The Zombie rear mount turbo saga
11-28-2007, 04:29 PM
#1
The Zombie rear mount turbo saga The Zombie rear mount turbo saga. (it wouldn't be a saga if it was a short write up 
)
I've been seeing a lot of posts on STS/rear mount turbo setups lately so I thought I'd summarize (along with some cheesey humor) some of what I have learned to help others.
Chapter 1... A New Hope.
The concept of the rear mounted turbo setup popularized by Squires Turbo Systems exists because of limited space in the engine bay of most modern cars. While it is possible to mount a turbo in the engine bay of many cars, it can prove very challanging and even more of a challenge to retain all the cars accessories. There is also the problem of additional heat added by the turbo charger than can be difficult to overcome on some vehicles that require the repositioning of the factory radiator in order to fit the turbo. That won't work for someone like me since I live in a climate that can reach 115 in the summer.
There is no debating that a turbo mounted close to the engine will spool faster and make more power than a rear mounted setup, which is simple physics. The advantage of the rear mounted turbo is it's simplicity in installation. Its downside is it's complexity in getting it to function correctly. More piping means more of a chance for boost leaks and exhaust leaks before the turbo.
A rear mount turbo is capable of spooling quickly and making a lot of power. How well it does this is determined by the mechanical setup of the system as well as the tune. If the setup is good it can be similar in performance to a traditionally mounted turbo in the engine bay. If it is setup poorly, it's slower than a short bus full of window lickers.
The basics of getting the turbo to spool fast are keeping as much heat in the exhaust stream as possible and minimizing back pressure after the turbo.
Chapter 2... The Empire Strikes Back!
The rear mount turbo, loved by some, despised by others. How can such a simple device as a turbo and it's where it's located stir as much hatred as it does. Perhaps the hatred is due to latent homosexuality since rear mount turbo users "like their turbo in the butt". Who knows.
The first results from a lot of rear mount turbo users were dismal and received lots of hate from the traditionalists. Hearing taunts such as "that thing won't spool until next week" and reports of end users claiming very little performance gain were not uncommon. Some were happy users; others were selling off their kits for other "better" solutions. Things were not well, the Empire was pleased.
Chapter 3... Use the Force!
Eventually end users started to listen to the cries of partially correct dissenters who claimed a turbo runs off of heat (they run off of heat and pressure). They started to insulate their exhaust piping and swap headers for stock manifolds, anything to keep the heat in the exhaust stream. Surface area is the enemy. The more surface area on your exhaust system, the faster it gets rid of the heat. Headers are the worst mod on a rear mounted turbo setup. They have a very large surface area compared with exhaust manifolds. That large surface area is also at the point where the exhaust is it's hottest, the point where you want to keep the most heat possible.
Exhaust heat causes the volume of the gas to be larger. That larger volume of gas in a confined area equals more pressure. More pressure equals faster spool. Pressure is both friend and foe though. As much as pressure can help you, it can hurt you. Too much pressure and things start to choke up.
Hot exhaust gas has much more energy and pressure than cool exhaust gas. Without a waste gate before the turbo to bleed off some of this exhaust, the turbo would spool to its maximum. The waste gate lets us regulate how much of the exhaust is actually making it to the turbo and regulate the amount of boost produced by the compressor side. The goal is to supply the turbo with just enough exhaust energy to spool up as quickly as possible to the set boost level and then bypass the rest of the exhaust gas. The best way to bypass extra exhaust gas is a larger exhaust housing or a larger exhaust wheel or both. The hotter your exhaust gas the less of it you need to spin the turbine wheel of the turbo. This means the hotter exhaust gas is more efficient at doing the work. Since you don't need all of it to do the work, you can bypass the extra. Bypassing this extra gas causes the backpressure to drop which allows the cylinders to fill easier. If you don't bypass this extra exhaust gas your engine tends to choke at higher boost levels and RPMs due to excessive exhaust back pressure. It becomes more difficult for the engine to ingest more air when it can't get all of the spent exhaust out of the combustion chamber because it's fighting the exhaust back pressure. Controlling this backpressure and maintaining decent spool can become a delicate balancing act. Bypass too much and your setup spools slow and might not be able to make as much boost as you desire. Bypass too little and you run into excessive back pressure and possibly over running the flow of you waste gate causing you boost creep, poor power and increases your chance of detonating.
