it only went down to 37-38psi... just barely below 43. and was that cool or warmed up? would it matter? i have no idea. i can run the LT1 car im working on down to single digits i believe. it has an a1000 pump.

vent needs to be at least a 3/8 or so i would think. he has been running the car with the cap cracked open i believe. is that enough? i have no idea.

 

He already says he leaves the gascap mostly open already. I mean it's still on the filler neck but he said, if I recall, 3 full turns "out".

Would a fuel pump suction issue only start after being heatsoaked? That's the confusing part to me.

 

ZZ3 - With the smaller turbo on the car at lower boost levels, can your reproduce the issue with fueling?
Here are my thoughts. Is it possible that you are floating the regulator spring by adding 7psi more head pressure when the injector fires? What I would do is leave your setup as is and add a good known working boost referenced regulator (as a test) between the existing regulator and the return line. This will rule out the regulator as an issue. Also, could there be a leak in the regulator housing that bleeds off pressure?
What is the max pressure that the regulator can hold before it starts dumping fuel to the tank(engine off, pump on)?
A way to stress the pump is to place a regulator on the feed line and dump it into a bucket, turn the pressure sky high and let the pump run. You should know in a minute if the pump can handle it as a pass down the track, then returning and making another pass should be about that time frame.
Not sure if you can, but you mentioned an ammeter on the pump. I am curious to see what the reading is when the issue is present..

 

I don't know about the whole heat soaked thing. This thread has been hard to follow, but what I'm understanding is pressure drop when in high boost. Is that only when the motor is hot? So he's seen the same RPM, in same gear, with same reported MAP and pressure has been ok vs all those the same with pressure drop and the only difference is a hot engine?

-- Joe

 

Yes, and he has verified the fuel pressure dropping off with a mechaincal gauge. The mechanical gauge data matches with what the AFRs are doing

 

I mentioned the pressure regulator as the culprit pages and pages ago, and I got tired of reiterating on it because I was told that a boost referenced regulator was used in the past as a test, as well as various fuel pumps, essentially ruling out those two. Bottom line is his fuel pressure regulator may not be functioning properly, and with the amount of time and money wasted he should have just put in a quality one and be done with it already rather than theorize about springs and vapor lock as well as other possibilities "surrounding" the regulator. Either that or his fuel pump is bad, the fuel lines are kinked, or the wiring with his battery relocation is not hooked up right causing a loss of voltage at higher demands. The only other area that I can think of is his Vapor Canister, or lack thereof. What was done with the line coming from the tank to the Vapor Canister? Did you just cap it off? If its just capped off, the tank still needs to bleed the vapor, especially if your not using a vented gas cap...

 

inline Filter ?

-- Joe

 

Saw it, read it(entire thread actually) just wanted to give my two cents.

I want an ammeter hooked up to rule out the pump and it will also further back if the regulator is gone. As I mentioned above, I am curious to see what the max pressure the regulator can hold without help from boost reference line. With the pump voltage boosted to 18V it is moving a lot of fuel. I just dont see it being the pump. As for the comment of the pump overheating due to a restriction in the return line, I have a buddy(and I am not saying this is a good idea, actually am against it) that has a Holley blue pump that is regulated down to 8psi fuel pressure without a return. It has been that way for 5 years, street driven. Plus! the fact that when in lower boost, the motor requires less fuel therefor more is being dumped to the tank via the regulator. Dont see the return line being an issue either. Now these are all assumptions that the issue is not present in lower boost, ZZ3 will need to confirm.

The evap can line being blocked/connected/open should not have anything to do with vac/pressure in the tank. It is not there to regulate that. I agree 100% a good vent is needed, but buildup of vapour in the tank will not hurt performance. If the pump is pulling that much fuel out and not properly vented, I would think you would/could hear a few tin oil can pops from the tank flexing....

 

Did you just say that the Vapor Canister does not relieve pressure build up in the tank? The Vapor Canister is a catch-can for fuel vapor, and it does in fact regulate the amount of pressure in the tank. If the canister is removed, the line can be left exposed, but if it's capped, the vapor needs to be released from the tank, thus using a vented gas cap. His pressure drops happens at high boost, and the higher the boost the higher the voltage to the pump, which creates an excess of vapor if it gets too hot. If the vapor is not vented, tell me how the fuel pump and/or injectors will be able to pulse a non liquid? It will lock...

 

These cars had a vent valve and an evap line to motor front. I dont think evap line is suppose to vent, it can alittle but the big valve ball vent thing these cars came stock with should be doing the main venting

 

I will disagree. These cars did not come from the factory running 20 pounds of boost, they came naturally aspirated with a TPI fuel pump. That valve was not designed to handle that much pressure buildup. Take away the canister, and now suddenly you have that much pressure buildup needing to be controlled by just one mechanical valve. I ran two of them with my old setup at one point, but now I just run a vented gas cap...

