QUIETEST? I didn't want to listen to a drone and appretiate a quiet system, especially on long trips pulling a load. For that reason, I had Jardine put 2 mufflers in series. They said it wouldn't reduce performance any - just added $60. It is as quiet as the factory system, however the pitch seems a little lower. I love it. My only disappointment is that the EGTs didn't drop as much as I had expected.
Steve

 

I have the warpspeed 4in exhaust and love it. Very simple install (once you get rid of the stock system). I have mine straight piped and there is a slight to medium drone at highway speeds. If you plan on leaving the muffler on, then I don't think there will be a drone. Great price and great product.

 

Well, if you have 1:1 pressure across the turbo, you'd have NO flow, wouldn't you? Flow only occurs when there is a difference in pressure, because flow is nature's attempt to eliminate a pressure difference.

Nature abhors a vacuum,as they say. You are correct that the pistons are forcing it through, but they do that precisely by eliminating a 1:1 ratio.

I would tend to agree with Rowland that backpressure is cumulative. IOW, the backpressure contributions of each element in the exhaust are separate entities. So the turbo's backpressure is a function of the turbo. The exhaust backpressure is a function of exhaust, etc. So you can't change the turbo's backpressure by changing exhaust-- you change the turbo to do that.

I think RJ is right to say that TIP will ALWAYS be more than TOP, simply because TIP is the SUM of TOP PLUS the resistance of the turbine. It's cumulative.

So, TIP *must always* be higher than TOP.

I'd also suggest that exhaust should be matched to turbo size. Because as the turbo gets bigger (and therefore offers less restriction), then the restriction of the pipe becomes a higher percentage of the overall restriction picture. It's a higeh disadvantage that exhaust pipe tubing is generally only available in increments of a half inch or full inch. The flow rate increase of 5" to 4" is considerable-- almost double.

I'll close by stating my belief that high EGT is MUCH more related to turbo sizing than exhaust size. I believe that an HX40 with a stock exhaust would lower EGT more than an HX35 can with a 4" exhaust.

jlh

 

When does 4" over stock enhance performance and what is the difference of Catback vs Turboback?

 

Yes, but your FACTORY exhaust will keep TOP well below TIP even with a HUGE single charger.

For reference, the stock turbo is roughly equivalent in flow to a 3/4" pipe. Makes the stock 3.5" exhaust look downright huge.

If your boostP ratio is getting far above 1:1, I can ASSURE you, that it's not because your exhaust AFTER THE TURBO is too small.

I'd match exhaust pipe to turbo. Twins are best with 5"-- most big turbos need 5" outlet anyway.

4" will accomodate any single on the market with relatively insignificant backpressure due to exhaust pipe flow.

To put numbers on this: The rule of thumb (per David Vizard) is that exhaust will frrely flow about 115CFM/sq in of sectional area.

Thus, 4" will flow 1445 CFM. That's a LOT of air.

4" is fine even with a somewhat small set of twins, running a reducer from 5" outlet to 4"pipe. Doesn't cost much in the way of HP or cooling at all.

IMO, you'd have to be running some rather large twins (HT4C or bigger on bottom) to even approach NEEDING 5".

5" will freely flow 2258 CFM. That's plenty to supply an ISX at 600hp 14L displacement.

jmo

 

Thanks fellas for the debate and excellent info. In case your curious, I ordered a 4"

 

The 5" straight pipe I have on the truck does not drone at all. Is that because of the size of the pipe? I do not not know. It is very mellow sounding, unlike a 3" straight pipe. Pulling a load with the windows down and going up a hill at slow sppeds with a wall or embankment on the exhaust side of the truck then DANG shes loud. But running down the freeway at speed no drone at all and can carry on a normal conversation. The big fat pipe also looks cool IMHO. I only paid $125.00 for the system but was on the road for 5 hours to get it. I was bored that Sunday and went for a drive. Gas was around $2.00/gal and was able to fit it in the Honda Accord that gets 32mpgs. For that price why wouldnt I install it?
You can get a 5" system here for less than most places charge for a 4". MOTOBLUE™ MONSTER 5-INCH EXHAUST SYSTEM $349.00
http://www.rpmoutlet.com/dodgecdd5.htm
I also ordered the Stainless tip and man is it nice.

Dusty

 

Now you show me that after i already ordered. I sure never seen a 5" for that cheap. Dusty, wanna sell me yours for $125??

I know, I know I pussed out...

 

Ha ha ha ........Glad you said it, not me. You cant go wrong with a 4". Thats what I would have run if I didnt get such a good deal on my 5". I dont have any regrets yet with the 5". Are you gunna straight pipe your 4" or are you going to let Forrest down and be Mr. Mellow Evil ?

 

I've been looking for this kind of info!!