Hi Guys, I'm new and my profile isn't filed out yet but I will. Got a 84 vette. My mods last year were Xram, headers and 1.6 rrs and pretty happy with my dyno results then which were 207.7rwhp / 258 tq
Now this year I installed the Dart ss iron heads (173cc), 2040 cam, underdrive pulleys. The car screams now its a huge differance.
Ran the dyno today thinking I should pull at least 250 rwhp. Instead it ran 171 rwhp / 208 tq !! thats NOT right at all.
Dyno used is a Dyno Dynamics and there was a stang on there just before I got on. Is there different settings or something that are used for stangs that he could have forgotten to change? Something just isn't right with this. I can post the sheets if they help.

Two things in common between the two different pulls is that each time the car runs real rich until about 4500 then leans out. I know the leaning out in the high rpms is due to fuel pressure which runs 12 psi. But why does it run so rich? By the way no codes

Any thoughts and input would be appreciated, thanks

heres a vid of the pull http://s60.photobucket.com/albums/h5...t=100_0034.flv

 

I know that Dyno Dynamics will read quite abit lower that other dynos. Was your first dyno pull also on a Dyno Dynamics? If you can it is best to use the same dyno for comparisons.

 

Yes both times I ran it was the same dyno

 

Have you done any tuning for the mods you have added?

IF not that could explain the power drop. Any mods that add power require extensive retuning of these ECM's. A lot of guys on here couldn't even get their car to idle with a mild cam swap. IF you swaped heads and cam without tuning then I will garantee you that is the problem. A lot of times you can make less power but still feel good to the butt meter because of how the power comes in all at once.

 

No, I haven't tuned it. I do use the orginal ecm with dcs chip. I orginally used the hypertech chip on my first run last year. Maybe now since the bolt ons it does need a good tune. Like you say it feels great because now I've got the good flow just need to get the tuning right.
I have been looking at the ecm through dynamicefi with flash, any opinions or something else I may look into.
thanks

 

The EBL system is the shiznits and THE best option for major modifications, don't discount tuning the ECM you have. The equipment costs less than $150, I really wouldn't run your motor hard untill you get it tuned, you are most likely way lean and could hurt something prety quick.

 

The way it runs now according to the dyno
Lean at Idle
Rich until about 4500
After 4500 it starts to lean out again.
A simple FP adjustment can be made to accomdate over 5000, but I would think that it would then run even richer under 4500 than it already is.

How would I tune my ecm for under 150 bucks? You may not have looked at my profile but this is a 84 vette with the stock ecm. And if I can do that please explain... thanks

 

I've got a sticky at the top of the TBI forum titled "come in for a free tune" that goes through the process step by step. There is also a whole forum dedicated to DIY tuning on thirdgen. Do some research, you'll be surprised what you can do with the stock ECM.