remote mounted turbo systems

[aspera]

http://ststurbo.com/home

Check this out. Better yet, check out the latest 'turbo' magazine for more info.

This turbo system is basically a clever packaging solution. So clever, that it seems to overcome the obvious drawbacks to remote mounting.

Most of you will have a knee jerk reaction and blurt out something about turbo lag. Yes and no. Mostly no. This is a 'light pressure' turbo setup...like on SAABs. The stock compression ratio isn't changed. Boost is moderate. All eight cylinders on a V8 are spinning one larger turbo instead of two smaller turbos. Larger turbos are generally more efficient. Larger engines (V8 truck engines) are already tuned for low end torque and throttle response...so the turbo doesn't need to be. Why make more power at low RPM anyway? The tires just spin. In my opinion, a single, large light pressure turbo is a great match for a domestic V8. The only things left to cause turbo lag are the VOLUME of the exhaust and intake pipes. Since there is no intercooler VOLUME, then those pipes won't cause much lag. The exhaust piping to the turbo can be smaller and straighter than a normally aspirated performance exhaust. The pipe after the turbo can be huge and short...creating a better pressure ratio across the turbine. The compressor inlet tube can also be big, short and straight. All that is left is to minimize the bends of the pipework going to and from the engine.

I still worry about the cat and the stock O2 sensor. How will they survive the add-on turbo? They weren't designed to deal with the pressure.

If this technology were applied to an XJ, then you'd have to worry about keeping the turbo protected from rocks, water and dust. A skidplate and snorkel would do it. There are 4 locations the come to mind.

1. Turbo where muffler used to be. I'm luke warm.
2. Turbo where gas tank used to be. Use a fuel cell inside, like Jeepspeed.
3. Turbo in custom back bumper! For a few more feet, you get absolutely straight intake and tail pipes. Air goes in left side COLD---comes out right side HOT. :laugh:
4. ***hardest-core option*** Turbo in custom front bumper. NO exhaust under the Jeep.

Other little things make me like the remote mount turbo, like weight distribution and stealth. Weight is low and in the rear. No sign of turbo in the engine bay. I'd like to see something like this on the 6.1L Hemi Charger in a few years. :looney:

 

[aspera]

I think the turbo article stated that the exhaust pipes were coated to insulate and the intake pipes were coated to radiate the heat.

 

[aspera]

One more thing--the wastegate can dump to atmo. They say that it is quieter, too...due to the greater distance from the engine. You don't even need a 'screamer pipe'.

 

[aspera]

"Most people think this will not work because you have to have heat to produce boost. Boost is produced from air flow across the turbine making it spin. We do lose heat energy and velocity, but there is still the same amount of mass coming out of the end of the exhaust as there is right out of the head. The gas coming out of the tailpipe, or in this case into the turbo is denser but still has the same number of gas molecules at different temps. If its in the front, the volume is so much that the turbine housing must be larger so that will not get restricted and cause back pressure. Smaller housing increases velocity w/o extra backpressure because the gas is smaller and denser. That is what I mean when I say they are sized to work in the rear."

I thought this was pretty neat. The turbo is sized for the loss of heat and velocity. It just works on airflow. No mention of exhaust pulses that I could find.

 

[BigDadys94xj]

Ok after reading your post there are a few things I must dispute.Being a mechanical engineer I see some flaws. First of all turbos by there nature run very hot so mounting it in a custom front bumper may not be the best thing to do (unless of course you vent it alot) but this to creates problems with dirt, debris, bugs ect. Also you stated that building alot of horse power at low rpms was not good because you would just spin your tires. Well if you only run on the street and drag race this is fine but most of the members in the forums run their XJ's offroad at slow speeds for rock crawling, muding, trail riding ect. So you want most of your horse power built at these low rpm's. This not a good application for a turbo system do to the fact that you would never build enough boost pressure at these rpm levels to make a turbo effective. Plus cooling a motor at these slow speeds for extended periods of time is crucial and adding a turbo would like signing a death warrant for your engine when offroading (unless you add sufficient cooloing).
The other thing I dispute is that this article seems to be all about adapting one of these turbo systems to a v8. This is ok if you have ZJ but the last time I checked most of the people here are running 4.0 i6 or 2.5 i4's (very few have made a v8 swap. Due to the engineering of inline motors there is not a hell of alot of room on the drivers side of the motor to run all the nessasary plumbing for a turbo. If this is something you seriously want to persue for your rig you better read more about them and match whatever you use to your specific application. Good Luck.
J

