I initially wanted to work around using the stock exhaust manifolds, but have decided that at some pont I would be just choking the motor. Im getting ready to do a tear down (still waiting on some parts) so while the stock e.manifold will be off and Ill have some room to work this will be the time. Im looking at doing L.T.s and possibly true duals back. My questions to those forum members who have this type of set-up are:
1) W/ true duals and an "X" pipe what is the interior resonance like?
and how is it when bullet cats are used?
2) From what I have seen from other forum members pics it appears
to be fabricated, are there any complete assy. available (havent
seen any) I have looked at the usual exotic, summit) ?
3) As to performance, using a set of L.Ts to a 31/2" main cat, to a
corsa system "appears" to be an easier solution, however what
(approx) h.p. difference as opposed to a true dual sys. would I be
looking at?
4) In mfgs. of LT.s, whose product fits well, in the past have used
hookers on other cars who else would you suggest? And what
available pipes w/a flange are avilablto a go from the collector back
or does this need to be fab.?

The car is a 90 L98, 3:07, 26" tall tire, and the mods being done are heads (straight plug dart pro), cam, intake (still shoppin for a better price) stock stroke, so I believe that 21/2" pipes w/ 15/8" header will be fine, corect me if Im wrong
I would appreciatte all sugestions, and especially to those forum members who have been down this road already. Thanks in advance M7

 

Its expensive, but I highly recommend my TPiS LT's. I bought the ceramic-coated ones and they look and sound great. Also, maintainence is EASY when it comes to plugs. Get some Stage 8 locking fasteners for them, though, and you might have to do some work to the supplied Y-pipe (I did)

 

Your combination (assume 350cid) should build 350-360chp. Your motor needs about 2.2cfm/chp before the exhaust system starts to choke power; your motor will need around 800cfm.

Can a single hi-flow cat handle that flow?? I suspect the answer is no and that is why the General went to dual cats with the 300chp LT1.

I don't know of any out-of-the-box duals with dual cats for L98. Check out your local drag strips for a good local custom exhaust shop.

With your 3.07 gears I would suggest going with 1 3/4" LTs into 3" collectors and 3" cats.

 

3"? Come on now... not for a mild small block. Besides, that will cause nothing but resonance.

mseven and I have been discussing this in PM for a week now, and I suggested he create a thread to discuss the specifice. My empirical data is limited on LTs.

My suggestion is the LTs, to 2.5" pipe, to 2.5" high flow cats to a Borla NASCAR style X-Pipe and a cat back of some sort, 2.5".

The questions here are which LTs and which catback?

I don't see the need for 3" anything on a small block under 450hp... 3"? That's bigblock size...

 

Im guessing no one has done this set-up or used LT1-4 dual aftermarket parts on an L98?

 

Yes there are people here with true dual exhaust, the resonance is going to be rough with any exhaust other than Corsa, but its a personal preference thing, some people like it that way, some think its nothing.
Performance difference between duals and the stock configuration, not really, not anything you would notice. As long as both are free flowing. You could just get the headers, Y-pipe, put a straight pipe in for the cat, and slap on a catback and you wouldnt feel any performance difference.

Either get Hooker 2149/2151 or TPiS headers, and you dont need 3" all the way back, you want the pipe diameter to slightly decrease as you go backwards to keep gas velocity up.

 

Thanks to everyone who responded, I appreciate it!
I was hoping to get a few more members who have done this to chime in with their experience/results

 

Resonance is very subjective.. on one car the resonance maybe music to one person and painful to the ears of another.. on my 89 I have done the following:

I have had a few different exhaust systems over the last year or two. 2 years ago I have the Borla 2-3/4" Challenge system on and I should have left it as it was perfect to me, but I found a killer deal on a B&B set-up and bought and sold the Borla. The Borla was headers into a ZR1 catback no Cats.

When I switched to B&B I put a LT1 3" Catback in place of the Borla.. the resonance was really bad, I could not stand it. So I swapped to a X-pipe with a Set of 3" dual cats. the Cats I use are Dynatech 3" ($150 ea).

the Resonance was still bad. This past weekend I swapped to Dynomax Ultra flow Welded series 3" mufflers with LT1 tips, resonance is lowered, but I have not driven the car enough yet to know if I like it.

I am thinking that if I swap the Resonator in place of the x-pipe then it may tone it down. Since I have cats back on the car now, I will leave them and work from there. the Cats are side by side right at the tunnel entry under the car.

I think if I would have installed the resonator withthe cats last year the B&Bs would be fine. they were not too bad on my friends Stock LT1 and also not too bad on another Modded GS. but the Stock LT1 had cats and used the resonator..

if I can fit the X-pipe between the cats and Resonator that would be the best in my mind but I don't think I have enough room. We will see..

 

Jeff, I understand what you mean about individual taste regarding volume, but from your comments it seems your not liking the interior volume (dont blame you), However its obvious your makin some power(read your mods/times) 12:5s un corked? NICE!!!!

Vader and Bogus had mentioned regarding pipe size IM thinkin the 21/2" catback is probably a good move (quieter as well) this is also why Im interested in the corsa. I get plenty of loud (play and teach music), still want to hear radio and drive on the x-wayw/out additional annoying ressonance.

Another question I have is, 2149 hooker full length (2151 med. len.) is that the reference to collector length if so, mine w/A-4 could probably use that the collector length.

Thanks, M7

 

the difference with the 2151 and 2149s is the addition of the AIR tubes on one of them..

the 12.55 time was with the Borla exhaust and headers (no Cats).

I will be trying the Resonator with Cats and see how it goes..

I should have kept my Borla system.. LOL

 

AIR??? Is this smog reference?

Borla sounds like it was workin , how loud (interior ) was that system?

Read your thread, hope that works out, sounds like you have definitly spent some serious $$$ not to mention time, dont blame you for not wanting to spend additional coin

 

Yes AIR is the SMOG stuff..

The interior had some resonance, but to me it was fine, I could hear my stereo decently over the exhaust noise..

Keep in mind on the money I spent on exhaust I always got a used exhaust system, I never paid over $400 for a LT style catback..

and got most my money back from it when I sold it. Only things I boght new other then the headers are the Cats and X-pipe.

I think I will find the set-up I want.. just going to be a little more trial and error.. what I have now sounds good, not too bad on the resonance but I think I can tone it down a bit more.. I will swap the resonator in the next month or so in hopes to get it where I want it.

 

Good to hear it didnt kill your b account!!!

In all my haste (have to get back to work) I forgot to ask about the cat itself. At this point, can I then can use a cat(s) that will bolt up to the Y' and that accepts lt1 size (flange) corsas 23/4" (aside from the new L98 21/2") ?

And if so does the rest of the setup (mufflers) hang w/out mods.? It sounds as though this is similar to what you have done (obviously more). I ask this because even though c-4 is a c-4, Im bettin that are some differences in tube lengths, mounts etc.? Sorry for all the questions, Im just tryin to check out all my options. THANKS for the info m7

 

Some pictures of my set-up are here.. I am not using the OE style cat anymore..

the grey crap on the front of the Cats is muffler cement, I have a leak there and it is a temp fix until I can get better clamps on them

http://jeff.vettextc.net/exhaust