LT1 Based Engine Tech 1993-1997 LT1/LT4 Engine Related

dyno'd the firebird

Old Nov 20, 2004 | 09:59 AM
  #1  
Zigroid's Avatar
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dyno'd the firebird

well, I have some big problems. It put down 234rwhp and 275rwtq with the mods in sig. I'm pretty sure it was a dynojet dyno.
A/F ratio started at 14.8 at 3400 rpm and fell down to 12 by 5600 rpm.
from 4200-5500 rpm there is no reading at all, they said that the spark was so erratic that it wouldn't give a reading. The little bit it recorded was also "wavey"
overall the car is running very bad. The speed shop owner suggesting upgrading to an MSD ignition, but I don't know if thats the problem or not.
I just installed new plugs and wires less than 6 months ago.
I'll get the graph on the internet later tonight.

what could be wrong?
Old Nov 20, 2004 | 01:04 PM
  #2  
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Re: dyno'd the firebird

The missing part of the dyno graph is because they had a weak tach signal lead. They should have gone to the secondary pick up point and ran it again for a reliable graph.

If it's an ignition issue, you've potentially only eliminated two possibilities. And I don't believe throwing an MSD box on there now is going to help anything.
Old Nov 20, 2004 | 03:01 PM
  #3  
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Re: dyno'd the firebird

Try looking at the OptiSpark & put some Lucas Injector cleaner in your gas tank. The MSD box will only make things worst.
Old Nov 20, 2004 | 03:25 PM
  #4  
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Re: dyno'd the firebird

alright, some more stuff since I was in a bit of a rush when I wrote the initial post:
It was a mustang dyno day (not the mustang dyno) so I was the only GM there and I also had the lowest hp car... that right there made me very embarassed and mad.

The guy operating the computer said it was an ignition issue and that the spark they were picking up was so erratic that they couldn't make anything of it. I have no idea how this would affect things so I didn't even question him even though it didn't sound right. He also said that I should get all MSD ignition components. I remembered people on here refering to MSD as "may suddenly die" so I didn't think that that would solve the problems.

I didn't drive the car during the dyno, I stood behind it. I had never heard the car from the outside before and I didn't know how to operate an automatic on the dyno.

Above 5000 rpm it poured out black smoke, some blue smoke and throughout the entire RPM band there was some light smoke coming out. Over 5000 rpm the engine was getting very choppy and sounded like it was breaking up.

I just put new taylor spiro pro over the valve cover plug wires on and new spark plugs less than 6,000 miles ago. I sure hope it isn't the opti although I believe this is the original 122,000 mile opti. I'm sticking in a new 383 with a vented opti and i'm not reusing too much from this engine, so it wouldn't be the end of the world.

there was a guy with a new mach 1 there that put down 250ish rwhp, he said it was down about 20 since the last time, perhaps there was some dyno error in there somehow as well? Not one guy hit over 275. There was a 5.0 cobra there that had a new cam and full exhaust, air intake, other stuff. He laid down 271rwhp I believe.

Heres the dyno graph:
http://home.comcast.net/~zigroid/firebirddyno.jpg
You can see the huge gap. It was only 2 runs, one run it stopped at 4200, the other run started and stopped around 5600. I'm also sure if there was some sort of graph connecting the two that my peak hp number would be a bit higher.

Oh well, 13.8@102 mph with only 234rwhp! wonder what she would do with no problems!?
Old Nov 20, 2004 | 04:39 PM
  #5  
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Re: dyno'd the firebird

My bird on a Mustang dyno did; Stock exhaust manifolds = 262, after headers = 282.

Black smoke is unburned fuel, blue smoke is oil. Go to Jason Cromer, a new GM opti is $229. + shipping & don't forget the water pump gaskets. Buy a Chilton book at Discount Auto for the "how to" it's number 28284. Or go to some of the web sites here.
Old Nov 20, 2004 | 08:42 PM
  #6  
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Re: dyno'd the firebird

i think u need to start looking at a new opti sparkyou should be putting down 270+
Old Nov 20, 2004 | 10:23 PM
  #7  
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Re: dyno'd the firebird

if it ends up being an opti, im just going to drive it as is and wait till the new engine gets dropped in, which will have a newer vented opti.
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