ITB + manifold build

But with fluid dynamics it will still pulse down the 6mm tube, on a summers day, you close a door hard in a house and the rooms with a window open the doors slam shut too. I hate analogies...

If people do it on Jenveys does it make it right? do Jenveys link like that when you buy them? have a look at the ITB porn thread and see if you spot many of the motorsport ones linked, the homebrews maybe. Anyway as said your build was great and has inspired me and propbably numerous people all over, i particularly liked you testing the trumpet lengths.

 

The gsxr itbs come with small spigot vacuum take offs on each tb anyway. They are all linked and are connected too a pressure switch iirc as std. Possibly a fuel pump cut off or similar.
These spigots are also used for balancing the tbs. The hole diameter is very small 2mm max, but they are still connected and linked to one another.

 

They are on the bike, but you dont have to link them

 

I know you don't have to link them, but they are linked when fitted to the bike, this means there is a small amount of communication between the port runners. Possibly the small orifice of the vacuum stubs is enough of a restriction (as Sambo hinted) that it does not cause any issue when the throttles are open.

 

Sambo was talking about 6mm ID pipe to the injector holes. A bit of difference in size to the vacuum take of pipes.

How do you think the 6mm pipe would effect the air flow? and is there any need to link them? A take off on one cylinder is quite sufficient for brake vacuum. Why dont motorsport teams link theirs?

Might need a thread split...

 

One thing i learned out of these few posts is a distinct feeling that i miss my ITB-ed valver greatly!

God i love the noise....

Maybee Jools will honour us with testing it both ways just for the research purposes?

 

Tis hijack season! I am sure it will get cleaned up if need be.
Still relevant for the gsxr tbs though.

For sure a larger diameter hose will flow more, however if it is only connected to a servo which is a dead end.
These pipes are all linked to the closed side of the butterflies so it is not as if it is a gaping hole to the atmosphere. A lot of carb installations use a balance pipe between runners to smooth out pulsing, possibly for dizzy vac advance.
I think getting in to the area of inlet pulse tuning, valve overlap cylinder scavenging and exhaust reversion is probably a little too complex for the likes of us.

 

Agreed, what are these c*rbs you speak of? They are hardly the way of extracting potential from an engine for all throttle openings, are they! (new thread hijack) which is tossed to one side - i feel dirty just mentioning their name...

I agree about the complexities of the dynamics of the air flow and hence I why look to people (for gidence) who have studied it, tested it and raced it...

Talent imitates genius steals ideas.

 

Sad as it is on a Friday night, I just pulled out a couple of sets of gsxr tbs to look at.

It would appear the small vacuum take offs that are linked go to a map sensor. This could be for assisting in controlling the secondary butterflies that are used to damp the airflow when the main throttle plates are opened. Did your tbs have this secondary shaft?
They are a great bit of kit for the price though. Lightweight, super fine balance adjustment, tps, cable linkage, the list goes on.

Carbs have there place though, no electronics to fall over and contrary to popular myths banded about, they are very adjustable.

 

Mwhahahahahahahahahahahahahahahahahahahahaha

Im building an Ikea sofa ATM but today was using the laser cutter at work to make some backing plates for my carbon trumpets...runs back to the kitchen to have a look at the fit.

 

Only downside to Gsxr bodies, as well as most other bike bodies, is butterfly angle in closed position

Its alot steeper then average car engine bodies so for small throttle openings you get lots of airflow, very dificult to map acuratelly and can leave flat/lean/rich spots

By the way nothing wrong in getting a set of bods out of cupboard for a good look!

They are very nicely engineerd indeed

 

Laser cutter...... mmmmmmmmmm

 

Yep it is not ideal, but with a good SEM easy enough to map out, also is best to give the throttle pedal a longer throw, bikes ITB's have the small movement due to hand throttles.

Must say i never tire of the noise, and im missing mine too... cannot wait until im better and and can finish the damn things off...again.

CNC mill yummmmmmmmmmmmmmmmmmmmmmm. Manifold looks greart OP, just remmeber the bonnet clearnece, and its best to have a good length inlet track.

 

I see your mis-quote conveniently left out the efi failings.

Spare fuel pump and a screwdriver will mean my car will keep running.
If someone bothered to put half as much effort into setting up their carbs as it takes to install and map an efi system, they would have a pretty well sorted fuelling system.
If bothered about having immaculate driveability and fuel economy fitting itbs or carbs should not really be considered in the first place.

 

I must agree when EFI has wobbly its game over, but at least my car doesn't smell of fuel (from old pump). And ADCA and AA cover has me sorted if/ever that day were to come. Good wiring, good ECU and components and you should not have issues for a long long time.

See hotgolf and his threads. It has been done.

 

I agree with the quality of the install will determine the reliability of the car.
if the wiring is gash then your going to encounter issues, the same as IMO that if you use silicone tubing to join carbs/bodies to manifold you will encounter issues in the furture.
will upload some pics of progress soon, i've been making brackets to hold the bodies on. And have made fuel rail mounts.

 

I agree with about the tubing, i have seen some gash manifolds that rely on the silicone to hold the ITB's/carbs in place over a large length of hose, this will work loose after a time. You can use silcone to good effect IMO, I made mine so that the ITB's butt up to the manifold and are held in place with brackets - no gap between them. The silicone then is used to make an air tight seal around this butt joint.

I like the way you are aproaching it and using the tools/equipment you have at your disposal. Looks quality so far and im looking forward to seeing your brackets.

I have been thinking long and hard about ITB's and what i would/will do differently in the future. The way i would now mount the ITB's would be 90deg in rotation so that the butterfly lines up with the knife edge of the head. A bracket above and below could be used to join the ITB's together - simply use a bolt through the three rods to join up. Then you would need to make the throttle mechanism, I would use ball joints and ali tabs onto the spindles - throw away all the current mech. A bit like the F3 ITB's.

Something like this:

 

i can confirm to u that no matter what management u run u will get weak/rich areas of the map with gsxr bodies, the only way around is running very rich around 2% opening,

not ideal but prevents it stuttering

I'm running with a motec m600 in full sequential with pencil coils, spent around 20 hours with different setups and still cannot get over the issue, I'm looking into a work around but still doing development,

I'm running mine vacuum linked and have had no issues with it (in fact using silicone joins too)
been like this for years and will quite happily run close to 200hp,

if u want to have a nose i will be hacking around bedford with it Saturday,

 

Do you have any dyno prints with the AFR readings on to see this in detail?

 

no i dont , i never used a dyno with this setup its all road tuned,

when i map big hp cars i use a dyno, but this is only my track hack,

i have some datalogs from my dl1 around, but thats only from track