ITB'S Can it be done?
 

Being I am not too up to date with the rx8's engine I figured I would throw this out there and let people give me some input. I am alot more familiar with toyotas/hondas so forgive me...In the world of toyotas/hondas itb's preform really well and you can do this upgrade fairly cheap and easy. I am not going to ask if it is possible because I know it is possible. But what I am asking is can it be done in a cost effective manner and what exactly needs to me upgraded or modified as in tps/throttle cable or fly by wire/air flow sensor? Im guessing I am not the first to think of going to itbs so any pics or info would be greatly appreciated.

Thanks

How would ITBs work on the Rotary?

Air flow sensors are for pussies!

Mount your Webers on a new upper manifold, cable throttle, cable choke - what's stopping you? Go for it!

S

And people wonder why some of us old timers here have attitudes. :banghead:

it will only work in a very limited RPM range, it will never match the OE setup in broadness of range

what are you getting at?

Ok Thanks for your input. It was just something I was daydreaming about.

haha thats great!

if it was worth doing it would have been done already.

clearly this is true. I mean the car is what, 4 years old, and the FC is just now getting serious attention in regards to ITBs. So obviously if it hasnt been done in 4 years it isnt worth it. :icon_no2:



As far as power is concerned it would probably change the powerband somewhat. Depending on runner and airhorn length you could adjust where the meat of the power band is. I completely disagree with the idea that it would only work in a very limited rev range. This has been demonstrated to be false in many applications.


The problem is going to be that you need a speed-density standalone, or a plenum to run the MAF off of. A plenum takes away the adjustability of changing airhorns, and a stand alone results in lost OEM functionality. So its a big trade that a lot of people are, at this point, not willing to try out.


BC

wow,

your posts continue to get worse..

beers :beer:

I dont think he is. My post count does not reflect the amount of time I spend here and at RX7club lurking. His posts have, IMO, always been well thought out.

However ITBs have been demonstrated on many platforms (miatas, hondas, BMWs, Ferrari's etc) to promote incredible throttle response, power gains nearly everywhere, and a broad power curve.

The argument in the case of the Renesis is the fact that the stock intake manifold does so much to broaden the torque curve. This is something that, when replaced with ITBs, would obviously be lost, but not completely. It wouldnt help 'only' in a very limited RPM range, but his thought that it would narrow the torque band is correct.

My belief is that the increased throttle response would go a long way in offsetting this loss. Particularly if you went with a longer airhorn to try to maximize low end torque. You would lose something in the upper RPM range, in relation to a shorter airhorn, but I think, if appropraitely sized, that the loss would be minimal.

So long as you can keep the aux ports functional in the process you could have a strong low end response (viscerally this would be compounded by the near instant throttle response) with improved breathing at high rpms. Just because the airhorns would be sized to improve low end torque doesnt mean that you are going to hurt the top end. it just means that you are going to lose some of the benefit found in pressure wave tuning.


Personally I would love to see someone come out with an ITB kit for the RX8. I just think that when placed in a hp/$ argument the ITB is always going to lose. Peak hp increase wont be huge, but area under the curve would probably improve significantly. However all of that would be at approximately the same cost as a turbo set up. The other option would be to design a system that left most of the stock intake manifold intact, but moved the trottle bodies closer to the ports. Similar in effect to what OEMs typically do with ITBs. You lose the ability to tune for your desired RPM advantage, but still retain the improved throttle response and gain the ability to use the stock MAF and probably computer. IMO this is the worst option from an aftermarket perspective though it has the advantage of not needing a standalone and the associated loss of stock options (Cruise for instance).

BC

i disagree that it couldnt be beneficial, the reason no one has done it is because of cost effectiveness I beleive. a system that would show Hp increase through out the rpm range would have to be a variable length ITB system as seen on the 787b. the rx8 already uses variable length runners, however only a single throttle body and no plenums, I beleive with individual plenums that are variable length would show an increase all through the rpm range when tuned right

Anything can be done. There is a place for every setup as well as a time not to use it. For street use it's really going to be tough to beat the stock intake manifold. It is very well designed and does a good job of providing the powerband and drivability that a street car needs. for forced induction use I also wouldn't want to change to ITB's.

For a race engine however things can be very different. ITB's are simple and elegant. Simple is always a good thing on a race car. There's something about them that just screams race engine. Compared to the stock manifold there's no doubt that the powerband would be narrower. For a race engine that's fine though. Throttle response would be crisp and fast and the intake would scream. No noise control here! Speedsource uses the stock manifold on their Renesis race engines so they can't be all that bad for race use. It's true that peripheral port engines use ITB's but they are naturally configured for them.

