you could very well be right, if the leaning out is caused by the injectors firing, but if the problem is pressure falling off in the rail, thats not controlled by the megasquirt. well, other than it turning the pump relay on.

 

Im not versed really on the MS. He built that back in 09.


http://mentalsocket.com/Iroc87/megasquirt1.html


Given its given issues before.........

 

yea, thats the same kit i built for my gta. but i never ran any boost with it, just n/a.


maybe an option? could possibly swap my ecu in place and put his tune in there to try out.....

 

That would be a way to do it for sure. If nothing else rule out hardware failure of the MS.

Only real way to know whats happening is to relate the mechanical gauge reading to what the datalog says? If they don't match up.....

EDIT: Also curious as to what version he is running?

http://msextra.com/doc/ms3/firmware.html

1.2.x has some boost related settings changed.


Wonder what would happen if he commanded more fuel up top despite what it says it is doing? Similar to the timing issue.....

 

That's called failing to read directions. You need to TELL the MS what your initial advance is (also called a bias on stock calibrations). It doesn't have ESP. Same thing applies to any ECM.

Absolutely nothing electronic can cause a drop in fuel pressure without an alarming indication. (i.e, fuel pump losing power would shut down the vehicle, injectors going static would run stupid rich but not enough to drop fuel pressure).

He has a mechanical fuel flow problem.

-- Joe

 

As I mentioned Im not fully versed and open to learn here. Fuel cut can IIRC.
I just don't understand how it could be mechanical when everything has been replaced? Unless the rail isn't keeping up? That may not have been changed.....

 

still running the stock rail and return line, if im not mistaken. it is possible a restrictive return line could artificially raise the fuel pressure at idle as i said above. at wot, when less fuel is running through the return, the pressure could drop down to what it SHOULD be without the restrictive return line.

 

gone

 

Ive come in later on this than the 8 pages previous. Im not attempting to diagnose the problem, more just give you ideas that might make you go....hmm? Ive seen the videos over the years, and its obvious your skilled (that's not *** kissing, that's a fact). I would do two things, which wouldn't cost much if anything.

1. Check the pump....can it flow as advertised? Is to faulty....worn out....damaged? Any way to test it out to max capacity?

2. Pull the MS unit......is it okay, any damaged components?


Still a fan, hope you work it out

 

It's always that one thing that's looking you right in the face, but we always fail to see it. Let a fresh set of eyes check it out.

 

8.) Q: How much HP will the 340 Stealth Pump support?

A: Ordinarily, Aeromotive will publish a HP rating for fuel pumps, and we could do so for the 340 Stealth pump in the same fashion. However, the 340 Stealth Pump is typically installed in an otherwise stock, return-style EFI fuel system. For this reason various OEM components within the fuel system (engineered for a pump with only 1/3-1/2 the flow capacity of the 340 Stealth), could have a negative impact on the flow that can be delivered to the fuel rail, regardless of the new pump’s increased flow potential. This makes it difficult to project a standardized HP limit for the 340 Stealth Pump that would be correct across the many applications in which the pumps may be used. Bottom line, fuel system combinations and variations from one vehicle to the next, across the wide range of year/make/models listed in the application guide, are just too numerous to properly calculate maximum HP for each.

One thing you can be certain of, the 340 Stealth Pump you receive has been thoroughly flow tested and verified to meet all specs across the full range of pressure, and to be at or below the spec current draw. All 340 Stealth Pumps are tested multiple times in production to ensure each individual pump does flow 340 lph and meets all quality and performance specs, 100%.



Interesting that they don't provide hp ratings.......wonder if you could run a inline pump just to test out whether the pump is weak?


Also to double check myself here........is the wiring all new for the pump......like upgraded or stock? I thought it was upgraded?

 

I have always been on the fence about MS. That is why I asked that question about it earlier. I just started my build today and will I continue to use my stock OEM 730 ECU with EBL to control boost from Rob @ DynamicEFI. For the old school guy in me, it can't get any better than that. But of course I've been tuning over 15 yrs and have learned quite bit from members like TRAXION, ROB, and Gumpy R.I.P who passed away years ago to name a few because I know I forgot a lot more. Just hang in there man, I know it sucks because it's killing me too knowing how much time and money has been spent trying to reach a goal.

 

3 minutes in..........you heat shrinked the wiring? You mentioned you double heat shrinked it "in case it broke down" on the positive?

