Lets talk intake setup

[IIv SHaDoW vII]

I did the searching and I cant seem to find any good info on the best intake to get for the 420a. I noticed some went with OBX, but I heard that there are some fitament issues with it. Money is not an issue so if anyone has a good setup in mind please feel free to tell me. Id like to replace everything so Intake Manifold, Throttle Body, fuel injectors and whatever else I would need or should replace while its all disassembled.
Im not tryin to get flamed for asking such a vague question but I searched for an hour only to learn that the OBX IM isnt worth the fabrication.

 

[teamo2t]

I highly recommend AEM. I have the older cold air intake, I hear the V2 is a great improvement. AEM all the way!

 

[4UH8ERS]

I did the searching and I cant seem to find any good info on the best intake to get for the 420a. I noticed some went with OBX, but I heard that there are some fitament issues with it. Money is not an issue so if anyone has a good setup in mind please feel free to tell me. Id like to replace everything so Intake Manifold, Throttle Body, fuel injectors and whatever else I would need or should replace while its all disassembled.
Im not tryin to get flamed for asking such a vague question but I searched for an hour only to learn that the OBX IM isnt worth the fabrication.

Now these answers are based on the fact that I'm assuming you have a non-turbo eclipse with the 420a motor.

Manifold.

OEM, get it port matched to a MP 60mm throttle body. Have the runners ported, extrude honed, and gasket matched. I also recommend having the injector humps knife edged. You will also need to port the intake side of the head to match the manifold for best results.

Throttle Body.

Modern performance 60mm TB

injectors

no real need to upgrade over stockers without forced induction or Msns

intake.

A pipe is a pipe my friend. The filter is whats important. (K&N, Injen, and AEM all have nice filters) Go short ram with some sort of heat shield. You can route air from the from bumper ect towards the filter placement if you want to be extreme about it, but not much as far as hp gains will be found here.

 

[IIv SHaDoW vII]

Thanks guys, and I have a 99GST and a 98GS. I have decided to modify the GS for now since my GST is bone stock and I dont want to change anything until my warranty runs out. I purchased my GST from the dealership 2 years ago and they gave me a 4 year warranty on it so if I start modding that my warranty is void. As far as the GS goes, I see potential ^^

 

[BigRand]

Well just so you know your going to see a lot more bang for your buck on the GST, however there is still a lot of fun to be had by modding a GS with non turbo mods...

K&N air filter + Short ram intake pipe + modernperformance 60mm Throttle Body + port matched stock intake manifold (you can knife edge the injectors if you want) + (symtechlab's intake manifold spacer: talk to paul on this) + portmatched/port polished head w/ 3 or 5 angle valve grind + 4-2-1 header (not obx, more like pacesetter or tsudo, or megan racing) + highflow cat/test pipe (2.5") + 2.5" Exhaust (Tsudo, P.I.T.)

If I had to do an non turbo all over again, that would be my goal (plus MSnS)

 

[4UH8ERS]

(symtechlab's intake manifold spacer: talk to paul on this)

are you talking phenolic spacer? if so, I though this was aimed as a much more beneficial mod for those running forced induction to Keeps intake manifold temps down.

 

[VelocitàPaola]

They can be beneficial to both N/T and forced induction setups. It's all about the coolest intake temperatures... turbo or not. A spacer makes more sense than running an intercooler while you're N/T.

 

[IIv SHaDoW vII]

Yea, I know I should mod the GST. Ive went back and forth debating on if I should just say screw it and void the warranty.. but then I came across this GS about 4 months ago. Got online knowing that 4g63 forums were common. Then I found you guys ^^, the 420a specialists. So I think Im going to build up this car, and when the time comes, I'll mod the GST.. the best of both worlds right? Ive also heard great things about the 420a holding up to the power of a turbo.

 

[Locke]

are you talking phenolic spacer? if so, I though this was aimed as a much more beneficial mod for those running forced induction to Keeps intake manifold temps down.

