DOHC EFI modification underway
 

Made the big step tonight and cut straight through the middle of the EFI inlet manifold. I'm trying to mcguiver a plenum EFI up so that it will sit same height as the engine or even lower. First step it to get the inlet riser milled flat, 80mm from the base of the manifold

Could have completly balls'd my engine up but what the heck nothing ventured, nothing gained, I'll post up some pics of progress on Monday
Rapid:o

I know that people have modified the Pinto EFI and that some have made simple plenums for the Zetec soooo you should OK, you may loose a little flow but will gain it back with a K&N and a cold air feed.

Hi Rapid,
I'm gonna follow you're modifications, i've got an effi too. :D
Good luck !
W.

That's what I did, I know its on a Pinto but the theory is the same. Been on the road 5 years with 18k on the clock

I did an extensive 'how to' pdf on how to do it but its too big to upload on this forum

Hi Mister Trophy !
Maybe you can post a link were we can download the "how to do" pdf ?
Sounds very interesting i :D
W.

I could email it to you...

Send you PM.

Thx,

W.

Copies sent to multiple recipients - hope they help

Mark

Sorry for the lack of progress folks, new job and holidays etc.

I've now finished cutting the manifold, managed to line the riser up best I could then tried to get someone to TIG it up for me... tried quite a few places but they refused as they didn't want the responsibility of screwing it up, even though I said just go for it?!?

In the end I got introduced to Chemical Metal, this stuff is awesome. You can buy it from alfhords for a reasonable 11.99 for 900g. I was sceptical at first but a mate has used it on a rstor he had done a few years ago and it's still holding strong.

I bonded the 2 half together and now am in the process of just filing it back to look like a sensible shape. I'll then finish it with plasticote black wrinkle finish.

I've bolted it up to the engine and fired her up without any trouble and sounded fine. All in all I think I've taken about 40mm out of the height

pictures attached

Matt

Rapidtornado - Just a word of warning - be very careful with chemical metal. We used to use it to plug empty holes in throttle bodies. However one day, one of our engines started running badly on the dyno. Compression test showed one cylinder was 'ill' on stripping the head off I found a small pellet of something hard, a bent valve and a 'ding' in the top of the piston. After some head scratching and seraching we realised that the pellet was chemical metal that had previously filled one of the holes in the TBs. It had been in there for a couple of years on various engines. After that we always made aluminiun plugs and pressed them into the holes.

OK, thanks for the heads up. My intention is to use thios to get me through the IVA then very shortly after sitch to a zetec, but good to know.

Thanks
Matt

Fantastic work! Im working on my rb25det manifold atm modding it from a top feed to a gtr side feed. Loads of work and like you need to get it tig'd... just need to do some practice welding on some cast ally before i start anything!

You know what this has inspired me to do it this weekend! nice one mate :D

A very timely thread, I am going through a similar process with mine at the moment. I tried to cut one manifold down and duraweld an ally box on to it, that went badly wrong as I could not get enough heat in to the job. I have since acquired a manifold off a Galaxy - it goes down instead of up. I don't think it is going to work though as on the galaxy the manifold incorporates the injector ports, whereas in the sierra the ports are built in to the head. This all means that the galaxy manifold won't seal to the Sierra head. Also the throttle body is different and the manifold has an awful lot of holes in it that need to be filled. I have thought of loads of ways of doing the job but am still nowhere with it. I am having another look at the galaxy manifold today, that chemical metal may be the answer to fill the inlet ports and then reshape them.
Best to all,
Enoch

I recall seeing an ad for a product called Lumiweld i think that was used for these sort of things.Think it was in a car or bike mag :confused:

Took a couple of pics to show what im going to do with the gtr plenum and rb25 manifold. the ports on the injector manifold are in a "C" shape but the plenum is in a nice straight line. I think with any kind of manifold mod its important to make sure the air flow is nice and smooth. So what i decided to do is make a set of plates to weld to the injector manifold that will line up with plenum. Then grind down the inside of the manifold to make sure there is a nice flow basicaly porting it.
Im not keen on using those metal glue type things as you really dont want stuff getting inside the engine. Also in the future you might want to turbo the engine and in that case it might blow bits off... well you never know! heh
Anyhow hope that helps you a little.

