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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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Discussion Starter · #301 ·
Ok! I got back from visitng David Dalke this afternoon and we've settled on getting those longtubes installed at the end of next month. He's going to fab up an EGR bung and replace the ball-and-socket end of the headers with a 3-bolt flange as well. He was pleasantly surprised when he found out the heads (and exhaust studs) were "recently" installed by me, 8 years ago. He was NOT looking forward to the potential of having seized studs before that. :)

We're going to dyno it before and after to see what the difference is as well. It'll also be good to see fresh numbers after some years of tweaking the tune - and with the new trans and TC from Circle D and Darrin. This means I need to spend some extra $$$ and start putting 93 back into it, and getting that tune re-loaded! I've been on the 87 tune for so many years now, it'll take me a few to figure out what tweaks I've made to the tune that don't relate to timing since I last ran it on 93...
 

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I've seen the nut frozen to the stud, but not the stud to the block.
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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Discussion Starter · #303 ·
Left the car with David this afternoon. We did 3 pulls to "pre" measure it before the headers go on, but for some reason the TC is unlocking at 80 MPH and neither he nor I could immediately tell why given a 15-minute glance through the tune in Advantage. It is definitely commanding it to unlock though, given the datalogs. He's going to look through the MTF in his software to see if there might be some hidden settings related to torque limits that needs to be changed.

On the botched pulls though I did see it made it to 260 RWTQ around 4200 RPM before the TC unlocked.
 

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Seems to me there's a value file for that; specifically for locking it on the dyno.
Also, don't forget the 127.5mph upshift file.
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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Discussion Starter · #305 ·
Oh, I loaded that some years ago. Though I have never tested it. :)
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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Discussion Starter · #306 ·
The car is ready for me to pick up this coming weekend!

We did a few pulls on the dyno before it went under the knife and will do 3 more before I head home. A new problem is that it's unlocking the TC at 80 MPH in 3rd, which I have yet to find a reason for in the tune. Nothing that is an obvious cause appears to have changed from when I did the 1/4 passes a few years ago (it didn't do it then) and David briefly looked over my MTF in Advantage and it wasn't what he thought it was either. So my numbers will probably be coming from 2nd gear pull comparisons and/or extrapolations of what it does in 3rd if it unlocks again.

Anyone want to take a[n educated] guess on what my net gains from going from Preston's ported stockers to GM's longtubes will be? I'm hoping for a 20 HP gain...
 

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I’m going to guess 18hp and 32ft-lbs maximum gain.
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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Discussion Starter · #309 ·
Well, here we have it! No fancy undercar photos aside from this one, which will just have to do for now.

Hey @guitar maestro - recognize those? :p



Both David and I were hoping for a relatively easy install of guitar maestro's headers, but given the unique nature of the headers (being customized by him to clear the steering shaft without modding it - which btw, worked perfectly) neither he nor I could predict what obstacles would be encountered.

Me, being a stubborn completionist, wanted to keep EGR for the slight improvement in fuel efficiency it offered. The headers as they were had no EGR bung, so I had David add one. Of note, he told me this was the single most difficult thing he's had to do for exhaust on an MN12 due to the tight spaces afforded by the engine being in the car during welding - not sure if I should be proud of that or not! :eek::ROFLMAO:

With the engine still in the car he had to modify both the headers and the EGR tube to make it work, which added on quite a bit of extra time and complexity. He had to extend the EGR tube because as it was, it intersected with the headers in a place a bung couldn't be added. The ball-and-socket fittings on the headers were also deformed so he cut them off and welded on a traditional flange. I made the decision to keep the cats (yes, most unusual with headers, especially long tubes), despite their new position in an area that will take considerably longer to reach temperature. This I did if only because I really hate the smell of catless cars. No codes thrown, in the 120 miles or so it's been driven so far.

Anyway...

The paint GM used on the headers sure didn't fail to put on a show! As the headers heated up, gobs and gobs of smoke started pouring off them as the paint was cooked into place. And then we were in for smoke show 2.0 during the first pull as it cooked the headers properly, all the way to the end. :)

I didn't take any photos or videos of the pulls, but I snapped a couple photos of the graphs owing to them not being able to print them at the shop. We dyno'd the car mostly to try and see the difference before/after but unfortunately, we didn't get any solid pulls before as the TC was unlocking at 80-82 MPH. Today it stayed locked for the first pull, then unlocked for the 2nd. He's sending me a value file with the scalar he thinks is causing it; I don't have access to it in my copy of Advantage.