They can be beneficial to both N/T and forced induction setups. It's all about the coolest intake temperatures... turbo or not. A spacer makes more sense than running an intercooler while you're N/T.

The aluminum IM will act like a giant heat sink hanging off the side of the head. Heat will transfer from the head to the lower IM, to the upper IM. Since the longer (time) a fluid is subjected to a heat source, the more heat it will soak up. The phenolic spacer is used to reduce the temps of the upper IM, shortening the amount of time the air is exposed to heat.

It is more beneficial on a boosted engine, as more power equals more generated heat. You would get some benefit on a NA engine, but I personally don't suspect it would be a very notable gain.

An intercooler on a NA motor has absolutely zero benefits. A heat exchanger can only cool (or warm) to, at best, the temperature of the ambient air around it. The vehicle is already pulling in air at ambient temperatures, an intercooler cannot cool it any more than that. A phenolic spacer is MUCH better than an intercooler on a NA motor.

 

[DSMMER06]

i have an obx intake and didnt have to mod. a thing besides making the sensor ports larger and tapping the map sensor...i do have one problems though. when i tapped my map sensor i did it to low and had to cut on the cruise control box. i forgot to buy a missing link also cause im turboed and now i might have to cut on it again. Does anyone know if i go with the electronic one if it would extend the map sensor out or do you just have to splice the wires??

 

[Jonny]

i had a 96 with the 420a id go with Venom look it up

 

[Shadow98]

i had a 96 with the 420a id go with Venom look it up

OBX is basicly a knock-off of the Venom IM

 

[VelocitàPaola]

It is more beneficial on a boosted engine, as more power equals more generated heat. You would get some benefit on a NA engine, but I personally don't suspect it would be a very notable gain.

You forgot about Helmholtz resonance. Thick spacers increase the length of the intake manifold runners, thereby lowering the point of Helmholtz resonance. During resonance VE is pushed beyond 100% creating a power boost to help N/A cars along their way in the lower power band -- where much of their modifications haven't come alive yet.

Corbin always thought the spacers would help N/As in regular stop-and-go traffic as well, because while idling at a light, the intake air has a lot of time to sit around and soak up heat from the plenum. The spacer would eliminate that effect and give the car a little more pep while driving around on hot summer days.

 

[Locke]

You forgot about Helmholtz resonance. Thick spacers increase the length of the intake manifold runners, thereby lowering the point of Helmholtz resonance. During resonance VE is pushed beyond 100% creating a power boost to help N/A cars along their way in the lower power band -- where much of their modifications haven't come alive yet.

I agree, but we can assume (i try not to use that word much) the effects of Helmholtz resonance has been accounted for and incorporated into the design of the factory manifold. Likely tuned to become effective during middle to upper RPM driving to increase total output of the engine, and create a better number to advertise with. Adding a 0.375" or 0.5" spacer will lower the point of Helmholtz resonance to the slight advantage of low-end torque, but I don't believe it would be enough to make a notable shift in the powerband. For a general example: the difference between an IM tuned for higher RPM benefit and one tuned for lower RPM benefit is several inches of runner length.

It can be easily calculated, by I wouldn't know how to apply the results. General experience guides me on this, thusly the option of being disproven does exist.

Corbin always thought the spacers would help N/As in regular stop-and-go traffic as well, because while idling at a light, the intake air has a lot of time to sit around and soak up heat from the plenum. The spacer would eliminate that effect and give the car a little more pep while driving around on hot summer days.

I suspect this would be more beneficial than slightly adjusting the point of Helmholtz resonance. I wasn't thinking about stop-and-go traffic in my previous post, and I concur (concede, if you will) that the effects of a phenolic spacer in an NA application will be more noticeable that I previously (hastefully) anticipated, particularly in stop-and-go city commuting.

Phenolic spacer := All around good.

