1 7/8" LTs with a 2.5" Y Pipe, Negates Low End TQ loss??

tstar · Jul 1, 2015

A bit disgusted with the cost of ARH and SW LTs I contacted JBA to see if they are ever going to offer 1 3/4" LTs for the 5.,7 and here's my answer;

We are only going to offer the 1 7/8” version of our Long Tube header. If you need any additional info please let us know and if you are worried about low end TQ loss then build a 2.5” Y-Pipe and you will have no loss.

Now, I'm no exhaust engineer but I don't believe simply necking down the Y pipe is going to mimic 1 3/4" primaries... OR am I wrong???

Tim

Dubstep Shep · Jul 1, 2015

Nope. They're full of **** more or less.

The way scavenging works is that the previous exhaust pulse pulls a vacuum behind it. It does that because it has mass and momentum. That vacuum sucks the exhaust gasses out of the cylinder. Your primary size is absulutely critical for that to properly work.

tstar · Jul 1, 2015

Precisely my understanding, thanks! 1 7/8" I'm assuming are too large for the 5.7 HEMI and will slow the exhaust pulses reducing scavenging and making the engine work harder getting rid of that crap???

I'm not intimate with the 5.7 HEMI but I know in my 99 Vette, 1 7/8" primaries were too large for the stock heads and cam. Same deal here I guess...

So ARH or SW are the only options available in 1 3/4" huh???

Tim

HammerHead · Jul 1, 2015

Kooks has 1 3/4 now.

tstar · Jul 1, 2015

Thanks! Just checked that out and you have to use their Y Pipe, $1,700 total before shipping...

I need another job!!!!!

Tim

MyOhFive · Jul 1, 2015

Not the first time or place I've heard this. Haven't tried it myself tho.

charonblk07 · Jul 1, 2015

That's one of the more stupid things I've heard in a while. Let's only offer primaries that are too big for 90% of people who will buy them then tell then to add a major restriction to their exhaust so it'll bottle neck at higher rpm, genius. 1 7/8" primaries is too large for a stock hemi, you want to get the 1 3/4" for the best performance unless you're planning a big cam, going F/I, or nitrous.

Hemi450hp · Jul 1, 2015

You can get away with the 1 7/8" primaries on a N/A 5.7, but only if you have no less than 4.10 gears and a 3000+ stall tq converter. Trying to run the larger primary header without gears and a converter will result in tq loss.

I run 1 7/8" ARH longtubes on my regular cab, and I'm cutting consistent 1.6 60' times N/A. This is only possible because of the 4.10 gears and 3400 stall converter. My daily driver has 1 3/4" longtubes because it is much more practical for everyday use.

jwheeler · Jul 1, 2015

Hemi450hp said:
You can get away with the 1 7/8" primaries on a N/A 5.7, but only if you have no less than 4.10 gears and a 300+ stall tq converter. Trying to run the larger primary header without gears and a converter will result in tq loss.

I run 1 7/8" ARH longtubes on my regular cab, and I'm cutting consistent 1.6 60' times N/A. This is only possible because of the 4.10 gears and 3400 stall converter. My daily driver has 1 3/4" longtubes because it is much more practical for everyday use.

I have plans for a cam in the future so didn't think the larger size would make that much of a difference so I went with the jba. I really don't want to take these thing off. But the low end loss was pretty noticeable. Better gearing would solve this?

Sent from my iPhone using Tapatalk

Hemi450hp · Jul 1, 2015

Gearing would be a huge help, but you really want to go with both gears and converter to truly make up the difference down low.

tstar · Jul 1, 2015

Thank you everyone, really good info here!!!...

Tim

1morepart · Jul 1, 2015

I went with 1 3/4 Lt's to 2.5" y pipe , muffler delete, to a y splitter and retained the stock 2 1/4 pipe , resonators and tips. No power loss. Definite power gain! She will cook the tires from a dig if you aren't extremely careful. http://youtu.be/L8ylYUpNgkU

DERJ · Jul 1, 2015

The ARH LTs are pricey, but the install is pretty straight forward, the build quality is very consistent, and the power gains are proven. And when factor in the 3" Y-pipe is included, the price isn't that bad for what you get.

As Matt mentioned, you could make the 1 7/8" setup work on a NA truck for the track. But if you're using it in a NA daily driver (like me), the 1 3/4" are absolutely a blast in the lower RPM range most seen on the street.

1 7/8" LTs with a 2.5" Y Pipe, Negates Low End TQ loss??

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