Lean Spot At ~2400 RPM...What the?
09-14-2010, 07:52 PM
#141
I probably shouldn't tell you that I have a CAD model and drawing of that bracket....
I have seen that Merrin damper. If I ever go with aftermarket fuel rails I will probably install one of those on each rail.
Last edited by mx594; 09-14-2010 at 07:54 PM.
09-15-2010, 03:48 PM
#143
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I've also got a weird knocking sound after fitting my CJM stage 3. It sounds like a series of taps (say 2-4) when you touch the accellerator from idle. I originally thought it was from the reg on the firewall but after temporarily unbolting it and zip tying it out the way found that not to be the case. Furthur inspection leads me to believe its from around the rails themselves. I've sort of got used to it but it is annoying. I'm going to remove the plenum and check it out when I have time to start my wire tuck but until then can't be assed 
When Charles makes up the adaptors I'll get one just for peice of mind and with a hope it may resolve my strange noise.
I like the reg bracket mx594. Might have to get one made locally. Might reduce the fuel flow noise a little.
Matt
When Charles makes up the adaptors I'll get one just for peice of mind and with a hope it may resolve my strange noise.
I like the reg bracket mx594. Might have to get one made locally. Might reduce the fuel flow noise a little.
Matt
HOLY CRAP!!! i have this too and i was so scared it was something bad. I have checked and double checked all my pipings on my turbo kit and i swore it was a pipe but there's no way.
So if you are sitting idling and just quickly tap the pedal does it have liek a metal metal tap? and if you just keep tapping the throttle fast at idle it keeps doing it? Mine is doing that, i assumed it was the motor twisting and a pipe hitting but you could be onto something because it happened when i put my stage 3 on also. maybe the rails hitting the plenum?
and mx, charles is making a dampner fit on the stage 3 kits.
09-15-2010, 04:24 PM
#144
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Yep thats exactly the noise! Dunno what it is yet. If I find out I'll let you know binder. My initial thought were that the rails might be a little loose and need tightening but if you grab each end and try to move them they don't budge even a fraction. I have to take my plenum off anyway soon so hopefully it will become obvious then.
09-15-2010, 06:56 PM
#146
Check the spacing between the plenum and the AN fittings on the right side of the regulator... mine are pretty dang close. If they were to ever touch I'm sure you'd hear it through the firewall.
Other than that I would suspect knocking...listen with a knock device to be sure that isn't the case.
Other than that I would suspect knocking...listen with a knock device to be sure that isn't the case.
09-15-2010, 07:03 PM
#147
HOLY CRAP!!! i have this too and i was so scared it was something bad. I have checked and double checked all my pipings on my turbo kit and i swore it was a pipe but there's no way.
So if you are sitting idling and just quickly tap the pedal does it have liek a metal metal tap? and if you just keep tapping the throttle fast at idle it keeps doing it? Mine is doing that, i assumed it was the motor twisting and a pipe hitting but you could be onto something because it happened when i put my stage 3 on also. maybe the rails hitting the plenum?
and mx, charles is making a dampner fit on the stage 3 kits.
So if you are sitting idling and just quickly tap the pedal does it have liek a metal metal tap? and if you just keep tapping the throttle fast at idle it keeps doing it? Mine is doing that, i assumed it was the motor twisting and a pipe hitting but you could be onto something because it happened when i put my stage 3 on also. maybe the rails hitting the plenum?
and mx, charles is making a dampner fit on the stage 3 kits.
09-15-2010, 07:23 PM
#148
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Check the spacing between the plenum and the AN fittings on the right side of the regulator... mine are pretty dang close. If they were to ever touch I'm sure you'd hear it through the firewall.
Other than that I would suspect knocking...listen with a knock device to be sure that isn't the case.
Other than that I would suspect knocking...listen with a knock device to be sure that isn't the case.
i have an os giken twin disk. It's all bolted together. 8 hours of dyno pulls at injected would have definitely destroyed it if the flywheel was loose. Flywheel hasn't been touched since last november and this only started after i put turbo and stage 3 fuel on it. Did it instantly on first start up from those upgrades so it has to be 1 or the other.
09-15-2010, 09:24 PM
#151
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I've also got the OS Giken twin plate and flywheel. Had it on for the engine brake in period with the stock APS fuel system and there was no noise. It only appeared after the stage 3 fuel system was installed.
09-16-2010, 07:09 AM
#152
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ya, it's not the clutch and flywheel. There's no way it would have lasted through the 500hp pulls i've been doing on it. Plus the fact that it didn't make a noise, a week later after swapping the new setup the noise was there immediately.
