ZR8ED Posted August 23, 2003 Share Posted August 23, 2003 I know that the 3" is preferable for a turbo system over a 2.5", but I'm wondering the effects of one over the other. I have a 2.5' system on my car..but I'm using the 3ft of the stock 300zxt exhaust.. (like a cat back system without the cat) Car is in the shop, and everyone is telling me my exhaust is much too restrictive for my t3/t4 hybrid turbo..and that I have too much lag..I do have more lag than when I had my t3 on it, but i was expecting more lag, so i don't know if it is normal or not... 2500rpm if I floor it, boost will only come up to 3-6psi..and I wont' get full boost till just past 3500rpm..approx...maybe 4 sec..??? I'm not sure if i should go through the hassle of replacing it with a mandrel bend 3" system? would I notice a difference, or are we just talking a few hp? It does feel laggy...if i floor it at 4k, it comes on pretty hard... My hp goals have just been drastically changed (see post in engine problems forum) I'm not sure if it I'll see enough gains to justify it.. anyone dyno'ed before and after? Quote Link to comment Share on other sites More sharing options...
Guest ON3GO Posted August 23, 2003 Share Posted August 23, 2003 well if you have part of the stock piping on there i would get rid of that and all cars if you have one. 3in's will flow abit more, and im sure more then "a few" hp will be free'ed up. Quote Link to comment Share on other sites More sharing options...
BRAD D Posted August 23, 2003 Share Posted August 23, 2003 If you have the spare cash and you are not happy with the lag, I would do it. As for HP# i dont know but turbos love free flowing exhaust What kind of muffler do you run? Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted August 25, 2003 Author Share Posted August 25, 2003 I've done some casual searches here for some info leading to dyno proof of a larger exhaust for a turbo engine. It looks like it is going to cost approx $1100 for a 3" mandrel bent custom made exhaust..this price is very approx because it includes the down pipe, and of course he said the price may vary slightly because of the custom nature of my engine swap. I'd like some opinions if this mod is worth the money? I will probably have it done, I'd just like some opinions if I'm an idiot to spend the money or to not spend the money.. and no I don't have a money tree in my backyard...maybe a money weed...but certainly no tree! Quote Link to comment Share on other sites More sharing options...
Guest ON3GO Posted August 25, 2003 Share Posted August 25, 2003 can i borrow that money weed? i could really use that right about now.... Quote Link to comment Share on other sites More sharing options...
JMortensen Posted August 25, 2003 Share Posted August 25, 2003 That's one expensive exhaust system!!! Check out JC Whitney. You can buy 180 degree bends cheap, I wanna say you can get stainless too. Buy a few bends and go to an exhaust shop and have them weld it all up if you can't weld yourself. Should save better part of $800 including new muffler and shop charges... Jon Quote Link to comment Share on other sites More sharing options...
BRAD D Posted August 25, 2003 Share Posted August 25, 2003 I think he is talking about a full stainless steel system... Quote Link to comment Share on other sites More sharing options...
fl327 Posted August 26, 2003 Share Posted August 26, 2003 for that money, go titanium. Quote Link to comment Share on other sites More sharing options...
Drax240z Posted August 26, 2003 Share Posted August 26, 2003 I'd go 3" if I was in your situation... not for that kind of money though. Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted August 27, 2003 Author Share Posted August 27, 2003 I thought it sounded steep, but this shop supports our Z club, loves working on Z's, and specializes in high performance work on highly modded and exotic cars in Toronto. I've had crush/bend custom exhaust systems built front to back for me for under 300.00. with custom y pipes etc.. This would not be a SS system. He is talking about aluminized mild steel, and includes the downpipe, all the way back to a SS high quality brand name muffler. Maybe I should get some more info from him? Its way beyond my skills to build it, but I suppose the most expensive part is the labour to make and fit it under the car. maybe I should just replace the down pipe and the stock 300zxt part of the system, and leave my 2.5" part of my custom exhaust alone.. it is only 1 year old..and seems fairly free flowing minus the reduction of the diameter to make the bends. Any more thoughts? this will be wrapping up next week, and I want the car done so I can enjoy the end of the summer with it. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 27, 2003 Share Posted August 27, 2003 Whatever you do, DON'T get a crush-bent system. Even if you go with 2-1/2", buy mandrel bends and have the muffler shop weld or clamp them in. Crush bent is very restrictive, and the wrinkles trap moisture and rot out much quicker. Quote Link to comment Share on other sites More sharing options...
