Good point about overly large throttle bodies, they will have high flow at high revs but will be a killer at low revs as you need turbulent air for good fuel mixing. Another point is get the bodies close to the intake ports because part open throttles produce turbulent air and this is a good thing at low to mid revs. You will need trumpets for the intake side, as long as possible for a road car as this will give good ram affect, short trumpets are good for higher BHP but also at higher RPM so just for race. Don't go mad on ITBs size as you will build an undriveable dog that needs high revs all the time and will be a complete pain to drive everyday. I fitted 2x Triumph triple motorcycle ITBs to my 911 and yes the noise and the throttle response are awesome.
Bill, all good points. In fact I am currently running the "don't use too large throttle bodies" as a cautionary tale cus these are definitely too big (as are the injectors!). I bet a flat 6 barking through 6 ITBs does sounds awesome....
nice.... I adapted two sets of Hyabusa throttle bodies (off eBay) to a Ferrari 308QV (bought at a Ferrari breaker) that I'm putting in my Lancia Stratos Replica Easy peasy manifold fab. Each bank uses a Datsun 240Z air box. They Hyabusa ITBs are fitted with Honda S2000 injectors.
according to Jenvey the ideal length from valve seat to butterfly is around 200mm... the overall length (including velocity stacks) varies depending on tuned port length/cams/where you want peak power etc., so... it's very true that bolt on ITB kits may or may not make any more power...
Very interesting, thank you! Interesting how some motors with ITBs have actively adjustable velocity stacks as well that adjust the length depending on RPM.
The noise! Lol This is a great discussion. Ive been putting itb on my single cam honda. Power drops when the engine is stock. I change to 12.5 comp piston, and time the cam perfectly. Some tune on the link g4 later, a whole world difference.
Excellent comment! Really shows that ITBs don’t just add power, they can be used to great effect but everything has to work with them.... are you running a standard cam with 12.5 compression? That’s fairly aggressive... 👍👍👍
@@MakingforMotorsport stock cam. Just lock the vtec on the high lobe all the time. 12.5 is fairly normal in where i live since we got ron97 gas available at the station. Just dont get too attached to those people on the internet and forum telling u what to do or what not to do. Experiment it yourself.
If you are on the high cam that makes more sense, even with 97 you’d have to be careful with detonation at low revs high loads with a very mild cam shaft. I can’t fault you for getting stuck in and having ago, my methodology exactly! I am planning on bumping my compression once the throttle bodies are on!
Sorry late to the game... Main advantage is the reduction in pumping losses, making the engine more efficient... Yes you can tune the runner length but you will want the throttles as close as possible to the head... Also, placing the injector farther away, say at the bell of the runner, will give more time to mix and provide a cooing of the inlet charge, making it more dense. Problem as I see it is how to monitor the Manifold Air Pressure? Or are you going to utilize a mass air flow sensor on a common air inlet?
ITB tuning is usually alpha-N so throttle position is used for the load axis of the tables MAP sampled from a vaccum distribution block fed from each throttle body is good for 0-20ish% throttle position after that the pressure the other side of the throttle plate is basically atmospheric
Awesome video. Thank you so much. Numptys like me need this sort of stuff 🤣🤣. Spent most of the weekend trying to get my head around this subject and hadn't really got there. Feeling like I have a much better grasp of this now. Really wish I'd found the video at the start of the weekend though. It's really nice to see high quality content coming out of the UK and not the USA for a change.
One thing you can do with itb is leave the throttles close to the intake port but extend the runner length to something more reasonable for most engines. Very short runners are usually only effective with high rpm engines with large cams.
Thanks for the ITB lesson; very informative. I mainly deal with carbs, but you never know for the future; will be checking your application out further.
Thanks for watching, I like carbs for the simplicity, back with the a series i had a points dizzy... just fuel and 12v and it’d run, perfect for out on events! I have just looked at your channel, I love a MIdget!