 

[VelocitàPaola]

Adding a 0.375" or 0.5" spacer will lower the point of Helmholtz resonance to the slight advantage of low-end torque, but I don't believe it would be enough to make a notable shift in the powerband.

Oh, but it will. Trust me, I ran the numbers when I designed the thing.

See, if the intake pulse were only reflecting once, that would be true... but if the intake pulse were only reflecting once, the runners would also be something like three feet long. In fact, the runners are closer to 20" long, so the intake pulse reflects about four times (if I remember correctly); ergo, that 0.5" does make a bigger difference than you think.

I know we're both getting to the same point, but I'm just arguing for the sake of arguing here...

 

[Locke]

Assuming rL=84,000; where r=target in RPM, and L = runner length to plenum in inches (shortened and generalized, this is roughly true, regarding Helmholtz resonance as it concerns IM design), then 84,000/r=L and 84,000/L=r. At 20" runner length, Helmholtz resonance occurs at around 4200rpm. At 20.5", Helmholtz resonance occurs at around 4100. I would personally like the see it around 2300rpm for street commuter use, which would mean a runner length of about 36.5", which is uncomfortably long. I still don't see the slight alteration of runner length making a worthwhile shift in the powerband.

This is, of course, not accounting for the runners cross-sectional area, or plenum volume and ceiling height.

I know we're both getting to the same point, but I'm just arguing for the sake of arguing here...

We are.

 

[VelocitàPaola]

This is, of course, not accounting for the runners cross-sectional area, or plenum volume and ceiling height.

Plus, reflected value and RPM are inversely exponentially proportional; you'll notice more of an effect as the intake pulses are reflected as you reach the higher RPM ranges. The induction tract doesn't just resonate once, harmonic waves make just as noticeable an impact as the primaries... I think that equation is a little over-simplified.

 

[4UH8ERS]

hmmm.. Interesting, I like this conversation. continue please.

 

[Locke]

Plus, reflected value and RPM are inversely exponentially proportional; you'll notice more of an effect as the intake pulses are reflected as you reach the higher RPM ranges. The induction tract doesn't just resonate once, harmonic waves make just as noticeable an impact as the primaries... I think that equation is a little over-simplified.

It is very over-simplified, but is roughly accurate. We can account for compression ratio, intake port length, and cross sectional area with something along the lines of this:

Assuming r=c*sqrt(A/[(L+I)V])*sqrt([R-1]/[R+1])*642; where r=target RPM, c=speed of sound, A=runner and port cross-sectional area, V=volume per cylinder, I=port length, L=runner length, and R=numerator of compression ratio.

Given all other variables the same, slight alterations in runner length still only slightly shift the point of Helmholtz resonance.

Granted, as RPM's rise, the fluids velocity (thus momentum) increase allowing for a larger build-up of pressure behind the valve. This could be plotted out as to reveal a slope. Fortunately for everybody else, I haven't been in school in quite some time, and mathematical analysis was never my strong point. My little equation won't account for this.

Concerning multiple reflections, you are counting these at the TB? It seems as though you are thinking about the effects of the design of the product as a whole, where-as I am really only talking about it concerning individual runner length to the plenum. The combination of other features together, if all aimed at the same target RPM, would obviously yield larger gains that those described by the Helmholtz resonance alone.

You make my head ache, Paul.



You have designs in mind for an intake manifold? Any insights about it you could leak to the public for us to ponder/thirst over?

 

[VelocitàPaola]

It is very over-simplified, but is roughly accurate. We can account for compression ratio, intake port length, and cross sectional area with something along the lines of this:

Assuming r=c*sqrt(A/[(L+I)V])*sqrt([R-1]/[R+1])*642; where r=target RPM, c=speed of sound, A=runner and port cross-sectional area, V=volume per cylinder, I=port length, L=runner length, and R=numerator of compression ratio.

Where did you get that equation from? It seems rather complete, but there are no factors to account for effective closed valve duration. I think that variable is indispensable when it comes to calculating resonance.

