Guest Anonymous Posted June 7, 2001 Share Posted June 7, 2001 Thanks for the nice welcome! This site is cool with a lot of good information. I enjoyed looking at the web sites you guys have put together. It really shows you guys have a passion for your work which is evedent by the incredible Zs that you put together! Very talented! I almost did a custom Z, but the Roadster kind of "fell in my lap". If a Z would have come up first I would be doing a SBC Z. I have a friend in Idaho (Idaho Z) that is getting 300+ HP out of the 4.3 GM V6. He is doing a 4.3 Z with 6 speed now. I will keep you posted of the work progess and will have many more questions I'm sure Trimmed the fire wall a bit more last night and the motor/trans is just right! Turbo plumb next. OK - Scottie and all - 1st question. How big a down pipe should I use? I see most use 2.5, but some like 3 inch. Thanks guys Phil Quote Link to comment Share on other sites More sharing options...
Drax240z Posted June 7, 2001 Share Posted June 7, 2001 Personally I'd use the biggest one you could fit, and still keep the transitions smooth. I believe the reasn scottie made the 2.5" one for the Z that size was because he was able to use 45 degree bends, as opposed to 2 90 degree bends. I think a 3" pipe with 2 90's would be equivalent to a 2.5" with 2 45's for flow. If you can fit a 3" pipe in there with no sharp bends, go for it. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted June 7, 2001 Share Posted June 7, 2001 Thanks - and a related question. If I go 3 inch DP, do I have to continue it all the way out? Or could I go down to 2.5 under the Roadster after the exhaust straightens out. 3 inch (stove pipe!) all the way would be tough, but could be done. Phil Quote Link to comment Share on other sites More sharing options...
Drax240z Posted June 7, 2001 Share Posted June 7, 2001 Would it be easier to run dual 2.25"'s? Could be neat with one pipe out each side. Just make a Y after the downpipe. Not sure if it'd be easier than 1 3" in a roadster or not. Quote Link to comment Share on other sites More sharing options...
DavyZ Posted June 7, 2001 Share Posted June 7, 2001 Phil, how will you put the exhaust thru that tiny hole in the rear (think it's thru a crossmember if I remember?) of the car. My bro had a nice exhaust that pitifully pinched down to nothing through that hole. Are you going under or what? David Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted June 7, 2001 Share Posted June 7, 2001 Yep I thought about going dual exhaust. THe only problem is the gas tank is set to one side to allow room for the exhaust on the other side. People have done this, but it is very tight and can only use about 2 inch pipe - i think... Will have to check on this. Or use a fuel cell. The frame does have small holes through the x-member for the exhaust on the drivers side. Only 1 7/8 will fit - or 2 inch smashed. I plan on cutting these areas out and welding in 3 inch heavy pipe so 2.5 inch exhaust will clear. I could do both sides like this for duals. How about using 3 inch through the frame (weld in 4 inch pipe) and into a muffler with two exits, then dual out the back. I don't want the car to be too noisy. The turbo will help with that. Is there is good source for mandral bent tubing parts? The muffler shops in this area do not carry 3 inch stuff for some reason. Thanks for keeping the creative juices going! Phil Quote Link to comment Share on other sites More sharing options...
Drax240z Posted June 7, 2001 Share Posted June 7, 2001 Summit racing has mandrel bent stuff for sale. Not much of an option if you are up here in canada, but for you guys down there it sounds like its a pretty good deal. Also I'd be very careful with cutting through frames/etc. A little can be a lot, in some situations. Just be 100% sure that after enlarging holes things will be strong enough. I'm sure some of the 40,000 resident engineers we have here could offer some advice if you aren't sure. BTW, love those door handles you have there. Awesome stuff. Quote Link to comment Share on other sites More sharing options...
DavyZ Posted June 7, 2001 Share Posted June 7, 2001 Mandrel bent pipe can be purchased mailorder--check the search function in the forum, this has come up before. You should be able to find links, etc. I currently have a 3" mandrel bent system for the Z that will be installed. I purchsed it from the previous owner who said he was going to a single 3.5" for better performance. To his dismay, he found no appreciable difference in power! He is running over 400 hp as I remember. The single 3" flows extremely well and you will have a much easier time in routing it then duals IMO. The system utilizes a stainless steel Borla (straight thru design) immediately after a good "Y" pipe from the DPs. The system goes back to a Dynomax SuperTurbo (big puppy) in the rear and a sweet chrome tip. Size is a major issue with the SPL-311 and I'm not sure just how much room you have. The turbo muffler my brother used is anemic in comparison to the system my Z will use. If you can get at least a 2.5" single pipe you'll probably be ok. 3" is better, but it depends on hp. The turbo will certainly help to quiet the resulting exhaust note on whatever you do. Good luck. David Quote Link to comment Share on other sites More sharing options...
Scottie-GNZ Posted June 8, 2001 Share Posted June 8, 2001 The best turbo exhaust is no exhaust. Having said that, at the HP levels most of us are running, 2.5" is not going to hurt you. Remember the 1000hp Stage II Buick I posted a while ago is running a 3" DP, so what is a 3" DP doing for a 350hp engine over a 2.5"? As DRAX said, if you have have the room or have to make bends, go 3". Quote Link to comment Share on other sites More sharing options...
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