Was this heat shrink approved for submersion in fuel? If it broke down and the wire did touch would that cause a voltage drop or spike.....like blowing a 40 amp fuse as you mentioned earlier? Raychem DR-25 and Deray V25 are two good ones.....

I suggest that because it may be under hard acceleration that the wire shorts out when it comes into contact with the hanger......

 

What don't you like about it? I've used both and it runs circles around the other stuff.

-- Joe

 

I just remembered we made 550whp with a 255 pump, stock lines, and stock rails on an lt1. Yea, I think at this point I would let some fresh eyes look at it.

 

Regarding the fuel pump wiring.. It's been a long while since I did it but I know that I secured the wire in a way that didn't rely on heatshrink alone to keep me from blowing myself up. It's coming out soon (not by me) so we shall see.

Aeromotive does go on to explain further down on that page that it could support 700 hp on a boosted application:

So, putting aside all the variables, let’s presume the best case scenario: What maximum HP could a 340 Stealth pump support if the system were fully optimized?
Okay, in a bypass EFI fuel system that has been optimized to include:

• a 72 lb/hr injector (presuming V-8 engines, 150 lb/hr for 4 cylinder engines)
• 40 PSI base fuel pressure, vacuum line disconnected
• Boost is limited to 20 PSI (allowing a 1:1 boost reference to 60 PSI max under load)
• Providing the system has the necessary electrical supply to properly power the pump
• An appropriate fuel line size equivalent to AN-06 is installed
• A high-flow filter such as Aeromotive 12301 is installed
• A decent, high flow fuel rail is employed to feed the injectors
• A high flow regulator such as P/N 13109 and a AN-06 return line is present

It would be reasonable to rate the 340 Stealth to 700 flywheel HP EFI forced induction, 900 flywheel HP EFI naturally aspirated, on gasoline fuel. In this example the injector duty cycle for either V-8 or 4-Cyl would be between 80-85%.

 

i just thought of something , prolly would have helped out before u installed the new fuel lines but it can still help out now

since u have a presure gauge on the rail u know fuel presure is droping
why not install a y or tee right were the feedline comes out of the tank and monitor presure there as well

if u do 1 of 2 things will occur

#1 fuel presure drop will match that of the rail
if this is the case then u know the pump is falling off, then u just need to knwo if its the pump itself or a wiring issue

#2 fuel presure at the rail drops , but fuel presure at the tank stays the same
now u know the restriction is in the rail itself , or maybe one of the rail crossover tubes


instead of back at the tank u could monitor fp right before the fuel rails , but i would start back at the tank

this is how i would go about diagnosing the issue , as it will take any ifs out of the equation

 

whats the most anyone has made using the stock tpi rails?
back in the 90's my car was at the 450-500whp mark with twins and a tpi intake. tank was sumped, #8 feed line, return was using the stock feed line. i do not recall the guy having any problems with going lean with that setup, but i have to wonder how much headroom there was?

 

marty was making over 800 but he had to drill out the crossovers not sure what else he did to the rails

 

100% of the engines fuel was coming from the rails? (no wet nitrous system)

 

he had a 50-100 shot on the car not sure if it was a wet or dry system though

 

Roger that, Im at work.....didn't read that far down. Went back and saw that. Like I said, just ideas and thoughts...

Is it the stock fuel rail? Ive read they are fine to around 500 hp? Would make sense.....you have stock rails and made 4XX something last time - then you freed up a lot of power with the headers and other tweaks - maybe its your rails leaning out.

 

Now that you said crossovers the schrader is in the passenger side isnt it? Wow, never thought of that. Did marty dual feed his rails ultimately? If it puked a hg will be curious to see if it is the passenger one. It still does not explain the thermal aspect though.

 

do they still make these?

http://www.google.com/url?sa=t&rct=j...di75QCSfrLZiIw

if you scroll down to the bottom you will see a 5/16" return (stock tpi line?) is good for 45 gal/hr. the aeromotive 340 is pumping around 90 gal/hr, no?

 

from the aeromotive website-

 

Just remembered the Lt1
car was also running a meth kit which may have covered up any fueling issues. I believe a 255 pump and stock lines would have been completely maxed on their own.

