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!

 

[mattsooty]

Oh to have so few constraints! The fun we could have!

MS

 

[PEW]

Here I was, thinking the thread was closing and more help arrives!

The little Reliant 850 ccengine was designed about fifty years ago and has run on a carb for the ten years since I built this trials car. It was originally designed to power a 3 wheeled car. Three wheelers don't get emissions tested in UK. As soon as this one was fitted into my 4 wheeler, it was required to comply with the emission limits for the year of registration.

It usually fails the emissions test at MOT test time. The SU carb is traditionally very poor for emissions at idle, where the UK testing is done. Reliant owners usually tweak the mixture weak at idle prior to the test, which weans that the car won't run above idle. Before driving the car home they tweak it back to normal again. My friendly tester has another way of getting round that, enough said.

However, I want to improve things in that respect as well as bringing things into this century.

The car is used on road and also for off-road hill climb/trials competitions, so power is an issue, especially as we compete against cars with much bigger engines (3.5 litre in some cases). That said, I have one fairly recent class award where we beat all the MGs at an MG Car Club Trial and the only thing that beat us was a car in the "unlimited" Class 8.

We've tinkered with three different carbs and each has had its strengths and weaknesses. Extreme nose up attitudes at full power in first gear and subsequent hot starting after heat soak have always been an issue. FI should solve that in addition to the emissions issue whilst giving good power output.

The heated swan neck has a direct coolant hose supply, btw. Using it allows the throttle linkage mechanism to gain clearance from the inlet and exhaust manifolds, which is another issue on this little non-crossflow engine.

 

[BrianGar]

Are you allowed alter the fixed in-chamber volumes - cr ? Or alter chamber shape, but not volumes?
Are you allowed or have you altered valve and valve seat geometries?

The crux with many old engines is chamber shape, valve grinds, valve seat wall thickness(many are thicker than they need to be narrowing port) and of course large tolerances on all hydrodynamic bearings.
But of course then, your down to materials...and what will give next.
Perhaps your intake and carb should be further down the list?

What have you done already?

One last point, many think carbs are junk(nowadays), maybe so for various adjustments they need every now and then, but when setup correctly, they will and have surprised some efi whizzes...
I once saw two cars on rollers, each putting out around 135 standard. They had been modified, one ran efi, the other webbers, the efi fell short 5hp at 175hp. The web put down 180. Ill never forget the look on your mans face, he just could not understand how a flathead screwdriver could beat a laptop(Both in correct and incorrect hands of course)

Brian,

 

[patprimmer]

I was somewhat involved with Danny Miller and Gene Adams in an Engine Masters Competition team a few years ago. The team chose to build an early(late 50s early60s) Chrysler Hemi V8. The rules change every year to keep it interesting. One year there was an option of 8 carby chokes or EFI with certain limits on the manifolds. Of course the organisers expected twin 4 barrel Holles on a tunnel ram vs EFI from OEM IR from central plenum type manifolds. Danny chose 4 by twin choke Webbers and they scored better than the EFI in the configurations both could run that year so Danny competed with the Webbers and did quite well (Third out of maybe 20 starters I think from dim memory. They where scored roughly on area under the power curve over a specified power rpm range.

Regards
Pat
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[PEW]

Brian,

Engine mods are free from regulation but I reckon I've done just about all the mechanical mods that can be done. I achieved 58-60 bhp on a Weber 34 ICH (rolling road figures). I've since gone away from that carb and fitted a 1.5"/38mm SU (standard is 1.25"/32mm) because the engine would often cut out on a steep slope restart and then refuse to start. We're allowed 6 seconds to clear the line after the marshall's flag drops then are deemed to have failed the hill. The engine was often fluffing up badly and stopping with the Weber fitted, due to the extreme angle of the float chamber causing very rich mixture (i.e the contents of the float chamber tended to dump into the in the manifold). If we can't restart the engine and clear the line, as well as failing the section, we often have to reverse back down, which can be very exciting (!) and holds up the whole event because there is no other escape route.

My car is one of 60 made. It's seen by the designer as probably the most powerful normally aspirated one in its type/class using this type of engine. During one trial I was approached by a very enthusiastic marshall who asked to see my supercharger setup because he was building an Austin 7 special and wanted to copy it. He was completely taken aback when I told him that it didn't have one. I don't think he believed me until I lifted the bonnet and let him see for himself.

Other owners have not been as successful in tuning their Reliant 850s and some have recently fitted Suzuki G10A engines (relatively modern 1 litre, 3 cylinder, fuel injected). I don't want to go down that route as it involves a major rebuild and chassis and bodywork mods. There is also an advantage in keeping with the smaller engine - in the event of a dead heat during a special test timed sections, the smaller engine wins by default.

