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robington

Tuning

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So, I am trying to tune my car and am struggling a bit. This may all be a bit beyond me.

 

The timing is sorted and it is fine.

 

It's the carb tuning I am struggling with. I am getting quite a bit of smoke from the exhaust and uneven running, hesitation on acceleration and spitting back out the trumpets.

 

The set up is - a rebuilt engine and the carbs were rebuilt about 3 years ago. It was running ok before they came off, so I thought there would be no need to touch them and I put them back on, but with new spacer plate O rings and damper rubbers.

 

I got the Des Hammill book, a balancer and colourtune.

The carbs are balanced.

When I used the colourtune I got the blue flame but I have to say the running is still not right.

 

During my work I discovered that the idle jet that feeds cylinder 1 is seized, so that will have to be rectified but if I got 3 cylinders working well I would be happy - the spitting occurs on all of them at different times.

The plugs are all sooty Black

 

I looked at some threads on here before I started, but I am non the wiser really and am wondering if there is something basic that I am missing here.

 

Any suggestions?

 

Thanks..

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Upgrade today to remove Google ads and support TLF.

To be honest, I was unable to get the colortune to work. I even spoke to their techie people who suggested it was due to the adaptor not extending far enough into the chamber as would a spark plug.

After building my engine and carbs, I got it to start ok, and run, but in the end decided that getting it done properly was a job best left for an expert.

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I've never used a colortune but do use the carbtune. The carbtune is the best balancer and you should get one if you don't have it. If your are sure that all the internals of the carb are set correctly - floats, jets etc..- and you are sure all the carbs balanced correctly, then all you can adjust is the idle mixture settings. Once I get the engine running and up to temperature I close each idle mixture screw until the engine starts to run funny. I then open the screw until it smooths out. Then I open it one more 1/4 turn. That's about it. Settings are different on the N/A engine, my idle screws are about 4.5 turns out from seated. If you turn an idle screw and it has no effect on the engine then something is a miss. Either an issue with the idle jet or the mixture screw it's self. I'm not sure you can stop Dellortos from spitting completely, as that appears to be a characteristic.

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Cheers, Gavin

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Agree with Gavin, setting with a Carbtune works well, if you have disturbed the accelerator pumps then these will need setting up too, if I were you and the carbs have not been used for a few years I would strip, clean and rebuild with new seals as old fuel would have dried out leaving residue within.

With a seized jet which is fairly common it seems like overhaul is the way forward.

Dave :)


Do or do not, there is no try! 

 

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Just drop the carbs into an ultrasonic tank for a complete clean inside and out. To set up the balance the carbs I've used a VacuumMate for years. http://www.tecmate.com/pdf/VMaw-LF1-HR_eng.pdf Makes it easy to set up and diagnose multiple carb setups.

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BTW, a good tip to stop idle mixture screws seizing is to put some silicone sealant at the tops of the towers.

After mixtures have been set of course :)

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I want one!!

Not cheap but looks great, seems to be a US item but will see if available in the UK to avoid duty costs!

Thanks for the tip Roo.

Dave :)

It's from the UK Dave. Shadowfax Probike has them at £399 http://www.probike.co.uk/it060006.htm I've set up the 4 Weber 50IDF carbs on my V8 Vantage with it, purrs like a kitten.

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Cheers Roo, debating now as going to the US in March to Norfolk and June to Orlando so may pick one up then, Works out about £500 with VAT and shipping here.

Dave :)


Do or do not, there is no try! 

 

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Roo, you have my absolute dream car - V8 Vantage. I've always wanted one in Aston Martin 'Storm Red' with cream hide, piped in red. Late model one, 85ish, with the extended arches etc..... Back in the late 80s in the UK I knew someone that sold them from his house. I remember seeing the engine with the cam covers off and thinking crap that looks complicated in there!. We used to go out and take photographs of them, I was studying photography at the time, and he would include a framed picture of the car when he sold it. I also went to Newport Pagnell and did a factory tour around the same time. Nothing like seeing a wing being shaped using an English Wheel !. What year is yours?.

- sorry to go off topic.

Edited by GavinS1

Cheers, Gavin

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Rob,

 

   Regarding hesitation under acceleration, have you verified just by looking into the carbs (CAR NOT RUNNING) and pulling on the throttle cable to see that the accelerator pumps all squirt a good stream of fuel?   Could be something as basic as that -- look for blockage in the accelerator jets, progression holes, or in the passage that goes to the accelerator pump diaphragm (there's a needle valve there, IIRC?).  Or maybe an accelerator pump diaphragm is torn or has a hole?

 

   Also, when you said timing is okay, did you mean the distributor/ignition spark timing *and* that the cams are timed properly (i.e. didn't jump a tooth when installing new cam belt)?   (do the dots all line up?)

 

   Is there anything blocking the distributor arm movement (for the advance)?

 

   Everything okay with the ignition system (good spark, etc.)?

 

   Given everything you've said, I'd go back to the basics and disassemble the carbs looking for possible air leak as well as for little bits of stuff blocking passages.  I've cured popping issues with Dellortos doing little things like replacing O-rings (such as on the idle mixture screws) that weren't that old, replacing mounting (to manifold) O-rings, and just making sure all the brass parts are clear, the correct size and properly seated.

