I've been looking into ITBs for a bit, and I found a link on a honda site where a DIYer made ITBs for his Integra GSR drag car for pretty cheap, like 300$. He used 2002-03 GSX-R throttle bodies (750 or 1000 , same size those years) and basically welded those to a cut off stock manifold flange with some velocity stacks. This is the link to that article,

http://www.honda-tech.com/zerothread?id=975931&page=2

theres pictures on pg 2. I want to do this on my SVTF but I want to put a plenum over it and use the stock maf. Similar to this guys zetec

http://www.fastraxturbo.net/Images/Photos/DSC_1641B.jpg

Im confident I can make it, and make it fit in the engine bay. What Im not sure is can a stock maf and stock ecu handle this mod? Our stock TBs dont have a TPS sensor that Im aware of, so the only sensor envolved is the maf. Anything that was connected to the stock manifold could be hooked back up to the plenum. I would use the bottom half of the stock manifold so the fuel rail/injectors would be in the same spot. I also want to get the TBs as close to the head as possible so I can turn the runners approx. 45-60 degree's to the right to give longer runner length for a better power band. Obviously getting it tuned would net a lot more power but untill I have the money for that I dont want to make this and have to wait months till i can get a tune from Tom to use it. Feedback?

1. the stock intakes are plastic
2. they do use a tps
3. been tried and wasnt worth it on a stock motor since the svt has a dual runner manifold

our throttle bodies dont have a TPS?

Im probably wrong on the TPS, i took it off the TB to port it and I dont remember seeing one but I could be mistaken.

I know the stock runners are plastic, i would have a rubber coupler just like the second piece of the stock manifold. The TPS is a problem, but not unsolvable. Not worth it on NA? regular Zetecs can put 180whp with cams and itbs? Stock svt puts up like 145ish, im sure theres gains to be had.

the SVT manifold is miles ahead of the std zetec as it is so the gains might not be what you think.

and i believe that build had a lot of compression on it too, like 11:1.

but if youre still interested, just put a tps on one of the itb's and make one linkage to connect all of them, boom problem solved.

I agree you will have troubles using any piece of the stock manifold, youre better off doing a custom out of aluminum.

I'm going to go ahead and be the [:)][:)][:)][:)][:)][:)][:)] on this one and say that you do not possess the fundamental knowledge to pull this off. Like I tried telling them dip-shits on FJ years back, once you put a plenum around an ITB it looses it's ideal function and becomes just a manifold that is more complicated and has 4 times the moving parts.

our throttle bodies dont have a TPS?

Yes they do, I've had to replace mine.

The problem with ITB's in our cars mainly is placement. Look under your hood, you have maybe 6inches of room and it's at the rear on the engine bay. Not ideal position for ITBs and the cost would most likely out weigh the benefits. A used supercharger can be had for cheap if you want more power.

i know they do i was wondering why he thought they didnt. how much did yours run btw? i think mine's starting to go

videos i found on youtube. (zetec engines)
http://youtube.com/watch?v=cNWpa_TtRA8
http://youtube.com/watch?v=arNr9meGfqw

The TPS i was just going to fab a bracket to use the stock tps like suggested. I know the stock flange is a bad idea but im using it untill i get the rest of it built. When i know its built and it will fit ill finish the flange with an aluminum piece.

Adding a plenum doesn't take away from ITBs, every high performance bike that uses ITBs uses an air box around them. BMWs have ITBs with ............an air box around them. Open wheel racers, even F1 cars use ITBs with big air boxes. Its FUNDAMENTALLY beneficial to have an air box or large plenum because it acts as a large air holding tank for the ITBs to draw from. It is important to have the plenum large enough to allow the resonance tuning to disperse inside the plenum without bouncing around inside to cause negative harmonics for the other runners. This is why those crotch rockets have a 1000cc engine with a 6000cc air box. The rough formula is 4 times the diameter of the intake runner/velocity stack. So a 4 or 5 inch diameter plenum would offer enough room if the runners open on one edge. I wasnt looking for people to tell me why they think I cant do this, I was looking for issues with the stock TUNING. I dont wan't this to work only to throw my a/f ratio off so much that I lean out and dmg the engine. So, I guess I'm wondering is how far the stock ECU can "learn" and what its limits are.

I think the main benefit of not using an airbox is being able to use venturis, which probably result in better numbers than the airbox.

Personally if I was going to use a box on ITBs, I'd use a turbo, too. [hihi] Granted it's more complicated, but the point is to be able to fine-tune everything to get the most out of the engine. Coil-on-plug would be mandatory, in my opinion, so you can fine tune all aspects of each cylinder.

Look around, there are ITB set-ups out there for Foci. The caterham comes with them.

I think the main benefit of not using an airbox is being able to use venturis, which probably result in better numbers than the airbox.

Personally if I was going to use a box on ITBs, I'd use a turbo, too. [hihi] Granted it's more complicated, but the point is to be able to fine-tune everything to get the most out of the engine. Coil-on-plug would be mandatory, in my opinion, so you can fine tune all aspects of each cylinder.

I agree completely that velocity stacks are a must with ITBs, my plan includes curved velocity stacks with the bell being just inside the edge of the plenum. Id love a turbo, on my last car I built my own custom turbo kit for my V6 probe and I so miss the power that car had. Ive been thinking about turboing the SVTF as I have a spare turbo and intercooler laying around along with some intercooler piping, but im getting off track. I was doing some measuring today and I'll have more room than I thought I would. Turning the runners down like the stock manifold yields quite a bit of space. I wanted to curve up but too many clearance issues and nearly as much room. Todays my B-day and ill be getting some cash from my family/brothers on sunday which will kick start my project. Cant wait to get started!

