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Ok so from the beginning. I am so close to having this tune perfected and then it starts.....
1st method and equipment:
Each session is around 4 third gear pulls which go far into 4th and total of 20 something minutes of normal driving.
Car
New motor with big street port and new "SP" twins.
New supra TT fuel pump (re wired), stock lines. New fpd, 2200 secondaries.
PFC,
Water inj smallest nozzle
First 2 sessions go great. Very small changes in fuel cells. I am talking under 2%. I am think "hell yeah.... one more session and I am finished". Nope.... 3rd session she starts leaning out in high rpm high boost (P17, P18).... enrichen some fuel Speaking like 5+%. It gets to cool for around 15 min. Next session... same. Still lean... start enriching more.... next the same... then I stop session because I don't want to blow up of course! It will creep slowly into 12s then mid 12s I let off.
The water temp, oil temp, air temp (does have water inj), and all parameters are the same for each session for what I see.
Could it be I need bigger fuel lines? I don't think I am pushing over 360 to the wheels. Some are saying I may be hitting 380 with these "sp" twins @ 14psi and my fuel lines need upgrading so the pump may be over heating. Fuel pressure was verified a long time ago to be good. I will eventually install a pressure gauge permanently I guess, but do not think this is the problem.
This is very, very frustrating. Again, very frustrating.
your fuel lines arent the problem. if you are suddenly leaning out like this then i would check the pump again. did you keep the o-ring fitting at the feed pipe or did you change to a standard fuel line with clamps? i would watch fuel pressure on your next run. its possible if you still have the o-ring that it just let loose.
As mentioned, this would point to a fuel pressure problem. If you're not already running an adjustable FPR with a pressure sensor/gauge port I'd at least try to rig something.
Thanks guys. I will pull the pump. I have to install a baffle in the tank anyway. I also never finished wiring on that side of the bulkhead. I will definitely check the O-ring.
To answer the question. Yes it is installed as the oem pump was (with the o ring)...
Thanks for the ideas
Now that I think of it I don't think it would be an O ring issue as this has happened on different "sessions"... 3 or 4 separate occasions. Like different days. 1st few runs great then after that it started to lean out. Maybe it is just the wiring to the pump in tank... it has to be something over heating or failing as it gets hot? No idea, but I will definitely pull the pump.
Sucks to here this! Are you logging fuel pressure?
If not I would start looking into what your fuel pressure is doing on these runs.
Also stock bulkhead connectors are questionable when running a upgraded pump.
Numerous people have had the connectors/wiring get hot and melt..
I will add some wires through the bulkhead and get get back with you guys as this could be the problem. Maybe it is just heating up. I would still think it has time to cool, but maybe not.
I was suppose to get this awhile ago, I think I slacked off on it as it was overkill and not necessary at the time.
Fuel pressure should be a certain base amount - a stock car is 36-38 psi with engine off and fuel pump running with the F/P and GND jumpered in the diagnostic box. With the engine at idle, it will be lower - the vacuum line to the FPR will lower fuel pressure at vacuum and raise it under boost.
Typically the FPR will raise fuel pressure 1 psi for each 1 psi of boost. So, if you have 36psi base pressure, at 10 psi of boost you should have 46psi fuel pressure. This maintains a higher fuel pressure than the manifold air pressure. Imagine if you ran 36 psi of boost and 36 psi of fuel pressure - nothing would squirt out the injectors since the pressures are the same.
When you're doing a full power pull, the fuel pressure should come up with boost and maintain that ratio to redline. If it starts dropping off that can mean a few things - either the fuel pump isn't putting out enough fuel for demand due to it being undersized or not getting enough voltage, or there is some restriction like a clogged fuel filter that's causing fuel pressure to drop.
Also I'm not sure what the range of power is for that Denso pump. It's a pretty mild upgrade. With those larger injectors I would have gone with a Walbro 255. I don't know if that's the problem but something to think about.
Regardless, that's the only thing I can think of it being at this time. The engine is static at this point, it injests x amount of air at y load and z rpm. if you give it the right amount of fuel you hit your AFR target and that should be fixed. If it keeps dropping, that is telling me you're running out of fuel somehow - not from the tune or injectors but on the supply side. If it was an ignition issue I could see it getting more rich than lean in a similar circumstance.
Also you don't necessarily have to rig up a fancy method to computer log fuel pressure. You can T into the fuel feed line and run a hose up to a fuel pressure gauge and zip tie it to the windshield wiper. Especially if you are working in a fixed environment like a dyno. It's going to be super obvious just watching that gauge if the pressure is dropping off.