nice work there.... would be interested to see it when it's finished:cool:

Bought a pot of that chemical metal today and glued a few bits together with it to see how good it was. After it passed the "pull test", the "hit with a hammer test", the "fill it with petrol and leave it for 2 hours to see if it weakens test" and the "heat it up with a blow torch and hit it again" test I can confirm that it is, in technical terms, the mutt's nuts:D Very impressive stuff indeed. I have since taken my manifold off the car, cut it down and glued on the metal box I had previously made and abandoned. It is looking pretty damn good and for the first time I think I am going to get a manifold I will be happy with.
So thanks millions for the top tip, i will take some photos when it is done. It will sit well below the top of the engine now, the throttle body will exit from the rear of the manifold, the air intake will sit between the manifold and the side panel.
Best to all,
Enoch

Sweet nice work. Nice to know that stuff is rock solid! I will probably have some uses for it in my build :D

I have now got a manifold I am very happy with, it is test fitted in to the engine bay to make double sure everything fits without any problems. I will have to undo my engine loom a bit as three or four sensors are now in a different place but that's only 10 minute's work.
Thanks again to Matt for bringing Chemical Metal to my attention, I had almost given up! I would strongly recommend this to others, it's great stuff to work with and files / sands well while giving an amazingly strong bond to roughened alli.

nice work that looks fab!

nice work there mate, that's looks like a proper jobbie... good effort!!:cool:

Hi Enoch, whats the internal diameter of that hose between the filter and manifold?

Hi Deezee, don't know is the short answer :-)
The flexible pipe is the one off the Sierra, the rigid pipe is a bit of drain pipe, I think it is 2 1/2 inches diameter, I will measure it when I get back later today. It is larger in diameter than the point at which the throttle body connects to the inlet, I figured if I kept everything bigger than the original Sierra I should not have a problem with it being restrictive. Hope that makes sense??
Enoch

Thats a fair point. I'm trying to get some info together for the diameter of my inlet manifold on my 16v version of the DOHC. In theory it should only need to be around 65mm (2 1/2") but it seems a little small considering each carb has a 38mm choke in it. I suppose only one cylinder is drawing in air at anyone time though.

Quite. If you look at the cross sectional area of the inlet ports on the head they are actually quite small. The area of the point where the manifold meets the throttle body is a lot less than 2 1/2 diameter. I think I may have made my inlet "box" too big, I think it may have been better with a similar volume to the original but as I am not an engine designer I don't know what effect it will have. I drove the car briefly yesterday, it goes like stink so there can't be too much wrong :-)
Enoch

Been meaning to put this post up for a week or so now but just haven't got round to it. Finally finished the shaping of the riser and then got the primer coat on, unfortunately battery ran out on the camera before I took a shot of it finished in black but I think it came out OK, considering this is my first attempt.

Manifold is now fitted to the car and hopefully I'll get a pic of that tomorrow so you can see it fitted. I plumbed it all back up and connected all the tricity and to my surprise the car fired first time sweet as a nut.

As I removed the power steering system I also had to use a shortened belt and that went on a treat, I think it was an Alfa Romeo belt, I got the PN somewhere if anyone wants it.

Anyway a few pics attached of the before and after primer stage.

Cheers
Matt

Inlet manifold sizing is a lot to do with gas speed. If the diameter is too large, what happens is that the gas slows down and doesn't fill the cylinder so well at lower speeds, and can lead to a loss of torque. In a sporty car that may not matter as much as it would in a shopping car.

But looking at the mods that have been made the diameter should be the same, the difference is the shortened runners which will change the resonance of the system.

Don't know very much about this stuff, but I do know that runner length is considered very inportant by manufacturers of production cars, and in general the rule is the longer the better. Having said that, their concern is not only the headline max power, but how well the car pulls in a high gear at 1500 rpm, sas it will often be called on to do in traffic situations, whereas our concerns are different.