Given all other variables the same, slight alterations in runner length still only slightly shift the point of Helmholtz resonance.

Perhaps, but my point is that the net effect will be noticeable. Since we have relatively short runners, the reflected value is about four times... plenty of opportunities to feel the shifted point.

Concerning multiple reflections, you are counting these at the TB? It seems as though you are thinking about the effects of the design of the product as a whole, where-as I am really only talking about it concerning individual runner length to the plenum. The combination of other features together, if all aimed at the same target RPM, would obviously yield larger gains that those described by the Helmholtz resonance alone.

No, my calculations are based on a single cylinder/runner design... Either way, multiple standing waves form because the runner simply isn't long enough to accommodate a single reflection.

As the runner length decreases, more waves are created, but the maximum possible gains decrease.

You make my head ache, Paul.

And you mine. It's all good though, I got through this whole thing without actually having to bust out my math or Taylor's book.

You have designs in mind for an intake manifold? Any insights about it you could leak to the public for us to ponder/thirst over?

I have a few things I've worked on... in the end, Helmholtz resonance is only trully beneficial for N/A cars, unless you make the runners so long that it resonates well before the turbo spools. If you do that, however, you've just increased the manifold volume by an order of magnitude [sarcasm] or more, so now a significant pressure drop reveals itself, and the turbo spools slower anyway. So... yeah, it's only useful for N/A cars.

Bottom line: for turbo cars, get as much air in as fast as possible. Magnus is on to something... short, stubby, wide runners, attached to a nice big plenum.

 

[dr1665]

Back to basics for the OP, I would keep things on the simpler side. DEFINITELY pick up the following for the GST:
-K&N direct replacement filter. Anyone who would void a warranty for one of the most well-respected and oft-recommended upgrades to ANY vehicle is not someone you want responsible for repairs to your vehicle - warranty or not. You'll pick up some ponies and improve fuel economy.
-Boost gauge. Simple to install. Simple to remove (if taking the car in).
-MBC. With a boost gauge in place, you can install a MBC in less than fifteen minutes, allowing you the option of turning up the boost a bit.

Give these a shot before going nuts on the 2GNT. Nobody here will be more supportive of you building a 2GNT than I, but it's in your best interest to see how far $200 in mods will take you on BOTH cars. Do the above to the GST without fear of voiding your warranty (just be sure to remove the parts if you take the car in for service of any kind). Then consider the following for your 2GNT.

-Intake Manifold. Have the injector humps knife-edged as mentioned above. Proven gains right there. Get the TB end matched to a 52mm bored stocker TB. That's the upper limit as far as the stocker can be milled without boring through the sides.
-Intake. Pick up an Ebay short ram and be sure you have a quality filter like a K&N on the end of it. Don't pay big bucks for name brand pipe with a sticker on it. You'll see the same gains.
-Exhaust. If you're patient, you can find a used header online for under $100. Pacesetter might be scary cheap, but my Pacesetter header has lasted over three years and was installed used. You won't see much total HP gains, but the powerband will shift favorably. Keep the cat there (for sound reasons, mostly) or upgrade to a true high-flow cat from a quality vendor like RRE. (Most "hi-flo" cats online are NOT cats, expect to pay about $100 for the real thing.) Then round out your system with a nice, Ebay stainless catback in the 2.5" variety. Find a muffler you like and toss the one it comes with. I suggest something with a stock-looking dual outlet configuration.
-UDP. Replace the stock crank pulley with an underdrive unit from your favorite vendor. This mod is commonly called the most noticeable mod you can do to an NT car.
-Suspension and wheels. Pick up a nice suspension set up, keeping in mind that a high quality, true coil over set up might run you a grand or more, but will be the last suspension set up you ever buy, and some wheels/tires that make you proud to roll the car.

The above mods will provide you with a good foundation for working on your DSMs and provide you with a much more enjoyable experience behind the wheel. The benefit to you with a pair of FWD 2nd gens is that, should you decide to make the GST your main project, you can swap over the suspension, wheels, tires, and catback off the 2GNT directly to the GST without any modification or waste of money.

