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nickh90



Member Since: 19 Oct 2009
Location: Nr Horsham
Posts: 196

England 1989 Defender 90 V8 Petrol SW Auto Java Black
Engine breathing thoughts.. 5.7V8 through a mantec snorkel?
Hi all,

Getting a few things sorted over the coming weeks.. mostly cosmetic and basic mechanics.. however, one thing niggling me..
I see many a forced induction 2.5 diesel engine requiring 2 snorkels to get the required air in.. however on my LS1 powered 90 (350hp)it is currently routed through a cylinder air box then through a 3" pipe into a mantec snorkel..

Will this not strangle such a large capacity engine when pushing on or does the fact its NA mean it doesnt require such an immediate intake of air?

Thoughts appreciated..

Cheers
Nick
Post #173114 4th Oct 2012 7:40am
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JeremyJ



Member Since: 16 Nov 2011
Location: Aylesbury
Posts: 1758

United Kingdom 
My knowledge of air flows etc in RAIs is limited, I personally would have a look on LR4x4 and pick their brains as well.

My 4.2 felt slightly strangled running a Mantec to such a degree I took it off an donated it elsewhere.

How have you got the filter connected to it? The chevy lump I've got in an old Classic (only a little 5.0 one) is running a Holley that looks a pain to connect to a RAI!
Post #173117 4th Oct 2012 7:56am
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me@td5.org



Member Since: 16 Jan 2011
Location: Warwick
Posts: 856

2000 Defender 90 Td5 HT Epsom Green
Jeremy wrote:
My knowledge of air flows etc in RAIs is limited, I personally would have a look on LR4x4 and pick their brains as well.

My 4.2 felt slightly strangled running a Mantec to such a degree I took it off an donated it elsewhere.

How have you got the filter connected to it? The chevy lump I've got in an old Classic (only a little 5.0 one) is running a Holley that looks a pain to connect to a RAI!


Air intake restriction is more of an issue on NA cars than turbos, as having a positive pressure on the air box in an NA car can produce some tiny benefits.

Easier to test your car with and without the snorkel than it is to work out what effect the restriction will have if any.
Post #173119 4th Oct 2012 8:01am
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davew



Member Since: 02 Jan 2012
Location: North Yorkshire
Posts: 888

England 1990 Defender 90 V8 Petrol PU Auto Rioja Red
It may have some effect but the throttle butterfly is only 3 inches in diameter too even though the throttle body is 4 inch diameter. Rightly or wrongly, I work on the principle that as long as the pipework is as big as the throttle butterfly then that is always going to be the most restrictive part other then the air filter.

I run mine on a MegaSquirt ECU and have done straight comparisons with and without the snorkel (my snorkel is 3 inch diameter stainless pipe with a 4 inch diameter K&N filter on top of it) while logging the engine data. There was no discernible difference in MAP readings as far as I could see even at WOT. You could do something similar even if you are using the factory ECU by hooking a voltmeter up to the MAP sensor and getting someone to monitor it at WOT. It's easier to do this using logging though as you don't need to sustain WOT for very long. It doesn't take very long before you're either speeding or coming up to a car/bend !

Your reference point, the ideal MAP at WOT is the same as when the engine isn't running - atmospheric pressure. The closer the MAP is to that when at WOT the better your intake setup and that includes your air filter. http://www.yorkshireoffroadclub.net/
Post #173127 4th Oct 2012 8:27am
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