)I've been seeing a lot of posts on STS/rear mount turbo setups lately so I thought I'd summarize (along with some cheesey humor) some of what I have learned to help others.
Chapter 1... A New Hope.
The concept of the rear mounted turbo setup popularized by Squires Turbo Systems exists because of limited space in the engine bay of most modern cars. While it is possible to mount a turbo in the engine bay of many cars, it can prove very challanging and even more of a challenge to retain all the cars accessories. There is also the problem of additional heat added by the turbo charger than can be difficult to overcome on some vehicles that require the repositioning of the factory radiator in order to fit the turbo. That won't work for someone like me since I live in a climate that can reach 115 in the summer.
There is no debating that a turbo mounted close to the engine will spool faster and make more power than a rear mounted setup, which is simple physics. The advantage of the rear mounted turbo is it's simplicity in installation. Its downside is it's complexity in getting it to function correctly. More piping means more of a chance for boost leaks and exhaust leaks before the turbo.
A rear mount turbo is capable of spooling quickly and making a lot of power. How well it does this is determined by the mechanical setup of the system as well as the tune. If the setup is good it can be similar in performance to a traditionally mounted turbo in the engine bay. If it is setup poorly, it's slower than a short bus full of window lickers.
The basics of getting the turbo to spool fast are keeping as much heat in the exhaust stream as possible and minimizing back pressure after the turbo.
Chapter 2... The Empire Strikes Back!
The rear mount turbo, loved by some, despised by others. How can such a simple device as a turbo and it's where it's located stir as much hatred as it does. Perhaps the hatred is due to latent homosexuality since rear mount turbo users "like their turbo in the butt". Who knows.
The first results from a lot of rear mount turbo users were dismal and received lots of hate from the traditionalists. Hearing taunts such as "that thing won't spool until next week" and reports of end users claiming very little performance gain were not uncommon. Some were happy users; others were selling off their kits for other "better" solutions. Things were not well, the Empire was pleased.
Chapter 3... Use the Force!
Eventually end users started to listen to the cries of partially correct dissenters who claimed a turbo runs off of heat (they run off of heat and pressure). They started to insulate their exhaust piping and swap headers for stock manifolds, anything to keep the heat in the exhaust stream. Surface area is the enemy. The more surface area on your exhaust system, the faster it gets rid of the heat. Headers are the worst mod on a rear mounted turbo setup. They have a very large surface area compared with exhaust manifolds. That large surface area is also at the point where the exhaust is it's hottest, the point where you want to keep the most heat possible.
Exhaust heat causes the volume of the gas to be larger. That larger volume of gas in a confined area equals more pressure. More pressure equals faster spool. Pressure is both friend and foe though. As much as pressure can help you, it can hurt you. Too much pressure and things start to choke up.
Hot exhaust gas has much more energy and pressure than cool exhaust gas. Without a waste gate before the turbo to bleed off some of this exhaust, the turbo would spool to its maximum. The waste gate lets us regulate how much of the exhaust is actually making it to the turbo and regulate the amount of boost produced by the compressor side. The goal is to supply the turbo with just enough exhaust energy to spool up as quickly as possible to the set boost level and then bypass the rest of the exhaust gas. The best way to bypass extra exhaust gas is a larger exhaust housing or a larger exhaust wheel or both. The hotter your exhaust gas the less of it you need to spin the turbine wheel of the turbo. This means the hotter exhaust gas is more efficient at doing the work. Since you don't need all of it to do the work, you can bypass the extra. Bypassing this extra gas causes the backpressure to drop which allows the cylinders to fill easier. If you don't bypass this extra exhaust gas your engine tends to choke at higher boost levels and RPMs due to excessive exhaust back pressure. It becomes more difficult for the engine to ingest more air when it can't get all of the spent exhaust out of the combustion chamber because it's fighting the exhaust back pressure. Controlling this backpressure and maintaining decent spool can become a delicate balancing act. Bypass too much and your setup spools slow and might not be able to make as much boost as you desire. Bypass too little and you run into excessive back pressure and possibly over running the flow of you waste gate causing you boost creep, poor power and increases your chance of detonating.
Last edited by Zombie; 11-28-2007 at 05:58 PM.