 

Correct me if I am wrong, but it is not a vent in the way the picture above is. The solenoid on the can opens and closes at different intervals to burn off excess vapour instead of venting it to atmosphere. That solenoid also has a vac line to the intake to pull the vapour out of the tank. Correct me if I am wrong again, there is a check valve in the line leading to the canister as well.

As I said, it being blocked off should not effect its performance, and I am pretty sure the TTA's did come with boost and used an evap can.

I figure with 80lbs/hr injectors(not sure what we are running here), and that pump, you should be able to run the tank dry in 10 minutes with injectors going static. A good vent is needed, the mechanical ones should be good. I know for a fact in my car that I have a pressure build up not a vacuum, but it is a different animal altogether. You are also talking about a buildup....If that were the case then I would think fuel pressure would be too high and not controllable as the only relief would be the injectors....I think it is either a vac effect on the tank and the pump cannot pull(very unlikely) or as you have said.....the regulator.

All of the things to date (in my eyes) are pointing to a regulator issue. As I said previous, the return line is not the issue as in lower boost it is fine. When more pump is given, it gradually gets better means that it is covering up the true issue, not that the pump is the cause.

ZZ3 - Out of curiosity, what happens when you leave the cap tight and take it for a spin? I still think that you are barking up the wrong tree in regards to a vacuum being created in the tank and its ability to pull fuel because of it....

 

There is no check valve in the line leading to the Vapor Canister, there is only one that essentially dangles behind the rear drivers tire. The picture above is my old setup, and I cut the lines and ran two of those check valves, one of them I got from a donor. Now I just run a vented gas cap because the volume in the neck is much greater than those two little fuel lines, and pressure buildup is a thing of the past. Yes, the solenoid is pulsed to allow the engine to "suck" the vapor from the tank, and much like a turbo charger, you will flow more when there is some form of pressure pushing or drawing as opposed to a single mechanical valve that only relives pressure when pressure is built, and pressure that is built in the tank that "forces" its' way out of a small check valve cannot keep up as fast as the Vapor Canister which is pulling the vapor out with engine suction, suction that increases with RPM no less, and not just waiting for it to come out on its' own like the check valve. Again, I threw that out there as a possibility because I don't know how Steve set his system up, and that is the only other thing that I can think of other than what I have been pointing out already; the regulator, the pump, or the alternator/battery wiring...

 

Thanks for the clarification, was not sure if the one by the can was also a check valve...Learning and trying to help, just like the next guy.

I suppose it is possible that if he does have the can plumbed up and working, would it not pressurize the tank under boost? I Would also think it would be the opposite effect that he is experiencing. A lot of if's and questions. I think we both want to see this thing put down the number Steve wants.

 

Most of us rarely see 20 pounds of boost, I mean you will get those who say they run that much, but they don't. Steve is pushing his turbo 350 very hard, upwards of 20-psi, and he is seeing the effects that it has with that much boost pressure using some of the stock TPI parts. I hang out with a lot Grand National guys, and they run upwards of 30-psi, some close to 50-psi with E85. They cannot stress enough the need and importance for a Vapor Canister, as all of them that I know run them for that very reason, to relieve tank pressure. It's really hard to diagnose Steve's problem online, I wish he lived closer. Although, he isn't that from from Cal Hartline, and I am positive that Cal will be able to figure it out if he gets his hands on it...

 

Just had to throw Gabby's vid up, E85 is a beautiful thing. Would you believe the stock cast crank held up to a number of 43-psi hits? I mean it broke, but hey, that's not bad for a stock 109 crank. The forged guys are running closer to 50-psi on E85...

 

Those are one way check valves combined with filters designed for incoming airflow to the tank, not out. When the charcoal canister purge is activated the tank needs fresh air coming in otherwise the tank would have no way to displace the pressure. So really all you did was create more pressure in the tank when you had it set up like that and the fuel vapor had no where go, but though a vented gas cap you installed. I personally have a small spectre valve cover filter used for import cars in place of the charcoal canister vent line from the tank.

The primary reason why GM put a Charcoal Canister purge on all vehicles had nothing to do with them being Boosted or NA. It is all about Emission Volatile Organic Compounds (VOC) from crank case vapor to fuel tank vapor. Charcoal Canister purge is part of the emissions system.

