It's a subjective measurement ... depends on gearing, TC stall speed, tire size, shift points, etc. If he's in 4-lo and first gear ... he's probably going to have it red-lined the whole time.

 

ah cool. so just wondering, how do most people find themselves picking then 52mm for the 5.9 instead of the 50mm? Because I mean like for normal driving i wouldn't think you'd be in the high rpm range ya know, just wondering why that would be a better choice for some.

 

I think most people want to feel themselves shoved back in the seat when they floor it. The internal combustion engine is a big air pump ... the more air you take in (and expel) the more power you're gonna make. Bigger holes in (and out) makes for more air pass through. That's a VERY simplistic explanation.

Of course, you can get TOO big ... that's why the 50mm is about right for the stock 318. Just like you can have too large of a diameter on the exhaust.

 

yeah that helped out, I'm just stuck on whether I want to get a 50mm or a 52mm for my 5.9L. I mean I don't often go above 2500 RPM as a daily driver, but every now and then I would want some nice power. Heres a question, from a stock TB now, no matter which I got, I would still have an increase in both low end and high end right? No way I would be losing any with either choice?

 

The idea of going to the Fastman is to put a bigger throttle body on the engine. I don't know what the stock TB throat diameters are but I think that as long as you're going to replace it, go big. You'll probably be thanking yourself later if you do any other serious mods. You're not going to KILL the low end ... just move the power band up into a somewhat higher RPM range.

 

Yeah I do have plans for stuff in the future like headers, but I do like my low end now because im running 285 with 3.55, like you, you would probably agree the truck feels sluggish. I have people passing me out all the time from lights and such because I can't keep up unless I mash it to get it to shift. Gunna have to think about it more before i go ahead and order one.

I just don't want to get the 52mm and have the truck feel the same way during every day driving and only open up when I floor it.

 

Actually, I'm pretty pleased with my performance. I *NEVER* get taken at a light ... and I take off on maybe 3/4" of pedal.

Didn't we determine that you had the death flash ... or was that someone else?

Anyway ... if you're looking at headers in the future ... a 52mm is the call for sure.

 

must have been someone else with the death flash, no sticker on my pcm, unless its hidden on the other side and i dont know about it [:@]

do you have a fastman atm? maybe the mopar pcm/91 octane gas helps you out in those situations. whats your mpg usually? mine is usually around 11-12.5

the point of getting new headers would also be to increase air flow right, anything else? off topic but how would they affect exhaust tone?

 

I actually went back to stock on the PCM (need to update my sig). Didn't see that much of an improvement ... certainly not enough to justify paying for 93 octane. No, Fastman either. Motor is pretty much stock. Mileage was 11.5 for years ... jumped to 12.5 this summer. I figured it was because of the ethanol they started puting in the gas here.

About the headers ... yes, they're to help the motor breathe. Good compliment to the 52mm TB. No information on sound ... I only had one vehicle with headers (FJ-40 Land Cruiser) and I bought it with them installed.

 

good luck... i dont think a couple bolt ons are gonna be helpin you take some 600+ ft lbs (stock) diesels in a pull competition....