I'd like to see someone try it and report the results. It may not work that well or it may work fantastic. The real question is over what rpm range?

im going to try it, even if it dosent work, i dont care... but if it does work for my application... (track use) ill make an affordable kit, anyone serious might wanna wait, i have free dyno time and i already have fabricators that can make custom pieces.. i can save time and money for all of you and let you know how its going.. but i cant do crap until i get back from canada.. sometime in may

im doing alot of things because i have all the same questions...

also, ill be traveling to japan every now and then to see what they are doing over there that they dont put in the magazines.. maybe i can see some of their itb renesis that are floating around out there.....

het rotarygod, you have any other ideas on that exhaust manifold

does anyone else have any serious interest in this, if so subscribe now, when i get back to cail ill be trying some stuff once my site is up and will be posting picks here.

ps. hopefully ill have some stuff ready for sevenstock.

Thank you, did a search and subscribed to it. I know of crispeed from when I was on the RX-7 forums back in 2001. I had an 3rd Gen with a T-78. Man it was fun.

I also found photos of me and my car in sevenstock 5.. hahahaha, I had a complete ab-flug bodykit wing n all, volk gtn's and a 6point red powdered coated cusco bolt in cage. Worst mistake I ever made was getting rid of that car.

Anyways, Thanks CRH

Ben

hahah, i was hoping no one had said that so i could be the one to point that out. :lol:

i'd love to see what it does on a 13b renny. would be interesting. if it had similar gains as to a CAI, people would still buy it. as RG said, something about ITBs scream race engine. and driving a race car is something we all wish for. (except the expense. :P)

as RG put it, i am after the same tq curve and crisp throttle response in the upper rpm range, but im shooting for a minimum of 15 whp peak.. if i can't get this it will not be worth making for sale as a kit. too much money for not enough power... that is unless people want to buy it for the cool factor.....lol

Don't underestimate the amount of money people will spend on the "cool factor".

Cel

I've got a hunch that any ITB setup on the Renesis that does make more peak power than the stock manifold won't have near the nice average powerband that the stock one does. The stock manifold is so good that they are retained on race engines.

+1 on that. Seen with my own eyes this I have :)

^ no arguing here, but it will still be cool to see how far i can get with testing different possibilities.

as for the stock upper intake manifold being on race engines, what other upstream modifications do they do to it..

and also i do not know of the regulations, do they say they must keep the upper stock intake manifold?

Links to my post #20

it's me, 1994 rx7, complete ab-flug bodykit and the ab-flug spoiler, power fc, jacobs electronics, had a wideband on it, volk gt-n's 18x8 front 18x10 rear, 6 point cusco cage powdered coated red, apexi front mount, greddy t-78, 1600cc secondaries, scoot carbon fiber hood, a few other stuff i cant remember.. so ive got some past rotary experience...lol

http://sevenstock.org/Photos/Sevenstock5/SS5_00100.jpg

http://sevenstock.org/Photos/Sevenstock5/SS5_00173.jpg

They even keep the stock intake complete with paper air filter and no they don't need to!

This is going to be a fun adventure none the less, I just want to come back home and get the site up and the business started already!!!!

any updates on this one? also i was wondering if this 13b kit could work or be modified to work tweakit.net

Tweakits kit is awsome but requires additional management, the one I'm going to work on will be a hybrid itb set-up that will still use the factory engine management and sensors.

There will be no-updates for a few months, but expect it to be ready by sevenstock

Ben

There is no reason a tweakit kit would require any more or less engine management than anything else. You absolutely must retune for any setup anyways.

true, but for tweatkits kit, it requires more of a custom set-up, mine should be bolt on if all works, its not wotrh selling as a kit if it is not cost effective vs the whp gain. but it will be simular to the gtir set-up which works really good.

ya obviously tuning will be required regardless i was more curious if the intake manifold for the ITBs would fit a reni? they say 6 port but.... im not sure

^ "they say 6 port" did you find something that says they have itb's for the 6 port, i can't figure out who "they" is, i dont see an itb kit for the renesis on tweakit's site

thanks

If it says "6 port" but doesn't specifically say Renesis, then it's for a nonturbo '86-'91 RX-7 engine. The intake runners and bolt pattern are nowhere even close to each other and adapting one to work would be more difficult than just making a new one.

the more i look at the intake system the more respect i have for the factory design, a huge amount of time and engineering must have been put into it. it is going to be fun, difficult and extremely challenging to make a hybrid itb set-up that will be a complete bolt on kit and make more power.

oo ya good point def is for an fc, my mistake.

Buy why ITBs?

Why not a larger throttle Body attached to a better designed air intake box, with a larger ram air intake duct?

Simple things like taking out those "plastic guides" in our air intake box, catch can with breather appear to have positive effectives, and CAI ducts (Odula) and ram CAI ducts (Racing Beat).

The combination should give you more air and more power. This would use more fuel, but this could be mitigated with tuning and isolate the effect at WOT and high speed.

