has anyone ever looked into bonnet mods to feed thier intakes?, cai or otherwise?

while its nice to have them long pipes for cai, is there a thoery on the length of these pipes, or more like if they are too short? for example, if one was to have a air inlet in the bonnet right above the stock snorkle area, and fed it properly filtered/etc into the airbox, i would say the air may be moving too fast at that point perhaps?.. chatter in the cai post today there mentioned air speed in the intake, should the intake draw the air in, or have it pushed in?

imho, i would like to think the intake should draw air in as needed with minimal resistance as possable, rather than having it shoved into the intake through phat pipes/mountings making a messy air flow?.. like some sort of shonky low grade turbulent pretend turbo effect?

most of these designs of amc'ers cai mods look to be in the right spot not to be rammed with air, so most of these designs prolly dont have that effect.


thoughts?

Ram air is good not bad. You will probably get very little positive pressure but its best to site the intake on a high pressure zone of the car(like the front) rather than on the bonnet unless it has a raised scoop.

Turn the engine around so the intake is at the front then remove the radiator and have direct ram..:P

:rant: :rant:
My myyy - it's way better to turn the donk upside down. Geesshhhh...

Aaanyway, ram air is good, provided the inlet really is in area of positive pressure. Not all sections at the front of car are positive, some might be less. Bonnet scoop would definitely be positive. Depending on car speed, revs, size of piping, eventually there is a point where the ram air is theoretically beneficial - faster air speed than what the engine requires. But, considering that surrounding air pressure fills vacuum by ruffly speed of sound, which is way greater than any other factor, the ram effect is bit theoretical. :)


Turn the engine around so the intake is at the front then remove the radiator and have direct ram..:P

Kawasaki have ram air on their bikes and alot of people talk highly about it... there's no doubt about fresh air forced into your intake giving you more power. Go download some leaf blower dyno runs if your keen =P

I was just thinking about plenum designs today before refitting my plenum back on... I am looking into making a REALLY short runner plenum at the moment. I still have to find more information about WHAT MAKES THE 3L PLENUMS RESTRICTIVE! Are the runner sizes ok? Because I could use the stock valley and EASILY make a new (very basic) plenum and perhaps cut off the ECI Multi 3000 and weld it onto the new one to make it look stock(ish).

I took some short runner prototype magna porn pics check it out... attached.

Another thing I'm looking into right now is freeing up area in my engine bay so other modifications can be done... for example, I have moved the Fuse box and taken out the battery support bracket. Basically what I am thinking to do is:

1. Put a battery box over on the front left of the car where the radiator overflow bottle use to be. Extend the positive and negative feeds to that side of the car with the right wiring, run under the radiator cable tied and taped to the stock loom.

2. Using the area where the battery was... make a heat shielded air box for a pod to sit into. The AFM would bolt up to the back of the box making it look relatively straight. From the AFM I'd have to have some form of rubber/plastic piping which would be really small and connect to a steel pipe which would then run into another 10cm bit of rubber/plastic mounting onto the TB. I would then cut a comfortably large hole in the bottom of the box and duct some air into the box from the front bumper. Perhaps 2x 3" Pipes welded to the bottom of where the airbox is onto the body which run from two big scoops behind the bumper, or grille.

But yea... my main priority right now is finding out what exactly are the flaws with the stock intake manifold designs and how people have improved it, and what goes into making an intake manifold etc. I'll start searching now, but some thread links would be nice.

Don't mean to steal your thread, if I should make another post I will do so... might as well have one big intake post though!

cool man, its exactly what i was trying to do, get a yarn goin about differnt styles of intake and the ups n downs of various designs.

i personally see the good parts in the usual cai tubes designs, and seeing as there is such a huge market for those particular designs, then one would say there a very good design.

while im no physicist or anything, i am interested in not-what-every-one-else has type ideas now and then.

i dont think a tunnel-ram / bonnet scoop is really the go, lets be honest, were talking about road cars here, not top fuel drag cars.

and i would have faith that so much money poured into the design of a given system, factory or 3rd party would atleast have some major merit to its design.

but as posted here today, i would like to see if theres any stats out there about the volume/velocity of air in the standard intake, and what the engine, in 'standard' configuration really requires, and the effects of aftermarket parts, like upgranded exhausts/engine parts/etc.

EZ boy was on the brink of producing custom Plenums, but family commitments overtook him.

Search under his username with "plenum" keywords.