 

you lost me on the canister... why would a vent not work again? pump pulls fuel out of the tank, pushes it up to the rail. engine uses some fuel, and the rest gets pushed back to the tank. the amount of fuel used by the engine = space in the tank that needs to be filled in order to maintain zero pressure/vacuum.
or, as fuel is heated, pressure picks up in the tank?

i cant think of any more variables that can affect tank pressure/vacuum?

 

yes, basically the charcoal "filtered" the vapor from the tank instead of simply venting them if i remember correctly. there is engine vacuum connected to the canister, and on later model cars they used solenoid valves to intermittently pull vacuum on the canister. even my '78 cutlass had one.

 

... okay, so if you feel you are correct, remove your canister, plug your line, up the boost to a similar threshold, and lets see if your fuel tank doesn't collapse even with your single incoming check valve prevalent from both the vacuum in the tank and the atmospheric pressure on the outside, not to mention the tank perhaps even bursting on a very hot day. You wanna give it a go with some factual data to prove the theory?

 

You are stuck parroting an understanding from a naturally aspirated engine. The Vapor Canister does more than just filter and deliver vapor, without it and the line blocked off the tank will collapse. Your agreeing with the person you quoted, yet that same person you quoted is stating that the check valve in the back is not a vent, it is designed for incoming air only, not outgoing, so if it is not a vent, and you block off the Vapor Canister, how exactly does the tank vent without a vented gas cap at boost pressures a TPI system was never essentially designed for? I am all ears, lets hear it...

 

Oh and sorry to burst your bubble, they are designed for outgoing air, despite me using your theory in my response to Diggler. I am looking at it right now, and it is spring tensioned on the tank side, using a small screw you can "push" it open from the tank side, but then immediately seals and closes from the tension, so yes, it is an outgoing vent, not incoming...

Edit: I could put a little video together and apply pressure from both sides to one of the check valves in the picture I posted if anybody is interested in seeing how it works...

 

street lethal, are you saying the boost from the turbo is entering the gas tank? im still lost on what you mean when you are talking about having to use a charcoal canister to keep from damaging the tank on a turbo car?

how will you vent the tank without a charcoal canister? just add a vent, like all the hundreds of fuel cells the turbo powered race cars are using. could even be a hole drilled in the top of the tank if you werent worried about spilling gas everywhere, evaporating rapidly, or venting exessive vapor..... lol

i can tell you i ran a stock tank in my car with an a1000 and no charcoal canister. it wasnt boosted, though.

 

Dig, the bottom line is this, what Steve needs to do to END this nonsense is apply 20-psi of boost pressure to the top of the fuel pressure regulator, which technically should net him 63 to 65-psi in fuel pressure, then run the return line in a bucket and see how much fuel he is actually getting in a minute's time. If he's not getting enough fuel its the pump or the lines, if he is getting enough fuel then he has other issues...

As for the vapor canister, no turbo guy running upwards of 20-psi will cap the canister line without a vented cap, or some type of adequate vent period, because the slightest shake of the gas tank will cause the fuel in the tank to expand. The vapor canister normally triggers only during in decel in turbo applications, so a vent is needed to bleed during everyday driving as a just in case, which is what that check valve is there for back there. I do not know what Steve did with his canister setup, and that is why I threw that out there as a possibility of it causing issues at high boost because his canister is obviously gone, and we have no idea of what he did with the line...

 

he's already spent a few weekends trying to narrow down this problem. testing never hurts, but when half the system is questionable its a good time to upgrade some stuff and make sure the whole system is where it needs to be. he's been heartbroken a dozen times now over this thing, each time there is one component possibly at fault. when replacing that component doesnt help anything, he gets kicked in the rear again and he's sick of the car.
i am certain if everything in the system is the way aeromotive says it should be, he will have no more issues.

do the rails like this, add a 3/8" return back to the tank, and add some sort of vent. could use this rollover vent/valve on top of the tank if there is room, or 100 other possibilities as long as the tank can breathe.

 

Okay, I see where this is going. Somehow you have misunderstood what I said and also took it the wrong way. I was just stating what the component is used for, not get in to a debate on the zz3Astro's thread.

Cool, no harm done. Go ahead and test the valve you have. I know you have an air compressor, regulate the air as low as you can not to exceed 10 lbs or so. Take a rubber tipped blow nozzle and apply air in the direction away from the tank like you said not prying it open. I've done this along time ago and curried my fuel tank issues with pressure.

zz3Astro,

Sorry for chewing up your thread bro. It will not happen again.

