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Discussion Starter #1 (Edited)
Big Scott took another vacation week to work on GB. The plan was to iron out some issues, install the new upper pulley and belt, and try get her back to the dyno. She didn't get to the rollers, but it was a week well spent.

One of the issues was an A/C leak, the system wouldn't hold a charge. Another of the issues was a PS leak at the steering rack. Since Aric had a brand new A/C bleed down tester and a couple of new lifts installed, and room for GB, Scott took her up to his shop (Injected Engineering) in Kennesaw. That's the same shop where the engine was pulled, shipped back to Michigan and replaced a couple of months ago, and Aric is the guy who has been working on GB's tune, and providing lots of technical advise along the way.

The new pulley and belt were up there, and since the blower and plumbing needed to come apart to check the A/C, and replace the upper pulley and belt, Scott made the commute to Kennesaw every day.

The A/C leak turned out to be an O-ring. There was also a hose that needed replacing, it's obsolete from Ford, but NAPA had it.

The PS leak wasn't so simple. Well the problem was not complicated, but the solution was a PIA. The threads where the PS line connected up in the new rack we got from Ford were bad. The best fix was to replace the rack with another new rack. So the steering rack had to come down - not an easy job.

The new pulley and belt are on and so far so good, but we really won't know whether the belt slip issue is resolved until we do a WOT pull on the dyno and see what happens.

The new fuel pump & fuel delivery system seems to be working like a charm, but that also needs to be tested at WOT. We might have got GB to the dyno by the end of the week, but due to prior commitments, Aric wasn't available on Friday or Saturday. Consequently, Scott turned his attention to the cabin, and put some quality time installing the heat/sound insulation (Dyna Pad) and the new (black) carpet.

Scott left the car up at Injected so that Aric can drive her around and fine tune her for street driveability. There is also a speedometer calibration issue. For some reason when we put a purple speedo gear for 373's in the '03 GT 4RW70 J built, the speedometer is inaccurate, which is screwing up the shift points.

So after the Speedo issue is resolved, GB can go back to the rollers and assuming the fuel and belt slip issues are also resolved we can get a WOT tune and some preliminary numbers.

What's left to do is to complete the cabin - carpet and gauges. Scott will drive her around for 500 or so miles looking for, and destroying any gremlins that might be lurking around. Then, we'll probably re-tune her, maybe get a moneyshot (race fuel?), and then (drum roll), I'll bring her home to Florida to see how the charge temps are with 90+ ambient temps.

There is some touch up painting to be done on the bumper, and the hole in the hood to deal with, but I may do all that here in Florida. I'm anxious to get her down here so I can do some time trials at Moroso before SSHS.

Here are some vacation pix from Scott:

RACK IT


A/C HOOKUP


Z PARTZ




APART




Z NEW






Z CABIN






Z HOLE



more will be revealed...

:cool:

-mike
 

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Discussion Starter #3 (Edited)
do you want to trade the 3.1" pulley for a 2.8"? how much boost do you get with that pulley if you dont mind me askin

zack
We tried the Vortech 2.87" pulley, and the belt slipped like crazy at 4700rpm. The belt we have on her now is a RR pulley, something under 3.00". We have a backup 3.1" RR pulley to try with an oversized crank pulley, if the set up we have on her now still slips. I may keep the 3.1" for the future, or Aric may use it on something else. I dunno.

With the 2.87 Vortech pulley the digital boost gauge just got into the positive numbers (maybe 6 psi or so) when we had to shut her down at 4700 rpm due to belt slip and fuel starvation. So at this point we really don't know what "boost" we will get.

But, as you probably know, boost readings on a gauge are pretty much worthless as a measure of anything but back-pressure. However, as a rule, lots of folks use "boost" to measure expected power from a blower set-up. The manufacturers use it to sell the blower kits - "the 6psi kit" and "the 12psi kit" .. that assumes that the "kit" will be installed on identical set-ups as the test car, I guess. Folks say, "don't run more that 6psi on stock internals." It's a good rule of thumb, but does not take into account other important factors. We shut GB down at 4700 rpm because the fuel pressure had dropped to 21psi and the belt was slipping (smoking). The boost gauge may have been at 6psi, but we were pulling 439rwhp. Considering the engine was fuel starved, that's quite a bit of power at that "boost", and that's a function of low ACTs and an efficient intake/exhaust system. Generally speaking 439rwhp is probably more power than you'd want to put to stock internals for very long, even if the gauge is reading 6psi.