11-28-2007, 04:29 PM
#2
I'll use my car as an example (I don't have any other examples, HAH!) of how important keeping this heat in the exhaust is and how backpressure can affect the performance of your setup.
I started out with a T67 using a P-Trim exhaust wheel and a .81 a/r exhaust housing. My car had a 10:1 compression 346 LS1 engine with SLP long tube headers. This turbo spooled decent (how little I really knew). Would make 10 psi of boost and was fun to drive. I then tried to turn it up. I managed to get 14psi regularly but it struggled to go any higher. I could occasionally reach 16psi in high gear, but it was difficult and took a long time.
Best 1/4 mile pass: 11.7 @ 126 MPH, 15psi
14.5psi waste gate spring = 10psi
I then decided to try a Innovative T76 R-trim wheel with a .81 a/r exhaust housing. The car would make 5psi of boost quickly but then take until 6000 rpms until it would reach 11psi in high gear. Even if I blocked off the waste gate completely. Frustrated by this, I broke out my trusty credit card and purchased a .70 a/r housing and installed it. The result was excellent, I could now make 12psi and then slowly creep up to 14psi and occasionally it would reach 16psi in high gear. It spooled the same at the T67 but made a little more power.
Best 1/4 mile pass: 11.7 @ 127 MPH, 15psi
14.5psi waste gate spring = 11psi
In my quest to go ever faster, I changed my setup. I replaced the stock engine with a 8.7:1 comp 370 cu inch iron block Ls1 and a Th400 transmission. The previous transmission was a T56 6speed. While still running the same 3" exhaust after the turbo .70 a/r housing and 15psi I managed to go faster.
Best 1/4 mile pass: 11.3 @ 128 MPH, 15psi
14.5psi waste gate spring = 11psi
I still had problems though. I could only build a little boost on the line or none at all, boost was limited to 15psi max even with the waste gate blocked off and it took forever to get there. I decided to get rid of the headers and go back to stock manifolds. Wow what a difference! Now the car spooled faster and make 15psi reliably. The power range was very limited though. I was making my shifts at 5700 rpms because power was falling off fast after that and it would get detonation even on 100 octane gas if I revved past 6000. It spooled so well that I decided to try the .81 a/r housing again. I barely noticed any difference in spool time, but now the car felt like it was making a little more power. It spooled slowly on the transbrake (about 5 seconds to get 10psi) and I had to leave on 10psi of boost to get a good 60' (1.6x
range) because it would reach max boost faster that way, but it was working.
Best 1/4 mile pass: 10.54 @ 129.9 MPH, 16psi
14.5psi waste gate spring = 11psi
I started doing some research; I measured my back pressure and was seeing 45psi of back pressure at 15psi of boost. After talking to some more people it appeared that back pressure was still killing my performance. In my research I had found out that having your exhaust after the turbo to be 1.5 (or more) times the diameter of the exhaust wheel was better for back pressure after the turbo I had a new exhaust setup made up. The old exhaust was a 3.5' section of 3" pipe off the turbo exiting behind the rear wheel, it was a straight shot with no bends. I didn't think that this could be the problem but figured I'd give it a shot any ways. My exhaust housing used a 3.5" v-band to make the connection and I basically had a 3" exhaust butted right up against it. The new piece used a 3.5" v-band to a 3.5" to 4" transition and then a 4"
90 degree dump. Total exhaust length after the turbo, about 1 foot. The result was excellent, faster spool! Top end power seemed to be better but I was still limited to 16psi of boost even with the waste gate blocked off. It would build to 13 and then slowly go up to 16psi from there.
