Failed Rolling Road!

[Thrashed]

Hi Guys

 

Went for my rolling road to get the engine set up to run right and pass emmissions for IVA on the 16th Sept, BUT...... did not really get too far.

 

Main problems are that the sump is still leaking like a sive and lost about 0.25 of a pint in oil. The other big issue was that the rubbers holding the ZX6R carbs on are too short and the clamps were not getting a good enough hold. Suprising as this was all supplied by GBS with the manifold!!

 

This was causing some good air leaks so not really able to get much done on the set up, but after a few runs found that the fuel pump was not man enough for the job. I used the ZX7 fuel pump but on tick over was about 2.5 PSI but when at about 5k revs was 1 PSI.

 

So jobs i need to sort are silicone rubbers to bolt carbs down better, bigger fuel pump and regulator and stop the sump leaking (alreadty got this planned, thanks Gaz ).

 

If anyone else has had these problems or knows a good way to fix any of them, please let me know.

 

On the plus side at about 5k on the rollers at about 3/4 throttle is sounds awesome and it did not blow up so alls good really.

 

Cheers

 

Steve

[steve in stockport]

silicone is a nightmare to get a seal, I've used Gates radiator hose from local motor factors, £15 for a metre. I t works well but you still need to be careful when fixing it and it's not weight supporting so needs bracing to the manifold - that's why GBS cut the silicone so short.Or for a proper job get some GPZ 900 carb rubbers from ebay, these will fit and support the carbs.

For the fuel pump I've been using a facet fast road solid state pump for three years, no regulator and no problems. Good enough to keep a 170+bhp red top fuelled right up to the rev limiter. You really need to make sure you strip the bowls off the carbs and get rid of all the crap in there, if the floats and needle valves etc are clean and working properly you won't need a reg.

[Thrashed]

Thanks Steve

 

Bought some from my local Kwak dealer so will give them a go. Inhad the original zx6r rubbers but they have an oval flanged end so would not fit. The gpz are round and loom perfect. Did you still fit a brace?

 

Thanks

 

Steve

[steve in stockport]

You should be ok without any bracing, I'm still on rad hose as the inlet tracts on the vauxhall are oval, I may get round to trying them one day.

[knights_templar]

Hi

 

Question:-

 

engine is not known, lets assume 1600 cc pinto, carbs are designed to feed 600 cc (zx6). so a carb designed to feed each cylinder with 150cc of air and mix it with fuel every induction stroke is asked to deliver 400cc of air. with fuel, every induction stroke. drill out the jets, and throw fuel down it and you get the power. emissions?

 

Fitting of carbs are fine with GBS setup, provided they are seated correctly. can vibrate loose if not fitted perfectly. note bike carbs have special inlet collars, that are expensive, and are not designed to fit car engines.

 

As for IVA. I know of one vehicle that was able to pass current regulations and get a new plate. If you are going for age related it will be easier, but still a problem.

 

regards

[Thrashed]

Thanks

 

Engine is a 2.0 pinto. Bought some of the gpz rubber( yes expensive) but they seem to work. Just need to get sone proper clips to hold the tight.

 

Going for age related so emissions just need to pass that which should b ok once set properly.

 

Thanks

[knights_templar]

Hi

 

for a 2.0ltr, that's over three times greater than the carb was designed for.

 

I know its the "cheap" way of getting more power, let more air in, and tip in enough fuel, and your bound to. and I know its the "in thing" on the forums, but have always considered a very inefficient way of doing it.

 

anyway, if you now have the fitting sorted, should be relatively easy to get a age plate, given time and a gas analyser. but I suspect you will have to do it again after the test to get it to run properly.

 

If you have the original carb for the engine, I'd stick that on, its designed to meet the requirement and is easily tweaked at the test centre if out.

 

what happens afterward, well everything stays as it was at the test, doesn't it?

 

regards

[agent_zed]

i think in terms of the carb sizing for differnt engines there are lots of variables.

 

the standard webber 2v carb on my 1.6 pinto has a 28mm and 30mm choke so if my maths are right

 

area of a circle = Pi times r squared.

 

so for 28mm choke

 

3.14 x 14 squared = 615

 

so for 30mm choke

 

3.14 x 15 squared = 706

 

total = 1321

 

 

if you have 4 x 30mm chokes on a bike carb you get

 

4 x 706 = 2824

 

which is significantly bigger.

 

I might be completely wrong but to me this seems to show that it is far more than adequate to cope in terms of air flow with over twice the area of a standard carb. or am i missing something?

[knights_templar]

Hi

 

No, quite correct, that's how you get more air in, so you can add more fuel, and get bigger bang.

 

have no problem with that theory.

 

The problem comes with the volume of air.

 

In theory 600cc draws 150cc of air at max throttle (actually less if you take into account air cleaner restrictions, inlet track throttle shaft, valve etc).

 

A 2.0 litre will try and suck in 500cc of air through the same carb in the same time span.

 

without going into the mists of how carbs work their magic. http://www.dansmc.com/carbs2.htm if your interested, just looking at the carbs at tickover will show they are working hard and way out of their build tolerance, and as for fuelling, just drilling out the main jet is a very crude way of tuning an engine.

 

whilst I can understand the draw of cheaper power, I worry about the extra load on the carbs and the risk of major engine problems due to incorrect fuelling.

 

So what you gain in one hand can easily be taken by the other.

 

Regards

[agent_zed]

just playing devils advocate and for the sake of conversation (i'm about a million miles from being a carb expert) but the motorbike you are talking about at full throttle will redline at 14,000+rpm whereas a pinto 7000ish. So the carbs will be dealing with more volume than a car engine carb to start with. I would also guess that bike engines are designed to be more for performance than economy so will be designed to shift a larger amount of air to start with.

