Live action from FUMANCHU182.

[jonx96]

I haven’t looked at the logs but idling at 50 injector percent duty cycle is not normal at all

 

[fumanchu182]

Thats pump duty cycle my bad, not inj duty cycle.

 

[Speedy!]

My fuel pump DC is 45-47% on E85 at idle so I'd say that's fine. At WOT mine's around 80-82% in good air.

 

[fumanchu182]

My next check will be Friday at MIR, I'll let yall know how it goes.

 

[zhc]

You're actually not dropping that much fuel pressure but you also don't have a lot of injector head room to cover for it. Even if it maintains 80+ psi, you'd probably run out of injector in negative DA as it stands.

With that said, I would add a single bap plugged into the slave fpdm. That'll fix your fuel pressure issue for the time being. You might have to add a 2nd one when the air gets cold if you stick to this configuration. You can also target higher fuel pressure during WOT operation but that'll just cause the fuel pressure to drop faster once pump flow is mechanically maxed out.

Your bypass valve is also on the verge of triggering a limp mode condition. This is typical whenever pushing over 21 psi of boost. As you mentioned, it is just an srt4 throttle body after all, not really designed for this use case. There are companies out there that sell modified bypass valves with a stronger motor. Either lower boost or upgrade your bypass if you want to avoid future frustrations. You could also take a chance that another bypass might be a little stronger but it could also be weaker. I don't recommend that route for you given where you're at with this car.

Your 1-2 2-3 short shift issue, that's weird. It's not skipping 2nd gear though, it can't physically do that, but it's triggering the 2-3 shift right after completing the 1-2. As to why, I couldn't tell ya. It's not something I've seen before which would be kind of odd don't you think?

 

[zhc]

Im on the virge of making a window so time to tone it down.

I concur. A lot of your issues will go away if you turn it down as well.

 

[jonx96]

@zhc @fumanchu182
DCR racing (you probably know him from his light weight batteries) sells a return system for the stock fuel system. He claims it will give more pump over head than a BAP. I have thought about testing it but havent seen him at the track in a month or 2 to talk to him more about it. I’m just not aware of any comparison data.

 

[zhc]

@zhc @fumanchu182
DCR racing (you probably know him from his light weight batteries) sells a return system for the stock fuel system. He claims it will give more pump over head than a BAP. I have thought about testing it but havent seen him at the track in a month or 2 to talk to him more about it. I’m just not aware of any comparison data.
View attachment 75597

People don’t typically invest in a full return style system at this power level, mainly due to cost, so I can’t really comment on DSR’s product offering. I don’t have enough data to draw meaningful conclusions about how much it would enhance a stock style setup. I do know that at higher power levels even on a full return style fuel system, using traditional Walbro pumps may require baps to meet fuel flow requirements on ethanol based race fuels. I myself have 3 baps, one for each of my pumps. It’s a tried and true method when done properly and sometimes you just don’t have a choice if you want to avoid the trials, errors, and tribulations of trying something that hasn’t been proven out yet on our platform.

For example, I could potentially get rid of my triple pump triple bap setup with one of those cool high volume variable speed brushless fuel pumps but I haven’t because I know it would take a lot of time on r&d to figure out and work out the kinks. It would be like going down a rabbit hole and not everyone makes it out.

 

[fumanchu182]

My fuel pump DC is 45-47% on E85 at idle so I'd say that's fine. At WOT mine's around 80-82% in good air.

You're actually not dropping that much fuel pressure but you also don't have a lot of injector head room to cover for it. Even if it maintains 80+ psi, you'd probably run out of injector in negative DA as it stands.

With that said, I would add a single bap plugged into the slave fpdm. That'll fix your fuel pressure issue for the time being. You might have to add a 2nd one when the air gets cold if you stick to this configuration. You can also target higher fuel pressure during WOT operation but that'll just cause the fuel pressure to drop faster once pump flow is mechanically maxed out.

Your bypass valve is also on the verge of triggering a limp mode condition. This is typical whenever pushing over 21 psi of boost. As you mentioned, it is just an srt4 throttle body after all, not really designed for this use case. There are companies out there that sell modified bypass valves with a stronger motor. Either lower boost or upgrade your bypass if you want to avoid future frustrations. You could also take a chance that another bypass might be a little stronger but it could also be weaker. I don't recommend that route for you given where you're at with this car.

Your 1-2 2-3 short shift issue, that's weird. It's not skipping 2nd gear though, it can't physically do that, but it's triggering the 2-3 shift right after completing the 1-2. As to why, I couldn't tell ya. It's not something I've seen before which would be kind of odd don't you think?

