F.I. intake manifolds

noincome · Post by **noincome** » Thu Aug 30, 2001 3:33 pm

First off please forgive me if I ramble on a bit. I know that this topic has been discussed on this forum in the past however, in the last few days there has been heated discussion on what makes more H.P., fuel injection or carbs. I do not want to stir up any echoes on that subject but the one thing that I would like to focus on out of this topic is the intake manifolds for fuel injection.

I recently purchased a 1956 bug and I'm planning on pulling my turbo engine out of my Ghia for use in the 56. While the engine is out I'm going to convert it over to F.I. Currently the engine runs a single Dell in a blow through arrangement, and I like the way that it runs. I know that I could make more H.P. with duals but that doesn't matter to me. My intention was to replace the carb with a 48mm dual throat throttle body and be on my marry way. I figured that the single would give me better low end street driveability, and that the extra H.P. that I would pick up on the top end with dual throttle bodies I could live without, and cost is a big factor. (BTW this is a street engine) Plus I read somewhere, can't remember where, that the only reason CB Performance came out with dual throttle bodies was no one would buy the single throttle body units. You do have to admit though that dual carbs look cool on a VW!

I have all sorts of throttle bodies, in my stash, water-cooled VW, Porsche 914, Ford Mustang, Chevy truck TPI with all the TPI crap taken off, the list goes on. The only one I do not have is the single CB Performance throttle body. I've thought about using the two Porsche 914 throttle bodies that I have in a dual arrangement sort of a quasi Kadron deal. I feel that setting the linkage up for this maybe a PITA. I also thought about using my IDF center section with one throttle body centered at one end of a 3" piece of exhaust tubing. I may experiment with this just to see what type of performance it gives. Anyway I'd like to throw this out to all of the forward thinkers on this forum. If you had to build a fuel injection manifold for a street driven VW, not a monstrous one, how would you design it, what would you use for a throttle body, and what are the reasons for your choices? There are no right or wrong answers, just open discussion on what you do.

ray greenwood · Post by **ray greenwood** » Thu Aug 30, 2001 5:15 pm

Well...if you don't absolutely have to have twin throttle bodies, and you have dual port heads...has think about using a late model type 1 fuel injection runner system? It still allows the use of the upright fan...is not a bad FI manifold system...can be modified to use type 4 throttle bodies without too much trouble. Either use the stock injection, or just use the runner and throttle body system and try slaving some ofthe aftermarket units to it. Those will take some tuning I would bet. But the late model type 1 FI system is a straight bolt in. Ray

Duc · Post by **Duc** » Thu Aug 30, 2001 7:58 pm

Just purchase a single TB from CB. They will sell it to you, though they will try to sell everything else too. They run about $240 or so a piece. As for the ECM you will need something that will allow you to do some tweaking.

D

noincome · Post by **noincome** » Thu Aug 30, 2001 9:08 pm

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Duc:
<B>Just purchase a single TB from CB. They will sell it to you, though they will try to sell everything else too. They run about $240 or so a piece. As for the ECM you will need something that will allow you to do some tweaking.

D</B><HR></BLOCKQUOTE>

That's too easy, lets think outside of the box. Like I said "My intention was to replace the carb with a 48mm dual throat throttle body and call it a day". However, why should I spend $250.00 on a throttle body when I have several in my possesion? I could cast my own if I had to. Why do you have to run a throttle body that resembles a Weber?

If you look at the how to build a manifold tech article at the SDS site, that is something that could be adapted to run on the single Weber center section. Besides the outlet on my turbo would bolt up beautifully to a single throttle body once I've got everything dialed in. I even have a fuel injection manifold from a Transporter that I could use. I've seen a set up like that posted here on this forum. There are not that many people in my area that I can talk to about things like this, hell some of you guys may be in the same situation. I just thought that maybe if we got some dialog going about this it could help some other people out in the process who do not want to spend $250.00 on a single dual throat throttle body, or $500.00 on a set of duals if you can get almost the same performance from a single throat.

Duc · Post by **Duc** » Fri Aug 31, 2001 2:39 pm

Sorry, been box thinking all my life.

The only thing holding you back from using another TB is insuring that the TB can withstand blow through presures you will be running. The other limitation you will have is that the air flow through your close to stock manifold would be less than a larger one. That would be the chalange to get rid of those restrictions. What your talking about doing is what I want to do, with my T4 but I don't have the skills or connections to make that happen, yet.