This is why those crotch rockets have a 1000cc engine with a 6000cc air box. The rough formula is 4 times the diameter of the intake runner/velocity stack. So a 4 or 5 inch diameter plenum would offer enough room if the runners open on one edge.


Assuming you just phrased this wrong.


This will be the problem you will have to overcome.
If you are going to use a plenum, it will have to be large, roughly 250ci, for the harmonics to not interfere, and it will have to function more as a hood than an actual plenum, i.e. no throttle body at the opening. Now that is going to create a problem with metering the incoming air. At idle it will be almost stagnant and the MAFS will read very little if any G/sec. To overcome that you'd have to put another TB on the opening of the plenum, but that will change the harmonics.
Pretty much the ideal plenum should have no state of vacuum in it, using a TB on the end negates that.

This is more the kind of feedback I was looking for. I was going to use an open-ended plenum, balancing the stagnant airflow vs unwanted harmonics will be a problem. What I meant before about the spacing was that you want at least 4 times the diameter of the runner before you hit anything. Example: the runner is 40mm, you would want at least 160mm of space before it hits anything. I guess the question is, would having enough vacuum to use the maf be enough turbulence to ruin the resonance effect? I think the main effect would be to throttle response, because once the air gets going it would smooth out flow across the maf. Its a good point, I'll have to ponder this with my ole man. He's been an engineer for Ford for 27 years and has designed more than a few intake manifolds. Thanks for the feedback.

You guys need to go read up on manifolds.... for optimum sizing if you have 2 liters of displacement you need 3 liters of plemium... its 1.5 times your displacement not 4 or 6.

You also need to look at runner length... most ITB's have extremely short runners, which do give you top end power.... but down low even old stock Honda's will have more TQ than you.

Well, I was quoted an article about F1 engines so it wasn't too much in context I suppose. Im planing on keeping the runners as long as possible to keep torque up, around 17inches from valve to venturi. Not sure if I'll get that long but 14" looks doable for sure. Thanks for the info.

You guys need to go read up on manifolds.... for optimum sizing if you have 2 liters of displacement you need 3 liters of plemium... its 1.5 times your displacement not 4 or 6.

You also need to look at runner length... most ITB's have extremely short runners, which do give you top end power.... but down low even old stock Honda's will have more TQ than you.

Yep, and peaky powerbands aren't usually all that great on the street either. Driveability will suffer pretty drastically UNLESS you can change the gearing substantially to offset the low end torque loss. Also, keep in mind peak power will be made MUCH higher than what the engine was designed for and you will have to make a few other changes to keep the engine together.

I wouldn't even consider doing ITBs on the Focus because there are too many other ways to improve performance while staying within the design limits of the engine and drivetrain. You will be very dissapointed with the results *if* you don't or can't make other engine/drivetrain changes.

Not considering ITBs is just fighting progress, IMO. [;)]

I have to admit, I still can't grasp why longer runners = more torque. Still learning.

Not considering ITBs is just fighting progress, IMO. [;)]

I have to admit, I still can't grasp why longer runners = more torque. Still learning.

It's all about air speed/velocity at a given rpm. Just being "longer" isn't always right either. Most of the time the inner diameter of the runners are smaller too.

You can only cram so much air into a motor at low engine speeds.

With a four stroke engine, there are four events that happen. I would suggest doing some reading on the gasoline combustion engine and how the four "strokes" (and changing them) effects a powerband. Then you will have a much better understanding on how intake runner length and size effect the powerband and torque charactoristics of a motor.

I would do it, but it's late (after 1am) and I'm going to bed.... [sleeping]

[:)]

I know the basics, but not the engineering.

I honestly dont think the low end torque will suffer. With an intake runner of 14-17" thats as long or longer than the stock even when its on the long runners. With a length of 17" the peak power is at 7000, same as stock only you have 3 other resonance points down throughout the power band. The only place I see the stock manifold being competitive is from idle to 2-2.5k rpms, after that I think ITBs will win out and the top end wont even be close.

I'm glad you feel like that........

ITB's will GREATLY suffer low end torque loss.... go to the Focus Power Forum and look at the dyno of the ITB setup they dyno'd last month... you can physically see the torque curve drop off then come back later on in the rpm's.

Here is the dyno... notice how the torque is effected from start all the way to 4500rpms.... thats where you LOSE races.

http://img.photobucket.com/albums/v683/1turbofocus/NAZX37.jpg

yikes even I have more torque than that thing below 4000.... [poke]

And that was with Tom tuning it, I asked about the low end... he said he tried to tune it out but thats one of the draw backs of ITB's

I"ve done a good bit of work with Webers ( carbs for you young folks)... They are basically mechanical ITB's... TRUST ME, you low end usually suffers, but they work great on road race vehicles, they can make mad power at High RPMS . Thats the trade off.

Here is the dyno... notice how the torque is effected from start all the way to 4500rpms.... thats where you LOSE races.


I see what you're saying, but I would hope someone who's racing would keep an SVT above 4k. [burnout]

I bet if you ask Tom how long the runner length was it was very short. The few setups ive seen is with the runners coming straight out and stoping, the total length is like 10-12 inches. So with a setup like that yeah of course low end torque is going to suffer, thats like running the stock manifold only on the high rpm runners. With 12" runners the peak power would be somewhere like 8500rpms.