VNT turbo on a non-VNT car?

[Arro]

Ok, I asked about this on another site, but that was before I found you guys.... apprently all the old knowledge base hangs out here. So here I am.

If I wanted to control this mechanically on a car not equipped with a VNT computer, how would I do it? I tried to draw up something to better understand how these things work:

http://img.photobucket.com/albums/v216/arrospeed/Neon/vnt_simple_controller_rev_3.jpg

And since I hear that these turbos sometimes suffer from massive spike and even boost creep, I thought about a setup that incorporated an external wastegate:

http://img.photobucket.com/albums/v216/arrospeed/Neon/vnt_simple_controller_rev_3_w_overb.jpg

What I THINK it does: The way I have it in the last two drawings, the moment you put the engine under load, it will spool up the turbocharger (which will have vanes closed because of the spring in the can). As the boost rises, it reaches the manual boost controller (not pictured, just shown as two hose ends leading to it), until it defeats it. Say it is set to 12 psi. Once it reaches 12 psi, it defeats the MBC, and sends that boost signal to the boost side of the actuator can. Since it's 12 psi, it defeats the spring (which I imagine is somewhere around 5-7 psi). It pushes open the vanes, and the turbine stops spinning as fast, until it reaches the point where the boost is barely regulated by the MBC. Thus holding boost at 12 psi.

Without an MBC, it will regulate at the actuator can's guestimated 7 psi.

Under hard accelleration, it still may want to creep beyond that, or on initial boost, it may hit so hard that it overboosts a bit past the maximum set point. Use of an external wastegate as shown in the very last diagram will quickly illeviate exhaust backpressure and prevent overboost or creep on this VNT setup.

Someone please buy me a clue here, or am I on the right track?

Also as a side question, the spring in the actuator, which side is it on? The side with the smaller barb (boost side) or the larger barb (vac side)?

Thanks in advance, and it's nice to find myself among the original community, many of whom I see are transplants from the good ol' SDML days.

Edit: Oh yeah, my friend has been trying to figure this out with me. Me modelled a 3d animation on the fly of the turbine side of the VNT. We just aren't sure about the spring placement. Anways here it is:


http://www.youtube.com/watch?v=Gc2awh0O0Bc"]http://www.youtube.com/watch?v=Gc2awh0O0Bc

[turbovanman²]

Welcome, :wave1:

Very interesting idea, I would be curious if it works also. In theory, all the factory did was use solenoids as bleeds if I have the workings right so if you can manage to copy that using MBC's, it might work.

BTW, why a VNT turbo, a TII can easily make good bottom and top end power?

[Arro]

Well first off, thanks for asking me why, instead of what some people did on the *other* site who just TOLD me I was making a mistake.

I used to own an '89 Daytona Shelby TII, and before that a Datyona Pacifica, so I'm not new to these cars... I was actually pretty active on the SDML back when Gus was barely breaking into the 13's (he was awesome stuff wasn't he?), and before Dan Culkin toyed around with his "D-valve". it was alot of fun. But after those cars, I moved on to other platforms... DSM, Then Nissan turbo, and now I have a 2000 Dodge Neon SE. I want to push 7 psi or so into it. So I figure a VNT is a perfect way to tie in my roots. A rising-rate FPR and high-volume pump is pretty much all you need with those cars. Turns out they're very similar to the oldschool ones.

Next spring, I'll be swapping out the engine to the 2.4L DOHC Turbo from the SRT (big job but I have someone who will source it and do the work for a good price). I want to take what I learn about VNT on my 2.0L, and use that trick on the SRT engine, only with a VNT-S60 (or S62? I saw on here someone had one built by TEC, awesome!).

I figure if people are putting down close to 300hp on 16-18psi from a VNT-S60/62, on a SOHC engine, imagine what 22psi on a MUCH improved head design (like the 2.4L DOHC) will produce.

I know that it's *easier* to make more power with a standard-configuration turbocharger, but I like the idea of a more linear power curve from almost instant boost. It's even better than ball bearing option!

I'm trying to get down all the basic concepts so I can do this without computer. So I drew up these diagrams in the hopes someone in the community could tell me "yeah, that looks like it's gonna work", or "no, you're missing a few things, and ya got a hose backwards there..."

