TheSamba.com :: View topic - Dual Dell 45 tuning

Tue Apr 01, 2014 6:23 pm

I have eventually fired up the engine. Basically, it is:

2276
DRD L6 Heads
FK8
CR is 9:1
1 5/8" A1 Exhaust

I am running a pair of Dell 45s and have the following jets installed at present.

40 vent
Main Jet: 162
Air corrector: 200
idle jet: 70

I am planning to dial it in using a LM2.

With all that said, I have never done that before and therefore, on one hand, have been reading lots of related posts here.

On the other, I'd also like to hear from you your opinions as to what other jets I should make ready for this tuning exercise, as the engine is not in the U.S. and it takes about 2 weeks or so to ship the required jets. As such, I therefore would like to spend a little more money to make ready for the likely needed sets of jets as opposed to having to wait after finding out what I need.

Thanks for your help.

Tue Apr 01, 2014 7:44 pm

Use a 60 idle. Might be a little lean but enough to break in. Then you can use your LM2 and dial it in. Everything else is fine.

Tue Apr 01, 2014 9:42 pm

You have 40 vents in your 45 Dells?

Then try 60 idle, your 162 mains and 180 airs.

Verify the jets are sized correctly with a set of gauges as well.

Wed Apr 02, 2014 5:03 am

And the source for the 40 vents??...

Wed Apr 02, 2014 8:56 am

My apologies folks.
After checking with the guy who rebuilt my pair of Dell 45s, I think that 38 vents, as opposed to 40 vents, were installed.

Wed Apr 02, 2014 10:17 am

I'd start with a 58 idle, and the 180 air baseline.

Wed Apr 02, 2014 12:04 pm

[email protected] wrote: I'd start with a 58 idle, and the 180 air baseline.

John, does ACN have those in stock for immediate delivery? If yes, I would proceed to place an order for them.

Wed Apr 02, 2014 12:13 pm

Yes,

http://vwparts.aircooled.net/Dellorto-DRLA-Idle-Jets-7644-p/7644-drla-idle-jets.htm

and

http://vwparts.aircooled.net/Dellorto-DRLA-Air-Jets-10304-p/10304-dellorto-drla-air-jet.htm

Wed Apr 02, 2014 7:46 pm

Just in case, would you recommend any other jet sizes, other than those?

Wed Apr 02, 2014 7:55 pm

58s, 60s, and 180 airs. I think your mains are good, and the 200 airs give you some tunability.

Wed May 21, 2014 6:59 am

An update:

Before I place order for additional jets, I tried using a set of idle jets I pinched from another set of Dell 40s, which were marked 57. On re-starting, the engine was coughing and sputtering (snail was at about 5.5 on both sides, timing was at about 6-7 Deg at idle) and eventually died.

I then swapped back the 70 idle jets back in and was able to obtain pretty stable idle, about 800 rpm. I then used the LM-2 to measure the APR and obtained about 12.3 - 12.6.

After that, I swapped in another pair of Dell 48 trijets (air 2.00, main 1.80, idle .70). Those fired up fine and idled like a rock. I briefly adjusted the idle speed to about 800 - 820 rpm, the snail to about just less than 6, idle timing to about 7-8, best lean idle using the idle mixture screws. When these were all done, I checked the AFR again using the LM-2 and obtained 13.9 -14.3 reading, which was what I was trying to obtain when the Dell 45s were installed.

How do we explain this?

Wed May 21, 2014 8:21 am

You can put in any size idle jet and adjust the mixture screw to get the 13:1 AFR at idle. What you need to do is pull out your air and main jet stack, put in your idle jets, warm up the engine then adjust the mixtures then go around the block with just your idle jets. Keep going smaller on the idle jets until it spits and coughs and hesitates then go up one size on the idles until it is fine then you are done with the idle jets.

I guarantee you are rich with 70 idle jets.

Another thing is you need to verify that they are actually 70 idle jets with gauges since the stamping on the jets are meaningless.

Wed May 21, 2014 8:46 am

it coughed and sputtered because you went way lean, because the idle mixture screws were adjusted for 70 idles.

It won't matter if you go richer, but if you are going leaner on the idle jets, use this method.

Get the car warmed up. Now change ONE idle jet. Start it up, and re-set that cylinder's idle mixture screw. Then do the next one.

It will always idle and run on 3 cylinders. You can even do 2 at a time. But when you do all 4 you are faced with a situation where the car will not idle, unless you back out all the idle mixture screws a bunch first.

You need to understand you can idle rich with 40 idles in there, with the idle mixture screws way out. You can also idle lean with 80 idles in, with the idle mixture screws way in.

You went from carbs with idle mixture screws adjusted FOR 70 idles (far in), put smaller idles in, which made you lean. To get back to the same idle A/F you need to back out the idle mix screws. I prefer the 1 bbl or 1 carb change when going leaner, rather than swapping all 4, because I know it won't idle properly and makes initial setup a paint.

Wed May 21, 2014 8:54 am

Obviously the 57s are too small. For me I would start with 60 idles and keep drilling open till I reach the target afr under load. Dells like richer jetting then your comparable idf. Im running 65 idles on my 2017 tims stage 2s and 48 tri jets. On your 45s it will end up between a 60 and 65.

Fri May 30, 2014 6:10 pm

I backed out the mixture screws 6 turns and put back in the 57 idle jets. Started up the engine and it DID idle.

I then set the idle to about 800 rpm by syncing the carbs using a snail. Snail reading was about a bit more than 5. The timing was about 6-7 BTDC.

I re-adjusted the mixture screws to LBI, all screws responded pretty well and when done, the idle was about 840 rpm. At this point, do I bring down the idle to 800 rpm using the idle speed screws?

I connected up a LM-2 to check the APR at idle (engine is at its test stand) and obtianed a reading of 14.6 - 15.1, is this too lean?

Fri May 30, 2014 9:28 pm

Nothing wrong with 840 compared to 800.

Most engines idle best in the low to mid 13s. But I always tell people to set the idle mixture by EAR on a hot engine. I only use the Wideband to tell me if there is a problem (like 20:1). If it's 13:1 so be it, if it's 14:1 so be it. I don't set idle A/F according to a gauge, I set according to what the engine wants.

Just know that any time you change

idle speed
idle timing
idle jet size
Re-sync

you have to re-adjust all the idle mixture screws, 3x. Just do cylinders 1-2-3-4 in order, 3x. You can stop when you aren't making any changes to the settings. Normally you'll see a change the first 2 times.

If, for example on this engine, you changed idle timing from 6 to 8 BTDC, that kicks up your idle speed. You back out the idle speed screws to drop the idle, and now you have to re-set (re-optimize) the idle mixture screws. The change in idle mixture MAY increase your idle speed, and you get to do it again. Just remember to keep zeroing in on what the engine wants, until you are not changing anything, just verifying it. Then you are done.