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Discussion Starter · #1 ·
Has anyone dealt with a car that needed more fuel when seeing higher temperatures in general? My belief, as well as my tuner and main mechanic, is that you need slightly less fuel when intake temps are hotter but for some strange reason I'm seeing the need for much more fuel at higher temperatures. This means I need as much as 30% more fuel when the car gets hot.

I unfortunately have not installed my stupid fuel pressure sensor for my AEM yet as the sensor doesn't fit where I had hoped it would. I may get time in the next few weeks to do this as another data point but I have had someone watch my engine bay fuel pressure gauge to make sure the pressure rose with boost properly. However, the engine bay might have been cooled much better than a normal street condition to hide the problem or not run long enough to cause problems with the pumps to overheat. I'm not sure. Anyhow, any suggestions as to what to look at would be appreciated.
 

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How exactly are you determining that you need more fuel, are you leaning out?

Any chance one of your fuel lines is getting heated causing the fuel to vaporize in the line? Long shot, but about the only thing I can think of.
 

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Discussion Starter · #3 ·
When I'm idling and the car gets hot, it starts to see the need for more fuel through the wideband feedback. The car will be doing fine but as the temps rise, the fuel needed goes from a normal expected amount to x% that ends up being as high as 30% at times whenthe car's intake temps rise. Normally in the AEM people start to subtract fuel by default slightly as the temps get hotter. With that default setup, my car will start to get ultra lean. The wideband feedback will note this and begin to add fuel and that's where I get the 30% number from.

I'm also starting to wonder if one of the fuel lines is indeed getting hot and causing problems. I also wonder if my fuel pumps in some strange way.
 

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You could have too much adjustment in your warm up enrighment table thus covering up a slightly lean fuel map....
 

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Sooooooo JDM
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You're running Walbro's, correct? If something else, maybe your fuel is getting heated up then returned back to the tank. I know with some of the larger pumps this can become a serious issue, especially when low on gas. The solution is a voltage controller that will run the pump(s) @ 9v for cruise sitiations. But if you are indeed running Walbros, that's probably not the issue.

Ryan
 

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Discussion Starter · #6 ·
I'll double check myself but Sean assured me it's not warm up enrichment.

racing fan said:
You could have too much adjustment in your warm up enrighment table thus covering up a slightly lean fuel map....
 

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Discussion Starter · #7 ·
I'm actually running two stock pumps which I think I might change sometime soon as the stockers might outflow but they definately suck major power to do the same work. This is putting a major current draw on some wires that in the tank aren't probably cutting it. This is the only area I didn't finish rewiring since I've owned the car. Anyhow, I'm on twin stockers.

Ryan, I think I'm going to look into what you've mentioned but is there really any easy way to test this without replacing both pumps with Walboros? I want to switch but I'm trying to not spend much cash on the car right now. If I have to, I will spring for the two pumps though.

Thanks.

Ryan23 said:
You're running Walbro's, correct? If something else, maybe your fuel is getting heated up then returned back to the tank. I know with some of the larger pumps this can become a serious issue, especially when low on gas. The solution is a voltage controller that will run the pump(s) @ 9v for cruise sitiations. But if you are indeed running Walbros, that's probably not the issue.

Ryan
 

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silvino said:
I'm actually running two stock pumps which I think I might change sometime soon as the stockers might outflow but they definately suck major power to do the same work. This is putting a major current draw on some wires that in the tank aren't probably cutting it. This is the only area I didn't finish rewiring since I've owned the car. Anyhow, I'm on twin stockers.

Ryan, I think I'm going to look into what you've mentioned but is there really any easy way to test this without replacing both pumps with Walboros? I want to switch but I'm trying to not spend much cash on the car right now. If I have to, I will spring for the two pumps though.