Test the waters on both sides before making your decision. You might find you'd rather mod the hell out of the GST and keep the 2GNT as a reliable, gas-mileage-friendly ride to get you where you need to go. Then again, you might decide to do some BPUs to the GST, making it reasonably quick, while you strip the GST down and make a full drag car out of it just to do something different.

If you don't find the answer you need over here, keep in mind that 2GNT.com is like DSMtuners polar opposite, focusing mainly on the NTs, while providing a little corner for the 4G63 guys to talk shop. It's not about which DSM community is the best anymore to some of us. These days, some of us are all about making sure the new guys get the technical info they need so they will stay in the DSM family for the long haul. With all the new cars coming out these days, it's important that people see the big picture and value being a part of the DSM community, as a whole, just as much as they value building a bitchin' car. Good luck with your project.

 

[VelocitàPaola]

Leave it to Brian to bring us all back down to Earth...

 

[Locke]

Where did you get that equation from? It seems rather complete, but there are no factors to account for effective closed valve duration. I think that variable is indispensable when it comes to calculating resonance.

A simplified Helmholtz formula: r=c*sqrt(A/[LV])

642 is the coefficient used to make it applicable, found in a notebook describing past projects. Likely sourced from the net or a textbook some time ago.

sqrt([R-1]/[R+1]); is used as a generalization to account for the effects of CR. This was in my notebook as well, also from unknown origin, concerning effects of pressure on the speed of sound as it applies to automotive practice. I applied it as the missing (static) pressure variable of a more accurate Helmholtz formula.

I accounted for the length of the intake ports, but did not account for the difference in cross-sectional area between the port and the runner. I figured they were close to the same, anyways. Call it laziness, if you will. Easily expandable.

If you can figure for closed valve duration, and apply it, let me know. Useful stuff.

You say it seems rather complete; do you have a more accurate formulation? There is no point in my trying to figure for something that is already known to others. I would feel foolish to put much work into it, ya know?

Perhaps, but my point is that the net effect will be noticeable. Since we have relatively short runners, the reflected value is about four times... plenty of opportunities to feel the shifted point.

No, my calculations are based on a single cylinder/runner design... Either way, multiple standing waves form because the runner simply isn't long enough to accommodate a single reflection.

As the runner length decreases, more waves are created, but the maximum possible gains decrease.

See, I am no scientist or mathematician, only a hobbyist. I figure for some theories of elementary physics at work. Perhaps you could PM me with the details of multiple resonances, and how it is figured? I am always receptive to understanding new (to me) ideas.

My stating that the effects would not be very noticeable were only speculation, based on my limited knowledge. Realizing that you have obviously put much more thought into this than I, and have more tools at your disposal, I will trust you. The gain may be more noticeable that I anticipated.

And you mine. It's all good though, I got through this whole thing without actually having to bust out my math or Taylor's book.

I had to scour through old notebooks, and dig for my calculator.

I have a few things I've worked on... in the end, Helmholtz resonance is only trully beneficial for N/A cars, unless you make the runners so long that it resonates well before the turbo spools. If you do that, however, you've just increased the manifold volume by an order of magnitude [sarcasm] or more, so now a significant pressure drop reveals itself, and the turbo spools slower anyway. So... yeah, it's only useful for N/A cars.

Bottom line: for turbo cars, get as much air in as fast as possible. Magnus is on to something... short, stubby, wide runners, attached to a nice big plenum.

I completely agree.

Leave it to Brian to bring us all back down to Earth...

Yeah.

 

[dr1665]

Leave it to Brian to bring us all back down to Earth...

Yeah.

I am Spartacus.

Good to see some serious technical jargon up in this heezy though.

 

[BigRand]

"This is madness".............................."This is SPARTA"

I am Spartacus.

Good to see some serious technical jargon up in this heezy though.

plus one