Can I pass 1990 emissions in UK with a carb?

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Ian Anderson
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Can I pass 1990 emissions in UK with a carb?

Post by Ian Anderson » Sun Nov 24, 2019 2:21 pm

Ok here goes

GT40 replica and it has a 1990 dated engine so need to meet emissions for that.
The current set is a JE 102 cam, which is quite lairy and 4CUX Hotwire injection.
Yes it works but does not look period correct

Feeling on these cars is an issue with two long thin tanks on either side. Brake, fuel sloshes forward and the outlet allows air in to the pump.
And with 2 tanks you need to return the fuel to the same tank or it will overfill and leak from the other.

So
I have a cross over valve called a Pollak, which does the job almost bit not good as my second one mow leaks.

I have a low pressure pump feeding a swirl,pot then on to a HP pump to the rails.second in line HP pump is getting noisy so more £££

So I am thinking of going back the way these were designed, low pressure pump feeding a carb.

Not overly worried about fuel consumption as not a daily driver and only used weekends.

So an Edelbrock 4 barrel inlet and Weber carb seems like the easy route. But will it get past emissions for a 1990 engine or will I end up changing everything again?

Last option may be to link the two tanks together in say 19 mm cross pipe and not worry about stuff, but Jags note when doing this and parking your car at a sideways angle the lower side tank overfills and leaks...... not good!

Anything anyone can suggest?
Or should I be looking for an old block and get emissions to visible smoke only?

So May possibilities and not sure.... what do you suggest?

Ian


Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

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Re: Can I pass 1990 emissions in UK with a carb?

Post by DaveEFI » Sun Nov 24, 2019 2:40 pm

IIRC, 1990 falls into a category where a decent carb should pass the MOT OK. Think the magic figures are better than 3.5% CO and 1200ppm HC at a normal idle speed.

With your fuelling problem, the usual answer would a swirl pot on some sort. Either internal or external to the tanks.
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Re: Can I pass 1990 emissions in UK with a carb?

Post by SimpleSimon » Sun Nov 24, 2019 5:20 pm

You will breeze it your 2 years early for CAT more stringent testing
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Re: Can I pass 1990 emissions in UK with a carb?

Post by DaveEFI » Sun Nov 24, 2019 7:02 pm

SimpleSimon wrote:
Sun Nov 24, 2019 5:20 pm
You will breeze it your 2 years early for CAT more stringent testing
Assuming the carb is properly tuned. Even a carb SD1 will pass '92 specs.
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Re: Can I pass 1990 emissions in UK with a carb?

Post by stevieturbo » Sun Nov 24, 2019 8:58 pm

if it passes now, there's little reason a good well tuned carb shouldnt be ok too

Cam might be the only concern, but what are the current emissions levels at idle ?
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Re: Can I pass 1990 emissions in UK with a carb?

Post by Ian Anderson » Sun Nov 24, 2019 9:59 pm

stevieturbo wrote:
Sun Nov 24, 2019 8:58 pm
if it passes now, there's little reason a good well tuned carb shouldnt be ok too

Cam might be the only concern, but what are the current emissions levels at idle ?
Well it does pass, but engine has to get really hot, fans running pretty well constantly, then read the one. And up revs to 2500 and the second bit passes. So emissions are tight already.

So should I be looking at a cam change at the same time? And if so which one to get power?

Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

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Re: Can I pass 1990 emissions in UK with a carb?

Post by Eliot » Mon Nov 25, 2019 3:14 pm

Seems a backward step to me.
One problem i had with the webber carb on my dakar was fuel sloshing around the float chambers and down the inlet making giving it a rich stumble (discovered by using a wideband) now clearly my dakar is pretty wobbly side to side, but i've heard similar reports of cars stalling under braking presumably for the same reason.

Personally I would address what you have in hand rather than go back to carbs;
Have a read on the Ultima GTR forums on pistonheads, as they have the same dual-tank & efi problem - i cant remember the best solution now, but there have been some very expensive solutions using a billion pieces of fancy jic fittings which didn't work.
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Re: Can I pass 1990 emissions in UK with a carb?

Post by DaveEFI » Mon Nov 25, 2019 4:03 pm

You basically need what amounts to a smaller tank that the main ones feed. Of such a size as it can remain (nearly) full while the fuel in the others sloshes around. To help prevent cavitation to the HP fuel pump. In some cases, a circular baffle round the tank outlet can do it. Could be more tricky on an off roader, though.
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Re: Can I pass 1990 emissions in UK with a carb?

Post by Ian Anderson » Mon Nov 25, 2019 6:15 pm

DaveEFI wrote:
Mon Nov 25, 2019 4:03 pm
You basically need what amounts to a smaller tank that the main ones feed. Of such a size as it can remain (nearly) full while the fuel in the others sloshes around. To help prevent cavitation to the HP fuel pump. In some cases, a circular baffle round the tank outlet can do it. Could be more tricky on an off roader, though.
Thanks Dave,
I already have a swirl pot. So HP EFI pump should never suck air!

It is filled from the main tanks

Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

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Re: Can I pass 1990 emissions in UK with a carb?