Thanks.
I would just make sure you had a full tank and see if the problem is still there. While it may be easy to heat 3~5 gallons, I wouldn't imagine this would happen so easily with <10 gallons. You could also potentially have a pump that's falling off after it gets warmed up too. I know with my pump, I can vary my A/F @ Idle by a full point by just flipping the override switch on my Single (Aeromotive) A1000. The switch overrides the box which runs the pump @ 9V for cruise situations (thus keeping fuel cooler). Check voltage at the tank connector cold and after the car warms up. You should have ~13.5V there. You mentioned that pressure is not falling off under boost, right? If there is anyway to temporarily extend your gauge out to the windshield, just to double check, it might be a good idea. When Sean M and I left the dyno, we got on the highway and noticed that Fuel Pressure was only rising .4~.5 bar over the base pressure. This wasn't an issue the day before but all of the sudden, Whammo, pump started to fail. Looking back at my fuel map, numbers were rapidly approaching 255 RAW up top too :eek:

Ryan
 

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Sil, this may be a stupid question, but what does your IAT fuel compensation table look like? Do you have it pulling fuel at temps increase? I don't know how you have it tuned, but if you have the "stock" IAT table, it's going to pull fuel as temps increase and that could be the reason why O2 feedback adds fuel back in. But if your IAT table isn't pulling fuel, then I would have to say check the pumps like others.
 

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I posted this to the list, just a thought:

I’ve been trying to figure out why my fuel pressure drops about 8~10 psi after everything is warm. It’s worse coming to a stop and idling, not as bad idling with the hood open. I put in two new pumps, checked voltage, changed the filter and replaced the fpr. Even put in a fuel cooler that is helping some at cruise. Someone mentioned heat soak of the regulator, which mine is mounted by the intake manifold like most in the engine compartment. I got a can of cold spray the other day (stuff that’s used to cool circuits boards for testing) and blasted the fpr while it was hot and my pressure was down. The pressure came back up to normal like it is when the engine is cold. My next step is to move the fpr as far away from engine heat as possible. Just an observation for anyone having a similar problem with falling fuel pressure.
 

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supra400hptt said:
I posted this to the list, just a thought:

I’ve been trying to figure out why my fuel pressure drops about 8~10 psi after everything is warm. It’s worse coming to a stop and idling, not as bad idling with the hood open. I put in two new pumps, checked voltage, changed the filter and replaced the fpr. Even put in a fuel cooler that is helping some at cruise. Someone mentioned heat soak of the regulator, which mine is mounted by the intake manifold like most in the engine compartment. I got a can of cold spray the other day (stuff that’s used to cool circuits boards for testing) and blasted the fpr while it was hot and my pressure was down. The pressure came back up to normal like it is when the engine is cold. My next step is to move the fpr as far away from engine heat as possible. Just an observation for anyone having a similar problem with falling fuel pressure.
Interesting, do you have any pics of where it's mounted? Good idea BTW with the cold spray ;) One other thing you may want to try is hooking a vaccum pump up to the regulator while it's nice and hot. Tee in a known good gauge (I've got an EMS, so I just watch engine load via MAP sensor) and see if you still get a linear rise. Maybe you have a slow vaccum leak that's only evident with heat? Wait a minute....did you say at idle? I guess a leak there would be increasing pressure, not reducing it. :( FWIW, my regulator is mounted next to the intake, outboard side, and if anything, I gain .1 bar of FP when the car is nice and warmed up. This is with the big ass Aeromotive heat pump..err...fuel pump :D.

Ryan
 

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I've got it mounted along side of the intake manifold. Wish my pressure was that solid. Vacuum line is good and tight. I'll see what happens when I move the regulator away from the heat.
 

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Discussion Starter · #13 ·
This is pretty much how mine is mounted as well.

supra400hptt said:
I've got it mounted along side of the intake manifold. Wish my pressure was that solid. Vacuum line is good and tight. I'll see what happens when I move the regulator away from the heat.
 

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supra400hptt said:
I've got it mounted along side of the intake manifold. Wish my pressure was that solid. Vacuum line is good and tight. I'll see what happens when I move the regulator away from the heat.
Hmm, mine is there as well and isn't prone to heatsoak (I haven't tried hitting it with cold spray though). Same Aeromotiveregultor too. Strange for sure....

Ryan
 
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