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What are effects of bigger TB?
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Author:  Sam Powell [ Sun Aug 01, 2010 5:35 am ]
Post subject:  What are effects of bigger TB?
So, I went to the Haggerstown slant six races, and had a pretty good time meeting the folks and participated in T&T and raced the brackets, (well just bracket as I red lighted in the first round).

What I found out is that the car is no where near as fast as I had hoped. But, everything worked pretty well. I did blow off one intercooler hose, but it stayed on after really cranking down on it. It runs a pretty consistent 16.75 or so, even with my pathetic neophyte driving skills. The red light was pretty justifiable, and indicative of my drag racing skills at this point.

So the question is, what is the next step? Tuning will absolutely help, as it has only been together and running well for two weeks now. But, here is the big question. When I put this together, I used the TB from a standard Buick Century, and not the TB from the Grand National. This means the TB is quite a bit undersized. I did this simply because the throttle blade rotated in the correct way to use the stock throttle linkage. But now it seems it might be worth figuring out how to make the larger TB work. I have several questions:

1. What effects will the larger TB have on tuning? Will I have to reconfigure the entire map, or just the WOT part of it?

2. How will the larger TB effect the power and performance of the engine? I understand the effects of a larger carb on an NA engine. Is it similar to this with turbo as well? I know this sounds like a dumb question, but I am hoping someone who has put a larger TB on an EFI and or turbo car will have some useful info here.

3. Is there another TB set up I should be looking at? The under hood space is actually a little cramped, so I must be efficient with any elbows that turn the air flow from horizontal to vertical. I think I threw away an old Ford truck TB elbow that might now prove useful here. I am in no hurry here for sure. The car runs, and runs well. But if I am going to put time into tuning it, maybe I should do this with the larger TB on first.


Thanks in advance for any thoughts or knowledge shared.

Sam
Author:  Dart270 [ Sun Aug 01, 2010 6:30 am ]
Post subject: 
It should make more power just like a bigger carb or head porting will. I got a takeoff 2000 or so Mustang 4.6L GT TB that is definitely big enough for you, and dirt cheap. Mounts in a similar config to yours but bore is about 70 mm. I don't think you will see big differences in tuning except at or near WOT. This is because the MS senses MAP and doesn't care about throttle position.

Fantastic to see you at the race this weekend. You ran 84 MPH, which should be fast enough for 15s in the 1/4 mile. Looking forward to progressing forward with "the new Dart."

Lou
Author:  Sam Powell [ Sun Aug 01, 2010 12:54 pm ]
Post subject: 
Lou, is that "I got" as in a have for sale, or "I got" as in I have on my car? I'm talking about the 70mm TB you say you got.

Sam
Author:  emsvitil [ Sun Aug 01, 2010 2:37 pm ]
Post subject: 
What is the current TB size vs what you're thinking about ( ? vs 70mm ??? )



You might get away with some TB blending and porting to smooth the flow.


The lips where the hose fits over will be restrictive too because of the step down in size. (some dremel work to smooth out the transisition).
Author:  Sam Powell [ Sun Aug 01, 2010 4:00 pm ]
Post subject: 
Ems I am always delighted when you contribute. Thanks. It seems the difference between the standard 3.8 GM tb and the turbo GM TB is more details. The one I am using now, appears to be 60mm ID inside all the way through, with no finesse at all. It has blunt edges at the top. The turbo set up has a tapered air horn that is very carefully shaped at the top with a nice taper to the edge. It measures 70mm at the very top, but very quickly tapers down inside to 65mm at the blade. And then below that, it tapers down to 55mm at the mounting flange.

I did not remove the one I am currently using, so it could possibly get to 55mm as well.

It seems that if I am going to change things, I should go with the bigger TB such as Lou suggested. It does not seem as if there is a big enough change between these two to make much difference. But maybe I am wrong there. Maybe the turbo one will pass considerably more air than the stock NA one. But that is not my gut feeling just looking at them.

If I go with the Ford unit, I think I will have to provide vacuum nipples for a number of things if I do this. I am not sure Lou's TB has these. It seems it is much thinner in profile from top to bottom.

Sam
Author:  Dart270 [ Mon Aug 02, 2010 6:52 am ]
Post subject: 
I was using correct grammar. "I got" meant "I bought, once upon a time." I currently :) have :) that piece, and I will be using it on my next port EFI setup. Sorry to confuse.

These should be easily available on Ebay or at a junkyard. Now that I think of it, it might be 66 mm at the narrowest point, but I'd have to measure. It was just the factory Mustang piece.

I doubt your TB is a major restriction if it is 55 mm at the narrowest point. To get max HP, you'll need a bigger one, but I bet a bunch of tuning is the first thing to focus on. My '68 Dart runs low 16s naturally aspirated with probably the same size TB and essentially a stock cam.

I am pretty confident we could get your car running at least in the 15s with only tuning (mixture and timing) changes. I guess verifying you are not venting boost pressure via hose connections would be another check (boost gauge).

Lou
Author:  Sam Powell [ Mon Aug 02, 2010 9:43 am ]
Post subject: 
I wonder if there is a standard procedure for checking the intercooler hoses.