Great video! I've got Jenvey individual throttle bodies on my 1600 Eunos Roadster ( videos on my channel) and I love the character and response they give
ITBs just make that BRARP!!!! Just watched your fly-by video, sounds sweet. The bit I love, ain’t just 8000rpm it is the just off idle barble they give.... nothing better! Thanks for the comment and watch!
great video, want to put ITB on my mk1 focus but obviously to buy ready made kits are £££. one thing is what happens when it comes to the air flow measurement?
But Mike Costin never said - “don’t worry about it, slap some motorbike throttle bodies on!” Either way… turbos, for all the “whoooosing” and “psshhhhtting” will never match up to a good honest “BRARRRP!!!” And I am sure Mike and Keith would agree!
Just bought the speeduino and was looking for options of throttle bodies for a aircooled vw and here i am. Now im looking for a cb 600f itb, complete set is cheaper than anything else, and looks amazing, must sound too.
Good video👍 however your fueling and injector timing. The fuel does not spray as the intake valve opens. On port injection the injectors spray on the exhaust stroke before the intake stroke. Using the heat to help atomize the fuel. Granted @ 5800 RPM this is happening very quickly and the Fuel is being mixed with air velocity. I just wanted to clarify this for those inspired to enter PCM tuning.
It’s a good point, certainly on sequential injection and at low revs it’s onto a closed valve. But as you say, at any kind of high revs the fuel is coming in throughout the cycle…
I bet that a set ITB would sound great on a Turbocharged 5.3L LS truck engine that tops out at 6000rpm but is built for and has loads of low end torque.
Hello, very nicely expland! Thanks. I also want to try those itb's on my golf mk1 16v PL motor. I can also buy a set from a Honda CBR 600 RR. Do you now if those are any good? Gr
The 600RRs might be a little small for you, a decent valver golf should be pulling 120-130bhp you might find the limit for absolute power… that said drivability will be better with them in the small side.
Hey ! It's been sometime I wanted to do an ITB build. Loooove them noises .. And I have a spare VR5 VW engine ( Since I swapped in VR6 ) I want ITB convert it with ported head , higher CR , cams , stronger valvetrain and so on for ESPECIALLY beatiful BRAAAP noises. Buuut , now comes the problem of there being 5 cylinders instead of 1--4. How would you go about it , any ideas ? Thanks !
Hi mate. Currently looking at Atpower 55m ITB's for my honda k24 hi comp motor, it has big cams 12.5.1 comp pistons ported head oversize 1.2mm but stock valves. Currently makes 305hp but want to switch to individual throttle boddies... was planning on going a 55mm itb with long runner lengths 130mm. The car is used on the road and tracked regularly. I want the car to drive as good as possible and Idealy not loose any hp, main reason is the noise but I want to optimise it where I can. Not sure if they are to big as can't seem to find to much info for ppl running them. Any advice or info would be great thanks dan
Thanks, glad you enjoyed it! I'm just working on the follow up now, got a couple of bits and pieces videos coming but they all support the fitting of the these throttle bodies!
Good man, welcome to the club! The throttle bodies will be replacing 600cc carbs on my mini Autotest car... at wide open throttle the mixture is okay but it ran really lean at idle and part throttle. I drilled the main jet out to 1.5mm but could’ve gone to 1.6mm. Best of luck for your project!
Hi mate! Been looking at these ITB video's for a while now and trying to figure out all separate pieces before I go and order all the parts to update my BMW M10 engine from an old carb to EFI with ITB's. Initially I wanted to go for a 2000 euro kit, but seeing your video's I want to give bike throttle bodies a go 😀Now a lot is clear, however, I'm currently looking at fuel pressure. Normally when looking at the fuel system, I expect a high pressure fuel pump, a fuel rail and after the fuel rail a fuel pressure regulator and the return line. Now for these bike ITB's it's a bit tricky to see where the fuel returns. Now at your throttle body I see what looks like a dedicated fuel pressure regulator on the rails. But I'm not sure. On lots of other throttle bodies, I only see a feed, but no return. Can you maybe briefly explain how you regulate your fuel pressure on your fuel rail? I'd appreciate it greatly! Thanks mate :)
The fuel rails come in two flavours, open ended with a reg or dead ended. The dead ended ones usually have a T-piece on the inlet and require an additional fuel regulator which goes on one leg of the “T”, the fuel inlet from the pump goes on the other.