I concur. A lot of your issues will go away if you turn it down as well.

People don’t typically invest in a full return style system at this power level, mainly due to cost, so I can’t really comment on DSR’s product offering. I don’t have enough data to draw meaningful conclusions about how much it would enhance a stock style setup. I do know that at higher power levels even on a full return style fuel system, using traditional Walbro pumps may require baps to meet fuel flow requirements on ethanol based race fuels. I myself have 3 baps, one for each of my pumps. It’s a tried and true method when done properly and sometimes you just don’t have a choice if you want to avoid the trials, errors, and tribulations of trying something that hasn’t been proven out yet on our platform.

For example, I could potentially get rid of my triple pump triple bap setup with one of those cool high volume variable speed brushless fuel pumps but I haven’t because I know it would take a lot of time on r&d to figure out and work out the kinks. It would be like going down a rabbit hole and not everyone makes it out.

All good information, at this point I will be going up in pulley size, I don't have the stomach for upgrading the fuel system and or adding a BAP. I had one when I started this journey but it kept dying in the middle of the runs due to over volting the stock pumps. Just a bad experience all around so hesitant to go back there. I didn't realize that trying to make more power than what I had on 93 would require this much more effort to get e85 to flow. There is something to be said that maybe I should change from the stock fuel rails to the FORE ones as they flow better but as it is I might be running out of pump, or do I go to a triple pump system and call it a day with some 1650 injectors (which I don't want to do). I'll never be 7s fast but I'd definitely be low 9s at that point but then again I have to worry about stress on the trans and all that good noise. I think a 2.85 would be good, bring me down in boost, give the fuel system a little bit more head room and just enjoy the car for what it is. If I can go 9.5 in the heat, then a lower number for sure will happen in the fall, just hope I don't run out of pump then. Thank you @Speedy! @zhc and @jonx96 for the help, it is truly appreciated.

 

[fumanchu182]

I also just noticed my fuel system from OST has the 285 pumps, can they be upgraded to the 525? So dual 525s might also increase pressure right?

 

[zhc]

I also just noticed my fuel system from OST has the 285 pumps, can they be upgraded to the 525? So dual 525s might also increase pressure right?

Yes they can be upgraded to get you a little more. It’s pretty easy to do.

 

[zhc]

a BAP. I had one when I started this journey but it kept dying in the middle of the runs due to over volting the stock pumps. Just a bad experience all around so hesitant to go back there.

Your fpdm was probably going into limp mode from seeing too high voltage. Generally you’d want to set the Bap to a lower voltage setting to avoid this. Most baps have this option but people often leave it max’d out not knowing. That’s partly why I suggested putting one on the slave fpdm which isn’t monitored. Good lesson to share so that others can avoid experiencing similar issues with over voltage.

 

[Speedy!]

@zhc what's the tell on the bypass being over run? I'm probably gonna be in the 20psi boat this fall with the 2.7 blower I'm having gone through. Is it the voltage differential between bypass position1 and 2?

I always thought the JMS booster would be a good addition for the second pump if ever needed.

Also, I've heard of some tuners turning DOWN fuel pressure to increase fuel flow. One I know of actually sets the Redeye fuel pressure to 80psi like a standard Hellcat instead of the factory 100psi. Thoughts?

 

[zhc]

@zhc what's the tell on the bypass being over run? I'm probably gonna be in the 20psi boat this fall with the 2.7 blower I'm having gone through. Is it the voltage differential between bypass position1 and 2?

bypass position 1 and 2 are just inverses of each other, they're two different sensors. The PCM checks both. As for being overrun, just make note of your bypass position during WOT operation to see if it budges as you turn up the boost. It shouldn't deviate more than a few hund. Anymore and it's being pushed open somewhat. That isn't a big deal honestly. I ran some of my best times with a bypass that was on the verge of triggering a limp mode condition with voltages deviating more than a couple tenths from what the computer wants to see. One of those set conditions is a deviation of .29 volts for more than 1 second from desired. There's many more set conditions though, that's not the only one but a common one I see that gets triggered. These things operate on duty cycle so whenever there's deviation, it adds voltage until it matches desired or in cases where it can't, it'll just max out the duty cycle to the bypass until it triggers a limp mode condition usually because it gets weaker over time when subjected to this kind of abuse repeatedly. Such problems tend to be intermittent which creates difficulty in proper diagnosis if you don't know what to look for.

