Supercharging

[EdKiefer]

Originally Posted by NHRABill

Don't think that there would be many that would argue that a turbo is the most eficient of the 3 types of forced induction. But a good ? is what turbo setup is most efficient?

I have always found the tailpipe turbo STS style is the best route for effiencey and installation No need for a intercooler when it is where the muffler is located. It keeps engine temps down and cools the charge in the longer travel distance back to the intake. I know someone with this setup but he is tuned for power not mpg

This is just my opinion but those STS rear mounted turbo I can't see how it can be efficient . they sure are good for installation and keeping heat down in engine bay but there are drawbacks from my point of view.

1) there long length from turbo to throttle-body induces lag as that whole length of pipe needs filling .
2) on the exhaust side having turbo back there is losing the heat and velocity of exhaust right out of head .

3) The oiling system is much more complicated as you need a pump to return oil back to sump and you are below pan level which means if pump goes bad oil back up into turbo center housing .

These comments are from working in performance industry, installing turbo kits and turbo/inter cooler upgrades. Some of the front mounted intercooler kits I can notice a lose of response and here were talking just few ft increase .

Now most of the cars they install in are big V8 so they probably don't hamper much but if it was small L4 or V6 IMO it would be noticeable.

Just look at OEM they don't mount turbo far away, its always to keep piping short as possible .

[comptiger5000]

Plus, rear mounted turbos have more turbo lag. A front turbo with adequate airflow and exhaust insulation to keep the engine bay from getting too hot would be best.

[NHRABill]

Thanks for all of the comments regarding the rear turbo. My point of view was not stated as I made my comments thinking about myself like always lol.

and as Ed K mentioned the noticeable difference will be much more pronounced in a small displacement car. I am always thinking v8 and had been toying with the idea of putting the little garrett T3 I pulled from my Grand National on for kicks. The oil pump is no issue cause they are cheap and a simple hookup and the lack of need for an intercooler makes it easier in my eyes and a lot cheaper overall.

The power of a v8 in comparison will not show the mass increase in power as you may feel in a 4cyl motor having 300lbs of torque already the kick from the turbo will only need to produce 4-6lbs of boost unlike the smaller engine that will want more. so the "lag" will actually help the car be more efficient by not creating too much boost too quickly. Boost requires more fuel it will also reduce the amount of vacum in the system under standard driving conditions adding to fuel economy it may not cause mass performance gains because the turbo is small and designed for a v6 but it will increase the cars overall efficiencey.

So I was looking at it from another set of eyes than most. All of your points are make a great argument for your point of view.

On another note I never liked the turbo Mess under the hood. Cover a turbo all you want they are crazy hot wrapped and shielded my 85 National was a nightmare to work with poor design much better in 86 and 87 especially when the exhaust housing was made smaller it helped the turbo spool much faster this is the reason I replaced my 85 turbo with a 86 model the lower end power due to smaller exhaust housing. very noticeable.

Didn't mean to hijack thread here I enjoy the comments and just went with it.

[redpoint5]

Originally Posted by Old Tele man

...the direct injection both cools the cylinder and allows it to ingest 100% air--rather than the typical less dense A/F-mixture--during the intake stroke. This permits the use of higher CR because the fuel is NOT present during the compression portion of the intake stroke, and is only present at the instant combustion is appropriate to occur (assuming properly 'timed' injection/ignition calculations).

Wouldn't the direct injection eliminate pre-detonation? What is the limiting factor on CR if the fuel is directly injected? Can't we just go 20/1 and run the gas engine like a heat engine with no spark plugs?

[ShadeTreeMech]

Originally Posted by redpoint5

Wouldn't the direct injection eliminate pre-detonation? What is the limiting factor on CR if the fuel is directly injected? Can't we just go 20/1 and run the gas engine like a heat engine with no spark plugs?

So you HAVE heard of the diesotto engine!

[EdKiefer]

Originally Posted by NHRABill

Thanks for all of the comments regarding the rear turbo. My point of view was not stated as I made my comments thinking about myself like always lol.

and as Ed K mentioned the noticeable difference will be much more pronounced in a small displacement car. I am always thinking v8 and had been toying with the idea of putting the little garrett T3 I pulled from my Grand National on for kicks. The oil pump is no issue cause they are cheap and a simple hookup and the lack of need for an intercooler makes it easier in my eyes and a lot cheaper overall.

The power of a v8 in comparison will not show the mass increase in power as you may feel in a 4cyl motor having 300lbs of torque already the kick from the turbo will only need to produce 4-6lbs of boost unlike the smaller engine that will want more. so the "lag" will actually help the car be more efficient by not creating too much boost too quickly. Boost requires more fuel it will also reduce the amount of vacum in the system under standard driving conditions adding to fuel economy it may not cause mass performance gains because the turbo is small and designed for a v6 but it will increase the cars overall efficiencey.

So I was looking at it from another set of eyes than most. All of your points are make a great argument for your point of view.

On another note I never liked the turbo Mess under the hood. Cover a turbo all you want they are crazy hot wrapped and shielded my 85 National was a nightmare to work with poor design much better in 86 and 87 especially when the exhaust housing was made smaller it helped the turbo spool much faster this is the reason I replaced my 85 turbo with a 86 model the lower end power due to smaller exhaust housing. very noticeable.

Didn't mean to hijack thread here I enjoy the comments and just went with it.

For V8, like 300-350ci you would need bigger than T3 , T4 works . The T3 I think would cause to much back pressure with its smaller housing , even if you got large ones .
twin T3 would work nice for 350+ but for eco boost type you might get away with slight smaller twin setup .

