Firebirda7x

Does it have the hookups to your oil lines and the intercooler too?

lillee64

you dont need a intercooler for a rear turbo

Firebirda7x

Well you don't need one anyway, but it' a bit self defeating to not have one. Although I don't understand why you say rear systems don't have one...

fast82z

iTrader: (1)

An intercooler might not be "as necessary" with a rear turbo, but I can assure you that my pre-intercooler temps of 200+ degrees would not come down to anywhere near atmospheric air temps without an intercooler no matter where I placed the turbo. Just fyi, my w/a intercooler has taken 200+ degree air down into the 60 degree area.

lillee64

every rear turbo system ive seen didnt have an intercooler and it said that one is not needed because the length of the tubing back to the engine. i guess one would help but its not really needed

P-ROC

iTrader: (2)

I'm no turbo expert but I think it is pretty safe to say that you would successfully boost the turbo. What about the engine?

Firebirda7x

Lillee, the air will not cool down as it travels back to the front of your car. The turbo heats up the air due to heat of compression, it will just expand even more. That is why you want an intercooler, especially with the turbo so far from the engine.

blackbmagic

You are right about the air expanding more that is why you loose ~2 psi when using either a large inter cooler or rear mount turbo. It has more room to expand.

But you are very wrong about air not cooling down. Air cools down when using a rear turbo system because of the length it travels as well as the surface area of cooler materials such as the charge piping traveling from rear to motor. You also loose PSI.

This is why many rear turbos do not use intercoolers. They dont "need" them. If they used them which they can they would loose even more PSI to the engine.

Orr89RocZ

iTrader: (20)

Pressure lossed doesnt really matter if you have the mass flow required to make the power you want. PSI is just a measurement of restriction. IF you have more restriction you will show more boost but doesnt mean its flowing more. What matters is what the motor sees. You will be referencing the wastegate off the intake manifold pressure on most setups. IF you want 10 psi, the wastegate will stay shut until the referenced port sees 10psi from the intake manifold. So if you have alot of restriction in the cold side, the backpressure in the exhaust manifold could be much higher than it needs to be, just to overcome the losses.

A good intercooler will have minimal pressure drop across its cooling medium. If you do have restrictions, the turbo may have to output a higher pressure just to overcome those restrictions to get the flow up to where you need it to make the power you are trying to make. That just makes an inefficient system as you will have to overwork the compressor more and thus may have different efficiencies. A lower efficiency heats the air more.

A remote system not using an intercooler is stupid. Front mount systems dont "need" an intercooler either, but you will be limited on what boost you can run or what gas you can run. Most carb guys dont run an intercooler either because the fuel cools down the charge enough, but the ones that do usually run faster Always use an intercooler unless its a race gas application and where space is limited. Cooling the intake charge down makes power so run one.

Firebirda7x

Boost is created when there is restriction as the above user said...so having a lot of boost doesn't mean the engine is breathing good. You can have restrictive heads and build up good boost but in the end you still want cooler air moving into the engine.

I assumed that there wouldn't be a lot of heat loss due to the long return pipe because the underside of the car is still pretty hot and the gases will be moving so fast they won't get a chance to cool down.

Orr89RocZ

iTrader: (20)

Just look at an exhaust system. Header pipes near the heat source (combustion chamber) are very hot but usually the tail pipe tips arent quite as hot. There is a good bit of cooling there. Given enough time however, they do get pretty toasty. My over the axle pipe was touching the plastic gas tank I have and it started to melt it.

So there can be hot gas traveling thru the "cold" side piping to the intake manifold from the turbo. Heat transfer thru the air passing under the car will help cool it off but I doubt its as effective as an intercooler would be. You can attempt calculate it thru simple heat transfer equations. 15ft of 2.5" piping would have surface area of 1423 sq. inches. A typical front mount intercooler bar/plate design that fits in the front grill area of a thirdgen camaro (like mine) is in 2500 sq. inch range. Much more cooling surface to work with.

All depends on how efficient the turbo is and how hard you run the car. If you have a good sized compressor wheel, it will be fairly efficient and not heat up the air as much, so the 15 ft of pipe to the front of the car will do a good job on cooling off the air charge. Plus, boost is what is heating the charge up so much so if you are not in boost for long periods of time, there will be much less heat generated.

