Junkman

We ran our first race a few weeks ago and found our second biggest problem was using 15 gallons of 92 octane per hour. We are running the car hard, but I think 3 mpg is excessive. Any ideas would be appreciated

AaronUCF11

Engine is running well? No fuel leaks or sloshing out passed the cap on hard cornering?

i dont think its entirely unreasonable, i swear i can see the needle move if i plant my foot on the throttle.

Quadprop

start with the coolant temp sensor

DIY Coolant Temperature Sensor change (PICS) ( 1 2 3 4 5 ... Last Page)

the pictures should help the car has 3 temp sensors... 15$ at oriellys

dicer

At 300 hp for one hour and approximate decent mixture for antidetonation the consumption would be 23 gallons an hour, HP consumes fuel. And unless it is steady state high speed your HP will fluctuate up and down, also of course I don't know what HP the engine is making. But 15 gallons in an hour isn't bad depending on the racing your doing. Oh and at 300 hp and very lean it comes out at 14 gallons an hour. These examples are for an engine that is pulling a steady 300 hp for one hour.
If you don't want to burn so much fuel racing, then do go carts instead of a Lexus.

Junkman

Well, if we can't fix the fuel consumption problem, a small block Chevrolet gets way better fuel economy than the Toyota motor does now and it will fit in a Lexus shell quite easily.

dicer

Not so if its pulling power the consumption will be approximately the same, unless you have some far out super economy fuel system.

Junkman

My only comparison for fuel consumption is from watching other V8 cars during the course of the race. They are fueling less often which gives them an advantage in an endurance race. There may be other ways to make the car work better and use less fuel, but I am looking for engine expertise to see possible causes and fixes. We are working on other aspects of the car as well.

djamps

Any CEL/codes? I'd swap the coolant sensor as a cheap shot in the dark. Otherwise it could be issues with the o2 sensors, egr, ECU caps, the list goes on. You should be getting better economy than the other V8's unless your car is alot heavier.

Junkman

We are going to change all the temp sensors for sure and I have an extra MAF sensor, so we will change that also. The only codes we are getting were transmission and knock sensors, but the knock sensors are new since then also. The car is going on a diet before the next race and we are planning the 95 brake swap also. More wheel and tire are also on the list. I am going to borrow some scales to see just how heavy we are. The suspension raised 4" in the front and 5" inch in the rear from all the interior and other stuff we already took out. I cut out quite a bit of spring to give it a decent ride height. The car handled well and the number one problem we had was oil starvation in the corners which led to the demise of our first engine 1 hour into the race. We changed the engine and returned to the race on Sunday morning and ran 6 hours with an extra quart of oil to reduce the oil starvation. We are building baffles into our stock pan to help control this issue.

dicer

If you wanted to be able to monitor the parameters you should have chosen an OBD2 car like a 1996 or so, you just don't have the good options with OBD1.
With OBD2 you could be checking fuel trims etc while your racing, and see if it is a sensor problem or what ever. Even having something like tight brakes, low tires or anything else that can cause a parasitic drag and rob power and thus fuel should be checked out. Are you running the CAT's? If not there could be something going on there with the fuel control. For real racing I would not want the stock Lexus ECU I would want something more user programmable.

Junkman

This is Lemons though and the idea is for it to be cheap. There are not many 96 and newer V8 cars out there for under $500. We can still monitor sensors using a scope. It is just slightly more difficult. I am not the expert, which is why I am on the forum.

djamps

Seems like weight is under control. I'd focus on sensors and ECU issues.

GasBuggy

Stock tune is pig rich under WOT. I would be looking for a way to trick it into leaning out at WOT.