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blomas
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Joined: September 18, 2013
Posts: 7
Location: Columbia
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 Posted: Wed Aug 12, 2020 5:17 pm Post subject: 74 standard beetle jetting recommendations |
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Fresh built 1600cc engine, big cam, light flywheel, dual 40mm kadrons with velocity stacks. 009 distributor. Exhaust flows into one exit with a 90 degree muffler out the side.
My problem is what seems to be pre detonation/ pinging on the lower end when you stomp the gas. It bogs and makes a rattle noise until you get about mid range. I have played with the timing and it doesn't seem to make a difference in the pinging weather it's advanced or retarded. From what I read 7.5 advance at idle should be in the ballpark but like I said it doesn't get better no matter where it's at. My next educated guess is carburetion.
(By the way I'm no expert at all. I've learned a bit from my dad and reading online but im fairly green on tuning an engine)
My kadrons have a 135 main jet I believe. I'm not sure of the idle jet. Is it correct that being too lean can be causing the problem I'm having? If so what idle and main jets would you recommend for this engine? The big cam and velocity stacks in my mind are what might affect the jet size needed. Any and all suggestions are appreciated. Thanks |
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mukluk
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Joined: October 18, 2012
Posts: 7452
Location: Clyde, TX
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| Posted: Thu Aug 13, 2020 7:43 am Post subject: Re: 74 standard beetle jetting recommendations |
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Pinging under load could be from being too lean, or you may need to run higher octane fuel. What cam and compression ratio are you running?
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blomas
Samba Member
Joined: September 18, 2013
Posts: 7
Location: Columbia
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| Posted: Fri Aug 21, 2020 11:53 am Post subject: Re: 74 standard beetle jetting recommendations |
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| Engle 110 cam. Stock size piston and cylinders so it should have whatever the stock compression is. Since this post I ordered a jet kit from the kaddyshack in which you fill out your altitude, venturi size, engine size, and exhaust size. They said the cam shouldn't matter. I got the jet kit but the sizes were ground off because they're all secretive about it. I have to guests that this is pretty close to ideal jetting size because these guys are experts. STILL have the low end pinging. Even when timing is retarded below 7.5. Been running 93 octane. HELP |
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Lingwendil
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Joined: February 25, 2009
Posts: 3999
Location: Antioch, California, a block from the hood
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| Posted: Fri Aug 21, 2020 12:01 pm Post subject: Re: 74 standard beetle jetting recommendations |
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Have you checked that the accelerator pumps are giving an instant clean uninterrupted squirt of fuel when you first hit the throttle?
Time your 009 with a timing light to 30 degrees when max advance is in, and let idle fall where it may.
I would think you need something like 132 mains, 135 sounds pretty fat. It sounds like your idle jets or passages are clogged or dirty maybe. What size idles are you running?
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73 super beetle thread http://www.thesamba.com/vw/forum/viewtopic.php?t=649622 Back on the Road!
Modify your Kadrons for SVDA http://www.thesamba.com/vw/forum/viewtopic.php?p=8115884#8115884
Cast iron VJU4BR8 SVDA reference thread- https://www.thesamba.com/vw/forum/viewtopic.php?t=...mp;start=0
Need replacement filters for original Kadron aircleaners? WIX #42087 is a perfect fit, as is Napa Gold #2087! |
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blomas
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Joined: September 18, 2013
Posts: 7
Location: Columbia
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| Posted: Thu Sep 17, 2020 5:01 am Post subject: Re: 74 standard beetle jetting recommendations |
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| Sorry for the late reply. I've kept going up on idle jets and the low end pinging has gotten less and less. I'm up to a 70 idle jet (the biggest size) and I STILL have a little bit of pinging. I see most people engines don't usually need this big of an idle jet. I'm inclined to drill it out a little more to fully stop the pinging. Any thoughts? |
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jarmchairpilot
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Joined: March 04, 2013
Posts: 492
Location: GALWAY,IRELAND
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| Posted: Thu Sep 17, 2020 11:57 am Post subject: Re: 74 standard beetle jetting recommendations |
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Did you pull the spark plugs they will show if the mix is correct, white tip is lean,
Black is rich,
sandy brown is just right.
All gaskets are new right?
Any little leak anywhere, carb/manifold/headers/exhaust will cause trouble. |
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Floating VW
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Joined: April 28, 2015
Posts: 1628
Location: The South Zone
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| Posted: Thu Sep 17, 2020 1:46 pm Post subject: Re: 74 standard beetle jetting recommendations |
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Improper timing and lean air/fuel ratios can cause detonation and pinging, but the usual culprits are high compression, low octane fuel and/or poorly designed combustion chambers.
If you are using 93 octane, is that 93 (R+M)/2, or 93 RON? 93 RON is somewhere between 87 and 89 (R+M)/2, and here in North America, that is considered a "low octane" fuel. The "high octane" fuel in the States is 93 (R+M)/2, which is about 98 RON.