The non-crossflow head uses parallel vertical valves and there is no scope for changing this. The head has been ported as far as it can be safely done and chambered. Due to other work on the block and wet liners the CR is very high (it pumps straight up to 225 psi on a dynamic compression test) and I have no deire to increase this. In fact I've done some recent work to remove material to decrease the CR and this time will fit a head gasket of 0.0715" thickness (standard is .047", in an effort to improve reliability in that area. The crank assembly has been dynamically balanced. On these engines the factory conrods are known to be good to 9,000 rpm and flat top pistons give no trouble either, so nothing needs doing there.

I am about to fit a slightly hotter 280 degree cam; this is as yet untried but is expected to increase top end power and willingness to rev a little higher (present cam completely runs out of go at 6000 rpm). As part of this upgrade I initially intended to merely fit Megajolt ignition to replace the original camshaft/chain drive distributor (already converted to electronics and advance curve modified) but I want to be able to experiment with mapping the ignition because I've always felt there has been more to come from this engine. Having looked at the relative cost of using a Megasquirt module to also include fuel injection, I'm looking at giving it a go.

To give you some idea of what we get up to, here's a YouTube link of our little car:

http://www.youtube.com/watch?v=tmllbFxzHKg&feature=related

 

[patprimmer]

Do the rules prevent you making an individual runner manifold with either multiple carbies tilted from horizontal to correct for average slope.

Do they prevent a log plenum with IR from the plenum and a single throttle body. I have made inlet manifolds out of copper pipe and plumbing fittings before today and exhaust pipe tube can also be used. I know aluminium looks the part, but it actually only needs to direct and control airflow.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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for site rules

 

[PEW]

Hi Pat, Thanks for your participation.

I think I see what you are getting at - then fit one injector per runner. There's nothing to prevent me doing that. In effect that's what the original manifold was, albeit with a downdraught entry mouth.

We did find better performance with the internal wall of the manifold cut away. The inlet ports are so close together in the head casting it prevents enlargement of the runners of the original manifold by more than a couple of millimetres without breaking through the dividing wall so I couldn't match the size of the enlarged inlet ports. I reckon the narrow tubes had become the limiting factors to gas flow to the port. Allowing the ports to "suck from both teats" as it were, removed that limit. I understand that ideally the runners should be as long as possible. On this car using long runners blocks access to the battery (which sits alongside the engine) and accessory drive belt adjustment. I had originally used twin SUs on separate, semi-downdraught siamesed inlet trumpets, giving a longer inlet tract. Car ran very well (and they looked very nice indeed) but they were totally impractical for other than occasional use. My car also gets used on the road, we've covered almost 40K miles since I put her together a decade ago.

Alternatively, as I think I mentioned earlier, I could possibly fit simple ally plates inside each arm of my present "big bore" cast manifold, to provide crude fuel spray guides which should minimise fuel charge robbing, if in fact that should prove to be a problem (which is where my original quest began ).

All interesting ideas. Thanks again. Paul W.

 

[BrianGar]

'it pumps straight up to 225 psi on a dynamic compression test'

The valve grind/overlap would affect this reading and no indication of cr.

But I feel you know this.

Ill think some more,

Brian,

 

[PEW]

Hi Brian,

Yes, I'm aware of the lack of accuracy of that method. However I also know that a standard engine of this type (10.5 to 1 CR) normally gives around 195 psi. The cam in my engine is standard but the head face has been skimmed and the block shaved when I first had it re-manufactured (I wish they hadn't done this, especially as the pistons now sit very slightly proud of the liners at TDC, but that's another story altogether).

So we do know it's a little bit higher than 10.5 to 1.

I've not had time to re-measure the volumes of the combustion spaces as yet. These are "bathtub" shaped with a "waist" on one side (not sure of the technical term but they look like a rounded capital letter "B". This time I've taken some more metal out; de-shrouded the valves slightly and removed a little off the "egg-timer waist" between the valves. I will re-calculate the actual CR with the new thick gasket eventually. I'm hoping to have reduced it back down to a more sensible level.

 

[WGJ]

Isn't that a typical 'Weslake' chamber shape?

Bill

 

[PEW]

I don't think Weslake were ever involved in making 850cc engines for Reliant three wheeler cars, but of course it might be similar. (Reliant did get BRM involved once, but their engine conversion never made it to production and there is only one example left).

My car's cylinder head:

 

[BrianGar]

PEW,

As Pat mentioned, ITBs may be the way to go too? But of course they have drawbacks compared to log style manifolds.

'Generally' ITBs lose mid range torque, but offer gain at higher rpm. Dont go down the road of large or common diameters, fit smaller bore ones, this will keep some mid torque by keeping air speeds up. 7/10 times I see throttles fitted with too large a bore.

