2014 Silverado fuel system limitations with aftermarket camshaft

[Tick]

I have been researching this topic, but haven't found too much info. I'm tuning a '14 silverado that we have built a single turbo system for. We've had the truck on the dyno and it has made around 630 rwhp in 3rd gear.....realistically its probably making a good bit more than that. The injector duty cycle levels out at 31 percent regardless of how the maf curve is raised. I have raised the fuel pressure desired table by about 1000 psi in the area that needs more fuel and blended the table and I've also raised the HP Pump Max. I have read that 50% was the max for a DI injected engine.....if so what is holding us at 31%.

The truck has a comp cam with lobe number 21968 that supposedly increases fuel flow by 38%. I'm not really sure how that works and if there are any aspects of the tune that need to be changed to recognize the new pump lobe other than what I've already changed. I haven't played with injector timing at all yet.

Any advice would be greatly appreciated.

[Area47]

lean it out. You're too rich for a GDI system.

[Tick]

I know I can lean it out as far as commanded afr once the tune irons out.......but what about the actual 14:1 afr that it has at 6500 rpms with the current tune like it is?

[Mep_q8]

Soi.

[jarrah]

Lean it out 12.6 is safe with good reults log .......wat r ur cam specs seems abit of i tuned bolt on truck with playing with vvt gained 30whp on mustang dyno .....u need a dyno to get the most out of it how much boost r u running

[Tick]

Lean it out 12.6 is safe with good reults log .......wat r ur cam specs seems abit of i tuned bolt on truck with playing with vvt gained 30whp on mustang dyno .....u need a dyno to get the most out of it how much boost r u running

I'll lean it out, just wondering why the injector pulse width won't increase and the duty cycle won't increase beyond a certain point even with the MAF curve jacked way up. I increased the desired fuel pressure by 500 psi and the air fuel ratio did respond by dropping down to around 12.2 to 12.4:1 while the commanded was still 11.6. My desired fuel pressure up top is 24.95 MPa (3600 psi) and by the log the rail pressure is that.

I also changed the SOI by adding 30 so that the fuel would start to inject earlier. I haven't played with this yet other than the one change, but that didn't have any affect on the injector pulse width / duty cycle either. The pulse width will get as high as maybe 6.7 ms when the turbo first spools at lower rpms (and 30 or 31 % duty cycle) and then the pulse width gradually decreases the rest of the run while maintaining a 30 % duty cycle.......almost like there is a limit to the fuel flow somehow.

The cam is a 223/227 on a 114 +3. IVO .5* BTDC EVC 3.5 BTDC at .050 not taking into account the variable valve timing. The EVC is 24 degrees ATDC when open .010. Would it matter that the SOI takes place while the exhaust valve is still open? How high can the number be generally speaking....how high have others successfully ran the SOI?

We have a dyno.....I'm about to put the truck back on there. It has been on the dyno but we left it in 3rd gear to keep the driveshaft in tact. We have installed an aftermarket shaft now and will see what it will do in 4th gear which should be a better gauge of the actual power level we are at. After seeing two trucks spit driveshafts out over the years, I'm pretty hesitant to dyno a truck that makes 700+ rwhp and has wheel speeds of 150+ mph.

[Tick]

We are at 13 or 14 lbs of boost.

What would limit the injector pulse width to a certain value......just a limitation of direct injection in general? In other words why have I read that 50% duty cycle is basically maxed out, and why does it seem that 30% is maxed out for us on this truck?

It seems that we have the fuel pressure based on my latest logs that matches up with the desired table, so I don't think we're at any kind of limit in terms of pump yet.

And if the injectors are supposed to flow 96.5 lb/hr of fuel at the given factory pressure settings I wouldn't think we'd be anywhere near max on the injectors after increasing the pressure so much. Why would an LT1 engine have needed so much larger injectors than the truck at 121.1 lb/hr anyway also? Because they are direct injected and can only be open during a much shorter period of time? If 50% duty cycle is the max, does that mean that the flow rating of one of these injectors would be comparable to an injector rated half its size in an earlier style injected engine in order to determine the potential hp they could support?

[Higgs Boson]

I would say max is closer to low 40s and yes, direct injection has a very short injection window vs port. 336 would be the highest you could comand and ensure nothing goes out the exhaust, but I have seen much higher numbers than that, in the 400s.....it's only at higher engine speeds anyways, you won't have fuel loss through the exhaust valve at low RPMs or idle anyways. Even though the exhaust valve is open (almost closed), the piston is on the way down so it shouldn't affect you as much as a PFI where all the fuel is coming in much much earlier. I think SOI affects more spark timing advance-ability duty cycle.