Best 1/4 mile pass: 10.56 @ 131 MPH, 16psi
14.5psi waste gate spring = 12psi
The waste gate was not opening at high boost. I didn't have enough exhaust energy to be bypassing any exhaust, it was taking every molecule of exhaust to reach 16psi (slowly). I talked to my friend Jon Whittington (he built my car and turbo setup) about this. After some discussion and further research we decided that it was the lack of heat in the exhaust causing us issues. He tried the experiment first on his car. He had a completely stock exhaust setup that spooled well to 12psi on a stock engine and a T70 .81 p-trim turbo. He swapped out to Jet hot long tubes. The result was amazingly disappointing. With no other changes besides the long tubes, the car
would barely build 5psi of boost and took seconds to even achieve that. He then pulled the exhaust system and headers off the car and wrapped it in header wrap. The result was fantastic, it spooled as well as it did on the stock uninsulated exhaust. Seeing how well this worked I decided to have him fabricate an entire new exhaust system for me. The exhaust is made out of 2.5" OD from the manifolds to the turbo and then insulated with fiberglass header wrap to just over the rear axle (we ran out). The end result of this was much much faster spooling and I could now achieve 20psi of boost with the waste gate still opening. I now had to leave on 5-6psi of boost because
it spooled so much faster it would blow the tires off if I left higher. It would also build 10psi of boost in 2.5 seconds now when using the transbrake, a huge improvement.
Best 1/4 mile pass: 10.13 @ 132 MPH, 19psi (best MPH of 134.55)
14.5psi waste gate spring = 13psi
Chapter 4... Return of the Jedi
I've now swapped to a .96 a/r housing. The turbo spools identically as it did on the .81 housing but it makes much more top end power. Instead of shifting at 6000 like previously I'm now able to shift it at 6500 and the power doesn't fall off. I'm hoping to get track results on this setup soon.
Best 1/4 mile pass: x.xx @ xxx MPH, 20psi
14.5psi waste gate spring = 14.5psi
The car feels like a completely different animal on this housing, the top end is
amazing, it actually feels like a turbo car should now. It took 3 years to get the car to this point by making a lot of small changes and observing how they affected it.
(keep in mind that I run at a track at high elevation that often sees 5000+ density altitude when trying to compare times to sea level tracks)
Chapter 5. Epilogue
Trying to go fast with a rear mounted turbo is possible and there are a few doing it, one car has even made it to the 7's and at least 3 others that have run 9's. It's not easy and not everyone will share their tricks and research which makes it harder for others to duplicate. If you quest is for get ET slips then changing to a built automatic is the easiest and cheapest route. Some people are die hard 6 speed fans like I use to be, but once you experience how much fun a built RMVB trans braked Th400 is you might change your mind. A huge advantage of an auto is that it never drops boost between shifts and shifts faster than any human can. It can take some experimentation with torque converters to get it to behave exactly the way you require though.
You don't have to spend a lot of money on parts to go fast on a turbo setup either. Most of the parts on my engine are stock with the exception of the pistons and rods. You don't have to spend a lot of money on high flowing heads and a magical cam either, the stock parts will do just fine. If you do spend the money for a nice set of heads and a good turbo cam you will make more power at a lower boost. I suggest against them when first starting out since it's a lot of extra cost that could be used towards getting the car running.
My setup is simple:
6.0 iron block bored .030 over
Diamond 4.030 dished pistons
Eagle I-Beam SBC 6.125 rods
60lb/hr injectors
Stock 317 heads with good springs (130 seat pressure)
Stock valves
Stock 02+ Z06 cam
stock intake
stock exhaust manifolds
2.5" custom exhaust wrapped in DEI header wrap (no cats)
ITS T76 R trim turbo with .96 a/r housing
Ebay intercooler
SMC Methanol kit
Rossler Th400 with transbrake
Vigilante 9.5" converter made as tight as they could make it
Moser 30 spline 9" with 2.75 gears and a spool
Hoosier 275/50/15 drag radial tires on 15x8 wheels
Only suspension mods are a RR airbag and BMR LCA's
I hope some of this will help some of the rear mount turbo guys out who are trying to go faster.
Jeremy Wolf, aka ZombieSS/Zombie
Credits:
1320 AKA Jon Whittington (my fabricator)
JZ 97 SS 1500 AKA Jose from forced inductions
EnineerMike (knows his physics and compressor theory)
(If I got any theory wrong let me know so I can correct it)
I started out with a T67 using a P-Trim exhaust wheel and a .81 a/r exhaust housing. My car had a 10:1 compression 346 LS1 engine with SLP long tube headers. This turbo spooled decent (how little I really knew). Would make 10 psi of boost and was fun to drive. I then tried to turn it up. I managed to get 14psi regularly but it struggled to go any higher. I could occasionally reach 16psi in high gear, but it was difficult and took a long time.