It seems a schraeder valve in one of the tubes might be a place to start. However the turbo end would leak down quite quickly. I would guess the tb would leak at the blade to the extend that the idle air setting opens it. I guess I could plug each end and put some air pressure in it. It would not take much. Nor would it tolerate much.

Now that the engine is not going into preignition hysteria at the drop of a hat, there are boost levels that might be tunable as well.

Do you know which year and model Mustange your TB is from?

Sam
Author:  Dart270 [ Mon Aug 02, 2010 9:55 am ]
Post subject: 
I believe it was from a 2000 GT 4.6L V8.

Lou
Author:  kesteb [ Mon Aug 02, 2010 8:34 pm ]
Post subject: 
I would use the stock 5.0 ford piece. It has various vacuum fittings and measures 65mm at the throttle plate with a built in IAC.
Author:  Sam Powell [ Tue Aug 03, 2010 5:08 am ]
Post subject: 
Quote:
I would use the stock 5.0 ford piece. It has various vacuum fittings and measures 65mm at the throttle plate with a built in IAC.
Is this a simple single plate design? And I assume they made some MPI and some Throttle body 5 litres. The simpler thing would be to find the MPI style. How do I recognize it in the junk yard? I know the newer 4.6 engine has the plugs down in the center of the head. There must be tons of cars out there with the 5.0 L engine in the yards.

Sam
Author:  Matt Cramer [ Tue Aug 03, 2010 10:53 am ]
Post subject: 
The MPFI 5.0 liter was found in Mustangs, Thunderbirds, some Crown Vics, a lot of things, really. The intake manifold is a dead giveaway - it has a plenum on one side of the engine compartment, throttle body on the other.
Author:  Reed [ Tue Aug 03, 2010 11:40 am ]
Post subject: 
I just got done converting my 1989 Ford van from speed density to MAF fuel injection. I have learned a small bit about Ford throttle bodies in this process.

Ford used two style of throttle body in the late 80s to mid 90s. There is the large single bore passenger car style:

Image

Image

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and the double bore truck and van style:

Image

Image

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Image


Both the truck and the passenger car style throttle bodies have vacuum fittings, have integral IAC valves, throttle position sensors, and have throttle and kickdown studs compatible with Lokar style throttle and kickdown cables.

Based on my experience, when I build the MPFI systems for the slants in my brother's Duster and his van I will be using the passenger car single bore style TB. This is mainly due to its square mounting bolt pattern and the much wider availability of factory and aftermarket air filter and air intake tube options. Also, Ford MAF sensors were only made in the large single bore style. I had to cobble together a home-made adapter to go from the double bore van throttle body to the single bore MAF sensor on my van. It works, but it isn't pretty.

I plan on using the factory Ford MAF MPFI system. THis system can be tuned using an aftermarket device called a TWEECER and a laptop. You plug right in to the factory computer and can control all the parameters of the timing and mixture. :D THe hardest part will be adapting the Ford TFI distributor guts to the slant six, but that can be done.
Author:  kesteb [ Tue Aug 03, 2010 10:14 pm ]
Post subject: 
I wouldn't wast my time with the TFI, just go straight to EDIS.
Author:  Sam Powell [ Wed Aug 04, 2010 4:41 am ]
Post subject: 
Keysteb, would you elaborate on that one please? Doesn't the EDIS require an igiition pickup wheel on the crank? I have been lost as to how these work when I read about them. If I can get there with MS II with a minimum of fuss, I would have to see pretty big gains from an EDIS system to justify doing it. Also, I just have never understood how they work. I would either need deeper understanding, or a good cookbook diagram from someone who had done this before to go there.

One of the reasons I got in trouble with Accell was they did not provide good diagrams about how their ignition pick up system interfaced with other types of ignitions or pickups. I am certain this was always the weak link in the program.

Sam
Author:  Sam Powell [ Wed Aug 04, 2010 6:26 am ]
Post subject: 
So, I went to AMazon just to get an idea of what new things there are out there, and what they look like, and this is what I found.


http://www.americanmuscle.com/94-98-mus ... odies.html

Which one of these looks like what I should be looking for in a junk yard? Or on E-bay. Will I find anything out there that looks like these things? And which size would be the upper limit? Is a 75mm too big?

It seems most of the new ones do not have vacuum taps. But, most have a TPS mount, if not the TPS itself. The vacuum lines must come off of the plenum, if they have them at all.

Look at the upper plenums shown at various places. It looks like these could be adapted to the Offenhauser manifold. This would require a very thin TB as the AC compressor sits right in front of the manifold there.
Or raised up and turned to reach over the fuel rail.


Then I went on e-bay and looked at these bewildering selection.

http://shop.ebay.com/i.html?_nkw=5.0+th ... rom=&_ipg=

I would not have a clue which one to buy. It looks as if the 87-93 units are the ones with vacuum connections. And it looks like there are some pretty cheap things there. But, how do you know what you are getting? A junk yard still seems like the place, if I can get a handle on what I am looking for.




This is still in the dreaming, planning stage. I spent all my money on wheels for the month. I am not marching off to a junk yard till it gets a little cooler.

Sam
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