Jetting and elevation

[tnc110]

Wanting to have a 600+hp fe built. Was hoping to go carburated. I live at 3500ft, but would like to take the car to the coast on occasions. Am I going to have jetting issues? Tune it for sea-level and let it run rich in the moutsins?

[Anthony]

Maybe talk to a local engine shop, dyno tuning shop, and see what they have to say.

I guess the best would be to dyno tune your engine at both elevations, for the optimal jetting. Maybe percy's adjustable jet kit would make it convenient to make adjustments.

https://www.summitracing.com/search/...-adjust-a-jets

But, I think it really comes into play with full throttle acceleration, racing. I'm guessing unless you have a "race" engine, maybe leave it alone?

[Phx Mike]

I am sure the experts here can provide advice on how to optimize your setup and whether to bias it for the altitude or SL conditions, but in general I would not worry too much about a 3500 ft elevation change. Many of us routinely drive our cars between SL conditions and the mountains here in AZ (5-7k elevation) without any troubles. In my younger days we used to drive up to the White Mountains (9K plus) with our carb'd vehicles without any problems, and I know my dad used to drive his t-bird up Pikes Peak with no issues.

We all used to survive just fine in the days before fuel injection!

Good luck!

[Bartruff1]

I have my cars tuned for where I live at 800' and where I do 99% of my driving ....I don't worry about tuning for a occasional trip to the Sea Shore at 0 or a trip over the Cascades at 7000'....or even to Colorado at 12,000 '.

[twobjshelbys]

You're ideally situated. I doubt you'll be racing and if so the story will change. But if you get a good tune for your home altitude it should handle normal driving down and up with no troubles. When I was in school my dad always got the truck rejetted for mountain driving but we were towing a big trailer. I knew a guy in Colorado that just swapped carbs since he goes to sea level often.

[Cashburn]

Best option: https://www.holley.com/blog/post/hol...r_stealth_efi/

[bobcowan]

3,500' change won't really matter. Just put a nice conservative tune at home, and don't be afraid to drop to 0.

Going from near sea level to above 7,000' ASL means the engine will be running fat. For short jaunts, that's not a big deal. But for longer trips it will eventually foul the plugsCars can be hard to start up there, too. Iv driven behind people who live in Denver, and then drive up into the Rockies. Man, that stinks! It can really gas you out. We try to put EFI in the front, and carbs in the back.

If you're concerned about it, consider EFI. If programmed correctly, it will adjust for altitude on it's own.

[olddog]

Originally Posted by bobcowan

If you're concerned about it, consider EFI. If programmed correctly, it will adjust for altitude on it's own.

Let me elaborate a little. Some of the aftermarket EFI setups go to Alpha N to solve issues. Alpha N mimics a Carb and will not compensate for elevation changes. Some of the people with 8 stack EFI look alike systems have said they were using Alpha N. Also huge cam engines often go this route.

Map systems kind of compensate. They check the Map when the engine is started to determine atmospheric pressure. So if you shut the engine off and restart it after an elevation change it is perfectly adjusted. If you do not shut the engine off, the O2 sensors will compensate by trimming the fuel in, slowly over time. However the narrow band that the O2 sensors operate in is only used at idle and cruise, at WOT the O2 is not used.

MASS FLOW systems truly 100% compensate for elevation all the time. Very few aftermarket EFI systems are Mass Flow. Also tuners have a nasty habit of turning the feedback off on high performance stuff to solve some problems.

So EFI can be the solution, but you still have to make sure of what you are installing and who is tuning it. Personally I feel a good EFI system is the best solution, but that qualifier GOOD is important.

PS
There are some MAP systems that have two MAP sensors. One connected to the manifold and another to measure atmosphere. These would not have to be restarted and would compensate very well. The systems that Ford put on the Mustangs in 1986 thru 1988 did not have this. Thought I should correct myself.

[eschaider]

Everything olddog just told you is spot on. There are three very good sources of EFI systems that you may not have heard of. All three have been providing them for years although, some have become generally available only in the last few years.

The first is what you will consider an unlikely source — Ford. Ford spends more money designing the hardware and software before getting to the calibration on one system than most of the aftermarket suppliers combined. Their engine management is very complete but does not offer the failsafes the aftermarket systems do.

