CA18s and SR20s can make the max restrictor bhp with stock inlet and exhaust manifolds. I reckon you might be getting sidetracked. To me the key to maximising the potential of a 1200cc IPRA turbo is using the 8500-9000rpm you should be able to get through the restrictor. These big manifolds and 2 sets of injectors just look like ballast to me! :P Have you tried a shorter, more conventional looking manifold?

I think the rpm is right on the ball but the manifold is fine for e85 versus oxygen balance at the rate its consumed.

The runners and plenum look to big to me. Whats the inlet port size. Injectors aimed at the valves is the way to go no need for secondaries. Have you posted a spec list on the engine. Throttle body doesn't need to be any bigger then standard ca18. sr20's with 66mm tb can flow engines up to 400kw. Sorry to sound like a sour puss

I understand SR`s and CA`s make max resrtictor hp with standard manifolds. As you know, the A series probably will not using standard manifolds. Custom manifolds have to be made. These manifolds are not big. The exhaust manifold has a runner ID much smaller than the ports(26mm) and the inlet runners have an ID of 40mm, tapering down over the last 150mm to match the larger than standard ports. The problem with more traditional looking manifolds(small plenum and TB at one end) is ensuring even distribution to all cylinders. OEM manufactures spend a lot of time and money getting this right. with custom manifolds the easiest way to ensue even distribution is by having it symetrical with the TB in the middle. Large plenums also help.
I certainly agree that the plenum on this one is too large. But i am confident of fairly even distribution between the cylinders.


Oda, why is having the injectors pointed at the back of the valves the way to go over staged injection? The TB is a lot smaller than 66mm.

Simon, mega interesting read.
What you are saying re the distribution echoes what I was always told, hence the 'log' type manifold with the air getting blasted into the very middle before splitting into the individual runners.
Re the staged injection, I would have thought that pointing at the back of the valves was the way to go too, but would be the 1st to puit my hand up and say that I really don't know that much about it. Could you please enlighten us as to why you feel that this is the way to go?
And finally fantastic work and results. Utterly inspirational to all us 'A' series addics out there and proving beyond doubt what an amazingly versatile little engine they are!
Cheers
Dave

I also agree with you Harry regarding using the extra rpm capabilities of the small capacity.

I`ll have to put a good booton end together for that. This one still has standard pistons. I have another bottom end nearly ready to go together. Still standard rods w 17.45 pin end tho. I have some better pistons that will handle more boost and rpm. I`ll have to change the cam a bit too.
The springs should be good for 8.5-9k.

The 840cc Injectors were already at 80% duty. So the second set will also now give more headroom without having idle mixture issues with huge singles. A lot of books on the subject of injector placement seem to recommend using secondary injectors further from the valve for medium and high loads. According to the books, it helps with mixture quality and helps pull heat from the charge.

This is the first time ive personally done staged. I have tuned them before and seen plenty of top HP race engines with injectors mounted out at the start of the runners.

What I might have to do is two dyno runs, one only using the inners and one only using the outers and compare the results. could be interesting.

Another 1200.com member has already done this test on his Cosworth race engine and it was worth an extra 7-10% in Hp from 5k to 8k on an engine dyno.

I've seen some testing to show that all out naturally aspirated race engines can make more power with injectors outside the inlet's bellmouths, but I haven't seen anything to suggest turbos get any benefit from it. It used to be the way to go back in the 80s for your turbo car though - add an extra injector inthe plenum and a microfueller to controll it at high load. But we've come along way since then. Plenty of very powerful turbo race engines just use a single set of conventionally placed injectors. And in an IPRA restricted turbo setup, where you'll only ever make about 250rwkw through the restrictor, it's simply not neccesary. It can be done easily with a single set of injectors conventionally placed near the port face. The second set of injectors, fuel rail and wiring are just extra weight and complexity, with more potential points of failure or headaches. Imagine if it starts running a bit rough at a race meeting - you've now got a much more complex troubleshooting proceedure reducing the likelihood you'll find the problem when the pressure's on in the rush to make the next race.

I think the same goes for the long manifold. A conventional manifold design half that length (and weight) should be do the job just as well and be easier to work on. You've got an inlet restrictor limiting power, all out manifold designs simply aren't needed to make ~250rwkw with forced induction. Nor are long inlet runners - the 30psi boost will take care of the torque/midrange. But to take advantage of your smaller capacity, you'll need to utilise all the revs you can extract through the restrictor - that's where your advantage is. It should be able to make power to nearly 9000rpm through the 36mm restrictor.

Don't get me wrong, the power your making is very impressive, particularly on stock pistons! But I think the way forward is making power up around 8500 - cam selection and timing, cylinder head etc, rather than getting bogged down in trickier inlet manifold designs and experimental injector placement.
EDIT - I missed your last post while I was typing that. Its no real surprise to see you're already working on a better bottom end to be able to use the revs...

180rwkw makes for a very fast Datsun 1200! And your would be alot lighter than the CA18 powered one I had, so faster again. But the 230rwkw mine made on 1.5bar and avgas was a completely different car compared to the detuned 185rwkw it made on 1bar and pump gas.

All duly noted. I have to get through one more race meeting(island Magic)next week then i can concentrate on the next engine.
Ive taken another 22Kg`s out of the rest of the car since i raced it at Sandown. Ive also improved the brakes heaps. It`ll be interesting to see how close i can get to the fastest interstate U2lts cars/drivers.

i dont know about the short runner will be fine with boost thing, s13 sr20 owners who "upgrade" to a shorter runnered greddy plenum lose heaps of midrange. i thought length was supposed to be good for torque? as for the weight its made out of sheet alloy so it'd be pretty light.

i do like the idea of more revs as the power doesnt seem to taper off. either way i dont know anything like it, its ground breaking stuff!

The idea behind having out board injectors is that the fuel evaporates and soaks heat out of the air. Spraying it at the valve more heat gets drawn out of the cylinder head so your inlet charge is warmer and less dense. How much depends on specifics.

There's a few way to maximise flow through the restrictor. You want the minimum turbulence, no flow separation and the coolest air possible. You also want the smallest boundary layer, which just means the bit of air near the wall that's moving slower. You can take some clues from wind tunnel design. I'm also happy to help.