Synlubes Posted August 27, 2003 Share Posted August 27, 2003 maybe I should just replace the down pipe and the stock 300zxt part of the system' date=' and leave my 2.5" part of my custom exhaust alone.. it is only 1 year old..and seems fairly free flowing minus the reduction of the diameter to make the bends. Any more thoughts?[/quote'] Sounds like a good idea. You can find out if you see the gains you are looking for with out spending the big bucks. If it works, leave it or replace . . . Quote Link to comment Share on other sites More sharing options...
Guest szlash280z Posted August 29, 2003 Share Posted August 29, 2003 take off the pipes and run it with just the DP, that will tell you if your exhaust is too restrictive. (right?) If it's better without the pipes on there, that would tell me to try a new exhaust, if it doesn't make much difference, then it is fine. I have only run my stock T3 Turbo with the DP alone (I have no exhaust yet), it still doesn't produce any real boost until 3k. The turbo is freshly rebuilt. Can't get much better at flowing than that. Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted September 8, 2003 Share Posted September 8, 2003 This is interesting... Dyno charts from Stock to 3" exhuast Author: mylesm (---.vc.shawcable.net) http://www.zcar.com/forums/read.php?f=1&i=398657&t=397847#reply_398657 This is a baseline dyno run with stock exhaste: This is a dyno run with 3" exhaste: Quote Link to comment Share on other sites More sharing options...
Savage42 Posted October 7, 2003 Share Posted October 7, 2003 Does switching to a 3" exhaust make a difference? Definitely!! Of course, the whole engine is a system, so depending on other things, it can really make a big difference. Here's a dyno chart from the VG30 turbo in my 510. The motor is stock, stock turbo (T3) & injectors. Custom headers, JWT ECU, headers w/ 3" mandrel bent exhaust, Starion intercooler, HKS blow-off valve. all bolt-on stuff! This was on pump gas at 15 psi. http://www.datsuns.com/Tech/engines/vg30et_dyno_savage_510.gif It had considerably less power before switching to 3". Quote Link to comment Share on other sites More sharing options...
Guest Nic-Rebel450CA Posted October 8, 2003 Share Posted October 8, 2003 The diameter you need is all dependent upon the CFM of exhaust flow. Straight pipe flows at about 115CFM PSI (115 Cubic Feet per Minute per Square Inch). This means a 2.5" flows at about 450CFM and a 3" flows at about 550CFM. Of course, this is all irrelevant if you have a muffler that doesnt flow good enough to match. Not sure how to tell how much airflow is going in under a turbo situation, but if you can find this out then you can figure out your demand and those figures should help. Quote Link to comment Share on other sites More sharing options...
fl327 Posted October 8, 2003 Share Posted October 8, 2003 a good downpipe. the gain from the 3" will not be as potent if you dont get a nice downpipe, but it will make more than 2.5" in any case with a turbo. Quote Link to comment Share on other sites More sharing options...
Guest ZmeFly Posted October 15, 2003 Share Posted October 15, 2003 if your using the starion, ive found that at only 10psi on a stock L28ET that the pressure drop across the starion ic is 3.5 psi!!!!! if you really want to see an increase in your 510s power lose your last restriction which is that starion ic and get a supra ic, 944 ic(the one i chose because it was bar and plate design flows at 650 cfm) or an NPR. your putting out great power and i hate to see it lost in that shabby ic. ive had one, they really do suck! great dyno numbers though once again, i wish i were there Quote Link to comment Share on other sites More sharing options...
Guest bloodyknucklz Posted November 11, 2003 Share Posted November 11, 2003 The price quoted by the the shop is insane. As mentioned previously the best way to do it is to buy mandrel bends ...they come in different diameter. Then buy a section of straight pipe. Fabricate the exhaust by cutting the bends and welding together. There are few bends required for your setup. I had mine done for under $450.oo (not stainless though) Quote Link to comment Share on other sites More sharing options...
ZR8ED Posted November 15, 2003 Author Share Posted November 15, 2003 I'm going to take this a bit easier now... I thought it was pretty expensive, but this shop is a respected speed shop..(ala twin supercharger install on a viper gts) Guy just loves Z though... I'm going to get the material myself, and see what can be done about putting it together. I know a great welder/fabricator that can help...For 1100.00 its worth trying on my own... I think I may just replace the part of the exhaust that is factory stock...that ought to free up enough to be able to notice if its worth the effort to redo the entire exhaust... Thanks. Quote Link to comment Share on other sites More sharing options...
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