Outer Limits 4x4 Board

had a discussion with a mechanic at work, he seems to think that just by adding a larger snorkel you get more power?

Scenario;
4.2 factory turbo diesel, non-intercooled with a 3.5" stainless snorkel, If you were to put a 4" or 5" snorkel onto it would it make more power
A) driving or moving
B) stationary on dyno

His theory is that the air is rammed into the turbo therefore flows more,
My theory is the turbo may spool quicker, but it can only compress and move so much air, no matter how much air is available, it will only use what it can.

What is the go? Does anyody know, with figures to prove it?

So you wanna use forced induction on your forced induction


The turbo is pumping well and truly enough, it would be impossible to force any more up its butt without another turbo to push the air and pressurise it further.


But if ya like the look of twin snorkels then go for it.

Someone on a Suzuki thread did some calculation on what would be required to develop positive pressure with a snorkel.

The calculations looked quite creditable and it basically turned out not to be practical at the sort of speeds we are interested in.

This is assuming however that the air intake system already fitted isn't unduly restrictive, in which case simply fixing whats already there would produce gains.

Another thing to think about is that things stuck on the outside of cars produce drag, 2 snorkels = twice as much drag. The losses through extra drag would need careful consideration, otherwise you could well end up worse off overall.

I'm thinking that if the turbo is drawing air from atmospheric pressure it'll take a little longer and work harder to move the same volume of air as a turbo that has a volume of air pressure feed to it. Does this sound reasonable or correct? (to a degree)

But even if that is the case, it will only be pressurized and "trapped" at the front of the turbo waiting to be pulled through, So surly any sized snorkel would be addiquate enough, provided it was enough for basic engine needs to begin with.
And even then would it make more power just because it can move the air easier?

You will find that the biggest restriction will be the air filter, regardless of how hard the air "blows" against it, it is almost like it is blowing against a solid. (ever stand behind a bit of shade cloth when it is windy, it blocks a supprising amount of the wind, but if you try to suck air through it it acts almost like there is no barrier at all)



I recall reading in oneof the car mags about the WRX's that have the big aftermarket bonnet scoops ... They take more power to drag through the air than what the additional charge cooling capacity gives ..

I realise this, But to keep things simple I am just refering to at the turbo inlet,
Would there be any overall (not boosting sooner) power increases if the air was pressure feed through a snorkel, rather then drawn through from atmospheric pressure?

On a turbo engine, there might be slightly more positive pressure at the turbo inlet when there's no load on the engine.

As soon as you hit the accelerator and put a load on the engine, any positive air pressure before the turbo will be very quickly replaced by vacuum from the turbocharger.

So while a freeflowing snorkle will definately give better driveability, economy and power than a poor flowing snorkel I really doubt it could provide any positive air pressure at the inlet to the turbo.

Opinions?

love_mud wrote:...ever stand behind a bit of shade cloth when it is windy, it blocks a supprising amount of the wind, but if you try to suck air through it it acts almost like there is no barrier at all...

I can just picture how many members have tried this since reading Guy's post.

At the end of the day ANY restriction is going to affect performance, what needs to be weighed up is how much gain you're going to get from the time/money spent and what other sacrifices you'll have to make that could sap the power away elsewhere, eg twin snorkels creating more air flow to the engine but more wind resistance/poor aero dynamics taking power away.

If you can be bothered, dyno your car with the snorkel and no air filter, then without the snorkel/air box/filter (bonnet up) and see what happens. This will take you from one extream to the other.

Does bigger snorkel=bigger power??

I've got a 20" airconditioning duct on the roof of my Mazda 121 and it absolutely hammers

GQ Bear wrote:Does bigger snorkel=bigger power??

I've got a 20" airconditioning duct on the roof of my Mazda 121 and it absolutely hammers

ThAt I want photos of

x2 that would be i funny thing to look at

GQ Bear wrote:Does bigger snorkel=bigger power??

I've got a 20" airconditioning duct on the roof of my Mazda 121 and it absolutely hammers

sweeet! but is it polished??

nah should be painted red with chrome edging to go faster and also for bling factor

It boils down to how restrictive the intake system is relative to the requirement of the engine, I did a tune recently on a TB42 Carby that made about 81 rwkW which is quite respectable, the customer asked the same question as to the benefit of a large snorkel and air box. I removed the carby air box lid and repeted the dyno run and the vehicle improved to 89 rwkW with a noticable improvement from about 3000 rpm. It depends on the air requirements of the vehicle as to the gain but i a stock carby can show a 10% gain then anything making more power would show a larger gain.

Joel

work out the volume of the pipe (a bigger pipe means more volume) then times the amount of atmostshperes (boost) that the turbo provides.
better to work out the full volume of the pipe though rather than just the snorkle.

14.69 PSI = 1 BAR = 1 atmostshpere

Thanks for input guy's, The convosation started because the mechanic at work had the chance to get a factory nissan snorkel for cheap, Instead he is opting for another brand that's $120 or so more, Simply because he thinks it flows better, therefore has more air going through it, therefore makes more power for his engine.
I realise that a good induction system will alway's give you power gains, But surly driving at posted road speeds isn't enough to create positive pressure at the turbo inlet whilst engine is under load or boost, Which is the mechanics argument.
I can understand that the turbo may spool up faster or earlier, but that isn't h/p figures increasing, thats just boost coming on sooner, So the answer is NO, a bigger snorkel alone won't increase your turbo's output potential but may help with ealier boosting?
Sound about right.