I have a question, I have a fleet of trucks, in my country the fuel is ridiculously expensive, with a good tune I might have some advantage in putting ITB in order to save fuel? increasing the economy by 1 km/l would already be great
Hi there, as you say truck I automatically assume they are diesel ones, that is a curious fact because i haven't ever seen any diesel vehicles with ITBs... The injection is done directly to the cylinder so as some modern vehicles. So it might work! If it's a gasoline fleet, it may be worth checking if the fuel savings are that much so it compensates the investment
Hi there, hope u doin well, thanks for the video good learning. Just wanna know something I drive a 2005 Mk 5 Golf GTI 2.0T FSI, can ITB'S be fitted to my car or are they not for turbo charged cars?
Hi, that’s for watching. You can fit ITBs to a turbo’d car but it’s not often done, there are minimal benefits for airflow (because you have a turbo), and the throttle response won’t be great because you will be waiting for the turbo to come on boost and finally it can get complicated with ecu. It can be done but I wouldn’t bother... (hope this helps)
so if i'm doing cams, downpipe and a tune on my car, with a pod intake, straight pipe exhaust and some slightly bigger injectors would you consider this a good idea
Hello, these look like CBR1000 Throttle bodies, im going to be using these on my car, can you tell me what size the banjo fitting is on the fuel rail that you have
Each throttle body of a BBC’s ITB is 50mm. That’s equal to 400mm. A Fitech EFI system has 1 throttle body @ 102mm. ITBs flow 3.92x more air. Perhaps ITBs’ should have 12.75mm throttle bodies.
Even I don’t follow that maths I’m afraid! It’s a simple fact that per square mm of cross sectional area, ITBs flow less air, but the proximity to the engine and the single inlet tract per cylinder have their own benefits.
@@MakingforMotorsport Does “flow less” mean less volume but more velocity? I’m trying to figure out why the ITBs are sensitive to throttle changes from idle to half throttle but after 1/2 throttle there is hardly any change. That’s just from what I’ve learned from social media. The analogy I can give is that ITBs are like comparing a 2 stroke to a 4 stroke engine. I’m also wondering what an o2 sensor at each primary exhaust shows on an ITBs system. I’ve yet to find an ECU that has that capability.
a mm per horsepower for that cylinder is a terrible rule of thumb because the area gets exponentially bigger with each mm increase. you wouldnt use 75mm bodies on a 300hp 4 cylinder... just gotta be big enough to give your CFM requirements
I mean, most rules of thumb aren’t totally accurate, and (it been a while but) I think I mentioned this falls down at higher diameters, but at least your not gonna under size them 😂
what if your car is direct injection ? you basically just don't use the injector part of this solution or you swap for a port injection and leave the Directo injection useless?
Hmmm… so whilst there stand-alones out there that can handle direct injection speeduino isn’t one of them. Personally, it’s not something I know about but, having a total guess, I suppose you could just not use them, but a care point might be that injectors might need be cooled by the fuel going through them, maybe not???
@@MakingforMotorsport very god point on cooling the inejctors, makes a lot of sense. Ok, would it possible to use the original ecu? in that case I could use the original GDI injectors . My car is a 2.2 4cil, gasoline (gdi) ... alfa romeo 159 2008 selespeed.