Also, using "stock" parts is, unfortunately, no guarantee they still have stock dimensions (especially the aftermarket parts). Until you actually measure these parts, you are just shooting in the dark with respect to your compression ratio.
Worst of all, it's very possible your engine was built with an overly large deck height. A common "solution" for obtaining the correct compression ratio you want, is to increase the deck height volume instead of removing metal from the cylinder head or the piston crown. The result is an engine that, even though the compression may be good, is lazy, hot-running and prone to detonation.
The size of your idle jets has almost nothing to do with your pinging and detonation. Detonation usually only happens when the engine is under some sort of load, and that means it's on the main jets. Using super large idle jets can make the air/fuel ratio richer during the transition to the mains, but that's about it.
Reading spark plugs is not difficult, but there is actually a bit more to it than most people realize. Here is how I do it (this is something I wrote for this thread here: https://www.thesamba.com/vw/forum/viewtopic.php?t=671819&highlight=reading+spark+plugs , but I'll paste it again here just to make it easier for you).
| Floating VW wrote: |
| ps2375 wrote: |
| So, are those plugs pulled after idling or was motor shutoff under the load you wanted to read them for? |
That is the trick, right there.
What you have to understand is that when you look at a spark plug, the only carbon deposits you see there are what was formed during the absolute last time the cylinder fired. The tip of the spark plug is the hottest part in an IC engine, by quite a big margin. What this means is that, every time the cylinder fires, any and all carbon that is on the tip of the spark plug effectively gets burnt off, and whatever carbon is left over in the chamber after that last combustion event is finished, gets redeposited. And the reason you get carbon build-up in certain other areas inside the combustion chamber, is because these areas are able to quench enough heat to prevent some of the carbon from previous cycles from being burnt off. The tip of the spark plug, however, is not one of these areas. In some cases, the face of the exhaust valve (which is the second hottest part in an IC engine) is also not one of these areas.
So, when you read a plug, the first thing you have to do is decide which RPM range, and/or amount of load, you want to look at. Personally, I don't bother with reading plugs for idle or light cruise, because I feel there are much better ways of knowing if you got the A/F ratio right at these particular loads. And besides, really the only time you need to worry about an incorrect A/F ratio causing a major problem is when it's under load, such as during WOT (even the infamous 14.7 A/F of death won't hurt a thing, as long as the engine is not under any significant load). A notable exception would be when passing smog, but my machine is old enough that I don't need to bother with that, anymore.
After that, what you need to do is get the engine up to operating temperature (unless you want to know what your effective A/F ratio is when the engine is cold), and take it out for a spin. Now, here's the important part: When you reach the RPM/load you want, WITHOUT removing your foot from the accelerator OR disengaging the clutch, shut off the engine and pull the car over to the side of the road (or, if you time it right, you can shut off the engine and coast it all the way back to your garage). All safety precautions observed, naturally. If the cylinder fires even ONCE after you lift your foot from the accelerator pedal, the test is ruined and you have to start over from the beginning.
And finally, pull a plug.
Here's what you're looking for:
In this image, you can see a before and after shot of my no. 2 plug (the no. 2 is the easiest to remove). Ideally, you want you use a new plug for this, but a cleaned up old one will do if you're not too picky. This image was taken after a WOT pull up a small hill in fourth gear, taking care not to lift off the accelerator until the engine was shut down.
The ground strap: Before I cleaned it, you could see where the discoloration ended quite clearly. Not so much, after. At any rate, this indicates you have the correct heat range. Closer to the tip, the plug is too cold; closer to the base, the plug is too hot.
The electrode: You don't want to see more than a hair's width of clean metal on the tip of the electrode. If you do, your timing is too advanced and you might be damaging your engine. Also, look for small particles of grey-colored metal embedded in the ceramic insulator. This indicates detonation in the cylinder (those bits of metal used to be part of your piston until they got blasted off and landed on the spark plug).
Under heavy load, the base of the spark plug should develop a nice, completely formed ring of carbon around it. The carbon ring on my plug is perhaps a little on the heavy side, which tells me my A/F ratio might be slightly too rich for max power at WOT, but as someone mentioned above, these engines run hotter than most, so trading a little bit of power for a little bit of extra cooling is a good trade, in my opinion. You shouldn't see any carbon on the ceramic insulator, a little bit of brown or grey from the additives in the fuel is OK, but no black. Oh, the little copper-colored splotches are from the anti-seize compound I used on the threads, not from the combustion chamber.
