I posted this over on DTW a few weeks back and got no really clear idea's on what to do.

On my latest dyno my A/F was topping out over 14 at 6100rpm, not good at all. Though it's probably a little better then that, I want to get it back into the 12.5-13.0 area.

The only way I know of forsure to fix the problem is to get an smt-6 and change the fuel mapping, but that is an expensive route.

I just put in the IAT resistor mod, and will dyno that on Saturday to see if it richens me up any. People claim to get 2.5% more fuel at wot with it but will 2.5% be enough?

What else can I do, try putting in an 04 fuel pump. A fuel regulator, an inline fuel pump, bigger injectors have all been mentioned to me? Which one or combo of those would be the fix?


Here's the dyno run. The red is the new run.

 

Well.... if I had your problem... I think the first thing I would do is to try to find a Autotap somewhere... ( least expensive option that I know of for datalogging, however limited it is... and I know of nothing else out there that will work ) and I would check the duty cycle on the injectors... IF the duty cycle is below 100% then you might figure it is not pushing enough fuel and then You may go the 04 fuel pump route.... if it is over 100% then you may do the fuel pump first and get an effectively larger injector but may still need the larger injectors if you still see a 100% or close to it duty cycle. I really doubt that the IAT mod will supply enough additional fuel to fix your problem but I may be wrong...
but whatever the problem I would do the fuel pump first..... ( if the IAT mod fails )

keep us posted!
TJ

 

The problem with using the 04/05 fuel pump or larger(6.1) injectors is that there is no way to regulate them. They will give you more fuel at WOT but you don't know if it will be to much or not enough and you will not be able to lean or richen them up. Also, the 6.1 injectors are like $48 a peice which would be about $400 and the fuel pump is about $180.

The smt-6 is $400 and can be used in conjuction with the injectors/fuel pump later if you have to much or not enough fuel.

 

Yah, I guess I need to figure out what the duty cycle is on the injectors first, though I would think they are probably still in the clear as guys running 370rwhp + seem to be maxing those out.

That's the problem with all these fixes outside of the smt-6, all we can do is move the a/f line up or down. The idea of the smt-6 gets more appealing, but I don't think I have enough knowlage to create my own fuel maps. That's where it would get expencive, running it on a dyno for the better part of a day getting someone to map it all out. And I guess I would need a labtop, though I could drag one of my old machines out into the garage to mess with it once it's been setup.

Anyone have any experience with installing and creating a fuel map with it?

 

I agree with TJ and SRT, the duty cycle at WOT will be the best indicator.
On the fuel maps, I think there are a few NA folks running the SMT, worst case you can get a copy for a decent starting point. Down side, without Autotap you really should add a wideband to the mix for optimum tuning, although you should be able to recover the extra money quickly since dyno time will not be required!

 

Just for s**ts and grins. Try pulling the superchips out of the picture.

 

Aye I actually put it back on the 87 tune... which is stock except the rev/speed limiter is still in. Been running 94 oct gas to make sure it doesn't ping it's self to death. Saturday night I'll post results from the dyno. Gonna see if I can con my local speed shop to install/tune a smt-6 if they have some experience with them. Hopefully so, these guys do a lot of custom turbos and such and would need to do some custom tuning for those.

 

Went back to the dyno today, looks like the power wire I ordered from Air Ram (like the resistor mod for the IAT except its a variable resistor) did the truck. My A/F is back down in the 12.8 to 13.3 range, right where I want it to be for a N/A hemi. Power remained the same, 315-320 range, but with a healthy a/f I can safely stomp on it again.

Next friday I am off to the track.