ITB's info/projects

[1991 E30 M42]

http://www.gttechnic.com/catalog.html
about 2/3 of the way down

[steve321]

well it all started about 18 months ago, when i brought a set of E36 M3 evo ITB's off ebay, but had a nightmare when it came to trying to fit them, what did'nt help is that i worked everything out using gaskets and not actually matching the ITBs to the head, (becuase i did'nt want to take my inlet manifold all off in case it all went tits up and did'nt work, lol) so i machined my self an aluminium adapter plate to match the S50 itbs with the M42 head, and that went fairly well, but i was never happy with having the adapter plate, one reason among other was that the ITBs and plenum sat quite high in the engine bay and stoped me from using my strut brace,

heres how i was first going to have the itbs


and heres the aluminium adapter plate


time went by and i had the itbs fitted for about 8-months, then just recently i was browsing through ebay for a cylinder head, and found one for ?30, so i brought it with the intention of practicing headwork on it, and making the itbs fit properly,

heres the main problem with the itbs, the ports are the same size, just dont quite match



so i started to grind out the head and itbs so that they matched each other, that was only about an hours work, with a drill and tungsten carbide bit.

now its a case of bolting them to the head when the bolts do not all line up, you can see in this pic that there very very close, and i did even have to file a small ammount from either end so that the itbs sqeeze in around the studs,


so with most of the obsticles out of the way i got on with making some little brackets up, and very luckily i happened to have some 2" aluminium angle thats about 3-4mm thick so i used that for some little right angle brackets.




 and thats about it really, then got them bolted to the car


its still abit of a mess and needs some more tiding, but slowly getting there, i am working now on the spare cylinder head, the porting is going very well indeed, i am fitting bigger 34mm inlet valves and the inlet and exhaust valve seat/throats are being machined out to the maximum they can be,

 heres some of the head work
before

after




  once all this is done then i will start on the bottom end, making it 2 or 2.1 liter, and a silly high RPM

     steve
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Ecig forum

[romkasponka]

looks very good!

I found this few days ago http://www.homemadeturbo.com/tech_projects/itb/

[Alpine003]

looks very good!

I found this few days ago http://www.homemadeturbo.com/tech_projects/itb/

This is what I did with my Acura 4 years ago. I recently acquired another set of GSX-R ITB's but they are going on the 2002.

IMO, ITB's are only good for track cars that have upgraded cams/headwork and constantly sees above 4000 rpms.

The itb's on the 2002 will more or less be for curiosity sakes and experimental with no intentions of leaving them on in the long run.

It seems that Carbon Fiber and ITB's are so overrated these days and it's usually the wrong people that adds to the hype. :rolleyes:

As for the above poster, definitely an "A" for effort. Curious to know the outcome on whether it was really worth it or not.

[tim_s]

i kinda disagree with the above (ITBs just for track cars). ITBs on my M42 made it have fantastic throttle reponse throughout the rev range, and (ok particularly at high rpms) it really went very well. It was pretty driveable in all conditions, it was the aftermarket ECU that let it down. I could not map megasquirt so that it would drive as well as factory.

My concerns with Steve's setup are how he's going to get MS to run well enough, although Steve's car is mainly a toy, whereas I had to use mine to drive around cities etc.
I will resume hostilities with my setup later in the year if I can pluck up the energy

[Alpine003]

It was pretty driveable in all conditions, it was the aftermarket ECU that let it down. I could not map megasquirt so that it would drive as well as factory.

Your sentence seems confusing saying it was driveable in all conditions but the ecu let it down. :confused:  

The term "driveable" imo is a relative term for everyone. The issue that I have with ITB's is that most of the diy itb's looked niced and performed nice within a certain rev range but as for daily driveability, it was far from optimized.

I'm sure if someone spent enough time on tuning, they could get the driveability and refinement close to a factory tuned M car but I've only seen 5% of ITB cars that exhibited this trait. There is just too much r&d and tuning time involved to get the kind of refined ride that factory cars have for daily street use.

Of course if you're riding around on 800lb/in springs on the streets then ITB's will probably suit you and offer you that good "driveability".

[tim_s]

i said it was 'pretty' driveable, which is probably a term that's used more in the UK. Lots of people have been in my car, and more or less everyone said that i was being really fussy over how it drove, but i didn't really want to accept any compromises. I have to spend quite a lot of time in slow-moving traffic and I could never get megasquirt to respond to IAT properly with MAF, and also i wasn't using the new hi res code and was never happy with the idle. Having said this, when I wasn't living in london, the car drove great, so well the girlfriend could drive it; it was only when I moved to london and had to spend loads of time in traffic that I found the ITBs tiring.
It all depends on definitions I guess. I'd say my car with MS and ITBs drove as nice if not better than factory in most conditions, apart from slow moving traffic and idle, especially when the inlet temps hiked up.
With MS improving all the time, especially the hi res code, and with some more improvements to the ITBs, I may be back with ITBs later on in the year.

[Alpine003]

I'd say my car with MS and ITBs drove as nice if not better than factory in most conditions, apart from slow moving traffic and idle, especially when the inlet temps hiked up.

I would say this is a definition of a street car as most people that live anywhere near a major city will most likely experience some amount of slow moving traffic and idle. Hence, I stand by my original statement that itb's are great for the track.

