Long intake VS. Short intake

[autonut]

Does anyone know techically what the advantages are of a long intake over a shorter one with a smaller plenum?

 

[GVR4592]

Are you talking about intake manifold runners or an air intake pipe?

 

[VanIsleDSM]

here, check this out for intake runners..

http://auto.howstuffworks.com/question517.htm

 

[1997GST]

if this is in reference to an air intake (which I would assume so since it's a common/easy upgrade) than consider this.

A longer intake will usually place itself in a lower spot on a car. Basic physics suggest that the air on the ground is cooler in compared to the air higher (thus cold air intake is used). Not only are you getting fresh cool air from the bottom of the street, you're also not sucking up the hot ambient air that is circulating around the engine compartment.

Cooler air is densor, densor air will let the IAT sensor allow for a better timing curve and more fuel (this is where all those ebay "chips" come in that trick the iacv so the computer throws advanced timing end result is a little bit more horsepower).

The short ram intakes have the advantage of a little bit less turbulance in the air flow (stock boxes are baffled for noise reduction, but create turbulance). The main advantage of a short ram is it's pretty close to impossible to hydrolock your motor.

The long cold air intakes can easily suck up water if going thru a big puddle, that's bad. There are water bypasses but they get costly.

I run short ram intakes on my cars. It's cheaper and the horsepower loss is minimal in my opinion.

Hope that clears it up for you

 

[GVR4592]

Cooler air is densor, densor air will let the IAT sensor allow for a better timing curve and more fuel (this is where all those ebay "chips" come in that trick the iacv so the computer throws advanced timing end result is a little bit more horsepower).

The ebay chips don't trick the IACV(idle air control valve). Some ecu's don't have an air temp correction for ignition timing, they all have one for fueling though.

 

[1997GST]

yes, the IACV reads collant temps and is controlled by the ECU. I know that the cheap $1 worth of radioshack parts that kids spend $20 on via ebay are mainly wired for the IATs (intake air temp) sensors.

Coolant temp sensors are a bit different, those only tell the computer that the car is warmed up and is another link in the chain for the ECU going into closed loop mode. I remember older turbo kits for hondas (I think it was a name brand) that tricked the coolant temp sensor so the car would run rich to compensate for the added boost.

 

[GVR4592]

yes, the IACV reads collant temps and is controlled by the ECU. I know that the cheap $1 worth of radioshack parts that kids spend $20 on via ebay are mainly wired for the IATs (intake air temp) sensors.

Coolant temp sensors are a bit different, those only tell the computer that the car is warmed up and is another link in the chain for the ECU going into closed loop mode. I remember older turbo kits for hondas (I think it was a name brand) that tricked the coolant temp sensor so the car would run rich to compensate for the added boost.

Where did you come with coolant temp sensors? That wasn't even brought up.

The idle air control valve does not read coolant temps. It has nothing to do with coolant, that's the FIAV. Neither of them use any sort of sensor to monitor the temperature of anything.

You make it sound like coolant temp sensors are an ON-OFF switch, they're not.

 

[1997GST]

I'm sorry, I was thinking of the FITV (fast idle thermo valve). But yes, the IACV is ecu controlled.

The coolant temp sensor does have an interaction with the cars cloed loop/open loop operation.

 

[GVR4592]

I'm sorry, I was thinking of the FITV (fast idle thermo valve). But yes, the IACV is ecu controlled.

The coolant temp sensor does have an interaction with the cars cloed loop/open loop operation.

I never said the IAC wasn't computer controlled or that the coolant temp sensor had no interaction with closed loop/open loop. I guess I don't understand what you're trying to say.

 

[1997GST]

the point i was making to him was about air intakes and how they suck up air. Colder air coming from just a few inches off the ground is going to be a lot densor than a short ram intake sucking air that is circulating from the engine bay.

I then went off in a sub tangent and started talking about why colder air is better for performance. Dense air can take more fuel and more timing advancement. We then went off a little and talked about coolant sensors and idle controls.

I will admit that you probably know more about DSM cars than me, my area of knowledge rests with hondas and mechanics in general. My sensor terms might slightly vary, and I might not know which sensor a DSM will have in comparison.

 

[autonut]

Let me rephrase my question. I have 2 stock intake assemblies which are the intake tubes and plenum assembly complete. The difference is one has a really large plenum and about 1.5" more tube to reach the head than the other. The other has a smaller plenum and has shorter tubes.

I am currently using the longer one (it was from a newer, larger car) and I was told that the shorter one may have advantages over the longer.

 

[VanIsleDSM]

the shorter will have more advantages at higher revs, the stock intake mani on our cars has much longer runners than the aftermarket intake manis you can buy.. this is to direct more of the power into the high revs.... with the stock intake runners being long they focus on stacking the intake pulses as the intake valves open at a slower rate, (it takes longer for a pressure wave or pulse to travel back to the plenum once the intake valves shut and then bounce back down the long runner to get to the intake valves for their next opening) *** more geared towards mid-range revs, with the shorter runners of the aftermarket manis these pulses bounce back and forth faster, suited to the more frequent opening and closing of the intake valves at high revs... hope that helps.

*** didn't want to be more confusing but the pulses actually bounce off the plenum off the closed intake valves, and back off the plenum again before hitting the open valves... that link I posted explains it quite well.

 

[autonut]

Thanks alot. Makes sense, and the link was helpful. The 2 intakes I have are the bigger one, from a 97 Hyundai Sonata 2.0 and the smaller is from my stock engine, a 94 Elantra with a 1.8. I have a friend who told me that they were trying hard to get the 1.8 to perform like the 2.0, thus the shorter intake. I do notice a slight 'lag' when stepping on the gas with the longer one, almost like turbo lag, without a turbo. I have the shorter one on my galant, and the response it totally different. Im going to build another 2G DOHC 2.4 for my Elantra, and I want to use as many factory parts as I can, cept for the cams which Im sending to Crower to be regrinds.