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1987 Shelby GLHS #0958
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Jan, I meant on gemini's setup. It just wanders off somewhere.

gemini, there are two ports of obvious different size on the wastegate actuator, even on this 28 unit. The small one is supposed to go to a tee that goes one way to solenoid, and the other way to a nipple on the compressor outlet that your compressor housing doesn't even have. God only knows what's going on without looking at your system directly. They could be using manifold for reference but I don't think that port on the actuator supposed to see vacuum.
 

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87 CSX, 88 Shadow, 89 CSX
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Discussion Starter · #22 ·
Here are a few videos. I'm not sure if it will help or not. Here's one going up the mountain. You can see the psi lingers around 12. This is probably the better video.
Should boost be higher than that? My 87 is 15 or above continously.

And here's another one. Sorry I don't know why I kept putting my finger in the way.... that's incredibley annoying, I know.

So am I going crazy or is this wrong? I did read an article about the VNT25 that said max boost is 12 psi. Now I'm confused.

So the larger vnt28 would explain some of the extra lag but provide more boost so then shouldn't I see more than the 12 psi on the gauge? Even If 12 is the norm for VNT25?

A few things to add is that the seller included a bag of +20% injectors, a DOA computer from fwdperformance and some other items like spark plugs and what looks to be valve seals. Also he claimed in 1991 the block was replaced with a Mopar performance block. I also noticed the oil filter appears larger than it should be. Not sure if any of this info helps anything.

I'll check out those vacuum lines this evening and that T you mentioned.
 

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Those boost levels you are describing are not stock (15-16 lbs.), any boost level above 14.5 lbs.(2 Bar) requires a calibration and a 3 Bar Map Sensor.

If you want to know for sure take both down the 1320 and get actual real time numbers.
I am sure you will find that the 60' times are quicker with the VNT, top end MPH may not be.
Just be sure both vehicles are running under the same atmospheric conditions or your numbers will be skewed.

Without getting ahead of ourselves, later on when you are sure the VNT is running properly and All Basics have been verified OK, you can add an Adjustable Cam Sprocket which will allow you to advance/retard Cam Timing by a few degrees which can decrease low end quickness (60' times) and increase top end pull (or vise-versa) if that is what you are looking for.

All Stock, New, Running Well, Good Air (1993)
Quickest ET, 1993.jpg

Adjustable Cam Sprocket
Engine Compartment Right Side-2014.JPG
 

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The stock engine controller is going to keep boost levels at 12 lbs. of boost, if you want more boost you will need a calibrated controller and can run up to 14.5 lbs. of boost without major modifications, above that you will need to go to a 3 Bar Setup and add a Wideband A/F Gauge to be able to properly tune the system.

This is the VNT control system, along with the exhaust system that was designed with backpressure to prevent the turbo from over spooling, how much backpressure can be removed with the VNT 28?
VNT Solenoids 1.JPG
 

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87 CSX, 88 Shadow, 89 CSX
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Discussion Starter · #25 ·
Man am I ever confused . So basically from what I'm gathering is that the vnt is working fine? Weird. I swear this 87 csx pulls allot harder. Boosts at 15+ I'm wondering if it is actually the 87 that isn't quite normal. Possibly modified in some way? It appears stock tho. I've been comparing the 87 and 89 expecting the 89 vnt to out perform the 87. But the 87 has the upper hand. Or at least it feels that way. I think some tests may be in order. Don't let me go through all this just to find out I'm crazy lol.

According to the boost gauge on the 87 I am indeed boosting 15 and above and it feels it too.
Those boost levels you are describing are not stock (15-16 lbs.
 

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If you are boosting at 15 lbs. then the 87 is not normal, 14.5 is 2 Bar, the most the stock engine controller and Map can provide fuel for and that is still above factory controlled boost which was 7 (?) on a T-1 and 12 on the T-2 (Intercooled), T-3 (16 valve DOHC), T-4 (Intercooled VNT).

What turbo is on the 87?
What is it using for boost control?

Again, it is Springtime where the birds sing, the flowers bloom and men and women with loud, fast toys head to the track.
 

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Discussion Starter · #27 ·
As far as I knew this was an all stock setup. Bought it last year and there was no mention of any modifications. 69k miles on the car when I got it from GR Auto Galleries in Michigan. There IS a vacuum line disconnected tho. The car stalls out with it hooked up. It's the vacuum line that goes to the heater controls to change from the vent, floor, etc. The car won't run properly with this hose connected. Other than that the only thing I noticed was the aftermarket tachometer (stock tach doesn't work) Am I just clear crazy here and imagining all this? 🧐
 

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The tach being inop is common, usually related to cracked solder joints on the cluster PCB or oxidized terminals where the tach drive module mounts.