So please, anyone and everyone with input, feel free!

:)

[quantum]

Looks like a good design. Personaly I would take boost signal as close to the compressor housing as possible so you have a faster reaction on both the boost controler and external wastegate (especially if your intercooling) reducing the chance of overboost.

[turbovanman²]

Interesting. I have put an SRT engine into a 95 Neon and it wasn't fun, :( a 2000 model should be easier.

I hope some VNT guys will pipe up but I don't think you can get 22 psi out of one.

Gus and the good old boys, they got me into this and a few are on this site, we have a few old timers here, ;)

[t3rse]

nope, 18 seems to be the max and it really sucks over 15, at least on my buddy's csx...

however, at 15 the car is a cornering dream, it pulls hard off the apex but doesn't have enough to roast the tires.

[Arro]

Out of what, a stock VNT25 or a VNT-S60 (or this S62 version I saw on here)? if a stock VNT is fine with 15, I can't imagine that a VNT-S60 is limited to 18.

Thr SRT engine will physically fit fine in my 2000 chassis. The firewall will have to be modded for the transmission, but the real PITA is that you have to replace the engine harness (of course) and the entire body harness as well (ick!).

[90Dodgevnt]

I had many e-mail w/John Craig from Limit Engineering who rebuilt my orig. VNT25 years back.

Running 20+ psi on a VNT28 is not a bad thing, as long as it's balanced properly and has a good supply of oil.

The VNTS60 should be good to at least 23 psi if not more...under the same conditions.

A VNT25...personally I would not run over 15 psi.

Let me see if I can find the e-mail.

Edit:

found it
-------------------------------
Mike,

I don't know which compressor wheel your turbocharger builder used. I looked at some
TB03 (same as T28) compressor figures and I still don't think you have a problem as long
as your turbocharger builder did things properly. At 24 PSI (2.63 pressure ratio) I estimate
that your turbocharger is turning about 150,000 RPM. If the turbocharger is balanced
properly, RPM is not the problem. As boost levels rise, thrust increases. Stock thrust
bearings are easily over loaded. If your turbocharger builder didn't use the proper thrust
bearing, then you have a failure waiting to happen.

It makes sense to me, that your boost increased after changing exhaust pipes. That turbo
was designed to run with a specific amount of backpressure. By changing exhaust pipes,
you removed that backpressure.

What do you mean by "clipped vanes"?

Regards,

John

------------------------------------------

To: johncraig@limitengineering.com
Sent: Wednesday, December 31, 2003 12:12 AM
Subject: Dodge VNT Turbo


John,

I spoke to you a few weeks ago about a few technical questions on VNT25 Turbo for my 1990 Dodge Shadow VNT. This is what my setup is currently running:

-Ported intake manifold
-ported exhaust manifold
-52 mm Throttle body
-VNT25 Turbo (modified to VNT28...larger compressor wheel, clipped vanes)
-full 3 inch exhaust
-Adj. fuel pressure reg.
-Ported head w/+1 mm valves
-cone filter

Since I dropped in the 3 inch exhaust, the boost jumped from 16 psi to about 20-24 psi. I was told by the company that built the turbo that going over 18 psi with the turbo would basically make the turbo overspin and destoy the shaft. I did a little research and called a few other Turbo shops and they pretty much told me that the shaft speeds at that boost level would be well over 180k rpm, and that it would lead for definate turbo failure. You were the only person to tell me that the turbo would not grenade, and that I could run the boost right up to 30 psi without any problems as long as it had a good supply of oil (I run Mobil 15w50 synthetic) and a good supply of coolant.

In talking back to other Dodge VNT Turbo owners on Turbododge.com, I was pretty much told same thing and that I should look to finding a way to get my SBEC reprogrammed, or find a way to limit the boost. Are there any technical reports or any type of documentation I can find to disprove all the naysayers, or can you tell me of anything I should or should not do with this engine setup? I have to say this car runs great and is a blast to drive, but I am concerned on the turbo not lasting....


Thanks for your help or any guidance you can supply.