 

[DangerBoy]

Reviewed the Tacoma set up on their website... and the air intake is under the truck???? that would work just swell for us up here in mud and water country.... by the time you get all the plumbing together to get the air intake up out of harm's, water or mud's way and pay for the turbo itself and install this thing you could have done some other pretty serious mods that would improve off road capabilities... to many times I have needed to feather the throttle and having the boost suddenly kick in at the wrong time would be troublesome at best. My 4.0 has plenty of torque especially in 4 low so I dont see a point unless you are interested in street performance.... and then i gotta ask why are you driving a jeep.

 

[CW]

I can't even imagine what the lag would be like on that. I larger turbo takes longer to spool up, and from what I read, they are using a larger than normal turbo for the application. Add to that, that the distance between the engine and turbo increases lag. So mounting the turbo at the end of the tail pipe would be rediculous. Plus it is exposed to the elements, the intake is drawing air that has debree in it because the tires kick dust and other crap up. A properly enginered, under the hood turbo would be the best option by far, other than a super-charger.

 

[aspera]

The front bumper idea would allow the turbo to sit outside of the engine bay (advantage--keeping heat away from the engine), while keeping it relatively close to the engine (same end of the vehicle). Of course the bumper would have to deal with the heat. That means holes for venting and simple heat shields. Also, the 90lb steel bumpers on some XJs would help deal with the heat. Basically, I suggested designing an engine bay for the turbo itself. My Warn winch bumper gave me the idea of using the bumper.

When I made the comment about sizing the turbo for high RPM power, I was talking about the RWD V8 kits. 4WD *might* be different depending on application. For example: Mudding might work best with a turbo sized for midrange power. Peak power would be more important than throttle response.
Engine cooling is a problem on XJs even without a turbo. I assume that all supporting mods would be done before a turbo kit would be added.

I wouldn't bother with a turbo on my XJ's I6. I just started this post in case somebody else wanted to do it. Now if the Jeep had a proper crossflow head....maybe.

 

[aspera]

Reviewed the Tacoma set up on their website... and the air intake is under the truck???? that would work just swell for us up here in mud and water country.... by the time you get all the plumbing together to get the air intake up out of harm's, water or mud's way and pay for the turbo itself and install this thing you could have done some other pretty serious mods that would improve off road capabilities... to many times I have needed to feather the throttle and having the boost suddenly kick in at the wrong time would be troublesome at best. My 4.0 has plenty of torque especially in 4 low so I dont see a point unless you are interested in street performance.... and then i gotta ask why are you driving a jeep.

See, this is what makes me like the large displacement/low pressure/larger turbo setup. At low RPM the engine behaves like stock. You might lose a few horsepower slowly spinning the turbine *IF* you are at WOT. Otherwise you never notice it.

Then, when you need maximum boost...you just hold your foot down. Turbos spool up over time, and that time varies by RPM and load.

Feathering the throttle is something that is already built in to driving a turbo car. You really notice it when you back off of the throttle going uphill.

Throttle tip-in is set up softer on most offroad vehicles. Check out the info on how the drive-by-wire response was altered on the new Dodge Power Wagon. Funny how that is designed in, yet offroaders worry about turbo lag.

 

[aspera]

I can't even imagine what the lag would be like on that. I larger turbo takes longer to spool up, and from what I read, they are using a larger than normal turbo for the application. Add to that, that the distance between the engine and turbo increases lag. So mounting the turbo at the end of the tail pipe would be rediculous. Plus it is exposed to the elements, the intake is drawing air that has debree in it because the tires kick dust and other crap up. A properly enginered, under the hood turbo would be the best option by far, other than a super-charger.

No. They use a smaller turbo. I posted it. That's why it is SOOO clever. A hot turbo bolted to the exhaust manifold has to handle a larger VOLUME of air because it is HOT. The remote turbo sees less HEAT and therefore less VOLUME, but the same MASS of air. That means that is can squeeze the same MASS of air through a smaller turbine. That means quick spool-up.

Also, my theory is that the cool and dense slug of air has some inertia to it by the time it gets to the remote turbo.