Also, I've heard of some tuners turning DOWN fuel pressure to increase fuel flow. One I know of actually sets the Redeye fuel pressure to 80psi like a standard Hellcat instead of the factory 100psi. Thoughts?

Fuel pumps flow more fuel at lower pressures, yes. But inversely, injectors aren't able to flow as much fuel at lower operating pressure as well. So you have to balance the two against each other when making decisions like that. If you have big injectors, you can drop operating pressure at WOT to get more out of your fuel pumps before having to upgrade. If you have a pump setup that can maintain a high pressure under WOT conditions for a particular setup, then you can get away with a smaller injector.

 

[fumanchu182]

@zhc some good information here. I already ordered some bypass valves and this one came in today.


You mentioned people make stronger motor versions, do you have a vendor in mind? I did searches and can’t find anyone.

Also how much headroom do you think upgrading to the 525s? Ive just had bad experiences with a bap and really dont want to revisit them.

 

[hellkeezy]

@zhc some good information here. I already ordered some bypass valves and this one came in today.
View attachment 75724

You mentioned people make stronger motor versions, do you have a vendor in mind? I did searches and can’t find anyone.

Also how much headroom do you think upgrading to the 525s? Ive just had bad experiences with a bap and really dont want to revisit them.

Gearhead Fabrications sells one called Badass Bypass valve.
https://www.gearheadfabrications.com/product-page/ghf-badass-bypass-valve

 

[zhc]

You mentioned people make stronger motor versions, do you have a vendor in mind? I did searches and can’t find anyone.

You can order off of Gearhead Fabrication's website or give Baily's Hyperformance a call and get one done through them. You'll probably have to send one in as a core as cores are hard to come by now days. The stronger motors used for them have also been in short supply so expect a long wait time potentially for one to get returned to you they're on back order.

Also how much headroom do you think upgrading to the 525s?

I honestly couldn't say in your case. It's not often that someone with a dual non-return factory style fuel system will upgrade their pumps and for those that do, they're not folks I'm tuning because I would have made a different recommendation. That means I have no comparative data to draw upon.

However, if you go by what's advertised on paper. Say 485 pumps and upgrade to 525 pumps, then that would be just over an 8% increase. If you take their advertised flow rates at 40 psi, that increase drops to just over 6%. That's not much in the grand scheme of things.

 

[Speedy!]

I did the math on the 285 vs 295 pumps earlier today and concluded little difference.

 

[fumanchu182]

You can order off of Gearhead Fabrication's website or give Baily's Hyperformance a call and get one done through them. You'll probably have to send one in as a core as cores are hard to come by now days. The stronger motors used for them have also been in short supply so expect a long wait time potentially for one to get returned to you they're on back order.


I honestly couldn't say in your case. It's not often that someone with a dual non-return factory style fuel system will upgrade their pumps and for those that do, they're not folks I'm tuning because I would have made a different recommendation. That means I have no comparative data to draw upon.

However, if you go by what's advertised on paper. Say 485 pumps and upgrade to 525 pumps, then that would be just over an 8% increase. If you take their advertised flow rates at 40 psi, that increase drops to just over 6%. That's not much in the grand scheme of things.

I did the math on the 285 vs 295 pumps earlier today and concluded little difference.

Well good news, I'm done racing for the season... bad news... I'm out of fuel pump based on some feedback in this thread. The injectors spike as the pump reaches max duty cycle then the inejctors spike and as a result fuel pressure drops. The only thing I could do is put a BAP on the non monitored FPWM but I've not had a great experience with those. I could also upgrade to a triple pump setup but I don't know if that is even possible on our returnless systems. Another birdy in my ear mentioned changing to a return style system could solve a lot of this. Thoughts?

I know @jonx96 runs duals with a bap I believe, but I am hesitant to go that route again. Having a car almost blow up cause of them will do that to you. I'm just angry at myself, if I knew all this was going to happen I would have stayed on a 2.72 hellraiser and just sold the car then.

For all those that ever read this post. Leave your car stock, you'll be a lot happier in the end. If you want a racecar build a racecar. Also tidbit, the 285 is actually a 470lph pump and the 295 is the true 525... bullshit ass marketing wank.

 

[vortecd]

From Tapped website. I went with the 1.5 kit being it was only $100 more

Tired of searching through forums and pages trying to find everything you need for your fuel system? This kit is identical to our Stage 1 but this complete setup uses a Fore double pump hat with 295 pumps installed. Although the 285 (Factory Hellcat Pump) is a known powerhouse rated at 525lph, that is free-flow, at 40psi they are around 470lph, the 295 pump is also a 525lph pump but pumps out 525lph at 40psi!