Best 1/4 mile pass: 11.7 @ 126 MPH, 15psi
14.5psi waste gate spring = 10psi
I then decided to try a Innovative T76 R-trim wheel with a .81 a/r exhaust housing. The car would make 5psi of boost quickly but then take until 6000 rpms until it would reach 11psi in high gear. Even if I blocked off the waste gate completely. Frustrated by this, I broke out my trusty credit card and purchased a .70 a/r housing and installed it. The result was excellent, I could now make 12psi and then slowly creep up to 14psi and occasionally it would reach 16psi in high gear. It spooled the same at the T67 but made a little more power.
Best 1/4 mile pass: 11.7 @ 127 MPH, 15psi
14.5psi waste gate spring = 11psi
In my quest to go ever faster, I changed my setup. I replaced the stock engine with a 8.7:1 comp 370 cu inch iron block Ls1 and a Th400 transmission. The previous transmission was a T56 6speed. While still running the same 3" exhaust after the turbo .70 a/r housing and 15psi I managed to go faster.
Best 1/4 mile pass: 11.3 @ 128 MPH, 15psi
14.5psi waste gate spring = 11psi
I still had problems though. I could only build a little boost on the line or none at all, boost was limited to 15psi max even with the waste gate blocked off and it took forever to get there. I decided to get rid of the headers and go back to stock manifolds. Wow what a difference! Now the car spooled faster and make 15psi reliably. The power range was very limited though. I was making my shifts at 5700 rpms because power was falling off fast after that and it would get detonation even on 100 octane gas if I revved past 6000. It spooled so well that I decided to try the .81 a/r housing again. I barely noticed any difference in spool time, but now the car felt like it was making a little more power. It spooled slowly on the transbrake (about 5 seconds to get 10psi) and I had to leave on 10psi of boost to get a good 60' (1.6x
range) because it would reach max boost faster that way, but it was working.
Best 1/4 mile pass: 10.54 @ 129.9 MPH, 16psi
14.5psi waste gate spring = 11psi
I started doing some research; I measured my back pressure and was seeing 45psi of back pressure at 15psi of boost. After talking to some more people it appeared that back pressure was still killing my performance. In my research I had found out that having your exhaust after the turbo to be 1.5 (or more) times the diameter of the exhaust wheel was better for back pressure after the turbo I had a new exhaust setup made up. The old exhaust was a 3.5' section of 3" pipe off the turbo exiting behind the rear wheel, it was a straight shot with no bends. I didn't think that this could be the problem but figured I'd give it a shot any ways. My exhaust housing used a 3.5" v-band to make the connection and I basically had a 3" exhaust butted right up against it. The new piece used a 3.5" v-band to a 3.5" to 4" transition and then a 4"
90 degree dump. Total exhaust length after the turbo, about 1 foot. The result was excellent, faster spool! Top end power seemed to be better but I was still limited to 16psi of boost even with the waste gate blocked off. It would build to 13 and then slowly go up to 16psi from there.
Best 1/4 mile pass: 10.56 @ 131 MPH, 16psi
14.5psi waste gate spring = 12psi
The waste gate was not opening at high boost. I didn't have enough exhaust energy to be bypassing any exhaust, it was taking every molecule of exhaust to reach 16psi (slowly). I talked to my friend Jon Whittington (he built my car and turbo setup) about this. After some discussion and further research we decided that it was the lack of heat in the exhaust causing us issues. He tried the experiment first on his car. He had a completely stock exhaust setup that spooled well to 12psi on a stock engine and a T70 .81 p-trim turbo. He swapped out to Jet hot long tubes. The result was amazingly disappointing. With no other changes besides the long tubes, the car
would barely build 5psi of boost and took seconds to even achieve that. He then pulled the exhaust system and headers off the car and wrapped it in header wrap. The result was fantastic, it spooled as well as it did on the stock uninsulated exhaust. Seeing how well this worked I decided to have him fabricate an entire new exhaust system for me. The exhaust is made out of 2.5" OD from the manifolds to the turbo and then insulated with fiberglass header wrap to just over the rear axle (we ran out). The end result of this was much much faster spooling and I could now achieve 20psi of boost with the waste gate still opening. I now had to leave on 5-6psi of boost because
it spooled so much faster it would blow the tires off if I left higher. It would also build 10psi of boost in 2.5 seconds now when using the transbrake, a huge improvement.
