Turbo Charging a '94 F350 7.5L

I am looking for any info from you guys about undertaking this. The truck is a strong running 460 with a E40D trans. I posted this about 9-12 months ago on the other site but have not been able to find it. I need to know the pros and cons of this. I am also wondering how much boost and the size of the turbo, for the RPM range it will opperate in. Now the truck has 4:10 gears but I am switching it to 3:55 for better fuel milage. The purpose of me wanting to put a turbo on is to get better pulling power and milage, this is not a race car. I run with the 3:55 gears daily around 1600 - 1900rpms @ 70mph, I have very rairly seen 4Krpms. I am working on setting this truck up for long hauls, being we are racing this season in Idaho and Washington. With the expected gas cost increase I need the best milage possible. Now if it jumps up in power from the 285hp and 425ftlbs that will be great as well.

Thank you
Jim
928-219-4929
eperformancemarine@yahoo.com

A turbo won't help your mileage. W aren't talking about a diesel here.

EVE wrote:A turbo won't help your mileage. W aren't talking about a diesel here.

Nope it is a 7.5L/460 ! Now why would it not, as you would have more power in all gears? This would allow me to stay in 4th/OD while climbing a hill with a load, in turn better milage. Now it seems that having more power would use more fuel, but if you don't have to use more throttle you could get better milage right ?

I have never heard of a turbo conversion that did not get better mileage. you would need to discuss your wishes with a reputable turbo dealer for specs on the turbo you need. what you would be looking for would be more of a diesel type turbo than one like on our ride which is intended for high rpm use. good luck.

I dont see how mpg could possibly improve. Your effiency (Brake Specific Fuel Consumption, BSFC) will probably improve but you have to burn more gas when you put in more air at any rpm.
You could train yourself to use the higher gears and suffer the low power to improve mpg.

The turbo is like artificial cubic inches and more C.I. burns more gas.

AK wrote:I dont see how mpg could possibly improve. Your effiency (Brake Specific Fuel Consumption, BSFC) will probably improve but you have to burn more gas when you put in more air at any rpm.
You could train yourself to use the higher gears and suffer the low power to improve mpg.

The turbo is like artificial cubic inches and more C.I. burns more gas.

I don't follow your reasoning. Some of what you are saying is true, some is true but not applicable, and some is wrong.

JR Performance Motorsport wrote:

EVE wrote:A turbo won't help your mileage. W aren't talking about a diesel here.

Nope it is a 7.5L/460 ! Now why would it not, as you would have more power in all gears? This would allow me to stay in 4th/OD while climbing a hill with a load, in turn better milage. Now it seems that having more power would use more fuel, but if you don't have to use more throttle you could get better milage right ?

You won't have more power unless your in boost. It will act just like a N/A engine until the boost comes on and if you want to tow a trailer up a long hill with boost then good luck and I hope you run race gas. Another problem with it is that you will be running smaller turbos to get it to spool at a lower RPM and that's going to make your IAT's even higher and cause detonation that much easier. Diesels like boost because it cools down the exhaust gas and makes the fuel burn more efficiently. They benefit from more boost up to a point. If your EGT's on your diesel are high throw a bigger turbo on it and it will cool them down and fuel mileage while in boost will improve. This logic does not work with a gas engine. Your best bet is to lower RPM's as someone else stated above. Look into a gear vendors overdrive.

whatbumperu wrote: I don't follow your reasoning. Some of what you are saying is true, some is true but not applicable, and some is wrong.

What I'm saying is, Your engine will become more efficient at making power, (HP per CI). But at the cost of more fuel. The only way I see that you could improve MPG is if the turbocharger was going to correct a rich condition, which it will not IMO. Fuel + air in = power out. Not just more air. You still have to maintain an air/fuel ratio, so more air in = more fuel in.

I'm not going to claim to be an expert but I think I'm giving a very basic answer to a very complex question. If I'm wrong feel free to correct me.

I see no reason why mpg would not increase with the turbo installed if the right foot is applied the same.

The benefit of the turbo is that you can switch from 4.10s to a 3.73 gear and still pull a hill the same.
Turbos help build low rpm torque, so those deep gears are not necessary.

I just put the 460 out of my race car into my '84 F350 Crew Cab and had thought about mounting a turbo in the bed of the truck.
All that engine needs is 5-6 lbs of boost.
Then I could swap the 4.10 Dana 60 for a 3.55 Sterling 10.25 rear.
That would drop my cruising RPM by over 13%.

Heres a rpm/mph calculator. I'm not sure what the OD ratio is but 4.11 to 3.55 will only change rpm roughly 300-400 rpm at any given speed

http://www.bgsoflex.com/rpmmph.html

Lowering the rpm without a turbo will lower fuel consumption but with the added fuel for 5-6 # of boost you might break even, more, or less. It all depends how much more fuel it takes to keep a decent A/F ratio. It will be interesting to know how it turns out.

Well I am doing the gear swap/rearend from 4:10 to 3:55, this allone should get me at least 2mpg better. Now the turbo should imo help me pull the gear without dropping a gear going up a hill. I am going to do a throttle body switch as it seems they use the same ones on the 5.0, 5.8 & the 7.5L truck engines. I saw some where that they make a larger one and as we all know 460s/BBFs love big carbs. So more air in with this may help. I am going to get some baseline info first then make changes. I am going to try and document everything I do on this and see where it leads.

Thanks for all the info.

just put a Blower on it, instant trq.

My opinion is worth twice as much as you paid for it:

Simply adding a turbo to a NA 460 cid engine will not increase fuel economy. In fact, a turbo decreases BSFC. It is possible that changing the combo (gearing, trans, tune, ect) may net enough improved economy to make up for the decreased efficiency, though.

Now, IMHO, the reason you see turbos used is that you can put a turbo on a smaller engine and get comparable hp/torque to a larger cid engine. The fuel economy of the smaller, turbocharged engine may get better fuel economy than the larger, NA engine even though both may have the similar hp/torque #'s. So, a fairer question might be, "Will a turbocharged 460cid get better fuel economy than a NA 557 cid engine?"

Have a good day!
Michael