 

Tried helping Steve as much as I can, even started a thread on the Buick forums for him years ago and sent him the link, but he doesn't want to listen to those guys. A very respected member over there who I am good friends with read this whole thread after I sent him the link tonight, and he immediately pointed out the pump Steve is using as being absolute garbage, and that they fail constantly in the Buick world regardless what the manufacturer claims. He feels that Steve built a fuel system based on a constant 14.7 - 15.0 voltage need, not realizing that voltage drops as fuel pressure demand increases at that level. He even pulled out a log of a nine second run, was showing 14.0 voltage at the tree, and 12.6 voltage at the 1/8th mile, difference being his injectors and pump will compensate for the voltage loss, and Steve's won't. Every single one of them say the same thing, and I agree, without him knowing his volume, he is shooting his arrows in the dark, and that is why he is heartbroken in my opinion. Meh, but take a look where this thread inevitably goes though. You got members wanting to argue about the characteristics of the vapor canister, you got theorizing left and right, you got pages and pages of possibilities, but you still have the same result. His fuel system and voltage is flawed, there is really nothing else to argue about. Every damn turbo forum says the same thing when Steve's problem is presented to them for the sake of conversation, but somehow this forum wants to blame bad tuning, and other silly things lol...

 

gone

 

So, I have a couple of dumb questions playing the "too small return" angle.

1)what's your vacuum at idle currently?
2)What's your FP at idle?
3)What's your base FP with the vacuum line off?

I realize all of this has probably been covered, but since the combo has been tweaked repeatedly so I want to have the readings all in one place. If you're not bumping up excessively you should have something like this happening:

-(idle vacuum (KPA)-101.325)/101.325*14-7=FP_DROP_PSI

Theoretically your base FP with the line off should drop down that much. As an example 43 PSI base pulling down to 35 KPA (my Peanut cammed 4.3L in the Astro did, your milage may vary) would be:

-(35-101.325)/101.325*14.7=9.622 PSI.

That means if I had 43 PSI base, I should have around 33.5 PSI of FP at idle. Anything more is because there's a restriction somewhere in the return circuit.

If this appears suspect, JMO take a line off the schrader valve, run it into a gas can and see if the base FP with the line off drops at all. Quick and dirty way to test it.

ED:I am totally NOT saying it's the return line. However this would be a logical way to check if it is, and a logical way to test it out as well.

 

i doubt u saw my post since this thread grew atleast a page since i last posted

but have u ever had the injectors checked out , or had different injectors in the car
. i know many pages back i was telling u about some issues i was having with my turbo tpi and the injectors over heating . i think u only went just as far as checking injector temps with an infared temp gun. and iirc u were getting really close to the temps on the injectors to were i was having issues with mine


i know its a shot in the dark but it seems like the only one thing u really havent put any much thought or time into checking out

if an injector or 2 were to hang open fuel presure would drop in the rail , and u would also see a false lean condition on the wideband

it sort oif makes sence that after u have driven for a while or done a few wide open passes when injector dc is high that the problem ocurs if infact the injectors are over heating

 

With no vacuum it's at 45. With 20" of vacuum it drops to 37-38.
Steve, do the things you have planned for the fuel system, but please add a larger return. I would at least do a -6. After that th only problem could be the rails. Watching your YouTube vid, the tee on the feed lines is extremely noisy. Wonder if that could be doing something crazy?

 

Maybe.... but if one was hanging open I would expect a misfire/bad running.
I know a 100 shot of nitrous with the bottle turned off will bog horribly and smoke like a fright train. Been there done that. Lol

 

Agreed, I don't think overheating injectors are the culprit... although, Steve did have issues with these injectors using Code 59 if I remember correctly, and nobody could figure out why it was surging, which is when he jumped ship to Megasquirt. Perhaps throw in another set of injectors to rule that possibility out. I think everyone here who is pointing towards the fuel system is dead on, as either the pump is failing at that boost pressure, his base pressure is too low or has a bad regulator, the fuel lines are restrictive, or he is losing too much voltage due to an incorrect setup. Ditto about the tone Steve, as my tone may come across as arrogant at times, but its only because I really want to see you get this thing resolved buddy...

 

I have been running a stock 4th gen tank with it vented by single small line to atmosphere. 15-18 psi boost last few years and now up to 24 psi boost this past decemeber and no issues with my fuel system. It gets warm but never overly pressurized and i dont smell alot of fumes. It vents thru the charcoal line but does not actually operate. I am not convinced you need a canister.

I would junk the aeromotive pump and stock reg and run a dual walbro and aftermarket reg with -6 return. Use stock feed as return. Run new -8 feed. 1300 hp fuel system for a 550-600 hp car lol

Could even run a bosch 044 inline with single walbro in tank, and the compound setup will make the power and hold pressure.