Here's an example. Prepare to drool..:D

http://www.aussiemagna.com/forums/showthread.php?t=29485&highlight=manifold

Well xwhiskey, fabrication of a possible intake kit and custom plenums are under discussion and planning at the moment between some magna guys and my father has been a boilermaker for 35+ years and I have lots of equipment at home (Welders etc) and he works on a profile cutter which can cut steel plate to whatever shape or size I want... so thats why it's relatively easy for me to whip up manifolds and the such. I just have done so much other crap getting the magna back in shape to worry about modifications that dramatic JUST yet... but soon =)

EZ boy was on the brink of producing custom Plenums, but family commitments overtook him.

Search under his username with "plenum" keywords.

Here's an example. Prepare to drool..:D

http://www.aussiemagna.com/forums/showthread.php?t=29485&highlight=manifold

Yea Mulga apparently he can't do them anymore or something I heard? It really wouldn't be too difficult for me to fabricate things like a plenum. Having design plans would help alot though, I'm not too sure how the internals of it should work. When I opened up mine there was butterflys in it and two passages etc...

Edit: Also, why has he got two pipes for each intake port? One larger pipe would be much more effective and efficient, surely.

Yea Mulga apparently he can't do them anymore or something I heard? It really wouldn't be too difficult for me to fabricate things like a plenum. Having design plans would help alot though, I'm not too sure how the internals of it should work. When I opened up mine there was butterflys in it and two passages etc...

Edit: Also, why has he got two pipes for each intake port? One larger pipe would be much more effective and efficient, surely.

The discussions in his threads provide an absolute wealth of information.

He really new his stuff, and spent alot of time researching, plus I believe his Dad is an enthusiast and had alot of input and knowledge from working on old Fords and the like. :D

In answer to your question about the twin-intake runners, this is from that particular thread.

By using long thin runners we achieve a high intake air flow velocity, shorter length runners will move the start of the torque curve higher into the rev range, as will larger diameter pipes. We've used twin long, thinner than stock runners to achieve a much higher inlet velocity as well as outflow the stock runners by 20-25% per cylinder. The square plenum actually assists runner resonance by reflecting the pulses back down the runners and increasing the air speed down the runner.

Many thanks to the Honda and Ferrari Formula 1 development websites for their input in this project

Great I just finished reading the thread. I didn't see however, him saying anything more about it... has he gone or what's the go with them now?

I didn't know that the 3L intake manifold was restrictive. From what I have picked up most of the problem is with the design of the plenum chamber, not the runners. As has been said earlier the length of the inlet runners determines where they will generate the most torque due to a wave reflection or 'ram' effect. Here's a page that explains it better than I could, along with the equation you'll need, it was posted earlier this year by someone, can't remember who.http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=466
It's a very interesting read if you're interested in tuning.

As you'll be able to tell after reading that article, short runners will give you bugger all torque down low. Ideally you would tune cams, inlet manifolds and and exhaust for the same rpm, giving you a big lump of torque where you want it.

edit: article was first posted on AMC by Anon, here (http://www.aussiemagna.com/forums/showthread.php?t=36725&highlight=inlet+manifold)

There are some over simplifications and errors in that information, perhaps due to the person wanting to sell things? I would strongly suggest that you read more widely than this one page (I am sure that you have).
There are very very good reasons to go ITB on any sporting NA engine, cost is usually the limiting factor.

I didn't know that the 3L intake manifold was restrictive. From what I have picked up most of the problem is with the design of the plenum chamber, not the runners. As has been said earlier the length of the inlet runners determines where they will generate the most torque due to a wave reflection or 'ram' effect. Here's a page that explains it better than I could, along with the equation you'll need, it was posted earlier this year by someone, can't remember who.http://www.team-integra.net/sections/articles/showArticle.asp?ArticleID=466
It's a very interesting read if you're interested in tuning.

As you'll be able to tell after reading that article, short runners will give you bugger all torque down low. Ideally you would tune cams, inlet manifolds and and exhaust for the same rpm, giving you a big lump of torque where you want it.

edit: article was first posted on AMC by Anon, here (http://www.aussiemagna.com/forums/showthread.php?t=36725&highlight=inlet+manifold)
Yeah unfortunatly there is a lot more to intake design than just slapping on some drain pipe PVC and expecting it to make a difference. While working/designing the FSAE engine for uni, I spent a few days solid designing a simple 4 cylinder setup for the specific cam, head, capacity, power and torque range we needed. And in the end it gained a decient 8hp over the standard setup. Similarly, if you just slap random stuff on you could probably expect to lose that 8hp.

Thats a very good read, and for a comparison, the FSAE car had a very similar write up but a lot more calculations and much more detailed.

