-=Jeff=-

I saw in lGaff thread someone saying the Borla exhaust is holding them back..

http://forums.corvetteforum.com/show....php?t=1814504

Might I ask Why this is? What is wrong with that exhaust?

I had a the Same Challenge system on my 89 and ran a 12.55 @ 111mph, then when I went to the 3" system B&B I was only trapping 110... (yes the PROM was retuned) with my Custom 3" exhaust, I was runnign the same 12.5x @ 111mph

Now I know the L98 (my 89 has bunch of work with a Miniram) is a different animal then the LT5, but where is the problem with the Borla on the LT5?

Just curious

locobob

From what I hear the resonator is quite restrictive.

-=Jeff=-

Thats it? if that is the case I have some thoughts on fixing it

Cdn Z06 Mike

I've got either the reciprocating saw or chop saw......your choice

95ZR1

Greybeard ZR1

IMO,comparisons with an L98 aren't really applicable. I've had both the Borla Challenge, and the B&B system on my car. IMO, the B&B flows a whole lot better. Of course the price you pay in resonance is considerable.
My trap speeds went way up when I put the B&B system on. On an otherwise stock LT5, with headers, (no cats), and the Borla, the best it would do was 110mph. With the full B&B system it went into the 114-115 range, and with a 3" X pipe instead of a resonator, 3" B&B exhaust pipes, and the mufflers removed it trapped 117mph. The sound was hellacious (it scared all the little imports at test and tune )

The Borlas really do sound sweet on an LT5 though, unlike the B&B's which have mind numbing resonance. But remember what system John Lingenfelter used on many early 415's?, Borla Challenge..go figure.

jonszr1

Is there a difference between the borla challenge and the standard borla . when i go on there web sight they say that they dont have an exhaust for our cars? just curoious thanx

Greybeard ZR1

The regular Borla for our car used to be 2 1/2", then they came out with the Borla "Challenge" system that was supposed to be 2 3/4". But mine (the Challenge) actually measured 2 1/4" at the resonator necks....not good.

They may have discontinued one, or both of them. I bought mine way back in 94' when there really weren't a lot of exhaust systems available for the ZR1.

jonszr1

thanx for the info .it seems they did just like gm and neck down t.o 2/1/4. i wonder if there would be any interest in a 3 in exhaust that would be almost as quiet as the borla . my prelominary dyno runs show a 24 hp increase over a standard flowmaster exhaust . completed strip testing show the flowmaster 12.27@117.45 my modded exhaust 11.82 @119.88 mph best.. if there is some interset i will go about making a parts list and draw it out for those that wish to try it . please if you are interested pm me your mailing address and i will try to get it done in 2 weeks and then send it out. there would be no cost to anyone just my way of sharing with fellow zr1ers. ps these tests are with out cats

xlr8nflorida

Personally, I think the whole thing is overrated.

I am basically putting out 400RWHP.

Yeah B&B prolly gets you another 15hp.

You can then pay your dentist or DDSLT5 to give you some porcelin teeth after the reasonance loosens open all your teeth and you need to buy a hearing aid.

LowFlight

How much horsepower if any does the Borla provide vs Stock?

Jeffvette

When the only systems available were Borla and Flowmaster.

tuband

Been reading this thread with a good bit of interest and finally decided to thrown in my .02

I have a 90 ZR-1 (plenum & IJH ported by Corey, SW Headers, and tuning by Corey).

I also have the following exhaust systems:

1) stock OEM system ... previous owner provided it to me; I've never had it installed; will probably sell it to get some more garage space.
2) Borla 2.5" system ... was on the Z when I bought it. The Z dynoed 352 totally stock except for the Borla and K&N. The sound was very nice with minimal resonance. No longer installed since I've added headers ... probably need to sell it for more garage space (i.e. my wife has given me the ultimatum ... get rid of my "junk")
3) Borla 2.75" system ... now on the Z. Corey "adapted" it to fit the SW headers as well as added 3" high flow cats. With the mods, etc. we dynoed OK (not 400 as I had hoped, but crap, it was over 110 degrees in Texas when I visited Corey). The sound is very good & smooth, not too loud and has minimal resonance. Believe it or not, I will probably sell this set, too, since I'm temporarily "addicted" to experimenting with exhausts on the Z.
4) stock LT-4 system ... thinking about building a "custom" set using the LT-4 components. More about this later.

Necking down:
The OEM 90 exhaust necks down to just over 2" at both ends of the resonator and also at the inlet of the mufflers. Actually, when you consider how much the OEM manifold "pinches" down, the exhaust may not be the only culprit for robbing power.
The Borla 2.5" doesn't have much neck down at any of the inlet/outlet connectors, but does neck down slightly inside the resonator. The resonator is a little strange, in that it is not exactly straight thru, but has three tubes running parallel with each other (kinda hard to describe) which I guess was Borla's method of controlling resonance/sound.
The Borla 2.75" also doesn't have much neck down except inside the resonator.
The LT-4 is 2.75" and the neck down is never less than 2.6" ... I'm guessing it is the most efficient C4 exhaust to come from the factory, plus it has the H pipe behind the resonator. The resonator pipes are also straight thru. I would further venture to guess that the stock LT-4 , even with stock mufflers, may not be too far behind the other available exhausts, until you get into the straight thru 3" systems. It is my thinking that with my mods, I don't need more than 2.75". Indeed, a straight thru 2.5" should do the trick.

Just my .02 based on my experiments and observations.

GW Jones

Greybeard ZR1

Actually, there was another high flow system available back then, the Desert Development, (3" - not stainless, I think), it was legendary for being horrendously loud.

FYI, there is a custom system designed by Hib H. using some GM, and Flowmaster parts, over on the ZR1Net website. It supposedly has some pretty good dyno numbers for a non-3" system.

If anyone has a Corsa system for sale, cheap, I might be interested.

Dominic Sorresso

I bought my B&B from someone who has a 91 with Jeals I believe. He thought the B&B with headers was too uch resonance. He went with an LT-4 system including resonator. However, he cut off the stock mufflers and installed 3" inlet Magnaflows. He loves the exhaust. Has much less resonance than B&B and according to him and Marc Haibeck, he's picked up 7hp over the B&B + Headers system.
So far, I think the B&Bs are great. No issue witth the resonance, BUT haven't put headers on yet. Should be remedied fairly soon. The system I took off the car has the LT-4 resonator (straight thru) and the 2.75" pipes to the back. So I might do the same mod IF I don't like the B&Bs w headers. We'll see, I'll be putting cats on with the headers.
Another alternative is the LT-4 with Xpipe instead.
Decisions, Decisions.