I'd like to see what intake manifold air temps are at the TB and at the compressor outlet to see how hot things are getting. The turbo itself will be very hot so the air already is getting heated coming out of the compressor, let alone the heat made from compression of the air. Air gets pretty hot fairly quickly in compression.

lillee64

id be doing this on a carbed engine. not really going for major boost, thats one reason why i want the rear turbo, i dont have cats and wont be using an intercooler

Orr89RocZ

iTrader: (20)

Carbed engine it shouldnt matter too much. The fuel is gonna cool the charge even more so you should be ok.

84blacktransam

Sorry guys, I could only get maybe 2/3ds of the way through this thread. I used to be a semi active member but then I went off to college, and the Trans am stayed at home and I got a 300zx. I joined a forum about them and kinda left thirdgen behind, for the time being. Anyway I'm going back to NY and thought oh man I know, I'll grab some turbos and twin it. Lets see if anyone has done something like that. And I find this.

So I can only wonder, why would you ever want to do a rear turbo? Some of you seem to think its cheaper. How can that possibly be? You still need the turbo, but now you just need a ton more piping. When you install an intercooler you gain lag. If you use larger diameter piping you get more lag. Why? because the compressed air has to travel through more volume before it reaches the engine. So all that extra piping you will have to run will just add to turbo lag. Sure, you can use a smaller turbo and it will spool quicker. Thats stupid. Because you can install a larger turbo closer to the engine and get more power with the same spool time. If you're "just looking for an extra 150hp" just get nitrous. Turboing obviously isn't for you. Why do a rear set up when an engine bay set up will get you more power, less spool time, and probably cost less?

I can't imagine why you wouldn't do a turbo in the engine bay. Only benefit I see of not being in the engine bay is that its hot in there, and that affects the air temperature, however there are ways to offset this. With the more than ample room in our engine bays, this is BY FAR the way to go.

Get a junkyard turbo, junkyard intercooler or one off ebay, and an ebay piping kit. You'll have to make an exhaust manifold. Maybe they sell them. I am going to do a twin so cross over won't be an issue, otherwise you will have to have the turbo run from both sides of the engine. After that its all custom but I mean it really is a pretty simple concept, I don't see where people are tripping up here. Just start READING and RESEARCHING and that will help you.

Another concern is what fuel system you have. I have a carb, and there are issues you run into with that. Fuel injection is easier, but you will have to retune your computer. I know nothing about the fuel injected 3d gens so, thats up to you.

You want to do something different? Thats great. Seriously, I love innovation when it comes to cars. But it is obvious that you can make more power with your turbo in the engine bay. Theres plenty of room, just do some reading about turbos and start looking at the local junkyards. And good luck

Primetime91

iTrader: (15)

I'll disagree with you on one thing... Rear turbo's are easier to set up, since you can largely use the stock exhaust system. Because of that, and the fact they often omit intercoolers, they are often cheaper.

I'm not a huge advocate of them, but they do have their place; when maximum possible horsepower & efficiency isn't the goal, but extra power is needed at low cost.

Orr89RocZ

iTrader: (20)

I just dont like having to route a cold side pipe back to the engine bay. these cars dont have alot of room under the car as it is. You dont see many dual exhaust setups with good clearance on these cars unless you ride on stock springs that sit high up.
Best way to do it would be to run the pipes in the stock location, but you dont want to run your cold side piping along the hot exhaust pipes, else you need an intercooler, which I'd run regardless.

Other option is to bring it up through the trunk and down under the passenger seat thru the firewall to the side of the intake manifold...using a sideways elbow ontop a EFI single plane manifold. Thats what I'd do

bradyb

I ran a rear turbo kit on an '02 SS, she ended up with 585 horsepower running 8 PSI with methanol injection.

I ran the car as a two stage, flipping a switch between 5 PSI and then ran the methanol at 8PSI.

If you want to see how to put together your own kit then contact STS turbo. The turbo sate longitudinally where the muffler was. The charge pipe ran over the axle towards the driver's side, the pipe then bolted in on the driver's side just like a subframe connector. It then ran under the K member and came up in front of the engine going directly into the LS1. With your car you would have the charge pipe come up on the side, just like a LT1 cold air intake.

