Is the 80 mm Pro-m mass air too big??

87'GTstang · May 17, 2004

Couldn't have said it better myself

You're simply basically throwing money out the window because you want it now. There just isn't much sense in spending the $300 (estimate) or whatever deal you are getting for a setup you are simply "guessing" will work. If you're trying to do a dual turbo setup AND nitrous or anything drastic like that, you may find yourself in need of a more capable setup in the aftermath anyway.

86Cobra · May 17, 2004

Michael Yount said:
That's not internet myth. Could they have tuned their way around it? Perhaps - but they ultimately decided metering small amounts of fuel was more easily and accurately done with a smaller injector.

I am admittedly pretty clueless when it comes to any modular motor Mustang so I don't have any idea what the answer is there. I'm sure they could have had multiple reasons for that choice.

For an example in the other direction, why did Ford put 24s in the 93 Cobra? That's a VERY mild motor that you would probably recommend 19s for. They used 24s and they of course worked fine.

Also, how about the stock 5.0? I see 19s getting recommended for motors up to 300 hp all the time on the net. If that's the case then why didn't Ford use something smaller in the 5.0? If 19s are good for a 300 hp motor then surely they're "too big" for a 225 motor, right?

Ok, sarcasm off. My point being, you can find production examples on the other side of the argument too.

As for metering small amounts of fuel, IMO people under estimate how precise modern fuel injectors are. My buddy runs 72s (yes 72s) in his turbocharged 316. The car idles like a stocker and is not rich at all. Of course this is an extreme example, but you wouldn't believe this was an almost 800 hp car listening to it idle. This is what most people don't get - with a good meter and, better yet, a custom chip/tuner, there is no downside to a larger injector.

Michael Yount said:
Now, will going with 30's in this case instead of 24's cause idle or low rpm problems? Probably not if the meter is calibrated correctly and has the right transfer curve - I think that's what you were alluding to. Does the engine with the set up described need 30's? No, 24's are more than sufficient.

I agree. Either one will work fine.

Michael Yount · May 17, 2004

Mod or pushrod - the injector dynamics are the same. It's simple physics - to get a very small amount of fuel out of large injector takes a very short pulse width - and control gets less accurate at very large and very small pulse widths. That's not rocket surgery.

Regarding the Cobra, as I understand it, the engineers became concerned that under high speed (as in flat out at top speed) conditions for long periods of time, the motor could outrun the the 19's - they bumped up to 24's to eliminate any concern. It would be a great question for the folks whose meters you encouraged Andy to use - ProM (I run a ProM too). It's their website that allows up to 425 crank HP for the 24's. And as I understand it they are intimately involved with Ford and other manufacturer's maf design.

The solution still seems straightforward to me - there's no performance benefit to running any more injector than you need. And once you start to get above 30's, there is often special tuning that's required to solve a variety of issues - low speed control being one that often surfaces. My point is simple - if you don't need the extra size anyway, why tempt fate?

86Cobra · May 17, 2004

Pro-M makes nice meters but their tech frequently leaves a lot to be desired. For example, they used to (maybe still do) have a tech article on their site supporting the dumbest internet myth of all time...yes...the famous "distributor off a tooth" myth.

Most knowledgable tuners will not recommend running 24s at 400+ hp.

86Cobra · May 17, 2004

Michael Yount said:
The solution still seems straightforward to me - there's no performance benefit to running any more injector than you need. And once you start to get above 30's, there is often special tuning that's required to solve a variety of issues - low speed control being one that often surfaces. My point is simple - if you don't need the extra size anyway, why tempt fate?

It's a "glass half empty or half full" question. I see it the other way. When choosing between two injectors sizes, I always pick the larger since there's no downside to running the larger injector. Then I have more room to grow (I upgrade my setup relatively frequently) and a little factor of safety.

Of course, there's usually more than one "right" answer and that's certainly the case here.

Michael Yount · May 18, 2004

I think we're reaching alignment 86. "dumbest internet myth of all time...yes...the famous "distributor off a tooth" myth." - I'm with you there!

Half full/half empty is a good analogy. With the correct tune/meter set up - as long as the fuel needs can be met flow-wise, there are a range of injectors that can do a reasonable job. I think you tend to the 'why not go one step up for safety and future' side, and I tend to the 'don't go any bigger than you need to' side. I can live with that difference.

QDRHRSE · May 18, 2004

I know I'm late but I think an 80mm Mass air is too big for that combo as is. It will only help top end performance and may even hurt low end drivability on the street. You can get away with a bigger injector but in a lot of cases it makes tuning very hard- especially if you have a street/strip car. Then, couple the oversize mass air and injector combo, unless you are the master of all tuners, and you will end up slower than you were to begin with.

Just my opinion. I agree to disagree.

Michael Yount · May 18, 2004

qdrhrse - howdy! Why do you think it will hurt low end drivability?

86Cobra · May 18, 2004

Actually, the Pro-M 80 should help driveability because it's a much more accurate and better designed meter than the 75mm Bullet. The size difference won't affect driveability.

Michael Yount · May 18, 2004

"The size difference won't affect driveability." I agree.

86 - several times you've mentioned the quality of the 80 vs. the slightly smaller bullet. Can you elaborate - what makes it better, more accurate, etc.? I get to learn a little something here!

