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Though not planning on doing this anytime soon as I have too much on my plate right now, the idea of a rear mounted turbo on my 78 sounds awesome. Has anyone on here attempted such a thing?
Some questions come to mind:
would you go single exhaust to one turbo or twins?
oil cooled or water cooled?
how to figure out what size turbo(s)?
how many pounds of boost can be run safely?
would my holley be sufficient as a blow thru carb? (after removing the choke and changing the floats)
could my two bolt main handle the added power? (currently run aftermarket cast heads, long tubes, performer intake and a mild cam)
Anyone know if that system ran an intercooler too. it seems to me it would cool the charge air a little traveling all that way. on a c3 I think it's better under the hood as there is limited room under the car.
I would think that the biggest disadvantage of a C3 for a rear mounted Turbo ( or any Turbo mounted anywhere) compared to a newer car is that its not Fuel Injected and there isn't a ECM to run the show.
Anyone know if that system ran an intercooler too. it seems to me it would cool the charge air a little traveling all that way. on a c3 I think it's better under the hood as there is limited room under the car.
I don't believe it did, I read that the air was cooled enough in the travel from the rear of the car forward on sts kits, plus its already drawing cooler air outside of the engine bay
I would think that the biggest disadvantage of a C3 for a rear mounted Turbo ( or any Turbo mounted anywhere) compared to a newer car is that its not Fuel Injected and there isn't a ECM to run the show.
I'd have to agree but if vortech can do a supercharger with a carb hat then why not?
The power recovered by turbo-charging is from the HEAT of the exhaust system. By moving the turbos to the rear, you run the risk of losing a lot of efficiency from heat losses from tubing getting the exhaust to the rear of the car. If you can insulate that tubing well enough, you might be able to salvage most of the exhaust heat; if not, you should just save your money.
2020 Corvette of the Year Finalist (performance mods)
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I saw that system on a custom mustang at a local show. The guy said it was super expensive and the shop said it was kind of a hassle. I believe the turbo actually works with the gas flow which is why there is a turbo lag as the turbine spools up and the idea for the distance is that the cooler gases will prolong life of the turbo bearings. The cooler air will keep the power boost up with better air\fuel ratio as the forced air isnt exchanging heat through the turbine housing, assisting the intercooler with cooling the compressed in coming gases. The engine wants cold outside air.
BUNK! Hotter gases means higher pressure. As heat is lost, pressure goes down. As pressure goes down, potential energy is lost to the environment...rather than to the turbo. Simple as that.
I've ridden in a couple of these STS cars over the years and I'll say for a fun street car...they run very well. They run small turbos that spool quickly. The size of the pipe is critical....but seems to work well overall. Is it the ultimate power adder? No.....but it is very effective. One thing you have to be aware of is scavenging the oil with a pump usually and pumping it back to the engine or to a tank/cooler etc.
I was able to mount twins in the "gill" area of my '67 without too much drama...certainly a C-3 could be done the same way.
BUNK! Hotter gases means higher pressure. As heat is lost, pressure goes down. As pressure goes down, potential energy is lost to the environment...rather than to the turbo. Simple as that.
It's not as simple as that. Hot gas by itself doesn't do much. The turbine also needs one of two things: a pressure differential across it to get the gas flowing into the turbine housing, or high speed gas hitting the blades (momentum transfer). The drop in pressure and temperature across the turbine shows that some work has been done (driving the compressor wheel).
The power recovered by turbo-charging is from the HEAT of the exhaust system.
Originally Posted by 7T1vette
BUNK! Hotter gases means higher pressure. As heat is lost, pressure goes down. As pressure goes down, potential energy is lost to the environment...rather than to the turbo. Simple as that.
I really, really (really) (I mean...REALLY...) don't want to go down the rabbit hole of a 'toobroke' type discussion, but I have to question the above statements.
I offer an agreement that higher heat equals higher pressure. But I don't believe that any increase in the pressure INSIDE THE EXHAUST PIPE due to the temperature of the gasses INSIDE THE EXHAUST PIPE is the chief/paramount mechanism that is rotating the turbo.
A turbocharger is not a heat exchanger and its performance is not driven or measured by the temperature of the incoming gasses. I DON'T DISAGREE that there may be an increase/decrease in overall performance of the turbocharger related to the temperature of the incoming gas charge, but that is not the 'thing' that creates the power.
The "turbine" side of the turbo responds to the velocity/volume of exhaust gases passing over the vanes. They are generally "cupped" to accept the gasses that flow over them to capture as much of the gas as possible. The "turbine" side is then connected via a hard shaft to the "compressor" side which "accelerates" the air within the intake air charge, hopefully feeding more air to the engine than it is taking in, creating a buildup of pressure within the engine intake...positive manifold pressure...which is the 'thing' that gives you all the power. You're shoving air into the engine instead of it having to suck against a vacuum.
The AMOUNT OF FLOW that is turned into actual work that spins the compressor side of the turbocharger is what defines the efficiency of the turbo. The easiest way to evaluate this efficiency would be to measure the "Delta P"...the change in pressure...across the turbine. The difference between the high pressure on the upstream side compared to the low pressure on the exhaust tip side would tell you how much of the exhaust is being turned into work.
I would speculate that the turbo system would respond well to a more stable/laminar flow into the turbine side of the turbocharger...an opinion that would speak to a positive of having a longer, straighter pipe feeding the turbine side. This would decrease the pulsations of individual cylinders firing and give a more stable "blow" across the turbine vanes.
Again...perhaps there is a positive to having heat in the exhaust charge that passes over the turbines. Simply because hot air takes up more room than cooler air and that would allow there to be a (slightly) greater pressure within the exhaust tube before the turbine. This would allow a greater possible "Delta P" on the upstream side.
HOWEVER, I would counter the argument that a hotter exhaust charge would have lower density and that the lower density of the charge passing over the vanes could/would impact the efficiency of the vanes capturing the exhaust charge.
I will call those two speculations...yours about heat/pressure and mine about density/efficiency...competing notions that are negligible to the overall function of the turbo.
Therefore, I would politely offer the argument that a turbocharger will be very happy creating positive pressure to an intake charge even if the exhaust flow passing over the turbine side of the turbocharger is as cool as a raw clam.
Last edited by keithinspace; 12-12-2016 at 09:23 AM.
12-05-2016, 03:34 PM
Has anyone attempted rear mounted turbos?
