Monday, November 07, 2005 - 07:21 pm, by: Mike Beck(Gold_40gt)
Ive got a stock uzz30 v8 soarer. I plan to do these few mods over the year or so.
Just wondering what sort of % gains in rwkw or rwhp i would expect to get by doing them. Ill of corse be taking this to the dyno to find acurate results of how it is now, stock and each time i perform another mod.
1) Exhaust 2.25" to stock cats. All 5 mufflers removed and an X shaped cross over pipe. Lukey 2.25" double offset ultra flos.
2) 3rd BFI version with cold air ducting.
3) Stock ecu reset before unichip etc. Will i get any power out of making it learn to drive a bit harder?
later on (at least 6 months)
3) Headers and 2.25" dual cats to complete exhaust.
4) Uni-chip and tune.
ill be very happy with thos 4-5 mods done. Any thing else i should do?
Monday, November 07, 2005 - 07:32 pm, by: Mike Beck(Gold_40gt)
headers before other exhaust work? hmmm seams more cost effective going the mufflers to the headers.... headers are the best exhaust mod so you do have a point... id rather get rid of the quite 5 mufflers first however.
Monday, November 07, 2005 - 07:39 pm, by: Mike Beck(Gold_40gt)
mmm thats true.
Well for now id say id be quite pleased with the exhaust done from the stock cats. Headers and high flow cats can wait a good few months until ive got the odd 600+ for them and feel the need for more power and a better exhaust note...
Monday, November 07, 2005 - 08:01 pm, by: Mike Beck(Gold_40gt)
I think ill try how ive planned the exhaust in a month or so and if its not want and drones etc ill get the headers as fast as i can and just pay the extra cost fit them in with the new exhaust... Money is not that much of a problem
Monday, November 07, 2005 - 09:00 pm, by: Mike Beck(Gold_40gt)
id be more than happy with 170 rwkw!
Yeah, it's probably got around 130rwkw stock, which i find is good power.. Ill get it dynoed in December, its been well maintained and has 122,000kms so it should make good power... have to wait and see.
Monday, November 07, 2005 - 09:47 pm, by: Avin Luther(Lex_luther)
i would leave the cats out if local regulations permit, other wise put in larger Hiflow cats. Ans as suggested above, do the headers at the same time as the rest of the system! It is a big job and makes the rest seam simple. You will also save Lots of money, and it will allow the exhaust shop to build a proper system in one go. I got 148rwkw with headers, hi flow cats, twin 2.25 and BFI. ~20kw gain for about $1800
Before it gets any further embedded in folklore, I would like to kill the newly created myth that has sprung up in the last week or two, that modifying the exhaust on a V8 without fitting headers is likely to cause droning.
I have been in a few cat-back modified exhaust V8's and none of them droned. Conversely I have been in a V8 with headers that droned quite a lot.
Droning is a function of the entire exhaust, choice of mufflers, amount of vibration transmitted to the cabin via mounts not hanging freely etc. Not just whether it has headers or not.
A 30rwkw gain is available without fitting headers (and no drone, as Peter says). In fact, my exhaust retains the original resonator as well as the cats and exhaust manifold. Cost for that (including Unichip) was $1950 or $65/kw compared with $90/kw in Avin's example.
So, replacing headers and cats is not as cost effective for power gain as the other three changes (BFI, Unichip, muffler/strangler replacement) but if you want the extra power headers/cats provide, then it is cheaper to do them before the rest of the exhaust.
Tuesday, November 08, 2005 - 08:56 am, by: Miles Baker(Milesb)
removing cats is worth a couple of kw tops. do the environment a favour - don't be an ass for 2kw. unburnt hydrocarbons are nasty. plus you won't have a rear bumper covered in filthy black crap all the time.
Tuesday, November 08, 2005 - 01:45 pm, by: Avin Luther(Lex_luther)
David Vaughan wrote on Tuesday, November 08, 2005 - 07:24 am:
Cost for that (including Unichip) was $1950 or $65/kw compared with $90/kw in Avin's example.
David, i hadnt had mine Dyno'd before the exhaust so this is only a rough estimate based on stock figures of around 130. I dont think you can break it down into KW for dollar! Also when looking at an upgrade path i did headers in the hope of fitting a chip one day, and felt this would optimise any gains possible. It also sounds AWESOME.
ALso most of the price in an exhaust willbe on the choice of mufflers and cats, and this can be more up to style than performance.
Avin, I had no intention to cause any offence so please do not worry about that. Your base power estimate accords with mine. Your initial power would need to have been down around 123rwkw to get the same gain per dollar. I think looking at what you get for dollar spent is perfectly legitimate. in your case (and others) fitting the headers makes sense because of the total gains you will eventually seek whereas I am deliberately capping possible gain. So, my choice (no headers) limits total gain but at a higher payoff than any alternative limited path. Unlimited paths are a different matter. Hope that is clear.
Back on ALSC earlier this year I did a dollars per kilowatt comparison of the various changes. The main points were that doing anything before a BFI is profligate, while a Unichip has a good payoff ($90-$100/kw plus low end torque benefits) if you can afford the capital for the chip and the running cost of locking into Premium fuel. It also showed that if you are planning either headers/cats or cat-back exhaust (one but not both) then the rear exhaust has the better payoff but if you will ever do both then the headers come first, this being the point I am making in the previous post.
A supercharger costs more per kilowatt gained than any of the other changes and hence came last in my list even though it provides the biggest single gain. As a side point it needs some of the other breathing changes to be most effective anyway.