That's actually not the answer, the answer is DO NOT take your vehicle to the dreamer/mechanic

hahaha, I work on mine myself, And yes he is a Truck mechanic.... Sad hay?

A larger snorkel can increse the turbos potential it the current snorkel is restrictive, the turbo will have to spin faster if the intake is restricted to generate the same boost, if rotating at a higher speed the turbo outlet temperatures will be higher, much like when you put you hand over a vacuum cleaner, the electric motor speeds up and the suction diminishes, the impeller looses efficiency, I don't believe the snorkel creates any significant boost level however it does allow for a less restricted intake that in turn increases engine efficiency.
I can do a dyno run and log manifold pressure on a N/A engine, it will be for example 100 kpa up to 3000 rpm and then diminishes to 97 kpa by 6000, the engine is now below peak cylinder fill as it is generating vacuum due to a restriction in the intake tract, this could include the carby itself of EFI throttle body, air filter, dust extractors and snorkel.

Joel

Thank you

I believe the question should be:
"Does a large snorkle strangle an engine less?"

The answer is. Yes.

Thanks captin obvious,
perhaps the question should have been, Does a turbo produce more power under a pressurized inlet?

MY answer is if the snokle pressurises the air to 1 psi and the turbo is set on 10 psi then 11 psi of power(which would make a patrol about 81 kwatts at the alternator)

But if the turbo is set at 10 psi, How does it move 11psi ????

It's about moving a volume of air in the most effective, effiect way to produce more power.

mattstar wrote:Thanks captin obvious,
perhaps the question should have been, Does a turbo produce more power under a pressurized inlet?

All your turbo compressor knows is the pressure ratio it's working at and the flow.
The pressure ratio is the absolute pressure it's blow air out at divided by the absolutel pressure it's sucking air from.

If a turbo is wastegated to a set boost pressure (as most are) then it'll only be able to provide that amount of boost. But the difference is how hard it has to work to provide that boost.
If the turbo compressor has to work harder due to inlet restrictions then you need more exhaust pressure and temperature to drive the turbine harder. Which does cost power.

Short story.
On a diesel, the most free flowing intake is always the best.
Snorkels are a big airflow restriction and ram is is useless at legal road speeds.

yeah okay, so were agreed that a pressurized airbox (turbo inlet) might produce early spool, quicker spool up , as the turbo might not have to work as hard. But it will still only produce the same power.
I understand that the speeds needed for the snorkel to achieve positive airbox pressure are NEVER going to happen.
Thank you all, any info greatfully appreciated.

mattstar wrote:yeah okay, so were agreed that a pressurized airbox (turbo inlet) might produce early spool, quicker spool up , as the turbo might not have to work as hard. But it will still only produce the same power.
I understand that the speeds needed for the snorkel to achieve positive airbox pressure are NEVER going to happen.
Thank you all, any info greatfully appreciated.

You'll get a tiny power improvement as the turbo doesn't need to work so hard. But it's going to be below the margin of error on your average dyno. Especially the oh-so-accurate butt dyno.

The convosation started because the mechanic at work had the chance to get a factory nissan snorkel for cheap, Instead he is opting for another brand that's $120 or so more, Simply because he thinks it flows better, therefore has more air going through it, therefore makes more power for his engine.

So we're only comparing 2 standard style snorkels (safari vs airtek - airflow or whatever!?) and its only that he 'thinks' that one flows better....
So its not like we're comparing a 4 inch snorkel with the standard style one either. If the motor is fairly standard i'd say it'd make sfa difference.
And yea if there was less vacuum at the turbos intake then it would not have to work as hard to make the required boost.

Similar to a guy at work who has a 60 series with a 350 chev he put a snorkle on just because he thought it would help economy and power due to ram air! - obviously hasn't considered all the extra bends and pipe work(designed for 6 cylinder) that 5.7 litres now has to suck through!!

Patroler,
yeah thats pretty much it, he tells me that less bends etc, means the air is rammed into the turbo so makes more power. (whilst I realise that more air, less bends does mean more power, I also think that the "ram" affect is b/s)
I said that if the induction system (snorkel or not) flowed the same volume of air, the only difference to be gained would be through the filter and a positive turbo inlet pressure, by making the turbo work less, Having said that I then thought that by driving legal speeds and off-road 4x4 speeds there is no way you could "ram" enough air in to create constant positive inlet pressure, So the $120 odd extra bucks chasing 1-2 hp that might only be helpfull at highway speeds is wasted, But on the other hand, If the engine has to draw air through a snorkel under load at low revs, It probably would benifit from a free flowing snorkel.
So would there be that much difference between aftermarket snorkels? I don't think $120 dollars worth???

For those that are bored:
http://www.vararam.com/ramairinaroadcar.html

Lots of numbers from Ram air tests