09-16-2010, 11:03 AM
#153
a clutch and flywheel wont make a knocking noise from things being loose... the noise comes from the transmission when you run a very light solid flywheel.
you can rule out the noise being related to the clutch and flywheel by trying to make the same noise with the clutch peddle down all the way. of course, it will be harder to hear since a twin disk clutch makes a new set of noises when the clutch is down... but the reduced acceleration of the input shaft with the clutch to the floor makes the transmission knock stop in my personal car and others i have worked on.
it could very well be the regulator... for as long as i have been building cars i have heard mixed reviews about regulators mounted to the firewall causing tapping sounds. never had it happen personally on any of my cars, but i have heard of it countless times.
personally, i dont plan to focus much on any regulator noises. i just want to see what i can figure out about the damper issue. its very overwhelming at the moment. we have sold several hundred systems and never ran into an issue... and of course there are also probably hundreds of AAM systems and custom systems... none of which retain the dampers. now just in the last 2 months it seems we have a handful of people that are noticing an issue that may be related to dampening or lack thereof.
for our stage 0 kits its really no big deal because we can add a damper mount to the stage 0 fitting with only a simple extra machine process that will only take us a matter of minutes per kit.
for all the kits using billet rails (our stage 1-3 and other manufacturer kits) its not quite that simple. and its just so odd that its even needed out of nowhere.
i am considering possibly trying to change the plumbing reverse to see what happens. perhaps if the feed lines came into the front of the rails, and the return lines came out of the back of the rails to the regulator... perhaps that much shorter path to the regulator would allow the regulator to perform a share of the dampening itself. But that still doesnt change how many kits we have had out there for years running the existing plumbing without issue.
i feel a great sense of urgency to help the handful of customers that are currently concerned that there is an issue with their RFS not having a damper, but its hard to determine exactly where to start, or what exactly the fix is.
We have a pump, hoses, rails, hoses, a regulator, and another hose. in the end, this is the same layout used in aftermarket fuel systems in so many different applications and vehicles and rarely with any dampers included. While I am sure any application out there could benefit from an added damper, it seems bizarre that we have run into a scenario where it could possibly be an absolute requirement... right out of the blue with an existing layout that has been problem free for 5 years.
at this point in time, mx's car is the only car proven to have required a damper. in the end, the damper didnt completely resolve the issue even while it was added in almost directly where it originally was. so now i am thinking that perhaps the new stage 0 fitting will be a fuel damper spacer, allow the damper to face the same direction and position in relation to the rail bore, and have the outlet come out the side. then we can put that in mx's car and see if that has a greater effect than his current custom fitting.
that, in reality, is as good and close to OEM as it can get. if there is still fuel pulsations at that point, surely they must be equal or less than stock.
a couple weeks ago i had some conversations with an engineer at aeromotive and i am going to follow up with him and get some ideas.
fortunately, our own 350z has the lean spot at ~2500 rpm also, giving us an in-house means to test solutions/effects/changes to the fuel system to see if we are chasing the same gremlem that MX was.
you can rule out the noise being related to the clutch and flywheel by trying to make the same noise with the clutch peddle down all the way. of course, it will be harder to hear since a twin disk clutch makes a new set of noises when the clutch is down... but the reduced acceleration of the input shaft with the clutch to the floor makes the transmission knock stop in my personal car and others i have worked on.
it could very well be the regulator... for as long as i have been building cars i have heard mixed reviews about regulators mounted to the firewall causing tapping sounds. never had it happen personally on any of my cars, but i have heard of it countless times.
personally, i dont plan to focus much on any regulator noises. i just want to see what i can figure out about the damper issue. its very overwhelming at the moment. we have sold several hundred systems and never ran into an issue... and of course there are also probably hundreds of AAM systems and custom systems... none of which retain the dampers. now just in the last 2 months it seems we have a handful of people that are noticing an issue that may be related to dampening or lack thereof.
for our stage 0 kits its really no big deal because we can add a damper mount to the stage 0 fitting with only a simple extra machine process that will only take us a matter of minutes per kit.
for all the kits using billet rails (our stage 1-3 and other manufacturer kits) its not quite that simple. and its just so odd that its even needed out of nowhere.
i am considering possibly trying to change the plumbing reverse to see what happens. perhaps if the feed lines came into the front of the rails, and the return lines came out of the back of the rails to the regulator... perhaps that much shorter path to the regulator would allow the regulator to perform a share of the dampening itself. But that still doesnt change how many kits we have had out there for years running the existing plumbing without issue.
i feel a great sense of urgency to help the handful of customers that are currently concerned that there is an issue with their RFS not having a damper, but its hard to determine exactly where to start, or what exactly the fix is.
We have a pump, hoses, rails, hoses, a regulator, and another hose. in the end, this is the same layout used in aftermarket fuel systems in so many different applications and vehicles and rarely with any dampers included. While I am sure any application out there could benefit from an added damper, it seems bizarre that we have run into a scenario where it could possibly be an absolute requirement... right out of the blue with an existing layout that has been problem free for 5 years.
at this point in time, mx's car is the only car proven to have required a damper. in the end, the damper didnt completely resolve the issue even while it was added in almost directly where it originally was. so now i am thinking that perhaps the new stage 0 fitting will be a fuel damper spacer, allow the damper to face the same direction and position in relation to the rail bore, and have the outlet come out the side. then we can put that in mx's car and see if that has a greater effect than his current custom fitting.
that, in reality, is as good and close to OEM as it can get. if there is still fuel pulsations at that point, surely they must be equal or less than stock.
a couple weeks ago i had some conversations with an engineer at aeromotive and i am going to follow up with him and get some ideas.
fortunately, our own 350z has the lean spot at ~2500 rpm also, giving us an in-house means to test solutions/effects/changes to the fuel system to see if we are chasing the same gremlem that MX was.
