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Working VNT??

5K views 54 replies 7 participants last post by  gemini9 
#1 ·
Hello

Some of you may have already read that I just bought a 1989 CSX-VNT from Washington state and had it delivered here. The seller says the VNT is in working order and he's a cool guy and all but I just want to make sure it's working alright as it seems a bit laggy. The seller did state the turbo was replaced with a VNT-28 rebuild from fwdperformance.com as well as some steel braided lines. When driving the car, it feels like there is lag present and I don't really feel the boost kick in until the higher RPMs. As I understand with the VNT, the boost should come on almost immediately. Maybe I'm just overthinking all of this and worrying for nothing. Also in the higher gears, such as 4th, the boost gauge reads around 10 or 12 instead of the max of 14 or 15.

Is there a way I can be sure there is a working VNT system in the car? I just want to make sure everything is as it should be.

There are 40k miles on the car, the title said 0 with an E status (most likely because of the vehicle age). Seller said that in 1991, the original owner threw a rod and the block was replaced with a mopar performance short block.
 
#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
 
#35 ·
And what is the last digit?
I googled Garrett Turbo 465599-6 and was taken here...

Try searching your number.
 
#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.
 
#41 · (Edited)
Ok so fwdperformance got back in touch with me and said it is a vnt28 machined into the vnt25 housing.

Now that this is verified, how can I increase my gains? Right now this vnt28feels a bit sluggish.

Everything is stock other than the vnt28. I do know that in 1991 the block was replaced by a Mopar performance short hole (whatever that is).

This vnt28 was put on in 2016.

I have in a box in the trunk +20% injectors, freebar map sensor, a doa stage 3 module computer. The seller said the set up didn't run because the computer was doa. He said the original injectors were cleaned and put back in and "put the shelby computer in it"

There is a totally random code 31 for a purge solenoid. The solenoid was replaced and wiring was checked and everything seems to function like it's supposed to.

I know thats allot to read through but hopefully that helps. So... what do I need to do here to get more boost here?
 
#43 ·
Oh. LOL. Yep. I got back from a long trip just now. Haven't checked in in a bit.

I had a performance VNT SBEC for my Lebaron coupe that was also dead. I'm beginning to think that SBECs do not like to be socketed. If your SBEC was swapped back to stock then you need to either get a working SBEC with a tune for VNT 28, or put a VNT 25 back in it. You most likely won't achieve stock horsepower levels and could be causing detonation running the engine lean in the current configuration.
 
#44 ·
Oh. LOL. Yep. I got back from a long trip just now. Haven't checked in in a bit.

I had a performance VNT SBEC for my Lebaron coupe that was also dead. I'm beginning to think that SBECs do not like to be socketed. If your SBEC was swapped back to stock then you need to either get a working SBEC with a tune for VNT 28, or put a VNT 25 back in it. You most likely won't achieve stock horsepower levels and could be causing detonation running the engine lean in the current configuration.
I'll look around and see if I can find a stage 3 .module . I'll check back in with fwdperformance and see if maybe someone has one for sale here in the forums. If I canr find a computer I'll pick up a vnt25

So if I can get hold of a computer, all I'll really have to do then is install the injectors and things shoild be ok?.
 
#46 ·
Yes. If the car runs it may be fully functional. I doubt they would say it was toast without a reason though. A lot of guys disconnect the hose between the ECM and airbox and those components need that airflow to survive. Chrysler engineers didn't set it up that way for no reason. There are heat sinks that pull heat away from the voltage regulator components and coil driver components.
 
#49 · (Edited)
I always considered the the VNT more a technical novelty, no disrespect intended.

Heavy T-II Daytona's were a bit if a challenge to get rolling smoothly without stalling.

Once rolling, the T-II no doubt outperformed the VNT in a drag or any race.

As mentioned, the VNT advantage was it came off the line briskly, no stall.

Back around 1990 a local had a red 89-90 Shadow T-IV competition.

By chance, I pulled beside side him in a stock red 1985 Omni GLH Turbo.

Glances and smiles were exchanged and we played for awhile.

No standing starts but rolls from about 5 mph for about 1/8 mile.

We floored them about the same time and he moved up smartly.

Top of 2nd gear I was beside him then began pulling ahead.

We raced about 1/8 mile and made several runs in 2nd, 3rd, 4th.

Omni always by a little and the gap continually opened slightly.

Its understandable many get a regular T-II Garrett swapped in.

Thanks
Randy
 
#50 ·
I wouldn't mind putting in a stock VNT25. Either way, VNT25 or vnt28 with the injectors and ecu, I'm a happy guy. I'm just glad to have the car. The car is clean and the motor is clean. It's a show car. But I'd like to do either or. Vnt25 or finish up the 28 setup. The latter would be cheaper and easier since all I really need most likely is the ecu since the turbo is already on the car. I'd have to pay a mechanic to put the Vnt25 back on plus I would have to find and buy the turbo.
 
#55 ·
I got in touch with fwdperformance about sending it in to them but never heard anything back from them. Car is stored away now until summer so I'll try again in a few months. I did find some pt cruiser valves in a parts box in the trunk tho!
 
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