I'd be careful with HPFP that high on the stock pump, even the Z06 bigger pump runs 2900. Not saying you can't bump it, but most use a cam lobe (like you are) or lash cap to increase it. I don't think just commanding in the tune is a reliable way to do it, IMO.

If I were you I would put SOI at like 400 in your problem area, command 12.5, command more like 2900 MPa, tune the MAF for it, and see where you get. There is a place in the Fuel System tab to specify the number of lobes on the cam, not sure if you adjusted that yet.

[Tick]

I would say max is closer to low 40s and yes, direct injection has a very short injection window vs port. 336 would be the highest you could comand and ensure nothing goes out the exhaust, but I have seen much higher numbers than that, in the 400s.....it's only at higher engine speeds anyways, you won't have fuel loss through the exhaust valve at low RPMs or idle anyways. Even though the exhaust valve is open (almost closed), the piston is on the way down so it shouldn't affect you as much as a PFI where all the fuel is coming in much much earlier. I think SOI affects more spark timing advance-ability duty cycle.

I'd be careful with HPFP that high on the stock pump, even the Z06 bigger pump runs 2900. Not saying you can't bump it, but most use a cam lobe (like you are) or lash cap to increase it. I don't think just commanding in the tune is a reliable way to do it, IMO.

If I were you I would put SOI at like 400 in your problem area, command 12.5, command more like 2900 MPa, tune the MAF for it, and see where you get. There is a place in the Fuel System tab to specify the number of lobes on the cam, not sure if you adjusted that yet.

Well, I took your advice and the truck went very lean. Duty cycle dropped to around 28%..... All the pulls I'd made to this point were short because it would go leaner than I like and I'd let off of the throttle almost immediately. I even fattened up the MAF table up top where its going to by 20%.

I might have a very basic, stupid issue with the MAF itself...... I've stayed in the throttle long enough a couple of times now to see that When the turbo spools the MAF frequency goes to 12,600 to 12,750 pretty quick and then it just stays there from 5400 rpms on up. I think the reason the duty cycle may not increase and the pulse width slightly decreases is the fact that the desired fuel pressure is increasing and the fact that its staying in those two cells in the maf table.

I've never tuned anything boosted with the MAF that has 'pegged' a MAF. I figured it would go all the way up the scale but is that value as high as it will go? Our charge pipe that the MAF is mounted in is 3" diameter so maybe that is the issue? All the boosted c6's and 5th gens I've done don't register than high on the MAF scale even making 750 to 800 rwhp with blowers....but the charge pipes are usually larger or the maf is mounted in the intercooler...? Bigger power than that or all of the earlier c5's and f-bodies I've usually gone to SD and haven't even tried to dial the MAF in.

[jarrah]

Well, I took your advice and the truck went very lean. Duty cycle dropped to around 28%..... All the pulls I'd made to this point were short because it would go leaner than I like and I'd let off of the throttle almost immediately. I even fattened up the MAF table up top where its going to by 20%.

I might have a very basic, stupid issue with the MAF itself...... I've stayed in the throttle long enough a couple of times now to see that When the turbo spools the MAF frequency goes to 12,600 to 12,750 pretty quick and then it just stays there from 5400 rpms on up. I think the reason the duty cycle may not increase and the pulse width slightly decreases is the fact that the desired fuel pressure is increasing and the fact that its staying in those two cells in the maf table.

I've never tuned anything boosted with the MAF that has 'pegged' a MAF. I figured it would go all the way up the scale but is that value as high as it will go? Our charge pipe that the MAF is mounted in is 3" diameter so maybe that is the issue? All the boosted c6's and 5th gens I've done don't register than high on the MAF scale even making 750 to 800 rwhp with blowers....but the charge pipes are usually larger or the maf is mounted in the intercooler...? Bigger power than that or all of the earlier c5's and f-bodies I've usually gone to SD and haven't even tried to dial the MAF in.

Put the SOI tables back to stock and try ......zero out ur wot vvt cam angles until 5600 and above put 4 deg .........do u have methanol injection u have some leaks check for that i had similar issue with a supercharged truck ended up intake leak.......also max maf freq under engine diag

[ayousef]

im running 14psi near redline with a whipple 2.9 and only go up to 10,600 hz on the MAF, this is with a Volant CAI. You might have to increase the charge pipe diameter as suggested. Based on the screenshot g/cyl is also going down hence why its running much more timing at higher rpms.

edit: I thought about this a little more and you are most likely pegging the MAF, despite the fact that we think it should go higher. try a 3.5 inch charge pipe, before you go a 4".

