If I recall correctly, its 50mm tapered to 48 or 47. Thats why 50mm is supposedly easier to do than the 52, because its more about just making it straight than expanding at all.

I had the 52mm Fastman on my 2001 Ram back when I had it. 5.9L with 3" single exhaust, Volant, SCT, and modified intake (runners cut down, plenum fixed). The 52mm was almost too much for me, especially without the SCT. You did gain some power on the highway, but you lost a little low end.

Unless you plan on heavy modifications down the road, a 50mm would probably be good for the 5.2 or 5.9. Especially if you want to keep more low end grunt.

 

^^^ Yep yep, even with some bigger mods you still lose lower grunt with the 52mm, get above 4000rpm and thats a diff story as you said.

 

Put me down for purple... I want the fastest ones

 

I have a 52mm TB on a 5.2, and agree that you do loose bottom end.
Once over 2000rpm it starts coming to life, and as the revs rise, the more get up and go you have... For now, I've just had to change my driving style a little to compensate.

I've got the intake side opened up, and I'm now about to open up the exhaust side (LT's and 3" all the way back)... hopefully this will regain a little of the lost low end.

Later I'm going with H&S1.7's to finish the bolt-on breathing upgrades.

As a side note; Some of my bottom end loss could be attributed to the shorter runners of the FI Airgap, and not solely because of the 52mm TB.

 

I think you will find out that the lt will do just the opposite of what you are thinking. The 1.7 will help a little bit. The F1 is a dual plane intake in reality you should gain lower tq not lose it, the short intake runners should have helped. The M1 has some long runners on it and it a single plane intake but not like a high rise intake thats for sure. The longer the intake runners puts the it in the higher rpm to make hp. For you to gain back what you lost and more it would take a cam swap, you might look into that area.

Not trying to be a jerk or anything just posting what I have experienced myself.

 

Actually, longer runners give low end torque. Look at the GM TPI system. LONG runners, and GOBS of low end torque.

 

I did not no we were talking GM stuff on a Dodge forum. That setup has more to do with the plenum size over the runner length. Wtf do I know maybe it time for me to move on to another forum.

 

The WEIGHT of the vehicle plays a significant roll in the correct size of the throttle body.
Running a 52mm TB on a Dakota R/T regular cab is alot different than running one on a Ram 4X4 extended cab. This is something that the Fastman and a few other TB modifiers fail to consider when recommending the TB for the engine size alone. Another thing to consider is the actual use of the vehicle, the gearing, as well as the future mods that are planned.

 

He respectfully disagreed with you, and you are free to refute his information with facts. Tell him why he is wrong. Don't whine and moan about it.

 

I certainly would not take it that way... honest comments based on first hand experience is exactly what I want.
Your experience may or may not be the same as the next guys due the combination of other mods, but it all gives me good info to evaluate what path I'll take.

I knew I was going to get some low end loss from what I had read here, but did not know how much or what that would practically feel like in my situation.
I don't tow or off-road, so a little loss in bottom end pull didn't seem like a big deal... but I now realize that my driving style with a stick does seem to keep me in the lower rpm ranges than the auto guys see... for now I just run higher rpm before shifting and I'm well in front on power from where I was stock.
I'm hoping the scavenge from the LT headers will help.

The H&S1.7's are planned when I get the cash saved up.
A cam of some sort has been considered, but I don't think that will be any time soon, due to the teardown needed... this is my daily driver (has been for 15˝yrs).
Cam suggestions are welcome though.