Side by side fuel injectors in open manifold.

[PEW]

I have a fuel injection conversion project in mind, using either a Megasquirt or Canems programmable control system.

My old non-crossflow, 850cc four pot engine presently has a single semi-downdraught SU type carburettor. The carb is fitted on a heated swan-neck adapter which takes the mixture flow into the mouth of the main inlet manifold. The ports are arranged E-II-EE-II-E. The conventional cast ally inlet manifold has two horiziontal branches, feeding the two pairs of side-by-side inlet ports.

The main problem with this engine is its very small size and lack of space around the inlet ports and in the engine bay. It's a very tight fit in there, too small for any conventional throttle bodies, including motorcycle types, which are all crossflow. To keep the conversion simple, I'm therefore looking at the possibilty of fitting a single throttle body downdraught fashion, onto a vertical adapter bolted on the existing gas flowed and matched inlet manifold (i.e. replacing the heated swan neck adapter). This would allow me to fit two injectors into each of the manifold's two branches, one for each inlet port.

These would be fitted by welding in comercially available, push-in tubular injector adapters on the top face of the two manifold branches.

The inlet manifold branches have no internal walls and therefore act as plenums. This works very well on the carb setup. The injectors will be fitted side by side, at a 45 degree angle on the manifold, to fire directly towards the ports, only about 25-30 mm away from the face of the head casting.

I see no issue with this but I'd just like to canvass opinion here before I make an expensive mistake and ruin my specially made ally inlet manifold because I've missed something obvious.

Thanks in advance!

 

[patprimmer]

If this is a race car, you need to build a race car and stop fussing about with relatively minor problems.

EFI as such will not improve power much at all over a carby set up. To get gains you need to increase airflow, improve airflow distribution and improve fuel distribution. Charge robbing does not only rob fuel, it also robs air.

If the battery is in the way, move the battery. That is not exactly a major problem.

If the exhaust is n the way, reroute it to make more room.

If the engine bay is narrow, make a manifold with individual runners that sweep back over the engine so the plenum is on the opposite side to the exhaust. Use one large throttle body on the plenum and four individual injection nozzles. Make the inlet manifold out of exhaust tubing for reasons of economy. It isn't really all that hard to do.

Alternatively, cut holes in the side of the engine bay so long as there will be some room for the manifold to project through. I mean, this is supposed to be a race car.

Regards
Pat
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[BrianGar]

Pat, I love the way you can say in one post, what takes me 6 posts.

But yes Paul, thats pretty much it really,

Brian,

 

[PEW]

(Quote) If this is a race car, you need to build a race car and stop fussing about with relatively minor problems. (Unquote).

Sorry guys, we're obviously talking at crossed purposes here. This is definitely not a race car and power is certainly not the only priority. If I wanted to build a race car, I'd have built a different car altogether. As I mentioned, this is essentially a 1950s style road car. For fun we use it for off-road trials.

All I'm trying to do here is replace the existing carb setup with an EFI, without changing the car into something else it was never designed to be. We're certainly not trying to win the NASCAR series with it. The "more power" priority was posted by someone else. I'd hoped I'd made things clear enough by posting the link to the video of us using the car in a trial. As you perhaps hadn't watched it, here is another:

http://www.youtube.com/watch?v=77RRLlYXZ7U

We got second in class that day. The following year (2010) we won best in class, which surprised the MG drivers as it was an MG Car Club invite and we beat them all. We were second overall, to a Buckler, built especially for trials and it arrived and went home on a trailer. We drive to and from the trials.

Anyhow, I thank you all for your contributions. I think we'd be better to leave the subject to rest here because I sense this thread is beginning to cause frustration in some.

As I said, I will report back with observations when the car is back on the road.

 

[izzmus]

As an aside, Subaru made TBI engines for years with a similar intake layout. One throttle, one injector, two necessarily long runners to each cylinder head, which had a single port runner for each cylinder pair. Being a boxer four, each cylinder pair had two intake strokes in a row.

It worked well enough for those relatively low-revving, low output engines. Roughly 90hp from a 1.8l. The turbo variants did get divided intake ports and four port injectors.

 

[PEW]

Yesterday I spoke to the proprietor of CANEMS, who manufacture one of the aftermarket injection systems available in UK. I was assured their system will work well, provided that the single injector has sufficient capacity to provide all the fuel required.

