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Discussion Starter #1
Howdy all...I've got a question I'm hoping someone here can help me with.

I've done a MAF conversion on my 86, 5.0, AOD. The donor for the harness and computer (J0T2) was a 1991 Town Car with 5.0 and AOD. I'm using the intake tubing/airbox/filter setup from a MAF F-150.

I'm using the actual MAF sensor from the Town Car, in the MAF housing from the F-150. I'm running lean.

The MAF housing from the Town Car is tiny (55mm?????), compared to the housing from the F-150 (70mm?????), and I think this is causing my lean condition. Can anyone confirm this? From what I understand of how a MAF sensor works, I think that the larger size housing is throwing off the actual sensor. Am I on the right track?

I'd like to avoid getting a Tweecer and investing the time and $$ in a custom tune, and I'd like to retain the factory airbox and MAF housing.

What other vehicles had the same size MAF housing as the F150, that I can use in place of the Town Car MAF? The F150 MAF uses a different connector...

Help!

Thanks!

-Mark
 

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Discussion Starter #3
JB, thanks for the reply. No, I haven't tried the housing from the TC - the airbox is completely different from the F150's. The flange is a different bolt pattern, the airbox lid is a different shape, and the MAF is angled. The diameter is also different, so it would take a fair amount of rigging and some tube/adapters to make it work.

I was hoping someone here had converted using the 70mm housing and would know what electronics may work. Hopefully I'll be able to get to a jy this weekend and see if I can find something to match up...we'll see.
 

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The Towncar MAF meter is set for the Town car MAF housing. That's your problem, it will read lean as more air is flowing through the larger housing. I'd try to make the Towncar MAF housing work, or find a housing, that is the same diameter, put the Towncar meter in it and that should work.

The other option is to run a truck MAF and EEC that go together. The meter and housing are matched and both are matched to the EEC.

Last option Tweec! it!
 

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Discussion Starter #5
Swat!

Thanks for the input! I've installed the wideband O2 sensor (that you sold me...how long ago was that? ha!) and gauge, which confirms that you are correct - I'm running lean.

I've got an adjustable FPR and have cranked the FP up to about 55 psi, which has helped the lean situation. I also found (an awesome) local junkyard, and grabbed the MAF sensor from a 94 Towncar with factory 70mm housing. The "new" MAF has helped driveability quite a bit - with the previous sensor it would occasionally die/stall in gear at idle, my cruise AFR (with FP cranked) was in the low 12's, but at WOT with would hit the high 13's. With this sensor, it doesn't stall at idle anymore, cruise AFR is in the 13's, and it drops to below 12 at WOT. Much better, but I still have to have the fuel pressure cranked up.

I've been getting code 34, even after replacing the EVP sensor and EGR valve, and I finally realized tonight that I need to get the correct EGR vacuum solenoid. The 86 Bronco used a dual solenoid, apparently - one to supply vacuum to the EGR valve and another to moderate/bleed the vacuum, from what I've deduced. With my setup, the second solenoid was not electrically connected. I see that the 91 TC uses a solenoid with the bleed built in - so I'll pick one up soon and go from there. If anyone has any input on this, it would be appreciated!

Once that's sorted, I plan on rigging up a way to make the 55 mm Towncar MAF housing work with the truck MAF intake plumbing. Although, I'm fairly happy with it as is...aside from needing to have the FP cranked up.

Do you think going from a 70mm to 55mm housing will have an effect on performance? That 55mm housing looks tiny!!!

Engine specs: honed 302, truck/bronco intake, MAF, 19lb 4 hole injectors, shaved GT40P heads, 1.7 ratio RR, mild COMP cam, JBA headers, single 3" exhaust w/ high-flow CAT.

As always, thanks for any input, guys!

-Mark
 

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The EECV programming or strategy to run that engine is looking for the specific MAF that it is matched too. Further more, getting the MAF curve correct is a huge part of tuning. I think it will run better with the stock MAF unless you got lucky. The MAF you are running now would have to be very close to the stock one to be lucky. Your work around with the adjustable FPR is helping but not the best solution. I'd try the 55mm MAF housing and meter that are matched to the EEC's programming.

You can tell much with a vacuum gauge installed in the intake tubing and in the manifold. Which set-up creates more vacuum and then go by seat of the pants to determine which is best. The stock set-up should have enough to handle your changes, Ideally, a larger MAF, and injectors with a tune would squeak-out a bit more power.

I post here a Screenshot of the MAF transfer for a 302 truck and Open loop fuel. The MAF curve is specific for what each MAF meter reads and that is what the EEC is counting on to get the AF ratios correct. You could use the Open Loop fuel table to compare against your AFR readings.
 

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MAF Curve X = Voltage reported by the MAF meter. Y = Kg/Hr.



Air Fuel ratio in open loop when ripping around, at high speed, or under higher load. It should be 14.64:1 otherwise. 11.67 at WOT X = RPM Y = Engine Load

 
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