By using long thin runners we achieve a high intake air flow velocity, shorter length runners will move the start of the torque curve higher into the rev range, as will larger diameter pipes. We've used twin long, thinner than stock runners to achieve a much higher inlet velocity as well as outflow the stock runners by 20-25% per cylinder. The square plenum actually assists runner resonance by reflecting the pulses back down the runners and increasing the air speed down the runner.

Many thanks to the Honda and Ferrari Formula 1 development websites for their input in this project[/QUOTE]


Reflection plate theory is very much a trial and error task and will only work at a certain rpm/load. Other methods involve cross-ramming the intake pulses between different cylinders etc. The issue is the control of such teuning methods, specifically controlling the adverse effects at less than the optimum point.
You could feasably do the runners as described, it is simply a copy of the TVIS toyota system, but as described may be less than desirable. that is a very big reduction in cross sectional area and you would have to carefully model it on the computer. Again it would be affected by many variables.

So stock runners are relatively ok? Im thinking about using the standard valley and just make my own runners inbuilt into the plenum and making it one piece bolt-on onto the valley... and make it so the runners are as short as possible, just allowing the plenum to sit over the rocker covers, then the TB out the side... would cost me only time to do, and would be piece of cake to make a big square plenum and some pipes then a plate which i can juist make a template for and get my old boy to cut it at work... I just need to find out what the internal stuff (butterflys) and the sensor on the outside would be like with that... do I need it/them?

^^^That'll be an absolute pig to drive on the street. I really would advise against doing that. Also with that big a change you would definately need some form of piggy back or replacement ecu

Yeah unfortunatly there is a lot more to intake design than just slapping on some drain pipe PVC and expecting it to make a difference. While working/designing the FSAE engine for uni, I spent a few days solid designing a simple 4 cylinder setup for the specific cam, head, capacity, power and torque range we needed. And in the end it gained a decient 8hp over the standard setup. Similarly, if you just slap random stuff on you could probably expect to lose that 8hp.

Thats a very good read, and for a comparison, the FSAE car had a very similar write up but a lot more calculations and much more detailed.
FSAE eh? What uni were you with? I'm with the Adelaide uni team, I'm only in second year but by 5th year me and a coupla others plan to have the design all nutted out. Hopefully scrapping the old CBR600's for a kei class car engine that'll have a helluva lot more torque :badgrin:.

Definately that article is very simplified, but it will point him in the right direction. The best way to do it would be first in Ricardo or another angine analysing software, and then on dyno tuning. But that isn't exactly available to most people. ;)

^^^That'll be an absolute pig to drive on the street. I really would advise against doing that. Also with that big a change you would definately need some form of piggy back or replacement ecu

FSAE eh? What uni were you with? I'm with the Adelaide uni team, I'm only in second year but by 5th year me and a coupla others plan to have the design all nutted out. Hopefully scrapping the old CBR600's for a kei class car engine that'll have a helluva lot more torque :badgrin:.

Definately that article is very simplified, but it will point him in the right direction. The best way to do it would be first in Ricardo or another angine analysing software, and then on dyno tuning. But that isn't exactly available to most people. ;)

I was at JCU durring my 4th year as a mechanical engineer. The program had only just started and I had only just recieved the motor (CBR600) before I graduated so I didn't get a chance to put any of my theory (and boy was there some of it!) to practice.

They scrapped the idea of new intake and plenum because of budget and lack of onboard knowledge once I left :cry: Unfortunatly I was the only one with the experience and skills to convert it to EFI and get results. Now they are just running either 1 single injector or the carbi setup if they are allowed :doubt:

you can download a working trial version of engine analyser pro and trial things. It works well enough for this.
3ltr, I would advise you to leave the plenum as it is. Despite the often seen custom plenum in some magazines, designing such a thing is not easy. The OEM engineers are talented guys with a lot of resources and what they have done works. You will get a much better return on your investment focusing on other areas of the engine.

Hey tommo, I don't care what it's like... if it cranks at high rpm, then I'll just bolt it on for me n my mate to go for a thrash with and then swap it back over! Engine management is a problem though. BUT at the end of the day.... if I get like $1500 or so worth of EMS, I can fit it to any car I have right? SO, It would be a decent investment considering I can do metalwork for relatively cheap, and on a large scale (Custom intake/exhaust manifolds, exhausts, turbo conversions etc)

I have been thinking about better platforms for a race car to work with... and so far the R31 is a favourite of mine, always has been.. I have owned a couple now in the past three years... but I always think of the 3000GT engines and know I am better off just bombing the Magna.