The car did bottom out on the charge pipe that was bolted in like a subframe connector but it was fine since that pipe was a heavier gauge.

I found that 5.5 PSI was about the most you could run with out an intercooler of some kind. The car made full boost by 3,000 RPMS. It sounded absolutely wicked, I just put a dump pipe off the turbo.

Here's the STS kit:
http://www.ststurbo.com/ls1_installation_pics

84blacktransam

Yeah turbo cars sound really cool, but I'm not too sure if the sound would be that much different having it in the engine bay, or rear mount. I wouldn't mount one under the car because I don't think it would be protected. Maybe you could do this successfully on a track only car, but on a Daily Driver type car I think its just going to cause problems.

I guess it is easier to set up a rear turbo in terms of the exhaust, but you still have to run the air back up into the engine bay. And if your only going to run 8 psi of boost, you can use a small turbo.

If you want to run a large amount of boost you should get an intercooler. Or run some kind of cooling injection like the guy above did.

I was just thinking about piping and don't know where you would run the return pipe. I mean for heat soak reasons you shouldn't have it next to the exhaust. Otherwise you would probably need an intercooler. I know! how about you run the pipe through the passenger compartment, and you can have the blow off valve blow right in your face to cool you off on a warm summers day.

If you have low compression you could probably get away with 5-8, like the guy above said, without an intercooler.

When I'm back in NY I'll see if I have enough money to put on the Trans am and if I do twin turbo it I'll do a write up. Good luck designing your system, I still think rear isn't the way to go.

bradyb

Before a drunk driver killed my SS, I had the STS kit on the car for three years. Driving it everyday in Utah, snow and shine. I ran a big K&N filter that I cleaned two to three times each year. During the winter, I ran a water resistance filter sock.

I went through three rear ends, a clutch, and two sets of tires. The car was just about worn out after 40K miles, adding 280 horsepower to a car will do that.

Orr89RocZ

iTrader: (20)

Ultimate idea is to have air intake for the turbo up thru the trunk floor into the car cabin. Hopefully you have AC and can make it a REALLY cold air intake

Tony89GTA

iTrader: (7)

Nice to see someone on here that actually has used the system and had good results, with 585 HP must have made it a really fun daily driver Plus it makes all the naysayers whine more and make stupid jokes.

Quick question though, about the oil return pump was there any problems with it in the 3 years?

lillee64

having the turbo in the rear makes a big difference in sound because the turbo is soo close to the exhaust exit. where would be a good place for the wastegate and bov?

Firebirda7x

BOV needs to be before the air inlet and in front of the turbo outlet. I'm not sure where backpressure would first build up on a rear turbo system...maybe right at the turbo or maybe still under the hood. Normally since the turbo is right next to the engine it's pretty much right there in between...dunno how that long pipe comes into play. For a wastegate I'd think it still goes where it normally would go..behind the turbo inlet.

Orr89RocZ

iTrader: (20)

Take a look at the STS turbo systems. I'd put the BOV right before the TB and the wastegate goes right before the turbo flange on the exhaust. The wastegate vent pipe can discharge to atmosphere...dont have to run it back into the downpipe like most people do with front mounted turbo setups

junkcltr

iTrader: (1)

Ha ha funny. Ask anyone who says that says a rear mounted turbo IC is not needed what the cooling surface area of the pipe back to the intake is. Then compare that to a proper sized turbo. Just a long pipe is a fraction of the surface area of a real IC. You will find that the "unnecessary rear mount turbo IC" is needed for decent boost.

Too many suckers believing in rear mount turbo literature published by certain companies. None of the companies support their myths with actual math & physics. Real companies like Garrett and others give the equations to do real work calcs.

RMT systems work when done right just like FMT work right when done right. Yeah, for an STS system with mild boost you don't "need" the IC...............regardless of it is in the front or rear. The RMT IC cooling from the long intake pipe is BS.

Firebirda7x

I was thinking the other day, a rear STS system without an IC might be useful for providing mild boost for my long runners to not struggle at high end air flows. Of course, that's a lot of money to shell out just to overcome the downside of long runners, you might as well get the intercooler and do it right.