With this in mind I've also been in touch with a fuel injector specialist who advises that a single 400cc injector (a long stroke, 20 degree spray Asnu) should do the trick and will cope well with mapping.

 

[BrianGar]

Im sure it has the capacity to supply all fuel required, but whether it will supply it and distribute it to all cylinders that need it, when they need it, with optimum flow paths and velocity is a whole other question,

Brian

 

[patprimmer]

Whether it will do it any better than a carby in this case is also a question.

Regards
Pat
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[PEW]

I agree it will probably produce no more power than a carburettor due to airflow issues already discussed, but as I've already tried to emphasise, this isn't the main aim of the conversion.

I've had practical problems, especially during off road trials with different carbs, which the TBI should overcome. Some of the slopes we are expected to drive up are extremely steep (too steep to walk up or down). This can cause either fuel starvation or flooding depending which carb is used and in which orientation it's fitted; we think due to float chamber limitations. Other owners have the same problem.

The car also has to pass UK emissions testing during its annual MOT check for road use. As I wrote in one of my original posts, the car has always had a problem with the emissions test (the Reliants all do, due to limitations of the SU carb they were originally fitted with at idle). In the past we have had to get around this by various means. We have to find a "Reliant friendly" MOT tester to do it. However, the UK system has now been computerised which makes it much more difficult to "fudge it" as all emissions test attempts are recorded on a database.

[To be honest, as well as hopefully helping me solve these issues, another reason I want to do this is out of curiosity because no-one else seems to have fuel injected this little engine type before].

 

[patprimmer]

So after 67 posts your real objectives are spelled out. It seems they are an ability to run at extreme angles and a cool factor.

A carby with the float bowel directly below the discharge nozzle or jet is a needle type metering jet is used. I think from memory, some SUs and a lot of moror bike carbies are built that way.

Some down draft Webbers also have tall narrow float bowels close to the nozzles. This means a large angle makes little difference between fuel level and fuel discharge point.

Also a throttle body injector will do it. Many D series Honda engines have a dual point fuel injection system. It is throttle body and has low and high speed injectors at the TB. They should be almost free being the low performance option on these engines in the late 80s early 90s.



Regards
Pat
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[PEW]

Pat, I actually spelled out my original objective in post #1!

Quite a number of folk have had things to contribute (I'm grateful for all of it) and the scope has become wider than I expected. I asked what seemed a simple question in the first place and have received answers on things I didn't feel I needed an answer to. The only reason this thread has gone on for so long is that almost everyone has their own fixed ideas on how "tuning" should be done, including keeping the carburettor. I've read all the advice, done more research (including from the manufacturers and suppliers), looked into the practicalities and adapted my plan to suit.

I have already tried to politely bring the thread to a close on two occasions. However, folk (including yourself) have continued to post stuff for me, so I feel obliged to give them the courtesy of a reply.

You latched onto something posted by another contributor about increasing power output and wrongly assumed I was building a racing car and was therefore out to gain maximum power. I've never said that. Sorry for any confusion. You gave advice on improving airflow via manifold improvements and seem to expect me to redesign the whole inlet system and re-jig half the engine bay on your say-so.

However, I don't feel inclined to redesign more than I really have to because increasing the power output isn't the main priority. If I wanted to merely wring the maximum power out of the engine then I would put the quadruple motorcycle throttle bodies on it (I have a set of near-new Suzuki 750 TBs in the garage and did look at this on a previous occasion, that's why I bought 'em). Or I could supercharge it, as a couple of other owners have already done, albeit not without sacrificing reliability elsewhere.....

When I've tried to explain what I'm trying to do here in more detail, because of answers given, you seem to become irritated about it. If this is a problem for you, then please feel free to stop replying. If you wish to carry on, then that's just fine too.

Having taken everyone's advice into consideration (not just on this forum) I have now decided how to make the conversion to suit my own needs, the look of the car, the practicalities and the fairly limited budget. The project is moving on.

It's been a very interesting discussion which I note has produced quite a large number of replies compared to other recent topics. If anyone remains interested enough to know how it works out (or not) then I'll report back at a later date with some results.

If not, then I'm happy to finish the thread at this point.

Thankyou, again and peace to you, Pat!