Post by Ian Anderson » Mon Nov 25, 2019 6:24 pm

Eliot wrote:
Mon Nov 25, 2019 3:14 pm
Seems a backward step to me.
One problem i had with the webber carb on my dakar was fuel sloshing around the float chambers and down the inlet making giving it a rich stumble (discovered by using a wideband) now clearly my dakar is pretty wobbly side to side, but i've heard similar reports of cars stalling under braking presumably for the same reason.

Personally I would address what you have in hand rather than go back to carbs;
Have a read on the Ultima GTR forums on pistonheads, as they have the same dual-tank & efi problem - i cant remember the best solution now, but there have been some very expensive solutions using a billion pieces of fancy jic fittings which didn't work.
Thanks Eliott, I sort of feel that way but there are numerous high performing cars that run 4barrel carbs without too many problems. Yes the acceleration and braking could cause problems with float bowl sloshing.the GTRblokes are running more modern kit this is supposed to replicate a 60s car, but it even has the wrong motor.

I will check over that site.

Oh and building now I would have hydra at in the tanks

Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

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Re: Can I pass 1990 emissions in UK with a carb?

Post by r2d2hp » Mon Nov 25, 2019 6:36 pm

Did you ever get it mapped Ian?
If I remember correctly back from 2008 at the dyno Day it sounds the nuts but based on the engine spec made very poor power and the graph looked terrible.

will see if I can find the dyno run and image from the day. Think Eliot was there on the day with the glowing headers

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Re: Can I pass 1990 emissions in UK with a carb?

Post by r2d2hp » Mon Nov 25, 2019 6:41 pm

Here it is
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Re: Can I pass 1990 emissions in UK with a carb?

Post by stevieturbo » Mon Nov 25, 2019 6:59 pm

Ian Anderson wrote:
Sun Nov 24, 2019 9:59 pm
stevieturbo wrote:
Sun Nov 24, 2019 8:58 pm
if it passes now, there's little reason a good well tuned carb shouldnt be ok too

Cam might be the only concern, but what are the current emissions levels at idle ?
Well it does pass, but engine has to get really hot, fans running pretty well constantly, then read the one. And up revs to 2500 and the second bit passes. So emissions are tight already.

So should I be looking at a cam change at the same time? And if so which one to get power?

Ian
If it's borderline now, I cannot see a carb improving matters any. It would seem a backwards step. A better idea might be a mappable ecu for the injection instead, so you can fine tune things to help at MOT
9.85 @ 144.75mph
202mph standing mile
http://www.youtube.com/watch?v=XgWRCDtiTQ0

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Re: Can I pass 1990 emissions in UK with a carb?

Post by sidecar » Mon Nov 25, 2019 8:52 pm

I've worked on loads of Eddy 4 barrel carbs, you can reduce the effect of them going rich when braking or cornering hard by making sure that the carb is mounted level, many manifolds tip the carb forward and that can make it spill fuel into the primary venturies when braking, fit a wedge plate if required. Even when new the float heights are never set correctly, increasing the float height by 2mm helps because it lowers the fuel height. You can not go more than 2-3mm through because the "spill height" becomes too large which messes up the carburation. Blocking off the passage at the back of the carb that connects the two float chambers also helps when cornering. Having said all that if you really know how to throw your car around a track then you can still get an eddy carb to misfire. I have always found that an Eddy carb will need recalibrating on any engine that I have worked on, they seem to be OK but are usually way too rich on the cruise circuit. If you manage to get the carb to work with a vac advance ignition system and the carb has been recalibrated then you can get very good MPG out of them. Getting these carbs to work well with any of the standard Lucas vac canisters is not easy, I had to open up the last canister that I worked on and modify the 'internals'.

My latest set of mods include modifying the standard straight leg boosters so that they are annular boosters, this allowed me to lean off my cruise circuit one full ratio. On Muscle Manta's SD1 which is currently running a stock-ish 3.5 we managed to lean the mixture off to at least 16.5:1 on cruise and it still responded to the throttle very well, it may have been happy going even leaner!

Edelbrock are making some carbs with annular boosters now, personally I think that they could have done a better job because I can tell from the jets and the rods that they have fitted that the 'signal' at the booster is not all that strong.

Below is a picture of my modded boosters...
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my annular boosters.JPG
Last edited by sidecar on Tue Nov 26, 2019 8:00 am, edited 1 time in total.

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Re: Can I pass 1990 emissions in UK with a carb?

Post by Ian Anderson » Mon Nov 25, 2019 9:50 pm

Hi yes it is a screamer and runs 250ish Hp
That was the designed in Hp by J Eales. With usable revs2500 to6500
Je102 cam, balanced, ported, biggest available valves and marked on paperwork as full race TVR.it is only 3.9 so down on CC to some of the bigger units produced now.

And it does that powers well 2500 up.

Kangaroos al low throttle 1300 to 1800 rpm as ecu cannot move mix fast enough and goes rich then lean you learn to drive not in that rev range! Was explained it refreshes every 2 seconds!

I never got anyone to map it as nobody could redo the chip except Adams and I could never get him.

Was going to get a ms plug and play exchange unit but was told it needed a trigger wheel and I have no space at the pulley, chassis and firewall in the way.

So I used to be indecisive bot now I’m not sure.

Which way to go?

Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

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