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I hate to say it, but I don't think your problem is jetting, and I'd be careful you don't make it run pig rich in an effort to cover up the real problem. It might be timing related. Definitely set your timing the way Lingwendil said. The 009 usually ends up being around 10 degrees BTDC at idle, but around 30 degrees BTDC at 3000 rpm is where you want to be. It also might be octane related, so if you can get a higher octane fuel, it might solve your problem. But you might end up having to re-design your combustion chambers to make the problem go away completely.
Good luck, man.
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blomas
Samba Member
Joined: September 18, 2013
Posts: 7
Location: Columbia
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| Posted: Mon Sep 21, 2020 4:14 am Post subject: Re: 74 standard beetle jetting recommendations |
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| Thanks for the feedback. I did pull the spark plug this weekend and I didn't do that procedure, but it was in fact black. But the higher i go on the idle jet the better it runs on the low end. I feel if I went up one more size on the idle it would eliminate the low end pinging. Is it possible just my main jet is too rich? |
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blomas
Samba Member
Joined: September 18, 2013
Posts: 7
Location: Columbia
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| Posted: Mon Sep 21, 2020 4:31 am Post subject: Re: 74 standard beetle jetting recommendations |
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| When you say deck height are you talking about the top of the case? And I get 93 at the pump I'm not sure if it's RON or not. Would an octane booster work? The pinging I hear is on the very low end of the rpms. In standard acceleration it only pings for a tiny bit unless I really wind it out then it won't do it. I'm not an engine expert can you explain how high compression is seemingly making it lean on the bottom end? And how does richening up the idle jets seem to fix the problem yet it's not the right fix? |
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blomas
Samba Member
Joined: September 18, 2013
Posts: 7
Location: Columbia
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| Posted: Mon Sep 21, 2020 4:32 am Post subject: Re: 74 standard beetle jetting recommendations |
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| When you say deck height are you talking about the top of the case? And I get 93 at the pump I'm not sure if it's RON or not. Would an octane booster work? The pinging I hear is on the very low end of the rpms. In standard acceleration it only pings for a tiny bit unless I really wind it out then it won't do it. I'm not an engine expert can you explain how high compression is seemingly making it lean on the bottom end? And how does richening up the idle jets seem to fix the problem yet it's not the right fix? |
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Floating VW
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Joined: April 28, 2015
Posts: 1628
Location: The South Zone
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| Posted: Tue Sep 22, 2020 9:37 am Post subject: Re: 74 standard beetle jetting recommendations |
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| blomas wrote: |
| Thanks for the feedback. I did pull the spark plug this weekend and I didn't do that procedure, but it was in fact black. But the higher i go on the idle jet the better it runs on the low end. I feel if I went up one more size on the idle it would eliminate the low end pinging. Is it possible just my main jet is too rich? |
No problem. I'm assuming the engine was allowed to idle before you pulled the plug- remember, the plug will only show you what the conditions were like in the combustion chamber the last time it fired. Your spark plug is black because your air/fuel ratio at idle is extremely rich. Your idle air/fuel ratio is too rich because your idle jets are too large (and/or because your idle mixture is not adjusted properly).
I couldn't say if your main jets are too big without knowing how big your carburetor venturi is. Do some research on the relationship between venturi size and main jet size. This will give you a good place to start when choosing main jets.
| blomas wrote: |
| When you say deck height are you talking about the top of the case? And I get 93 at the pump I'm not sure if it's RON or not. Would an octane booster work? The pinging I hear is on the very low end of the rpms. In standard acceleration it only pings for a tiny bit unless I really wind it out then it won't do it. I'm not an engine expert can you explain how high compression is seemingly making it lean on the bottom end? And how does richening up the idle jets seem to fix the problem yet it's not the right fix? |
Deck height is the distance between the crown of the piston and the squish pads in the cylinder head. The deck height in a stock engine is around 0.055". In some countries, stock cylinder heads were made with a "step" in the mating surface between the cylinder and the cylinder head. This almost doubles the deck height, which, as I mentioned earlier, is a cheap way to reduce compression, but is bad for engine performance. An ideal deck height for safe performance is between 0.040"-0.050".
You're in Columbia, right? I just looked it up here: https://www.wikizero.com/en/Octane_rating.
It appears that 93 octane in Columbia is about the same as 84 octane in the USA. That is extremely low! This is probably the root of your problem. Using some sort of octane boost will definitely help you.
Using large idle jets will increase the amount of overlap during the transition to the main jets. What this means is that, as you open the throttle, there is a time when both the idle jets AND the main jets are delivering fuel to the engine. Ideally, you want the idle jets to die off just as the main jets are starting to wake up. If the idle jets are too small, it can cause this transition to be too lean (which is corrected by making the main jets wake up a little sooner); if the idle jets are too large, this will cause the transition to be too rich, which is bad for performance but will help reduce detonation and pinging.
Do some research on how to properly set the jetting on your carburetors and how to properly set the timing on your distributor, and get some octane boost for your fuel. You'll be happy again in no time!
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