Timing, SVDA and Advance Curves.
- Sluggo
- Wishin' I was Fishin'
- Location: Portland, Or.
- Contact:
- Status: Offline
Timing, SVDA and Advance Curves.
My timing advances too much. I have the Aircooled.net SVDA. From what I understand it should be timed at 28* max advance with the vac hose off and plugged. Mine does go to 28* max centrifugal advance and settles nicely at 7.5* BTDC at idle. But once I hook up the vac hose the timing advances to 34* Max advance! This is too high right? How do I adjust the dizzy springs/weights to make so that I only have 28* advance.
I was reading this thread at Shoptalk http://www.shoptalkforums.com/viewtopic ... ry&start=0
Now I'm a little more confused.
I was reading this thread at Shoptalk http://www.shoptalkforums.com/viewtopic ... ry&start=0
Now I'm a little more confused.
1977 Bus with Sunroof - "Lucky '77"
2000cc Type IV w/Dual Weber 36s,
Aircooled.net SVDA w/Compufire,
Redline Weber Fuel Pump,
Holley Regulator,
Half Ass Brush & Roller Rustoleum Paint Job,
Incomplete Custom Interior,
Dual Batteries,
Crunched Slider Door.
------------------------------------------------------
- spiffy
- IAC Addict!
- Location: Walla Walla, WA
- Status: Offline
- Sluggo
- Wishin' I was Fishin'
- Location: Portland, Or.
- Contact:
- Status: Offline
Thanks guys. I was thinking it should go up and then return to 28*. Then return to 7.5* BTDC at idle. I won't worry about it. Bus is running better and stronger than ever.
1977 Bus with Sunroof - "Lucky '77"
2000cc Type IV w/Dual Weber 36s,
Aircooled.net SVDA w/Compufire,
Redline Weber Fuel Pump,
Holley Regulator,
Half Ass Brush & Roller Rustoleum Paint Job,
Incomplete Custom Interior,
Dual Batteries,
Crunched Slider Door.
------------------------------------------------------
- Amskeptic
- IAC "Help Desk"
- Status: Offline
Vacuum advance should hit 40*BTDC when you mildly blip throttle up to 3,000 rpm or so. On the road, when you floor the accelerator, the vacuum drops under full load, then the centrifugal advance is your primary advance. The Type 4 engines are pretty happy up to 30-32* BTDC on centrifugal only. Check at 3,200 rpm with advance hose off, duh course. When you are done, make sure centrifugal advance does NOT exceed your adjusted value when you rev to 4,000 rpm briefly.Sluggo wrote:Thanks guys. I was thinking it should go up and then return to 28*. Then return to 7.5* BTDC at idle. I won't worry about it. Bus is running better and stronger than ever.
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
- Gypsie
- rusty aircooled mekanich
- Location: Treadin' Lightly under the Clear Blue!
- Status: Offline
What if it does advance beyond the adjusted value?Amskeptic wrote: The Type 4 engines are pretty happy up to 30-32* BTDC on centrifugal only. Check at 3,200 rpm with advance hose off, duh course. When you are done, make sure centrifugal advance does NOT exceed your adjusted value when you rev to 4,000 rpm briefly.
Colin
Would that mean that it is not fully advanced at 3200rpm?
If so should the high rpm advanced setting get made with a higher rpm to attain max centrifugal advance for the setting?
Curiouser and curiouser...
So it all started when I wanted to get better gas mileage....
- Amskeptic
- IAC "Help Desk"
- Status: Offline
If it does advance beyond the specification, then the second question is answered by the first. You would want to clean the centrifugal weights and pivots and springs. You need to be dialed-in advance-is-in, at 3,200 rpm. Your immediate concern is to make sure that the timing never exceeds 28-30* at any rpm, and if you need to retard the timing, do it, even if the idle timing is now closer to "0". Idle is not half so critical.Gypsie wrote:What if it does advance beyond the adjusted value?Amskeptic wrote: The Type 4 engines are pretty happy up to 30-32* BTDC on centrifugal only. Check at 3,200 rpm with advance hose off, duh course. When you are done, make sure centrifugal advance does NOT exceed your adjusted value when you rev to 4,000 rpm briefly.
Colin
Would that mean that it is not fully advanced at 3200rpm?
If so should the high rpm advanced setting get made with a higher rpm to attain max centrifugal advance for the setting?
Colin
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles
- tvargs
- I'm New!
- Location: San Francisco, CA
- Contact:
- Status: Offline
Re: Timing, SVDA and Advance Curves.
I just had a new (rebuilt) engine from Adrian @ Headflow Masters put into my '77 FI Type 2, stock most everything. There's a long story about it, featuring the amazing, truly exemplary, and unbelievable effort and service of Adrian Audirac and Kenny from Headflow Masters, but I will save that for another thread. Suffice it to say: those guys are worth EVERY PENNY and have gone ABOVE AND BEYOND what a reasonable person would ever expect - I can't thank them enough. =D>
So when we got the engine running, Adrian noticed that the timing went to 40* at 3000RPM, and pronounced that way too high. Without the hose, it stays below 30*. One thing we noticed when we took a look at the distributor is it's a fair bit dirty - my first thought was perhaps a good cleaning will help.
Reading the above post, though, suggests that the high advance shouldn't be too much of a concern. Without the hose, the advance stays below 30*, with the hose attached, it gets way up there. Any thoughts?
So when we got the engine running, Adrian noticed that the timing went to 40* at 3000RPM, and pronounced that way too high. Without the hose, it stays below 30*. One thing we noticed when we took a look at the distributor is it's a fair bit dirty - my first thought was perhaps a good cleaning will help.
Reading the above post, though, suggests that the high advance shouldn't be too much of a concern. Without the hose, the advance stays below 30*, with the hose attached, it gets way up there. Any thoughts?
1977 2.0 FI Westy
- Randy in Maine
- IAC Addict!
- Location: Old Orchard Beach, Maine
- Status: Offline
- tvargs
- I'm New!
- Location: San Francisco, CA
- Contact:
- Status: Offline
Re: Timing, SVDA and Advance Curves.
Ok, so that graph tells me that the timing goes far too high at 3000 RPM, and I have a problem? And that problem is likely the distributor? (It was suggested that my dizzy may be missing a spring - will have to take it apart to see. Seems like an odd thing, to have a missing spring, but you could fill entire libraries with what I think is odd and don't have the experience to know...)
1977 2.0 FI Westy
- chitwnvw
- Resident Troublemaker
- Location: Chicago.
- Status: Offline
Re: Timing, SVDA and Advance Curves.
IIRC, it is 28 degrees without vacuum max advance. With vac if you blip the rpms you can see 40 + degrees of advance briefly, picture you need a bit of acceleration to pass a car on the highway, so you lay on the gas pedal...
But it should pretty quickly settle back to the 30 degree territory...
But it should pretty quickly settle back to the 30 degree territory...
- RSorak 71Westy
- IAC Addict!
- Location: Memphis, TN
- Contact:
- Status: Offline
Re: Timing, SVDA and Advance Curves.
This is flat out wrong. When you get on the throttle the engine vacuum goes down not up. So the timing would not advance under these conditions.With vac if you blip the rpms you can see 40 + degrees of advance briefly.
If you were missing a spring the timing would come in sooner i.e. lower RPM but it would not go any higher than it otherwise could.
Take care,
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.
Rick
Stock 1600 w/dual Solex 34's and header. mildly ported heads and EMPI elephant's feet. SVDA W/pertronix. 73 Thing has been sold. BTW I am a pro wrench have been fixing cars for living for over 30 yrs.