I'm thinking an air intake system that flowed more air would be effective and it's practical use would not be limited and would be fine for a daily driver.

im going to retain the single tb, because its a good size, i want to retain the features of the stock set-up because it works, im just going to modify it a bit

itbs for better throttle response, this is going to be difficult to make a kit that will yield results for the dollar spent for the kit

its going to be fun doing this while retaining the electronic tb

also it will still be compatible for FI.. turbo, the sc i see make you change to their upper intake manifold so they will not be compatible.

i wonder what it would take to hav a manifold made to fit the tweakits kit to a reny. they hav a kit with tapered throttles that i hav my eye on. :) ino that the $/hp isnt very good but.....insane throttle response ftw. also theres def. no need for a bigger throttle body as ours can already flow much more air then our ports, wouldnt a bigger throttle body just make throttle response worse also?

The stock throttlebody is already capable of flowing more air than the engine can ingest on it's own so I see no reason to use a larger single one. Multiple plates, even with greater total area, change the rules a bit.

mhmmm thats wat i thought

anyone know someone who makes custom intake manifolds. i want one that will fit the tweakit throttles to a renny.

How do you want to do it? Do you want to use 3 throttle plates or 2? I have a Renesis intake manifold lying around so making flanges isn't hard to do.

ooo i was thinking 1 per rotor just cuz the tweakit's kit. but 1 throttle per two ports would be nice too... what do u think?

The easy way would be to replace only the upper intake manifold. By keeping the lower you have 3 places or air to go. You have the rear rotor, the front rotor, and the auxiliary ports. You could have a throttle plate for each one and still retain the VDI and other features.

The other way would be to use only 2 barrels as you have suggested but still retain the stock lower manifold for it's features. Instead of keep the upper aux. port plastic runners, those could be replaced with runners built into the upper that keeps them separated into front and rear rotors only. Neither is necessarily any harder to do than the other.

BTW: I have a Weber carb lying around so I can easily get the flange dimensions for it too.

for what im working on, it will still use the maf, i want to make it a bolt on kit that will still function with the factory computer. i also want to use the maf so that a turbo kit can be used with the set-up..

rotarygod, i know you know this, but i want to remind others that this is fly by wire and no tb cable which makes it more intersting.

i want to retain some of the following features
"sited from the rx8 book page 115"

S-DAIS (sequential dynamic air induction system) for the high-power RENESIS. Six valves are employed to alter air passages. The rotary's unique intake interation is used to feed more air.

Low-speed zone ( WOT 3750rpm)
air goes through the long tube infront of the airbox and only into the rear port of the front rotor and the front port of the rear rotor.. or the inside ports between the rotors.

Mid-speed zone (WOT 3750rpm-5500rpm)
air goes through the long tube infront of the airbox, two valves open up, one for each rotor, and now air is fed to the inside ports and the outside ports.

Mid-speed zone (WOT 5500rpm-6250rpm)
air goes through the long tube and now the short tube infront of the airbox, two valves remain open , one for each rotor, and air is still fed to the inside ports and the outside ports.

Mid to High speed zone (WOT 62500rpm-7250rpm)
air goes through the long tube and now the short tube infront of the airbox, two valves remain open , one for each rotor, and air is still fed to the inside ports and the outside ports, two more valves open, one for each rotor, and the auxiliary ports kick in.

High speed zone (WOT 7250rpm to redline)
air goes through the long tube and now the short tube infront of the airbox, two valves remain open , one for each rotor, and air is still fed to the inside ports and the outside ports, the valves for the auxiliary stay open and the last valve between the runners going to the inside ports opens creating an additional pathway in the manifold.

there are a total of 6 valves that open that create 5 different pathways for the intake system.

so the challange is to make a hybrid itb set-up that will not lose power down low, give better throttle response, make more top end power and top end tq and still run within limits that the factory ecu can control.

this is the mission

Keeping drive by wire on an ITB setup is going to be difficult but not impossible. It will require some custom fabbing to make the stock tb motor fit. I have a stock tb lying around too!

rotarygod, do you have a spare upper intake manifold for sale also

i would like to buy them off of you, the tb and upper intake mani, i am not in a rush to push out something that wont work, but i would like to have a prototype ready by sevenstock

yes it will be difficult, but more fun then anything

ya i like that first option RG. 3 sounds real good. i was already thinking about keeping the lower intake mani just to keep the other features and to keep the butterflies up higher. what does the weber hav to do with it?
ps i was def thinking about throttle cable.
pps do u think the AP would work well with the ITBs

damn, ITB will sound so crazy on the renesis...... but did anyone see the 4 rotor scoot weith itb.? so sickkkkk~~~~~

:naughty: ya def will sound amazing, and yes i did see that..... :naughty: