How much hp can OBD 2 Explorer handle stock?

[rjrobin2002]

How many upgrades like high flow heads, cam, and headers can the OBD 2 Explorer efi handle with stock injectors and computer?

 

[sanndmann3]

I can't give you a number but staying with stock injectors would probably be the limiting factor. I have 351w with edelbrock Al heads and itscreams. Tune provided by EFI Guy. 34 lb injectors though...

 

[Broncobowsher]

The injectors (and maybe the MAF) are the limiting factors.

With the right parts the ECM will support over 1,000 HP (with a proper tune)

 

[rjrobin2002]

So a 300hp 5.0 would need a bigger injector set and maf and a tune to make it all work together?

 

[JSmall]

I’m curious of this as well

 

[EFI Guy]

There really isn't any limitation to how much HP it can handle. There are limits to how much air it can calculate, which in theory would limit HP, but you can scale the entire tune if need be. So with the correct parts and tuning, anything is possible.

I recommend 24# injectors for 300 fwhp. However, the 99 and later with the returnless system is just fine for 300 because the little injectors flow just about equal to 24lbs at the higher pressure. I'd have to do some math on the MAF to find the limit, but the MAF can be changed and tuned for as well. I believe there are a couple people on here using the stock Explorer MAF on warmed up 351s so it should be fine.

The biggest hurdle is cam selection. Too much valve overlap will create a false lean condition at lower idle speeds, and possible surging, bucking, etc... So, you either need to increase idle speed or force open loop at idle. Higher idle speed is typically only a problem on a c4 with a low-speed stall converter, other than that, it's not too annoying.

Forcing open loop at idle keeps the computer from adjusting fuel based on o2 feedback, so I don't like to do it on on a typical cruiser or crawler, but for a drag car, dune runner, or mud drags that's usually the best method. With enough tuning, you can still be happy with a larger cam, but for the way most people drive their Bronco's, it's best to just keep the cam mild.

If you're thinking about building a pretty hot motor, call and talk to me first about parts selection so you don't throw money after parts that you won't be happy with. I won't mail order tune something with a very hot cam, but I still remote tune them.

 

[rjrobin2002]

Good info, thanks.

 

[Broncobowsher]

I was surprised that the over-pressurized smaller injectors were that capable. The back of the head math was telling me that they would come in about the same as the bigger 19s.

 

[JSmall]

Gary, I am about to take my engine to the machine shop so this topic is relevant to me right now. You tuned my PCM already so I was going to go with a stock build/refresh for the most part because the Explorer motor will be so much better than what I have now that I didn't feel any extra power was going to be needed.

I plan to replace the cam with the Comp Cams 35-349-8 or 35-308-8 on your recommendation that I read somewhere. Could a nice aluminum head be paired with that and still be able to use the stock tune and injectors? Help me build my engine ;D

 

[jbawall]

I am in the exact same boat as jsmall, I would like to know as well.

John

Gary, I am about to take my engine to the machine shop so this topic is relevant to me right now. You tuned my PCM already so I was going to go with a stock build/refresh for the most part because the Explorer motor will be so much better than what I have now that I didn't feel any extra power was going to be needed.

I plan to replace the cam with the Comp Cams 35-349-8 or 35-308-8 on your recommendation that I read somewhere. Could a nice aluminum head be paired with that and still be able to use the stock tune and injectors? Help me build my engine ;D

 

[EFI Guy]

Gary, I am about to take my engine to the machine shop so this topic is relevant to me right now. You tuned my PCM already so I was going to go with a stock build/refresh for the most part because the Explorer motor will be so much better than what I have now that I didn't feel any extra power was going to be needed.

I plan to replace the cam with the Comp Cams 35-349-8 or 35-308-8 on your recommendation that I read somewhere. Could a nice aluminum head be paired with that and still be able to use the stock tune and injectors? Help me build my engine ;D

Both of those cams usually do ok on a stockish tune with stock heads. The 308 has more lift, the 349 has more duration. I do typically bump the idle speed up a little with the 349. It has done pretty well with aftermarket heads as well.

However, I had a local guy using a set of Procomp heads that it didn't want to idle well with and had to do quite a few tweaks to the tune and raise idle speed up to ~850 before it would purr. So I'm sure port velocity is a big factor in that.

If you're going aluminum heads that can handle more lift than the Gt40's then I'd probably go with the 308 cam. Or, talk to a custom cam guy that understands EFI, low-end torque, and heavy Broncos.

If your computer is set up for the P heads, then it's probably best to send it back to me once you know exactly what you are going to run. The timing tables for the P heads are very conservative and most aluminum heads will take much more aggressive spark advance (assuming compression is the same). So you may be lacking some power potential if you make the switch and do not tune for it.

As for injectors, it's best to figure out the rest of the build first and decide what kind of power you'll be making to figure out the injector size required. Or, just bite the bullet and go with Siemens Deka 60's and never worry about them again. Just don't buy aftermarket injectors that there isn't any Ford specific tuning data for.

 

[JSmall]

Both of those cams usually do ok on a stockish tune with stock heads. The 308 has more lift, the 349 has more duration. I do typically bump the idle speed up a little with the 349. It has done pretty well with aftermarket heads as well.

However, I had a local guy using a set of Procomp heads that it didn't want to idle well with and had to do quite a few tweaks to the tune and raise idle speed up to ~850 before it would purr. So I'm sure port velocity is a big factor in that.

If you're going aluminum heads that can handle more lift than the Gt40's then I'd probably go with the 308 cam. Or, talk to a custom cam guy that understands EFI, low-end torque, and heavy Broncos.

If your computer is set up for the P heads, then it's probably best to send it back to me once you know exactly what you are going to run. The timing tables for the P heads are very conservative and most aluminum heads will take much more aggressive spark advance (assuming compression is the same). So you may be lacking some power potential if you make the switch and do not tune for it.

As for injectors, it's best to figure out the rest of the build first and decide what kind of power you'll be making to figure out the injector size required. Or, just bite the bullet and go with Siemens Deka 60's and never worry about them again. Just don't buy aftermarket injectors that there isn't any Ford specific tuning data for.

Thanks Gary! I’m leaning towards a stock rebuild with the stock P heads. Going that route I know everything will work together and I’ll have a nice reliable build. I want the extra power for one week a year while I’m out in the dunes so it’s not worth the hassle of trying to increase the HP just for one week.

I’ll see what the builder thinks and if I need a cam or any other parts replaced I will make a decision at that time.