 

im about 80% confident this was the problem all along. the rail/regulator/return needed to be upgraded to accommodate the pump.

going lean can take out an mls gasket, too. may have damaged the head in doing so.
take a break from the car and have your buddy do the rest of the fuel system and check out the engine. he can pressurize each cylinder to see which one is putting air into the coolant system. once its found, pull that head and check gasket. if its just the gasket, bolt the head back down using a standard throw away gasket so he can do a leakdown test to check the rings. if they are ok, pull the head and put another cometic on. if it got the head, a new set of heads would be nice. or repair/resurface your head....


this is fixable.

 

gone

 

i would agree on the rails being ok if thats how they are setup. they should flow plenty. the return is still undersized though, going by what i've been reading.
the test with the vacuum on the regulator might be a good one to do. would be interesting to see the results of that one. the return side of the system is the only questionable piece to the puzzle, regulator AND return line. and the line needs to be much larger anyways, from what aeromotive says.
thermal issue- i have no idea honestly. i know of 2 cases personally that had a thermal issue that would stall the car after running for a period of time.
1. '03 cobra with sumped tank and a1000 pump. after driving around town for 30 minutes or so and parking, the car would not restart. had to let it sit 30mins or so before it would run again. seemed to only be an issue around town or in traffic, as the problem wouldnt show its head on long road trips. never really figured out the problem on that one i dont think.
2. lt1 car with s-trim vortech and 255 pump and stock lines. after driving for a few minutes romping on it the car would choke itself down and die. fuel was actually boiling in the tank and whistling out the gas cap if you loosened it up. he told me it was the pump and he had it changed resolving the problem.

 

im willing to bet on the return line/regulator then , when i first installed a single 340 in my car i could not get base fp below 55ish psi , with both pumps on the car wouldnt even run as it would spike my fp gauge to 100 psi
have u ever ran it with the 255 walboro? or did u just go right to the 340 pump

the heat thing totally has me stumped though

 

gone

 

are you running a restrictor on the turbo oil line? if so, you might want to try opening it up or removing it altogether...
also look into a larger fuel tank vent setup, and make sure you are running at least a half tank or more of fuel.
anxiously awaiting test results.

 

gone

 

gone

 

Looks like a Turbonetics T7675 would work well for you. Check them out! My T7875 should be here Tuesday http://shop.huronspeedproducts.com/T...urbo-t7875.htm and then my project begins. Good luck my friend!

 

If your worried about turbo size, the t-netics TC series is the way to go. the T7875 and T7875 are tc series with larger exhaust housings IIRC.

I will sell you mine [tc-76] for a good price if you want, I have been thinking of upgrading and if it'll help you out and make an easy sale for me why not. It's got a couple dings, only 2000 miles on it or so, works great.

 

if it fails the minimum fp test do this

turn the regulator up till fp rises set it 2 psi above the lowest setting ( rember to do this with the vacum line cnonnected and engine idling ), then go into megatune/tuner studio and scale down the entire ve table to compensate

just be aware the high load portion of the map will prolly still be off , if u were trying to add fuel before to compensate for going lean

 

You are halfway correct, the T series turbos have a larger compressor housing as well that's why it's not a TC. The new T series T7875 is on the left and TC series Hurricane is on the right,

 

gone

 

Might be interested in a turbo.. depends how things go in the next week or two with this thing.

 

Is it possible that the fuel flow restriction is causing the pump to heat up, degrading its performance? You said it starts pulling a lot more voltage when these things happen, but Im not sure if that means its a safe assumption that it's drawing proportionally more amps. Been a little while since my circuits course... But if it's drawing more amps and getting hotter because it's working too hard that can either affect its performance or perhaps even heatsoak the fuel itself.

You'd have to see if the fuel coming out of the line is 160F+, but I KNOW gas will boil at that temperature because my car does that when it sits after running. But the difference is my fuel will boil when the line isnt pressurized. Yours IS pressurized... but then I wonder how low the pressure is dropping... Probably not enough to allow the fuel to boil in the line... but maybe? I would imagine you would SEE crazy pressure fluctuations as gaseous gas went through the gauge so I'd hope we can at least rule that out.

This is well out of my realm of expertise... just tossing some ideas out.

 

https://www.thirdgen.org/forums/tpi/...el-system.html

some ideas in there.

I agree with you that heat soak should not cause a rail/regulator issue, if there is a problem like that it should do it cold too. If the fuel isn't boiling, fuel pressure drop has to be a pump issue, nothing in the system will expand significantly at the temperatures it will see [except the injectors maybe? doubtful]

It's a pump, wiring, or ECU issue. I'm still thinking you have a table that is only "active" certain conditions like a bad sensor or something that gets screwy with heat, temp sensor failing high, TPS sensor, MAP, something...