I also talked to David a bit about his dyno numbers and how I could "compare" them to my DynoJet pulls from back in 2013. He gave me a complicated answer.... but basically said there isn't a way to know for sure. Newer DynoJets will compare much more apples-to-apples to the other dynos out there (inc. the Mustang dynos) but the one I ran on 8 years ago was definitely the older style that was "nicer" to numbers, so I'm going to use the old formula for a Dynojet reading about 8% higher than a properly set Mustang dyno. It's the lowest figure to approximate and compare (some as high as 12% but I care less about bragging rights and more about measuring gains).

SO.... all that said, the best numbers I saw were 265 RWTQ at 4200 RPM and 255 RWHP (yet again) at 5200 on the first pull, when he let off at 5200. To our delight the TC remained locked for that pull. I had him do a 2nd pull out past 6000 to see the curves, but the TC unlocked again and it peaked this time at 243 at 5600, staying flat to 5800.

We were looking at comparisons of the "unlocked" runs and the unlocked TC transmits a solid 10% less WHP compared to it being locked. We looked at the before pull to 5400, with the TC unlocked, and compared it to the after pull to 6000, with the TC unlocked. Before the TC unlocked at around 4000, there was a pretty consistent 5-7 WHP gain after the headers went on. Higher up it was more apparent, but difficult to measure due to the before pull ending at 5400. Extrapolating the curves and guessing, it looks like a difference of about 15 peak WHP from before the headers, to after. Doing the same extrapolation of the shape/position of the curves to estimate what a fully locked run would have done (bench racing, lol), it looks like it would probably have peaked around 260 WHP on the 6000 RPM run, or ~280-285 WHP on the Dynojet I ran on in 2013 (using the 8% figure). So that's a 25 WHP gain due to polishing up my "rough cut" tune over the last 8 years and installing the longtubes. 15-20 WHP from the headers and I somehow found 5-10 RWHP through the tune by perfecting my mixture and dialing in the spark. Given Nick McKinney's statements that the H/C/I combo I went with was a proven 300 WHP combo on Mustangs (assuming a Dynojet measurement), I figure 280 is a pretty close estimate given the extra losses due to IRS and the 4R70W.

As I left, David mentioned he was going to be putting Brian Herron's Mark VIII - with two PCMs and 2 MAFs - under the microscope next week. I told him I didn't envy him. :)

Here are the 3 photos of the pulls/comparisons I took.



This first one shows the last pull, the one to about 6100, where the converter unlocked at about 4300, as well as the best "before" pull to 5400 with the same erroneous unlock. Modest yet consistent gains up through about 4000, then widening more substantially after the curve resumes.




This graph shows the same 6100 RPM pull at the end of the day (that unlocked) next to the previous to 5400 that did not unlock. There's no argument that an unlocked converter transmits less power to the wheels looking at that graph! Of importance for my case is the ~20 HP loss between locked and unlocked, from which I estimate my RWHP figure.



This final comparison shows the "before" and "after" pulls where it's really easy to see the consistent 5-7 HP gains down low. Trying to look through the mess of the TC unlocking, it's the best guess of David's and mine that the longtubes by themselves were worth at about 15 RWHP. He suggested I consider adding more timing to compensate for the cooler combustion afforded by the new headers, which I may yet do... in the spring. :)

Now, as for the rest of you... I legitimately await for you to tell me where my logic has failed and how my conclusions are flawed... :whistle:
 

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1994 Cougar XR7 DOHC/5-Speed
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I always wondered if header paint self cured after enough time, guess not lol Did you go through the whole bake in process with them? Speaking of paint I hate when shops overspray onto the underbody, big little peeve of mine.

15 horsepower is about what I expected with MACs, that’s very consistent with what I’ve seen posted up on Mustangs with them. I like the flanges you used, my 4V MACs need them added to the collectors which has been part of my demotivation from using them(also need blasting, touch ups of any deep pits that might blow through from the blasting, and bungs ugh). It would have probably been easier to have used a SN95 EGR tube that feeds off the driver side header, obviously Oscar eliminated the tube/bung for it when he modified them but the factory tube would have likely cleared and probably wouldn’t have been such a tight squeeze for Dave to get in there
 

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1997 Thunderbird 4.6, 1998 Mark VIII LSC
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Discussion Starter · #311 ·
Nothing special, we just let the car warm up at idle and they started smoking on their own. After that stopped we ran the car up a little and let them smoke/clear up some more before doing the first pull.

Oh well, 96-97 EGR tubes are rare enough nowadays but now I have the rarest one of them all! :ROFLMAO:
 

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You can set the paint without an oven; you hang them up vertically and hit the bottom with a torch until it stops smoking or the glass melts. :)
 
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