As far as the issue with the HVAC, there is probably a vacuum leak in the system.
Use a handheld vacuum pump, climb under the dash and inspect the line from underhood to the HVAC unit, the HVAC vacuum harness and the vacuum door mode actuators.
HVAC 85-87 Ex. L-Body.jpg
 

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Discussion Starter · #29 ·

The tach being inop is common, usually related to cracked solder joints on the cluster PCB or oxidized terminals where the tach drive module mounts.

As far as the issue with the HVAC, there is probably a vacuum leak in the system.
Use a handheld vacuum pump, climb under the dash and inspect the line from underhood to the HVAC unit, the HVAC vacuum harness and the vacuum door mode actuators.
View attachment 275299
But this shouldn't affect or explain the 15+ boost. So the conclusion here is that my VNT is working fine and my 87 is somehow modified to reach a 15 psi boost with a slightly higher spike. So now having figured all this out, if I wanted to accomplish the same results on my VNT I would need what? Better injectors and a tune and or computer?
 

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The article about the 87 CSX tells you how the car was built, what the car had stock and what Shelby Enterprises did to modify the vehicle.
From there you have to figure out what other modifications were done.

I am by no means an expert on modifications since my car is all stock, however I do know about what you need to have for the system to operate properly without issue. Other than the internals being larger and it flows more air I know nothing of the performance aspects of the VNT 28, I do know from first hand experience the VNT 25 is prone to overspool/overboost issues without the proper exhaust backpressure and boost control, same for the VNT 28???, I have no idea.

This is the least you can expect from continuous overboost.
Head Gasket (A) 5-21-10.JPG

If you stay at or below 14.5 lbs. of boost all of your stock components are fine and capable of providing the proper fuel.
Above that you will need Larger Injectors, AFPR, 3 Bar Map Sensor and a Calibration.
Regardless of what you do you need to install a Wideband A/F Gauge, verify Fuel Pressure is correct and the pump is capable of providing the fuel needed for additional boost, it needs to be able to provide additional fuel instantaneously.
I would also suggest a compression test and cylinder leakdown test to ensure the engine is capable of handling additional boost.



SPECS-Engine Compression.jpg


You can read more here...
(Turbo Database)

FWD Performance sells calibrated controllers for the VNT.
Any questions, give them a call.

Also found this, albeit 15 years old.
 

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Discussion Starter · #31 ·
Was reading through some of this and noticed this post --z

So my opinion is pick up the VNT 28, grab yourself a FWDP stage 3 VNT computer, some +20% injectors, cold air intake, and a 2.5" or 3" exhaust and have some fun, you'll like it-A LOT! ;)"

I think this is what the previous owner was going for. He says the car has the VNT28. (Tho I can't prove it really is]. He also gave me some 20% injectors and a computer controller thing from fwdperformance that he claims to be DOA (dead on arrival?).

But from my experience with this vnt28 so far, there are no gains at all from just the bolt on turbo alome.
 

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Discussion Starter · #32 ·
Can anyone verify this is actually a VNT28 and not the VNT25?
275584
275585
275586
 

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1987 Shelby GLHS #0958
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The tag on my NOS 25 says 465599-6. Don't know if that helps. Your compressor wheel appears to be significantly larger than mine.
 

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Discussion Starter · #34 ·
I wrote to fwdperformance and asked them about the injectors, doa computer and what else I needed to increase my gains and they never responded. I had also asked them to verify this was one of their vnt-28 turbos. It need to know if this is the 25 or 28 before I go doing the other upgrades.

My tag is similar to yours with the exception of the last digit after the hyphen
 

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And what is the last digit?
I googled Garrett Turbo 465599-6 and was taken here...

Try searching your number.
 

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Discussion Starter · #36 ·
Mine says 465599-5 so that tells me this would be the vnt25. The previous owner says he bought a package deal from fwdperformance that included a vnt28, computer and +25% injectors. He said the computer was doa. I have the injectors and computer in a box.

So either I misunderstood the last owner, he was mistaken or was ripped off by fwdperformance. Judging by that Google search, this would be a vnt25.
 

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Discussion Starter · #38 ·
So if understand all this correctly, I have a OES vnt25 installed? If the 465599 part number is a vnt25 like the other website suggests and the dash 5 means it's a replacement. Hmmm.
 

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None of the numbers matter. Your compressor housing has been machined and a larger wheel has been installed.
 

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Discussion Starter · #40 ·
None of the numbers matter. Your compressor housing has been machined and a larger wheel has been installed.
So it's the VNT28? Lol my brain hurts...
 
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