hey guy's it may just be me but it seems like when you nail gas to the floor there is a little lag. im used to carberators. is this normal with fuel injection and or is there a way to fix this .the car is 02 gt with 4.10 and o/r h pipe. nitrous coming in near future.

 

When I first got my car I put 89 octane fuel in it and it would hesitate a little when you punched it from a stop. I put 93 octane in it and that went away.

 

i already run 93 octane maybe i'm just comaring it to the 400hp maverick that i sold like i said im usred to carb's but i always heard f/i was more responsive.

 

If you end up with a larger plenum and TB, you will improve your throttle response.

 

On the note of 93 octane, unless you are running nitrous, higher timing, or a blower, there is no reason to run higher than 87 octane. The owners manual even states this. A lot of people have had hesitation problems, then switched from 93 to 87 octane, and the problem went away. Try that, just one tank.

 

I saw a dyno run with a porsche 911 on 87 octane and then 93. Switching to 93 it picked up 5hp and like 2 or 3tq. Running on the lower octane fuel retarded the timing thus resulting in a little less power.

 

If you have an auto trans there will be a lag while the tranny shifts into a lower gear.There will be a slight lag with fuel injection because it takes time for the air in the intake tube to get moving at the higher speed and for the MAF sensor to read the increase in flow.Carbs are closer to the combustion chamber and,properly tuned,can give a quicker response.Higher octane than needed serves no purpose other than to part you with more of your hard earned money.The HP increase with the Porche probably was a result of a knock sensor(I don't know anything about Porche's).Two valve 4.6's don't have knock sensors,four valve 4.6's do.Four valve engines will pull spark advance out when running ANY octane rating when they sense a detonation event.You can try this one out by whacking one of the valve covers near the top center hard enough to fool the knock sensor.The engine will pull advance and the idle speed will drop for a second or two.

 

Exactly, the porsche prolly had a knock sensor.

 

Im not arguing the point on the owners manual, but I'm skeptical of some things even if its in the manual.

 

Ok, but I have used 87 since day one, and it makes no difference here.

 

So...

The 96-04 GTs do not have knock sensors to be able to sense any pinging at 87 octane, so timing can't be pulled.

Now, the '05 GT, it's setup like the porsche like you mention. Higher octane will result in the computer NOT pulling timing, resulting in better numbers.

On the 2 valves though, you will not gain any power and can actually reduce power and performance running anything higher than 87 octane. So, save your money and run 87.

 

The ONLY reason why a 2V stang should run anything other than 87 is if you have a power adder, timing advanced, or experience knock.

If you do not have a power adder and have stock timing AND get knock, the knock is either caused by bad gas, or deposits in the combustion chamber. Deposits in the cumbustion chamber can cause a increase in pressure which will cause knock unless higher octane fuel is used. If you are one of these people, use SeaFoam or a similar product to clean your motor.

 

The tune I have requires 93. Another .10/gal isnt a big deal.

 

Oh ok, then that makes sense, just didnt mention it before, thats why I was so confused.

 

That's a good point. As gas goes up in price, the percent difference between 87 and 93 has gotten smaller.