 

Cheers,

 

Tony


Tony K. :)

 

Esprit S1s #355H & 454H

Esprit S2.2  #324J

1991 Esprit SE

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Roo, you have my absolute dream car - V8 Vantage. I've always wanted one in Aston Martin 'Storm Red' with cream hide, piped in red. Late model one, 85ish, with the extended arches etc..... Back in the late 80s in the UK I knew someone that sold them from his house. I remember seeing the engine with the cam covers off and thinking crap that looks complicated in there!. We used to go out and take photographs of them, I was studying photography at the time, and he would include a framed picture of the car when he sold it. I also went to Newport Pagnell and did a factory tour around the same time. Nothing like seeing a wing being shaped using an English Wheel !. What year is yours?.

- sorry to go off topic.

Yeah they are a favorite of mine Gavin. Have had about 8 Vantages over the years, down to a few at the moment. Sounds like Mike Fleming in the UK selling them from his house. He's still about. I had a Red one just like you described http://www.v8vantage.com/11992.htm took it to my house in Australia, but it's in New Zealand now. Spend loads of time at NP, they stopped building cars there a few years ago and it's a sales/service/restoration facility now.

 

11992a.jpg

Edited by v8vantage

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To be honest, I was unable to get the colortune to work. I even spoke to their techie people who suggested it was due to the adaptor not extending far enough into the chamber as would a spark plug.

 

I always used a Colortune ti set the mixture on my Esprits & it always worked great. Just screw the plug into the head then screw in the supplied extension lead, didn't bother with the tube they supplied but used an old mirror to be able to see the colour of the burning mixture. When you say you couldn't get it to work, what problems were you having?

 

I then used a Morgan Carbtune to set the air flow balance, again worked great giving very accurate reults & a fraction of the cost of the Vacuummate.


Cheers,

John W

http://jonwatkins.co.uk

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John,

I was having difficulty seeing the colour of the 'flame', even in the darkenss of my garage. But worse than that was the terrible back-firing through the exhaust.

 

The techies at Colortune put his down to the fact that the adaptor doesn't extend far enough into the combustion chamber (as far as a spark plug would), which was causing incomplete ignition. As such, unburnt fuel was igniting in the exhaust - quite un-nerving really :(

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John,

I was having difficulty seeing the colour of the 'flame', even in the darkenss of my garage. But worse than that was the terrible back-firing through the exhaust.

 

The techies at Colortune put his down to the fact that the adaptor doesn't extend far enough into the combustion chamber (as far as a spark plug would), which was causing incomplete ignition. As such, unburnt fuel was igniting in the exhaust - quite un-nerving really  :(

 

Obviously I can't explain that except that it's not the reason the Colortune techies gave, I can only reiterate that on the two S3s & 1 Stevens Turbo that I used a Colortune on it always worked perfectly & there was certainly no back firing or even occasional popping.  :unsure:


Cheers,

John W

http://jonwatkins.co.uk

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Whatever it was, my 2.2 n/a didn't like the Colortune, and there was clearly an irregular spark.

I even tried cleaning it with carb cleaner, but it made no difference.

However, as soon as I put the plugs back it was fine.

 

Anyhow, it's now been set up by a known carb expert, who ultimately made it run a whole lot better than I would've. Even if the C'tune was working ok :) 

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Thanks, Dave.

It was a rolling road. TBH, I increased the chokes from 36mm to 38, so I knew I'd need a re-jet anyway.

But I must say, they did a very thorough job. Set the carbs up, and fitted new idle jet emulsion tubes, pump jets and main jets.

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Rob. With my carb turbo I set the carbs up using the Morgan Carbtune (you can usually get these on ebay) and then I set the mixture to the default setting in the handbook which is 6 half turns out from closed. Then my friendly MOT station takes the exhaust measurements and adjusts each mixture screw the same amount to get ideal CO2 etc readings.Interestingly at my last MOT the default position gave the best readings.

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I'll put in another recommendation for the Morgan Carbtune...bought one from the Motorcycle Show ages ago, it's the original with the mercury columns...(!) It hangs sweetly from a hole drilled in the rear lid where the lid goes over the slatted inlet through the engine cover. Makes setting the carbs FUN!! Once they are synchronised and adjusted, I do the mixture by setting all the carbs to the recommended starting setting and working from there. There's a bit of thaumaturgy involved, you have to invoke the Spirit of Dell'Orto and make the blood sacrifice, but it's a good way to spend an afternoon....especially when you get to the road testing..... 


Scientists investigate that which already is; Engineers create that which has never been." - Albert Einstein

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The only other thing I can think of to check for, is that all four butterfly discs are in sync with each other. I have heard / read that the throttle shaft can get bent.

I find the tuning of the carbs to be the most satisfying thing to accomplish. Once you have the carbs basically set up it's all about little tweaks this way and that. Once you get the hang of it, you can dial the carbs in in just a few minutes.

Edited by GavinS1

Cheers, Gavin

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Thank you all for the replies.

The balancer I used was the Weber Synchrometer from Eurocarb and it was very easy to use, however I can see the benefit of having all 4 readings at the same time with the Morgan unit.

The general message I am getting here is to take the carbs off and do a rebuild, which to be honest I was trying to avoid, but with the firm knowledge that I have a seized idle jet I think I should just get on with it.

I have seen the gasket kits on the eurocarb website, but I was thinking about replacing all the jets as well regardless of the condition of them on the basis that  the cost of them is not too prohibitive.

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Where do you connect the pipes to on a Morgan carbtune? It looks a lot more likely to work than my "trusty"gunsons carb balancer.

Phil

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