Technical throttle bodies for FIRE engine

[arc]

why would it have been done, do we know anyone has even attempted to make a high revving 16v?

generally speaking, 8v engines have more low down and 16v are better higher up.. BUT the 8v engine is easier to make rev higher.. but the 16v would benefit more from that.

 

[craigb244]

im sure people have looked into it and just found it cheaper to make a 8valve do the job.

 

[arc]

but like i say, using the 8v for that is a comprimise.. meh, what do i care - i dont want a screaming engine on TBs

 

[Renrut]

Right I've measured the throttles - 37mm right through into the airbox.

Looked at space under the bonnet and took a couple of pics. I'll upload them if I need em.

Its quite deceptive how small they look, yet when you compare them to the 1108 fire the airbox is nearly the size of the block!

Did lots of measuring and offering up and it looks like there are 4 options for me:
1 - forget it.
2 - just fit the throttles and forget about the air box.
3 - fit the throttles downdraft and and have a bulge in the bonnet with holes for the airbox inlets.
4 - rip out the heater and battery which will give more than enough space to fit the whole lot.

Considering the airbox will likely be benefitting from Honda racing development knowledge I suspect 2 won't be a great idea unless I put a lot of effort into making another airbox.
I don't fancy chopping big holes in the bonnet or making it bulge for a single potentially minor power increase. Were I forking out for crazy cams and a money no object engine rebuild then yes I think I could live with it but I'm not. It'll probably get a P75 cam and a bit of head work and aftermarket ecu at some point but not from the off.
I believe the heater is an MOT requirement so pulling that out scuppers road legality unless I can find some sort of dinky heater to replace it inside the cabin.
That only leaves 1

For reference the throttles themselves are 100mm long, 37mm bore, on checking the bore spacing its 74mm not 55! I divided by the wrong number

With the airbox on they're more like a 350mm cube with a corner cut off.

 

[arc]

rip out the heaters and fit a fully electric one, just bung a B&Q fan heater in there. done in minis often isn't Tom? Not the B&Q fan tho

 

[craigb244]

you dont need a heater... just ventilation. (never seen a mot test look at the heaters tho tbh) so basically you can just fit a computer can where the vents are or something.
heating is for girls

dont worry about the airbox... it will be tuned... but not for our engine. the bike engine will rev as something like 15k while ours is only half that

 

[Renrut]

Apparently the particular year of this CBR made peak power around 14,000 rpm. So approx 2x my rev cut. Working a bit of logic into that it should mean ideally I want twice the length from throttle plate to inlet valve compared to the bike and maybe half the size of the airbox. My fluid dynamics knowledge isnt great

I'll read up on how to remove the heater and have a look over pics from people who've already done it as that seems to be the most sensible course of action. I have tons of spare computer fans so no biggy if all I need is outside air ventilation for MOT. And I need an excuse to move the battery to the boot anyway

 

[Brooky]

there should be a picture of mine somewhere without the heater and itb's laid in position

 

[randomizered]

I have looked at solid lifters for the 16v, as has NigelR. It's NOT easy but it is doable, and is something i am looking into.

Ultimate plan for mine is forced, and for that, i want/neet solid lifters. Rember that fiat is making 180bhp from a 1368cc engine though

As for ITB's, I'm looking forward to the results!

 

[fingers99]

I think C&B do them off the shelf. Arc, no real similarity tween the K series (which is more like the 8 valve) and the 1.4 16v Superfire (which is more like an ancient Lancia ) which is where I got the notion of ye olde screw adjuster.

You can bet your life that the car that finished 3rd in the Polski endurance championship and the works rally cars are not running 8 valve heads.

 

[fingers99]

Damn silly thing won't allow me to edit, but:

Here is a 16v hydraulic tappet:

Here is a K series follower converted from hydraulic to mechanical operation:

As you see, the K series is very similar to the old 8v follower (looks even more like the new hydraulic 8 valve follower), but the shim is in the right place.

BTW (and sorry for thread stealing!) great stuff about K Series (including very good bits about porting generally and a link to DIY solid follower conversion) here.

 

[randomizered]

16v hydraulic tappet https://www.fiatforum.com/panda-new/172848-project-has-begun.html?p=1861914 Shimming is the hard part as you have no access al all!

 

[arc]

I think C&B do them off the shelf. Arc, no real similarity tween the K series (which is more like the 8 valve) and the 1.4 16v Superfire (which is more like an ancient Lancia ) which is where I got the notion of ye olde screw adjuster.

it was the T series i was on about BUT looking at them diagrams the T series ones are like the K series, i just took that as the norm on 16v engines of the 2 that i've pulled to bits (T series lump and cosworth lump). Why've fiat done this to us lol

looking at the pics from Kristian, and going off what i remember falling out of the 1242 16v.. they look like the other type, that first pic looks more like what i'd expect the 899cc's rocker gear to look like!

edit; after further reading on guy croft forum.. solid lifters, forget it!

 

[fingers99]

If Kris's pic is right, it's relatively easy -- the shim under bucket style is exactly the way Alfa, Jaguar, et al did it in the good old days. Alfa were right, naturally. They are buggers to shim as you have to remove the cam and bucket every time to swap the shim out, but providing all the clearances are not out..............

Advantage over shim on top of bucket is light weight, by quite a margin. This should really help a high revving engine, reducing stress all along the valve train.

Which leaves me wondering exactly what my pic represents........

 

[randomizered]

But how do you measure the clearance on a superfire 16v engine You have no access once the cam carrier is bolted down

 

[fingers99]

Dunno -- got a pic? Plastiguage, maybe. Or holes in the carrier? Or wierd shaped feeler guages? In all this, it may be that the hydraulics are safe to 10k.

Aha! Dummy cam carrier, machined out of a scrap one?

Give me a six figure sum and I'll try and come up with a desmo head for the damn things -- safe to 12k (pistons, rods and crank willing).

 

[arc]

i have a scrap cam carrier.

 

[pictsidhe]

Those honda ones are too big, the 1600 16v vtec crowd like those...
Theres a few bikes with 32mm TBs, diversion 600, fz6r. my money would be spent on a set of kawasaki ninja 250 TBs, it's a twin fed by 28mm TBs, which seems a reasonable start, you'd need two sets though, that'll be good for over 100hp. The CBR TBs are for a very very revvy motor in a bike, cars need more torque, you'd probably even gain HP due to the increase in gas velocity, even the kawasaki tbs will probably be down on hp. I'm actually searching the forum to see what size small spi fiat tbs are to get hacked up for my 400 ducati engined bike: 50-60hp and 12k redline... I'm after 32mm single body per tb

 

[tpv]

Dont know about the 1108 but the 1242 mpi mani ports are about 30mm.

I think the heads are the same as the bigger engine just has longer stroke