So we're adding a auxiliary pump to a LT4 car. What should I change in the tune to take advantage. I'm guessing I can add low side fuel pressure to keep the high side feed better. I've got a few ideas I just want to make sure I don't mess anything up.
you dont change anything in the tune as the aux pump isnt getting controlled by the ECU. You set your FPR and hobbs switch to whenever you want it to come on
I was looking to find out if there is a certain field in the fpcm that I should be messing with.
Interested in this as well. I will be installing a DSX aux pump and was under the assumption some values in the FSCM would need changed. Anyone have input?
need to adjust some settings in the fpcm to allow the added fuel psi that the aux pump is going to supply
I'm assuming a DSX kit here...
The real key is table ECM 6975, make sure the hi flow areas are at least 500 kpa. Then ECM 7030 make sure it's at least 500kpa as well. If you want it to enter "hi flow" more often you would decrese numbers in ecm 17022, and to come out of hi flow easier increase 17023.
With factory tune settings an LT4 SHOULD kick on the dsx kit when flow rates match.
I'm in DSX Tuning auxiliary pump hell myself right now. I just installed one as part of a supercharger upgrade on my 2017 ZL1.
In the logs, I've noticed a few issues.
- When the aux pump kicks on, the in-tank pump backs off in an attempt to maintain the desired fuel pressure. However, when the aux pump suddenly turns off, the pressure dips significantly before the in-tank pump has the chance to get back up to speed. There's probably a way to tune around this, but I wish the DSX kit would just use a PWM pump and phase out slowly.
- Sometimes, mid pull, I'll see dips in fuel pressure. It's not because the pumps can't keep up with the load because the pressure will recover on its own within the same pull. Something else is going on.
Sevinn, do you know what happens with the values in the Maximum Desired Pressure table (6975) are exceeded? I'm wondering if my dips in fuel pressure mid-pull might be related to exceeding the limits here.
I'm working on one in a 5gen Camaro and will be doing a C7 next week if all goes well. The most I can get our of DSX is you have to increase the minimum flow tables. So when the pump kicks on and adds pressure and the stock pump backs down to compensate you just don't give it the chance. By increasing the min flow tables the stock pump just can't pull enough pressure out. I haven't taken this to the genV platform yet but we'll see what happens.
How far are you exceeding them? That table I feel is a bit mislabeled as it acts more like a floor for desired pressure.Quote:
Originally Posted by travislambert
You can play with Open Loop DC on the in tank pump to offset it a litte, but the aux kits will always hit kind of hard.Quote:
Originally Posted by JASON11WS6
Quote:
Originally Posted by sevinn
I see spikes at around 600 kPa, but mostly I see 550 kPa where the max is set to 500 or so. I'm sure the mechanical pressure relief valve is probably opening near 600 occasionally.
The problem is my setup is relatively mild. When the aux pump kicks on, the primary pump basically has to wind down to its minimum duty cycle and often there's still too much pressure. When the aux pump turns off, I get a momentary pressure drop because my primary pump is basically off and has to spin back up. If I bump the min DC up, then I'm back at too much pressure.
These aux pumps sound like a good idea in theory, but when you get into the details all they do is confuse the crap out of the primary pump logic. It'd be much better if the aux pumps were variable output and pressure controlled.
I've ordered a new aux pump with a lower flow rate in hopes that I can keep the primary pump moving more fuel without too much pressure.
Talking to DSX, I guess I'm "patient zero" for having these issues. Apparently every other aux pump just works absolutely perfect in all scenarios. (In other words, they offered zero assistance.)
https://dsxtuning.com/blogs/dsx-tech
Maybe this will help?
Quote:
Originally Posted by NotSure
DSX just sent me that when I asked for help. I'm getting enough fuel but I still don't like how the pressure drops. I'm asking for 550 on the high flow table which seems to be kicking in around 5k for me now. So I think I have everything where I want it but the pressure still drops to around 300kpa. I'm tempted to unplug it and see if I get the same numbers. I've just been raising the minimum tables for the pump. Raising the floor if you will. Has anyone been able to maintain 500-550kpa with one of these pumps? Any secrets?
I eventually dialed mine in to give the appearance of working after many hours and hundreds of dollars in dyno rentals. I had to bump up the requested pressure as you have done as well as play with the minimum tables. You have to be careful with the minimums though and only change numbers > the requested pressures but also leave the last column at max pressure alone. Otherwise your pump can get stuck at a high pressure when you go from high flow demand to a low fuel demand. (It happened to me while testing.) It's a delicate balance that will never be perfect, but you can get it close.