A good starting point you might consider is the n/a version of the Ford EFI electronics which they sell through FRPP for Coyote's. This is the link => Coyote EFI System. You can usually reduce the buy price fairly significantly over Ford's MSRP.

To use the system you need to disable the TiVCT in the software (mouse clicking effort) specify your engine displacement and injector sizing you wish to use. The supplied MAF is already specified in the tune.

The second choice you have is the Pro-M Racing injection, <= click here. The Pro-M system is the Ford factory racing EFI of a few years ago, that is built for them by the same folks (Visteon) that build all their OEM daily driver systems. The system is extremely high quality and again a stunning engineering effort and investment, way outstripping most all of the aftermarket offerings.

A nice extra added attraction is that this system will actually build its own base tune to keep you going until you can get to the dyno or get around to doing it yourself. You still have to tell it your engine size and injector sizing and MAF calibration. This is a VERY complete and well thought out system.

The third candidate you should consider is the MegaSquirt Pro package from DIY Autotune <= click here. Many people have overlooked the MS systems because they didn't want to get involved with a 'Heathkit' type project.

DIY Autotune changed all that. They offer a completely built system just like Ford or Pro-M offers but with a stunning array of tuning features. The completeness of the offering is in large part due to the decades of development the authors have put into it. FWIW it is also the least expensive of the three without giving up any capability. An additional attaboy is an extraordinarily good and complete tuning software user interface that is available in either PC or Mac formats.

All three of these systems are Mass Air systems. Ford supplies a suitable MAF with the first choice. The Pro-M and the Megasquirt systems require you to purchase a MAF. The MAF that I use and highly recommend is the Pro-M 92 unit click here =>Pro-M MAFs for pics. The one you want is either the Pro-M 80 or the Pro-M 92, depending on your engine size and anticipated mass air flow. The 92 is usually used on supercharged engines but can be calibrated for lower mass air flows. Pro-M can help you select the proper one for your engine choice

As old dog said their are three primary EFI models. The oldest and simplest in terms of management strategy is the Alpha-N model. The Speed Density model is next and is the most popular today because it is easier to understand and lets the end user fiddle with engine Ve in a Ve table. The problem with the fiddle approach is no one seems to know what their engine's Ve is at 4137 rpm or how it has changed by 5962 rpm.

The Mass Air Flow approach measures, with a calibrated MAF, the actual weight of air being injested by the engine at any point in time and informs the EFI controller so it can adjust the injector pulse width to provide the commanded AFR you have chosen for that operating RPM and load with the ambient air available at that particular point in time.

A nice extra added attraction, that the OP was interested in and old dog already mentioned, is the ability of the Mass Air Based systems to adjust the tune on the fly depending on ambient weather conditions. This is the OEM approach used because they have to meet emissions standards anywhere in the country, at any altitude, and any weather conditions all the time — because it is mandated by Federal law.


Ed

p.s. Almost forgot. If you use one of the iconic and stunningly good looking eight stack intake systems it will be all but impossible to use a MAF based system. At the minimum it will be quite difficult to manage the air into the MAF and then out to the eight stacks.

If that is your intended engine configuration you will be best served with a Speed Density approach that obviates the use of a MAF. All three of the systems I have enumerated above have a mode switch in their s/w and can be operated in Alpha-N, Speed Density or Mass Air mode.

p.p.s When / if you go to the FRPP page with the Coyote PCM, scroll down to just below the picture where it says Overview and then Similar Parts. Click on similar parts. You will see a listing of all the PCM's they sell. The 4.6L 3V unit will save you about $400 and still allow you to specify your engine, injector and MAF calibrations to work with your engine.

An important consideration if you go the Ford route is you will need to spend about an additional $800 for aftermarket tuning software. If you go the Pro-M or Megasquirt route they come with the tuning s/w.

[Phx Mike]

Or, tnc110, if you have a carb just get it set up for where you live and drive wherever you want and don't worry too much about it. The EFI is of course better at optimizing the air/fuel mixture to accommodate changes in atmospheric pressure and fuel properties, but the carb will be fine. I wouldn't sweat it too much unless you are really into maximizing your fuel economy and minimizing CO and hydrocarbon pollution, in which case you have the wrong car!

Most importantly, have fun!