Are These Low Numbers for a 3.4 Auto Cobra

[MYVENM]

built motor, but still 281ci, stock cams, 1 5/8 long tubes, 3 inch x pipe and mufflers, 3.4 whipple, 3.5 upper, 2 pound lower, built 4r70w.

Car is tuned for 110 octane. Had the car on a dynojet for the first time yesterday and with the converter locked it did 614/614 on the first pull, and 609/609 on the second pull. My boost gauge is seeing 29 psi. What do you think of these numbers? I know the auto eats up some power but i thought it would do better than it did.

 

[racin4ds]

Damn almost 30psi boost?!?!? I know there are cars making those numbers on 22psi... Is this an 03/04 cobra motor or something else? What are you using for tuning?

 

[MYVENM]

Damn almost 30psi boost?!?!? I know there are cars making those numbers on 22psi... Is this an 03/04 cobra motor or something else? What are you using for tuning?

yes it is a 03 cobra. sct is what the car is tuned with.

 

[stangaholic280]

I'm running a 2.8 KB so I don't know how much they compare but I really don't think a 3.5" pulley should be making 29#'s of boost...even with a lower. But assuming it is, yes 29#'s of boost should be miles above 600 HP. I made 750 with 23#s on my KB.

Edit: But then again...I'm not real familiar with how autos affect dyno numbers. Still seems off to me.

 

[cbr repsol]

with 29psi it should be high 7's thru your auto. A guy ive seen was throwing 30 psi with his 3.4 and was around 850rwhp i think through a manual gear box. Then the block completely cracked and threw the crank snout. Good luck

 

[cbr repsol]

Edit: But then again...I'm not real familiar with how autos affect dyno numbers. Still seems off to me.

Auto's are usually 25% drive terrain loss

Manual's usually 15%

 

[GodStang]

I'm running a 2.8 KB so I don't know how much they compare but I really don't think a 3.5" pulley should be making 29#'s of boost...even with a lower. But assuming it is, yes 29#'s of boost should be miles above 600 HP. I made 750 with 23#s on my KB.

Edit: But then again...I'm not real familiar with how autos affect dyno numbers. Still seems off to me.

Pulley combo for the 3.4L and the 2.8L are different.

Numbers are not bad if you are running stock inlet. Do you have the crusher or Behemoth inlet? Not running those at that much boost will kill a lot of power.

 

[stangaholic280]

Pulley combo for the 3.4L and the 2.8L are different.

Numbers are not bad if you are running stock inlet. Do you have the crusher or Behemoth inlet? Not running those at that much boost will kill a lot of power.

I figured they would be different...I was just saying that I doubt they are so far off that I'd be making 18#s of boost with a 3.5 and he's making 29 lol. :lol1:

 

[GodStang]

I figured they would be different...I was just saying that I doubt they are so far off that I'd be making 18#s of boost with a 3.5 and he's making 29 lol. :lol1:

The stock 3.5" on a 3.4L makes ~26psi on a stock setup. Adding a 2lb lower will put him in the 28-29psi range on a stock setup. You have to realize that every turn of the 3.4L you are moving 3.4L of air and every turn of the 2.8L you are moving 2.8L of air. You are moving .6L or air more. Forcing it into the same area you make more psi with the same setup on the 3.4L than the 2.8L.