So you had 85 GN , that was one with turbo in back and no intercooler . If memory good the 86 was with intercooler in front of fan /pulleys and that one had ceramic intake blade , 14-15lb too .

[NHRABill]

Originally Posted by EdKiefer

For V8, like 300-350ci you would need bigger than T3 , T4 works . The T3 I think would cause to much back pressure with its smaller housing , even if you got large ones .
twin T3 would work nice for 350+ but for eco boost type you might get away with slight smaller twin setup .

So you had 85 GN , that was one with turbo in back and no intercooler . If memory good the 86 was with intercooler in front of fan /pulleys and that one had ceramic intake blade , 14-15lb too .

I Had an 85 GN I sold it about a year or so ago. I looked at my insurance Bill and saw 3 cars too many so had to make a few sacrifices.

You are correct the 84-85 both had the turbo on top of the motor passenger side and no intercooler. I replaced my turbo with only 60,000 miles on it for the 86 model that had a smaller exhaust housing. In doing so I had to clock the 86 turbo 40% around to make it fit the proper orientation of the 85'pipes. The GN was a cool car I always wanted but a pain to work on very innovative for its time in making power but a true knuckle buster. I sold that and 78 chevy straight six 3 on the tree I restored and a 91 3.1L Lumina that I couldn't kill no matter what I did to it.

doing the turbo add to the tahoe is a fairytale at this point. I have little intrest in messing with the truck. Other than some small ecomods to improve mpg's the Tahoe has almost 204,000 miles and its all stock just general maintenence since I owned it. besides I just custom bent the exhaust for that truck and fully welded it a month ago.

The reason I am here is to hear great feedback that you all have when I have one of my oddball ideas. Most peopel tell me I am nuts you guys encourage and refine the idea to be more of a reality. I have a few projects in the way of my goal of an electric build. I need to learn first hand about all that I am reading here, But before any of that can happen I have to swap a tranny for a friends car, tile a few bathrooms, and finish converting my drag car from methanol back to gas this winter. I hope to be working on something this comming spring maybe pickup a frame and build a forklift powered 32 ford or maybe even a cobra that would be something. untill then I am going to keep my ideas quiet I need to reach the level of confidence and am in more of a position to act rather than talk.

[some_other_dave]

Originally Posted by NHRABill

... but 13:1 compression ? i would hate to own that car... 87 octane will not cut it that boy will need 92 octane and even that is almost not enough for it.

Blanket statements like that are quite dangerous. I would not be surprised if we see an engine in the near future that can run 13:1 on 87 octane gasoline. The advances in engine design and (especially!) engine management are helping automakers run higher compression with the same fuel. The aforementioned 14:1 gasoline car will probably only need 91 octane, so it is likely that a 13:1 using the same technology would only require 87.

-soD

[redpoint5]

Originally Posted by some_other_dave

Blanket statements like that are quite dangerous. I would not be surprised if we see an engine in the near future that can run 13:1 on 87 octane gasoline. The advances in engine design and (especially!) engine management are helping automakers run higher compression with the same fuel. The aforementioned 14:1 gasoline car will probably only need 91 octane, so it is likely that a 13:1 using the same technology would only require 87.

-soD

My F4i motorcycle has a 12:1 CR and the recommended fuel is 87 octane. I can work that machine at 14,000 rpm all day long with no problems or performance hits. Then again, the motor is only 600cc.

[gone-ot]

Originally Posted by redpoint5

Wouldn't the direct injection eliminate pre-detonation? What is the limiting factor on CR if the fuel is directly injected? Can't we just go 20/1 and run the gas engine like a heat engine with no spark plugs?

...Google "HCCI engine" and see what Ford (and others) are already doing in this area, ie: gasoline-fueled diesel-like engine. From WIKI:

==================================================
As of August 2007 there were no HCCI engines being produced in commercial scale. However several car manufacturers have fully functioning HCCI prototypes:

• General Motors has demonstrated Opel Vectra and Saturn Aura with modified HCCI engines.
• Mercedes-Benz has developed a prototype engine called DiesOtto, with controlled auto ignition. It was displayed in its F 700 concept car at the 2007 Frankfurt Auto Show.
• Volkswagen are developing two types of engine for HCCI operation. The first, called Combined Combustion System or CCS, is based on the VW Group 2.0-litre diesel engine but uses homogenous intake charge rather than traditional diesel injection. It requires the use of synthetic fuel to achieve maximum benefit. The second is called Gasoline Compression Ignition or GCI; it uses HCCI when cruising and spark ignition when accelerating. Both engines have been demonstrated in Touran prototypes, and the company expects them to be ready for production in about 2015.
• In May 2008, General Motors gave Auto Express access to a Vauxhall Insignia prototype fitted with a 2.2-litre HCCI engine, which will be offered alongside their ecoFLEX range of small-capacity, turbocharged petrol and diesel engines when the car goes into production. Official figures are not yet available, but fuel economy is expected to be in the region of 43mpg with carbon dioxide emissions of about 150 grams per kilometre, improving on the 37mpg and 180g/km produced by the current 2.2-litre petrol engine. The new engine operates in HCCI mode at low speeds or when cruising, switching to conventional spark-ignition when the throttle is opened.
• In October 2005, the Wall Street Journal reported that Honda was developing an HCCI engine as part of an effort to produce a next generation hybrid car.
• Oxy-Gen Combustion a UK based Clean Technology company has produced a full load HCCI concept engine with the aid of Michelin and Shell.
==================================================

...gasoline, by itself, tends to be too inconsistent about ignition, unlike diesel fuel, but they're all working on it because the Diesel cycle is much more efficient than the normal gasoline Otto cycle.