Instead of boost numbers what we really need to know is how many cc's of air are flowing through system. That would tell us something useful.

In lieu of knowing that number, I guess the next best measurement is the spin rate of the blower impellers. The T-Trim's maximum efficient spin rate is 52,000rpm. The maximum spin rate is 55,000. At 52,000 rpm the T-Trim is pushing the most air it can push, the most efficiently, in terms of power needed to turn the blower and heat developed (both of which increase as the air compresses more).

The engine Jim built for GB is safe to spin up to around 8,000 rpm, but the power curve, where I want to be, of the heads/cams combination is around 7,000 rpm, at least that's the plan.

The upper pulley we're using now (or the 3.1" upper/oversize crank pulley combo), should give us 52,000 blower rpm at right around 7,000 engine rpm. That's what we're looking to get - we want everything to max out at the same rpm, with a little cushion.

So if all the planets line up and the belt doesn't slip at 7,000 engine rpm, we should get the maximum air-flow available from the T-Trim through the intake.

ONce the blower is spinning at it's max, what the boost number on the gauge will be depends on the efficiency of the intake/cams/heads/exhaust - the freer the airflow, the lower the boost numbers, but also the charged air temperatures are lower (cooler air) and there is more power. If the intake/exhaust system is corked, the boost number goes up, but the actual amount of air available goes down, the ACTs go up, and the power goes down.

That all being said (Blower 101) ;) .. someone who is very familiar with the heads/cams combination I've got, and has seen the T-Trim maximum air output in action many time (and knows a lot of math) has told me that at 52,000 blower rpm, the max boost would be 18 - 20 psi on the gauge.

If the gauge shows lower "boost" than that estimate at 7,000 rpm, and the ACTs stay as relatively low as they have been so far, I will not be disappointed. It means, that either I'm not getting the full 52,000 blower rpm, or the air flow is very efficient

I will, of course post up as much actual data as I get from the dyno and Scott's Info Center. All the numbers will be "real" time numbers.

By the way, there is formula you can use to get the blower rpm given known crank and blower pulley sizes.

Who was it that said math has nothing to do with cars??

:tongue:

-mike
 

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There is also a speedometer calibration issue. For some reason when we put a purple speedo gear for 373's in the '03 GT 4RW70 J built, the speedometer is inaccurate, which is screwing up the shift points.

-mike
does the output shaft have 7 or 8 splines?

i think the later ones required the "white" gear for 3.73, purple for stock 3.27 or screw it all and go speedcal
 

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Dumb question but where did you get the carpet and how is the fit?

Russ
 

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ah i have a RR 2.9" pulley that i am unsure if i want to run yet. and also a vortech 3.25 pulley. all of them are 6 rib. Also i only have a S trim. so i may just take a plethora of pulleys with me to the dyno! :)

p.s.. oh where did you get the oversized crank pulley at?
 

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Discussion Starter #7
Dumb question but where did you get the carpet ...

Russ
Darned if I remember ... too many orders/invoices over too much time for this tired old brain.

Scott probably knows, though ...

and how is the fit?
We'll have to hear from the guy that's putting it in .. he said something about "wrestling" ..... but didn't give me the details...

-mike
 

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Discussion Starter #8
ah i have a RR 2.9" pulley that i am unsure if i want to run yet. and also a vortech 3.25 pulley. all of them are 6 rib. Also i only have a S trim. so i may just take a plethora of pulleys with me to the dyno!
Probably a good idea ...

p.s.. oh where did you get the oversized crank pulley at?
Aric had one laying around his shop, doing nothing.. It happens to be an 8 rib, I'm not sure who made it.

Kenne Bell makes oversize crank pulleys for the Cobra.

-mike
 

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Mike...I must admit, I have always loved looking at the buildups on your car. It's hard to believe it's almost done?

Anyways, it looks like you'll enjoy it..and too bad I don't have the $$$$ or time to do something like that.

-Corey
 

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Mike,

Ditto on loving to read about the car.

I think that you and Scott are going to need to sit down one day and write a sticky thread on the WHOLE build-up of the car from start to finish.

Good luck with the tune!

-Josh
 
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