Correct timing

[mhagie]

OK now I am confused here,I want to check/set my timing but I am unsure of just what is the correct timing degrees BTDC or ATDC
Right now I have 5* ATDC @1400
I have read from Britannic that 2.4 - 2.6 BTDC @1400 is good.
I have read from Grape that 6* ATDC is the best,needless to say I am confused here.
No offense to either but what is the correct timing? I have a clone to Dr Lee's engine with the exception of a Banks Turbo Kit 4911 pump and all.
Any help here is appreciated.
Thanks, Merle
Forgot to mention these readings are from my Rotunda 078-0100 timing meter w/lumy probe.

[ 06-19-2005, 10:35 AM: Message edited by: mhagie ]

[spitfirenut]

Not 100% sure, but it seems like I read something about different types of meters. One reads the injection pulse while another reads the flame. If reading the pulse on the injection line it would have to be earlier than if reading the flame because the flame is real time and with the pulse you still have to inject the fuel. I'll be waiting to see if that's a correct assumption.

[arveetek]

Just bumping this up to the top for further comments.

I agree that setting the timing depends on what type of meter you're using. If using the lumy type, I would assume that the timng MUST be set ATDC, so that the piston isn't forced back down the wrong way. The lumy style measures the actual flash from ignition taking place.

If using the clamp-on pulse type, then the timing can be set BTDC. This is because you're measuring the injection fuel pulse, before ignition takes place. By the time the fuel ignites, the piston has traveled past TDC and is beginning it's way back down.

Are my assumptions correct?

Is 4* to 6* ATDC the optimal setting when using a lumy style meter?

Casey

[78Chev]

Jamie at DD once told me that they set timing at 11 advanced at idle, 6 to 7 advanced above 1100 RPM. He said they use the pulse type. The Ferret manual for their pulse adapater says that pulse can precede flash flash from 7 to 10 degrees. If it is as much as a 10 degree difference then the equivalent lumy reading would be around TDC at idle and 3 ADTC above 1100 RPM.
It would be great if we could get an official word on timing these things - it seems too mysterious to me! When I get mine engine back together I'm gonna check the timing ASAP so I need to know the numbers. Of course I have to find a lumy meter too...

[mhagie]

Jamie told me basicly the same thing 10* at idle 5* at 1100. Checked it with my lumy probe and found 0* @idle 5* ATDC @1400.
I guess its to each his own but for me the lumy is the way to go.
Still waiting for the answer that started this topic in the first place.
78 Chev watch for e-mail
Merle

[78Chev]

Merle - my email address is knuth2 at comcast dot net. BTW: I don't have a Ferret pulse type - just found the manual online.
Randy

[arveetek]

Okay, I've had some time to play around with my timing, using a Snap-On MT1480A timing meter, and I've arrived at the figure of -4.5 degrees, which I believe means 4.5 degrees ATDC. That's pretty much where I had it set for on my trip. When I got home, I bumped it up a bit, but then it rattled too much. That setting was about 2.5 to 3 degrees ATDC. Any more advanced than that, and it would have stopped running or caused damage, I'm sure. There's no way this engine will run at TDC or BTDC when measuring combustion.

I'm going on a camping trip this coming weekend, so I'll tow my trailer and report back with results.

I checked the timing in cylinders 1, 2, 3, 5 and 7. I couldn't get to 4, 6, and 8 due to the downpipe preventing access to the glow plugs. The timing in all the cylinders I checked was in the 4 to 5 degree area. I couldn't find any cylinders that were way off, so I still don't know what's causing my rough idle. It's not missing, but it just doesn't sound right to me.

One thing I discovered is that the pushrod on the passenger side of the pump retards timing, not advance it. I read hear on the page that when you push in on the plunger with the engine running, it should advance the timing and make it rattle more. It's just the opposite. With the engine running at 1400 rpm, you can push the plunger in and watch the timing fall from -4.5 degrees to nearly -25 degrees. It's very quiet then and slows the rpm way down. I called Tim at accurate diesel to confirm my readings. He confirmed that the plunger is supposed to retard timing, not advance it.

Casey

[britannic]

I had a turbo making up to 17psi of boost, so my timing was appropriate for that set up. NA engines, can be around 4-6* BTDC +/- 2*, so a baseline of 4 can be a good starting point. I also had timing gears, which really makes for accurate timing.


