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Why an Intake May Hurt Performance
Posted: Thu Dec 05, 2013 11:38 pm
by SamirD
I was just reading the 1000 page service manual available here (well not every page), and came across some very interesting technology that may negate any gains by having a traditional performance 'intake' on the car.
The IMT system varies the effective intake pipe length by opening and closing the IMT valve in order to improve air volumetric efficiency.
As the intake valve in the cylinder head is opened and closed repeatedly, intake air pulsation occurs. If the intake valve is opened when air pressure is momentarily at the maximum level, the intake air volumetric efficiency increases. This momentary maximum air pressure depends on the effective intake pipe length.
When IMT valve is totally closed [A]:
The effective intake pipe length is longer. Engine torque in the high engine speed range drops, while it improves in the middle range.
When IMT valve is fully open :
The effective intake pipe length is shorter. Engine torque in the high engine speed range improves, while it drops in the middle engine speed range.
IMT system utilizes this characteristic of engine. IMT valve is closed in middle engine speed range, and opened in high engine speed range.
In this way, engine torque is improved in whole engine speed range.
Page 611 if anyone wants to look at the diagrams including what looks to be a dyno graph.
Re: Why an Intake May Hurt Performance
Posted: Fri Dec 06, 2013 4:47 am
by murcod
It's a split length inlet manifold. Longer inlet tract gives better torque at low revs, short tract gives higher power at high revs. They work extremely well- I had a vehicle back in 1995 with a similar system and had it dynoed with the system locked in both positions and in the the normal ECU controlled mode. The ECU switched the inlet over at exactly the correct revs for peak power and torque across the whole rev range. On the road, you could really notice the difference with inlet being locked manually in either position.
Re: Why an Intake May Hurt Performance
Posted: Fri Dec 06, 2013 7:14 am
by bootymac
It's best not to mess with most modern intakes nowadays. The engineers usually developed them to be as efficient as possible. Usually.
Re: Why an Intake May Hurt Performance
Posted: Fri Dec 06, 2013 5:34 pm
by LPSISRL
The SX4 J20b engine had the same setup. It was in the owner's manual. I wasnt' aware the Kizahi used the same system.
Re: Why an Intake May Hurt Performance
Posted: Sat Dec 07, 2013 2:55 am
by Speed_Racer
My '86 MR2 had a variable intake system as well (T-VIS). You could actually hear the engine note change when it made its switch. Though with the engine a foot or two behind your ears... you could hear everything going on back there haha.
The TVIS system was located "behind" the air filter, so you could swap filters without affecting TVIS, aside from how the airflow would change w/ different style filters.
Re: Why an Intake May Hurt Performance
Posted: Sat Dec 07, 2013 5:06 am
by SamirD
Very cool to know this technology has been used in other Suzuki's and other brands!
I remember AEM making a 'version 2' type of intake that used a chamber that optimized intake flow at two different RPMs. Unless you've got a flowbench and a dyno, it's really hard to make power on the newer cars out there when they're done right.