After getting everything dialed in, I took my car to the road course and discovered a huge design flaw with this kit. In my case, my car has a saddle tank (2017 Camaro ZL1). When you go around a right turn hard with less than a 1/2 tank of fuel, all of the fuel transfers to the left side of the tank... seriously, all of it (I logged the fuel level sensors in both sides of the tank). So if you take a hard right turn and then get on the throttle (with less than 1/2 tank of fuel), the car will run out of fuel and go lean because there is no fuel available to the aux pump where the tank is tapped. At this point, you're running on the in-tank pump which is also less efficient when fuel is only present in one side of the tank. The pump will struggle to keep up, pressure will drop, and once the fuel bucket on the in-tank pump is dry you'll run completely out of fuel... happened to me... over and over again until I figured out what was going on.
After discovering this, I couldn't rip this piece of junk off my car fast enough. If anyone is putting together a museum of poorly engineered aftermarket parts and would like to buy my kit for a 2016+ Camaro, I have one I'll sell really cheap. PM me.
Anyway, in my case, I installed a JMS voltage booster. At 17.5v, I have perfect fuel pressures again and all is well. Overall I'm happy with their kit, but it does triple the current draw on the battery while the car is not in use. The JMS unit alone uses about 20 mA constantly, which is waaay too much. If you don't use your car often, you'll need to keep a charger on the battery. I would wire up a simple relay, but GM expects power to be present to the FPCM all the time. If you kill the power to the booster, this also would kill the power to the FPCM which will trigger the MIL light. My plan is to rig up something to with heavy duty diodes to kill power to the JMS booster when not in use while keeping power to the FPCM at all times.
Youo guys looking to boost the low side also need to remove the stock check valve from the line at a minimum. I have gone as far as mounting my flex sensor off the stock pump then where the secondary pump I run ties into the line I ran 8 an all the way to a russell check valve then to my mechanical pump. So this is like the max setup for the low side. I command 80 psi on the stock pump and my aux is setup that way and it holds 80 psi through a full pull on a car running heads and a cam with 32 percent lobe running full pump e85 with zero drop on low or high side. I do run meth on it but have gone as far as cutting it to 50/50 as I no longer need so much of it to suplement the fuel system. If your familiar with the stock check valve on these cars you know its about the size of a marker tip where it passes through on the check valve. So it has to be cutting a ton of fuel from making it to the pump. My low side has no issues holding that 80 psi now by adding the 8an line but even if just remove the stock valve and run with out any it will work and work much better. I ran the russell valve as it is not restrictive and was cheap through amazon or I would have just gone with out it on the car. No way I was paying 200 bucks for the lingenfelter one that I had heard a few ran with it and with out any and saw no change at all on the car. I guess the russell was cheap insurance on it so just went with it.
You also have the 30% injectors right?Quote:
Originally Posted by lt1z350
Didn't GM correct the check valve issue from 2017+?
Yea I have the fuel injection connection injectors. On 16 psi with the cam and heads now at e80 I’m at 4.9 ms in the injectors. So I have some room still on it. I even cut the meth down to 50/50 so to cool more.Quote:
Originally Posted by HeavyChevy305
I didn’t think gm changed anything on the check valve. I hear a lot of guys do not even run it now. I was told some newer z06 might not even have it factory. That or they moved it on the line and the person who told me was looking at other pictures. But doing the low side makes a good difference on high side. Seems this pump has to be fed by volume not just pressure. Back in the early 2000s we had a lt1 on a procharger had stock fuel lines with 2 in tank pumps and a third in line one of the nos booster pumps fro
Those kits. Car was still going lean in high rpm though pressure held 45 psi. We took a big single pump through it in a bucket full of fuel and put a big 8an line to the rail. The car picked up 75whp. 1997 lt1 camaro 383 stroker on 12 psi 850whp back then. Just showed how the larger line more volume is needed though pressure was stable still. I kept thinking back to that car with this one and thought how is it even possible it makes this power on a tiny 3/8 line. So did the 8an stuff and it has paid off. I have heard of guys saying took the valve out and even on the stock line the high side picked up 400 psi on a case where it was running low and just doing that got it back to commanded pressure. Granted you can get away with less then 3000 psi. I ran mine down to 2400 plenty of times injectors at 7.0 ms which is too much but it still trapped 140 mph. Now if someone came up with a decent high side pump as I’m not paying 1700 for a lingenfelter that give me 10 percent. Even now I command 3000 and see it go to 3150 randomly so the low side is really helping the high side so much more it goes up and over commanded more so then not.
Quote:
Originally Posted by lt1z350
You're pushing your stock low side to 80psi constant or only under high flow conditions? I thought they over heat?
That 8an line you're running from the aux pump goes straight to the high side rail?
*edit* just found a thread on the other forum. Lot's of good info on this topic.
Quote:
Originally Posted by HeavyChevy305
Where is the other thread you found? I'm interested in what you found.