Best 1/4 mile pass: 10.13 @ 132 MPH, 19psi (best MPH of 134.55)
14.5psi waste gate spring = 13psi
Chapter 4... Return of the Jedi
I've now swapped to a .96 a/r housing. The turbo spools identically as it did on the .81 housing but it makes much more top end power. Instead of shifting at 6000 like previously I'm now able to shift it at 6500 and the power doesn't fall off. I'm hoping to get track results on this setup soon.
Best 1/4 mile pass: x.xx @ xxx MPH, 20psi
14.5psi waste gate spring = 14.5psi
The car feels like a completely different animal on this housing, the top end is
amazing, it actually feels like a turbo car should now. It took 3 years to get the car to this point by making a lot of small changes and observing how they affected it.
(keep in mind that I run at a track at high elevation that often sees 5000+ density altitude when trying to compare times to sea level tracks)
Chapter 5. Epilogue
Trying to go fast with a rear mounted turbo is possible and there are a few doing it, one car has even made it to the 7's and at least 3 others that have run 9's. It's not easy and not everyone will share their tricks and research which makes it harder for others to duplicate. If you quest is for get ET slips then changing to a built automatic is the easiest and cheapest route. Some people are die hard 6 speed fans like I use to be, but once you experience how much fun a built RMVB trans braked Th400 is you might change your mind. A huge advantage of an auto is that it never drops boost between shifts and shifts faster than any human can. It can take some experimentation with torque converters to get it to behave exactly the way you require though.
You don't have to spend a lot of money on parts to go fast on a turbo setup either. Most of the parts on my engine are stock with the exception of the pistons and rods. You don't have to spend a lot of money on high flowing heads and a magical cam either, the stock parts will do just fine. If you do spend the money for a nice set of heads and a good turbo cam you will make more power at a lower boost. I suggest against them when first starting out since it's a lot of extra cost that could be used towards getting the car running.
My setup is simple:
6.0 iron block bored .030 over
Diamond 4.030 dished pistons
Eagle I-Beam SBC 6.125 rods
60lb/hr injectors
Stock 317 heads with good springs (130 seat pressure)
Stock valves
Stock 02+ Z06 cam
stock intake
stock exhaust manifolds
2.5" custom exhaust wrapped in DEI header wrap (no cats)
ITS T76 R trim turbo with .96 a/r housing
Ebay intercooler
SMC Methanol kit
Rossler Th400 with transbrake
Vigilante 9.5" converter made as tight as they could make it
Moser 30 spline 9" with 2.75 gears and a spool
Hoosier 275/50/15 drag radial tires on 15x8 wheels
Only suspension mods are a RR airbag and BMR LCA's
I hope some of this will help some of the rear mount turbo guys out who are trying to go faster.
Jeremy Wolf, aka ZombieSS/Zombie
Credits:
1320 AKA Jon Whittington (my fabricator)
JZ 97 SS 1500 AKA Jose from forced inductions
EnineerMike (knows his physics and compressor theory)
(If I got any theory wrong let me know so I can correct it)
Last edited by Zombie; 11-28-2007 at 05:08 PM.
The following 2 users liked this post by Zombie:
crw3673 (05-15-2020), Homer_Simpson (02-09-2024)
11-28-2007, 04:51 PM
#4
So what I get from reading that novel is what common sence tells you, the more heat you can have at the turbine wheel the better. After all theory of a turbine is HOT expanding gases is what makes it work. So in any rear mount turbo set up all the band-aiding you can do will help, BUT not as much as moving the turbo closer to the hot expanding gas source IE the engine.
What it all boils down to is if you want to make serious power front mount is the only way to fly.
Can you make power with a rear mount? Yes. Is it the most efficent way of making power? Probably not.
Before the flame war starts, yes I know some guys will argue packaging, ease of install etc, and they are right. I want lots of power, and dont mind doing my homework to make the power. After all anything worth doing is worth doing right. 
What it all boils down to is if you want to make serious power front mount is the only way to fly.
Can you make power with a rear mount? Yes. Is it the most efficent way of making power? Probably not.
