new injection manifold

[steer from the rear]

right a while ago i made a injection manifold out of steel with a single throttle body and a not very well designed injector angle



then i had cut and re-welded the runners after and it looked a bit of a mess but it was the best i could do with a mig, but now i have a a.c tig i plan on making it in aluminium






so i seen this a while back, a maxi engine fitted with quad throttle body's. what advantage does this have over a single one? and i noticed the injectors are fitted befor the throttle plate. would this work? dont the injectors have to be after the plates?

also im planning on using cbr 600 throttle plates, does any one know the correct size plate per cylinder for a 1400? and am i correct in thinking that i need a 300mm inlet runner from the back of the inlet valve to the plenum chamber?

[Big Jim]

There isn't really a definitive throttle size for an engine. I'm generally of the "big is best" school for minimum pressure drop, but going too big gives you problems with progression and the bigger runners can hurt low speed and off-boost performance. I would say about 34-36mm would be the smallest you'd want to go for a plate-per-cylinder setup, but I personally would go 40.
Runner length again isn't set in stone. 300mm is fine, longer will move your peak torque down, shorter up.

Basically, making stuff like this, your first attempt is an educated (or un-!!) guess which you can then refine later if something is really amiss.

Having the injectors before the throttles will make idle and low speed a nightmare but be good for power. Hence double injector setups with one set in the normal place and another set out in the plenum. Balancing the flow betwen the sets gives you the best of both worlds.

[olidaviesuk]

If you're after a ready made throttle butterfly/injector inlet manifold the nissan pulsar gtir has one on it as standard, off the top of my head has 4 x 38mm butterflies and injectors downstream from the butterflies, but has been 10 years since I had one apart.. is made from alloy, might be easier to find one and modify, rather than start from scratch..

[michael tierney]

throttle boddies will give u better torque off boost but as soon as ur near atmospheric and then on boost theres no gain.they will make a wild cam more drivable low down because the whole manifold will not be subjected to mad pressure fluctuations that happen on overlap!! is this going into a gtturbo?

[steer from the rear]

i was planning on buying some cbr 600 carb set up, pulling the throttle plates and spindles out of them and dropping them into some sort of tube then welding that to the original manifold flanges (unlike the 4mm plate i cut out for the steel maifold flanges) and then making a tidy plenum higher up to go to my charge cooler.
with my turbo not coming in till 300rpm id like any gains to be had lower down the rev range

this is for a turbo 2

[michael tierney]

you could ask mudslinger about his experiences with multi-throttle setups,i'm actually making a manifold for a gt for multi throttles at the mo!

[olidaviesuk]

would save a lot of trouble if it fits or is close... Is pretty much what you're talking about fabricating from scratch...

i was planning on buying some cbr 600 carb set up, pulling the throttle plates and spindles out of them and dropping them into some sort of tube then welding that to the original manifold flanges (unlike the 4mm plate i cut out for the steel maifold flanges) and then making a tidy plenum higher up to go to my charge cooler.
with my turbo not coming in till 300rpm id like any gains to be had lower down the rev range

this is for a turbo 2

[Mudslinger]

its not easy thats for sure , the first route we went down adapting the bike throttles work was asking alot the throttles were cut up so much it was a miracle we actually managed to get it working ,they didnt like the boost that much and pissed fuel , the hardest part is making the seal and designing a plenum thats going to hold the pressure ,i certainly wouldnt advise anyone to do it , then you have the mapping of the thing , its certainly not easy and theres not alot of help out there for mapping mtb's with boost , it takes a bt of time .

using the jenveys upto now seems to be pretty solid although the work involved in getting this to work is immense . but its certainly proving more reliable , albeit the car has had alot of mapping time and there is still room for it to be tweaked abit more

ive added alot of pics to my profile that were probably lost when the old site went down , 1's with the phase1 of the mtb route using the bike bodies


https://www.rtoc.org/boards/album.php?albumid=145

[michael tierney]

did u manage to dampen out the vacuum pulses with filters?i seem to remember this from the last time..ur rolling road results,ect?

[Mudslinger]

im using a bleed valve for now and it seems to be a bit better ,the latest rr print out is in my profile pics

[Woznaldo]

I asked this very same question on the Megasquirt forum and after a bit of heated debate the general consensus was that for 'ultimate power & throttle response', throttle butterfly per cylinder was the way to go but, hugely complicated to get to work correctly.

For 99% of applications, a single throttle body is going to be best because it will make almost as much power & have more than adequate response but, the average joe has a good chance of a DIY installation because it's relatively simple to achieve.

Like already mentioned, if you want to look at a good throttle per cylinder installation turbo set up, then have a good look at the Nissan Sunny/Pulsar GTIR. The only reason Nissan went this route was for homologation for their rally cars.