "BRAPs" lol. Once the car is dialed in, you can move this value a little bit to get the up shift and down shift Braps to be more pronounced on Automatic cars. I know it sounds dumb, but I swear it works lol

Thanks for the heads up on the User Defined Parameters. I actually installed Tuner Tools and was messing with finding tables. But its time consuming to poke around. If someone has already done the leg work I will gladly pay a fee to access those tables and save myself some time.

Actually makes sense. I posted way back and again about a year ago I guess what changing the etc scaler has affects wise to how the tb performs. Smaller than actual closes slower and opens quicker whilst larger than actual closes quicker (for that better choke off for your pops) and opens about the same to slightly slower than a "correct" setting. It used to - at least on the 4th gens - I have not reconfirmed on the 5th gens - but it used to also change or I guess rather affect transient and regular fuel calculations. This was especially evident on the 3rd gens as well. It would change wot fueling on them a decent amount for some reason.

William said just about everything in the coding or at least a whole lot of the coding was tied to that throttle rate table. I would think the etc scaler would have to be tied to it too.

[1scls1z]

For those of you who have calibrated cars with larger DI injectors like XDI's +30%, how far have you pushed rail pressure?
XDI notes that maximum pressure is 2900PSI "(tested rock solid on engine and roller dyno)" and the 3500PSI in perfect conditions.

I know that some people have had issues with stock LT4 injectors above 21MPa but wasn't sure if anyone has had issues with these higher than that? I think I remember Ben Charles posting he runs 24MPa regularly on stock LT4 systems.

I have a customer with a new to him ZL1 that has a 416 stroker with a big cam, 2.9L Whipple and from searching around in the calibration I pulled out of it, +30% injectors. It baselined at 725whp on another dyno before it made its way to me to fix a list of things including making more power and adding ethanol.

I haven't reached out to XDI yet but wanted to ask around if anyone has pushed the bigger injectors to 24MPa without issues as I think I am going to need all I can get if we add ethanol.

Thanks in advance!

I have found XDI +30's are solid to 2900psi but the FIC +30's are hit and miss. I run a LPE HPFP @ 2500psi with XDI +30's using stock LT4 density table and don't have any issues with AFR changes in different conditions.