Before the flame war starts, yes I know some guys will argue packaging, ease of install etc, and they are right. I want lots of power, and dont mind doing my homework to make the power. After all anything worth doing is worth doing right. The following users liked this post:
stngh8r (10-29-2019)
11-28-2007, 05:04 PM
#5
So what I get from reading that novel is what common sence tells you, the more heat you can have at the turbine wheel the better. After all theory of a turbine is HOT expanding gases is what makes it work. So in any rear mount turbo set up all the band-aiding you can do will help, BUT not as much as moving the turbo closer to the hot expanding gas source IE the engine.
BTW, I don't know what you consider "serious power", but I've got way more power than I can even hope to hook on the street, even at 14.5 psi. It's definately "fast enough" when talking in terms of street cars. The "I want a 1000 RWHP" dreamers I see posting every know and then don't have a clue what they even want lol. I don't want 1000 RWHP on the street, what I have now is scary enough.
Last edited by Zombie; 11-28-2007 at 05:12 PM.
The following users liked this post:
crw3673 (05-15-2020)
11-28-2007, 05:18 PM
#6
When are you planning to step up to something a little bigger then the ITS76. I would imagine your pretty much choking that thing by now. Impressive times though for the setup and being a rear-mount.
Yes some of it is common sense, but to many it is not. Most of the people going the rear mount turbo route want street cars, not max effort race cars. The purpose of my novel is to show how everything affected the car. There are a lot of noobie users especially with STS setups. This post is mainly directed at them (and anyone else who cares to read my story). This is my experience I've had over the last 3 years with examples of how the setup was improved at each major step. Four years ago most people swore that a turbo couldn't possibly work when mounted in place of the muffler. I've posted all my success and failures on this board and this is a summary of what has worked well for me. This is the kind of information I use to search for when trying to make my setup better but couldn't find easily. I know most people are probably going to ignore this information and do their own thing anyways, but I'm pretty sure there are a few that don't want to reinvent the wheel when doing a rear mount setup.
BTW, I don't know what you consider "serious power", but I've got way more power than I can even hope to hook on the street, even at 14.5 psi. It's definately "fast enough" when talking in terms of street cars. The "I want a 1000 RWHP" dreamers I see posting every know and then don't have a clue what they even want lol. I don't want 1000 RWHP on the street, what I have now is scary enough.
BTW, I don't know what you consider "serious power", but I've got way more power than I can even hope to hook on the street, even at 14.5 psi. It's definately "fast enough" when talking in terms of street cars. The "I want a 1000 RWHP" dreamers I see posting every know and then don't have a clue what they even want lol. I don't want 1000 RWHP on the street, what I have now is scary enough.
11-28-2007, 05:39 PM
#7
Thanks for taking the time on the excellent post. Im not a fan of rear mounts by any means, but it seems to be working very well for you. So if it works, more power to ya. I was curious if getting the stock manifolds coated would help reduce spool time any further. Thats one of the first things that came to mind when I read that.
Good Luck
Good Luck
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11-28-2007, 05:50 PM
#8
It should, but I don't know anyone who has done it or if the difference would be worth the cost. I've taken the route of best bang for my buck (I'm a cheap bastard).
11-28-2007, 06:10 PM
#10
Launching!
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What about a 408 fully built with Dart 225 fully ported and so on.Could you use stock manifolds because I run long tubes with a wrapped exhaust on my STS kit.I am Installing a Garrett T88 with a 108 exhaust houseing that is already coated.Not trying to hijack your post put would like your input.THANKS.
11-28-2007, 06:25 PM
#11
What about a 408 fully built with Dart 225 fully ported and so on.Could you use stock manifolds because I run long tubes with a wrapped exhaust on my STS kit.I am Installing a Garrett T88 with a 108 exhaust houseing that is already coated.Not trying to hijack your post put would like your input.THANKS.
Your goal is to keep as much heat in the exhaust as possible, I'd even consider double wrapping it.
11-28-2007, 06:36 PM
#12
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I was curious about the stock manifolds I figured they would choke the 408.What cubic inch do you run.The turbo will be a winter project I am going from t4 to t6 flange and a 5" inlet 5"exhaust and 3 1/2" outlet.Which is going to take alot of pipeing change.Then I got to get that big a$$ turbo to tuck up nice.
