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!