i dont know how often people ask this. but i think its commonly known ur not supposed to boost with less than 1/4 tank. well i'm just wondering why? your thoughts and where i can read more about it.

thanks.

steve prew

 

It's more of a recomendation because the baffles in the fuel tank that push the fuel towards the pump can brake, and with low gas and hard cornering, the pump can end up starved. If all of a sudden you're running lean when boosting, kaboom.

Theres just a better chance of detonation when boosting then when not boosting. I just plain don't let my car get below 1/4 tank. It hurts less to spend $30 on gas than it does to spend $40 for a full tank anyway

 

more answers please, enough to convince me this is why my engine really blew a seal.

 

When I blew my first engine, I wasn't boosting just crusing at around 70 mph on the highway with a low (on E) tank of gas.

Also, I had never changed the fuel filter.

kaboom! super grooves in the rotors and housings from the busted apex seal and toasted turbo.

I have no other explanation, the car was entirely stock.

 

Fuel slosh.

 

911gt2 did a good job explainin what happens, im not exactly sure what you are looking for in a respones or how it would help after the fact (i mean you already blew your engine, learn to have more fuel ready to be feed to your engine)

 

Like it is said above.....fuel pressure drops, and you're looking for a motor. CJ

 

i appreciate the responses guys. i still dont believe that this was 100% the problem of the seal blowing. the engine had 1000 miles on it since i had it rebuilt. ive been running the car the way i did for over 2 years without inccident. im not complaining because i can understand i shouldnt have run it low. but im more worried that this isnt the problem, and after it gets another rebuild tomorow the real problem will kill it again. what do you guys think.

steve prew

 

Hmmm... I think I'll order that FP gauge now.

 

perhaps it was another problem, what kinda injectors did you have at the time? did you flow test them the last time you had yoru engine out?

 

stock injectors, i was running 12lbs at the time.

 

well I blew my motor this way. Racing a WRX up a hill, with no gas, at redline.

I'd say that detonation from fuel starve is enough to kill a motor regardless of age or mileage on the motor.

 

??

You're just spending $30 more often than you would spend $40.

 

That doesn't help either. When Demetrios tuned my car he didn't go up to 12psi because he was worried about Inj. duty cycle. He said he wanted to be on the safe side because should anything slight happen in my fuel delivery the engine would be adios!

 

im so glad i read this thread, im about 1/4 full on gas and i do occasional boosting here and there.. this thread possibly saved my engine..

 

Well it's common sense too... Boosting eats up 2X-3X more fuel than running under vaccuum... so I usually limp to a gas station once past 1/4 so that I can pick the station and my gas situation doesn't force me to go to some cheap place, where the gas is questionable....

 

As I stated to prew in private mail, high mileage injectors may not be flowing as much as they should be at a given duty cycle, the fuel filter may be clogged, the pump relay may not be switching the pump to 12V+, the pump may be weak from age, the fuel pressure regulator could be faulty, and as mentioned, fuel slosh in the tank can run the baffle area dry when gas is low, causing momentary starvation.

There are so many factors in the fuel system which can affect actual delivery to the engine that you really need to take a look at each one individually and do what you can to mitigate the risk in each case.

If I were buying a "new" FD today, the first thing I'd do is replace the pump and fuel filter. It's just cheap insurance. If I had the engine apart for any major modifications, I'd have the injectors cleaned and flowed or have them replaced. I'd also check to make sure the fuel pump relay was in good working order, and check to make sure it was coming on, or modify the system to give the pump 12V+ full time, which is what many Supra owners do. And finally, I'd add a good rising rate fuel pressure regulator with a gauge so I could be sure of what the pressure level was. Even adding just the gauge could help troubleshoot problems with fuel delivery and catch it before something bad happens.

Bottom line, you need to do some basic maintenance and improvements on your car before you start modifying it and running higher boost, even if it's only 12 psi. I know people who have blown their engines at 10 psi. It doesn't take much... just a momentary lean condition and a couple pings.

I'm sorry prew, but there's no real indication that your tuning was to blame for the loss of your engine and you were driving the car when it happened and admit to having a low tank. If you can't give more details, then it's very difficult to help troubleshoot what went wrong.

 

thanks for all the responses. i needed to hear the reasons i guess to realize that the low fuel is a legitimate problem, enough to blow my motor. the car is in the shop now, im gonna have them look at the fuel system.


thanks everyone.

steve prew