A properly engineered underhood turbo would trade advantages with the remote turbo. Both turbo systems are superchargers. The key advantages are that boost isn't tied directly to load and the power to drive the compressor is from heat that is normally wasted. Example: A belt driven supercharger might make 2psi of boost per 1000 RPM. It ramps up to maximum boost at redline. If redline is 6000 RPM, then maximum boost is 12psi. A light pressure turbo setup might only make 10psi, but it might make it by 3000 RPM and hold it to redline. That means that most of the time the turbo is making much more boost. 10psi@3K for the turbo, 6psi@3K for the blower. Even at 2000 RPM the turbo only has to make 4psi partial boost to match the blower.

The turbo is powered by the energy that normally gets flushed out the exhaust pipe. The blower robs it from the crank. The blower also has a tendency to blow the air/fuel mixture right through the engine and out the exhaust. As boost pressure increases on the intake side of the supercharged engine, it stays nearly the same on the exhaust. This pressure differential, combined with valve overlap, blows right through the engine. The turbo builds pressure in the intake AND the exhaust much more evenly.

 

[BigDadys94xj]

Just remember you can never get something for nothing!Yes a crank driven supercharger does steal horsepower from the engine to run but it also builds more horsepower than it robs. Same with a turbo yes it uses exhaust flow which would normally be wasted going out the exhaust pipe but it also creates a certain amount of restriction which causes backpressure in the exhaust system which robs a certain amount of power from the engine until the turbo spools up. The main problem with a remote mounted turbo (front bumper) is that there will be a certain amount of pressure loss from the engine to the turbo because of distance from the engine. Heres an example hook a pressure gauge to a water faucet and measure the pressure, then attach a 50' hose to the faucet and check the pressure at the end of the hose, the pressure will be lower at the end. This pressure loss over distance will not allow for maximum efficeincey of the turbo. Yes using a smaller turbo would help but you would also need to use some pretty small tubing from the exhaust to the turbo to increase the velocity of the air going to the turbo to increase the efficeincy.

Just my 2 cents!

 

[aspera]

...so your arguement for a supercharger is that it builds a small amount of boost at low RPM for a fraction of a second until a turbo spools up and out-boosts it until redline with an overall greater efficiency?? Boy, that 1psi for .1 second IS better. heh heh :laugh3:

Yes, the turbine is briefly nothing but a restriction...but you do get something for nothing, sorta. The heat energy in a blower engine is pure waste after it gets out of the head. It just gets flushed. The heat energy in a turbo engine is exploited to spin the turbine to spin the compressor to supercharge the engine.

The modern turbo is actually two different machines. One is a power recovery turbine. PRTs were used on military piston aircraft years ago. The second part is the compressor, which is self-explanatory. They work very well together, but would work better by themselves.

http://www.enginehistory.org/Gallery/DickMerrill/3350with prt.JPG

In the picture you can see the PRT spins a shaft that directly drives the crankshaft. It works similarly to a crank driven supercharger, but in reverse. Air pressure is converted to crankshaft torque.

By connecting the turbine directly to the compressor without any contact to the engine's crank, the turbo RPM is free from the engine RPM. Good. That lets the turbo spool up before the engine can rev up. The blower is actually the one that has LAG. It can't reach its full RPM or boost until near redline.

 

[aspera]

The main problem with a remote mounted turbo (front bumper) is that there will be a certain amount of pressure loss from the engine to the turbo because of distance from the engine. Heres an example hook a pressure gauge to a water faucet and measure the pressure, then attach a 50' hose to the faucet and check the pressure at the end of the hose, the pressure will be lower at the end. This pressure loss over distance will not allow for maximum efficeincey of the turbo. Yes using a smaller turbo would help but you would also need to use some pretty small tubing from the exhaust to the turbo to increase the velocity of the air going to the turbo to increase the efficeincy.

Just my 2 cents!

I'm not sure the faucet test holds water. Liquids don't compress, so pressure would be the same. Exhaust gasses would decrease in pressure, however. That's bad, like you said. But that also works for the exhaust gasses after the turbo. In a normal turbo setup the after-turbo gasses have to pass down several feet of pipe. This exhaust cools and slows, which increases backpressure. In the remote turbo setup, there is enough heat to keep the air moving to the turbo and almost no pipework after it to cause backpressure. Also, the small pipes needed to feed the remote turbo hold the heat in and keep the velocity up, but flow well since they are pressurized.
Small pipes for high pressure, big pipes for low pressure.