ZZ3Astro

Rear mounts are much quieter than FMT's if you're running no muffler. A RMT actually sounds pretty decent too, albeit loud, for a no-muffler setup. And there is no denying the turbo spooling sound of a RMT is very pronounced and sweet sounding. On the other hand my FMT with straight three inch pipe running to the back of the car sounds absolutely terrible without the muffler bolted on. It sounds like a straight pipe from iron manifolds sound... loud and ugly but with the turbo sound mixed in. In my old age I like quieter so I'm happy with the FMT/rear muffler configuration.

freaky

so what size ar on the exhaust side of a hx35 for a stroked 305 with elederbrock heads on it .

hotshift13

Looks interesting!! Im in the research stages of doing a turbo setup on my T/A, this looks like it could work quite nicely. Look on you tube, there are a few things on rear mounted turbo setups. I love the way they sound, simplisity, and they dont seem to have hardly any lag. So taking off the muffler welding on a turbo flange route the piping? I can fab so it wouldnt be too hard to do.

I guess the biggest question is how large of a turbo to run, t3 t3/t4, gt45?

The sts kit works, just the price is crazy considering it looks like some parts can be bought on fleabay... $1900.00 for a base kit? WOW!! There is a two guys garage clip of them putting a sts kit on a 4th gen camaro. built 140hp and about the same for tq? Im sold on this idea, and I still have the exhaust out of the T/A.

Cost looks to be less with this setup cause you don't need a fmic, headers, which we all know can be expensive. A little digging around it seems like $1000,00 can put together a real nice set up.... Discuss....

Firebirda7x

$800 on ebay I found a twin turbo setup including headers for a 305....a rear mounted turbo will have more lag, the gases need to go to the back of the car and the return air needs to travel to the front...more lag not less. And you need to fabricate your own piping, and 3rd gen F bodies don't exactly have a lot of room under there as it is...

fast82z

iTrader: (1)

I'm gathering parts for my car to make a rear mount setup over the winter, and I'll start a post when I actually begin making stuff. It's going to be twin 70mm's. I wouldn't count time as a factor of the air traveling since 225hp worth of exhaust through a single 3" pipe still comes to 80feet per second.

hotshift13

Please post a link of the $800.00 ebay kit please..... Im interested!!!

Firebirda7x

Yea but when you have turbo lag with the turbo up front the extra piping isn't gonna help. U gonna have an internal or external wastegate? or just a blow-off valve? Those are also illegal...

Firebirda7x

http://cgi.ebay.com/ebaymotors/Twin-...#ht_2372wt_939

Tony89GTA

iTrader: (7)

That doesn't have any chance of fitting.

fast82z

iTrader: (1)

Since my current Tial 60mm wastegate and Procharger red race BOV seem to be working nicely with my 91mm turbo now, I plan to keep them. Wastegate will attach to both headers and be placed as close to the motor as possible so that after it I can properly use smaller pipes to help spooling. Not exactly sure where I want to put the BOV, although I'm thinking by the throttle body would be the most proper location.

Firebirda7x

I would think you would want the BOV closer to the turbo outlet, correct? I am wondering if the pressure along the piping will affect the BOV opening if it is near the motor as opposed to being nearer the turbo.

Why not?

fast82z

iTrader: (1)

My thoughts with the BOV being close to the TB is that when the TB rapidly closes all the air coming from the turbos has to make it all the way up to the TB and exit the BOV. Should I loose traction and have to let off and get back into it, total air flow will only have to "refill" a few inches of pipe instead of many feet worth of pipe so that the engine will be able to come back into boost more rapidly although this may be a fairly slight difference.

Grifter757

iTrader: (5)

I had an STS setup on my car for about 3 years until now were everything sits where the battery was. For what it was the car made good power. At 9PSI of boost full boost was not hit till 3500ish RPM which is kinda high for the small turbo I had (T-60 then T-67) I have Eiback springs and scrapped on everything and everywhere. Tried fixing it twice by doing diffrent routing and stuff but always ran into one problem or another. Blowing holes in the silicone couplers was also common and sucked trying to run through 10 feet of pipe to figure where the leak was. **** from roads would hit the turbo and hit me and any standing water would worry me from getting sucked up in the turbo. All in all it made good power is just the headaches i got from it made me want to go another route. Oh but it did sound good.