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Mustang throttle body mod

 
Old 02-15-2003, 03:42 AM
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--JR--
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Post Mustang throttle body mod

I've been hearing people talk hear and there about a 80mm Mustang throttle body that can be retrofitted to the 928.

Has anyone seen this, know what's involved and what Mustangs (models/years) this throttle body came on?

I have a 78 car that has headers and a new exhaust in the works. I thought I might pick up a coulpe more ponies with this mod. On the other hand I have heard that the factory ?70mm? body is good for a 400Hp motor. But yet again I have heard that the body is one of the more restrictive components in the intake.

I do plan on opening up the heads a bit more in the future and probably looking into cam upgrades for my 78... But I've dropped over $5K into it over the last year and I think I'll slow down a bit for now.

Thanks!
78 9288200419
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Old 02-15-2003, 01:45 PM
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John Struthers
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JR,
If we could just slap hardware on the sHARKs we would probably be the most obnoxious of all Porsche owners - quite a feat-. And we would also be spending time on the side of the road talking to the speed enforcement people.
There are 2v and 4v stangs' just like there are 2v and 4v 928's, similar displacement. Depending on GT, Cobra, or Cobra R the rpm/torque band may be similar. What won't be similar is the computer and how it is mapped. Our early models won't allow for chipsets. The Throttle body up grade, even on the stang's, will require a calibration of the the mass air sensor -maybe a bigger one of these too so as not to restrict airflow- as will the MAS on the 85'-95' model 928's.
I'm not sure if we can calibrate the air flow meter (AFM) on the early model 80', or the AFM on the typical 81'-84's. Mapping, Mapping, Mapping.
Some of the late versions of the 5L and, the 4.6 2 valvers had optional camming. So depending on cam profile, wheel size and gearing which can affect your off the line performance - Grunt- as well as mid/top end performance you can see where calibrating the sensors, particularly after a inlet volume change, which talks to the computer/ECU will need a little consideration. While the stang's will wind out like the shark I believe they go to full advance a bit earlier -not positive - and cam folks want full vac. by 3500rpm. I'm sure you know there are a lot of variables when trying to extract more power from the 928 both hardware and software. Due to Murphy's Law, and the Handbone Connected to the Wristbone Theorum's even the the finest collection of individual performance parts will invariably lead to an infinite number of the many small sadnesses that trouble our otherwise carefree lives.
Some of the sadnesses can be eliminated with stand alone high-end engine management systems.
These systems vary in utility depending on the supplied software, and of course, COST.
Get a JEG's Catalog for reference - jeg's.com - and check out some performance magazines if nothing else you can make some inference based decisions derived from manufacturer sales blurbs and get an idea of the cost.
I'm all for the Idea, personally, I would like to see the whole Mustang chipable computer, fuel system, pumps, injectors, sensors, ignition... grafted onto the sHARKs simply because there are so damn many Mustang's, hence, lots of available parts and lower parts' cost.
Remember! If YOU waste a lot of money, time, and pieces of your sanity.... your loss will benefit the rest of us. Or, better you than me.
snicker, snicker.
I think you need to brainstorm this one, talk to people in local hot rod, drag racing, or performance clubs before you leap into the fray.
Take some of the big iron people for a RIDE, they may show some interest after changing their shorts and offer FREE insight to your project.
There are some good folks out there who don't drive a Porsche. Try em'
John S.
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Old 02-15-2003, 07:28 PM
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dr bob
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Um, the '79 is a CIS car, so changing th ethrottle body requires no change to MAS/MAF since there isn't one.

Simple stuff will dog you though. The vacuum for the distributor plugs in at the throttle body, sampling airflow to determine ignition advance. Does the Mustang TB give you the same vacuum at the same load?

A temptation might be to find a throttle from a 6.9 or 6.3 MB with CIS to attach.

If you don't spend a whole lot of time at full throttle, consider modifying your throttle linkage to get the existing throttle open further with less pedal. Even if you don't do that, do make sure that the throtle is fully open when the pedal is on the floor, make sure that no carpet or mat is in the way of full open performance.

Just some casual thoughts. Your Results and Opinions May Vary.

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Old 02-15-2003, 08:32 PM
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Cool

dr bob,
You will note in my typical CYA fashion
that while I included the 85'-95's, 81'- 84's and the lonely 80 MY I, glaringly, left the 78 & 79.
JR's is a 78. and I was hoping Dennis or some other, kind and knowledgeable soul would jump in.
You have been elected.
While you are here what prevents a lean condition in the CIS critters at WOT? Throttle linkage and manually tweaking the fuel/air?
TIA
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Old 02-15-2003, 09:21 PM
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JR,

That's the best one I've heard all day!

You've dumped five large into the car in the last year & you didn't even know that it's CIS. Doh!

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Old 02-16-2003, 01:13 AM
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JR, Don't let the 5 grand comment get to ya. some of us know that you can put a few K into these things wtihout even lifting the hood.

Wheels 1000 (Cup 17")
Tires 400 (Kumhos)
Windsheild replace 1100 (insur. payed however)
Alighnment 250
Climate Control Head 400
EFI & Fuel Pump Relays 80...

Wheel Bearing Repack, New battery, Door handle mechanism, etc. etc. etc. all since last March.

We're with ya bro.- Ruf
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Old 02-16-2003, 01:21 AM
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I hope this is not OT.

Greetings Dr. Bob and all y'all,
please forgive me, I just watched "Sweet Home Alabama" ....
but John S. just asked: "While you are here, what prevents a lean condition in the CIS critters at WOT? Throttle linkage and manually tweaking the fuel/air?" ....
and it made me think of a question I would rather have answered... How do you control a rich condition at WOT?

I ran my car (83S Euro w/CIS) on a dyno last fall and according to the dyno tech, the Fuel/air ratio at the top end was very rich....
he said it was bordering on "black smoke" and I was leaving horsepower on the table. I just wondered how a person goes about tuning around that???? I thought the idle and mixture adjustments were just for idle purposes.

Your help and advice is appreciated.

Best wishes.

Joe Ferguson
'88 S4 A/T Black/cashmere (her driver)
'83S Euro 5sp pewter/black (my project)
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Old 02-16-2003, 04:55 PM
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Dennis Wilson
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The air fuel curve on the 78 CIS is all mechanical and linear to air flow. The later models have an O2 sensor to fine tune the mixture, so if your car was running rich at the top end only, you may have a lazy sensor. If rich at all rpm's check for a blocked fuel return line, bad vacuun line(s) to the WUR, or a bad WUR.

Dennis
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Old 02-16-2003, 05:11 PM
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Concerning the 80mm Mustang TB. It would be easier to install a later model euro TB, but to see any gains you would also need to replace the intake runners and heads with the euro versions. Porting, polishing and extrude honing your existing intake would be a better/cost effective update. If pollution isn't an issue, removing the air pump and cat will bring you up to the 78 euro specs. If pollution control is an issue, headers and a freer flowing exhaust (with cat) would be another option.

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