I had an issue where my AFR's would just act stupid, and i could not figure it out! It ended up being a bad MAP sensor, i watched it in the data logs at idle for 25minutes or so, until I recognized a pattern. It was randomly going static, at whatever it's last reading was, then working normally for a while. It would go static for .5 to 3 seconds, some times just once, sometimes it would act like a step function for 12 or 15 seconds, and sometimes it would go static until the input [manifold pressure] changed a bunch, like a shift or the boost changed 5+ psi. You could have something similar going on, it reads wrong when it gets hot... Just throwing anything I can think of out there..

 

im kinda lost on the factory fpr....
the ideal setup is a boost referenced regulator with manifold vacuum on its port. static with vacuum line unhooked you would read 43.5psi (or whatever you want it to be), with line hooked up at idle you would read less than that, and with 10 psi boost you would read 53.5psi. right?
fuel tables in the ecu would be setup for boost referenced fpr.
so, when applying 10psi to the factory regulator, what do you see? (or maybe i am misunderstanding what you meant up above?)

fuel return line is still sized for a pump half the size of the 340, and im not sure what the regulator itself might flow.

fuel heating in the rails may compound the situation since hot fuel would need more "room" than cold fuel. fuel system might barely get by when cool, but not when its warm.

 

im just as lost as the op now , everything seems ok but that is out the window once it heats up
i cant for the life of me think of one reason why it would lose fuel presure when it heats up , unl;ess the fuel is actually boiling


the only thing i can think of besides the regulator and return line upgrade is to monitor both fuel rail presure and feed line presure before the fuel rail , go beat on it till the issue comes back and compare the 2 readings.Atleast this could localize the issue to the fuel rails or the tank

my only other thought is that the injectors are getting hot and are shutting down and or hanging open , hanging open while making the engine dead rich , would read lean on a wideband 02
this could also be the source of a fuel presure drop , unfortunaly this would only be able to be determined by putting the injectors on a flow bench and running them at high duty cycle till they get hot, and see how they react


isnt southbay fuel injectors located near the op? if so maybe they could test those injectors for u

edit nm they are in ny not fl



do u have any datalogs of the issue , if so can u post one id like to take a look at it

 

I don't see the reasoning behind why we think a return line issue is causing his problem. The pump is rated for operating pressures far higher than what he's seeing, and as such any restriction on the return side wouldn't "overheat the pump". The pump doesn't know that their is a restriction vs a higher pressure setting at the regulator. He's running the pump within it's operating limits.

The theory of overheating (explaining the voltage utilization), and pressure drop all points to a suction problem.

-- Joe

 

the problem was a loss of pressure at wot.

my original thought was the return side being too small was causing an artificially high pressure at idle. so, at wot when there wasnt very much fuel flowing through the return, the regulator would then settle down to what it couldnt attain at idle. (thus, pressure would drop at wot)

aeromotive says the return is far too small. so, i would change it.
if there is a suction problem, what do you think it could be? op has gone through this with a couple different pumps now, and each time they have a clean strainer on the pump along with a clean tank. the tank could have an insufficient vent, and i mentioned that awhile back.

 

Well from what I have read, a large enough restriction in the fuel system....return line could cause the pump to work too hard....causing heat and can foam the fuel.

From Magnafuel FAQ page....

Is it necessary to plumb your system for a return line to the fuel tank?
Yes, because all MagnaFuel pumps are equipped with external bypass system. We don't think that any well-engineered racing fuel system should use internal bypasses because all they do is heat up and add foam (bubbles) to the fuel. It is a little more difficult to plumb, but it provides a better and more efficient system. See the drawings in the Kits section for proper placement of the return line in the tank.




Obviously its just a blurb, but could be relate?

 

Ok. So what you suspect is happening is the return is acting like a restriction when at idle, and fuel volume is highest, so the regulator is cranked way down so when the restriction goes away, the regulator kicks in with a lower regulated pressure.

However, didn't he crank the regulator way down and show that he could regulate pressure way lower than 43psi ?

I also mentioned the vent. The problem is happening when fuel consumption is highest, and return volume lowest. Seems like a vent problem to me.

-- Joe

 

Wouldn't a cheap - quick way to check the vent would be to run without a gascap and see what happens? Willing to learn here so teach me!

 

Yep.

-- Joe