Obviously, if you do go this route, and aim to make power further up the range than you currently make it, keep in mind your gearbox ratios may need a re-jig to take full advantage.


Easy and cheap steps are, make car light, and fit the smallest width(within reason), and diameter rims that will fit over your brakes.

Overall, you will be limited with what you can do with a cast Iron head, since al transfers heat faster, and therefore can handle higher crs without hotspots. Al heads were one of the notable changes when It came to getting more power out of top ends - Is head Al or Iron?

Brian,

 

[PEW]

Brian, thanks for that. This is a car used for road and off-road trials (for nearly a decade) so we have already put a lot of thought into gear ratios, wheels, tyres etc because in our field (!) grip is everything. We use 5x16 inch crossply tyres on very narrow rims. The wheels are die cast and are made specifically for the car. Only specified wheels and tyres can be used for competion use (or we get put into "Class 8" where anything goes, including unlimited rear engined specials and there is no way we can compete with them with only 850cc). I now use Avon Tourist for the road and carry two spare wheels with Firestone ANS for the off-road stuff. These are essentially WWII Harley Davidson despatch rider bike tyres. We had to get these cleared for competition use as they are a bit "knobbly" which isn't normally allowed as the spirit of the classic trials event is for prepared road cars on relatively "normal" treaded tyres. I always drive the car to and from the trials (very old fashioned, even by UK standards - many other cars turn up on trailers these days) and I change the wheels over on arrival.

The existing gearbox ratios can't easily be changed because nothing else fits - the gearbox is very small on these cars. I have recently fitted a longer diff ratio to reduce the engine rpm for road use as it produces quite a bit more torque than the norm. One member of our group did obtain a quote for a new gear cluster but it apparently was to cost almost as much as he had spent on his entire car. I'm happy with the gearbox ratios!

Regarding weight reduction - for the road yes, we have a car weighing 460 kgs but in fact we tend to ballast them up at the rear end for more off-road traction during competition work. I hang my two spare wheels off the rear of the car and carry a heavy tool bag, another tool box, a spares box and jacks, spare fuel, water ballast etc in the rear compartment.

If you look at this video link below you should get some idea of what we try to emulate (Sorry to say, I can't easily do the "old school" accent though). It's all for fun, no prize money given, no sponsorship allowed, so costs are a big issue.

http://www.youtube.com/watch?v=8YLmb08T0z4

Rgds, PW.

 

[PJGD]

I think that there is little doubt that this engine has a Weslake-designed combustion chamber, as did many British engines of that era. A close read of the patent here:

http://worldwide.espacenet.com/publ...n_EP&FT=D&date=19500517&CC=GB&NR=637209A&KC=A

is very instructive, since so often the specific features that Weslake had recognized as key to the enhanced performance of his chamber are misunderstood or even removed during a head job. I am thinking of aspects such as the swirl-inducing inlet port (counter rotating in adjacent cylinders when fed by siamesed intake ports), and the curved chamber side walls to deflect the incoming mixture around the head of the valve.

PJGD

 

[PEW]

PJGD,

An interesting link! I seem to have inadvertently copied the intricacy of that design by de-shrouding the inlet valves during previous DIY work on my ally cylinder head. It made a noticeable difference, more than I'd expected for the small amount of metal removed.

Regards, Paul W.

 

[WGJ]

Thanks for posting that link PJGD. A you said, many British manufacturers of the 50s and 60s utilised the basic Weslake chamber design with some success. I think that Ford UK was the only manufacturer not to - too tight to pay a royalty, I imagine.

Bill

 

[PEW]

Having spent a couple of days working on ideas for this project, I seem to be uncovering more uncertainty.

My initial concern was charge robbing when using four injectors in the existing "Siamesed runner" manifold. I spent some time pondering over this, then saw the answer was to design and make a couple of ally plates to weld inside the engine end of the manifold, to direct the fuel sprays directly into the port they were meant for. Essentially, place a simple dividing wall between ports.

Having finally got this sorted, I trial fitted the manifold. The injectors will actually be required to sit less than an inch from the exhaust headers. Not a good recipe for longevity of plastic bodied injectors, even with heat shielding fitted.

The single injector spaced away from the exhaust in a simgle throttle body may be more practical, if not the best design for performance. In effect an electronically controlled carburettor working in closed loop.

 

[BrianGar]

Paul, I went image hunting and found image below, is this what your dealing with?

If you now have paired runner divides ported out totally, then I would buy another manifold and leave them in there. Mount an injector in each tract spraying onto valve, or near it, and batch fire them. Individual runners to each valve will airspeed up.

Brian,

 

[BrianGar]

second time lucky with image

 

[MikeHalloran]

Nope; images ain't happenin'.


Mike Halloran
Pembroke Pines, FL, USA