 

I can't see the problem if its rolling roaded and tuned. How would this be different to any other carb. Its sole job is to provide the correct fuel/air mix across the rev range so as long as this is happening how can this be wrong? sure just bolting them on and hoping might not be the correct way.

 

From what (very) little i understand, bike carbs are ment to be better for economy than twin 40's, for example, as they have a variable venturi. The 40's only being efficient at higher revs and being rubbish at lower revs as the air flow isn't right to get the venturis working perfectly, and these are designed for cars.

 

please correct me if/where i'm wrong, not trying to cause an arguement just find this interesting and like to learn more.

 

cheers

[knights_templar]

Like a good discussion

 

150cc theoretical max intake per induction stroke x 14000 rpm is 210000cc as you only get induction every second revolutions / 2 = 105000cc

500cc --------------------------"---------------- x 7000 rpm is 3500000cc ---------------------------"----------------------- / 2 = 1750000cc

 

1750000/105000 is 16.66 times greater than design.

 

they are variable venturi or constant depression carbs just like the SU and its copiers Zenith/Stromberg (diaphragm instead of piston) Nikki (SU patent ignored) and even the Ford VV (an ill fated attempt to get around SU patent) all designed for cars.

 

Your right, this type of card has a number of advantages over fixed venturi. but only when used in the application for which they were designed.

 

have a look at http://www.dansmc.com/carbs2.htm, you will see what I mean about tuning.

 

anyway theory aside have a look at the carbs on a bike when it is running, the sliders stay steady at what ever revs you set, then have a look at them fitted to a larger capacity engine, the sliders pulse quite violently at tick-over, less so on steady revs, and on full revs some actually top out. as slider position has the greatest effect of fuel delivery, how can this be correct for the engine?

 

Not arguing they don't do what is intended, they do give more power, not efficiently, and not economically and some would say not reliably.

 

but maybe its just me, always been one to buck a "trend", everyone is doing it, just look at you-tube, so it must be right?

 

would probably have been hung draw and quartered in the past, more likely to argue the world was round, coz everyone else said it was flat.

 

Regards

[Guest mower man]

Bike carbs seem to work . Why that is I 'm not sure but the amount of cars that are out there producing good power and economy seems to say that they are the poodles doodles .I'm old school but agree that Webers can be an absolute bitch to set up and do drift in and out of tune with regularity but thinking back 25/30 years the fastest BMC 'A' series engines around where on Amal bike carbs produceing over 100 bhp from a 1000cc 8 port headed screemer so it's not realy new .I'would like to try them on my pinto but am too tight to spend the money on some thing I might regret for the type of running I mainly do [touring]. thats my 2p's worth---===mower man

[knights_templar]

Hi mower man

 

Have an Amal mono for my triumph 5TA. 500 cc twin

 

Same engine was fitted with twin Amal's think it was the T100 and from memory smaller diameter.

 

Two 5TA carbs or four T100's will feed 1000cc no issue with that, they are designed for that volume of air.

 

600cc carbs on 2000cc engine?

 

A carb is a carb it mixes fuel and air, what it is fitted on doesn't really matter, more fuel and air bigger bank more power, no quibble. Have set enough up in my time.

 

my point is how well is it doing it? that's all, it works, just doubt some of the stories out there as to how well.

 

And to go back to the start of the thread, Thrashed was at a rolling road to set up for IVA, at that point we did not know he was going for age related, which will make life a lot easier, but he may well have to go back again to undo IVA set-up afterward. Just appeared a lot of time, and possible expense, when the bog standard carb will meet the requirement, put the bike carbs on afterward and tune for power on the rolling road.

 

Discussion is irrelevant really, bikes moved to injection in 2009 so the supply of carbs will eventually dry up, or become less cost effective, and with the number of people fitting them, probably sooner than we think.

 

Regards

[agent_zed]

Like a good discussion

 

150cc theoretical max intake per induction stroke x 14000 rpm is 210000cc as you only get induction every second revolutions / 2 = 105000cc

500cc --------------------------"---------------- x 7000 rpm is 3500000cc ---------------------------"----------------------- / 2 = 1750000cc

 

1750000/105000 is 16.66 times greater than design.

 

 

 

sorry but think you missed a '0' on the first calc (i think - hope i'm right or i'll look a fool saying its wrong )

 

150 x 14,000 = 2,100,000 (not 210000) / 2 = 1,050,000

500 x 7000 = 3,500,000 / 2 = 1,750,000

 

1,750,000 / 1,050,000 = 1.66

 

not quite as bad as 16x's you were thinking but agreed still more than designed to do orginally

 

also agreed that injection throttle bodies are the future but a tad more expensive once you have to add in the ignition system etc, but then the price of fuel will also make it more viable as the effiency will hopefully be better on injection.

[knights_templar]

I will eat humble pie,

 

can't even read what's on my calculator, must admit was a bit surprised at difference.

 

teach me to wear my glasses, and not read forums whilst painting the bathroom.

 

assuming I haven't had another mental lapse, 0.66 is over half as much again, isn't it?

 

Anyway, lots off people do it, all appear happy, and I'm not judging their decision in any way, probably would have done the mod myself in my younger days. did have a Reece Fish carburettor on a 1303S beetle once, advanced timing, centrifugal advance distributor, straight through exhaust, high lift rockers etc................ that went well, till it seized No 3, pulling away from some hot hatch, that was embarrassing to, and expensive.

 

probably accounts for my caution now I've got old.

 

Regards