In my experience, I've noticed diy itb's are easier to tune for steady state cruising or higher rpm operation. Not necessarily the case with lower rpm and rock steady idle.

Are you using a Vacuum canister? If not, I found using one can help with the idle situation of ITB's. Really easy to construct out of PVC pipe, end caps, and some fittings from the hardware store.

As for the lower RPM driveability, I might try to utilize the secondary butterflies of my ITB's on my next project to see if those would make any differences.

[tim_s]

The idle and traffic issues have absolutely nothing to do with the ITBs. I would still have these issues if i were running MS with a single TB.
The idle seems to be due to the (lack of) resolution of msns with the normal code and fairly large injectors, and the traffic temperature problem is due to not fully understanding the relationship of inlet air temperature to the output of my MAF. You simply cannot blame the ITBs for both of these megasquirt issues. Megasquirt is a big undertaking, and is improving all the time; bottom line i've just not been good enough or had the time to get it perfect, especially as I'm running it in an unusual configuration. When I took on megasquirt, I was aware that this was likely to be a big project and that i'd have some small issues. Had I paid a lot more money and had the car properly set up and mapped on a more expensive standalone, I daresay I wouldn't have had those problems. Theoretically traffic and idle were not a problem with ITBs; it was my implementation of MS that caused the issues.

In my experience, I've noticed diy itb's are easier to tune for steady state cruising or higher rpm operation. Not necessarily the case with lower rpm and rock steady idle.

Are you using a Vacuum canister? If not, I found using one can help with the idle situation of ITB's. Really easy to construct out of PVC pipe, end caps, and some fittings from the hardware store

When I was running MAP i experimented with small plenums and with restrictors. I found MAP had more fundamental issues with ITBs than getting a stable vacuum reading. This is why I ran MAF. I've not found ITBs any harder or easier than a single TB to tune for steady cruising or high rpms. In fact especially when using MAP ITBs are really easy to tune at light load and low rpms.

I just don't really see many issues with running ITBs on a daily driver car; the difficult bit imo is getting the management right. Which in a roundabout way i think is similar to what you're saying, but i think its an important distinction.

[Alpine003]

I just don't really see many issues with running ITBs on a daily driver car; the difficult bit imo is getting the management right. Which in a roundabout way i think is similar to what you're saying, but i think its an important distinction.

Yes this is what I'm saying and tuning is obviously the key in making ITB's suitable for the streets if done right. It's just that I haven't seen many able to achieve or put the time into tuning a really refined map on ITB's that can rival the refinement and driveability of factory itb cars. Most usually lack either time or proper knowledge to fully achieve this. Hence why I say that itb's generally belong on the tracks.

That is not to say that no one should be using these on the streets. I would say do what works for them and their situation.

I would easily recommend itb's to a "street car" if by definition, you are riding around in a stripped out interior, 800+ lb/in springs, no a/c, race seat, straight pipe as a street car and are perfectly fine for using it as a daily driver.

[nobrakese36]

So you eliminated the spacer?

[steve321]

yep, dont have it anymore, i did in the end actually need two spacers, there was another 10mm one in between the head and the adapter plate.
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[bmwman91]

Has anyone looked into slide throttles for this instead of butterfly valves?  Although the way they open could lead to odd air flow vortices, and subsequently odd air-fuel mixing, they seem like a pretty neat concept.  I have a lower M42 intake manifold on its way to me, and I hope to make some real design ideas for a sweet new manifold...then I just neet to get my Megasquirt working again!

[dino245]

I put my Hayabusa throttle body adapter up for sale in the clasified section. Check it out.

[Boyracer]

I am not quite sure how essential ITB's are for making big power on M42 :confused:

Honda S2000 makes 120 hp/l and first Integra Type R around 110 hp/l without ITB's, also Ferrari seems to be content running their current engines with one TB per cylinder bank (2 for F420 for example).

So clearly big power (for our cars atleast) can be achieved without ITB's. It is different matter for race cars that need to utilize every advantage they have. But we cannot go that far because of emission regulations anyway.

Why ITB's on BMW M cars then?

I think the reason might be in number of cylinders and driveability. 4 cyl inline engine fires once at 180 degrees of crank rotation and 6 cyl inline once at 120 degrees. So power (and induction) pulses come more often in 6 cyl engine.

Both 4 cyl and 6 cyl engines have common intake system for all cylinders but but with 6 cyl engine the induction pulses are closer together in time and they might overlap meaning there is less air going to cylinders. To avert this you could increase size of STB the cylinders share but that is not good for low speed running.

When you have ITB for each cylinder on 6 cyl engine there is no pulse overlapping between cylinders if the plenum and it's intake are large enough.

At low revs the overlapping intake pulses are not a problem because amount of air is not that great and time between pulses are quite long. But when you start revving the engine higher it is different. 6 cyl inline running at high revs (yes, M3 S5x...) have pulses close to eachother and they can affect eachother if you use STB. Solution is to have ITB's.

4 cyl inline running at *same* revs will have intake pulses further away to eachother and ITB's might not be needed because there is less pulse overlap.

So that's why 4 cyl Honda can run well on high revs without ITB's. And Ferrari V-8 plenum is split in two so it is basically two 4 cyl inlines, one TB per cylinder bank.

Does that make any sense or did I talk utter bollocks?