[Ben Charles]

Well, I took your advice and the truck went very lean. Duty cycle dropped to around 28%..... All the pulls I'd made to this point were short because it would go leaner than I like and I'd let off of the throttle almost immediately. I even fattened up the MAF table up top where its going to by 20%.

So you did what Higgs mentioned and added 20% MORE FUEL and you only hit 28% IDC???

IF your only hitting 12,700 Hz that's not a problem IMO, especially since its a 3" tube. The MAF maxes out Hz at 15,000 with a HIGH MAF fail at 14,500 which can be changed.

My desired fuel pressure up top is 24.95 MPa (3600 psi) and by the log the rail pressure is that.

NEVER seen anyone run that high of pressure on DI pump yet, but good to know you commanding that much and actually getting it. Shows, what I have been thinking about the HPFP as far as flow (cam helps here, curious how much can be gained without a Lobe or Lash cap) This setup is to be way north of 630rwhp

im running 14psi near redline with a whipple 2.9 and only go up to 10,600 hz on the MAF, this is with a Volant CAI.

That's a 4"tube, that's why you have a Hz lower than the original poster with probably similar power output.

[Tick]

I have played with WOT cam angles at a lower boost level on the dyno weeks ago (in 3rd gear) and I'm set on 1 in the table from 3200 rpms out. I played with it a good bit and the most it might have changed was 5 rwhp with 1 being the best if anything was even really better. It was hard to tell really with the truck blasing through the pull so quickly in that gear. The truck doesn't have meth.

Ben, I did change exactly what Higgs said to try and I raised the maf curve by 20% in the 12,750 cell and up on the maf curve. Then I went back down the table a ways and smoothed the curve to blend it in with the added 20%. This made that pull have a bit of a rich area where it was coming up in rpms and on the maf curve, then once it settles in the 12,600/12,750 cells it went to about 14:1 afr and 28 % duty cycle. When I had the truck on the dyno a few weeks ago I stopped messing with it for fear I was going to hurt something or break a shaft.....but what I change on the MAF table seemed to have no effect on the actual injector pulse or air fuel ratio in the 12,600 cell and up. I pretty much made the curve go up sharply at those cells and it still didn't raise the dc, pulse width, or lower the air fuel ratio. I wasn't logging the right fuel pressure parameters then and I hadn't messed with the SOI at all because I just didn't know what I was doing and I had other cars to tune. I've done some reading now and have a good driveshaft so here I am lol.

[Tick]

I'm going to make another change this morning that raises the maf table just in those cells to a stupid amount this morning and I'll post that tune file and a log. If that results in no change again I'll just start working on an SD tune. Either the MAF is limiting the fueling somehow or there is something in the tune that is limiting it. With fuel pressure responding to everything I've done so far I don't think I'm anywhere near out of pump and the DC is low so I should be good on injectors.

[Tick]

I raised the values in those cells this morning and the result was the truck went leaner than ever.....duty cycle and pulse width were lower than ever..... It went so lean the engine lost rpm/power. Why in the world would raising the maf data lower the pulse width and duty cycle from a prior run when the only change was the maf curve increased?

I had two other appointments today so I haven't had a chance to try tuning SD.

[Ben Charles]

I'll take a look when I get home

[Higgs Boson]

Are you logging fuel rail pressure? Is it going to 0? If so you are too rich and going lean because you are draining the fuel rails all at once. You're too rich when it hits PE it sucks the fuel right out of the system.

[Tick]

Fuel pressure was logged and it stays pretty much between 19 MPa and 21 MPa during the wot pull. IDC peaked at 28% as the turbo basically spooled and the rpms climb as it stretches the stall (which is WAY too loose). Once the stall was coupled for the most part (im forcing it to be unlocked now because it won't hold when locked) the IDC fell to as low ans 21 % and the truck stumbled because it was so lean. It definitely didn't go so rich it choked out or anything and the fuel pressure stayed steady as what it was desired to be.

[jarrah]

Fuel pressure was logged and it stays pretty much between 19 MPa and 21 MPa during the wot pull. IDC peaked at 28% as the turbo basically spooled and the rpms climb as it stretches the stall (which is WAY too loose). Once the stall was coupled for the most part (im forcing it to be unlocked now because it won't hold when locked) the IDC fell to as low ans 21 % and the truck stumbled because it was so lean. It definitely didn't go so rich it choked out or anything and the fuel pressure stayed steady as what it was desired to be.

Can u post a picture of ur setup maf location etc and how ur connecting to the tb

[ayousef]

Mass Airflow pegs at 655.35 g/sec at the exact moment where AFR starts to lean out, your problem is right there!

With my setup I reach 510 g/sec at redline and 14psi, so I still have room to go.

Gradually taper the PE curve from the point where it starts to lean out to about 9AFR (just to test).