Thread: Supercharge a 4BD1?

Originally Posted by Dougal

There was a thread on another forum where someone did supercharge a td42, it was quite recent but I can't find it. Google searches only pull up sites I don't visit.
At the end when he got all the bugs worked out, the supercharger was swapped for a turbo, but no good explanation given.

the explanation given was

a lot of work for little gain, ( fitting drive etc). starting off with not the ideal unit and a good $$$ offer from some one in Queensland. Additionally the vehicle needed other work. i don’t think the turboing has started yet.

Originally Posted by Dougal

I run a backpressure gauge on my Isuzu whenever I change the turbo setup and the results of this prove very interesting.

At 100km/h cruise with EGT's around 430C backpressure is ~1.5 times boost. 12-13psi backpressure for 8-9psi boost.
At the same rpm (2000 near enough) and full load the backpressure drops as EGT's rise. Above 600C I have slightly more boost than backpressure, the hotter the EGT's get, the lower the backpressure.

In these high load conditions, the turbo is essentially working off just the waste-heat, the backpressure it also needs to work is compensated for completely by the boost it provides. This mode of operation a supercharger just can't match.

Most of the time comments about turbocharger efficiency are talking about the compressors efficiency. Superchargers used to be a lot less efficient so the air charge was a lot hotter, but new superchargers have made big gains there.

Dougal I have read and reread your post. And as you said "results of this prove very interesting" if your results are correct then I think you have discovered perpetual motion.
To have less pressure on the hot side than the cold side (indicated) would sagest that you pressure gage set up and or pressure gage is fubar.

Heat is the mechanism that creates pressure; heat alone can not move anything.

Originally Posted by Dougal

There was a thread on another forum where someone did supercharge a td42, it was quite recent but I can't find it. Google searches only pull up sites I don't visit.
At the end when he got all the bugs worked out, the supercharger was swapped for a turbo, but no good explanation given.

i started a thread on here, but buy that time we had it on and in tuning,

we got up to 9ish psi max and yes it did go better, it took awile to set up right as it come off a petrol 3.6 ecotec, so we had to make vacum lines and all sorts to run the by pass valves, in the end it did work, and it was good off rd, never towed with it,

but as in out right perfomance, he got me off the line as you would with out right displacement and a SC( and a pootrol drive line) , but after 2nd gear that it was all by by, and i dont think my td5 has huge power, just 21psi and big chip and straight exhaust, plus its moving some fat 33s

so depends what you want out of it,

Originally Posted by 85 county

Dougal I have read and reread your post. And as you said "results of this prove very interesting" if your results are correct then I think you have discovered perpetual motion.
To have less pressure on the hot side than the cold side (indicated) would sagest that you pressure gage set up and or pressure gage is fubar.

Heat is the mechanism that creates pressure; heat alone can not move anything.

Not at all. Look at the total energy present in the exhaust stream (heat, pressure and velocity) and the proportion of that which needs extracted to provide the same pressure through a 65-75% efficient compressor.

If you get those maths right you'll see that even with a relatively poor performing turbine and compressor (so total efficiency 0.65*0.65= 42%) you can still get boost above backpressure at the best operating points.
With more efficient turbines and compressors (i.e. modern turbos) it's possible to reach boost above backpressure over a decent chunk of the operating range.

Do the maths, it's not only possible but it happens every day in most turbocharged vehicles.

Heat moves stuff every-day. From the wind to the pistons in your engines. It's all moved by heat.

Originally Posted by Dougal

Not at all. Look at the total energy present in the exhaust stream (heat, pressure and velocity) and the proportion of that which needs extracted to provide the same pressure through a 65-75% efficient compressor.

If you get those maths right you'll see that even with a relatively poor performing turbine and compressor (so total efficiency 0.65*0.65= 42%) you can still get boost above backpressure at the best operating points.
With more efficient turbines and compressors (i.e. modern turbos) it's possible to reach boost above backpressure over a decent chunk of the operating range.

Do the maths, it's not only possible but it happens every day in most turbocharged vehicles.

Heat moves stuff every-day. From the wind to the pistons in your engines. It's all moved by heat.

Heat is energy NOT matter
there is no more KG of gasses ( plus fuel)coming out of any motor than what goes in. all you have shown is that you have energy what happened to all the matter

Originally Posted by 85 county

Heat is energy NOT matter

Of course and nothing moves by itself, it requires energy.

Originally Posted by 85 county

there is no more KG of gasses ( plus fuel)coming out of any motor than what goes in. all you have shown is that you have energy what happened to all the matter

I don't understand the intent of your statement. Mass flow is not related to anything discussed so far.

Originally Posted by Dougal

Of course and nothing moves by itself, it requires energy.



I don't understand the intent of your statement. Mass flow is not related to anything discussed so far.

Mass is every thing. no matter = vacuum. Heat in a vacuum has nothing to effect. While you are not describing a complete vacuum. natural laws still apply.

Originally Posted by 85 county

Mass is every thing. no matter = vacuum. Heat in a vacuum has nothing to effect. While you are not describing a complete vacuum. natural laws still apply.

There is no vacuum in a diesel engine, so we're pretty safe there.
All physical laws still apply in a vacuum, but I still see no relevance in your statements.