making my own active feul management like chevy

[kanoshee]

i'm trying to figure how to create my own on an 85 ford 302
idk if it's possible i've got the fuel and spark cut off figured out what i can't figure out how to do is release compression on 4 cylinders.
it will be manually activated.
is it necessary to undo compression? i know it will be very beneficial but without it will it work to just cut off fuel and spark? and with this engine being older and not in such great shape i wonder the benefits of creating a v6 would be? does anyone have any experience in this, does anyone have a great understanding of chevy's system?

[c_silva88]

dosn't the have 85 carb? if so how do you plan on cutting fuel to the cylinders? also it wont idle/run right cause the firing order and probably result in worse fuel milage. just to give you an idea pull the plug wires off the cylinders you plan on deactivating and try to start it.

[kanoshee]

no it's fuel injected i'm not sure what or who changed it over or if but it has 8 fuel injectors and i'm going to have it manually switch so when i get up to cruising speed flip the switch to only 4 injectors. which is fairly easy what i can't figure out is how to cut compression to those 4 i assume it would have to do something in the camshaft, does Chevy's release compression? i say release but i truly mean prevent

[2000neon]

Do a search here for cylinder deactivation, it has been discussed before. Simply cutting off fuel will not get any improvement in fuel economy. You will loose a ton of efficiency pumping air through those dead cylinders. The ideal approach is to close both the intake and exhaust valve on the cylinder(s) you want to deactivate. You end up compressing the air in the cylinder on the upstroke of the piston, but you gain some of it back when that compressed air helps push the piston back down.

Also, if you only cut fuel to the cylinder,you will still pump air into the exhaust system,and this extra air be read by the 02 sensor as running lean, so the computer may add more fuel to compensate.

[c_silva88]

imo the cheapest and easiest route to go would either be change to a numerically lower gear ratio or swap over to a straight 6 both are basic bolt ins most of the f150 ive seen with the 302 have 3.55s in the rear end. my straight six came with 3.08s and i recently picked up a complete rear end with 2.72s for cheap. just a few options i figured i throw out there for you

[kanoshee]

Originally Posted by 2000neon

Do a search here for cylinder deactivation, it has been discussed before. Simply cutting off fuel will not get any improvement in fuel economy. You will loose a ton of efficiency pumping air through those dead cylinders. The ideal approach is to close both the intake and exhaust valve on the cylinder(s) you want to deactivate. You end up compressing the air in the cylinder on the upstroke of the piston, but you gain some of it back when that compressed air helps push the piston back down.

Also, if you only cut fuel to the cylinder,you will still pump air into the exhaust system,and this extra air be read by the 02 sensor as running lean, so the computer may add more fuel to compensate.

it doesn't have o2 sensors and thanks which would be better not compressing in the first place or the compression/down pressure?

[kanoshee]

Originally Posted by c_silva88

imo the cheapest and easiest route to go would either be change to a numerically lower gear ratio or swap over to a straight 6 both are basic bolt ins most of the f150 ive seen with the 302 have 3.55s in the rear end. my straight six came with 3.08s and i recently picked up a complete rear end with 2.72s for cheap. just a few options i figured i throw out there for you

imo? wtf are they're so acronyms? lol (yes i did that on purpose) and it's 4wd so if we lower the rear end won't we have to lower the transfer case?
and we're definitely considering a new transmission no overdrive is killing it. but i don't really want to go chopping this truck up to a highway going thing it's a beast of an offroader and we use it for that not just fun we work alot back in the woods and she's really, really good there but every now and then we gotta make long highway trips and the drive to town is pretty long it's self what i really need is another truck lol but ain't got the money for that right now and i just think it'd be one hell of a self accomplishment to create my own system for this. i mean, we pull trees out and everything so straight-6 is probably not a good idea either but, as low as she is geared it would probably work out.

[c_silva88]

imo- in my opinion. i didn't realize it was 4wd if you were to change the rear you'd have to change the front gears also so the cost would be more. as far as comparing horse power and torque granted these are newer engines but you get the idea horse powers higher in the 302 but torques close enough to not notice but in the 4.9 its a little lower rpm.
1988-91 4.9L EFI - 150 hp at 3400 rpm, 265 lbft at 2000 rpm
1988-91 5.0L EFI - 185 hp at 3800 rpm, 270 lbft at 2400 rpm
a transmission swap would be a good upgrade there are 2 options for a 5 speed there is the zf which has a low first gear good for towing found in f250s and 350s and then there is the m50d-r2 which is a lighter duty 5 speed found in newer f150s. both have overdrive and give you more gear options to keep the truck at the optimal rpms.
ZF S5-42 Close Ratio:
R: 3.79

1: 4.14
2: 2.37
3: 1.42
4: 1.00
5: 0.77

ZF S5-42 Wide Ratio:
R: 5.24
1: 5.72
2: 2.94
3: 1.61
4: 1.00
5: 0.76
M5OD ratios:
1st 3.90
2nd 2.25
3rd 1.49
4th 1.00
5th 0.80

[kanoshee]

4.9 is that the size of the l6?

[kanoshee]

and wow that zf is really what i need LOW first gear with decent over drive not sure of my current ratios i just know they are all low and 4 is drive how can i determine the difference on the outside between close and wide, i think i prefer wide.