86Cobra · May 18, 2004

The Bullet has a crappy flimsy sampling tube. The 80 has a much more solid precise sampling tube. Also, on the shorty 80 the sampling tube extends into the conical filter allowing it to get a more accurate sample versus a tube that only samples the flow at the top of the meter housing. This eliminates the need to "clock" the meter.

It's kinda hard to describe, but if you ever have the opportunity to compare them side by side you'll quickly pick up on the differences.

The 80s used to be $275+ but Pro-M is selling them for $199 with filter. That's a great deal for a great meter.

A good source for a lot of mass air meter experience is the Tweecer board:

http://tweecer.oplnk.net/

The Pro-M 80 and the 90mm Ford Lightning meter are by far the favorite meters of the Tweecer geeks. The problem with the Lightning meter is that its transfer function maxes out around 500 hp. Pro-M sells new Lightning meters for $115 but you need a filter to bolt to it (~$50) and the wiring plug/pigtail (~$25) so the 80mm Pro-M at $199 with filter and individually calibrated is a great deal.

Michael Yount · May 18, 2004

"the sampling tube extends into the conical filter " -- ???? Confused. My conical filter is in a cold air box with 2 mandrel bent 90 degrees ells between it and the maf. How could the sampling tube reach into the filter?

Sounds like the filter is designed to bolt to the maf -- which requires mounting the maf along with the filter in a location where it can pick up cold air - or fabbing some piping in between.

I think I've seen the meter you're referring to - don't think I'd conclude there are as much of a difference between the two as you've concluded, however.

86Cobra · May 18, 2004

Yep, the filter bolts to the meter as it does on the 90mm Lightning meter. So it won't work on some applications w/o some fab work.

Michael Yount · May 18, 2004

Yeah - I've got a buddy with that meter set up that's chasing detonation issues. May be due to mismatched calibration on a used meter, but it doesn't help (ping or power) that he's pulling hot air in from under the hood.

86Cobra · May 18, 2004

I guess this would be a discussion for another time and place, but I run an open filter under the hood and have never had any problems with it. I also have a cowl hood and a very open engine compartment that gets a lot more air flow than the usual cramped Mustang engine compartment. That probably helps.

Sounds like a calibration issue to me.

87'GTstang · May 18, 2004

86Cobra said:
I guess this would be a discussion for another time and place, but I run an open filter under the hood and have never had any problems with it. I also have a cowl hood and a very open engine compartment that gets a lot more air flow than the usual cramped Mustang engine compartment. That probably helps.

Sounds like a calibration issue to me.

It's just the whole philosophy that cold air is denser so more oxygen molecules can be packed in a specific amount of space as compared to much hotter air. If you have a very open engine bay setup then you probably won't notice but such a difference, but there probably would be if you were sitting at idle in traffic. Either way you like it, the combustion cycle doesn't really like excessively high temp. intake charges of air.

86Cobra · May 18, 2004

87'GTstang said:
It's just the whole philosophy that cold air is denser so more oxygen molecules can be packed in a specific amount of space as compared to much hotter air. If you have a very open engine bay setup then you probably won't notice but such a difference, but there probably would be if you were sitting at idle in traffic. Either way you like it, the combustion cycle doesn't really like excessively high temp. intake charges of air.

Yeah, the theory is pretty obvious. It's mainly a question of how much cooler the air you're pulling with a kit really is. In my specific case, I don't believe there's much, if anything, to be gained by putting the filter in the fender. Other experiences may vary.

QDRHRSE · May 18, 2004

Michael Yount said:
qdrhrse - howdy! Why do you think it will hurt low end drivability?

In the past I have experienced a part throttle bog with really big air meters with NA cars. I have seen big top end gains with running a really big meter but at the same time the cars always seemed lazy down low. If your racing I guess it doesn't matter. In fact if your car has a lot gear it doesn't matter either because you're alway turning a lot of rpm. I'm reaching here but I think it creates a temporary lean-then rich condition when you give the car a lot of gas while you are moving slow at low rpms. Like I said- its a driving (drivability) problem. Stuff that happens in traffic might not happen at the track.

04sleeper · May 18, 2004

The 80 MM Pro-M is not to big even for a bone-stock motor. It will not give any driveability problems. I have been running one on my car for 4 years now and I got it when my car was bone-stock. It picks up power all the way through the RPM range. I dynoed my combo several times because a friend had a shop with one. I have several meters including stock ported, C&L, 75 Bullet and the "Infamous" 77 MM Pro-M. The 80 is the most vesatile and is the best on the market!

Michael Yount · May 18, 2004

86 - even with air flowing through the compartment, the air coming off the radiator is at least in the 140-180 range depending on your t'stat; that's best case. The engine is a huge mass radiating at 200-220F. Headers radiating at 600-800F. You've got the potential to access intake air that's AT LEAST 50F cooler (I'd say more like 75F cooler, maybe 100F cooler on a really cool day) than what you've got now. That's a 2.5%-5% increase in HP across the board that's just a fenderwell away based on the 50F differential; it could be as much as 10% on a cool, 100F differential day. That's a freebie man - you're in denial if you think it's not impacting your output.

Is the 80 mm Pro-m mass air too big??

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