Tuning Issue--look inside

[techieman33]

So the problem is that RubySlow, and I's mountys are turtles off the line, but once in the higher rpm's, take off, especially when already moving and the trans kicks down. First off are there any more of you 302 guys out there with a similar problem? Everyone says that our motors love back pressure and both Ruby and I have bigger exhaust systems than stock, also my problem got more noticeable after Jon and I put my TM headers on.

Now to my idea, get another 302 throttle body, 65mm, my exhaust is 2.5" which is 64mm, so it's a good size match. and drill out some holes, or maybe cut half of the butterfly off. Then put attach it to the exhaust pipe, and wire it in to the gas pedal. So at idle, and lower rpm's it would be more restrictive, but at WOT, it would open up and flow like it does now. Could this work? Am I crazy?

 

[boominXplorer]

Its the headers, thats why I havent switched yet over yet. I am running FMS headers with true duals and I can scoot off the line.

I am sure the 4:88s have something to do with it also.

Are you still AWD? The switch to a 4x4 TC made a huge differance for me

 

[techieman33]

I'm still AWD, I plan on going 4x4 this spring, Ruby doesn't have headers, that's why I think they aren't the full problem.

 

[jimbo74]

so you are essentially making an exhuast brake, personally i would not trust it.. way too much to go wrong.....

 

[techieman33]

so you are essentially making an exhuast brake, personally i would not trust it.. way too much to go wrong.....

I'm just throwing the idea out there, I just know that I really want to get some bottom end back.

 

[Dan Whitaker]

My exhaust is all stock and is a dog from take off. I have 31x10.5 with 3.73 gears. The 31" tires account for a little of it but not that much.

I'm with Boomer. the AWD is killing the low end. I'm hunting for a 4406 as well.

 

[jimbo74]

throw in some 4.56s....

what happens if your ehuast brake fails at speed? or clsoes like a throttle body?

 

[techieman33]

what happens if your ehuast brake fails at speed? or clsoes like a throttle body?

That's why it would have holes in it, there probably wouldn't be much of the butterfly left, just enough to offer a little resistance.

 

[MountaineerGreen]

They make electric exhaust cutouts that will do something similar and be more durable in the exhaust system. The best price I found and quality construction was this: http://www.mccordcg.com/mpp/mpp.htm

I have been thinking of adding two of these to my exhaust, I would do it like this: No secondary cats, two 18" glass packs, two exhaust cutouts with turndowns, into my Magnaflow dual in, single out muffler, a 2.5" tail pipe all the way out.

With my current exhaust, headers, 4406, 4.10's and 33's it actually moves pretty good. If I could find some spare wheels, I'd mount up a set of stock size tires and go to the local 1/8th mile drag strip

 

[Turdle]

No, I think your "issue" is from something else--

it feels like a switch is turned on at 20mph--then the truck starts pulling.

it has to be something in the software-I'm curious when the timing advance kicks in--this is what it actually feels like is happenening---

Can you watch the timing curve with the xcal?

 

[techieman33]

Evan, I'm not sure if that could do what I want it to do, which is close the exhaust down at lower rpm's and open it up at higher rpm's. it would be open or closed. They say that you can control how far it opens by how long you hold the switch, which might work for me, but would be a pain in the ass since I would have to worry about controlling it as I was going down the road/track, that's why I was thinking about attaching it to the throttle cable, then I wouldn't even have to think about it.

 

[techieman33]

No, I think your "issue" is from something else--

it feels like a switch is turned on at 20mph--then the truck starts pulling.

it has to be something in the software-I'm curious when the timing advance kicks in--this is what it actually feels like is happenening---

Can you watch the timing curve with the xcal?

I'm going to do some data logging later this morning after my borther wakes up ( I need his laptop to do it)

 

[MountaineerGreen]

Yeah, I could see how it would be hard to control, but I'm worried about how a TB would hold up in the exhaust system. The cable actuated butterfly may work, it'd be difficult to rig up to work correctly and linearly with the throttle.

Have you considered just putting a dual in, single out muffler?

 

[Turdle]

I do know a TB needs disassembled for powdercoating--there are some bearings and o ring seals--

I think the exhaust will cook it--

 

[techieman33]

ok, i'm ready to datalog what parameters should I log?

 

[Turdle]

I think this is James' territory--

But I want to see the ignition timing curve--relative to speed--

 

[techieman33]

would that be the same as spark advance?

 

[Turdle]

would that be the same as spark advance?

Yeah-
how many can be logged?

compare speed-calculated load-and spark advance--let's see if something changes dramatically at 20 mph (something is-I have felt it when I rode in your truck)

ohhhh--check the throttle pull--

key on engine off--floor it and read TPS ----

then-go pull the throttle to max by hand--
compare the two readings--

 

[techieman33]

You can log a lot of things at once, I've logged over 15 at once. The battery on the laptop is almost dead, I have to go inside for a bit and let it charge. the red line is 20mph

 

[CDW6212R]

Let me know what becomes of this, all Lincoln Mark VII's are slow getting to 20mph or so. I'm hoping for it to be the timing also.