Author Topic: a different kind of VNT control (Read 11488 times)

moTthediesel · « **on:** March 28, 2009, 06:23:11 pm »

After years of rust work on my diesel Porsche 356 project, I'm finally putting the mechanicals together. I've spent a good bit of time lately working on a VNT controller for my 1.6 Quantum engine. While mine is the same in principle as others seen on this board, in execution it's quite different. While I guess it doesn't have much application to front drive VW's, if any of you are interested I've posted a few pictures and will try to describe it's workings.

These cars had solid rod throttles and while I guess I could have patched a bowden cable on, I decided to stick with old time rods and bell cranks. This car has a very small engine compartment and there is a lot of equipment and plumbing to cram in there, so I decided to fit the boost control can and vane control mechanism in the space between the long runner GTI intake manifold and the cam cover. That's air space that would have no other use.

I fitted a shaft along the back of the firewall behind the head that pulls the fuel control with a bell crank and rod. On that shaft is a cam which acts on a rocker with a central pivot attached to the intake plenum. The other end of the rocker pushes down a rod that goes through the manifold web and closes the vanes.

I'm fooling with cam profiles now, but the idea is that the vanes will only be closed by the last 25% or so of throttle travel. This will allow the vanes to be controlled mostly with the "loud pedal", and to remain open in most steady-state driving, only closing when the helmsman calls for flank speed. For further boost control, a can is fitted that pivots up the cam follower when the set level is reached. I used the standard vacuum can that came with the VNT, but fitted a compression spring to force the diaphragm into the "full vacuum" position. Boost pressure then extends the control rod, lifting the cam follower and allowing the spring loaded vane control rod to return to the open position.

Crazy complicated? Maybe, but it fits where it has to, and it seems to do what it needs to. I'm still at least a couple of weeks away from running the engine so no trials yet. I'd be interested to hear what anyone thinks about it.

moT

lord_verminaard · « **Reply #1 on:** March 30, 2009, 12:54:21 pm »

Pics don't work!

Good to know you are continuing on this project. I've recently gotten involved in 356 Restoration with a guy named Lowell Sivey, he's one of the best at this. Here's a car we are nearly finished with:

It's a 55 Carrera. We've got 3 more in the shop that will be next. The one on the rotisserie in back is the only one of it's kind in the USA- the owner wants it done by next year. :shock:

I'm really interested in your project, keep it up!

Brendan

myke_w · « **Reply #2 on:** March 30, 2009, 01:21:40 pm »

good lord that's sexy!

zukgod1 · « **Reply #3 on:** March 30, 2009, 01:33:30 pm »

Quote from: "lord_verminaard"

Pics don't work!

Good to know you are continuing on this project. I've recently gotten involved in 356 Restoration with a guy named Lowell Sivey, he's one of the best at this. Here's a car we are nearly finished with:

It's a 55 Carrera. We've got 3 more in the shop that will be next. The one on the rotisserie in back is the only one of it's kind in the USA- the owner wants it done by next year. :shock:

I'm really interested in your project, keep it up!

Brendan

HOLLY HELL!!!!!!!!

I absolutely LOVE that car!!!

PLEASE please PLEASE do a build up thread? I want more pictures.
I painted a couple of those back in the day. Full metal cars. Nice stuff.

subsonic · « **Reply #4 on:** March 30, 2009, 07:33:58 pm »

You know, I have been looking at one of those long runner intakes and tying to figure out how the hell you would get the manual controls to work for a vnt setup. I was wondering if there was adaquate room to drill through between the runners to run some sort of setup. I guess there is. Have you, or anyone else for that matter, seen any other mechanical vnt linkage setup's that involved the long runner intake like the above gti unit or a 1Y / 1X ? I am guessing the turbo would need to be re-clocked like Andrew did on his Mercedes gt22??v install, due to the fact that the runners go way back behind the head.

moTthediesel · « **Reply #5 on:** March 30, 2009, 08:19:36 pm »

Well, I finally got the pictures to load in a visible size, sorry, I'm new to photobucket.

My car is a plain old C coupe, sadly, not a Speedster

Here's a pic of the rear of the car, and one of the 2-1/2" ss exhaust.

Turbinepowered · « **Reply #6 on:** March 30, 2009, 08:34:08 pm »

You're my new hero. A diesel, in a super-sex Porsche 356? I have wanted a 356, any 356, since I first learned what a good looking car was...

lord_verminaard · « **Reply #7 on:** March 31, 2009, 06:38:17 am »

Quote from: "moTthediesel"

Well, I finally got the pictures to load in a visible size, sorry, I'm new to photobucket.

My car is a plain old C coupe, sadly, not a Speedster

Nothing wrong with that! We've got a C-coupe in the shop too, it's a '65- with disc brakes all around, the C-coupes are my favorites.

Not to mention a little more practical.

After looking over the pics about 5 times and re-reading your description, it finally sunk in, pure genius! Other than the modified deck lid, did you have to modify the engine bay much? Are you using the stock Porsche Transaxle?

This looks killer, I can't wait to see it driving!

Brendan

lord_verminaard · « **Reply #8 on:** March 31, 2009, 07:07:24 am »

Quote from: "zukgod1"

HOLLY HELL!!!!!!!!

I absolutely LOVE that car!!!