Even so, I know Jenvey, the performance throttle body makers, reckon that you should try for runners as long as reasonably possible. Not too sure about the resonance issue because resonance is something that happens at a particular frequency, and may have more to do (in a production car sense) with reducing intake noise than power characterisitics. Note that I said I don't know much about this stuff, though :)

That looks really nice Matt, its a good pulling engine the dohc and will suit the roadster really well. Been out in a couple of Sierra with the same engine and they pull very well. It's just the size and weight of the engine that puts some people off.

For me i would keep the intake as short as poss with a nice cone filter on for that nice induction roar, i've always believed that for production cars the long runners and air boxes is to prevent any induction roar - not really what we want....;)

Well Done....AndyH

Generally - you cannot make extra power/torque by tuning runner lengths, but you can move the position of the peak on the performance curves. The theory is that as the valve closes a reflected wave is produced back up the intake. When this wave meets a large volume change it is again reflected. If you can time this reflected wave with the normal pressure wave generated by the inlet stroke and the addition of the two provides an extra charge of air into the system - hence a peak. The same applies to exhaust system. If you look for Helmholtz or organ pipe theory you can do the quite simple maths behind it. Generally, the longer the runners, the lower down the RPM range your peak will be,

To get more power you need to increase the volumetric efficiency (VE) of your engine. Hopefully I'm not teaching people to suck eggs, but the VE is the relationship between the cylinder volume and the actual amount of fuel/air mix you can get in there. You can only burn as much fuel as you have air for, so you need to get more air in the engine. You can do this with a turbo and have a VE greater than 1. You can also improve the efficiency of the your intake system so that their are less frictional losses for the air coming in - in its simplest form porting, but the same principal should apply to your intake system as well.

Now of course when you really get into it, the two affects above actually combine. As your losses are based around the air velocity travelling through the system, but you have to size your diameter for a particular velocity. So in an ideal world you would have variable length and diameter intake runners!!

Lambos have variable length inlet pipes.
Thought you should know:)

Which have been used on many cars over the last 15 years.. ( cosworth BOB, 2.0 16V DOHC ( ford ). etc...

Can't remember which way round it is but short/long is good for power/torque.

TT

Short = less friction = more top power
Long = resonance down low = more low end torque

As do loads of bmws and the st170 engine im currently putting in my roadster!

The variable runner intake will be going on ebay rather than my car though :D

And quite a few motorbikes do now.

I'm not particulalry up with the latest fancy engines - but most of these inlet systems I've seen are 2 or 3 stage discrete systems, i.e. not truly variable. Does anyone know if any cars use a fully variable system?

I beg to differ.

Shorter runners will result in LOWER rpm HP whereas the longer runners will make HP in Higher rpm range.
IOW, for a town car shorter runners would be ideal and for racing engines longer runners would be more suitable. Ever wondered why racing engines have such beautiful long curved runner to inlets?

Basically an ideal plenum for a car to be used in town a good plenum design would be;

Plenum volume: 80 - 100% of engine volumetric capacity - normally aspired engines.
Runner lengths: anything from 200 - 300mm - measured from valve seat edge to runner inlet at plenum.
Runner diameter: 110 - 120% of inlet valve diameter.

General shape of plenum: Round or oval tapered down from TB - taper starts between 1st and 2nd intake from TB and runs well past last intake. Minimum diameter at the narrowest end of plenum must be about 1.5 times the diameter of the runners.

Just my 2 cents worth

907 on Locostbuilders can fabricate and TIG, does lots of great work to a fantastic standard, my recommendation

Happy days, engine out of the Sierra and into my chassis. Bit of a pig though as my garage door height prevented me from hoisting the engine high enough to clear the frame so had to lift up rear end of the chassis by about a metre just to shoe horn it in. I was hoping that I could have lifted the chassis over the engine but due to it's width it just wouldn't go. I'll stick some pics up after of the engine in it's new little home (well until I get the engine mounts made anyway)

:D

Now time for a brew and a sit on a radiator as I'm frozen through!

Later folks