I second the o-ring fitting that the denso pump uses with the factory fuel pump hanger, if those don't seat right/are missing/old and flat it can cause you to lose pressure there too. I like the idea though of switching to a walbro pump. The 525 works, just get it from a known good retailer. (F90000285). Also send your injectors back out to get cleaned and confirm nothing got sucked into them. Nothing is too small to consider when you're chasing issues without a clear root cause. How old is your OEM FPR? If you're not ready to upgrade to an aftermarket FPR, try replacing that as well. When you only find this problem on the dyno it's hard to only step through one issue at a time.
Definitely seems like a fuel delivery issue, I would monitor fuel pressure as Dale mentioned before digging into anything. It happens after a couple pulls could indicate it is heat related, the pump should cool by the fuel but if the wire gets hot enough it'll create more resistance.
Thanks all. I will let you guys know what I come up with. 1st I will pull the pump and see how everything looks. Then I will run some wires through the bulk head. Anyone have an idea what size the ring terminals are? I will pick up some ring terminals for the wires. That is probably all I am missing to get this project moving. I guess it is time for a fuel pressure gauge to be installed. I just remember checking fuel pressure after a dyno session issue and all was good.
I will keep this updated for anyone who may have the same issue some day.
I'm sure that doing all that work will be beneficial, however I'm of the opinion that 'throwing **** at a wall and seeing what sticks' is usually not the best way to go about doing things. I'd validate pressure, if pressures go down in the same fashion as before I'd validate voltage at the pump. At least then you know with certainty what part of your system/design ethos is compromised.
I need to pull it all anyway as I never rewired in tank. This set up is suppose to be good for 400 easy from what many have said. I get all cars are different, but I am sure I am not an exception pulling 400whp at 14psi on "sp" twins or something that should require a bigger pump or lines. That would be cool.
If you're going to spend money on a fuel pressure gauge, I would look for one that can be logged by the ECU. Every modern standalone can do useful things with a fuel pressure reading, and it sounds like even the PowerFC crowd has figured out how to log pressure sensors on some of their setups. Otherwise you'll be stuck doing hacky things like trying to point a camera at the pressure gauge and boost gauge during a dyno pull. That's better than no info, but the last thing the driver needs is another damn gauge to watch when he should be looking at the road.
If the problem seems heat-related I would take a look at where the fuel pressure regulator is mounted in relation to the turbo and exhaust. I've seen some scary setups with the FPR just a few inches from the exhaust housing. A less-dangerous problem would be an inadequate relay heating up and decreasing the voltage delivered to the fuel pump. Try tapping onto the fuel pump power and ground wires with a multimeter, if you can rig something up that allows you to safely measure fuel pump supply voltage during the dyno pull that would be useful. That won't tell you what's happening on the other side of the bulkhead, but it can help prove or rule out quite a few other potential electrical problems.
If you're going to spend money on a fuel pressure gauge, I would look for one that can be logged by the ECU. Every modern standalone can do useful things with a fuel pressure reading, and it sounds like even the PowerFC crowd has figured out how to log pressure sensors on some of their setups. Otherwise you'll be stuck doing hacky things like trying to point a camera at the pressure gauge and boost gauge during a dyno pull. That's better than no info, but the last thing the driver needs is another damn gauge to watch when he should be looking at the road.
If the problem seems heat-related I would take a look at where the fuel pressure regulator is mounted in relation to the turbo and exhaust. I've seen some scary setups with the FPR just a few inches from the exhaust housing. A less-dangerous problem would be an inadequate relay heating up and decreasing the voltage delivered to the fuel pump. Try tapping onto the fuel pump power and ground wires with a multimeter, if you can rig something up that allows you to safely measure fuel pump supply voltage during the dyno pull that would be useful. That won't tell you what's happening on the other side of the bulkhead, but it can help prove or rule out quite a few other potential electrical problems.
Thx Scotty. Going AEM. The FPR is oem in pretty much the oem location. I am hoping it's the wires heating up in tank... will be an easy fix.... hopefully
Just weird. If it is heat related how long does it take to cool off. It must take hours.
I will be as I need to tap I to the + wire from the relay anyway.
Looking back I should have wired the pump off a kill switch. Would be a good security feature and would eliminate another link (relay), but oh well.
Just installed a fuel baffle also while it is opened.
did you keep the o-ring fitting at the feed pipe or did you change to a standard fuel line with clamps? its possible if you still have the o-ring that it just let loose.
this... fix that on your hanger and run some heavier gauge wire. that looks 20 or 22. switch to 14 or 16 or whatever the biggest size you can fit comfortably
fix that on your hanger and run some heavier gauge wire. that looks 20 or 22. switch to 14 or 16 or whatever the biggest size you can fit comfortably
Yep! Bigger pump will demand more current.
The smart way is to upgrade the complete wiring feeding the pump... bulkhead and all.
FYI, You can see what I did in my thread... I've had ZERO fuel issues.
03-23-21, 04:23 PM
