Jetting/tuning issue

[Gütterßnipe]

I've had my new engine fitted along with new twin weber 40 IDFs
Karl at Wolfsburg Wizards didn't have the equipment to tune up properly.

The factory venturis are 28's but unsure about the rest -
The carbs have been balanced but it's popping and hesitating upon acceleration

So it's only had the short drive home so far.....

I'm gonna take it to get correctly tuned and jetted in a couple of weeks but until then
Not sure if I should be using it, so for the time being it's grounded.

Will be forking out to get it transported to the tuning shop too.....

Major bummer but don't want to bugger the new engine up.

The Question is........

Should I stay grounded and wait till it's been properly jetted or will it be ok to drive.

 

[jonboylaw]

What jets are fitted? 55 idles and 130 mains will be fine. Anything around that should be ok for pottering about. If the mains are significantly less than 130s then you may want to keep it under 2k rpm and drive on the idle




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[Dave.P]

Sounds like a blocked idle jet, take them out and blow through with compressed air. These cans are handy to have in your toolbox,
http://www.ebay.co.uk/bhp/compressed-air-can" onclick="window.open(this.href);return false;

Check this thread for a diagram and some useful info on setting up etc
http://forum.earlybay.com/viewtopic.php?f=4&t=22243&p=194117&hilit=Idf+idle+jet#p194117" onclick="window.open(this.href);return false;

Make a note of the idle jet size , it pays to know exactly what jets your running before setting up

 

[jonboylaw]

Just re read your symptoms. Ignore my statement. Could be as Dave states, blocked idle jet/circuits, or air leak.
Definitely find out what jets you have and try to get it running reasonable well before the dyno session.


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[Gütterßnipe]

Cheers for the advice, Jon/Dave.

Could it even be blocked jets on a brand new set of Carbs?

Gonna find out what jets have been factory installed today and will post update....

Thanks

Spence

 

[jonboylaw]

Yes, you can get all sorts of crap in new carbs, swarf from machining or crap from fuel lines etc.
Popping is because it is running lean. Also check the accelerator pump is working ok.

 

[Gütterßnipe]

Ok....bit of a delay in finding out but each of my 40IDF's
Are currently factory set as follows.....

Choke 28
Aux Vent 4.5
Main Jet 115
Air corr 200
E tube F11
Idle jet 50
Needle valve 175
Pump jet 50

Turns out they were just bolted on and the idle screw adjusted......

 

[Dave.P]

If it were me I'd get some 55 idles from " fast road cars" on eBay, all the rest sounds good.
Maybe blast a bit of carb cleaner through while they're out too.

 

[Gütterßnipe]

Thanks for the advice Dave,
Should my mains not be bigger too....
It's for a 1776....

 

[Trikky2]

This should help

 

[Dave.P]

Christ I'm only running 135 mains in my 2.1 with 32 vents :shock: any bigger and it bogged down..
Thought the theory was vents x 4 - 4.3 ? (but im using drla's mind you )
Might be worth getting some bigger mains too for what little they cost then ?
You won't know what is best till its set up properly anyway.

 

[Trikky2]

Christ I'm only running 135 mains in my 2.1 with 32 vents :shock: any bigger and it bogged down..
Thought the theory was vents x 4 - 4.3 ? (but im using drla's mind you )
Might be worth getting some bigger mains too for what little they cost then ?
You won't know what is best till its set up properly anyway.

The chart does not apply to DRLA's

 

[madmike]

Those jets are spot on,Check your dizzy and time it should of checked the float's level before installing them and fuel pressure

 

[Gütterßnipe]

Those jets are spot on,Check your dizzy and time it should of checked the float's level before installing them and fuel pressure

Mike,

Are you referring to mine or Dave's....???

Spence

 

[madmike]

Yours,I'm running a 1600 and have 115's with your 1776 maybe 120-125's,, 130's are to big unless u own a filling station :lol:
That chart is way off :roll: :roll: :roll:

 

[Trikky2]

Yours,I'm running a 1600 and have 115's with your 1776 maybe 120-125's,, 130's are to big unless u own a filling station :lol:
That chart is way off :roll: :roll: :roll:

Odd. [puzzled smily]

Worked fine with my Weber IDF 40 twins on a 2.1 - returned just under 27 mpg on 2200 miles round Spain and Portugal back in 2008.

I would gladly query the chart on your behalf but unfortunately the person who gave it to me is no longer with us. (Moby on Vzi - RIP )

 

[madmike]

Could be our 'Fuels' are different formula too :roll: and I'm at 1500' altitude all them things ad to the fun :lol: :lol:

 

[Todster]

Hi,
I've just changed my carb for a pair of EMPI HMPX 40s, (copy of the weber IDF40) as standard they came with 52 idles and 115 mains, they went on a 1641. I had similar issues to you in that they were popping and had a fairly hefty flat spot around 2K RPM. The first thing I did was change the mains to 125s. Completely changed the running, the flat spot is now only just noticeable, just off idle and as soon as it goes through around 1200 RPM, it pulls clean through.
I've got a set of 55s to try as idles, but as of yet have not got them in.

Good luck, I have found that they are a joy to work on.

Cheers
Mark

 

[Gütterßnipe]

Cheers for all the info and advice guys.

What pressure should my fuel regulator be set at for twin 40 IDF's ??

Mark,

Hearing from you gives me hope......I should be getting it sorted on Friday with a bit of luck,
half-term doesn't help when you wanna sort out bus issues.....

Spence

 

[madmike]

3 1/2lbs. please don't use a 'Dial' type regulator they are JUNK!!!,I've had good luck with Holly's,But search,,,you probably have something different over their? but better