I just tuned my car and had perfect afr all across. Now all the sudden the very next day I'm running leaner than crap. Everytime I mash on the throttle for more than 3sec, it leans out. Doesn't matter how much boost or what rpm, it just leans after a certain amount of time. The only thing I've changed or added was race gas. I'm thinking fuel pressure is dropping from a clogged filter cause I've added at least 20% more fuel. I've got a new pump that's going in tomorrow, I'm hoping that's it but wondering if it could be the leaded gas I ran.

 

I'd like to know too... 110octane is what most places sell!!!

any info would help...

 

I ran 100% 120 octane. I don't know if that means more lead or not but something is more than wrong

 

i just wanna know why you were running 120 octane....

 

It can also be your o2 sensor, check that first race gas has a very strong tendency to foul these up.

 

i remember a few years back when leaded race gas ruined my fuel pump and injectors.

 

last I knew anything over 100 Octane has lead in it. And most of our cars won't run very well with leaded gas... not for long anyway...

 

ive heard that if you tune on pump gas then add race gas to your tank it can affect the a/f, i dont remeber if it was lean or rich but it can affect it. try go back to pump gas and see if it still leans out

 

Just go back to pump gas. You need to be retuned to run on race gas. Also unless you have a really crazy timing map with high compression or over 500+whp, there is no need for 120. You can get up to 110 or 114 in unleaded.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Black-LS &raquo;</TD></TR><TR><TD CLASS="quote">last I knew anything over 100 Octane has lead in it. And most of our cars won't run very well with leaded gas... not for long anyway...</TD></TR></TABLE>

Sunoco makes an unleaded 104 . They sell it @ Cecil Co. MD.

 

Yup, you're leaning out, since you're not tuned for race gas. Surprised you instrumentation shows it, normally reads false rich as a lot of still burning and unburnt fuel/air blows out your exhaust valve when you try to fire it so late with pump gas timing.

 

It's not that I just added race gas and started pounding on the throttle. I actually tuned with race gas. Parked the car for a night and now it's running lean. Even with race gas. Adding 20% more fuel should have been way more than enough to richen any car.

 

Apologies, I thought you said that you were tuned three days ago, then just dumped in some racegas.

Checked fuel pressure lately?

 

Race gas can actually destroy certain o-rings or gaskets in a stock fuel system. Pieces could lodge anywhere in the fuel system.

 

If you are running race gas and have not been tuned for it, you will run into the problem. You would need to advance the timing to run such octane, if not....your EGT's will be super high because you would be delaying the timing too much for the slower more stable burn of the high octane fuel, resulting in the rise in EGT's. This is single most reason you make more power from a high octane fuel. The ignition timing you are able to run on the stable, slow burning fuel is the biggest reason you would want to run a high octane. And obviosly allows for more boost, which would be even more power(for the FI guys).

But this is obviously not the case, as you are tuned for the octane u are running. Do you have a loss of fuel pressure?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by earl &raquo;</TD></TR><TR><TD CLASS="quote">Race gas can actually destroy certain o-rings or gaskets in a stock fuel system. Pieces could lodge anywhere in the fuel system.</TD></TR></TABLE>

Yup, I had the same problem. Race gas would eat away at the rubber fuel lines and get clogged in my fuel filter and float bowls (carburetor).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by D.I.D. Race &raquo;</TD></TR><TR><TD CLASS="quote">

Yup, I had the same problem. Race gas would eat away at the rubber fuel lines and get clogged in my fuel filter and float bowls (carburetor).</TD></TR></TABLE>

This makes me feel much better than. Going to change my filter and pump tomorrow hopefully.

I have a fuel pressure gauge but it is electronical and takes a second to get caught up to actual pressures, that's why I'm getting rid of it. So it's hard to say if my fuel pressure is stable while boosting. I get base pressures that are stable, then when I boost it'll reference like it should. But when I start to run lean, I let off the gas and it's too late for the fuel gauge to respond.

Anyways, thanks for the responces. Hopefully I can get this boosting again and see what times I can get

 

changed filter and pump and still the same. Leaning after a couple secs of wot. I even went as far as replacing the pump with an RX7 twin turbo pump I had which should be good for 350whp.

The only thing I can think of now would be the injectors. Anyone else have a different opinion?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RedTT &raquo;</TD></TR><TR><TD CLASS="quote">changed filter and pump and still the same. Leaning after a couple secs of wot. I even went as far as replacing the pump with an RX7 twin turbo pump I had which should be good for 350whp.

The only thing I can think of now would be the injectors. Anyone else have a different opinion?</TD></TR></TABLE>

How do you know it's leaning out? Are you running a wideband? Perhaps you have a faulty connection. Please don't say your going off of the autometer a/f gauge.

 

yeah, I have a wideband.

I even went as far as adding 20% more fuel and still same thing. Runs rich right when I mash the throttle. Then slowly makes a turn for lean. It almost seems like I'm maxing out inj but these are 450cc at only 8psi of boost

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RedTT &raquo;</TD></TR><TR><TD CLASS="quote">yeah, I have a wideband.

I even went as far as adding 20% more fuel and still same thing. Runs rich right when I mash the throttle. Then slowly makes a turn for lean. It almost seems like I'm maxing out inj but these are 450cc at only 8psi of boost</TD></TR></TABLE>

well that definetly doesn't sound right. Something going on. Have you checked out the plugs? How do they look? Are they showing signs of running lean/detonation? Are you datalogging? You might have something wrong at some point in the map.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lonnieboost &raquo;</TD></TR><TR><TD CLASS="quote">It can also be your o2 sensor, check that first race gas has a very strong tendency to foul these up.</TD></TR></TABLE>

Did you check this. 120 has a lot of lead it can foul your wideband up and cause it to act erratically

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by lonnieboost &raquo;</TD></TR><TR><TD CLASS="quote">

Did you check this. 120 has a lot of lead it can foul your wideband up and cause it to act erratically</TD></TR></TABLE>

that's right! Leaded gasoline shortens the life of your o2 sensor.