Absolutely, no reason why not, it’s an engine and it works in the same way as all the rest do. 1 piece to be careful of is what else your more modern ecu does, some of them control alternators, dashboards etc, but that should be simple to find with some research…
Ive got a question i have a p71 starlet swapped 4efe and i really want itbs for it is it difficult to built them my own and make them work i bought a cbr600 bike thing or something
@@MakingforMotorsport then its similar to the Engine that I am going to efi convert with Speeduino and Itb's unless I can get a Manta/Ascona efi plenum setup, going to have to scour the scrap yards
Normally you run throttle bodies with an Ecu which just uses AlphaN which is throttle angle based, but you can run also run speed density (which uses Manifold absolute pressure sensor) mixed with AlphaN. There is no reason that you can’t use a MAF sensor but you’ll need a plenum to make sure that all the air the ITBs let into the engine comes through the MAF so it is correctly metered.
I feel like you got all this information from the Jenvey website. And I think their throttle body sizing is some hot bullshit to sell more stuff (I feel like they want to prevent the exact thing you are doing). For example they recommend 50mm for 65hp which is strange since a honda b16 has one 58mm throttle body and 160hp.
I don’t know what it says on the Jenvey site but, the information has been the same ever since people have been running DCOEs. Twin 40s have been on cars for years (as carbs tho these have the Venturi inside which narrows), but if you wanted 160+ out of your pinto you’d be on 45s. My comments about 1mm/hp was clearly a rule of thumb, as it’s more about area not diameter and area has a square relationship to diameter, that’s why an LS engine can put out 600bhp+ on 1 throttle of 76mm. ITBs don’t behave like a plenum installation, and truthfully most have much more flow than is needed, but that’s what it’s about, not being a restriction and tuning everything precisely, and ITBs let you get everything, just right. 👍
@@MakingforMotorsport I wish you could have cited some sources to your information! Little math to where I am coming from 4x 45mm Throttle body area = 6361.72 1x 60mm Throttle body area = 2827.43 (Used on 240bhp honda f22c1) And I dont think the two extra throttle plates will even remotely make up for that.
I did some maths but edited it out as it’s hard to decide where to pitch the standard. To get alittle more scientific, flow doesn’t scale linearly even with cross sectional area, more throttle bodies mean more spindles, more restriction, more separate paths means more wall/area with also slows flow proportionally (more wall means more boundary layer which also means slower flow), so there are many reasons why it’s not a linear relationship, why a single body has bigger flows than ITBs than you would expect from just looking at diameter or cross sectional area. I didn’t do experiment science as I’m not equipped to, but I do plan to get more scientific in the future (this was my 2nd proper video I think)
I completely agree, 40mm ITBs would be more than adequate for 160bhp, which is what I say in the video (1mm of diameter/cyl hp). If you are referring to my earlier comment about 160bhp out of a pinto, this is a SOHC old engine and the 45s I was referring to were DCOE carbs, which would have a 40mm choke to generate the Venturini effect required for carbs to work. I could’ve put all of this into the video, but I didn’t (and did deliberate about it). Long and the short of it, ITBs aren’t easy power and can wreck an engines drivability if not thought about properly... that’s all I was trying to get across. 👍
@@MakingforMotorsport the engine is still in the build process, but it is a Honda D14A3 with a D16Y8 cylinder head, compression ratio is 14:1 and max rpm around 11500... so mathematically it should make between 320 and 380hp.... And it will run on pumpgas but its 102 octane
Wow! Well that is quite the engine! 320bhp from 1400cc is F1 levels of specific BHP! It may have been the other video but I did mention that as you go up in size you get more BHP/mm (it’s obviously about area not diameter). But your engine is a special case I think! What are you planning on doing with it??
@@MakingforMotorsport racecar, full on endurance racecar, but as light as possible, something like 800kg in a Honda civic with over 300hp is more than enough for over 300kph and wheelspunn for days without a programmed TC
@@MakingforMotorsport i will obviously also try to run in on ethanol and methanol too, to see how much i could gain trough drastically the quality of fuel