At the end of the day(Year, lol) if I end up with a DOHC 3L M90+ Supercharged/T4 turboed 250kW atw then I'd be happy to keep the Magna for another 5 years... I have replaced the seats inside already and roof lining and getting new carpet, putting paint on next weekend... rims within a few weeks when its rolling again, brakes are ok... has 2.5" zorst... Maybe I should just buy a new Barina for work and bomb the magna and leave it off the road. Decisions, decisions, time for tv.

1 single injector:shock: . Damn that'd suck. They should see if they can source the injection equipment from the F4i model. Even if they ran it on the stock ecu it'd make a massive difference. Last year Adelaide's entry failed to finish, not through a mechanical fault, but because a driver didn't make it round a corner and broke off the front wing lol. My year is the first time that non final year students can become proper members with input. Apparently over the past coupla years the teams kept making the same mistakes over and over.

Anyhow back on topic.:redface:
3LTR have you thought about using a two stage runner system, like EZ Boy's design. Have long runners for low rpm torque and then a solenoid actuated butterfly to change over to short runners at higher rpm. I can put up a pic if you want.

well i got the bigger inlet plennum with ram tubes from RPW,
i gained nothing with putting this on. so then went out and got haltec, still gained nothing from it.... maybe some torque but thats about it.

well i got the bigger inlet plennum with ram tubes from RPW,
i gained nothing with putting this on. so then went out and got haltec, still gained nothing from it.... maybe some torque but thats about it.
Yeah I really dont think that the plenum or intake are a problem hey.

How did your haltech go?

well i got the bigger inlet plennum with ram tubes from RPW,
i gained nothing with putting this on. so then went out and got haltec, still gained nothing from it.... maybe some torque but thats about it.

EZ Boy really did make it sound like it gave him ALOT more power in this thread...


What about just modifying the top of the plenum so its larger... then grind off the TB mounting and remake it. Only problem with doing this is that you would have to find a way to keep the use of the plastic things in that top part, as they wouldn't line up anymore.

Hmm, RPW claimed "massive" power/torque gains with their plenum.... But your comment negates all that. Buger, just when I've been in process of ordering one, perhaps I should wait and keep following this post.
Wonder how many ppl have RPW plenum and what kinda gains?

To the matter of designing such plenum chamber. It's not just bending pipes and creating a box as some wise members mentioned. How about doing a 6 TB set-up? Much easier to design and trial simply by varying the pipe diameters and lengths. Just that buying those 6 TBs (even if generic) would cost a bit.....


well i got the bigger inlet plennum with ram tubes from RPW,
i gained nothing with putting this on. so then went out and got haltec, still gained nothing from it.... maybe some torque but thats about it.

6 throttle and trumpets would be angry :badgrin:

Sluprsss......:mad:

How much does a "generic" TB cost? Heard of figures of 150 bux ea.


6 throttle and trumpets would be angry :badgrin:

6 TB's with no plenum and a straight runner.... indeed that would look mental =)

Seriously guys - any one interested? Tuning the "pipes" would be way easier than a plenum system. Configuring cabling/linkage would be bit of work, but. And we would lose Cruise.
But the benefits!
I'll do some research on billet TBs if I have time in the office. I reckon 35-40 mm barrel would be good?


6 TB's with no plenum and a straight runner.... indeed that would look mental =)

6 throttle and trumpets would be angry :badgrin:

Neck snapping throtle response I would imagine.

After that, clean up the heads a bit, increase CR to about 10.0:1/10.5:1, ballance the crank and slap in some nice cams.....ahhhhhh:P

I am already heading that way, but I do not have the clearance issues that a magna would have. It would be possible to make up the ITB full system and I have cast my own TB's in the past. However, by itself it will possible not make a huge difference, as part of a high CR engine with the appropriate tuning it would work well, but that is around $7k of mods and NOT road legal.

I know this is an 'older' thread, but I spotted this on the US ebay site and thought some of you would at least like seeing it...

http://cgi.ebay.com/ebaymotors/3000GT-Stealth-N-A-Aluminum-Sheet-Metal-Intake-Plenum_W0QQitemZ290032596337QQihZ019QQcategoryZ364 74QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I know this is an 'older' thread, but I spotted this on the US ebay site and thought some of you would at least like seeing it...

http://cgi.ebay.com/ebaymotors/3000GT-Stealth-N-A-Aluminum-Sheet-Metal-Intake-Plenum_W0QQitemZ290032596337QQihZ019QQcategoryZ364 74QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


I have a feeling that there would be distribution issues in that manifold if it is simply a 'log' added to the std cast runners.

Looks like our runners welded onto a larger plenum. From EZ Boys thread it seems the design of the runners also needs to be modified to see gains.