11-28-2007, 06:55 PM
#13
I was curious about the stock manifolds I figured they would choke the 408.What cubic inch do you run.The turbo will be a winter project I am going from t4 to t6 flange and a 5" inlet 5"exhaust and 3 1/2" outlet.Which is going to take alot of pipeing change.Then I got to get that big a$$ turbo to tuck up nice.
With the power goals you are aiming for I would strongly consider selling off the rear mount kit and purchasing something else. You are making a large investment in time and money for an experiment.
When it comes to exhaust manifolds and headers I don't know if you can think of them in the traditional sense of flow. When you have a turbo sitting after them they now hold many times the normal pressure and the air is being forced through them in the same way that boost forces it's way into the intake. More flow mean more power, but how much more or where the limit is on a manifold exhaust setup I have no idea.
11-28-2007, 08:23 PM
#14
Best and most imformetive write up Iv'e seen on rear mounts.Your results speak for themself.Pretty impressive results for what you are working with and obviously you're not done yet!I like to read about all kinds of setups and different ways to improve them.If everyone had exactly the same setup how boring would that be?Keep up the good work!
11-28-2007, 08:30 PM
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Do you think the t88 that I have would work for a frontmount setup.I have been considering that I just didnt want to start over with another setup.But if it has to be done then so be it.Thanks for all the helpful info.
11-28-2007, 08:32 PM
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I am a huge rear mount fan and am in the slow process of a custom twin set up. I REALLY thank you for you info on housings and pipe size. Tucson is alot like vegas track sometimes the corrected alt. is over 4500' and no humity to help out either.
I am (was) having a hard time decideing if I should go with .63 or .48 housings ( to4e/t3) but I pretty sure I'll go with the .48's. I am tucking them up in the pockets behing the rear tires. I too have went with 2.5 pipe and when fabrication is done, I also thought about double wraping. I have not started the cold side becase I have to faricate custom SFC to use as intake piping. What size is you Intake pipe? and have you played with these sizes at all. I am stuck between 2" or 2.25" on each side to a, 2 in 1 out fmic) . Thanks again.
I am (was) having a hard time decideing if I should go with .63 or .48 housings ( to4e/t3) but I pretty sure I'll go with the .48's. I am tucking them up in the pockets behing the rear tires. I too have went with 2.5 pipe and when fabrication is done, I also thought about double wraping. I have not started the cold side becase I have to faricate custom SFC to use as intake piping. What size is you Intake pipe? and have you played with these sizes at all. I am stuck between 2" or 2.25" on each side to a, 2 in 1 out fmic) . Thanks again.
11-28-2007, 08:52 PM
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It should, but I don't know anyone who has done it or if the difference would be worth the cost. I've taken the route of best bang for my buck (I'm a cheap bastard).[/QUOTE]
I stepped up from a 67 to a tubonetics super t-76 BB. Moved the turbo to the back of a custom y-pipe. The turbo is about 18 inches closer to the engine now. The stock exhaust manifolds and y-pipe are geramic coated black. It spools up nearly identical to the 67. There are a few pics at this link.
http://www.cablebandit.net/gallery/v/Track+Days/Dave/
I stepped up from a 67 to a tubonetics super t-76 BB. Moved the turbo to the back of a custom y-pipe. The turbo is about 18 inches closer to the engine now. The stock exhaust manifolds and y-pipe are geramic coated black. It spools up nearly identical to the 67. There are a few pics at this link.
http://www.cablebandit.net/gallery/v/Track+Days/Dave/
11-29-2007, 10:29 AM
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I went 10.20 a year ago on a stock long block and my turbo set up. Zombie s car still has a lot left, these things are lot more $ and time driven then anything else.
11-29-2007, 11:06 AM
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very nice writeup! however, i believe the main thing that greatly helped your spooling was the 2.5" exhaust going to the turbo. I have LT's, as well as 2.5" piping and mine spools up pretty quick and could only get better if i switched to stock manifolds and wrapped it up....
i think most people would get better results switching to smaller exaust tubing first, rather than just wrapping it up and/or using stock manifolds... but hey, if you can do all three at once then it will be that much better... just my observation!
also do you have the oil return going to the pan?
i think most people would get better results switching to smaller exaust tubing first, rather than just wrapping it up and/or using stock manifolds... but hey, if you can do all three at once then it will be that much better... just my observation!
also do you have the oil return going to the pan?