Hi,
I finally got to dyno my car a year after I built it up. I dyno'd it at Alternative motorsports in OKC. Here are the numbers: SAE peak 352.7 HP 339.9 TQ. If anyone can tell me why the numbers are so low (I believe I'm supposed to have atleast 400-420RWHP) please let me know. My mods are in my sig. Everything on the dyno looks good except the numbers. Car ran/runs strong. Great torque curve but low numbers. Air/fuel ratio looks about right. Anyone with any ideas please let me know. Thanks for all your help.

 

is this package rated flywheel hp or rear wheel hp. if its rated flywheel the number are that way due to drivetrain loss.

 

How new is the clutch?

 

My guess is you have lots of knock retard. Or a mechanical problem in the motor. How many miles on the bottom end? Bad rings? How fast does your oil get dirty? Any gas in your oil?

I had the same issue last year. 390rwhp vs 422 rwhp this year.

 

how many miles on the motor? i seems as you hav all the supporting mods...how does it run at the track? bc i got my 306 dyno and they said a cam only lt1 will never make over 315 through an auto...i put down 301(theyre dyno)...but i run 7.80's

 

o yeah...what gear did you dyno in?? 5th? or 4th?

 

try testing your knock sensor
http://shbox.com/1/4th_gen_tech2.html#knock_sensor

my LE3 383 was pulling 8 degrees of knock retard. once I eliminated it I gained 6 mph trap speeds.

 

I can't believe no one has asked this yet...

What kind of chassis dyno was it? Mustang dyno perhaps? Dynojet?

 

I was thinking the same thing^^^^...A Mustang dyno tends to hurt feelings...

--Alan

 

Just remember to keep your dyno slip in the glove box in case someone wants to go...or you take a trip to the track.

That way you don't really have to waste gas and rubber---just show'em your numbers.

 

Not by THAT much though.
I see it has a catback. Does it still have a catyletic converter?

 

sounds like the knock retard is the problem...when you got your tune did they desensative it? if not then maybe you should get the LT4 knock module

 

60 rwhp from knock retard? wouldn't the curve be a bit jagged, unless they smoothed the heck out of it?

 

A guy bought the LE heads and cam that was in a 385ci combo that made 445 rwhp. Today I was helping tune the car and it only made in the high 340 range with again the same heads and cam that made mid 400 range earlier. Now this is an auto so we don't expect it to dyo the same but we knew we were missing something.

The first thing we found was the airbox was overly restricting and by just unhooking the airbox we gained 18 hp. I'd like to try new 02's as that can also throw off peak power. Also the air quality this time of year isn't very good so take that into consideration.

He had the stock 48 mmTB and I'm going to try my spare 58 mm TB to see if that helps. Also I had an electric pump, a welded/ported LT4 intake and every other trick in the book including a year of tuning finding what the car wanted.

The vast majority of the time it's finding all the little stuff that adds up vs giant steps that somehow should magically appear.

Still not finished the car did gain 100rwhp @6000 rpm over the stock and that ain't all that bad at all. You'll find it but your gonna have to earn it first.

 

I feel your pain. Your #'s look almost exactly like mine and we have close the the same mods. But after I dynoed and drove the car home, it started knocking and I haven't driven it since. I'm hoping the problem with the shortblock is the reason I'm down on power. Even though that sucks that I'm probably replacing the shortblock.