 

Again Justin, I threw that out there as a possibility, because I have no idea how he has his system setup, nor the effects of a poorly vented tank at that boost pressure will have because it is unheard of to not have adequate ventilation. His fuel system is getting too hot at times, he already confirmed that, fuel pressure and voltage reduce, and if its hot enough vapor lock immediately becomes an issue. It is somewhere in his fuel system and voltage supply. Again, I threw out the Vapor Canister line to see if it was plugged because we have essentially covered everything else, and there is nothing else to go by. Like Steve, I am running a boosted TPI with the stock 3rd gen tank, I am running a single pump just like he is (albeit a better pump designed for the power I am after), and am running the stock fuel lines as well. I am in fact running a vented gas cap however due to the lack of Vapor Canister. I have no issues whatsoever at the boost I am playing with, none. It is definitely in his setup, and why nobody wants to change parts to confirm it is beyond me. At 20-psi you don't play around with timing until the fueling is perfect, and at 20-psi you need quality parts, and if your losing pressure, then a part is obviously defective. Most point to the pump.

 

I want to see the car fixed too, he could have some real fun with it instead of shaking his head constantly. To be running 7.60's right through the gate at full weight with 2 pretty good size guys is pretty dang good, honestly. Looks to be a nice driving car in the vids too. It could go 6's with a bit more boost and no passenger.

A seasoned turbo/blower tuner could probably look at it and tel you exactly what the problems are anywhere on the car. Like Kurgan in Georgia.

 

Good to see the community is coming up with some real suggestions here. \

 

Yeah . This community is one of the best forums I've ever been apart of. I'm always learning something new.

 

Yep, we will help diagnose a problem, and if the OP decides to part it out we will buy up all the parts

-- Joe

 

I was thinking something similar...............

 

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the odds of having 3 bad pumps is pretty much zero. i think your 340 is fine, also. however, the dual 255's with a hobbs switch on one is a nice setup. honestly one 255 would feed your setup to this point.

rails- i am mostly familiar with LT1 stuff, but comparing the 2 rail systems, the tpi rails may actually be BETTER than the lt1 rails? the tpi rails have 2 crossover tubes as opposed to just 1 on the lt1 rails. they also have that big hole on one to attach a feed line if you wanted. that looks like it would work great. having said that, the stock LT1 rails with aeromotive regulator are good to over 550whp i know.... so your rails with a -8 feed and -6 return with aftermarket regulator should without a doubt be good to go. i would add a large vent to the tank while its out to keep from having to deal with the loose gas cap jazz.

dont know about the sts turbos, but its a shame your precision died. did you get a quote for repair? i have to wonder if there was an oiling issue? if thats the case, i can't explain why the chinese turbo is surviving just fine.

i have a masterpower 70mm in need of repair as well.

 

gone

 

my t-netics unit has a 2.5" outlet, I imagine some other 76's do aswell

 

I'm no turbo guy at all but if u already have the one with 3" could u not just reduce the pipe size a few inches past the outlet ? Instead of buying a whole nother turbo ? Or even run 6" of 3" then neck down to 2.75" for 3-6" then down to 2.5 " or somethin ? Idk just a suggestion

 

i guess they were talking about the turbine side of the turbo being too small? i know that a pair of those 6766 turbos can lay down 1500whp as twins on 400ish cubes. (i'm not up on my single sizing)

 

gone

 

hmm not real sure on that. im assuming they were considering the tpi intake with that 600hp quote. 20psi on a tpi intake would be like 10psi on a victor jr or something like that i would imagine.


this car had a pair of 6766's on a 408 ls engine. i recently purchased them from him.

 

C'mon page 10............Bump.

 

I make 500 per bank on a 64.5 mm turbine p trim, but exhaust mass of 3.3L of motor isnt the same as 5.7L of motor. I would have thought what goes in comes out so 500 whp of air mass goes into exhaust. So why do cubes matter? Well it apparently does to some degree because smaller motors get away with smaller turbines. The compressor side sets shaft speed of turbo so turbine wheel operation is set. depending on that speed the flow performance and pressure ratios change across the housing. 4.8-5.3's do well with s400 87mm turbine wheels but guys note issues with larger 6-7.0 motors when shooting for big power. Compressor could flow the air but cant because of how the engine sets operating characteristics of the compressor wheel. Set pressure ratio for given mass flow which sets speed. Thats why one turbo could support a wide range of power, really depends on what motor its on. Bigger cubes need bigger wheels to flow mass at low pressure ratios.
So chances are playing with turbine side could yield interesting results but thats unrelated to the fuel issue imo. Back pressure changes will change how engine runs but the fuel issue is obviously something different. Still curious to see if the lower rpm tpi based motor responds better to the larger comp wheel.