Safe Fuel Pressure Level

[EEngineer]

Since my installation of the intake, I've been getting crazy bad gas mileage.
The intake is so good that it makes the MAF sensor think there's so much air coming in, the injectors squirt in crazy amounts of fuel that the engine can't burn especially when i'm revving higher than 4000.

how bad...try 20-22 MPG on a 5SFE..

I don't want to lose the SRI so only way to do it is to mess around with the fuel delivery system.

I installed an adjustable fuel pressure regulator. Right now after the installation the regulator is at 38PSI idle pressure, a lil rev goes up to 42-45.

a AFPR will change the whole map of fuel delivery overall, leaning out all the way from idle to higher revs. So if I overly constrict the fuel pressure, I think i'm risking of blowing up my engine lol.

so, someone please tell me how much is too much.
i dont want crazy good gas mileage..like 40mpg...I'd be happy with around 28 which is acceptable i think.

[new echo owner]

Have you check the O2 or A/F sensor, reading, wouldn't that give you a more accurate picture of what your engine is doing?

N.E.O.

[EEngineer]

well, i might go ahead and replace my O2 sensor.
But then, it is said that if O2 sensor goes, I should simply get an engine light.

[EEngineer]

how can i get a reading?

plus replacing O2 sensor is expensive, that shit is like 100 bucks a pop

[new echo owner]

I am not saying that you have a bad O2 sensor, the readings from you sensors will give you some ideas on whether the engine is running too rich or whatever it is doing. It is a feedback system, whateveryou run through the engine will have to coming back out from the exhaust, so utilize what you have on the car and find out where you are at. You will probably need a scanner for that information but if you are going to modify your car, it would be a good tool to have.

N.E.O.

[Stillrunning]

Originally Posted by EEngineer

The intake is so good that it makes the MAF sensor think there's so much air coming in, the injectors squirt in crazy amounts of fuel that the engine can't burn especially when i'm revving higher than 4000.

I'm trying to figure out the above statement. This is a 94 5SFE? Doesn't that have a MAP not a MAF. And if it is a MAF doesn't the MAF measure the actual airflow so there's little thinking involved? And how much extra flow did WeaponR say you would get - more than the engine could handle?

[Venom_5]

what the f*** are they putting in the drinking water these days?

no aftermarket intake on a 5S-FE will trick the ECU into thinking ANYTHING ... air intake temps and volume change a minimal amount, and the stock MAF/AFM/MAP or whatever you have on your car (in this case, MAP) can handle much more than your intake

dont make these ridiculous claims (like your ridiculous claim about k-sport springs being progressive) without putting a wideband o2 sensor & gauge on your car, and id be willing to bet money that the intake didnt change it from the slightly rich position that the car comes with from toyota

[frenum49]

I don't think I would try to lean this engine out. An easy way to find out if you are indeed running rich would be to take your wheels somewhere, (garage, autozone, etc.), that can put a good scanner on it. Then you can see if your O2's are switching properly. The PID should show them moving rapidly from lean to rich with very fast output changes. If one is switching too slowly or is stuck you will know right away. They should pull any codes you might have at the same time. A lot of these codes on our earlier diag system will not light the MIL.

[EEngineer]

Originally Posted by Venom_5

what the f*** are they putting in the drinking water these days?

no aftermarket intake on a 5S-FE will trick the ECU into thinking ANYTHING ... air intake temps and volume change a minimal amount, and the stock MAF/AFM/MAP or whatever you have on your car (in this case, MAP) can handle much more than your intake

dont make these ridiculous claims (like your ridiculous claim about k-sport springs being progressive) without putting a wideband o2 sensor & gauge on your car, and id be willing to bet money that the intake didnt change it from the slightly lean position that the car comes with from toyota

listen.
I'm here to learn and get some opinions. I dont need you to come here and give me insults just because you think I'm wrong or you know better. I think you owe me an apology.

[Eye8Pussies]

okay boys, let's keep it down in here. he asked a simple question, and a simple answer would be nice.

[Luckynumber5]

The intake isn't gonna mess with your economy like that, you have other problems.

[Venom_5]

Originally Posted by Luckynumber5

The intake isn't gonna mess with your economy like that, you have other problems.

theres your answer in the simplest form possible ^

if you want, i will throw a wideband on my car and give you numbers with/without my SRI to prove it...

[EEngineer]

of course, everyone's got some points to back themselves up. Nobody here is an idiot, so we have our reasons to do the way we do things.

I have spent like $350+ trying to solve my gas mileage problem.
I even poped my valve cover to check for sludge and stuff. Seafoamed, injector flushed, de-carbonized.
I didn't want to throw another 100 bucks here 100 bucks there to TRY to solve my problem. I wanted something that will GIVE RESULTS even the slightest progress would do.


Only two more things to consider, O2 sensor or the EGR is blocked. EGR problem is highly unlikely, but up here where I live, an O2 sensor is 150 bucks. A fuel pressure regulator is $45.

YOUR CHOICE.

if a FPR can solve 60% of my problem for now, I'm good with it until I save up enough for another O2 sensor.

[Eye8Pussies]

I have to agree with the others in saying that it's not the intake...and agree with NEO as well that it's most likely an o2 sensor...it is too bad that they're not cheap, and in the end, it may not be your problem

but that being said, as you stated, you're looking more for a band-aid solution at the moment, and this may be a possible way of doing it.

the good thing about getting the fpr in the first place is that now you know that your fuel system is performing as it should- 38psi-41psi as stated in the shop manual.


as for leaning it out yourself...you're right, it will lean-out the entire power range at both idle and throttle by leaning the fuel through the fpr. But only to a point as well. I'm not too sure about the obdI, but on the OBDII, eventually, the ecu will not like it and start telling the injectors to just stay open longer and dump more fuel even though the pressure itself is turned down.

that being said, I would say that it's probably safe to lower the fuel pressure at least 5psi if not more. The only performance problem that you may encounter as you progressively lean out your mixture is extra leanness during initial throttle (I had this problem when I was boosted), but with an automatic transmission, it shouldn't be a big problem, since the fuel system will have time to catch up before the load really hits through the auto tranny. You can also keep an eye out for running too lean by checking your sparkplugs after a couple hundred miles (compare them to the pictures on the back of your haynes manual). When doing this experimentation, I also suggest you run the highest octane gas you can find (91 in the case of Toronto, or even 94 if the prices ever go down, lol) just in case.

and also, just to worry less, remember that you do have a knock sensor on your block, and it should at least prevent you from blowing up your engine by pulling timing should you try and pull too much fuel

good luck


and also on a side-note- I don't remember if you've said you've done this yet or not, but it wouldn't hurt to pull your spark plugs out to confirm that you're running THAT rich as well

[Luckynumber5]

unplug the vacuum line from the fpr, it increases pressure with vacuum. You can drive around with it unplugged and the car will be fine, that should lean it out a little since it should now have a static (and lower) fuel pressure.