isuzu induction system

**c.h.i.e.f** · 15th January 2012, 01:56 PM

recently i have been working on my isuzu county again and have been thinking of a few things that i thought i would discuss on here.
as we already know a nice sized exhaust system on a motor helps it expel the gases quicker and this is a common modification for a turboed motor but what about on the inlet side of things??
as previous studies and testing has been done on here on what filters are best suited (from memory isuzurover done a in depth study?) for the motor and the best filter turned out to be the factory donaldson filter arrangement.

the inlet and outlet to the factory filter housing is 3"

on the safari snorkel site it says that they have designed there snorkels to exceed the airflow requirements of the 2.5tdi motors but what i was wondering is, is it enough to accommodate the requirements for a 4bd1T motor that is above factory power levels?

would it be sufficient enough having 3" everywhere? or would a 3.5 or 4" snorkel made out of stainless be more benefitial?

also the size of the piping between outlet of the compressor housing to the motor what is the optimal size for flow but not effecting pressure?

then again i could be looking into it to much and it isnt that much of a deal

what is everyones opinions/findings?

Rangier Rover · 15th January 2012, 02:22 PM

The 4BD1 is no fire breathing rocket and never will be.

They dont rev!

Very small gains if any in this area in my experience. In theory big gains but in real life

I have gone back to the OEM filtration with the safety filter as expect my 4BD1T will probably see me out with out a major rebuild. Good filtration plays a big part here.

Long live the mighty 4DB1

On the intake. I have a 3" stainless snorkel. Has no effects on power economy as to speak other than cool denser air on hot days. Never bothered to check if there is any real pressure drop. Possibly would have.

On exhaust side, I have a full 3" mandrel inc the dump. Also very small gains if any overall. Spools quicker and a bit less heat.

**Blknight.aus** · 15th January 2012, 02:25 PM

as a very general rule to keep the flow rate the same through a mandrel bend you add 1/2 an inch to the diameter, a press bend nearly double.

**c.h.i.e.f** · 15th January 2012, 02:58 PM

i understand that they dont rev and the airflow wouldnt be anywhere near that of a petrol but being a turboed motor the turbo does the sucking and i have seen my duckting moving quite a bit once motor is reved thats all.

would you have a photo of your snorkel rangier rover? and out of intrest does it change the noise of your engine do you think?

thanks blknight i have been wondering that for awhile now...

**c.h.i.e.f** · 15th January 2012, 03:00 PM

rangier rover you wouldnt have any photos of where your exhaust runs would you?

Rangier Rover · 15th January 2012, 08:48 PM

I'll dig them up soon, few pics are floating around AULRO now.

I had to run the 3" exhaust under the starter motor and in line of a spanner throw of the clutch slave (Can still service it) so could wing it over the main X member. Not ideal but has two flange joints so easy to remove if need be . Best part it, the exhaust is well out of harms way

.

**c.h.i.e.f** · 15th January 2012, 09:19 PM

cheers
yeah i have to say the original position of an isuzu powered landrover leaves alot to be desired .
i went to a 3" exhaust and positioned it as close to the chassis as possible in the factory route but once 33's were put on it was touching when i turn and i shal not even mention what 35's do to it

i then made a different dump pipe that goes in front of the starter motor but it seems tight due to the winged sump so thats why im interested in seeing your setup!
i thought about swaping the sump for a non winged one to gain room.

**Bush65** · 16th January 2012, 01:42 PM

The pressure drop across the inlet filter and snorkel system can amount to a small amount of psi. The effect is to reduce that amount from the turbo boost - the other way of looking at this is that you increase boost by the same to cancel the performance loss.

Similarly on the exhaust side, reducing pressure drop after the turbo increases the expansion across the turbine , thus more torque from turbine or lower drive pressure for same expansion ratio.

**c.h.i.e.f** · 16th January 2012, 02:51 PM

Mmm interesting....concentrating on the air temp and pressure getting into the chambers would be the more important thing to play with then.
out of most compressors the outlet is around 2" give or take a tad depending on turbo size but what is preffered piping size from there on ? Say if you was to use a 3" pipe would that be to much volume to fill compared to 2.5" or is it not that crutial ?

**JDNSW** · 16th January 2012, 04:52 PM

Just a comment on air volumes. Comparing a diesel to a petrol, remember that with a petrol engine, most of the time the major restriction to airflow is the throttle, so other constraints (air cleaner, exhaust etc) really only come into play at full throttle. This is not the case with a diesel, where the airflow depends only on the rpm (and boost if turboed), and the amount of air is mostly considerably more than is required to burn the fuel, so airflow is a lot higher on a diesel than a petrol engine of the same power.

And in comparing the airflow of a 4BD1 with say a Tdi or Td5, a rough equivalence would be that the same airflow is required to produce the same power (will vary a bit, but not much). This suggests that a snorkel designed for a Tdi or Td5 will have plenty of capacity for a 4BD1 and probably a 4BD1T.

John

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