D

ray greenwood · Post by **ray greenwood** » Fri Aug 31, 2001 4:16 pm

There are large #'s of superb throttle bodies for FI...laying around in junkyards. There is nothing too special about FI throttle bodies. They just have to have the size you require, flow well and have throttle plates that cause as little turbulence as possible when opened. Since they do not operate on the venturi principle...or have to atomize fuel...they simply have to duct or control the air smoothly and in the correct volume for you. Tuning is a matter of plumbing and distance...and most is done with the runners/manifolds themselves. Find throttle bodies with the least amount of clutterance on them. No cold start jets mounted at the TB and TPS switches that can be romoved without disturbing the function of the throttle shaft. Some like the one I use from a vanagon on my 412, actually have nice replaceable throttle shaft seals. All of the progressive throttle bodies on the VW audi CIS injection are excellent. There are hundereds of subtle machining changes within the myriad of part #'s...and there are dozens of aftermarket designs....made by the oem manufacturers (neusped) that are known to improve on specific model #'s. Get a few...think about the runner plumbing first,,,to get an idea of how far...and what kind of twist and turns will be necessary in your system...cobble one together, that someone can put on a flow bench for you so you can swap TB's in and out to find which one will transition air in the best volume...with the best tunability and least turbulence for your set up. In the ugly junkyards of Dallas...TB's from any car are a flat rate 10 bucks..without throttle switches and cold start injectors. A throttle body is a throttle body as far as FI is concerned...it doesn't meter fuel.I think the only reason that the current VW after market FI looks like a Weber...is to fit in the locations a weber will...to fit the current applications of the masses. There is no good reason I can think of that it has to look like anything. Ray

Post by **Tom Notch** » Fri Aug 31, 2001 6:53 pm

I went to the local junk yard and got a TB off a GM 3L V6, stopped by the muffler shop and grabbed an exhaust flange that fit it and a chunk of 2 1/4" tubing. About 4 hours later, I had it all grafted to a bus plenun. Done deal.

I'll have a pix of it up in the next few daz on my site, I'll let ya know when.

------------------
Tom Notch
Tom's Old VW Home

69bug4me · Post by **69bug4me** » Sat Sep 01, 2001 12:08 am

I was also considering the switch to f/i,i have single plate T/B off of a 2.3 ford motor,it was free,aslo got a handful of injectors.Now all i have to do is fabricate the plenum and runners,not decide yet on whether to use stock end castings modified for the injector or just fab up a set from scatch.i am a welder/fabricator so that helps,so does having your own tube bender and tig welderplus a reletive that own the junkyard you go to. hopefully this link will work for dunebuggy.com there is a section on a F/I turbo set-up with some good info on runner length and plenum volume. http://www.dunebuggy.com/turbo/

69bug4me · Post by **69bug4me** » Sat Sep 01, 2001 12:13 am

oh crap it's gone bummer,guess i should have printed out the info!!!!

69bug4me · Post by **69bug4me** » Sat Sep 01, 2001 12:26 am

o.k o.k so i'm new here and had a brain fart...lol the correct link is http://www.dune-buggy.com/turbo/

Trebor · Post by **Trebor** » Sat Sep 01, 2001 1:45 pm

eeew does it stink?

Robert

[This message has been edited by Trebor (edited 09-01-2001).]

noincome · Post by **noincome** » Sat Sep 01, 2001 2:15 pm

I see you finally got it out! That's a pretty good link on intake manifolds. I do want to point out that the author of the article at Dune-Buggy.com states that the plenum size (volume) is usually 100% of the total engine displacement. I have read in several other places that the plenum volume should be more like 50-70% of the engines displacement. I'm going to start out with a manifold in the 70% range, and later on see if one in the 100% range offers more performance.

69bug4me · Post by **69bug4me** » Sat Sep 01, 2001 6:47 pm

yes that does sound a little bit more realistic,if you look at a v-8 manifold there is no way it would displace 350 c.i. I have not yet started making parts yet but i will probably use the stock end castings and weld the injector bosses in it and use a handmade center section,more than likely it will be on my 1915 in my rail then if i can get it all worked out i will modify it to fit under the decklid of my bug.

noincome · Post by **noincome** » Sat Sep 01, 2001 8:10 pm

I've used the stock end castings on my 1915cc engine and I'm happy with the performance. I planned on welding injector bosses in them but, everyone always says that the stock end castings are a restriction to flow. If thats the case, almost every turbocharged pull through engine I've seen runs them and most of them are are the 12's. I know that most people will say that you cannot compare NA to forced induction, and I would have to agree, but it looks like there may be a solution to the stock end casting problem if you want to run a center section type manifold. Bugpack has come out with dual port end castings that they call "Trick Ends" that have extra material all over them. These are thick end castings that allow you match port them to your heads. I have not seen them in person, just picture in the Bugpack catalog, looks very promising though.

Bruce M · Post by **Bruce M** » Mon Sep 03, 2001 6:30 am

Turbo end castings
check out aircooled.net

The std end casting have ID of 31.5 mm
(from memory )

Anyone know what size the turbo ones are.

This is one route I am considering. The next is to use dual barrel manifolds (possibly Type 3 to retrict height). Then use bolt on pipe work to link to single central TB.

Look at pictures of 911 manifolds for ideas.