09-16-2010, 01:01 PM
#154
at this point in time, mx's car is the only car proven to have required a damper. in the end, the damper didnt completely resolve the issue even while it was added in almost directly where it originally was. so now i am thinking that perhaps the new stage 0 fitting will be a fuel damper spacer, allow the damper to face the same direction and position in relation to the rail bore, and have the outlet come out the side. then we can put that in mx's car and see if that has a greater effect than his current custom fitting.
Again, my custom adapter moved the apparent lean spots from 1200/1600/2400 rpm to 1500/2000/3000 rpm and they are nowhere even close to the severity that they were. I would say the lean spots I have now are only 10% the magnitude that they once were, and the only reason I even notice them is if I am cruising at just the right rpm I can feel just a hint of sputtering - it's almost undetectable. I will post datalog screenshots showing before and after the damper was added in.
The only other thing that may be contributing is the fact that the pressure is now being regulated after the rails, whereas with the OEM system it is regulated in the tank, waaay before the rails. So IF there were any pulsations from the fuel pump, they would not be damped by the regulator like they were before.
09-16-2010, 01:13 PM
#155
i dont believe the pump will cause any pulsations unless there is cavitation going on in the tank. either way, any pulsations that far back will have been averaged out before the engine bay... especially once hitting the primary damper on the intake manifold mounted bracket which the stage 0 kit retains.
i am very confident that we are only battling injector induced pulsations.
i am very confident that we are only battling injector induced pulsations.
09-16-2010, 02:43 PM
#156
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interesting stuff.
i've been testing everything i can to get my solution solved. Mine is more of a tip in but i do have 3 spots that are the same areas that charles has on his car that go lean but not extremely lean.
i've been testing everything i can to get my solution solved. Mine is more of a tip in but i do have 3 spots that are the same areas that charles has on his car that go lean but not extremely lean.
09-19-2010, 09:24 PM
#157
Take a look at this datalog project I created. Both graphs show a slow acceleration run in 4th gear from ~1200 rpm to ~3700 rpm with O2 control turned off. As you can see, in each run I was trying to mainatain -17.5 inHg which corresponds to the center of one of my load columns.
The top graph is from before I added the damper back in. The red trace is Air/Fuel ratio. Imagine how hard it would be to try to tune out those lean spots. The three lean spots appear at 1200, 1600 and 2400 RPM. The lean spot at 2400 rpm peaks at 17.6:1 AFR. My attempts to tune these spots out were a disaster.
Now look at the bottom graph. After adding the damper back in and literally about 10 minutes of rough street tuning, the red trace is what the A/F trace looks like now. Notice I still have some odd spikes, with the worst being at 3100 rpm. Still, this spike is only 15.7:1 A/F and is nothing compared to what I was fighting before.
The top graph is from before I added the damper back in. The red trace is Air/Fuel ratio. Imagine how hard it would be to try to tune out those lean spots. The three lean spots appear at 1200, 1600 and 2400 RPM. The lean spot at 2400 rpm peaks at 17.6:1 AFR. My attempts to tune these spots out were a disaster.
Now look at the bottom graph. After adding the damper back in and literally about 10 minutes of rough street tuning, the red trace is what the A/F trace looks like now. Notice I still have some odd spikes, with the worst being at 3100 rpm. Still, this spike is only 15.7:1 A/F and is nothing compared to what I was fighting before.
10-28-2010, 07:29 PM
#158
Just an update:
I redesigned the adapter to mount the damper concentric with the fuel rail like it was stock, so now the return line comes off the adapter at a 90 degree angle. I had someone at my work machine the adapter for me at my own expense.
I am hoping to get the adapter installed and tested sometime this weekend. The weather is turning sour fast here in MI so if I don't get it in there soon, it will have to wait until spring.
I redesigned the adapter to mount the damper concentric with the fuel rail like it was stock, so now the return line comes off the adapter at a 90 degree angle. I had someone at my work machine the adapter for me at my own expense.
I am hoping to get the adapter installed and tested sometime this weekend. The weather is turning sour fast here in MI so if I don't get it in there soon, it will have to wait until spring.
10-29-2010, 01:57 PM
#160
Hmmm... I get a lean rpm "row" at 1600 rpms but it's not bad - have it mostly tuned out - always thought it was torque converter / gear related thing. Nothing at 2400 though. CJM Stage 1 moving to Stage 2 sometime this winter. If you buy something str8dum1 that's an easy add on to the fuel rails, let me know... I'll have Forged put it on when I ask them to install a few other things this winter.
Last edited by rcdash; 10-29-2010 at 01:59 PM.