PLEASE please PLEASE do a build up thread? I want more pictures.
I painted a couple of those back in the day. Full metal cars. Nice stuff.

Don't really have a build up thread, since it's not my car. I also don't want to thread-jack but I'll quickly post up what I've got.

Here's where it was when I first started working for this guy- well, actually it was in primer but we painted it soon after. The body work prior to this was extensive. The owner bought it in Mexico, some crazy Mexicans had hacked up the doors to put in power windows (

) and there was prior bodywork where they had cut the front of the car off and nearly cut through the serial number. Amazingly the engine was still there.

Later details:

It somehow still had the original badges so we cleaned them up and re-used them.

Carreras' had dry-sump oiling from the factory.

And bigger front drums.

Original gauges!

(notice the '65 in back)

Sadly, we aren't building the engine for this one, the owner has his own engine guy. He's got almost $200K!!! in the engine alone. The Carrera's had the crazy 4-cam aircooled engine, not the typical pushrod Beetle-like engine. (though they were not the same) The Carrera engine had roller bearings, shaft-driven cams, dual distributors, dry sump oiling, etc... pretty high tech. The car will be worth upwards of $700,000 when it's finished.

Sorry to moT, I don't want to take away from your post, if you want me to take down the pics, just let me know.

Brendan

moTthediesel · « **Reply #9 on:** March 31, 2009, 07:26:22 am »

Quote from: "lord_verminaard"

We've got a C-coupe in the shop too, it's a '65- with disc brakes all around, the C-coupes are my favorites. Not to mention a little more practical.

After looking over the pics about 5 times and re-reading your description, it finally sunk in, pure genius! Other than the modified deck lid, did you have to modify the engine bay much? Are you using the stock Porsche Transaxle?

The motor fits fine with little modification required. I didn't really need to put that hump in the deck lid. I was trying to put the radiator there, but it didn't work out. Now it's mounted on the right side of the engine with an air scoop and duct from under the car. It's an aluminum two row "Scirocco" rad from Summit, supposed to be good for 600hp. :lol:

The trany is a stock Porsche 741 four speed with a Kennedy adapter and a Kennedy stage 2 clutch. I'd like to add the super tall 4G top gear, but it's not in the budget right now.

The engine is a fresh rebuild with a Giles pump and GTD nozzles and the VNT is blowing through a 944 turbo intercooler. I'd like to see about 110hp and 160f/lb at 15psi without straining anything too much. With this car's weight (about 2k#) and aero shape I'd expect to see 50+ mpg too. Lots of plumbing and wiring to do, but it should be ready to fire up in about 2 weeks -- YAHOO!

moT

moTthediesel · « **Reply #10 on:** March 31, 2009, 07:36:43 am »

Quote from: "lord_verminaard"

Sorry to moT, I don't want to take away from your post, if you want me to take down the pics, just let me know.

Brendan

Hell no! That's a great looking car and I'm glad to see it on here --

Those 4 cam Carrera motors are awesome, but for $200k he still won't see 160ft/lb @ 2500 like I will for less than a grand :wink:

moT

lord_verminaard · « **Reply #11 on:** March 31, 2009, 07:41:23 am »

Quote from: "moTthediesel"

Hell no! That's a great looking car and I'm glad to see it on here --

Those 4 cam Carrera motors are awesome, but for $200k he still won't see 160ft/lb @ 2500 like I will for less than a grand :wink:

moT

Heh heh. I bet he will. I guess the guy is putting a crazy turbo setup on it. He's got more money than brains I guess. This is the 3rd car that Lowell has restored for him, he has a total of about 12 356's I guess, about 6 of them are Carrera's of some flavor. The C-coupe also came from him, though Lowell bought that one.

I'd also say that you will probably be making more HP and torque than what you thought though, so that car should fly!

Brendan

moTthediesel · « **Reply #12 on:** March 31, 2009, 08:03:00 am »

I've NEVER seen a 4 pot Carrera with a turbo -- I sure hope he's got everything engineered properly, that has the makings of one very expensive grenade job!

moT

fatmobile · « **Reply #13 on:** April 01, 2009, 10:20:13 pm »

Hey Mot,
I don't understand exactly how that works.
It sounds like it's connected to the throttle cable but I can't see how.

moTthediesel · « **Reply #14 on:** April 02, 2009, 04:53:09 am »

Quote from: "fatmobile"

Hey Mot,
I don't understand exactly how that works.
It sounds like it's connected to the throttle cable but I can't see how.

There is no throttle cable in this car, it has a solid pull rod from the A pedal back to a bell crank on the transmission. From there another pull rod curves up over the axle and then up to a bell crank on the rotating rod behind the head (sorry, you can't see that in the pics). That has still another bell crank that pulls the fuel lever on the injection pump. The rod has a cam on it that lifts one end of the rocker mechanism (see in the bottom picture above) as it turns. The other end of the rocker pushes down on the vane control rod and closes the vanes.

The advantage to this (as I see it) is that by experimenting with the shape of the cam you can adjust when the vanes close relative to pedal movement. Also the vane movement is positive in both directions so that it's less likely to stick either way.

I had trouble with the curved rod from the trany up to the engine, it would tend to straighten out when pulled which made for notchy throttle movement. The answer was to truss the 1/4" curved rod with some 3/16" rod as you see here, nice smooth, progressive movement now!

moT