Originally posted by mhagie:
OK now I am confused here,I want to check/set my timing but I am unsure of just what is the correct timing degrees BTDC or ATDC
Right now I have 5* ATDC @1400
I have read from Britannic that 2.4 - 2.6 BTDC @1400 is good.

[Dieselboy]

During the first phase of its life, my engine has been happy with 14 psi peak boost and 2* BTDC @ 1300. It runs well, EGTs are right on, and it sounds great.

For the upcoming second phase (new IP and injectors), I'm going to experiment with timing again. I want play with the 6* ATDC @ 2000 that was mentioned here recently.

It's good to see so many members with timing meters now. We can do a lot more comparing of results than we could just a year or two ago.

[mhagie]

To help confuse matters I will say that I bought a Rotunda timing meter but then I found a snap-on MT 1480A meter and bought it.
I found a HUGE difference between the Rotunda and the Snap-on, mainly in the fact that Snap-on has a small plastic gauge that checks the positioning of the magnetic pulse pick up and the timing tab.
When using the Rotunda I was way out on figures,after using the gauge I found the pick up was bent too far away from timing tab.
I am wondering if this contributes to the confusion between BTDC and ATDC.
78 Chev and I will be doing some experimenting between lumy and pulse timing in the near future and will report findings.
Merle

[john8662]

Originally posted by mhagie:
mainly in the fact that Snap-on has a small plastic gauge that checks the positioning of the magnetic pulse pick up and the timing tab.
When using the Rotunda I was way out on figures,after using the gauge I found the pick up was bent too far away from timing tab.
I'm glad someone on here brought this to attention. I have the little plastic gauge myself and have found that it makes a HUGE difference in the results of timing the engine if the tab is in the right place!

I didn't know what the piece was until the guy I was letting time my engine let me know what it was. He was glad I had the piece because he had lost his, and his unit was a Stanadyne and he had no clue what the part number was for it. Now, since he got the snap-on number off mine, he can get another.

[Peter J. Bierman]

And that number is?

Peter

[arveetek]

Part # for the Snap-On "Timing Guage Bracket" is MT95.

Okay, I had a chance to tow my RV again this past weekend, and I decided to adjust the timing again. After moving the timing from 2.5 ATDC to 4.5 ATDC, my boost dropped slightly and my EGT's went up. The EGT's went up enough that I had to keep a constant eye on the guage, to keep from going over 1100*. Before we left the campground to come home, I advanced the timing just a smidgeon. Now it's sitting at the sweet spot. Boost came back up, EGT's won't go over 1100*, right where I want it.

I just checked the timing again to see where it's at...looks like 4.0 ATDC. 4.0 to 4.5 doesn't seem like much, but it makes enough difference that I can see it on the guages.

Final conclusions: Any more advanced than 3.0 ATDC, and it starts to rattle too much, and is very, very noisy at startup, plus the power doesn't seem to increase. I'd say the perfect range for a 6.2L TURBO would be 3.5 to 4.0 degrees ATDC (-4.0), when using a Snap-On MT1480A timing meter.

Casey

[Dieselboy]

What RPM are you testing at, Casey?

[arveetek]

Sorry, I should have mentioned that. My readings are being taken at 1400 RPM.

Casey

[opto]

Any idea where to get these meters for a reasonable price?

[Dieselboy]

Originally posted by opto:
Any idea where to get these meters for a reasonable price? I got my MT480 off ebay. The lumy probes are still supported by Snap On, so you can get one through your dealer. For how long though?

[Dominique]

what is an easy way to keep the RPM's at 1400? I tried turning the Idle screw all the way in but it won't go far enough. Are their any tricks?

thanks
Dominique

[Dieselboy]

I have found the best way to hold the throttle steady was to have somebody sit in the truck and do it.

[arveetek]

I put a small block, about 1/2" thick, between the throttle lever and the fast idle solenoid. Then you can use the adjustment screw on the fast idle to fine-tune the engine speed to keep it at 1400 rpm. The instructions that came with the Snap-On meter say to keep the engine at the desired speed for several minutes, to make sure the readings are accurate and stable. It's hard to keep the engine speed stable by hand or foot.

Casey

[doncannon]

hello all,
I just got the snap on mt480. how do you hook it up?
thank you in advance,
Don

[Dieselboy]

The manual explains it well. I've scanned mine into pdf format:
http://www.oliverdiesel.com/images/mt480/manual/

[doncannon]

thank you dieselboy!
don