Mike

[turbovanman²]

Out of what, a stock VNT25 or a VNT-S60 (or this S62 version I saw on here)? if a stock VNT is fine with 15, I can't imagine that a VNT-S60 is limited to 18.

Thr SRT engine will physically fit fine in my 2000 chassis. The firewall will have to be modded for the transmission, but the real PITA is that you have to replace the engine harness (of course) and the entire body harness as well (ick!).

Firewall mods, damn. I just reused his stock 95 DOHC trans and installed an OBX. Had the guys next door install Microtech standalone. I am unfortunely working out the bugs, :(

[tryingbe]

http://www.thedodgegarage.com/turbo_vnt_pictures.html

[turbovanman²]

http://www.thedodgegarage.com/turbo_vnt_pictures.html

Neat, I can't believe how small the turbine wheel is. :wow1:

[Frank]

Interesting stuff here. I know the S60 VNT don't yield as desirable results as expected on the 8 valve motors, but that is due to the S60 compressor wheel having more mass then what the original turbo was designed with. On a 16valve, I would imagine that this would be overcome. However don't expect that much out of the turbo. This is because with the higher head flow of the 16v, that it is going to be harder to run more power. Obviously you will make alot more power, just be aware.


Have you considered the GT28 VNTs?? I have heard good things, but I doubt anyone here has tried them.


Frank

[ucku]

just came back from the track and ran a 13.60 at 99 mph in 89 csx with a stock vnt on a 89 stock tc motor, no mods. I put a s60 pump in the car and that is it and no converter in the exaust, car is running a full 2.5 exaust with a muffler. This car will go 12.s with a little more gas and timeing , but this is my daylie driver i put about 200 miles a day just driving around town. My boost swang 18 lbs and then went down to 15 lbs. This car has great manners can drive this car anywere.

[ironbird720]

^^^WoW!! Sweet numbers.Thats impressive for a stock setup

[Arro]

Interesting stuff here. I know the S60 VNT don't yield as desirable results as expected on the 8 valve motors, but that is due to the S60 compressor wheel having more mass then what the original turbo was designed with. On a 16valve, I would imagine that this would be overcome. However don't expect that much out of the turbo. This is because with the higher head flow of the 16v, that it is going to be harder to run more power. Obviously you will make alot more power, just be aware.

Have you considered the GT28 VNTs?? I have heard good things, but I doubt anyone here has tried them.

Frank

Hey Frank, I've never heard of a GT28 VNT. And I can't seem to find anything on Google. My funds will allow me a pretty healthy turbo purchase, so if you can lotate me some info and link it here, I'd be greatful. Maybe I can get something even bigger, like a GT60 VNT. Who knows.

[Frank]

I don't have the direct information yet, but I know Chris Wright at TU has it.

[turbovanman²]

just came back from the track and ran a 13.60 at 99 mph in 89 csx with a stock vnt on a 89 stock tc motor, no mods. I put a s60 pump in the car and that is it and no converter in the exaust, car is running a full 2.5 exaust with a muffler. This car will go 12.s with a little more gas and timeing , but this is my daylie driver i put about 200 miles a day just driving around town. My boost swang 18 lbs and then went down to 15 lbs. This car has great manners can drive this car anywere.

Thats pretty good, damn, :D

[ucku]

http://i106.photobucket.com/albums/m248/ucku/6.jpg

[TopDollar69]

Early style taillights in an 89 VNT?

[ucku]

good catch on the lights , i hate the 89 lights so i went with the lego lights off a 88 car

[TopDollar69]

Ah I see, I've aways been partial to the Sundance ones myself.

[Arro]

Bringing it back on topic, what do you all think of THIS:

http://www.youtube.com/watch?v=Frs6aQGOrlo&mode=related&search=TD%20VNT

Direct-throttle control of the actuator? Is that what we're seeing there?

Ok so I got my turbo finally in the mail... the shaft play on this is whacky, wobbles quite a bit, but the wheels don't scrape the housings. What is it that renders a turbo "unrebuildable"? As far as I can tell, the vanes shift fine.

[TopDollar69]

Usually it's when the vanes have contacted the compressor housing taking material away.